CN115074641B - HB 400-grade high-wear-resistance cold-bendable steel plate and production method thereof - Google Patents

Abstract

The HB400 grade high wear-resistant cold-bendable steel plate comprises, by weight, 0.14% -0.18% of C, 1.1% -1.50% of Si, 0.7% -1.0% of Mn, 0.12% -0.20% of Nb, 0.15% -0.35% of Cr and 0.4% -0.6% of Ni; nb is less than or equal to 0.03, si+Ni is less than or equal to 1.5 percent and less than or equal to 2.0 percent, al is 0.040 percent to 0.060 percent, and the balance is Fe and unavoidable impurities. Compared with the prior art, the invention has the beneficial effects that: can be produced by continuous casting; the surface hardness is more than HB400, and AKV at minus 40 ℃ is more than or equal to 40J; the wear resistance is more than 1.4 times of that of the low-alloy wear-resistant steel plate with the same hardness; the product has good cold forming performance and is qualified by 180-degree cold bending D=3a.

Description

A kind of HB400 grade high wear-resistant cold-bendable steel plate and its production method

technical field

The invention belongs to the field of metal materials, and in particular relates to an HB400 grade high wear-resistant cold-bendable steel plate and a production method thereof, which can be used in the manufacture of wear-resistant spare parts in the fields of engineering machinery, mining, metallurgy, and coal machinery.

Background technique

General low-alloy wear-resistant steel adopts the design of martensite matrix and low-hardness carbides such as Cr, Mo, V, Ti to enhance wear resistance, and is produced by heat treatment of quenching and low-temperature tempering. The hardness level of HB400 is ordinary low-alloy Brinell The service life of wear-resistant steel is generally about twice that of Q345B. It is widely used in construction machinery, coal mining machinery and other fields, but its cold bending performance is relatively poor. Improving the wear resistance of wear-resistant steel can generally be achieved by increasing the carbon content and alloy content of the steel plate, which will lead to poor processing performance, welding performance, and poor cold-formation performance of the steel.

In recent years, in the production process of road construction machinery, heavy mining vehicles, coal machinery, power plants, cement and other industries, due to the hard materials and fast movement, the wear and tear on the equipment is very serious, resulting in fast wear of spare parts and short maintenance cycles. There is an urgent need for a A high wear resistance HB400 grade wear-resistant steel plate prolongs the service life of spare parts without increasing the hardness. At the same time, some wear-resistant spare parts with complex shapes need to be bent and formed during the preparation process, and the cold bendability of ordinary low-alloy martensitic wear-resistant steel cannot meet its requirements.

In order to improve the wear resistance of low-alloy steel plates, in recent years, some steel mills at home and abroad have increased the content of Ti and V in low-alloy wear-resistant steels, and used the martensitic matrix to increase the hardness of TiC and VC precipitation to enhance wear resistance. It has enhanced resistance, but its plasticity and toughness are poor, and it cannot be cold-formed, so it is difficult to popularize in large quantities.

Tianjin Leigong Welding Materials Co., Ltd., Lei Wanjun; Chen Zerong; Grinding plate, including low-carbon steel plate or low-carbon alloy steel plate, said low-carbon steel plate or low-carbon alloy steel plate is welded with a wear-resistant alloy layer, characterized in that: the percentage of the total mass of the wear-resistant alloy layer, said wear-resistant The content of each component in the alloy layer is as follows: C: 0.35-0.55%; Si: 2-2.4%; Mn: 2.7-3.2%; Cr: 11-12.5%; Mo: 2.5-2.9%; V: 0.7-1.8%; W: 2.2-3.6%; B: 0.7-1.1%; the rest is iron. The invention has the advantages of being able to ensure the smooth surface of the wear-resistant plate and having good wear resistance. The invention is produced by the process of bimetal composite surfacing welding, which has complicated procedures and high cost, and the steel plate cannot be shaped and processed due to the high hardness of the surfacing welding layer.

Baoshan Iron and Steel Co., Ltd., Li Hongbin, Yao Liandeng, Miao Yuchuan and others applied for the publication (announcement) number: CN103146997A patent document "a low-alloy high-toughness wear-resistant steel plate and its manufacturing method", which involves a low-alloy high-toughness wear-resistant Steel plate and its manufacturing method, its chemical composition (wt%) is: C: 0.08-0.20%, Si: 0.10-0.60%, Mn: 1.00-2.00%, B: 0.0005-0.0040%, Cr≤1.50%, Mo≤ 0.80%, Ni≤1.50%, Nb≤0.080%, V≤0.080%, Ti≤0.060%, Al: 0.010-0.080%, Ca: 0.0010-0.0080%, N≤0.0080%, O≤0.0080%, H≤0.0004 %, P≤0.015%, S≤0.010%, and satisfy 0.20%≤(Cr/5+Mn/6+50B)≤0.55%, 0.02%≤(Mo/3+Ni/5+2Nb)≤0.45%, 0.01%≤(Al+Ti)≤0.13%, the rest is Fe and unavoidable impurities. The invention reduces the content of carbon and alloying elements, makes full use of the refinement and strengthening of microalloying elements such as Nb and Ti, and adopts the TMCP process. The wear-resistant steel plate has high hardness, good toughness, easy welding, and excellent wear resistance. It is suitable for Wearable parts in various mechanical equipment. Its mechanical properties: tensile strength greater than 1200MPa, elongation greater than 12%, Brinell hardness greater than 400HB, Charpy V-type longitudinal impact energy greater than 60J at -40°C. The invention has high strength, shaping, welding and other performances, but its wear resistance is comparable to ordinary martensitic wear-resistant steel with the same hardness.

Jiangyin Xingcheng Special Steel Co., Ltd., Liu Jun, Li Guozhong, Xu Xiaohong, etc. Publication (Announcement) No.: CN111996441A patent document "A TiC-enhanced martensitic wear-resistant steel plate with high toughness and good bending performance and its manufacturing method", It relates to a TiC enhanced martensitic wear-resistant steel plate with high toughness and good bending performance and a manufacturing method thereof, the element content: C: 0.18-0.30%, Si: ≤0.30%, Mn: 0.60-1.20%, Ti: 0.20 ～0.40%, Al: 0.04～0.08%, Ni: ≤0.10%, Cu: ≤0.10%, Cr: 0.20～1.00%, Mo: 0.10～0.60%, B: 0.0010～0.0040%, Ca: 0.001～0.005% , P: ≤0.015%, S: ≤0.003%, O: ≤0.0015%, N: ≤0.0030%, H: ≤0.0002%, the balance is Fe; and satisfy 0.13≤C-Ti/4≤0.25, thus After the formation of TiC, the hardness of the martensite matrix reaches 400-480HB; the carbon equivalent CEV: ≤0.65%, and the machining and welding performance can meet the requirements of high wear resistance equipment manufacturing. The technological process is: converter or electric furnace steelmaking -> LF refining -> vacuum degassing -> Ca treatment -> continuous casting -> heating -> hot rolling -> quenching -> low temperature tempering. Elongation A50≥8%; low temperature impact toughness: -40°C Akv≥20J, cold bending performance of steel plate: d=5a cold bending at 90° without cracking. The wear resistance reaches 1.4 times and above that of low alloy martensitic wear-resistant steel NM450. The steel plate prepared by the method has good machinability, and the hardness can reach HBW400-480. The invention has good formability, but high Ti content, making smelting and continuous casting difficult.

Jiefuyi Iron and Steel Co., Ltd., Yusuke Terasawa; Naoki Takayama; Kenji Hayashi; Japanese patent documents of Hase Kazuo, application publication number CN109072367A, "wear-resistant steel plate and method for manufacturing wear-resistant steel plate", disclosed It has the following component composition and structure, and the component composition contains by mass %: C: 0.10-0.23%, Si: 0.01-1.0%, Mn: 0.30-3.00%, P: 0.025% or less, S: 0.02% or less , Cr: 0.01 to 2.00%, Al: 0.001 to 0.100%, and N: 0.01% or less, and the balance is composed of Fe and unavoidable impurities. In the structure, a depth of 1 mm from the surface of the wear-resistant steel plate The volume ratio of martensite at the center of the wear-resistant steel plate is 90% or more, the particle size of prior austenite in the central part of the thickness of the wear-resistant steel plate is 80 μm or less, and the hardness at a depth of 1 mm from the surface of the wear-resistant steel plate is A wear-resistant steel plate with a Brinell hardness of 360-490HBW 10/3000 and a method for manufacturing the wear-resistant steel plate. The alloy composition of the steel plate is complex, the cost is high, and it only has ordinary wear resistance.

It can be seen that the existing HB400 wear-resistant steel plate has the following deficiencies:

1. The composition and process are complex, requiring heterogeneous compounding or surfacing;

2. Difficulty in smelting and continuous casting;

3. Can not be cold-formed;

4. Insufficient wear resistance.

Contents of the invention

The purpose of the present invention is to provide a kind of HB400 high wear-resistant cold-bendable steel plate and its production method. The present invention adopts a new wear-resistant concept on the basis of low-alloy wear-resistant steel, reasonably increases the Nb content in the steel, and utilizes dispersion precipitation The high-hardness niobium carbide particles enhance the wear resistance, which is more than 1.4 times the wear resistance of ordinary wear-resistant steel plates with the same hardness. Using unique smelting, rolling, and heat treatment production processes, the surface of the steel plate is subjected to crack arrest treatment to form a partly decarburized layer, coupled with reasonable residual austenite content control, the Brinell hardness 400HB grade is produced with good plasticity and Toughness High wear resistance low alloy wear-resistant steel that can be cold-formed.

To achieve the above object, the present invention adopts the following technical solutions:

A HB400 grade high wear-resistant and cold-bendable steel plate, the chemical composition of the steel is calculated by weight percentage: C 0.14%-0.18%, Si 1.1%-1.50%, Mn 0.7%-1.0%, Nb 0.12%-0.20%, Cr 0.15%～0.35%, Ni0.4%～0.6%, Al 0.040%～0.060%, P≤0.012%, S≤0.002%, [N]≤0.0030%, [H]≤0.00015%, [O]≤ 0.0015%; the balance is Fe and unavoidable impurities; and C*Nb≤0.0004%, 1.5%≤Si+Ni≤2.0%.

The chemical composition design of the steel plate of the present invention is mainly characterized by microalloying of carbon, niobium and silicon, and the alloy content is relatively low, which is convenient for smelting and continuous casting. Through continuous casting, controlled rolling and controlled cooling, low temperature tempering heat treatment is carried out to obtain HB400 grade steel plate with good ductility, toughness and wear resistance.

The reasons for the designed elements of the present invention are:

C: In order to ensure the high strength and hardness of the steel plate and stabilize the amount of residual austenite in the steel, a considerable carbon content is required as a guarantee. At the same time, carbon can form carbide precipitation with Nb, increasing wear resistance. If the carbon content is too high, the welding performance will decline, and it will also affect the solid solution and precipitation of Nb in the steel. In order to ensure that the steel plate has high wear resistance, good welding performance, formability, and wear resistance, the C content is controlled in the present invention. 0.14%～0.18%;

Si: The key addition element of the present invention. It is a non-carbide-forming element, and its main function is to inhibit the precipitation of carbides, stabilize the residual austenite content in steel, help improve the low-temperature toughness and plasticity of steel plates, and ensure good cold bending ability. Simultaneously, it plays the role of stabilizing the thickness of the decarburized layer, but when Si is too much, the welding performance will be reduced, so the Si content is controlled at 1.1% to 1.5% in the present invention;

Mn: The main function is to improve the hardenability and promote the solid solution of Nb. It is beneficial to the improvement of strength and wear resistance, but when the content is too high, it is easy to form center segregation, which makes the center of the slab prone to cracks; it is not conducive to cold forming, so the content of Mn in the present invention is controlled at 0.7% to 1.0%;

Nb: an important additional element in the present invention. Main function: increase wear resistance and plasticity. Nb is a strong carbon and nitrogen compound forming element. It can be combined with C and N in steel to form NbC, Nb(C, N) and other compounds. It has the characteristics of high chemical stability and high hardness, and can form 1.4 times the wear resistance of ordinary wear-resistant steel. In addition, the addition of Nb element makes the low-temperature austenite structure induce a large amount of carbon and nitrogen during the rolling process. The compound has the effect of increasing hardenability and precipitation strengthening; Nb dissolved in austenite inhibits austenite recrystallization and refines austenite grains during the two-stage rolling process. It is beneficial to the cold bending performance of the steel plate. However, if the Nb content is too high, the mechanical properties of the steel plate will be affected. Therefore, the added amount of Nb in the present invention is 0.12%-0.20%.

Ni: non-carbide forming element, the main function is to improve the toughness and plasticity of steel, if the Ni content is less than 0.4%, the required effect cannot be achieved, and if the Ni content is greater than 0.6%, the cost is too high, and austenite may remain during quenching Too much body. The present invention controls Ni: 0.4% to 0.6%. Since both Si and Ni have the effect of promoting the content of retained austenite, the present invention controls the content of retained austenite to 5 to 10%. The total amount of Si+Ni is controlled, so in the present invention, 1.5%≤Si+Ni≤2.0%.

Al: an effective element for deoxidation and nitrogen fixation. It can reduce oxide inclusions in the steel and purify the steel, which is beneficial to improve the formability of the steel plate. If the content is too high, it will cause casting difficulties, and a large number of Al ₂ O ₃ inclusions will be formed in the steel, resulting in poor ductility and nitrogen fixation. Ensure that niobium is mainly combined with carbon. Therefore, in the present invention, Al: 0.04% to 0.06%%.

Cr: The effect of increasing the hardenability of steel. Chromium is a strong carbide forming element that increases strength and hardness. Adding too much Cr will affect weldability, so the present invention controls Cr: 0.15%-0.35%.

Impurity elements: In order to ensure that the steel plate has good plasticity and toughness, and avoid fragmentation during wear and cracks during cold bending, the present invention controls P≤0.012%, S≤0.002%, [H]≤0.00015%, [O] ≤0.0015%.

The residual austenite content in the steel is 5% to 10%, and the thickness of the partially decarburized layer on the surface of the steel plate is 1 to 2 mm.

Under the same experimental conditions, the wear resistance of the steel plate is more than 1.4 times that of the NM400 steel plate with the same hardness, and the cold forming performance of 180° cold bending D=3a.

A production method of HB400 high wear-resistant cold-bendable steel plate, the production process is: smelting→refining→slab continuous casting→slab heating and slow cooling→heating→controlled rolling→controlled cooling→tempering heat treatment, including the following method:

1) Smelting: RH degassing time control is carried out during refining in the present invention, and the RH vacuum cycle time is ≥15min. Through long-term vacuum treatment, molten steel [N]≤0.0030%, [O]≤0.0015%, [H]≤ 0.00015%. The characteristics of continuous casting are: appropriately increase the cooling rate of the secondary cooling zone of continuous casting, adopt the medium cooling intensity mode, the water supply of the secondary cooling zone of continuous casting accounts for 60% to 80%, and control the casting speed of the continuous casting slab to 1.1 to 1.5m/ min; the purpose is to avoid excessive precipitation of coarse carbides of niobium in the high temperature zone. The thickness of the slab is 200-250mm. Electromagnetic stirring or light pressing is used during continuous casting to reduce center segregation. The control center segregation of the present invention is less than or equal to B0.5, and the middle crack is less than or equal to 0.5 level, and the purpose is to ensure the lowest internal defects of the steel plate during cold bending. After continuous casting, the slab is heated to 550-650°C, and slowly cooled with the furnace for no less than 48 hours; it can effectively remove the hydrogen content in the slab, and at the same time, the slow cooling at about 600°C is conducive to the full analysis of fine carbides of niobium.

2) Rolling: use an oxidizing atmosphere to heat the soaking section at a temperature of 1250-1310°C, and the soaking time is not less than 2.5 hours; the purpose of higher heating temperature and longer holding time: 1) to ensure that the higher niobium can fully Solid solution; 2) It is beneficial to the homogenization of central segregation elements; 3) It is beneficial to the formation of a 1-2 mm partial decarburization layer on the surface after rolling, which can effectively improve the cold bending performance of the rolled steel plate.

The two-stage controlled rolling of rough rolling and finishing rolling is adopted in rolling, the purpose is to fully refine and homogenize the hot-rolled microstructure. In the rough rolling stage, the rolling start temperature is ≥1100°C, the final rolling temperature is controlled at ≥1050°C, and the single-pass reduction rate of rough rolling is not less than 15%; to ensure deep penetration of rolling force and to promote the precipitation of niobium carbide; The rolling start temperature is 970-1030°C, and the deformation rate is not less than 70%. The purpose is to break the coarse niobium carbide and improve the defect structure in the core. The finishing rolling temperature is 900-950°C.

Water cooling after rolling, using ultra-fast cooling + laminar flow cooling, ultra-fast cooling water temperature 870-920°C, ultra-fast cooling cooling rate ≥ 20°C/s, ultra-fast cooling final cooling temperature 600-650°C; laminar cooling rate 5 ～10℃/s, reddening temperature 200～250℃, air cooling to room temperature.

The front section adopts ultra-fast cooling, the ultra-fast cooling inlet temperature is 870-920°C, the ultra-fast cooling cooling rate is ≥20°C/s, and the ultra-fast cooling final cooling temperature is 600-650°C; it can reduce the niobium carbonitride in the crystal during slow cooling. At the same time, the refinement of austenite grains is beneficial to the plasticity, toughness and wear resistance. Laminar flow cooling is used in the rear section, the cooling rate is 5-10°C/s, the redness temperature is 200-250°C, and it is air-cooled to room temperature; the rear section is weakly cooled and controlled to cool above 200°C, which can reduce the internal stress of the steel plate and retain a small amount of residual The content of austenite ensures that the flatness of the plate is below 5mm/m and the cold bending performance.

3) Heat treatment: the tempering temperature is 200-250°C, and the tempering holding time is 8-12min/mm. The present invention adopts a tempering time higher than conventional (3-5min/mm), aiming at fully removing quenching internal stress, improving the plasticity of the steel plate, and ensuring the cold forming performance of the steel plate.

Compared with prior art, the beneficial effect of the present invention is:

The invention provides a 10-30 mm thick HB400 grade high wear-resistant cold-bendable steel plate and a production method thereof.

1. It can be produced by continuous casting;

2. The surface hardness is greater than HB400, and AKV≥40J at -40°C;

3. The wear resistance is more than 1.4 times that of the low alloy wear-resistant steel plate with the same hardness;

4. Good cold forming performance 180 ° cold bending D = 3a qualified.

Detailed ways

Below in conjunction with specific embodiment the embodiment of the present invention is further described:

According to chemical composition of the present invention and production process, the actual chemical composition of smelting the steel grade of the present invention is as Table 1, and the smelting process is shown in Table 2, and the actual rolling process parameters of the steel example of the present invention are shown in Table 3, and the controlled cooling process is shown in Table 4. The heat treatment process parameters are shown in Table 5, the physical performance test results of the present invention are shown in Table 6, and the wear resistance test results are shown in Table 7.

The smelting composition example of the steel grade of the present invention of table 1, wt%

serial number C Si mn Nb Cr Ni Al P S h 0 N Si+Ni C*Nb 1 0.14 1.5 1.0 0.12 0.35 0.40 0.040 0.009 0.0013 0.00012 0.0014 0.0030 1.90 0.00017 2 0.15 1.3 0.9 0.14 0.25 0.50 0.045 0.011 0.014 0.00014 0.0015 0.0022 1.82 0.00021 3 0.17 1.2 0.8 0.17 0.25 0.55 0.052 0.008 0.016 0.00015 0.0011 0.0025 1.75 0.00029 4 0.18 1.1 0.7 0.20 0.15 0.60 0.055 0.010 0.016 0.00008 0.0009 0.0020 1.72 0.00036

The smelting process of table 2 steel type of the present invention

The actual rolling process parameter of table 3 steel example of the present invention

The actual controlled cooling process parameter of table 4 steel example of the present invention

The heat treatment process of table 5 steel example of the present invention

The mechanical property of table 6 steel embodiment of the present invention

In the MLS-225 wet sand rubber wheel wear tester, the high wear-resistant steel plate of the present invention is compared with the ordinary NM400 steel plate. The applied pressure is 70N, the speed of the grinding wheel is 200r/min, the total number of revolutions: 2000r, and the test time is about 10 minute. The experimental results are shown in Table 7.

Table 7 Comparison of wear resistance of the embodiments of the present invention

steel type Abrasion ΔM/g Wear resistance comparison Ordinary NM400 0.06500 1.00 1-1 0.04452 1.46 1-2 0.04392 1.48 2-1 0.04483 1.45 2-2 0.04545 1.43 3-1 0.04610 1.41 3-2 0.04545 1.43 4-1 0.04483 1.45 4-2 0.04392 1.48

It can be seen that the wear resistance of the steel plate of the present invention is more than 1.4 times that of the common wear-resistant steel plate NM400.

Claims (3)

1. The HB 400-grade high-wear-resistance cold-bendable steel plate is characterized by comprising the following chemical components in percentage by weight: 0.14 to 0.18 percent of C, 1.1 to 1.50 percent of Si, 0.7 to 1.0 percent of Mn, 0.12 to 0.20 percent of Nb, 0.15 to 0.35 percent of Cr, 0.4 to 0.6 percent of Ni, 0.040 to 0.060 percent of Al, less than or equal to 0.012 percent of P, less than or equal to 0.002 percent of S, less than or equal to 0.0030 percent of [ N ], [ H ] < 0.00015 percent, and less than or equal to 0.0015 percent of [ O ]; the balance of Fe and unavoidable impurities; and C is less than or equal to 0.0004 percent, and Si+Ni is less than or equal to 1.5 percent and less than or equal to 2.0 percent;

the production method of the HB 400-grade high-wear-resistance cold-bendable steel plate comprises the following steps:

1) Smelting: RH vacuum circulation time is more than or equal to 15min, and the continuous casting blank pulling speed is controlled to be 1.1-1.5 m/min; the water supply amount of the secondary cooling zone of continuous casting accounts for 60-80%, the center segregation of the billet is less than or equal to B0.5, the middle crack is less than or equal to 0.5 level, the casting blank is heated to 550-650 ℃ after continuous casting, and the casting blank is slowly cooled along with a furnace for not less than 48 hours;

2) Rolling: heating the soaking section by adopting an oxidizing atmosphere at 1250-1310 ℃ for soaking time not less than 2.5 hours;

during rolling, rough rolling and finish rolling are adopted, the rolling start temperature in the rough rolling stage is more than or equal to 1100 ℃, the finishing temperature is more than or equal to 1050 ℃, and the single pass rolling reduction rate of rough rolling is not less than 15%; the initial rolling temperature of the finish rolling is 970-1030 ℃, the deformation rate is not lower than 70%, and the final rolling temperature of the finish rolling is 900-950 ℃;

water cooling after rolling, adopting ultra-fast cooling and laminar cooling, wherein the temperature of ultra-fast cooling water inlet is 870-920 ℃, the ultra-fast cooling speed is more than or equal to 20 ℃/s, and the final cooling temperature is 600-650 ℃; laminar cooling speed is 5-10 ℃/s, reddening temperature is 200-250 ℃, and air cooling is carried out to room temperature;

3) And (3) heat treatment: the tempering temperature is 200-250 ℃, and the tempering heat preservation time is 8-12 min/mm.

2. The HB 400-grade high-wear-resistance cold-bendable steel plate according to claim 1, wherein the retained austenite content in the steel is 5% -10%, and the thickness of the decarburized layer on the surface part of the steel plate is 1-2 mm.

3. The HB400 grade high wear-resistant cold-bendable steel plate according to claim 1, wherein the wear resistance of the steel plate reaches more than 1.4 times of that of the NM400 steel plate with the same hardness under the same experimental conditions, and the cold forming performance is 180 ° cold bending d=3a.