A low-cost, high-formability HB400 grade wear-resistant steel and its production method

Abstract

This invention discloses a low-cost, high-formability HB400 grade wear-resistant steel, the chemical composition of which, by weight percentage, is: C 0.12-0.16%, Si 0.10-0.50%, Mn 0.7-1.5%, P≤0.020%, S≤0.010%, Als 0.015-0.060%, Ti 0.12-0.20%, N 0.010-0.020%, with the remainder being Fe and unavoidable impurities; the production method adopts a process route of smelting, continuous casting, heating, rolling, coiling, uncoiling, quenching, cross-cutting, and tempering. The low-cost, high-formability HB400 grade wear-resistant steel of this invention adopts a low-alloy composition design of C-Mn-Ti-N, and utilizes the high melting point, high hardness and good thermal shock resistance of TiN particles to improve the wear resistance of the steel. It is produced by continuous heat treatment line for quenching and tempering, which improves the uniformity of the steel plate, with an elongation of up to 15% or more and excellent cold bending performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high-strength wear-resistant steel manufacturing, and particularly relates to a low-cost high-formability HB400-grade wear-resistant steel and a production method thereof. BACKGROUND

[0002] Wear-resistant steel is generally applied in metallurgy, mining, railway, power, coal and other mechanical equipment, and the demand for wear-resistant steel is increasing in downstream industries such as commercial vehicles and engineering machinery. At present, the largest demand level of high-strength wear-resistant steel is mainly in the range of HB400-HB450.

[0003] CN102605234A discloses a HB400-grade wear-resistant steel plate and a manufacturing method thereof. The chemical composition by weight percentage is: C 0.08-0.24%, Si 0.10-0.30%, Mn 0.70-1.70%, P≤0.050%, S≤0.030%, Cr≤1.00%, Mo≤0.60%, Al 0.01-0.10%, B 0.0005-0.0040%, Ti 0.005-0.06%, and satisfies 0.15≤Cr+Mo≤1.20%, 0.011%≤Al+Ti≤0.15%, the balance being Fe and unavoidable impurities. The performance is excellent by adopting the casting- controlled rolling- quenching and tempering heat treatment process, and it is suitable for manufacturing easily-worn equipment in engineering machinery, but the formability is general and the risk of bending cracking is large.

[0004] CN113637894A discloses a HB450-grade wear-resistant steel free of leveling and tempering and a production method thereof. The chemical composition by weight percentage is: C 0.12%-0.18%, Si 0.15%-0.40%, Mn 1.0%-2.0%, P≤0.015%, S≤0.005%, Als 0.01%-0.06%, Ti≤0.02%, Cr≤0.25%, B≤0.0005%, and the balance being Fe and unavoidable impurities. The production method of the HB450-grade wear-resistant steel adopts the process route of blast furnace molten iron, molten iron desulfurization, converter smelting, LF+RH refining, continuous casting, heating, rolling, cooling, coiling, open flat transverse cutting. Although the alloy content of the present application is low, it still contains Cr and other heavy metal non-environmental friendly alloys. Although the process does not need leveling and heat treatment, it requires high power of coiling equipment, which is high in equipment cost and is not conducive to popularization and production. Moreover, the plate shape quality is only controlled at 5mm / m after transverse cutting, which cannot meet the high plate shape demand of users for wear-resistant steel.

[0005] CN 116904871A discloses an HB400 grade high toughness wear-resistant steel and a production method, the components and weight percentages of which are as follows: C 0.10-0.18%, Mn 0.2-1.3%, P≤0.020%, S≤0.010%, Als 0.03-0.06%, Nb 0.010-0.020%, Ti 0.005-0.020%, Si≤0.020% or B≤0.003% or both are added in any proportion. The invention has simple components, but still contains valuable alloys such as Nb, and the grain structure is a tempered martensite structure, which has a high risk of cracking when bending, while ensuring that the product hardness HB is not less than 400, the yield strength is not less than 930 MPa, the tensile strength is not less than 1100 MPa, the elongation is not less than 10%, and the impact energy at-40℃ is not less than 50J.

[0006] In summary, the current HB400-HB450 grade wear-resistant steel generally has high valuable alloy content, low flatness of the steel plate, poor formability, and easy cracking when bending, and it is difficult to meet the various delicate processing needs of users for wear-resistant steel. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a low-cost high-formability HB400 grade wear-resistant steel and a production method thereof to solve the problems of the prior art. The low-alloy composition design of C-Mn-Ti-N is adopted, the high melting point, high hardness and good thermal shock resistance of TiN particles are used to improve the wear resistance of the steel, and the continuous heat treatment line is used for quenching and tempering production, which improves the uniformity of the steel plate, the elongation is as high as 15% or more, and the cold bending performance is excellent.

[0008] The technical scheme adopted by the present application to solve the above problems is:

[0009] A low-cost high-formability HB400 grade wear-resistant steel, the chemical composition of which is as follows in terms of weight percentage: C 0.12-0.16%, Si 0.10-0.50%, Mn 0.7-1.5%, P≤0.020%, S≤0.010%, Als 0.015-0.060%, Ti 0.12-0.20%, N 0.010-0.020%, and the rest is Fe and unavoidable impurities.

[0010] Further, the weight percentage of Si is preferably 0.15-0.42%.

[0011] Further, the weight percentage of Ti is preferably 0.123-0.191%.

[0012] Further, the weight percentage of N is preferably 0.0112-0.0188%.

[0013] The production method of the low-cost high-formability HB400 grade wear-resistant steel adopts a process route of smelting, continuous casting, heating, rolling, coiling, uncoiling, quenching, transverse cutting and tempering, wherein,

[0014] 1) smelting: blast furnace molten iron → deep desulfurization of molten iron → converter smelting → LHF refining; wherein, the LHF refining process adopts bottom blowing nitrogen, and the gas amount is 70-90 Nm 3 / h for stirring for 10-15 min; after the further desulfurization treatment of the molten steel in the LHF refining process is completed and the Ti alloy is added, the bottom blowing nitrogen amount is 10-30 Nm 3 / h for stirring for 4-7 min, and the total LHF refining treatment time is ≥30 min;

[0015] 2) rolling: the final rolling temperature FT7 is controlled at 860-900℃, and the coiling temperature CT is controlled at 580-620℃;

[0016] 3) uncoiling and quenching: the uncoiling is in a continuous state, the molten steel is quenched in a heat treatment furnace, the quenching temperature is 850-950℃, the quenching holding time is 8-15 min, after the quenching is completed, the molten steel is discharged at a high speed for cooling, the cooling speed is 50-100℃ / s, and the molten steel is cooled to a final cooling temperature of 50-100℃;

[0017] 4) transverse cutting and tempering: after the transverse cutting according to the size, the molten steel is tempered in a tempering furnace, the tempering temperature is 400-500℃, and the tempering time is 30-60 min.

[0018] Further, the quenching temperature is preferably 854-941℃, and the quenching time is preferably 8-13 min.

[0019] Further, the cooling speed after quenching is preferably 53-100℃ / s.

[0020] Further, the tempering temperature is preferably 406-498℃, and the tempering time is preferably 33-60 min.

[0021] The high-formability HB400 grade wear-resistant steel obtained by using the above chemical composition and production method has a yield strength of not less than 1000 MPa, a tensile strength of more than 1100 MPa, an elongation of 15% or more, and a cold bending performance of 180° cold bending D=4a; the finished product grain is a tempered sorbite structure with excellent strength and toughness, which is different from the tempered martensite hard phase structure of conventional wear-resistant steel.

[0022] The reasons for setting the component range and process points in the application are as follows:

[0023] C is a solid solution element, and the increase of the carbon content can increase the hardness and strength, but too high carbon content will reduce the plasticity and toughness and the welding performance; in order to avoid the peritectic reaction in the continuous casting process and reduce the risk of casting crack, the C content is preferably in the range of 0.12-0.16%.

[0024] Si is a deoxidizing element, which can promote ferrite formation and reduce the excessive formation of surface iron oxide scale in a certain content range. In consideration of the above, the weight percentage of Si is preferably 0.10-0.50%.

[0025] Mn can hinder the diffusion of carbon atoms after forming a solid solution with carbon in the steel, thereby refining the grains, effectively increasing the hardness and strength of the steel, and increasing the residual austenite content in the steel to improve the cold bending performance. In consideration of the above, the weight percentage of Mn is preferably 0.7-1.5%.

[0026] Al is a complete deoxidizing element for killed steel, and the formed AlN can also effectively refine the grains. When the content of Al is below 0.010%, the deoxidization is insufficient. In consideration of the above, the content of Al is preferably 0.015-0.060%.

[0027] Ti can combine with N element to form TiN during solidification, which is pinned at the grain boundary of austenite, thereby hindering the growth of austenite grains and refining the austenite grains. Moreover, the melting point of TiN particles is as high as 2930°C, and the hardness is close to natural diamond, which can provide high wear resistance for the steel. In addition, the strengthening effect of a certain amount of Ti element solid-solved in ferrite is also higher than that of Al, Mn, Ni, Mo, etc. In consideration of the above, the weight percentage of Ti is preferably 0.12-0.20%.

[0028] N is a very strong austenite-forming and stabilizing element, which is about 20 times as effective as nickel, has solid solution strengthening effect, and can improve the hardenability of the steel. However, too high content of N will lead to loose macrostructure or pores. Therefore, the addition amount of N in the present application is 0.010-0.020%.

[0029] P and S are harmful impurity elements in steel, which can reduce the toughness and welding performance of the steel, and produce delamination defects. Therefore, the lower the content of P and S, the better. In consideration of the above, P≤0.020% and S≤0.010%.

[0030] The reason why the bottom blowing nitrogen is used in the LHF refining treatment in the present application is that the gas amount is 70-90 Nm 3 / h for stirring for 10-15 min. After the desulfurization treatment of the molten steel is completed, the bottom blowing nitrogen gas amount is 10-30 Nm 3 / h for stirring for 5 min, and the total treatment time of LHF is ≥30 min, so as to make the increase of N content in the steel reach the expected range and ensure that the Ti content reaches the target value, thereby avoiding being oxidized below the lower limit.

[0031] The present application controls the final rolling temperature FT7 at 860-900 DEG C and the coiling temperature CT at 580 DEG C-620 DEG C, so as to reduce the rolling load, ensure the uniform plastic deformation, and fully exert the precipitation and solid solution strengthening effect of Ti element.

[0032] The present application enters the continuous state into the heat treatment furnace quenching, the quenching temperature is 850-950 DEG C, the quenching holding time is 8-15 minutes, after the quenching is completed, the furnace is discharged and high speed cooling is carried out, the cooling speed is 50-100 DEG C / s, and the cooling is to 50-100 DEG C, so as to improve the quenching production efficiency in the continuous heat treatment furnace production, reduce the production process cost, and obtain the martensite hard structure.

[0033] The present application enters the tempering furnace tempering after the fixed size transverse cutting, the tempering temperature is 400-500 DEG C, and the tempering time is 30-60 min, so as to uniformly eliminate the internal stress of the material in the flat state of the steel plate, and obtain the excellent tempering sorbite structure.

[0034] Compared with the prior art, the present application has the beneficial effects that:

[0035] 1. The low-cost high-formability HB400 grade wear-resistant steel provided by the present application adopts the low-alloy component design of C-Mn-Ti-N, utilizes the characteristics of high melting point, high hardness and good thermal shock resistance of TiN particles to improve the wear resistance of the steel, and adopts the continuous heat treatment line quenching and tempering production, so as to improve the uniformity of the steel plate.

[0036] 2. The low-cost high-formability HB400 grade wear-resistant steel prepared by the present application has excellent performance, the heat treatment (i.e. tempering) adopts the medium-high temperature quenching and tempering process, the finished product grain is the excellent tempering sorbite structure, which is different from the tempered martensite hard phase structure of the conventional wear-resistant steel, the elongation is as high as 15% or more, and the 180 DEG cold bending D=4a is qualified.

[0037] 3. The present application does not contain any valuable metal content such as Cu, Ni, Cr, Mo, Nb and V, the alloy production cost is low, the HB400 grade wear-resistant steel product with low carbon content, easy welding and cold bending forming is realized. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The present application provides a metallographic structure diagram of a low-cost high-formability HB400 grade wear-resistant steel. DETAILED DESCRIPTION

[0039] In order to better understand the present application, the content of the present application will be further illustrated below in combination with examples, but the present application is not limited to the following examples.

[0040] EXAMPLE

[0041] The examples will be described in detail below:

[0042] Embodiments 1-10 each provide a low-cost high-formability HB400 grade wear-resistant steel, each chemical component and its weight percentage being shown in Table 1, the rest being Fe and inevitable impurities; Comparative Examples 1-2 are conventional wear-resistant steels, each chemical component and its weight percentage being shown.

[0043] The specific process parameters of the production process in Embodiments 1-10 and Comparative Examples 1-2 are shown in Table 2.

[0044] Each embodiment of the present application produces a low-cost high-formability HB400 grade wear-resistant steel according to the following steps, using a process route of smelting, continuous casting, heating, rolling, coiling, uncoiling, quenching, cross-cutting, and tempering, each process step being as follows:

[0045] 1) Smelting: high-temperature molten iron → deep desulfurization of molten iron → converter smelting → LHF refining; the LHF refining process needs to use bottom-blown N2, with a gas flow of 70-90 Nm 3 / h for 10-15 min; after adding Ti alloy after the molten steel desulfurization process is completed, the bottom-blown N2 gas flow is 10-30 Nm 3 / h for 5 min, and the total LHF processing time is ≥30 min;

[0046] 2) Continuous casting and heating: after casting into a billet, the billet is heated: the billet heating uses a three-stage heating system, i.e., a first heating stage, a second heating stage, and a soaking stage, wherein the heating temperature of the second heating stage and the soaking stage is controlled to be 1230-1270℃, the soaking time is ≥70 min, and the total in-furnace time is ≥150 min;

[0047] 3) Rolling and coiling: F1-F7 finishing rolling mill is used for rolling, the final rolling temperature FT7 is controlled to be in the range of 860-900℃, then laminar flow cooling is used to cool to a coiling temperature CT of 580-620℃ at a cooling rate of 10-30℃ / s, and then coiling is performed;

[0048] 5) Uncoiling and quenching: uncoiling is performed in a continuous state, and then the billet is put into a heat treatment furnace for quenching, the quenching temperature is 850-950℃, the quenching holding time is 8-15 min, after quenching is completed, the billet is taken out of the furnace for high-speed cooling at a cooling rate of 50-100℃ / s, and then cooled to 50-100℃;

[0049] 6) Cross-cutting and tempering: after cross-cutting according to the size, the billet is put into a tempering furnace for tempering, the tempering temperature is 400-500℃, and the tempering time is 30-60 min;

[0050] The low-cost high-formability HB400 grade wear-resistant steel is finally obtained through the above steps.

[0051] The production process of the comparative examples is performed according to the embodiments, and the specific component values and process parameter values are shown in Tables 1 and 2.

[0052] Table 1

[0053] C / ％ Si / % Mn / % P / ％ S / ％ Als / % B / ％ N / ％ Ti / % Example 1 0.13 0.18 0.96 0.015 0.005 0.020 / 0.0188 0.151 Example 2 0.14 0.20 0.88 0.013 0.009 0.015 / 0.0149 0.133 Example 3 0.16 0.15 0.76 0.011 0.002 0.050 / 0.0135 0.142 Example 4 0.15 0.40 0.95 0.012 0.003 0.042 / 0.0162 0.131 Example 5 0.12 0.38 1.22 0.015 0.006 0.030 / 0.0151 0.191 Example 6 0.15 0.31 1.17 0.005 0.010 0.040 / 0.0133 0.185 Example 7 0.13 0.21 1.29 0.018 0.009 0.051 / 0.0126 0.157 Example 8 0.12 0.19 1.50 0.011 0.005 0.058 / 0.0151 0.123 Example 9 0.16 0.22 1.23 0.006 0.009 0.042 / 0.0112 0.183 Example 10 0.14 0.42 0.98 0.014 0.006 0.041 / 0.0138 0.178 Comparative Example 1 0.18 0.31 1.42 0.012 0.003 0.031 0.0005 0.0035 0.022 Comparative Example 2 0.21 0.22 1.21 0.011 0.004 0.023 0.0006 0.0046 0.021

[0054] Table 2

[0055]

[0056] The performance of the low-cost high-formability HB400 grade wear-resistant steel of Examples 1-10 and Comparative Examples 1-2 is shown in Table 3. The yield strength (MPa), tensile strength (MPa), and elongation A are tested according to the national standard GB / T228, and the cold bending performance is tested according to the national standard GB / T232.

[0057] Table 3

[0058]

[0059] In summary, the low-cost high-formability HB400 grade wear-resistant steel provided by the present application has a yield strength of not less than 1000 MPa, a tensile strength of more than 1100 MPa, an elongation of 15% or more, and a cold bending performance of 180° cold bending D=4a. Compared with Comparative Examples 1 and 2, the elongation and cold bending performance of the examples are higher than those of the conventional wear-resistant steel of the same grade.

[0060] The above examples are merely illustrative for the sake of clarity and are in no way limiting on the embodiments. Other variations to those from the above will be obvious to those with ordinary skill in the art and the principal of the application is the patent to be protected.

Claims

1. A low cost high formability HB400 grade wear resistant steel, characterized in that, The chemical composition is as follows in percentage by weight: C 0.12-0.16%, Si 0.10-0.50%, Mn 0.7-1.5%, P≤0.020%, S≤0.010%, Als 0.015-0.060%, Ti 0.12-0.20%, N 0.010-0.020%, and the balance of Fe and inevitable impurities; The production method of the low-cost high-formability HB400-grade wear-resistant steel comprises the process routes of smelting, continuous casting, heating, rolling, coiling, uncoiling, quenching, cross cutting and tempering; wherein, 1) Smelting: hot metal desulphurization → converter smelting → LHF refining; wherein, the LHF refining process adopts bottom blowing nitrogen, and the gas quantity is 70-90 Nm 3 / h for 10-15 min; after the further desulphurization treatment of the molten steel in the LHF refining treatment process is completed and the Ti alloy is added, the bottom blowing nitrogen gas quantity is 10-30 Nm 3 / h for 4-7 min, and the total treatment time of the LHF refining is ≥30 min; 2) rolling: F1-F7 finishing rolling mill is adopted, the finish rolling temperature FT7 is controlled in the range of 860-900 DEG C, and the coiling temperature CT is controlled in the range of 582-620 DEG C; 3) uncoiling and quenching: the uncoiling is in a continuous state, and then the uncoiled steel is quenched in a heat treatment furnace, the quenching temperature is 850-950 DEG C, the quenching holding time is 8-15 min, after the quenching is completed, the quenched steel is discharged from the heat treatment furnace and cooled at a high speed, the cooling speed is 50-100 DEG C / s, and the steel is cooled to a final cooling temperature of 50-100 DEG C; 4) cross cutting and tempering: after the cross cutting according to the length, the cross cut steel is tempered in a tempering furnace, the tempering temperature is 400-500 DEG C, and the tempering time is 30-60 min, so that the low-cost high-formability HB400-grade wear-resistant steel is obtained, the yield strength of the steel is not less than 1000 MPa, the tensile strength of the steel is more than 1100 MPa, the elongation of the steel is more than 15%, the cold bending performance of the steel meets the requirement of 180 DEG cold bending D=4a, and the grain of the wear-resistant steel is tempered sorbite.

2. A low cost high formability HB400 grade wear resistant steel according to claim 1, characterized in that, The weight percentage of Si is 0.15-0.42%.

3. A low cost high formability HB400 grade wear resistant steel according to claim 1, characterized in that, The weight percentage of Ti is 0.123-0.191%.

4. A low cost high formability HB400 grade wear resistant steel according to claim 1, characterized in that, The weight percentage of N is 0.0112-0.0188%.

5. The production method of the low-cost high-formability HB400-grade wear-resistant steel according to claim 1, which comprises the process routes of smelting, continuous casting, heating, rolling, coiling, uncoiling, quenching, cross cutting and tempering; characterized in that, 1) Smelting: hot metal desulphurization → converter smelting → LHF refining; wherein, the LHF refining process adopts bottom blowing nitrogen, and the gas quantity is 70-90 Nm 3 / h for 10-15 min; after the further desulphurization treatment of the molten steel in the LHF refining treatment process is completed and the Ti alloy is added, the bottom blowing nitrogen gas quantity is 10-30 Nm 3 / h for 4-7 min, and the total treatment time of the LHF refining is ≥30 min; 2) rolling: F1-F7 finishing rolling mill is adopted, the finish rolling temperature FT7 is controlled in the range of 860-900 DEG C, and the coiling temperature CT is controlled in the range of 582-620 DEG C; 3) uncoiling and quenching: the uncoiling is in a continuous state, and then the uncoiled steel is quenched in a heat treatment furnace, the quenching temperature is 850-950 DEG C, the quenching holding time is 8-15 min, after the quenching is completed, the quenched steel is discharged from the heat treatment furnace and cooled at a high speed, the cooling speed is 50-100 DEG C / s, and the steel is cooled to a final cooling temperature of 50-100 DEG C; 4) cross cutting and tempering: after the cross cutting according to the length, the cross cut steel is tempered in a tempering furnace, the tempering temperature is 400-500 DEG C, and the tempering time is 30-60 min.

6. The method of producing a low-cost, high-formability HB400 grade abrasion-resistant steel according to claim 5, characterized in that, The quenching temperature is 854-941 DEG C, and the quenching time is 8-13 min.

7. The method of producing a low-cost, high-formability HB400 grade wear-resistant steel according to claim 5, characterized in that, The cooling speed after the quenching is 53-100 DEG C / s.

8. The method of producing a low-cost, high-formability HB400 grade abrasion-resistant steel according to claim 5, characterized in that, The tempering temperature is 406-498 DEG C, and the tempering time is 33-60 min.

9. Low cost high formability HB400 grade wear resistant steel produced by the method of any one of claims 5 to 8, characterized in that, The yield strength of the wear-resistant steel is not less than 1000 MPa, the tensile strength of the steel is more than 1100 MPa, the elongation of the steel is more than 15%, the cold bending performance of the steel meets the requirement of 180 DEG cold bending D=4a, and the grain of the wear-resistant steel is tempered sorbite.

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