High-strength medium-thin gauge wear-resistant steel plate nm600 and production method thereof

Abstract

The application discloses a high-strength medium-thin-specification wear-resistant steel plate NM600 and a production method thereof, and belongs to the field of metallurgy, alloy or non-ferrous metal processing. The chemical components of the steel plate and mass percentage are as follows: C: 0.35-0.4%, Si: 0.4-0.75%, Mn: 1.0-1.80%, Cr: 0.9-1.1%, Mo: 0.5-0.7%, Nb: <=0.0255, P: <=0.020%, S: <=0.010%, Als: >=0.010%, B: 0.0005-0.0060%, and the balance is Fe and inevitable impurities. The thickness of the steel plate is 2.0mm-12.0mm, and the width is 1500mm-2000mm. The reasonable design of C, Mn and Cr can effectively reduce the content of valuable alloy Ni and Mo without reducing the mechanical properties, so that the cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of metallurgy, alloy or non-ferrous metal processing, and specifically to a thin high-strength wear-resistant steel plate NM600 and its production method. Background Technology

[0002] Wear-resistant steel, as a crucial steel material, is widely used in various fields such as engineering machinery, mining machinery, and coal mining and transportation due to its comprehensive properties, including high strength, high hardness, easy formability, and excellent weldability. With the sustained and rapid development of my country's economy, the demand for wear-resistant steel is also showing a steady upward trend.

[0003] Currently, high-strength steel, wear-resistant steel, and aluminum have become mainstream materials in the market, with an emphasis on applying the right material to the right location to achieve optimal results. Against this backdrop, wear-resistant steel, due to its superior performance, is primarily used in key structural components such as the bodies of heavy-duty mining trucks and road dump trucks, as well as the beams and booms of semi-trailers. Compared to general structural steel, wear-resistant steel not only has higher wear resistance and strength but also allows for thinner and lighter vehicle bodies, thereby further improving overall performance and efficiency.

[0004] However, the wear-resistant steel market is currently dominated by international brands such as Hardox, EVERHARD, and XAR. Domestic wear-resistant steel plate designs mostly follow the GB / T 24186—2009 standard, "High-strength Wear-resistant Steel for Engineering Machinery," but there is still a lack of customized product development for different application fields, resulting in a gap compared to foreign brands. Furthermore, current wear-resistant steels use expensive alloying elements such as Ni and Mo to improve wear resistance, leading to higher costs. Therefore, this invention provides a high-strength, medium-thin wear-resistant steel plate, NM600, and its production method, suitable for wear-resistant steel used in dump truck bodies, while reducing costs. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a high-strength, medium-thin wear-resistant steel plate (NM600) and its production method, with a thickness of 2.0mm–12mm and a width of 1500mm–2000mm. This invention controls the mechanical properties of the wear-resistant steel by adding alloying elements and adjusting their content. Through rational design of C, Mn, and Cr, the content of expensive alloying elements such as Ni and Mo can be effectively reduced without compromising mechanical properties, thus achieving cost reduction.

[0006] A high-strength, medium-thin wear-resistant steel plate, NM600, has the following chemical composition and mass percentage: C: 0.35-0.4%, Si: 0.4-0.75%, Mn: 1.0-1.80%, Cr: 0.9-1.1%, Mo: 0.5-0.7%, Nb: ≤0.0255%, P: ≤0.020%, S: ≤0.010%, Als: ≥0.010%, B: 0.0005-0.0060%, with the balance being Fe and unavoidable impurities.

[0007] Furthermore, the thickness of the steel plate is 2.0mm to 12.0mm, and the width is 1500mm to 2000mm.

[0008] Furthermore, the microstructure of the steel plate is lath martensite.

[0009] Furthermore, the steel plate has a lower yield strength ReL ≥ 1200 MPa, a tensile strength Rm ≥ 1400 MPa, an elongation after fracture A ≥ 8%, and a surface Brinell hardness ≥ 580 HBW.

[0010] The production method of the above-mentioned high-strength, medium-thin wear-resistant steel plate NM600 includes the following steps:

[0011] (I) Steelmaking

[0012] (1) Refining: Steel is produced using the LF single-path method.

[0013] Furthermore, after refining, calcium treatment is performed, and the soft argon blowing time after calcium treatment is ≥15min to improve the flotation of inclusions.

[0014] (2) Continuous casting: Molten steel is continuously cast into billets; wherein, the superheat is ≤25℃, and the lower superheat of the molten steel can reduce the columnar crystal ratio during the solidification process of the molten steel. The constant casting speed is controlled at 1.0~1.1m / min. Stable casting speed control is conducive to accurate billet reduction and the generation of equiaxed crystals, and reduces billet segregation.

[0015] Furthermore, a new type of carbon-free slag is used in the tundish slag of the continuous casting process. The carbon-free slag has the following composition: SiO2 < 6 wt%, Al2O3 > 20 wt%, and basicity ≥ 5, in order to improve the adsorption capacity of inclusions during the casting process.

[0016] Furthermore, the water distribution for the continuous casting process is achieved through pipeline water distribution.

[0017] Furthermore, in the continuous casting process, the light reduction of the billet in the sector section of the continuous casting machine mainly occurs in sections 6 to 8, with a reduction amount of 2 to 4%. The stable reduction position and amount can effectively reduce the fluidity of the molten steel during solidification and reduce segregation during the solidification process of the billet.

[0018] Furthermore, the thickness of the cast billet is 230–240 mm.

[0019] Furthermore, the equiaxed crystal content of the continuously cast billet should be ≥40%, and the low magnification requirement for the billet should be <1.0.

[0020] (II) Rolling

[0021] (1) Heating: The billet enters the heating furnace for heating, and the furnace exit temperature is 1190~1250℃, and the furnace time is 150~210min.

[0022] (2) Hot rolling: The heated billet is hot rolled, which includes rough rolling and finish rolling. After finish rolling, it is cooled and coiled to obtain steel plate. Among them, the rough rolling adopts the 3+5 mode, the rough rolling exit temperature is 1050~1080℃, the finish rolling final rolling temperature is 875~905℃, and the coiling temperature is 665~695℃.

[0023] Furthermore, intermittent cooling is employed. The cooling water temperature fluctuates between 20 and 35°C, and the strip steel is cooled to 665–695°C at a cooling rate of 5–40°C / s.

[0024] Furthermore, the thickness of the intermediate billet after rough rolling is 35–60 mm.

[0025] Furthermore, the total reduction rate in rough rolling is 80-85%.

[0026] Furthermore, the finishing rolling temperature is 1020–1080℃.

[0027] III. Slow Cooling

[0028] The coiled steel plates are stacked in the hot zone of the warehouse at a temperature of 200-400℃ for slow cooling, which takes 36-48 hours.

[0029] IV. Heat Treatment

[0030] The steel plate is first quenched and then tempered using a quenching and tempering process. The quenching temperature is 870-920℃ and the holding time is 60-90 minutes. In order to reduce quenching stress and improve the flatness of the plate, a low-temperature tempering process is adopted, with a heating temperature of 150-220℃ and a holding time of 30-90 minutes.

[0031] Furthermore, quenching is performed using a quenching furnace with a heating rate of 35-75℃ / min.

[0032] Furthermore, the quenched steel plate is water-cooled, then tempered, and finally air-cooled to room temperature.

[0033] The beneficial effects of this invention are:

[0034] (1) The mechanical properties of wear-resistant steel can be controlled by adding alloying elements and adjusting their content. A reasonable design of C, Mn, and Cr can effectively reduce the content of expensive alloys such as Ni and Mo without reducing mechanical properties, thereby reducing costs.

[0035] (2) In the steelmaking process, the continuous casting adopts constant casting speed control and other methods to reduce billet defects, and the rolling process adopts controlled rolling and cooling process and heat treatment process to ensure the performance stability of high-strength wear-resistant steel. Attached Figure Description

[0036] Figure 1 The metallographic structure of the steel plate prepared in Example 1.

[0037] Figure 2 The metallographic structure of the steel plate prepared in Example 2. Detailed Implementation

[0038] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0039] Example 1

[0040] A high-strength, medium-thin wear-resistant steel plate, NM600, wherein the alloy composition of the hot-rolled strip steel is shown in Table 1, with the balance being Fe and unavoidable impurities.

[0041] Table 1 Chemical composition / %

[0042] Specifications / mm C Si Mn Cr Mo Nb P S Als B 3*1500 0.35 0.55 1.6 1.0 0.55 0.02 0.009 0.001 0.024 0.0015

[0043] The continuous casting superheat was 11℃, and the casting speed was 1.0 m / min. The hot rolling process involved 182 min in the furnace, an exit temperature of 1210℃, and a roughing mill exit temperature of 1060℃. R1 roughing mill had 3 passes, and R2 roughing mill had 5 passes. The intermediate slab thickness after roughing was 35.63 mm, and the total roughing reduction was 84.5%. The finishing mill's initial rolling temperature was 1020℃. The final rolling temperature was 900℃, and the coiling temperature was 680℃. Intermittent cooling was used, with cooling water at 25℃, and the strip was cooled to 680℃ at a rate of 26℃ / s. The coiled steel plates were then stacked in a 300℃ hot zone for slow cooling for 48 hours.

[0044] The quenching furnace has a heating rate of 50℃ / min, a quenching temperature of 900℃, and a holding time of 60min. After the steel plate is taken out of the furnace, it is water-cooled. In order to reduce quenching stress and improve the flatness of the plate, a low-temperature tempering process is adopted, with a heating temperature of 180℃ and a holding time of 60min, followed by air cooling to room temperature.

[0045] The properties of the steel plate prepared in this embodiment are shown in Table 2:

[0046] Table 2 Performance Requirements

[0047]

[0048] Observing the microstructure of heat-treated NM600 grade wear-resistant steel, its thickness section shows a uniform lath martensite structure, such as... Figure 1 As shown.

[0049] Example 2

[0050] A high-strength, medium-thin wear-resistant steel plate, NM600, wherein the alloy composition of the hot-rolled strip steel is shown in Table 3, with the balance being Fe and unavoidable impurities.

[0051] Table 3 Chemical composition / %

[0052]

[0053] The continuous casting superheat was 19℃, and the casting speed was 1.1 m / min. The hot rolling process involved 201 min in the furnace, an exit temperature of 1195℃, and a roughing mill exit temperature of 1065℃. R1 roughing mill had 3 passes, and R2 roughing mill had 5 passes. The intermediate slab thickness after roughing was 40 mm, and the total roughing reduction was 83.3%. The finishing mill's initial rolling temperature was 1022℃. The final rolling temperature was 895℃, and the coiling temperature was 675℃. Intermittent cooling was used, with cooling water at 24℃, and the strip was cooled to 675℃ at a rate of 26℃ / s. The coiled steel plates were then slowly cooled in a 305℃ warehouse for 48 hours.

[0054] The quenching furnace has a heating rate of 40℃ / min, a quenching temperature of 880℃, and a holding time of 80min. After the steel plate is taken out of the furnace, it is water-cooled. In order to reduce quenching stress and improve the flatness of the plate, a low-temperature tempering process is adopted, with a heating temperature of 180℃ and a holding time of 60min, followed by air cooling to room temperature.

[0055] The properties of the steel plate prepared in this embodiment are shown in Table 4:

[0056] Table 4 Performance Requirements

[0057]

[0058]

[0059] Observing the microstructure of heat-treated NM600 grade wear-resistant steel, its thickness section shows a uniform lath martensite structure, such as... Figure 2 As shown.

[0060] Example 3

[0061] A high-strength, medium-thin wear-resistant steel plate, NM600, wherein the alloy composition of the hot-rolled strip steel is shown in Table 5, with the balance being Fe and unavoidable impurities.

[0062] Table 5 Chemical composition / %

[0063] Specifications / mm C Si Mn Cr Mo Nb P S Als B 12*1500 0.36 0.65 1.6 0.95 0.6 0.018 0.006 0.001 0.024 0.0015

[0064] The continuous casting superheat was 16℃, and the casting speed was 1.0 m / min. The hot rolling process involved 190 min in the furnace, a furnace exit temperature of 1230℃, and a roughing mill exit temperature of 1053℃. R1 roughing milling consisted of 3 passes, and R2 roughing milling consisted of 5 passes. The intermediate slab thickness after roughing was 44.36 mm, and the total roughing reduction was 80.71%. The finishing mill opening temperature was 1025℃. The final rolling temperature was 904℃, and the coiling temperature was 690℃. A front-stage cooling mode was used, with cooling water at 23℃, and the strip was cooled to 690℃ at a rate of 24℃ / s. The coiled steel plates were then stacked in a silo at 315℃ for slow cooling for 48 hours.

[0065] The quenching furnace heating rate was 50℃ / min, the quenching temperature was 900℃, and the holding time was 90min. The steel plate was then water-cooled after being removed from the furnace. To reduce quenching stress and improve the flatness of the plate, a low-temperature tempering process was used, with a heating temperature of 210℃ and a holding time of 60min, followed by air cooling to room temperature. The properties of the steel plate prepared in this embodiment are shown in Table 6.

[0066] Table 6 Performance Requirements

[0067] .

Claims

1. A method for manufacturing high-strength medium-thin gauge abrasion-resistant steel plate NM600, characterized in that, The steel plate has the following chemical components and mass percentages: C: 0.35-0.4%, Si: 0.4-0.75%, Mn: 1-1.80%, Cr: 0.9-1.1%, Mo: 0.5-0.7%, Nb: 0.015-0.0255, P: ≤0.020%, S: ≤0.010%, Als: ≥0.010%, B: 0.0005-0.0060%, and the balance of Fe and inevitable impurities; The steel plate has a thickness of 2.0-12.0 mm and a width of 1500-2000 mm. The preparation method of the high-strength medium-thin plate wear-resistant steel plate NM600 comprises the following steps: (1) refining: using LF refined molten steel; (2) continuous casting: casting the molten steel into a casting blank; wherein the superheat is ≤25 ℃, and the drawing speed is controlled to be 1.0-1.1 m / min; (1) heating: the casting blank enters the heating furnace for heating, and the discharge temperature is 1190-1250 ℃, and the furnace time is 150-210 min; (2) hot rolling: the heated casting blank is subjected to hot rolling, and the hot rolling comprises rough rolling and finish rolling, and after the finish rolling, cooling and coiling are performed to obtain a steel plate; wherein the rough rolling adopts a 3+5 mode, the total reduction rate of rough rolling is 80-85%, the rough rolling outlet temperature is 1050-1080 ℃, the finish rolling opening rolling temperature is 1020-1080 ℃, the finish rolling final rolling temperature is 875-905 ℃, and the coiling temperature is 665-695 ℃; (3) slow cooling: the steel plate is slowly cooled at a temperature of 200-400 ℃ for 36-48 h; (4) heat treatment: the steel plate is first quenched and then tempered; wherein the quenching temperature is 870-920 ℃, and the holding time is 60-90 min; the tempering temperature is 150-220 ℃, and the holding time is 30-90 min; In step (1) of step (1), calcium treatment is performed after refining, and the soft argon blowing time after calcium treatment is ≥15 min; In step (2) of step (1), a carbon-free tundish slag is used in the tundish during the continuous casting process; the casting blank is pressed in 6-8 segments during the continuous casting process, and the pressing amount is 2-4%; In step (2) of step (2), the cooling mode is interval cooling; In step (4), a quenching furnace is used for quenching, and the heating speed of the quenching furnace is 35-75 ℃ / min. The steel plate has a lower yield strength of ≥1200 MPa, a tensile strength of ≥1400 MPa, an elongation after fracture of ≥8%, and a surface Brinell hardness of ≥580 HBW. In step (2) of step (1), the SiO2 in the carbon-free tundish slag is <6 wt%, the Al2O3 is >20 wt%, and the basicity is ≥5; pipeline water distribution is used during the continuous casting process; and the thickness of the casting blank is 230-240 mm. In step (2) of step (2), the cooling water temperature is 20-35 ℃, and the strip steel is cooled to 665-695 ℃ at a cooling speed of 5-40 ℃ / s. In step (2) of step (2), the thickness of the intermediate blank after rough rolling is 35-60 mm.

2. The production method according to claim 1, characterized by, ​ 3. The production method according to claim 1, characterized by, ​ 4. The production method according to claim 1, characterized by, ​ 5. The production method according to claim 1, characterized by, ​ 6. The method of claim 1, wherein, In step (four), the quenching cooling mode is water cooling, and the quenched product is tempered and then air cooled to room temperature. In step (four), the quenching cooling mode is water cooling, and the quenched product is tempered and then air cooled to room temperature.

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