High-strength wear-resistant atmosphere-corrosion-resistant hot-rolled checkered plate for railway freight car and manufacturing method of hot-rolled checkered plate

Abstract

The invention relates to the technical field of hot-rolled checkered plates, in particular to a high-strength wear-resistant atmosphere-corrosion-resistant hot-rolled checkered plate for a railway freight car and a manufacturing method of the hot-rolled checkered plate. The hot-rolled checkered plate comprises the following chemical components in percentage by weight: 0.06%-0.11% of C, 0.42%-0.55% of Si, 1.11%-1.23% of Mn, 0.007%-0.012% of P, less than or equal to 0.008% of S, 0.33%-0.42% of Cr, 0.1%-0.3% of Ni, 0.35%-0.46% of Cu, 0.12%-0.25% of Mo and the balance of Fe and inevitable impurities. The room-temperature structure of the checkered plate is ferrite (the area ratio is 80%) and pearlite (the area ratio is 20%), the yield strength is 520-600 MPa, the tensile strength is 590-630 MPa, the ductility is 21.5%-26%, the hardness is 205-221 HBW, the wear rate relative to Q345B is 30%-45%, the height of the checkered plate reaches the standard, and the plate shape is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of hot-rolled checkered plates, and in particular to a high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight cars and a manufacturing method thereof. Background Art

[0002] Hot-rolled checkered plate boasts attractive appearance, anti-slip properties, easy cleaning, and steel conservation. It is widely used in transportation, construction, interior decoration, equipment flooring, machinery, railway vehicles, shipbuilding, and other fields. Pattern shapes include diamond, lentil, round bean, and a combination of these. Traditional checkered steel users generally have low requirements for the plate's mechanical and mechanical properties, with a tensile strength requirement of 235 MPa.

[0003] With the development of the times, railway vehicle steel has placed higher demands on wear resistance, atmospheric corrosion resistance, energy conservation and emission reduction, and lightweighting. Market demand continues to grow, and the environment in which it is used is often harsh. For example, the China Railway Corporation's 2023 railway covered car renovation project replaced conventional hot-rolled checkered plate with high-strength atmospheric corrosion-resistant checkered plate, achieving an iterative material upgrade. The project required the hot-rolled atmospheric corrosion-resistant checkered plate to achieve a strength of 450 MPa and excellent wear resistance. Conventional checkered steel could no longer meet these strength and wear resistance requirements.

[0004] To improve the strength of checkered plates, there have been numerous advances in existing research. For example, patent CN118577630A discloses a method for producing thin, low-alloy, high-strength checkered plates based on the CSP process. The composition is: C: 0.04% to 0.07%, Si: 0.10% to 0.20%, Mn: 0.95% to 1.20%, P: ≤ 0.20%, Cr: 0.20% to 0.30%, Ti: 0.12% to 0.15%, V: 0.02% to 0.03%. This checkered plate has a high P content and is based on a method for controlling the shape of checkered plates above 700 MPa using a CSP line. However, no mention is made of wear resistance. Patent CN112246868A discloses a method for producing a substrate for cold-rolling 700 MPa high-strength patterned plate. The method adopts a three-stage cooling method: rapid cooling in the front stage, air cooling in the middle stage, and rapid cooling in the rear stage. This method solves the problem of insufficient pattern height caused by cold-working and embossing high-strength steel. The content of C is 0.01% to 0.08%, Mn is 1.65% and 1.85%, S is ≤0.010%; P is ≤0.20%, Si is ≤0.15%, Nb is 0.04% and 0.10%, and Ti is 0.08% and 0.12%. The cold-rolling substrate has a high P content, and wear resistance is not mentioned. Patent CN117732887A discloses a method for producing thin-gauge checkered plates without pickling. By controlling the temperature of the slab out of the furnace and the rolling temperature, the temperature uniformity of the slab is controlled, and the plate shape is better improved. By adjusting the cooling method and cooling rate, the technical problem of the plate shape warping after low-temperature coiling of thin-gauge checkered plates is solved, and the production of thin-gauge checkered plates with high-quality patterns and excellent plate shape is achieved, but the composition and strength are not mentioned.

[0005] Therefore, there is an urgent need to develop a high-strength, wear-resistant, atmospheric corrosion-resistant anti-skid hot-rolled patterned plate for railway freight vehicles to meet market demand and promote material iteration and upgrading. Summary of the Invention

[0006] In response to the above-mentioned technical problems that the strength, wear resistance and atmospheric corrosion resistance of the checkered plates in the prior art cannot meet market demand, and the production and processing of high-strength checkered plates are difficult, and the height and plate shape cannot be guaranteed, the present invention provides a high-strength, wear-resistant and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight cars and a manufacturing method thereof. The checkered plate has a good market prospect and is of great significance to the development of my country's steel industry.

[0007] In order to achieve the above object, the technical solution of the present invention is as follows: On one hand, the present invention provides a high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight vehicles. The chemical composition of the hot-rolled checkered plate is as follows, by weight percentage: C: 0.06%-0.11%, Si: 0.42%-0.55%, Mn: 1.11%-1.23%, P: 0.007%-0.012%, S≤0.008%, Cr: 0.33%-0.42%, Ni: 0.1%-0.3%, Cu: 0.35%-0.46%, Mo: 0.12%-0.25%, and the balance is Fe and unavoidable impurities.

[0008] The following describes in detail the mechanism of action of the various alloy components of the structural steel of the present invention, wherein the percentage symbol % represents weight percentage: C: The primary functions of C in steel are solid solution strengthening and precipitation strengthening. The steel described in this invention is designed to be low-carbon. To ensure the steel's toughness and ductility, the carbon content is no higher than 0.11%. To ensure the steel's strength and wear resistance, the C content is set to no less than 0.06%.

[0009] Si: Si plays two main roles in steel. First, it acts as a desulfurizer and deoxidizer during steelmaking. Second, as an alloying element, Si forms a solid solution with the iron in the steel, increasing strength. Furthermore, Si combines with Cr to improve corrosion resistance and oxidation resistance, and combines with Mo to increase hardness and wear resistance. Therefore, the lower limit of Si content is set at 0.42%. Excessive Si content significantly reduces the plasticity and toughness of the steel. Therefore, the present invention controls the Si content to no more than 0.55%.

[0010] Mn: Mn plays two primary roles in steel: first, as a deoxidizer and desulfurizer, it mitigates and eliminates the adverse effects of sulfur. Second, it provides solid solution strengthening and grain refinement, significantly increasing the strength of the steel plate, as well as its hardenability and hardness. Too little Mn content will not achieve these effects, so the lower limit is set at 1.11%. Excessive Mn content can lead to significant internal stress during rapid cooling, increasing the tendency to crack, so the upper limit is set at 1.23%.

[0011] P: P is an impurity element that embrittles ferrite grain boundaries. To ensure the plasticity, toughness and welding properties of the steel of the present invention, the upper limit of the P content is set at 0.012%.

[0012] S: S is an impurity element that forms non-metallic inclusions such as MnS, so it is controlled below 0.008% to reduce sulfur dendrite segregation and sulfide formation, thereby improving plasticity.

[0013] Cr: Cr has three primary functions in steel: first, solid solution strengthening ensures steel strength; second, it forms cementite and various carbides within the steel, improving its wear resistance; and third, it forms a dense chromium oxide film on the steel surface, which blocks internal oxidation. For example, it combines with Cu to form a dense Cr-Cu compound protective rust layer, which significantly inhibits the penetration of corrosive media and significantly improves the steel's corrosion resistance. The present invention sets the lower limit of Cr content at 0.33%. A Cr content exceeding 0.42% degrades the weldability of the steel plate, so the present invention sets the lower limit of Cr content at 0.42%.

[0014] Ni: Ni's primary role in steel is grain refinement, ensuring the steel's plasticity and toughness. It also provides high corrosion resistance and rust prevention in the acidic and alkaline environments of railway boxcars. Furthermore, Ni can reduce the "copper brittleness" defect caused by Cu. However, Ni is a scarce resource with high costs, so its content must be controlled. Therefore, the Ni content in this invention is set at 0.1% to 0.3%.

[0015] Cu: Cu can improve the strength of steel through fine precipitates. At the same time, the Cr-Cu compounds formed can significantly improve the corrosion resistance of steel. The present invention sets the lower limit of the Cu content to 0.35%. Too high a Cu content will cause hot brittleness, so the upper limit of the Cu content is set to 0.46%.

[0016] Mo: Mo combines with C to generate hard phase Mo2C3 inside the grains, which can improve the hardness and wear resistance of the steel. Mo combines with Si to form Mo2Si3 hard phase particles, which significantly improves the wear resistance of the steel. Considering the cost, the Mo content in the present invention is set to 0.12%~0.25%.

[0017] In the above technical solution, further, the specification of the hot-rolled patterned plate is: thickness 4~9mm.

[0018] In the above technical solution, further, the metallographic structure of the hot-rolled patterned plate is ferrite accounting for 80% of the area and pearlite accounting for 20% of the area.

[0019] In the above technical solution, further, the hot-rolled patterned plate has a yield strength of 520~600MPa, a tensile strength of 590~630MPa, an elongation of 21.5%~26%, a hardness of 205~221HBW, and a wear rate of 30%~45% relative to Q345B.

[0020] The present invention also provides a method for manufacturing the above-mentioned high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight vehicles, the method comprising the following steps: (1) Steelmaking: After desulfurization pretreatment of molten iron, the sulfur content in the molten iron is ≤0.008%, smelted in a top-bottom combined blown converter, and refined in a LF furnace; (2) Continuous casting: continuous casting speed 0.6~1.2m / min, secondary cooling water volume 0.15~0.35L / kg; (3) Rolling: The billet enters the heating furnace and stays in the furnace for no less than 120 minutes. The tapping temperature is 1180-1240°C, the rough rolling and final rolling temperatures are 1000-1200°C, and the finishing rolling is carried out on 7 stands, of which the last stand is a printing stand, and the finishing rolling temperature is 880-920°C. (4) Cooling: The front section of the patterned plate is cooled by laminar flow, the upper surface cooling manifold adopts intermittent mode, and the lower surface cooling manifold adopts continuous mode, and is cooled to the coiling temperature; (5) Coiling: The patterned plate is coiled after cooling, and the coiling temperature is 640~660℃.

[0021] In the above technical solution, further, in the step (1), the amount of desulfurizer added is ≥10 kg / ton of steel; In top-bottom combined-blowing converter smelting, the tapping temperature is 1660~1680℃; During LF furnace refining, Si-Ca wire is fed, the wire feeding speed is ≥3.5m / s, the wire feeding amount is (1.6~2.5)m / ton of steel, the deoxidation time is not less than 7 minutes, the oxygen content is controlled below 4.5ppm, and the superheat of the molten steel is 10~15℃.

[0022] In the above technical solution, further, in the step (3), the final stand is provided with grooves with a groove depth of 2.1~3.2mm, the upper working roll of the final stand adopts a flat roll without convexity, and the upper roll pressure is set to 2~4mm, and the lower working roll adopts a -20 μm sine roll profile; the bean height and plate shape are ensured by controlling the rolling roll gap and rolling force, the stand roll gap is 4~32mm, the rolling force is 8000~30200KN, the rolling amount of a single patterned roller is less than 4000t, and the rolling cycle is within 60km, so as to avoid unqualified bean height due to wear of the patterned roller.

[0023] In the above technical solution, further, in step (3), the thickness of the finished product is h, and the thickness of the finished product and the furnace temperature satisfy the following relationship: When 4mm<h≤5mm, the furnace temperature is 1220~1240℃; When 6mm<h≤8mm, the furnace temperature is 1200~1220℃; When 8mm<h≤9mm, the furnace temperature is 1180~1200℃.

[0024] The beneficial effects of the present invention are: The present invention produces a high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight vehicles with a thickness of 4 to 9 mm. The room temperature structure of the checkered plate is ferrite (accounting for 80% by area) + pearlite (accounting for 20% by area), the yield strength is 520 to 600 MPa, the tensile strength is 590 to 630 MPa, the elongation is 21.5% to 26%, the hardness is 205 to 221 HBW, the wear rate relative to Q345B is between 30% and 45%, the pattern height meets the standard, and the plate shape is excellent. DETAILED DESCRIPTION

[0025] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0026] The chemical compositions of the patterned plates of Examples 1-10 of the present invention are shown in Table 1.

[0027] Table 1 Chemical composition of the patterned plates of Examples 1-10, %

[0028] The method for manufacturing the above-mentioned patterned plate comprises the following steps: (1) Steelmaking: After the molten iron is pre-treated for desulfurization, it is smelted in a top-bottom combined blown converter and refined in a LF furnace. The amount of desulfurizer added is ≥10kg / ton of steel. After desulfurization, the S content in the molten iron is ≤0.008%. After the top-bottom combined blown converter, the tapping temperature is 1660~1680℃. Si-Ca wire is fed for treatment. The wire feeding speed is ≥3.5m / s and the wire feeding amount is (1.6-2.5)m / ton of steel. The deoxidation time is not less than 7 minutes and the oxygen content is controlled below 4.5ppm to ensure that the inclusions float fully. The superheat of the molten steel is strictly controlled at 10~15℃ to prevent the molten steel from being overheated and causing cracks inside the continuous casting slab. (2) Continuous casting: The continuous casting speed is 0.6~1.2m / min, the secondary cooling water volume is 0.15~0.35L / kg, and the molten steel is protected by protective slag throughout the continuous casting process. The continuous casting billet with a thickness of 210~230mm and a width of 950~1650mm is obtained. The accuracy of the continuous casting machine roll gap is confirmed before production, and the roll gap deviation is controlled within ±0.5mm to avoid cracks in the continuous casting billet caused by accessory stress, and to avoid rupture and elongation during the subsequent hot rolling process; (3) Rolling: The billet enters the heating furnace and stays in the furnace for no less than 120 minutes. Different discharge temperatures are set according to different thicknesses. When the finished product thickness (h) is 4mm<h≤5mm, the discharge temperature is 1220~1240℃; when it is 6mm<h≤8mm, the discharge temperature is 1200~1220℃; when it is 8mm<h≤9mm, the discharge temperature is 1180~1200℃. Due to the presence of the pattern, the metal flow on the upper and lower surfaces of the strip steel on the printing rack is asymmetric. In order to facilitate the formation of the pattern and ensure the bean height, the rough rolling and final rolling temperatures are controlled at 1000~1200℃. There are 7 finishing rolling mills, of which the last rack is the printing rack (groove depth 2.1~3.2mm). The upper working roll is a flat roll without convexity, and the upper roll pressure is set to 2~4mm. The lower working roll is -20 μm sinusoidal roll profile, finishing rolling temperature of 880~920℃, high temperature rolling reduces rolling force, and bean height and plate shape are guaranteed by controlling the rolling roll gap and rolling force. The roll gap of the stand is 4~32mm, the rolling force is 8000~30200KN, the rolling capacity of a single pattern roller is controlled below 4000t, and the rolling cycle is controlled within 60km to avoid unqualified bean height due to pattern roller wear; (4) Cooling: The front section of the patterned plate is laminar cooled. Considering that there is water between the patterns on the upper surface of the patterned plate, the upper surface cooling manifold adopts intermittent mode and the lower surface cooling manifold adopts continuous mode to cool to the coiling temperature; (5) Coiling: After the pattern plate is cooled, it is coiled and the coiling temperature is controlled at 640~660℃. Low temperature coiling can alleviate the phenomenon of pattern flattening and obtain high-strength, wear-resistant and atmospheric corrosion-resistant hot-rolled pattern plate with a thickness of 4~9mm for railway freight vehicles.

[0029] The steelmaking process parameters of Examples 1-10 are shown in Table 2; Table 2 Steelmaking and continuous casting process parameters of Examples 1-10

[0030] The rolling and coiling process parameters of Examples 1-10 are shown in Tables 3-5; Table 3 Rolling and coiling process parameters of Examples 1-10

[0031] Table 4 Frame roll gap design of Examples 1-10, mm

[0032] Table 5 Rolling force of the stand of Examples 1-10, KN

[0033] The properties of the patterned plates of Examples 1-10 are shown in Table 6.

[0034] Table 6 Properties of the checkered plates of Examples 1-10

[0035] The wear resistance test was carried out on a wet rubber wheel abrasive wear testing machine with an experimental size of 57.0 mm × 25.5 mm × 6.0 mm. The abrasive wear test was carried out in accordance with JB / T 7705-1995 Loose Abrasives Abrasive Wear Test Method Rubber Wheel Method.

[0036] Table 7 Comparative results of rapid corrosion tests of patterned plates of Examples 1-10 and control steel

[0037] The thickness parameters of the patterned plate of Example 1 are shown in Table 8.

[0038] Table 8 Thickness parameters of the patterned plate of Example 1, mm

[0039] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. A high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight vehicles, characterized in that: The chemical composition of the hot-rolled patterned plate is as follows by weight: C: 0.06%~0.11%, Si: 0.42%~0.55%, Mn: 1.11%~1.23%, P: 0.007%~0.012%, S≤0.008%, Cr: 0.33%~0.42%, Ni: 0.1%~0.3%, Cu: 0.35%~0.46%, Mo: 0.12%~0.25%, and the balance is Fe and unavoidable impurities.

2. The high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight vehicles according to claim 1, characterized in that: The specifications of the hot-rolled patterned plate are: thickness 4~9mm.

3. The high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight vehicles according to claim 1, characterized in that: The metallographic structure of the hot-rolled patterned plate is ferrite accounting for 80% of the area and pearlite accounting for 20% of the area.

4. The high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight cars according to claim 1, characterized in that: The hot-rolled checkered plate has a yield strength of 520-600 MPa, a tensile strength of 590-630 MPa, an elongation of 21.5%-26%, a hardness of 205-221 HBW, and a wear rate of 30%-45% relative to Q345B.

5. A method for manufacturing a high-strength, wear-resistant, and atmospheric corrosion-resistant hot-rolled checkered plate for railway freight cars according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) Steelmaking: After desulfurization pretreatment of molten iron, the sulfur content in the molten iron is ≤0.008%, smelted in a top-bottom combined blown converter, and refined in a LF furnace; (2) Continuous casting: continuous casting speed 0.6~1.2m / min, secondary cooling water volume 0.15~0.35L / kg; (3) Rolling: The billet enters the heating furnace and stays in the furnace for no less than 120 minutes. The tapping temperature is 1180-1240°C, the rough rolling and final rolling temperatures are 1000-1200°C, and the finishing rolling is carried out on 7 stands, of which the last stand is a printing stand, and the finishing rolling temperature is 880-920°C. (4) Cooling: The front section of the patterned plate is cooled by laminar flow, the upper surface cooling manifold adopts intermittent mode, and the lower surface cooling manifold adopts continuous mode, and is cooled to the coiling temperature; (5) Coiling: The patterned plate is coiled after cooling, and the coiling temperature is 640~660℃.

6. The manufacturing method according to claim 5, characterized in that In the step (1), the amount of desulfurizer added is ≥10 kg / ton of steel; In top-bottom combined-blowing converter smelting, the tapping temperature is 1660~1680℃; During LF furnace refining, Si-Ca wire is fed, the wire feeding speed is ≥3.5m / s, the wire feeding amount is (1.6~2.5)m / ton of steel, the deoxidation time is not less than 7 minutes, the oxygen content is controlled below 4.5ppm, and the superheat of the molten steel is 10~15℃.

7. The manufacturing method according to claim 5, characterized in that In the step (3), the last stand is provided with grooves with a groove depth of 2.1-3.2 mm. The upper working roll of the last stand adopts a flat roll without crowning and the upper roll pressure is set to 2-4 mm. The lower working roll adopts a -20 μm sinusoidal roll profile. The stand roll gap is 4-32 mm and the rolling force is 8000-30200 KN.

8. The manufacturing method according to claim 5, characterized in that In step (3), the thickness of the finished product is h, and the thickness of the finished product and the furnace temperature satisfy the following relationship: When 4mm<h≤5mm, the furnace temperature is 1220~1240℃; When 6mm<h≤8mm, the furnace temperature is 1200~1220℃; When 8mm<h≤9mm, the furnace temperature is 1180~1200℃.

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