High-strength medium-thin wear-resistant steel plate NM600 and production method thereof

Abstract

The invention discloses a high-strength medium-thin wear-resistant steel plate NM600 and a production method thereof, and belongs to the field of metallurgy, alloy or non-ferrous metal treatment. The steel plate comprises the following chemical components in percentage by mass: 0.35 to 0.4 percent of C, 0.4 to 0.75 percent of Si, 1.0 to 1.80 percent of Mn, 0.9 to 1.1 percent of Cr, 0.5 to 0.7 percent of Mo, less than or equal to 0.0255 percent of Nb, less than or equal to 0.020 percent of P, less than or equal to 0.010 percent of S, more than or equal to 0.010 percent of Als, 0.0005 to 0.0060 percent of B and the balance of Fe and inevitable impurities. The thickness of the steel plate ranges from 2.0 mm to 12.0 mm, and the width of the steel plate ranges from 1500 mm to 2000 mm. C, Mn and Cr are reasonably designed, so that the content of precious alloy of Ni and Mo can be effectively reduced, the mechanical property is not reduced, and the effect of reducing the cost is achieved.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, alloy or nonferrous metal processing, and in particular to a thin high-strength wear-resistant steel plate NM600 and a production method thereof. Background Art

[0002] Wear-resistant steel, as a vital steel material, has been widely used in many fields such as engineering machinery, mining machinery, coal mining and transportation due to its comprehensive properties such as 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 has also shown a steady growth trend.

[0003] At present, high-strength steel, wear-resistant steel and aluminum have become the mainstream materials in the market, and the emphasis is on applying the right materials to the right parts to achieve the best results. In this context, wear-resistant steel is mainly used in the bodies of heavy-duty mining trucks and highway dump trucks, the beams and booms of semi-trailers and other key structural parts due to its excellent performance. Compared with general structural steel, wear-resistant steel not only has higher wear resistance and strength, but also can make the body thinner and lighter, thereby further improving the overall performance and efficiency.

[0004] However, the wear-resistant steel product market is currently dominated by international brands such as Hardox, EVERHARD and XAR. The design of domestic wear-resistant steel plates is mostly based on the standard GB / T 24186-2009 "High-strength wear-resistant steel for engineering machinery", but it is still insufficient in developing personalized products for different application fields, and there is a certain gap compared with foreign brands. At the same time, wear-resistant steel currently uses precious alloy elements such as Ni and Mo to improve the wear resistance of steel, which is relatively expensive. Therefore, the present invention provides a high-strength medium-thin wear-resistant steel plate NM600 and a production method thereof, which is suitable for wear-resistant steel for dump truck compartments and reduces costs. Summary of the invention

[0005] In order to solve the problems of the prior art, the present invention provides a high-strength medium-thin wear-resistant steel plate NM600 and a production method thereof, with a thickness of 2.0 mm to 12 mm and a width of 1500 mm to 2000 mm. The present invention can adjust the mechanical properties of wear-resistant steel by adding alloy elements and adjusting the alloy content. By reasonably designing C, Mn, and Cr, the precious alloy content of Ni and Mo can be effectively reduced without reducing the mechanical properties, thereby achieving the effect of reducing costs.

[0006] A high-strength medium-thin wear-resistant steel plate NM600, the chemical composition and mass percentage of the steel plate are: 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 unavoidable impurities.

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

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

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

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

[0011] (I) Steelmaking

[0012] (1) Refining: LF single path is used to produce molten steel.

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

[0014] (2) Continuous casting: Continuously casting molten steel into ingots; wherein, the superheat is ≤25°C. A lower superheat of molten steel can reduce the columnar crystal ratio during the solidification process of molten steel. The constant pulling speed is controlled at 1.0-1.1 m / min. Stable pulling speed control is conducive to accurate pressing of the ingot and the generation of equiaxed crystals, reducing ingot segregation.

[0015] Furthermore, the tundish slag in the continuous casting process adopts a new type of carbon-free tundish slag, the composition of which is SiO2<6wt%, Al2O3>20wt%, and basicity≥5, so as to improve the adsorption capacity of inclusions in the casting process.

[0016] Furthermore, the water distribution in the continuous casting process adopts pipeline water distribution.

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

[0018] Furthermore, the thickness of the ingot is 230-240 mm.

[0019] Furthermore, the equiaxed grain content of the continuous casting billet is ≥40%, and the low magnification requirement of the casting billet is <1.0.

[0020] (2) Rolling

[0021] (1) Heating: The ingot is heated in a heating furnace, the furnace temperature is 1190-1250°C, and the furnace time is 150-210 min.

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

[0023] Furthermore, the cooling mode adopts interval cooling. The cooling water temperature fluctuates within 20-35°C, and the strip is cooled to 665-695°C at a cooling rate of 5-40°C / s.

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

[0025] Furthermore, the total reduction ratio of rough rolling is 80 to 85%.

[0026] Furthermore, the finishing rolling start temperature is 1020-1080°C.

[0027] 3. Slow cooling

[0028] The coiled steel plates are stacked in a hot zone in the warehouse at a temperature of 200-400°C for slow cooling, and the slow cooling time is 36-48 hours.

[0029] 4. Heat treatment

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

[0031] Furthermore, quenching is performed in a quenching furnace, and the heating rate of the quenching furnace is 35-75°C / min.

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

[0033] Beneficial effects of the present invention:

[0034] (1) The mechanical properties of wear-resistant steel can be controlled by adding alloy elements and adjusting the alloy content. Reasonable design of C, Mn, and Cr can effectively reduce the precious alloy content of Ni and Mo without reducing the mechanical properties, thereby reducing costs.

[0035] (2) The continuous casting process of the steelmaking process adopts constant pulling speed control and other methods to reduce the defects of the casting billet. The rolling process adopts controlled rolling and controlled cooling technology and heat treatment technology to ensure the performance stability of high-strength wear-resistant steel. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 2 This is the metallographic structure of the steel plate prepared in Example 2. DETAILED DESCRIPTION

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

[0039] Example 1

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

[0041] Table 1 Chemical composition / %

[0042] Specification / 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 overheat is 11℃, and the pulling speed is 1.0m / min. The heating furnace time in the hot rolling process is 182min, the furnace temperature is 1210℃, the rough rolling outlet temperature is 1060℃, the R1 rough rolling pass is 3 times, the R2 rough rolling pass is 5 times, the intermediate billet thickness after rough rolling is 35.63mm, and the total rough rolling reduction is 84.5%. The finishing rolling start temperature is 1020℃. The final rolling temperature is 900℃, the coiling temperature is 680℃, the interval cooling mode, the cooling water temperature is 25℃, and the strip is cooled to 680℃ at a cooling rate of 26℃ / s. The coiled steel plate is stacked in the hot zone of the warehouse at a temperature of 300℃ for slow cooling, and the slow cooling time is 48h.

[0044] The heating speed of the quenching furnace is 50℃ / min, the quenching temperature is 900℃, the holding time is 60min, and the steel plate is water-cooled after leaving the furnace. In order to reduce the quenching stress and improve the flatness of the plate, a low-temperature tempering process is adopted, the heating temperature is 180℃, the holding time is 60min, and then air-cooled 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] Observe the microstructure of heat-treated NM600 grade wear-resistant steel. Its thickness section is a uniform lath martensite structure. Figure 1 shown.

[0049] Example 2

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

[0051] Table 3 Chemical composition / %

[0052]

[0053] The continuous casting overheat is 19℃, and the pulling speed is 1.1m / min. The heating furnace time in the hot rolling process is 201min, the furnace temperature is 1195℃, the rough rolling outlet temperature is 1065℃, the R1 rough rolling pass is 3 times, the R2 rough rolling pass is 5 times, the intermediate billet thickness after rough rolling is 40mm, and the total rough rolling reduction rate is 83.3%. The finishing rolling start temperature is 1022℃. The final rolling temperature is 895℃, the coiling temperature is 675℃, the interval cooling mode, the cooling water temperature is 24℃, and the strip is cooled to 675℃ at a cooling rate of 26℃ / s. The coiled steel plate is stacked in the hot zone of the warehouse at a temperature of 305℃ for slow cooling, and the slow cooling time is 48h.

[0054] The heating speed of the quenching furnace is 40℃ / min, the quenching temperature is 880℃, the holding time is 80min, and the steel plate is water-cooled after leaving the furnace. In order to reduce the quenching stress and improve the flatness of the plate, a low-temperature tempering process is adopted, the heating temperature is 180℃, the holding time is 60min, and then air-cooled 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] Observe the microstructure of heat-treated NM600 grade wear-resistant steel. Its thickness section is a uniform lath martensite structure. Figure 2 shown.

[0060] Example 3

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

[0062] Table 5 Chemical composition / %

[0063] Specification / 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 overheat is 16℃, and the pulling speed is 1.0m / min. The heating furnace time in the hot rolling process is 190min, the furnace temperature is 1230℃, the rough rolling outlet temperature is 1053℃, the R1 rough rolling pass is 3 times, the R2 rough rolling pass is 5 times, the intermediate billet thickness after rough rolling is 44.36mm, and the total rough rolling reduction rate is 80.71%. The finishing rolling start temperature is 1025℃. The final rolling temperature is 904℃, the coiling temperature is 690℃, the front cooling mode, the cooling water temperature is 23℃, and the strip is cooled to 690℃ at a cooling rate of 24℃ / s. The coiled steel plate is stacked in the hot zone of the warehouse at a temperature of 315℃ for slow cooling, and the slow cooling time is 48h.

[0065] The heating rate of the quenching furnace is 50°C / min, the quenching temperature is 900°C, the holding time is 90 minutes, and the steel plate is water-cooled after leaving the furnace. In order to reduce the quenching stress and improve the flatness of the plate, a low-temperature tempering process is adopted, the heating temperature is 210°C, the holding time is 60 minutes, and then air-cooled 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 high-strength medium-thin wear-resistant steel plate NM600, characterized in that: The chemical composition and mass percentage of the steel are: 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 unavoidable impurities.

2. The high-strength medium-thin wear-resistant steel plate NM600 according to claim 1 is characterized in that: The steel plate has a thickness of 2.0 mm to 12.0 mm and a width of 1500 mm to 2000 mm.

3. The high-strength medium-thin wear-resistant steel plate NM600 according to claim 1 is characterized in that: 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.

4. The method for preparing the high-strength medium-thin wear-resistant steel plate NM600 according to any one of claims 1 to 3, characterized in that: The steps include: (I) Steelmaking (1) Refining: LF is used to refine molten steel; (2) Continuous casting: Continuously casting molten steel into ingots; wherein the superheat is ≤25°C and the casting speed is controlled at 1.0-1.1 m / min; (2) Rolling (1) Heating: The billet enters the heating furnace for heating, the furnace temperature is 1190-1250°C, and the furnace time is 150-210 min; (2) Hot rolling: The heated ingot is hot rolled, which includes rough rolling and finish rolling. After finish rolling, the ingot is cooled and coiled to obtain a steel plate. The rough rolling adopts the 3+5 mode, the rough rolling outlet temperature is 1050-1080°C, the finish rolling temperature is 875-905°C, and the coiling temperature is 665-695°C. (III) Slow cooling The steel plate is slowly cooled at a temperature of 200-400°C for 36-48 h; (IV) Heat treatment The steel plate is first quenched and then tempered; the quenching temperature is 870-920°C and the holding time is 60-90 min; the tempering temperature is 150-220°C and the holding time is 30-90 min.

5. The preparation method according to claim 4, characterized in that: In step (1) of step (I), calcium treatment is performed after refining, and the soft argon blowing time after calcium treatment is ≥15 min.

6. The preparation method according to claim 4, characterized in that: In (2) of step (a), the intermediate slag in the continuous casting process adopts carbon-free intermediate slag, wherein SiO2 is less than 6wt%, Al2O3 is greater than 20wt%, and the basicity is ≥5; the water distribution in the continuous casting process adopts pipeline water distribution; in the continuous casting process, the continuous casting machine fan-shaped section has the billet pressing action in sections 6 to 8, and the pressing amount is 2 to 4%; the thickness of the billet is 230 to 240 mm.

7. The preparation method according to claim 4, characterized in that: In step (ii) (2), the cooling mode adopts interval cooling; the cooling water temperature is 20-35°C, and the strip is cooled to 665-695°C at a cooling rate of 5-40°C / s.

8. The preparation method according to claim 4, characterized in that: In step (ii) (2), the thickness of the intermediate billet after rough rolling is 35-60 mm; the total reduction rate of rough rolling is 80-85%; and the start temperature of finishing rolling is 1020-1080°C.

9. The preparation method according to claim 4, characterized in that: In step (iv), a quenching furnace is used for quenching, and the heating rate of the quenching furnace is 35-75°C / min; the quenched steel plate is water-cooled, and then tempered, and then air-cooled to room temperature.

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