CN115976422A

CN115976422A - Flexible second phase production control method suitable for bearing steel and application thereof

Info

Publication number: CN115976422A
Application number: CN202310274167.6A
Authority: CN
Inventors: 王伟; 杨兆全; 蔡鹏�; 吴化鑫
Original assignee: Jiangsu Yonggang Group Co Ltd
Current assignee: Jiangsu Yonggang Group Co Ltd
Priority date: 2023-03-21
Filing date: 2023-03-21
Publication date: 2023-04-18
Also published as: CN116574976A

Abstract

The invention discloses a production control method of a flexible second phase suitable for bearing steel and application thereof, belonging to the technical field of metal product production. The control method comprises component control, smelting control, high-temperature diffusion and cogging control, hot-rolled blank heating control and wire rolling control. According to the invention, by controlling the production process parameters of the bearing steel, good shapes, sizes and quantities of inclusions and carbides are obtained, so that the product can meet the requirements of downstream users on stably and efficiently producing the rolling element with long fatigue life. Obtaining the proper quantity and type of the inclusions through a proper metallurgical process; the properties and the forms of inclusions are changed through intermediate cogging and diffusion processes; and by controlling the rolling process parameters, the composite precipitation of inclusions and carbides is inhibited, and finally good product quality is obtained.

Description

Flexible second phase production control method suitable for bearing steel and application thereof

Technical Field

The invention relates to a production control method of a flexible second phase suitable for bearing steel and application thereof, belonging to the technical field of metal product production.

Background

The high-quality bearing steel is mainly used for manufacturing rolling elements such as precision steel balls, and the like, wherein the parameters such as the quantity, the form, the size and the like of hard second phases such as inclusions, carbides and the like obviously influence the performances such as the fatigue life, the crushing load, the corrosion resistance and the like of the rolling elements. A large number of researchers have studied the relationship between oxide inclusions, carbide particles and rolling element fatigue life. The current bearing steel manufacturing enterprise adopts suitable smelting equipment and continuous casting process, can stably reduce the oxygen content in the bearing steel to below 8ppm, makes oxide inclusion quantity in the steel greatly reduce, and through suitable high temperature diffusion processing, makes the rolling element life-span improve by a wide margin. On the other hand, in the case of bearing steel produced by the electroslag remelting method, although the oxygen content reaches 18ppm, the fatigue life of the rolling element produced is longBearing steel L still having an oxygen content of 8ppm produced by continuous casting ₁₀ 1.4 times of life, L ₅₀ 1.3 times the life, which shows that the size and morphology of the hard second phase is also critical for the fatigue life of the bearing steel, in addition to the effect of the oxygen content. The reduction of the fatigue life of hard secondary phases such as TiN particles, eutectic carbide particles and the like has received much attention and research. The harm of the hard second phase to steel is essentially that the elastic modulus, the linear expansion coefficient and the plasticity of the hard second phase particles and a steel matrix are different, and the hard second phase particles and the matrix are not coordinated and synchronous when stressed and deformed, so that cracks and cavities are generated at the junction, and finally early crack source initiation and fatigue failure are caused.

Therefore, in the production process of the bearing steel, a special control means is needed to optimize the hard second phase, a desired inclusion morphology and carbide state are obtained through a flexible control method, the harm of the hard second phase to the bearing steel is reduced, and the product quality is improved.

Disclosure of Invention

The invention aims to provide a flexible second phase production control method suitable for bearing steel, which obtains good shapes, sizes and quantities of inclusions and carbides by controlling production process parameters of the bearing steel, so that a product can meet the requirements of downstream users on stable and efficient production of rolling elements with high fatigue life. Obtaining the proper quantity and type of the inclusions through a proper metallurgical process; the properties and the forms of the inclusions are changed through intermediate cogging and diffusion processes; and by controlling the rolling process parameters, the composite precipitation of inclusions and carbides is inhibited, and finally good product quality is obtained.

Meanwhile, the invention provides application of the wire rod obtained by the flexible second phase production control method suitable for bearing steel in the rolling body.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a flexible second phase production control method suitable for bearing steel comprises the following steps:

1) Controlling components:

the weight percentage of the chemical components of the bearing steel is C:0.95-1.05%, mn:0.25 to 0.45%, si:0.15 to 0.35%, S:0.01 to 0.025%, P: less than or equal to 0.025 percent, ti: less than or equal to 0.002%, ni: less than or equal to 0.30%, mo: less than or equal to 0.10 percent, cu: less than or equal to 0.25 percent, and the balance of Fe and trace impurities.

For controlling the S content, when the S content is too low, the sulfide does not form a form with an oxide and a nitride as cores, and only independent sulfide is formed. When the S content is too high, the formed sulfide is too high in grade, the fatigue performance is deteriorated, and meanwhile, the sulfide and carbon element perform eutectic reaction at the interdendritic positions, so that large-size eutectic carbide is formed, and the fatigue performance is also deteriorated.

The excessive high sulfide grade means that the number of sulfides is large and the size is large, and the detected sulfide inclusion grade is high according to the method of GB/T10561 steel non-metallurgical inclusion content determination.

The control of the Ti content is mainly to avoid the formation of large-particle titanium inclusions.

2) Smelting control:

tapping and alloying through a proper converter (firstly, the molten iron which is required to be loaded into the converter is that the C content is 3.7-4.5%, the Si content is 0.2-0.5%, the Mn content is 0.2-0.3%, the lower the other elements are, the better the molten iron is, after the molten iron enters the converter, blowing the molten iron for 700-1000 seconds by using an oxygen lance, controlling the carbon-drawing temperature to be 1560-1670 ℃, and adding proper lime, fluorite, dolomite, iron oxide skin balls and the like in the smelting process of the converter to ensure that the slag components of the converter are 45-55% CaO, siO, and the like ₂ :10-15%, mgO:5-8% and the balance FeO. Alloying is carried out during tapping, the slag discharging amount is noticed to be lower than 3Kg/t, and 80-120Kg of Al block is added when the amount of molten steel in a ladle is about 4-6 t; when the amount of molten steel in the ladle is about 8-12t, a carburant (the component of the carburant is C), ferrosilicon, ferromanganese, ferrochrome and synthetic slag (the synthetic slag mainly comprises 48-50% of CaO and 34-35% of Al in sequence ₂ O ₃ 、14~15%SiO ₂ And the balance of MgO) so that the molten steel components are as follows) to obtain molten steel with the following components and temperatures, and the molten steel is used as a previous guarantee for LF refining treatment.

Molten steel components: c:0.89-0.95%, si:0.10 to 0.15%, mn:0.27-0.32%, P:0.0087-0.0109%, S:0.005-0.01%, al:0.0086-0.0559%, ti:0.0007-0.0074%, cr:1.33-1.43 percent, and the balance of Fe and trace impurities.

The molten steel temperature is as follows: 1505-1570 ℃. The LF refining procedure is carried out by a suitable slagging process (starting from LF refining, adding 500Kg of synthetic slag (the synthetic slag mainly comprises 48 to 50% of CaO, 34 to 35% of Al) ₂ O ₃ 、14~15%SiO ₂ And the balance of MgO), 100Kg of lime, 50Kg of calcium carbide and 100Kg of ferrosilicon powder, then fine adjustment is carried out by observing the color, the consistency and the like of the slag material on site, and finally good white slag) is obtained, namely the final slag, wherein the components of the final slag are as follows: caO:40-57.2% of SiO ₂ ：15-25%，MgO：6-10%，Al ₂ O ₃ :21-25% and FeO:0.8 to 1.2 percent. The alkalinity R of the final slag is 3-4.5. In the LF refining process, according to the component inspection condition of molten steel, properly adding alloys such as carbon wires, ferromanganese, ferrochromium and the like for component fine adjustment, avoiding adopting alloys with high Ti content, and ensuring that C in the molten steel obtained by LF refining is as follows: 0.89-0.95%, si:0.10 to 0.15%, mn:0.27-0.32%, P:0.0087-0.0109%, S:0.005-0.01%, al:0.0086-0.0559%, ti:0.0007-0.0074%, cr:1.33-1.43 percent, and the balance of Fe and trace impurities.

And after LF refining, the molten steel enters an RH station to be continuously refined, the RH vacuum treatment cycle time is 40-50min, the vacuum degree is 50-100Pa, and inclusions in the molten steel are further removed and degassing is further carried out.

Calcium treatment is strictly forbidden in the whole smelting process, namely no calcium wire is added into molten steel in the LF refining process.

After the steel ladle after the RH vacuum treatment is put into a continuous casting machine and is produced at a drawing speed of 0.65-0.8m/min, the temperature of a tundish is controlled to be 1475-1500 ℃, protective slag is added into a crystallizer, the crystallizer is electromagnetically stirred, the current is set to be 480-520A, the frequency is 2.35-2.45Hz, the total water quantity of secondary cooling water is controlled to be 100-130L/min, and the total pressure reduction quantity is controlled to be 8.5-11mm under dynamic soft reduction at the tail end, the second phase in the continuous casting billet has the following types: 1) Inclusions are classified into the following categories: (1) ti (C, N) inclusions with edges are orange red, a small amount of Ti inclusions appear singly, and most of Ti inclusions appear along with MnS; ti (C, N) is TiA, wherein A comprises C and/or N. (2) MnS inclusions, which are mainly present in 2 forms: pure MnS in bulk, mnS with other inclusions (mostly oxides) as cores. (3) The oxide inclusions mainly comprise 2 types of small-amount magnesium aluminate spinel inclusions and large-amount aluminum oxide + calcium aluminate + sulfide composite inclusions. 2) Carbides, which fall into the following categories: (1) particulate eutectic carbides between dendrites. (2) Coarse along-the-grain network carbides.

The casting powder is continuously consumed along with the continuous casting of the steel billet, so the casting powder is continuously added according to the actual consumption condition on site, the molten steel is kept not to be exposed, and the general consumption is 0.2 to 1.0Kg/t (0.2 to 1.0Kg of casting powder is consumed by each ton of molten steel). The crystallizer casting powder mainly comprises the following components: 35% of SiO ₂ ，22%CaO，4%Al ₂ O ₃ ，10%K ₂ O+Na ₂ O（K ₂ O and Na ₂ O is an arbitrary ratio), 19% by weight of C, and the balance of Fe.

3) High-temperature diffusion and cogging:

the continuous casting billet is subjected to slow cooling or direct hot charging for high-temperature diffusion, and the temperature of each section is controlled as follows:

a preheating section: the temperature is less than or equal to 900 ℃, and the time is more than or equal to 180min;

a heating section: the temperature is 1200-1250 ℃, and the time is 100-120min;

a soaking section: the temperature is 1250-1270 ℃, and the time is 60-90min.

The main function of high-temperature diffusion is to dissolve carbide, and the sufficient high-temperature diffusion temperature and time are used for ensuring the dissolution of the carbide second-phase particles and reducing the influence of the carbide second-phase particles on the fatigue life. After high-temperature diffusion (the high-temperature diffusion is finished in a furnace, after the diffusion is finished, the steel blank directly enters a cogging mill through a roller way to perform 6 times of heavy reduction, the temperature of the steel blank is 1180-1230 ℃ during cogging, the temperature of the steel blank is gradually reduced along with the cogging, and the temperature of the steel blank is 1060-1100 ℃ after the cogging is finished), and the hot rolling blank with the section of 160 multiplied by 160mm is rolled by adopting 6 times of heavy reduction. In order to ensure the reduction effect of the central area of the billet, the reduction process of each pass is as follows:

pass 1: notch width B:320mm; groove bottom width b:285mm; height h:160mm;

pass 2: notch width B:256mm; groove bottom width b:220mm; height h:160mm;

pass 3: notch width B:226mm; groove bottom width b:190mm; height h:160mm;

pass 4: notch width B:201mm; groove bottom width b:170mm; height h:160mm;

pass 5: notch width B:175mm; groove bottom width b:155mm; height h:160mm;

pass 6: notch width B:162mm; groove bottom width b:157mm; height h:160mm.

After the hot rolling billet is rolled by the high-temperature diffusion treatment, the second phase in the billet is of the following type: 1) Inclusions are classified into the following categories: (1) ti (C, N) -based inclusions, a few of which are singly precipitated as massive Ti (C, N) inclusions, are basically crushed, and most of Ti (C, N) inclusions occurring together with MnS are not deformed. (2) The MnS inclusions and the MnS inclusions are elongated, and part of MnS is accompanied by oxides and Ti (C, N) inclusions. (3) The oxide inclusions are mainly of 2 types of magnesium aluminate spinel, alumina, calcium aluminate and sulfide composite, and are mostly wrapped by MnS inclusions. 2) Carbide: (1) the granular eutectic carbides among dendrites have been completely dissolved into the matrix. (2) The net-shaped carbide is precipitated at the position of the grain boundary, and the thickness is less than 0.5 mu m.

4) Heating a hot-rolled blank:

the hot rolling billet is heated and then rolled, and the temperature of each section is controlled as follows when the hot rolling billet is heated:

a preheating section: the temperature is less than or equal to 800 ℃, and the time is 60-70min;

a heating section: the temperature is 1150-1210 ℃, and the time is 30-40min;

a soaking section: the temperature is 1190-1230 ℃, and the time is 30-40min.

Various second phase particles in the hot rolling blank are heated and insulated again after being cooled, and can change again, which is mainly shown in the following steps: (1) the quantity of small particles Ti (C, N) in the matrix is increased, and the matrix cavity caused by the crushing of Ti (C, N) in the cogging process is closed after being heated at high temperature and rolled again. Ti (C, N) accompanied with MnS is further wrapped by MnS, so that the harm degree is reduced. (2) Strip-shaped MnS in the hot-rolled billet can be broken at a weak position and tends to be spherical after being heated and insulated, and finally becomes isolated MnS particles. MnS with oxide inclusions as a core tends to become spherical shells, and the Ca content of the shells further increases, eventually becoming CaS-MnS complex inclusions. (3) After the hot-rolled blank is heated and insulated, almost all oxide inclusions appear along with MnS. Most of the oxide inclusions are small and are wrapped by MnS inclusions; a small amount of oxide inclusions are large and account for part of MnS.

Through the treatment, the carbide second phase particles in the hot rolling blank are almost completely dissolved in the solution, and most of the inclusion second phase particles are wrapped by sulfide, so that the damage of the hard second phase to the fatigue life is obviously reduced. The pure brittle second phase particles and the second phase particles wrapped by sulfide are rolled into wire rods, and then the wire rods are manufactured into the rolling bodies through drawing and cold heading processes. Therefore, after the wire rod is wrapped by the sulfide, the damage of the second phase particles to the matrix in the deformation process of the wire rod can be obviously reduced.

5) Rolling the wire rod:

the control key points of wire rod rolling are as follows: 1) The finish rolling temperature is 850-880 ℃, the reducing sizing temperature is 850-880 ℃, the spinning temperature is 780-810 ℃, and each section of water tank passes through a proper nozzle and a recovery section to reach the temperature range. At least 2 sections of water tanks are required to penetrate before finish rolling, the number of nozzles of each water tank is more than or equal to 10, and the length of a water cooling section before the whole finish rolling is more than or equal to 40m; at least 3 sections of water tank penetrating are arranged between the finish rolling and the reducing diameter, the number of nozzles of each water tank is more than or equal to 10, and the length of a water cooling section before the whole finish rolling is more than or equal to 50m; at least 2 sections of water tank penetrating are arranged between the reducing diameter and the spinning machine, the number of nozzles of each water tank is more than or equal to 10, and the length of the water cooling section before the whole finish rolling is more than or equal to 20m. When in production, the cooling water temperature is required to be less than or equal to 35 ℃, the pressure of the cooling nozzle is required to be more than or equal to 0.5MPa, the back blowing nozzle is completely opened, and the pressure is required to be more than or equal to 0.5MPa. The cooling nozzles control the water flow rate in accordance with the actual temperature, and it is required to preferentially open the nozzles near the heating furnace, and to close the nozzles near the laying head, or to adopt a small flow rate.

The main purpose of wire rolling is to deform the core of the rolled material at a low temperature, and the core of the rolled material is cooled by a proper water tank nozzle and sufficiently recovered to keep the temperature of the core of the rolled material at a low temperature all the time, so as to avoid the precipitation of coarse carbide second phases. Meanwhile, the lower deformation temperature enhances the strength of the steel matrix and further reduces the harm of the second phase of the hard inclusion. At the moment, most hard inclusions are wrapped by sulfides, and can be deformed in cooperation with the matrix in the deformation process, so that the harmfulness of pore formation is reduced sharply.

In the wire, the ratio of the number of oxide and sulfide associated second phase particles to the total number of pure oxide particles and Ti (C, N) particles is (1.52-2.09): 1.

the application of the wire rod obtained by the flexible second phase production control method suitable for bearing steel in the rolling body is characterized in that the wire rod is manufactured into the rolling body through the processes of drawing and cold heading.

A rolling element is made of the wire rod obtained by the flexible second phase production control method suitable for bearing steel.

The smelting control of the invention is as follows: the desired second phase type is obtained by suitable converter tapping, LF slagging, RH and continuous casting processes. High-temperature diffusion and cogging: the carbide second phase is dissolved by a suitable high temperature diffusion process, reducing its impact on fatigue life. After high temperature diffusion, the hot rolled blank is rolled into a section of 160 x 160mm by 6 times to obtain the expected second phase type of the inclusion. A hot-rolled blank heating process: through the hot rolling billet heating process, the carbide second phase particles in the hot rolling billet are almost completely dissolved in the solution, most of the inclusion second phase particles are wrapped by sulfide, and the harm of the hard second phase to the fatigue life is obviously reduced. Controlling wire rod rolling: the deformation of the core of the rolled material in a low-temperature state is controlled, so that coarse carbide second phases are prevented from being precipitated. Meanwhile, the lower deformation temperature enhances the strength of the steel matrix and further reduces the harm of the second phase of the hard inclusion. At the moment, most hard inclusions are wrapped by sulfides, and can deform synchronously with the matrix structure in the deformation process.

Compared with the bearing steel wire rod obtained by the conventional control method, the invention has the following beneficial effects: through flexible control, the probability of scratching the matrix by a hard second phase is reduced, a low-harm matrix tissue is obtained, a rolling contact fatigue life test is carried out after the rolling element is manufactured, and under the maximum contact stress of 4.5GPa, L is ₁₀ The service life reaches 1.5 multiplied by 10 ⁷ Circulating for a week.

Drawings

FIG. 1 is a view showing a microstructure in which Ti (C, N) grains associated with MnS are further wrapped with MnS when a hot-rolled slab of the present invention is heated;

FIG. 2 is a microstructure view of elongated MnS in a hot rolled billet according to the present invention;

FIG. 3 is a microstructure diagram of elongated MnS in FIG. 2 which is heated to finally become CaS-MnS composite inclusion particles;

FIG. 4 is a microstructure view of a sulfide encapsulated oxide particle of the present invention;

FIG. 5 is a microstructure of a particle of the present invention in oxide to sulfide ratios;

FIG. 6 is a morphology of a wire cold heading deformed second phase without sulfide wrapping;

FIG. 7 is a morphology of a sulfide coated, cold heading deformed second phase of a wire rod according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following drawings and specific examples. The following examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.

Example 1

A production control method of a flexible second phase suitable for bearing steel, which has a specification of phi 10mm, comprises component control, smelting control, high-temperature diffusion and cogging control, hot rolled billet heating control and wire rod rolling control, and comprises the following production steps:

1) Controlling components: the bearing steel comprises the following chemical components in percentage by weight: 1.0%, mn:0.35%, si:0.25%, S:0.015%, P:0.012%, ti:0.002%, ni:0.02%, mo:0.01%, cu:0.02 percent, and the balance of Fe and trace impurities.

2) Smelting control: LF final slag composition: caO:46% of SiO ₂ ：21%，MgO：10%，Al ₂ O ₃ :22%, feO:1.0 percent. RH vacuum treatment time 45min, vacuum degree 67Pa.

The molten steel components are enabled to meet the following contents through proper converter tapping and alloying, and the molten steel with the following components and temperatures is obtained and used as an early guarantee of LF refining treatment.

Converter outletThe steel and alloying process comprises the following steps: the molten iron loaded into the converter requires that the content of C is 4.0 percent, the content of Si is 0.4 percent, the content of Mn is 0.25 percent, and the rest elements do not need to be added; blowing molten iron into a converter for 850 seconds by using an oxygen lance, and controlling the carbon drawing temperature to be 1600 ℃; in the smelting process of the converter, one or more of lime, fluorite, dolomite and iron oxide ball are added to ensure the components of the converter slag: caO:50% of SiO ₂ :12%, mgO:6% and the balance FeO; alloying during tapping and paying attention to the slag amount less than 3Kg/t, and adding 100Kg of Al blocks when the molten steel amount in the ladle is 5 t; when the molten steel amount in the ladle is 10t, the carburant, ferrosilicon, ferromanganese, ferrochromium and synthetic slag are added in sequence, so that the components of the molten steel meet the requirements. The synthetic slag comprises 49% of CaO and 35% of Al ₂ O ₃ 、15%SiO ₂ And the balance MgO. The carburant is C.

Molten steel components: c:0.90%, si:0.12%, mn:0.30%, P:0.0095%, S:0.008%, al:0.023%, ti:0.005%, cr:1.40 percent, and the balance of Fe and trace impurities; the molten steel temperature is as follows: 1550 ℃. The LF refining is carried out through a slagging process (the slagging process is that 500Kg of synthetic slag, 100Kg of lime, 50Kg of calcium carbide and 100Kg of ferrosilicon powder are added when the LF refining is started, and then fine adjustment is carried out by observing the color and the consistency of slag materials on site to finally obtain white slag, namely final slag), so as to obtain the final slag, wherein the components of the final slag are as follows: caO:44% of SiO ₂ ：20%，MgO：10%，Al ₂ O ₃ :25% and FeO:1 percent; the alkalinity R of the final slag is 3.5; in the LF refining process, according to the component inspection condition of the molten steel, adding a carbon wire, ferromanganese and ferrochrome for component fine adjustment, and ensuring that the molten steel obtained by LF refining has the same components as the molten steel obtained after converter tapping and alloying;

the RH vacuum treated ladle was put into a continuous casting machine and produced at a drawing speed of 0.7m/min with the tundish temperature controlled at 1490 ℃ and the mold flux (mold flux consumption: 0.5Kg mold flux per ton of molten steel; mold flux composition including 35% SiO 2) was added into the mold ₂ ，22%CaO，4%Al ₂ O ₃ ，10%K ₂ O+Na ₂ O, 19%; the crystallizer adopts electromagnetic stirring, the current is set to be 500A, and the frequency is 2.4Hz; for the secondary cooling water, the total water content is controlled at 120L/min, andthe tail end adopts dynamic soft reduction, and the total reduction is controlled to be 10mm to obtain a continuous casting billet;

the second phase in the slab is of the following type: 1) Inclusions are classified into the following categories: (1) ti (C, N) inclusions appear as orange red with edges, and appear in small amounts alone, and most of them appear together with MnS. (2) MnS inclusions, which are mainly present in 2 forms: pure MnS in bulk, mnS with other inclusions (mostly oxides) as cores. (3) The oxide inclusions mainly comprise 2 types of small-amount magnesium aluminate spinel inclusions and large-amount aluminum oxide + calcium aluminate + sulfide composite inclusions. 2) Carbides, which fall into the following categories: (1) particulate eutectic carbides between dendrites. (2) Coarse along-grain network carbides.

3) High-temperature diffusion and cogging: the temperature of the preheating section is 850 ℃, and the temperature is kept for 180min; the temperature of the heating section is 1230 ℃, and the temperature is kept for 120min; the temperature of the soaking section is 1260 ℃, and the temperature is kept for 70min. And 6 times of cogging and rolling to obtain hot rolling billets with 160mm sections.

After the high-temperature diffusion is finished, directly entering a cogging mill through a roller way to perform 6 times of large reduction, wherein the temperature of a steel billet during cogging is 1200 ℃; with the process of cogging, the temperature of the steel billet is gradually reduced, the temperature of the steel billet is 1080 ℃ after the cogging is finished, and the steel billet is rolled into a hot rolling billet with a section of 160mm by adopting 6 times of high reduction;

the reduction process of each pass under 6 passes of large reduction is as follows:

pass 1: notch width B:320mm; groove bottom width b:285mm; height h:160mm;

pass 2: notch width B:256mm; groove bottom width b:220mm; height h:160mm;

pass 3: notch width B:226mm; groove bottom width b:190mm; height h:160mm;

pass 4: notch width B:201mm; groove bottom width b:170mm; height h:160mm;

pass 5: notch width B:175mm; groove bottom width b:155mm; height h:160mm;

pass 6: notch width B:162mm; groove bottom width b:157mm; height h:160mm.

After the hot rolled billet is processed by the high-temperature diffusion treatment and rolled, the second phase in the billet is of the following type: 1) Inclusions are classified into the following categories: (1) ti (C, N) -based inclusions, a few of which are individually precipitated as bulk Ti (C, N) inclusions, are substantially crushed, and most of Ti (C, N) inclusions occurring with MnS are not deformed. (2) The MnS inclusions are elongated, and some MnS are accompanied by oxide and Ti (C, N) inclusions. (3) The oxide inclusions are mainly of 2 types of magnesium aluminate spinel, alumina, calcium aluminate and sulfide composite, and are mostly wrapped by MnS inclusions. 2) Carbide: (1) the granular eutectic carbides among dendrites have been completely dissolved into the matrix. (2) The net carbide is precipitated at the position of the grain boundary, and the thickness is less than 0.5 mu m.

4) Heating a hot-rolled blank: the temperature of the preheating section is 750 ℃, and the temperature is kept for 60min; the temperature of the heating section is 1190 ℃, and the temperature is kept for 40min; the temperature of the soaking section is 1220 ℃, and the temperature is kept for 30min.

Various second phase particles in the hot rolling blank are heated and insulated again after being cooled, and can change again, which is mainly shown in the following steps: (1) the quantity of small particles Ti (C, N) in the matrix is increased, and matrix cavities caused by the crushing of Ti (C, N) in cogging are closed after being heated at high temperature and rolled again. Ti (C, N) associated with MnS is further wrapped by MnS, reducing the hazard level thereof, as shown in FIG. 1. (2) Strip MnS in the hot-rolled billet can be broken at a weak position and tends to be spherical after being heated and insulated, and finally becomes isolated MnS particles. The MnS with the oxide inclusions as the core tends to become a spherical shell, and the Ca content of the shell further increases, finally becoming CaS-MnS composite inclusions, as shown in fig. 2 to 3. (3) After the hot-rolled blank is heated and insulated, almost all oxide inclusions appear along with MnS. Most of the oxide inclusions are small and are wrapped by MnS inclusions; the small amount of oxide inclusions is large and is partially proportional to MnS, as shown in FIGS. 4 to 5. Oxides and MnS dimensions and proportions were counted using a FEI inclusion scanning analyzer, as shown in table 1 below.

TABLE 1 scanning analysis results

As can be seen from table 1, the higher the number of particles in which the oxide is coated with the sulfide, the better. For the fatigue life hazard, the total amount of the second phase is determined, the pure sulfide second phase < the second phase particles of which oxides are wrapped by sulfides < the second phase particles of which oxides and sulfides respectively account for the proportion < the pure oxides, ti (C, N) and carbides second phase. As 2335 inclusions (carbide second phase has been almost completely eliminated) were scanned in this test, the number of oxide and sulfide associated particles was 1124, the number of pure oxide particles and Ti (C, N) particles was 387 and 151, respectively, and the ratio of the number of oxide and sulfide associated particles to the total number of pure oxide particles and Ti (C, N) particles was 1124/538=2.09. The invention reduces the quantity of the hard second phase of the pure oxide particles and the Ti (C, N) particles, and the ratio of the quantity of the associated particles of the oxide and the sulfide to the total quantity of the pure oxide particles and the Ti (C, N) particles is more than or equal to 1.5, thus obtaining good fatigue life. In comparative example 1, most of the oxides and Ti (C, N) were not associated with the sulfides, resulting in a reduction in fatigue life.

5) Rolling the wire rods: feeding the mixture into a finishing mill at 850 ℃, reducing and sizing the mixture at 880 ℃, and spinning the mixture at 790 ℃. Opening the water tanks of the 1 st and 2 nd sections before finish rolling, the water tanks of the 1 st, 2 nd and 3 rd sections between finish rolling and reducing diameter, and the water tanks of the 1 st and 2 nd sections before the reducing diameter and the laying head. All water tanks are provided with front 5 nozzles, the cooling water temperature is 30 ℃, the nozzle pressure is 0.6MPa, all back-blowing nozzles are opened, and the gas pressure is 0.6MPa.

In the embodiment, the finish rolling temperature of the wire rod reaches 850 ℃, the diameter reducing temperature reaches 880 ℃ and the spinning temperature reaches 790 ℃ by controlling the nozzles and the recovery section of each section of water tank.

Through the treatment, the carbide second phase particles in the hot rolling blank are almost completely dissolved in the solution, and most of the inclusion second phase particles are wrapped by sulfide, so that the damage of the hard second phase to the fatigue life is obviously reduced. And after the pure brittle second phase particles and the second phase particles wrapped by the sulfide are rolled into a wire, the wire is manufactured into a rolling body through the processes of drawing and cold heading, and the appearance is shown in figures 6-7. Therefore, after the wire is wrapped by the sulfide, the damage of the second phase particles to the matrix in the deformation process of the wire can be obviously reduced.

In fig. 6, the hard oxide particles are not coated by sulfide, and in cold heading deformation and drawing deformation of steel, the oxide particles are broken into strings, scratch the matrix and form holes, which are sources of early fatigue failure and reduce the fatigue life of the material. In fig. 7, the hard oxide particles are wrapped by sulfides, and in the deformation of the steel, the sulfides protect the oxide particles from being broken, so that the damage to the steel matrix is small, and the fatigue life is prolonged.

The wire is made into the rolling body through the processes of drawing and cold heading.

A rolling element made of a wire rod obtained by a flexible second phase production control method suitable for bearing steel of the present embodiment.

Example 2

A flexible second phase production control method suitable for bearing steel, with the specification of phi 12mm, comprises component control, smelting control, high-temperature diffusion and cogging control, hot-rolled billet heating control and wire rolling control, and comprises the following production steps:

1) Controlling components: the bearing steel comprises the following chemical components in percentage by weight: 1.01%, mn:0.34%, si:0.25%, S:0.012%, P:0.011%, ti:0.002%, ni:0.02%, mo:0.01%, cu:0.02 percent, and the balance of Fe and trace impurities.

2) Smelting control: LF final slag composition: caO:44% of SiO ₂ ：22.9%，MgO：10%，Al ₂ O ₃ :22%, feO:1.1 percent. RH vacuum treatment time 47min, vacuum 67Pa.

The molten steel components meet the following contents through proper converter tapping and alloying, and the molten steel with the following components and temperatures is obtained and used as an early guarantee of LF refining treatment.

The converter tapping and alloying process comprises the following steps: the molten iron loaded into the converter requires that the content of C is 4.2 percent, the content of Si is 0.3 percent, the content of Mn is 0.22 percent, and the rest elements are not required; blowing the molten iron into a converter for 800 seconds by using an oxygen lance, and controlling the carbon drawing temperature to 1650 ℃; in the smelting process of the converter, one or more of lime, fluorite, dolomite and iron oxide ball are added to ensure the components of the converter slag: caO:55% of SiO ₂ :13%, mgO:7% and the restFeO in an amount; alloying is carried out during tapping, the slag discharging amount is noticed to be lower than 3Kg/t, and when the molten steel amount in the ladle is 5t, 100Kg of Al blocks are added; when the molten steel amount in the ladle is 10t, the carburant, ferrosilicon, ferromanganese, ferrochromium and synthetic slag are added in sequence, so that the components of the molten steel meet the requirements. The synthetic slag comprises 49% of CaO and 35% of Al ₂ O ₃ 、15%SiO ₂ And the balance MgO. The carburant is C.

Molten steel components: c:0.92%, si:0.13%, mn:0.29%, P:0.01%, S:0.006%, al:0.035%, ti:0.006%, cr:1.37 percent, and the balance of Fe and trace impurities; the molten steel temperature is as follows: 1530 ℃. The LF refining is carried out through a slagging process (the slagging process is that 500Kg of synthetic slag, 100Kg of lime, 50Kg of calcium carbide and 100Kg of ferrosilicon powder are added when the LF refining is started, and then fine adjustment is carried out by observing the color and the consistency of slag materials on site to finally obtain white slag, namely final slag), so as to obtain the final slag, wherein the components of the final slag are as follows: caO:51% of SiO ₂ ：18%，MgO：8%，Al ₂ O ₃ :22% and FeO:1 percent; the alkalinity R of the final slag is 4.2; in the LF refining process, according to the component inspection condition of the molten steel, adding carbon wires, ferromanganese and ferrochrome for fine adjustment of components, and ensuring that the components of the molten steel obtained by LF refining are the same as those of the molten steel obtained after converter tapping and alloying;

the RH vacuum treated ladle was put into a continuous casting machine and produced at a drawing speed of 0.7m/min with the tundish temperature controlled at 1495 ℃ and the mold flux (mold flux consumption: 0.6Kg mold flux per ton of molten steel; mold flux composition including 35% SiO 2) was added into the mold ₂ ，22%CaO，4%Al ₂ O ₃ ，10%K ₂ O+Na ₂ O, 19%; the crystallizer adopts electromagnetic stirring, the current is set to be 500A, and the frequency is 2.4Hz; for secondary cooling water amount, the total water amount is controlled at 110L/min, dynamic soft reduction is adopted at the tail end, and the total reduction amount is controlled at 9mm, so that a continuous casting billet is obtained; 3) High-temperature diffusion and cogging: the temperature of the preheating section is 880 ℃, and the temperature is kept for 200min; the temperature of the heating section is 1220 ℃, and the temperature is kept for 110min; the temperature of the soaking section is 1260 ℃, and the temperature is kept for 70min. And 6 times of cogging and rolling to obtain hot rolling billets with 160mm sections.

After the high-temperature diffusion is finished, directly entering a cogging mill through a roller way to perform 6 times of high reduction, wherein the temperature of a steel billet is 1200 ℃ during cogging; with the process of cogging, the temperature of the steel billet is gradually reduced, the temperature of the steel billet is 1080 ℃ after the cogging is finished, and the steel billet is rolled into a hot rolling billet with a section of 160mm by adopting 6 times of high reduction;

pass 1: notch width B:320mm; groove bottom width b:285mm; height h:160mm;

pass 2: notch width B:256mm; groove bottom width b:220mm; height h:160mm;

pass 3: notch width B:226mm; groove bottom width b:190mm; height h:160mm;

pass 4: notch width B:201mm; groove bottom width b:170mm; height h:160mm;

pass 5: notch width B:175mm; groove bottom width b:155mm; height h:160mm;

pass 6: notch width B:162mm; groove bottom width b:157mm; height h:160mm.

4) Heating a hot-rolled blank: the temperature of the preheating section is 760 ℃, and the temperature is kept for 60min; the temperature of the heating section is 1190 ℃, and the temperature is kept for 40min; the temperature of the soaking section is 1220 ℃, and the temperature is kept for 30min.

5) Rolling the wire rod: feeding into a finishing mill at 850 ℃, reducing sizing at 880 ℃ and spinning at 780 ℃. And opening the water tanks of the 1 st and 2 nd sections before finish rolling, the water tanks of the 1 st, 2 nd and 3 rd sections between finish rolling and reducing diameter, and the water tanks of the 1 st and 2 nd sections before the reducing diameter and the laying head. The front 5 nozzles are opened in all the water tanks, the cooling water temperature is 30 ℃, the nozzle pressure is 0.7MPa, the back blowing nozzles are all opened, and the gas pressure is 0.7MPa.

Example 3

step one, component control: the bearing steel comprises the following chemical components in percentage by weight: 0.95%, mn:0.25%, si:0.15%, S:0.01%, P:0.025%, ti:0.001%, ni:0.30%, mo:0.10%, cu:0.25 percent, and the balance of Fe and trace impurities;

step two, smelting control: molten steel with the following components and temperatures is obtained through tapping and alloying of the converter and is used as the early guarantee of LF refining treatment;

the converter tapping and alloying process comprises the following steps: the molten iron loaded into the converter requires that the content of C is 3.7 percent, the content of Si is 0.2 percent, the content of Mn is 0.2 percent, and the rest elements do not need to be added; blowing the molten iron into a converter for 700 seconds by using an oxygen lance, and controlling the carbon drawing temperature to be 1560 ℃; in the smelting process of the converter, one or more of lime, fluorite, dolomite and iron oxide ball are added to ensure the components of the converter slag: caO:45% of SiO ₂ :10%, mgO:5% and the balance FeO; alloying is carried out during tapping, the slag discharging amount is noticed to be lower than 3Kg/t, and 80Kg of Al blocks are added when the molten steel amount in the ladle is 4 t; when the molten steel amount in the ladle is 8t, the carburant, ferrosilicon, ferromanganese, ferrochromium and synthetic slag are added in sequence, so that the components of the molten steel meet the requirements. The synthetic slag comprises 48% of CaO, 34% of Al ₂ O ₃ 、14%SiO ₂ And the balance MgO. The carburant is C.

Molten steel components: c:0.89%, si:0.10%, mn:0.27%, P:0.0087%, S:0.005%, al:0.0086%, ti:0.0007%, cr:1.33 percent, and the balance of Fe and trace impurities; the molten steel temperature is as follows: 1505 ℃. The LF refining is carried out through a slagging process (the slagging process is that when the LF refining is started, 500Kg of synthetic slag, 100Kg of lime, 50Kg of calcium carbide and 100Kg of ferrosilicon powder are added, then the fine adjustment is carried out through observing the color and the consistency of slag materials on site, and finally white slag, namely final slag is obtained, and the final slag comprises the following components: caO:40% of SiO ₂ ：25%，MgO：8.8%，Al ₂ O ₃ :25% and FeO:1.2 percent; the alkalinity R of the final slag is 3; in the LF refining process, according to the component inspection condition of the molten steel, adding a carbon wire, ferromanganese and ferrochrome for component fine adjustment, and ensuring that the molten steel obtained by LF refining has the same components as the molten steel obtained after converter tapping and alloying;

after LF refining, the molten steel enters an RH station to be refined continuously, the RH vacuum treatment cycle time is 40min, and the vacuum degree is 50Pa;

the steel ladle after RH vacuum treatment enters a continuous casting machine and adopts the speed of 0.65m/minThe production was carried out at a pulling rate, the tundish temperature was controlled at 1475 ℃ and the mold flux (mold flux consumption: 0.2Kg mold flux per ton molten steel; mold flux composition: 35% SiO% ₂ ，22%CaO，4%Al ₂ O ₃ ，10%K ₂ O+Na ₂ O,19% C, and the balance Fe); the crystallizer adopts electromagnetic stirring, the current is set to be 480A, and the frequency is 2.35Hz; controlling the total water content at 100L/min for secondary cooling water, and controlling the total pressure at 8.5mm under dynamic soft pressure at the tail end to obtain a continuous casting billet;

step three, high-temperature diffusion and cogging: performing high-temperature diffusion on the continuous casting billet, and controlling the temperature of each section as follows:

a preheating section: the temperature is 900 ℃, and the time is 180min;

a heating section: the temperature is 1200 ℃, and the time is 100min;

a soaking section: the temperature is 1250 ℃, and the time is 60min;

after the diffusion is finished, directly entering a cogging mill through a roller way to perform 6 times of large reduction, wherein the temperature of a billet during cogging is 1180 ℃; with the progress of cogging, the temperature of the steel billet is gradually reduced, the temperature of the steel billet after cogging is 1060 ℃, and the steel billet is rolled into hot rolling billet with the section of 160 multiplied by 160mm by adopting 6 times of large reduction;

the reduction process of each pass under the large reduction of 6 passes is as follows:

pass 1: notch width B:320mm; groove bottom width b:285mm; height h:160mm;

pass 2: notch width B:256mm; groove bottom width b:220mm; height h:160mm;

pass 3: notch width B:226mm; groove bottom width b:190mm; height h:160mm;

pass 4: notch width B:201mm; groove bottom width b:170mm; height h:160mm;

pass 5: notch width B:175mm; groove bottom width b:155mm; height h:160mm;

pass 6: notch width B:162mm; groove bottom width b:157mm; height h:160mm.

Step four, heating the hot rolled blank: the hot rolling billet is heated and then rolled, and the temperature of each section is controlled as follows when the hot rolling billet is heated:

a preheating section: the temperature is 800 ℃, and the time is 60min;

a heating section: the temperature is 1150 ℃ and the time is 30min;

a soaking section: the temperature is 1190 ℃, and the time is 30min;

step five, rolling the wire rods:

the control key points of wire rolling are as follows: and the finish rolling temperature is 850 ℃, the sizing temperature is 850 ℃ and the spinning temperature is 780 ℃, and the temperature of each section of water tank reaches the temperature through a nozzle and a recovery section to obtain the wire. 2 sections of water tank penetrating are required before finish rolling, the number of nozzles of each water tank is 10, and the length of a water cooling section before the whole finish rolling is 40m; 3 sections of water passing tanks are arranged between the finish rolling and the reducing diameter, the number of nozzles of each water tank is 10, and the length of a water cooling section before the whole finish rolling is 50m; 2 sections of water passing tanks are arranged between the reducing diameter and the spinning machine, the number of nozzles of each water passing tank is 10, and the length of the water cooling section before the whole finish rolling is 20m; when in production, the cooling water temperature is required to be 35 ℃, the pressure of the cooling nozzle is required to be 0.5MPa, and the pressure of the back flushing nozzle is required to be 0.5MPa after all the back flushing nozzles are opened.

Example 4

step one, component control: the bearing steel comprises the following chemical components in percentage by weight: 1.05%, mn:0.45%, si:0.35%, S:0.025%, P:0.01%, ti:0.001%, ni:0.20%, mo:0.03%, cu:0.10 percent, and the balance of Fe and trace impurities;

step two, smelting control: molten steel with the following components and temperatures is obtained through converter tapping and alloying and is used as the early guarantee of LF refining treatment;

the converter tapping and alloying process comprises the following steps: the molten iron loaded into the converter requires that the content of C is 4.5 percent, the content of Si is 0.5 percent, the content of Mn is 0.3 percent, and the rest elements do not need to be added; blowing molten iron into a converter for 1000 seconds by using an oxygen lance, and controlling the carbon drawing temperature to be 1670 ℃; in the smelting process of the converter, lime, fluorite, dolomite and oxygen are addedOne or more of the iron oxide coating balls ensure that the converter slag components are as follows: caO:55% of SiO ₂ :15%, mgO:8% and the balance FeO; alloying is carried out during tapping, the slag discharging amount is noticed to be lower than 3Kg/t, and 120Kg of Al blocks are added when the molten steel amount in the ladle is 6 t; when the molten steel amount in the ladle is 12t, the carburant, ferrosilicon, ferromanganese, ferrochromium and synthetic slag are added in sequence, so that the components of the molten steel meet the requirements. The synthetic slag comprises 50% of CaO and 35% of Al ₂ O ₃ 、14%SiO ₂ And the balance MgO. The carburant is C.

Molten steel components: c:0.95%, si:0.15%, mn:0.32%, P:0.0109%, S:0.01%, al:0.0559%, ti:0.0074%, cr:1.43 percent, and the balance of Fe and trace impurities; the molten steel temperature is as follows: 1570 deg.C. The LF refining is carried out through a slagging process (the slagging process is that 500Kg of synthetic slag, 100Kg of lime, 50Kg of calcium carbide and 100Kg of ferrosilicon powder are added when the LF refining is started, and then fine adjustment is carried out by observing the color and the consistency of slag materials on site to finally obtain white slag, namely final slag), so as to obtain the final slag, wherein the components of the final slag are as follows: caO:57.2% of SiO ₂ ：15%，MgO：6%，Al ₂ O ₃ :21% and FeO:0.8 percent; the alkalinity R of the final slag is 4.5; in the LF refining process, according to the component inspection condition of the molten steel, adding a carbon wire, ferromanganese and ferrochrome for component fine adjustment, and ensuring that the molten steel obtained by LF refining has the same components as the molten steel obtained after converter tapping and alloying;

after LF refining, the molten steel enters an RH station to be refined continuously, the RH vacuum treatment cycle time is 50min, and the vacuum degree is 100Pa;

the RH vacuum treated ladle was put into a continuous casting machine and produced at a drawing speed of 0.8m/min with the tundish temperature controlled at 1500 ℃ and the mold flux (mold flux consumption: 1.0Kg mold flux per ton molten steel; mold flux composition: 35% SiO 2) added in the mold ₂ ，22%CaO，4%Al ₂ O ₃ ，10%K ₂ O+Na ₂ O,19% C, and the balance Fe); the crystallizer adopts electromagnetic stirring, the current is set to 520A, and the frequency is 2.45Hz; for secondary cooling water amount, the total water amount is controlled at 130L/min, dynamic soft reduction is adopted at the tail end, and the total reduction amount is controlled at 11mm, so that a continuous casting billet is obtained;

a preheating section: the temperature is 850 ℃, and the time is 200min;

a heating section: the temperature is 1250 ℃, and the time is 120min;

a soaking section: the temperature is 1270 ℃, and the time is 90min;

after the diffusion is finished, directly entering a cogging mill through a roller way to perform 6 times of large reduction, wherein the temperature of the steel billet is 1230 ℃ during the cogging; with the progress of cogging, the temperature of the steel billet is gradually reduced, the temperature of the steel billet after cogging is 1100 ℃, and the steel billet is rolled into a hot rolling billet with a section of 160 multiplied by 160mm by adopting 6 times of large reduction;

pass 1: notch width B:320mm; groove bottom width b:285mm; height h:160mm;

pass 2: notch width B:256mm; groove bottom width b:220mm; height h:160mm;

pass 3: notch width B:226mm; groove bottom width b:190mm; height h:160mm;

pass 4: notch width B:201mm; groove bottom width b:170mm; height h:160mm;

pass 5: notch width B:175mm; groove bottom width b:155mm; height h:160mm;

pass 6: notch width B:162mm; groove bottom width b:157mm; height h:160mm.

a preheating section: the temperature is 750 ℃, and the time is 70min;

a heating section: the temperature is 1210 ℃, and the time is 40min;

a soaking section: the temperature is 1230 ℃, and the time is 40min;

step five, rolling the wire rod:

the control key points of wire rod rolling are as follows: and the finish rolling temperature is 880 ℃, the sizing temperature is 880 ℃, the spinning temperature is 810 ℃, and the temperature of each section of water tank reaches the temperature through a nozzle and a recovery section to obtain the wire. 3 sections of water tank penetrating are required before finish rolling, the number of nozzles of each water tank is 12, and the length of a water cooling section before the whole finish rolling is 50m; 4 sections of water tank penetrating are arranged between the finish rolling and the reducing diameter, the number of nozzles of each water tank is 15, and the length of the water cooling section before the whole finish rolling is 70m; 3 sections of water passing tanks are arranged between the reduction diameter and the spinning machine, the number of nozzles of each water passing tank is 15, and the length of a water cooling section before the whole finish rolling is 30m; when in production, the cooling water temperature is required to be 30 ℃, the pressure of the cooling nozzle is required to be 0.6MPa, the back blowing nozzle is completely opened, and the pressure is required to be 0.6MPa.

Comparative example 1: ( This comparative example differs from example 1 only in that: too low S content )

1) Controlling components: the bearing steel comprises the following chemical components in percentage by weight: 1.0%, mn:0.34%, si:0.22%, S:0.002%, P:0.015%, ti:0.003%, ni:0.02%, mo:0.01%, cu:0.02 percent, and the balance of Fe and trace impurities.

2) Smelting control: LF final slag composition: caO:45% of SiO ₂ ：22%，MgO：10%，Al ₂ O ₃ :22%, feO:1.0 percent. RH vacuum treatment time 47min, vacuum 67Pa.

3) High-temperature diffusion and cogging: the temperature of the preheating section is 850 ℃, and the temperature is kept for 180min; the temperature of the heating section is 1228 ℃, and the temperature is kept for 120min; the temperature of the soaking section is 1250 ℃, and the heat preservation time is 70min. And 6 times of cogging and rolling to obtain hot rolling billets with 160mm sections.

4) Heating a hot-rolled blank: the temperature of the preheating section is 750 ℃, and the temperature is kept for 60min; the temperature of the heating section is 1195 ℃, and the temperature is kept for 40min; the temperature of the soaking section is 1222 ℃, and the temperature is kept for 30min.

5) Rolling the wire rods: feeding into a finishing mill at 850 ℃, reducing and sizing at 878 ℃ and spinning at 800 ℃. And opening the water tanks of the 1 st and 2 nd sections before finish rolling, the water tanks of the 1 st, 2 nd and 3 rd sections between finish rolling and reducing diameter, and the water tanks of the 1 st and 2 nd sections before the reducing diameter and the laying head. The front 5 nozzles are opened in all the water tanks, the cooling water temperature is 30 ℃, the nozzle pressure is 0.6MPa, all the back blowing nozzles are opened, and the gas pressure is 0.6MPa.

Comparative example 2: ( This comparative example differs from example 1 only in that: the temperature of the heating section and the soaking section is both too low in high-temperature diffusion and cogging )

A flexible second phase production control method suitable for bearing steel, with the specification of phi 10mm, comprises component control, smelting control, high-temperature diffusion and cogging control, hot-rolled billet heating control and wire rolling control, and comprises the following production steps:

3) High-temperature diffusion and cogging: the temperature of the preheating section is 850 ℃, and the temperature is kept for 150min; the temperature of the heating section is 1100 ℃, and the temperature is kept for 100min; the temperature of the soaking section is 1100 ℃, and the temperature is kept for 50min. And 6 times of cogging and rolling to obtain hot rolling billets with 160mm sections.

4) Heating a hot-rolled blank: the temperature of the preheating section is 750 ℃, and the temperature is kept for 60min; the temperature of the heating section is 1180 ℃, and the temperature is kept for 36min; the temperature of the soaking section is 1190 ℃, and the temperature is kept for 30min.

Comparative example 3: ( This comparative example differs from example 1 only in that: in the hot rolling billet heating process, the temperatures of the heating section and the soaking section are both too low, and the temperature of the hot rolling billet entering the finishing mill and the spinning temperature are both too high )

A flexible second phase production control method suitable for bearing steel, with the specification of phi 14mm, comprises the following production steps of component control, smelting control, high-temperature diffusion and cogging control, hot-rolled billet heating control and wire rolling control:

1) Controlling components: the bearing steel comprises the following chemical components in percentage by weight: 1.0%, mn:0.33%, si:0.23%, S:0.018%, P:0.012%, ti:0.002%, ni:0.02%, mo:0.01%, cu:0.02 percent, and the balance of Fe and trace impurities.

2) Smelting control: LF final slag composition: caO:40% of SiO ₂ ：25.1%，MgO：8%，Al ₂ O ₃ :26%, feO:0.9 percent. RH vacuum treatment time is 50min, and vacuum degree is 70Pa.

3) High-temperature diffusion and cogging: the temperature of the preheating section is 850 ℃, and the temperature is kept for 150min; the temperature of the heating section is 1230 ℃, and the temperature is kept for 120min; the temperature of the soaking section is 1260 ℃, and the temperature is kept for 70min. And 6 times of cogging and rolling into hot rolling billets with 160mm sections.

4) Heating a hot-rolled blank: the temperature of the preheating section is 750 ℃, and the temperature is kept for 60min; the temperature of the heating section is 1100 ℃, and the temperature is kept for 40min; the temperature of the soaking section is 1120 ℃, and the temperature is kept for 30min.

5) Rolling the wire rods: feeding into a finishing mill at 900 ℃, reducing sizing at 880 ℃ and spinning at 900 ℃. And opening a water tank at the 1 st section before finish rolling, water tanks at the 1 st, 2 st and 3 rd sections between finish rolling and reducing diameter, and a water tank at the 1 st section before the reducing diameter and the laying head. The front 5 nozzles are opened in all the water tanks, the cooling water temperature is 30 ℃, the nozzle pressure is 0.6MPa, all the back blowing nozzles are opened, and the gas pressure is 0.6MPa.

The results of comparing the effects of examples 1 to 4 and comparative examples 1 to 3 are shown in table 2 below.

Table 2: comparison of effects

As can be seen from Table 2, in comparative example 3, the presence of the net carbon carbide reduced L ₁₀ Lifetime, but to a lesser extent than the other second phases.

L ₁₀ The life test procedure is as follows:

1) And (3) mounting the test steel ball in a test piece fixture, clamping the test piece fixture on the test shaft and rotating along with the test shaft, and mounting the test steel ball in the hole of the supporting circular truncated cone. When the hand wheel is rotated clockwise, the lead screw rises, and when the test accompanying steel ball is contacted with the test steel ball, the hand wheel is rotated clockwise, so that the test piece is slightly stressed, and then the test can be carried out. And the test tool is provided with a temperature and vibration sensor which can respectively detect the temperature and the vibration of the test piece.

In the test, lubricating oil is used for lubricating and cooling the sample, and return oil is pumped back to the oil tank through the oil pipe.

2) The test load was set to 15KN (instrument maximum load: 19.6 kN);

3) Setting the rotating speed of the transmission shaft to 2500r/min (the highest rotating speed of the instrument is 3000 r/min);

4) The instrument starts to be transported and relevant measurement parameters (load, speed, temperature, current, vibration and the like) are recorded in a computer;

5) When the parameters of load, current, vibration and the like reach set alarm values, the steel ball is considered to be in fatigue failure, and the service life value of the steel ball at the moment is recorded.

It should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: rather, the invention as claimed requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this description, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as described herein. Furthermore, it should be noted that the language used in the specification has been principally selected for readability and instructional purposes, and may not have been selected to delineate or circumscribe the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. The present invention has been disclosed with respect to the scope of the invention, which is to be considered as illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.

Claims

1. A flexible second phase production control method suitable for bearing steel is characterized by comprising the following steps:

step one, component control: the bearing steel comprises the following chemical components in percentage by weight: 0.95 to 1.05%, mn:0.25 to 0.45%, si:0.15 to 0.35%, S:0.01 to 0.025%, P: less than or equal to 0.025%, ti: less than or equal to 0.002%, ni: less than or equal to 0.30 percent, mo: less than or equal to 0.10 percent, cu: less than or equal to 0.25 percent, and the balance of Fe and trace impurities;

molten steel components: c:0.89 to 0.95%, si:0.10 to 0.15%, mn:0.27 to 0.32%, P:0.0087 to 0.0109%, S:0.005 to 0.01%, al:0.0086 to 0.0559%, ti:0.0007 to 0.0074%, cr:1.33 to 1.43 percent, and the balance of Fe and trace impurities; the molten steel temperature is as follows: 1505 to 1570 ℃; and (3) carrying out LF refining to obtain final slag through a slagging process, wherein the final slag comprises the following components: caO:40 to 57.2 percent of SiO ₂ ：15~25%，MgO：6~10%，Al ₂ O ₃ :21 to 25% and FeO:0.8 to 1.2 percent; the alkalinity R of the final slag is 3-4.5; in the LF refining process, according to the component inspection condition of the molten steel, adding carbon wires, ferromanganese and ferrochrome for fine adjustment of components, and ensuring that the components of the molten steel obtained by LF refining are the same as those of the molten steel obtained after converter tapping and alloying;

after LF refining, the molten steel enters an RH station for continuous refining, the RH vacuum treatment cycle time is 40 to 50min, and the vacuum degree is 50 to 100Pa;

putting the ladle subjected to RH vacuum treatment into a continuous casting machine, producing at a drawing speed of 0.65-0.8m/min, controlling the temperature of a tundish at 1475-1500 ℃, and adding protective slag into a crystallizer; the crystallizer is electromagnetically stirred, the current is set to be 480 to 520A, and the frequency is 2.35 to 2.45Hz; controlling the total water content of the secondary cooling water to be 100 to 130L/min, and controlling the total pressure reduction to be 8.5 to 11mm under dynamic soft pressure at the tail end to obtain a continuous casting billet;

a heating section: the temperature is 1200 to 1250 ℃, and the time is 100 to 120min;

a soaking section: the temperature is 1250 to 1270 ℃, and the time is 60 to 90min;

after the diffusion is finished, directly entering a cogging mill through a roller way to perform 6 times of high reduction, wherein the temperature of a steel billet is 1180 to 1230 ℃ during cogging; with the progress of cogging, the temperature of a steel billet is gradually reduced, the temperature of the steel billet is 1060 to 1100 ℃ after cogging is finished, and the steel billet is rolled into a hot rolling billet with a section of 160 multiplied by 160mm by adopting 6 times of large reduction;

a heating section: the temperature is 1150 to 1210 ℃, and the time is 30 to 40min;

a soaking section: the temperature is 1190 to 1230 ℃, and the time is 30 to 40min;

step five, rolling the wire rods:

the control key points of wire rod rolling are as follows: and (3) performing finish rolling at the temperature of 850-880 ℃, the reduced sizing temperature of 850-880 ℃, the spinning temperature of 780-810 ℃, and enabling the water tanks of all sections to pass through a nozzle and a recovery section to reach the temperature range to obtain the wire.

2. A method as claimed in claim 1 adapted for use withThe production control method of the flexible second phase of the bearing steel is characterized in that the process of converter tapping and alloying comprises the following steps: the molten iron filled into the converter is required to contain 3.7 to 4.5 percent of C, 0.2 to 0.5 percent of Si and 0.2 to 0.3 percent of Mn; after molten iron enters a converter, blowing the molten iron for 700 to 1000 seconds by using an oxygen lance, and controlling the carbon drawing temperature to be 1560 to 1670 ℃; in the smelting process of the converter, one or more of lime, fluorite, dolomite and iron oxide ball is added to ensure the components of the converter slag: caO:45 to 55 percent of SiO ₂ :10 to 15%, mgO:5 to 8 percent and the balance of FeO; alloying is carried out during tapping, the slag discharging amount is noticed to be lower than 3Kg/t, and 80 to 120Kg of Al blocks are added when the molten steel amount in the ladle is 4 to 6 t; when the molten steel amount in the ladle is 8-12t, adding a carburant, ferrosilicon, ferromanganese, ferrochromium and synthetic slag in sequence to enable the components of the molten steel to meet the requirements.

3. The method as claimed in claim 2, wherein the synthetic slag contains 48-50% of CaO, 34-35% of Al ₂ O ₃ 、14~15%SiO ₂ And the balance MgO.

4. The method for controlling the production of the flexible second phase suitable for bearing steel according to claim 3, wherein the slagging process comprises the following steps: when LF refining is started, 500Kg of synthetic slag, 100Kg of lime, 50Kg of calcium carbide and 100Kg of ferrosilicon powder are added, and then fine adjustment is carried out by observing the color and the consistency of slag materials on site to finally obtain white slag, namely final slag.

5. The method for controlling production of a flexible second phase suitable for bearing steel according to claim 1, wherein the consumption of mold flux is: 0.2 to 1.0Kg of covering slag is consumed by each ton of molten steel; the casting powder comprises the following components: 35% of SiO ₂ ，22%CaO，4%Al ₂ O ₃ ，10%K ₂ O+Na ₂ O,19% C, and the balance Fe.

6. The method for controlling the production of the flexible second phase suitable for bearing steel according to claim 1, wherein the reduction process of each pass under the large reduction of 6 passes is as follows:

pass 1: notch width B:320mm; groove bottom width b:285mm; height h:160mm;

pass 2: notch width B:256mm; groove bottom width b:220mm; height h:160mm;

pass 3: notch width B:226mm; groove bottom width b:190mm; height h:160mm;

pass 4: notch width B:201mm; groove bottom width b:170mm; height h:160mm;

pass 5: notch width B:175mm; groove bottom width b:155mm; height h:160mm;

pass 6: notch width B:162mm; groove bottom width b:157mm; height h:160mm.

7. The method for controlling the production of the flexible second phase suitable for bearing steel according to claim 1, wherein in the fifth step, at least 2 sections of water tank penetrating nozzles are required before finish rolling, the number of nozzles of each water tank is more than or equal to 10, and the length of the water cooling section before the whole finish rolling is more than or equal to 40m; at least 3 sections of water tank penetrating are arranged between the finish rolling and the reducing diameter, the number of nozzles of each water tank is more than or equal to 10, and the length of a water cooling section before the whole finish rolling is more than or equal to 50m; at least 2 sections of water tank penetrating are arranged between the reducing diameter and the spinning machine, the number of nozzles of each water tank is more than or equal to 10, and the length of the water cooling section before the whole finish rolling is more than or equal to 20m; when in production, the cooling water temperature is required to be less than or equal to 35 ℃, the pressure of the cooling nozzle is required to be more than or equal to 0.5MPa, the back flushing nozzle is fully opened, and the pressure is required to be more than or equal to 0.5MPa.

8. The method for controlling the production of the flexible second phase suitable for the bearing steel as claimed in claim 1, wherein the ratio of the number of oxide and sulfide associated second phase particles to the total number of pure oxide particles and TiA particles in the wire is (1.52-2.09): 1; in TiA, A includes C and/or N.

9. The application of the wire rod obtained by the flexible second phase production control method suitable for bearing steel according to any one of claims 1 to 8 in a rolling body is characterized in that the wire rod is manufactured into the rolling body through drawing and cold heading processes.

10. A rolling body, which is characterized by being made of a wire rod obtained by the flexible second phase production control method suitable for bearing steel according to any one of claims 1 to 8.