CN115652045B - Preparation method of high-wear-resistance impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher hammer - Google Patents

Abstract

The present invention provides a method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer head, wherein a Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer head casting is manufactured by pressure smelting in a vacuum furnace, and a quenching step-by-step partitioning combined heat treatment process step consisting of double-temperature austenitization, controlled cooling and quenching, and progressive partitioning isothermal is adopted to obtain a multiphase nano-microstructure composed of a strengthening phase and a toughening phase, while increasing the hardness and wear resistance of the pulverizer hammer head, and greatly improving its impact toughness. The pulverizer hammer head prepared according to the present invention can extend the comprehensive service life and reduce or prevent the occurrence of its early failure.

Description

Preparation method of a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer

Technical Field

The invention belongs to the technical field of preparation of novel wear-resistant and impact-resistant materials, and specifically relates to a method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer.

Background technique

Hammer crushers are widely used to crush materials in industries such as building materials, electricity, mining, metallurgy, and roads. The hammer head of a crusher is a key part of the crusher and also a vulnerable part, with huge demand.

Most of the hammer heads of crushers currently used in the market are cast from ordinary high manganese steel (such as M13, Mn3Cr, etc.), and are made by quenching (water toughening) after annealing and cutting. Its matrix structure is austenite, and the surface hardness is generally 240-280HB. If ordinary high manganese steel hammer heads work under high energy impact, and the hardness of the crushed materials is relatively high (such as ore, coal gangue, steel, etc.), the hammer head surface will produce strong work hardening phenomenon. After hardening, the hardness of the hammer head working surface can be increased to 350-500HB. However, in actual use, high stress conditions are less than 10%. Most hammer heads, especially small and medium-sized hammer heads, are not subjected to large impact stress, and the hardness of the crushed materials is not high. It is impossible to increase the surface hardness of the hammer heads through significant work hardening, and it is impossible to form a hardened layer with high hardness and deep depth on the working surface. Therefore, the wear resistance of ordinary high manganese steel cannot be fully utilized, resulting in early failure under wear and impact, and a short service life (as short as a few days and as long as less than a month), which not only causes serious waste of resources, but also increases equipment maintenance time and use costs.

In recent years, various manufacturers and research institutes have been committed to the research and development of new crusher hammer materials and processes. The service life of the high-chromium cast iron hammer developed can be increased by 1-2 times compared with high-manganese steel, but local brittle fracture under large impact loads cannot be avoided; recent studies have shown that by adding a certain amount of vanadium and a small amount of tungsten and molybdenum elements during the smelting process, the high-vanadium high-speed steel hammer prepared by the composite casting method has higher wear resistance. However, its high manufacturing cost and complex preparation process (such as the need for additional rust removal and pickling steps) currently affect its reasonable hardness in actual production and the best use effect.

With the continuous development of new pressure smelting technologies (such as pre-pressurized electroslag remelting and pressure induction melting, etc.), it has become possible to manufacture high-quality nitrogen-containing alloy steel in industry and laboratories. Studies have shown that when a portion of carbon is used to reasonably replace nitrogen, the comprehensive properties of steel such as hardness, toughness and corrosion resistance can be stably improved. Therefore, on this basis, the present invention designs a carbon-nitrogen (C-N) alloy steel, combines a novel progressive partitioning isothermal heat treatment process, and adjusts the partitioning diffusion of C and N atoms and the composition and quantity of the microstructure structure, so as to greatly improve the hardness and strength of the alloy steel, so that it has both the effect of deformation strengthening of carbon-rich austenite and strain austenite induced plasticity, thereby significantly improving the wear resistance and impact resistance of the crusher hammer, meeting the harsh actual production requirements and environment of the crusher, and providing an innovative solution for improving the service life of the crusher hammer.

Summary of the invention

The purpose of the invention is to provide a method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer head in view of the deficiencies in the prior art.

The present invention adopts the following technical solutions:

A method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer head comprises the following steps:

S1. Smelting and casting: placing a hammer alloy raw material into a vacuum furnace, stirring and melting it under a nitrogen atmosphere, and then pouring it to cast the hammer into shape, wherein the chemical composition and mass fraction of the hammer alloy raw material are: 0.30-0.50% C, 0.2-0.5% N, 2.0-2.5% Mn, 1.5-2.5% Si, 1.0-2.0% Cr, 0.1-0.2% Mo, 0.15-0.25% Ti, 0.01-0.03% S, 0.005-0.02% P, and the rest is Fe;

S2. Pre-uniform heat treatment: keep the cast hammer head at 850-880°C, then keep it at 650-680°C, and finally take it out and air cool it to room temperature;

S3, dual-temperature austenitizing treatment: first, the preheated hammer head is placed at 800-860℃ for low-temperature austenitizing treatment, and then austenitized at 880-910℃;

S4, controlled cooling and quenching treatment: the hammer head is quickly taken out from the high temperature furnace and controlled cooling is performed, and then the controlled cooling hammer head is placed in a water-based quenching liquid for 40-250 seconds, and the hammer head is manually rotated at the same time;

S5. Progressive partitioning isothermal treatment: put the hammer head after quenching treatment into a 100-140℃ resistance furnace for a period of time, and then carry out isothermal treatment at 140-180℃, then raise the temperature to 200-240℃ for isothermal treatment, and finally take out the hammer head and air cool it to room temperature.

Furthermore, in S1, the hammer alloy raw material is melted in a vacuum furnace at a temperature of 1500-1600°C, a nitrogen pressure of 10 bar, and a pouring temperature of 1450-1550°C.

Furthermore, in S2, the heating and holding time of the hammer head at 850-880°C is determined according to its thickness, and the holding time is 0.5-0.8 min per millimeter of the effective thickness of the hammer head; the holding time of the hammer head at 650-680°C is 3-5h.

Furthermore, in S3, the low-temperature austenitizing treatment time of the hammer head is determined according to its thickness, and the heat preservation is carried out for 0.3-0.5 min per millimeter of effective thickness; the austenitizing treatment time of the hammer head at 880-910°C is 30-50 min.

Furthermore, in S4, after the hammer head is quickly taken out from the high temperature furnace, its cooling rate is controlled to be 200-400°C/min, and the cooling time is 2-15s.

Further, in S4, the water-based quenching liquid is 60-100°C, and the speed of the manual rotating hammer is 0.4-0.8 m/s;

Furthermore, in S5, the hammer head after quenching treatment is kept in a resistance furnace at 100-140°C for 5-8h, isothermally treated at 140-180°C for 2-6h, and isothermally treated at 200-240°C for 30min-1h.

The present invention designs a carbon-nitrogen (C-N) alloy steel, combines it with a novel progressive partitioning isothermal heat treatment process, and adjusts the partitioning diffusion of C and N atoms as well as the composition and quantity of the microstructure, so as to greatly improve the hardness and strength of the alloy steel, so that it has both the effect of deformation strengthening of carbon-rich austenite and strain-induced plasticity of austenite, thereby significantly improving the wear resistance and impact resistance of the crusher hammer head, meeting the harsh actual production requirements and environment of the crusher, and providing an innovative solution for improving the service life of the crusher hammer head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a heat treatment process of the present invention;

FIG2 is a scanning electron microscope impact fracture morphology of a pulverizer hammer head (with an impact toughness value of 96 J/cm ² and a hardness value of 55.5 HRC) after heat treatment in Example 1 of the present invention;

FIG. 3 is a transmission electron microscope microstructure morphology of the hammer head of the pulverizer after heat treatment in Example 2 of the present invention (the sample has an impact toughness value of 94 J/cm ² and a hardness value of 56.5 HRC).

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The present invention provides a method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer, which mainly includes two steps of smelting and casting and heat treatment processing:

Stage 1: Smelting and Casting

The ingredients are prepared according to (0.30-0.50% C, 0.2-0.5% N, 2.0-2.5% Mn, 1.5-2.5% Si, 1.0-2.0% Cr, 0.1-0.2% Mo, 0.15-0.25% Ti, 0.01-0.03% S, 0.005-0.02% P, and the rest is Fe), and then the hammer alloy raw material is placed in a vacuum furnace (the furnace temperature range is controlled at 1500-1600°C), stirred and melted in a nitrogen atmosphere (10 bar, the required nitrogen content can be adjusted by the nitrogen atmosphere), and then poured (the pouring temperature is controlled at 1450-1550°C), and finally the hammer is cast.

Step 2: Heat treatment process

The overall heat treatment process implementation diagram is shown in Figure 1, which mainly includes the following steps:

1. Pre-uniform heat treatment

This step belongs to the category of pretreatment before heat treatment. Its purpose is to obtain uniformly distributed pearlite microstructure and pave the way for the implementation of subsequent heat treatment. It mainly includes the following processes: first, the hammer head is heated and kept warm at 850-880℃. The holding time is calculated and set according to the size of the hammer head. The insulation time is 0.5-0.8min per millimeter of effective thickness. Anti-oxidation treatment can be carried out according to actual production conditions; secondly, it is heated and kept warm at 650-680℃ for 3~5h, and finally taken out and air-cooled to room temperature.

2. Quenching, step-by-step partitioning and combined heat treatment

Step 1: Dual-temperature austenitizing

It consists of two processes: low-temperature austenitization and high-temperature austenitization. First, the hammer head is placed in 800-860℃ for low-temperature austenitization, and the temperature is kept at 0.3-0.5min per millimeter of the effective thickness of the hammer head; then the hammer head is austenitized at a higher temperature of 880-910℃ for 30-50min.

Step 2: Controlled cooling and quenching

The hammer head is quickly taken out from the high temperature furnace, and its cooling rate is controlled at 200-400℃/min, and the cooling time is 2-15s; then the hammer head after controlled cooling is placed in a water-based quenching liquid with a temperature of 60-100℃ and maintained for 40-250s, and the hammer head is manually rotated at a speed of 0.4-0.8m/s.

Step 3: Progressive partitioning isothermal treatment

The hammer head after quenching treatment is placed in a 100-140℃ resistance furnace and kept warm for 5-8h. After completion, it is kept isothermally at 140-180℃ for 2-6h, and then the temperature is raised to 200-240℃ and kept isothermally for 30min-1h.

Step 4: Air cooling to room temperature.

Example

The present embodiment provides a method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer, which specifically comprises the following steps:

Step 1: Set the temperature of the vacuum furnace to 1500-1600°C, control the nitrogen pressure to about 10 bar, and prepare the materials according to the ratio of 0.4% C, 0.35% N, 2.5% Mn, 2.0% Si, 1.5% Cr, 0.2% Mo, 0.2% Ti, 0.01% S, 0.01% P, and the rest is Fe. Put the alloy into the furnace for stirring and melting. After the pouring temperature is 1450-1550°C, pour and cast to obtain a crusher hammer head with an effective thickness of 120 mm.

Step 2: Cover the hammer head with sufficient carbon powder and put it into a container. Place the container in an 860°C electric furnace and keep it warm for 60 minutes. Take out the hammer head and quickly put it into another 660°C electric furnace and keep it warm for 3.5 hours. Then take it out and air cool it to room temperature.

Step 3: Using the same anti-oxidation measures, place the hammer head in an 820℃ electric furnace for 36 minutes, then raise the furnace temperature to 880℃ and keep it for another 30 minutes.

Step 4: Take out the hammer, cool it quickly in the air (400℃/min) for 8 seconds, then put it into 60℃ water-based quenching liquid, manually rotate the hammer at a speed of about 0.5m/s and keep it for 160s.

Step 5. Quickly place the quenched hammer head into a 110°C resistance furnace and keep it warm for 8 hours, then raise the furnace temperature to 160°C and maintain isothermal treatment for 4 hours. After completion, raise the furnace temperature to 220°C and keep it warm for 1 hour. Finally, take it out and air cool it to room temperature to obtain a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher hammer head.

Three V-shaped impact notch standard specimens (V-shaped notch groove depth of 2mm, specimen size of 10mm×10mm×55mm) were cut from the surface area of the hammer prepared in Example 1, and the room temperature impact mechanical properties were tested. The impact absorption energy was 89J/cm ² , 96J/cm ² , 85J/cm ² , respectively, and the corresponding hardness was 57.5HRC, 55.5HRC, 58HRC. From the SEM impact fracture of Figure 2 (impact value of 96J/cm ² , hardness of 55.5HRC specimen), it can be seen that the hammer fracture presents a typical ductile-brittle mixed fracture mode under the impact external force. The quasi-cleavage section is clearly visible, and there are obvious dimples of relatively uniform size, indicating that it has good impact toughness.

Example

The present embodiment provides a method for preparing a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer, which specifically comprises the following steps:

Step 1: Set the temperature of the vacuum furnace to 1500-1600°C, control the nitrogen pressure to about 10 bar, and prepare the materials according to the ratio of 0.3% C, 0.25% N, 2.0% Mn, 1.5% Si, 1.0% Cr, 0.2% Mo, 0.2% Ti, 0.01% S, 0.01P, and the rest is Fe. Put the alloy into the furnace for stirring and melting. After the pouring temperature is 1450-1550°C, pour and cast to obtain a crusher hammer head with an effective thickness of 80 mm.

Step 2: Cover the hammer head with sufficient carbon powder and put it into a container. Place the container in an 860°C electric furnace and keep it warm for 60 minutes. Take out the hammer head and quickly put it into another 660°C electric furnace and keep it warm for 3.0 hours. Then take it out and air cool it to room temperature.

Step 3: Using the same anti-oxidation measures, place the hammer head in an 820℃ electric furnace and keep it for 35 minutes. Then, raise the temperature to 880℃ and keep it for another 30 minutes.

Step 4: Take out the hammer, cool it quickly in the air (400℃/min) for 5 seconds, then put it into a 60℃ water-based quenching liquid, manually rotate the hammer at a speed of about 0.5m/s and keep it for 100s.

Step 5. Quickly place the hammer head after quenching treatment into a 110°C resistance furnace and keep it warm for 5 hours, then raise the furnace temperature to 160°C and maintain isothermal treatment for 2 hours. After completion, raise the furnace temperature to 220°C and keep it warm for 0.5 hours. Finally, take it out and air cool it to room temperature to obtain a highly wear-resistant and impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher hammer head.

Three V-shaped impact notch standard specimens (V-shaped notch groove depth is 2 mm, specimen size is 10 mm×10 mm×55 mm) were cut from the surface area of the hammer head prepared in this embodiment, and room temperature impact mechanical properties test was carried out. The impact absorption energies were 93 J/cm ² , 94 J/cm ² , and 88 J/cm ² , respectively, and the corresponding hardnesses were 58.5 HRC, 56.5 HRC, and 57.5 HRC.

The transmission electron microscopic structure of the Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer hammer is shown in Figure 3. It can be seen that the hammer prepared in this embodiment is composed of tempered martensite with a local carbon aggregation zone inside and strip bainite around it and film-like residual austenite, wherein the width of the bainite strip is approximately in the range of 5-50nm, and the film thickness of the residual austenite is 5-10nm. In this multiphase microstructure, it contains about 60% strengthening phase (bainite and tempered martensite) and 40% toughening phase (residual austenite). Not only that, it can also be observed that there is a high density of dislocations in the strip bainite and film-like residual austenite. Therefore, the proportion, distribution and morphology of the above strengthening and toughening phases can enable the alloy hammer to withstand external forces, especially high impact stresses, and each phase can cooperate to strengthen and toughen, give play to the advantages of the nanostructure, fully reflect the effects of phase transformation-induced plasticity and strengthening, and greatly improve its wear resistance and impact resistance.

This comparative example provides a composite metal hammer head, and the preparation method thereof is as follows:

Step 1: Preparation of the hammer handle:

The alloy composition by weight percentage is C: 0.35%, Si: 0.4%, Mn: 1.6%, and the balance is Fe. The mixture is cast into a sand casting cavity of the required hammer handle shape at 1500°C and cooled to form. After annealing, the hammer handle is sanded and polished at 100°C, and heated at 200°C in a heat treatment furnace for standby use.

Step 2: Preparation of hammer head:

The alloy components by weight percentage are C: 2.6%, Si: 0.7%, Cr: 18%, Mn: 1.6%, Mo: 1.2%, Ni: 1.4%, S: 0.03%, P: 0.03%, and the balance is Fe. The materials are prepared, smelted at 1500℃, poured at 1408-1380℃ at the junction of the above-mentioned hammer handle and hammer head, kept warm for 8 hours, removed from the mold and cooled → polished → heated to 450℃ and kept warm for 120 minutes → kept warm at 650℃ for 120 minutes → kept warm at 800℃ for 120 minutes → kept warm at 920℃ for 120 minutes → air quenched to 105℃ → tempered at 250℃ → naturally cooled to below 100℃ to obtain the hammer head.

The hammer prepared in this comparative example was subjected to impact mechanical property test. Three V-shaped impact notch standard specimens (the V-shaped notch groove depth is 2 mm, and the specimen size is 10 mm×10 mm×55 mm) were cut from the surface area of the hammer head for room temperature impact mechanical property test. The impact absorption energies were 4 J/cm ² , 5 J/cm ² , and 5.5 J/cm ² , respectively, and the corresponding hardnesses were 58.5HRC, 58.0HRC, and 57.5HRC.

It can be seen that the hardness of the hammer heads prepared in Examples 1 and 2 of the present invention is similar to that of the comparative hammer heads, but the impact toughness can be improved by about 19.0 times, which can effectively prevent local brittle cracking and peeling of the hammer head during use, and greatly improve the service life of the hammer head.

The above are only preferred implementations of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims (7)

1. The preparation method of the high-wear-resistance impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher hammer is characterized by comprising the following steps of:

S1, smelting and casting: placing the hammer head alloy raw materials into a vacuum furnace, stirring and smelting under nitrogen atmosphere, then pouring, and casting the hammer head for molding, wherein the chemical composition and mass fraction of the hammer head alloy raw materials are ：0.30-0.50% C,0.2-0.5% N,2.0-2.5% Mn,1.5-2.5% Si,1.0-2.0% Cr,0.1-0.2% Mo,0.15-0.25% Ti,0.01-0.03% S,0.005-0.02% P,, and the balance is Fe;

s2, carrying out uniform heat treatment in advance: preserving heat of the cast hammer at 850-880 ℃, preserving heat at 650-680 ℃, and finally taking out and air cooling to room temperature;

S3, double-temperature austenitizing: firstly, placing the preheated hammer head at 800-860 ℃ for low-temperature austenitizing treatment, and then austenitizing at 880-910 ℃;

s4, cooling control and quenching treatment: taking out the hammer from the high-temperature furnace rapidly, controlling cooling, putting the hammer after controlling cooling into water-based quenching liquid, keeping for 40-250s, and simultaneously manually rotating the hammer;

S5, progressive compounding and the like temperature treatment: placing the quenched hammer head into a resistance furnace with the temperature of 100-140 ℃ for heat preservation for a period of time, carrying out isothermal treatment at 140-180 ℃ after finishing, then carrying out isothermal treatment by raising the temperature to 200-240 ℃, and finally taking out the hammer head for air cooling to room temperature.

2. The method for preparing the hammer of the Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer, according to claim 1, wherein in S1, the smelting temperature of the hammer alloy raw material in a vacuum furnace is 1500-1600 ℃, the nitrogen gas pressure is 10bar, and the casting temperature is controlled at 1450-1550 ℃.

3. The method for preparing the hammer head of the high-wear-resistance impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher, according to claim 1, wherein in S2, the heating and heat preservation time of the hammer head is determined according to the thickness of the hammer head at 850-880 ℃, and the heat preservation is carried out according to the effective thickness of the hammer head per millimeter for 0.5-0.8 min; the heat preservation time of the hammer head is 3-5 h at 650-680 ℃.

4. The method for preparing the hammer head of the high-wear-resistance impact-resistance Fe-Cr-Mn-Si-Mo-C-N alloy crusher, according to claim 1, wherein in S3, the low-temperature austenitizing treatment time of the hammer head is determined according to the thickness of the hammer head, and the hammer head is subjected to heat preservation for 0.3-0.5min per millimeter of effective thickness; the austenitizing treatment time of the hammer head is 30-50min at 880-910 ℃.

5. The method for preparing the hammer head of the high-wear-resistance impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher, according to claim 1, wherein in the step S4, after the hammer head is rapidly taken out of a high-temperature furnace, the cooling speed is controlled to be 200-400 ℃/min, and the cooling time is controlled to be 2-15S.

6. The method for preparing the hammer of the Fe-Cr-Mn-Si-Mo-C-N alloy pulverizer, according to claim 1, wherein in the step S4, the water-based quenching liquid is at 60-100 ℃, and the manual rotation hammer speed is 0.4-0.8m/S.

7. The method for preparing the hammer head of the high-wear-resistance impact-resistant Fe-Cr-Mn-Si-Mo-C-N alloy crusher according to claim 1, wherein in S5, the heat preservation time of the hammer head subjected to quenching treatment in a resistance furnace at 100-140 ℃ is 5-8h, the isothermal treatment time at 140-180 ℃ is 2-6h, and the isothermal treatment time at 200-240 ℃ is 30min-1h.