HB450 grade wear-resistant steel produced by CSP and method thereof

Abstract

A HB450 grade wear-resistant steel produced using CSP has the following components and weight percentages: C: 0.20-0.28%, Mn: 0.1-0.9%, P≤0.020%, S≤0.010%, Als: 0.03-0.06%, and Ti: 0.005-0.01%. The production method includes conventional smelting and casting into billets; heating the billets; hot rolling; laminar cooling; coiling; continuous uncoiling and quenching; high-speed cooling; cross-cutting to a specified length and tempering; and natural cooling to room temperature. The present invention achieves a simple composition, a product thickness of 1.2-2.5 mm, a plate shape of less than 5 mm / m, and a reduction in overall production costs of at least 1%, all while ensuring a product hardness of no less than 420, a yield strength of no less than 1150 MPa, a tensile strength of no less than 1310 MPa, and an elongation of no less than 9%.

Description

Technical Field

[0001] The present invention relates to wear-resistant steel for mechanical engineering and a production method thereof, in particular to HB450 grade wear-resistant steel produced by CSP and a production method thereof. Background Art

[0002] Heat-treated steel is widely used in machinery and equipment for metallurgy, mining, building materials, railways, electric power, coal, and other industries. The common process for thin-gauge heat-treated steel is hot continuous rolling / plate production line rolling followed by heat treatment. This involves a lengthy manufacturing process, and there is no precedent for using CSP production lines to roll baseplates. While thinner gauges offer higher added value, thinner gauges are less efficient, making it more difficult to maintain stable control of the original coil's flatness and mechanical properties. Furthermore, to maintain flatness, the coiling temperature of thin-gauge wear-resistant steel is forced to increase, inevitably increasing the size of the original austenite grains, impacting performance and increasing the risk of cracking during welding or service.

[0003] The CSP process can improve production efficiency, reduce energy consumption, and has unique advantages in producing thin specifications, especially for thin specifications such as 2mm. No domestic manufacturer has the stable supply capacity of 2mm.

[0004] To ensure a consistent balance of strength, toughness, and hardness, and to improve welding performance in downstream applications, existing technologies originally designed wear-resistant steels to have a carbon content of 0.06-0.20%, covering the peritectic zone. However, for CSP, peritectic steel experiences significant volume shrinkage and a greater tendency to thermal cracking during casting. Thin slab continuous casting machines also require high cooling intensity and utilize a funnel-shaped mold, which increases the resistance of the slab shell and increases the risk of cracking during peritectic steel production.

[0005] After searching:

[0006] The document with Chinese patent publication number CN1109919A discloses "A low-alloy wear-resistant steel", whose components by weight are: C: 0.5-0.6%, Si: 0.9-1.2%, Mn: 1.4-1.7%, Cr: 1.35-1.60%, Mo: 0.3-0.5%, V: 0.05-0.10%, Ti: 0.03-0.06%, Re: 0.02-0.04%. It has good strength and wear resistance. The C content is as high as 0.5-0.6%. At the same time, a large amount of alloy elements that improve hardenability are added. Not only is the cost high, but it is also produced using a traditional two-stage hot rolling production line.

[0007] As can be seen, existing wear-resistant steels face technical challenges such as lengthy production processes and low efficiency. Therefore, it is necessary to redesign the composition and process to improve production efficiency. The engineering machinery industry consumes a large amount of high-strength steel, such as excavator bucket liners and side panels, and mining vehicle compartment liners. However, thin-gauge products are currently produced using hot rolling lines or even cold rolling, which results in low pass rates, lengthy processes, and high energy consumption. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings of the existing technology and provide a HB450 grade wear-resistant steel produced by CSP and a method thereof, which ensures that the product hardness HB is not less than 420, the yield strength is not less than 1150 MPa, the tensile strength is not less than 1310 MPa, and the elongation is not less than 9%. The components are simple, the product thickness is 2±0.5 mm, the plate shape is less than 2 to 4 mm / m, and the overall production cost can be reduced by at least 1%.

[0009] Measures to achieve the above objectives:

[0010] The invention discloses a HB450 grade wear-resistant steel produced by CSP, wherein the components and weight percentages thereof are as follows: C: 0.20-0.28%, Mn: 0.1-0.9%, P≤0.020%, S≤0.010%, Als: 0.03-0.06%, Ti: 0.005-0.01%, and the remainder is Fe and impurities.

[0011] Preferably, the weight percentage of Mn is 0.18-0.76%.

[0012] Preferably, the weight percentage content of Ti is 0.007-0.0086%.

[0013] Furthermore, the weight percentage of added Si is not more than 0.20%.

[0014] Furthermore, the weight percentage of added Cr is not more than 0.10%.

[0015] A method for producing HB450 grade wear-resistant steel using CSP, comprising the following steps:

[0016] 1) Conventional smelting and casting into billets, controlling the billet thickness to 40-80 mm;

[0017] 2) heating the ingot and controlling the heating temperature between 1160 and 1200°C;

[0018] 3) hot rolling, controlling the final rolling temperature at 880-930°C;

[0019] 4) laminar cooling is performed at a cooling rate of 5 to 10°C / s to the coiling temperature;

[0020] 5) Coil the steel sheet and control the coiling temperature between 600 and 680°C.

[0021] 6) Continuously unwind and quench, control the quenching temperature at 820-900°C, and control the quenching time at 5-10 minutes;

[0022] 7) High-speed cooling is performed, cooling to room temperature at a cooling rate of 80 to 110°C / s;

[0023] 8) After cutting to a fixed length, temper the steel. Control the tempering temperature at 150-220°C and the tempering time at 10-30 minutes.

[0024] 9) Cool naturally to room temperature.

[0025] Preferably, the coiling temperature is between 608 and 665°C.

[0026] Preferably, the quenching temperature is between 836°C and 887°C.

[0027] Preferably, the tempering temperature is between 155° C. and 208° C., and the tempering time is between 16 and 25 minutes.

[0028] Functions and mechanisms of each element and main process in the present invention

[0029] C: C is the cheapest element for increasing material strength. However, if the carbon content is below 0.20%, it can cause peritectic reactions in the molten steel during casting, increasing the risk of breakout during continuous casting. While increasing the carbon content improves hardness and strength, it also reduces plasticity, toughness, and weldability. Therefore, considering all factors, a C content of 0.20-0.28% by weight is recommended.

[0030] Si: Si can reduce the diffusion rate of carbon in ferrite and promote ferrite formation, but it can also deteriorate the surface quality. Taking all factors into consideration, it is best to control the Si content to no more than 0.2% by weight.

[0031] Mn: Mn significantly reduces the Ar1 temperature and the rate of austenite decomposition, improves the stability of supercooled austenite, promotes stress release in austenite, increases the residual austenite content in the final structure, and improves cold bending properties. However, if the Mn content is too high, it will increase temper brittleness and lead to severe center segregation. Taking all factors into consideration, the appropriate Mn content is 0.1-0.9% by weight.

[0032] Als: Als can deoxidize steel, reduce the inclusion content, and also play a role in refining grains. Taking all factors into consideration, Als is between 0.03 and 0.06%.

[0033] Ti: During the solidification process of steel, Ti combines with nitrogen to form stable TiN, which strongly hinders the migration of austenite grain boundaries, thereby refining the austenite grains. Taking all factors into consideration, the appropriate Ti content is 0.005-0.01% by weight.

[0034] Cr: Cr can improve hardenability, improve tempering stability, and reduce the cooling rate to obtain martensite. However, too high Cr content reduces workability and weldability. Taking all factors into consideration, it is best to control the Cr weight percentage to no more than 0.1%.

[0035] P and S: P and S are harmful impurity elements in steel. P in steel is easy to form segregation in the steel, reducing the toughness and welding performance of the steel. S is easy to form plastic sulfide, causing stratification of the steel plate and deteriorating the performance of the steel plate. Therefore, the lower the P and S content, the better. Taking comprehensive considerations, the P and S contents of steel are controlled at P≤0.020% and S≤0.010% respectively.

[0036] The reason why the present invention controls the coiling temperature at 600-680°C is that the steel coil is relatively thin. When the coiling temperature is lower than 600°C, it is difficult to resist thermal stress, which will deteriorate the shape of the steel plate and the coil. When the coiling temperature is higher than 680°C, the cooling rate in the cooling stage is insufficient, the austenite grains are coarse, and the performance of the finished product is also adversely affected.

[0037] The reason why the present invention controls the quenching temperature at 820-900°C and the quenching time at 5-10 minutes is that when the quenching temperature is lower than 820°C, the steel plate cannot be completely austenitized, and a mixed crystal structure will appear on the steel plate, affecting the uniformity of the structure and performance of the finished steel plate. When the quenching temperature is higher than 900°C, the original austenite grains are coarse, and after transforming into martensite, the plate size is large and the toughness is seriously affected.

[0038] The reason why the present invention controls the tempering temperature at 150-220°C and the tempering time at 10-30 minutes is that when the tempering temperature is lower than 150°C, the tempering effect is poor and the ability to improve the plate shape and internal stress is weak. When the tempering temperature is higher than 220°C, the supersaturated carbon in the martensite is easily precipitated, the solid solubility decreases, the strength and hardness are greatly affected, and the risk of performance mismatch is greater.

[0039] Compared with the prior art, the present invention has the advantages of simple components, product thickness of 1.2 to 2.5 mm, plate shape of less than 5 mm / m, and comprehensive production cost reduced by at least 1% while ensuring that the product hardness HB is not less than 420, the yield strength is not less than 1150 MPa, the tensile strength is not less than 1310 MPa, and the elongation is not less than 9%. DETAILED DESCRIPTION

[0040] The present invention is described in detail below:

[0041] Table 1 is a list of chemical compositions of various embodiments and comparative examples of the present invention;

[0042] Table 2 is a list of main process parameters of various embodiments and comparative examples of the present invention;

[0043] Table 3 is a table of performance test results of various embodiments of the present invention and comparative examples.

[0044] Each embodiment of the present invention is produced according to the following steps

[0045] 1) Conventional smelting and casting into billets, controlling the billet thickness to 40-80 mm;

[0046] 2) heating the ingot and controlling the heating temperature between 1160 and 1200°C;

[0047] 3) hot rolling, controlling the final rolling temperature at 880-930°C;

[0048] 4) laminar cooling is performed at a cooling rate of 5 to 10°C / s to the coiling temperature;

[0049] 5) Coil the steel sheet and control the coiling temperature between 600 and 680°C.

[0050] 6) Continuously unwind and quench, control the quenching temperature at 820-900°C, and control the quenching time at 5-10 minutes;

[0051] 7) High-speed cooling is performed, cooling to room temperature at a cooling rate of 80 to 110°C / s;

[0052] 8) After cutting to a fixed length, temper the steel. Control the tempering temperature at 150-220°C and the tempering time at 10-30 minutes.

[0053] 9) Cool naturally to room temperature.

[0054] Table 1 Chemical composition list of various embodiments of the present invention and comparative examples (wt%)

[0055]

[0056] Table 2 List of main process parameters of various embodiments of the present invention and comparative examples

[0057]

[0058]

[0059] Table 3 Mechanical properties test results of various embodiments of the present invention and comparative examples

[0060]

[0061] As can be seen from Table 3, the product described in this patent is produced using a CSP production line, with a thickness specification of 1.2 to 2.5 mm, a strength level reaching NM450, and a finished product plate shape reaching 2 to 4 mm / m. Compared with the comparative example, this patent has a better plate shape with a thinner thickness.

[0062] This specific implementation is only the best example and is not a restrictive implementation of the technical solution of the present invention.

Claims

1. A HB450 grade wear-resistant steel produced by CSP, wherein the composition and weight percentage are as follows: C: 0.20-0.28%, Mn: 0.1-0.33%, P≤0.020%, S≤0.010%, Als: 0.03-0.06%, Ti: 0.005-0.01%, Si: 0.01% or Si: 0.09-0.14%, and the remainder is Fe and impurities; the product thickness is 2±0.5 mm, and the plate shape reaches 2-4 mm / m; Production method: 1) Conventional smelting and casting into billets, controlling the billet thickness to 40~80mm; 2) Heat the ingot and control the heating temperature between 1160~1200℃; 3) Perform hot rolling and control the final rolling temperature at 905~930℃; 4) Perform laminar cooling at a cooling rate of 5-9°C / s to the coiling temperature; 5) Coil the steel sheet and control the coiling temperature between 600 and 680°C. 6) Continuously unwind and quench, control the quenching temperature at 820~837℃, and control the quenching time at 5~10 minutes; 7) Perform high-speed cooling and cool to room temperature at a cooling rate of 80~110℃ / s; 8) After cutting to the specified length, temper the steel. Control the tempering temperature between 150 and 220°C and the tempering time between 10 and 30 minutes. 9) Allow to cool naturally to room temperature.

2. The HB450 grade wear-resistant steel produced by CSP according to claim 1, characterized in that: The weight percentage of added Cr is not more than 0.09%.

3. The method for producing HB450 grade wear-resistant steel using CSP as claimed in claim 1, comprising the following steps: 1) Conventional smelting and casting into billets, controlling the billet thickness to 40~80mm; 2) Heat the ingot and control the heating temperature between 1160~1200℃; 3) Perform hot rolling and control the final rolling temperature at 905~930℃; 4) Perform laminar cooling at a cooling rate of 5-9°C / s to the coiling temperature; 5) Coil the steel sheet and control the coiling temperature between 600 and 680°C. 6) Continuously unwind and quench, control the quenching temperature at 820~837℃, and control the quenching time at 5~10 minutes; 7) Perform high-speed cooling and cool to room temperature at a cooling rate of 80~110℃ / s; 8) After cutting to the specified length, temper the steel. Control the tempering temperature between 150 and 220°C and the tempering time between 10 and 30 minutes. 9) Allow to cool naturally to room temperature.

Images