Production method of high-strength steel for easy-to-form sand-gravel material transport carriage body

Abstract

The invention discloses a production method of high-strength steel easy to bend and form for a sandstone material transport carriage body. The high-strength steel comprises the following chemical components in percentage by weight: 0.15%-0.20% of C, 0.50%-0.70% of S i, 1.20%-1.50% of Mn, less than or equal to 0.012% of P, less than or equal to 0.003% of S, 0.010%-0.030% of Nb, 0.010%-0.030% of T i, 0.10%-0.30% of Cr, 0.0005%-0.0020% of B, 0.020%-0.050% of Al and the balance of Fe and inevitable impurities. A ferrite, martensite and a small amount of retained austenite complex phase structure is obtained through a two-stage cooling process, a ferrite and metastable state austenite composite soft phase structure is introduced to a hard martensite matrix, the toughness, plasticity and formability are improved, and the high-strength steel plate which is high in strength, resistant to abrasion, low in yield ratio and easy to form is produced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-strength steel, and particularly relates to a production method of high-strength steel for an easily-formed sand and gravel material transport vehicle compartment body. BACKGROUND

[0002] With the development trend of light weight, higher requirements are put forward for the load capacity and fuel consumption of vehicles, and light weight, safety and reliability become the key development direction of transport vehicles. At present, the sand and gravel material transport vehicle uses low-strength steel materials with large thickness, which cannot meet the requirements of light weight, and high-strength steel materials are prone to cracking after being bent and formed, so it is necessary to develop a high-strength steel with high strength and good bending performance.

[0003] Patent No. CN 107099730 A discloses a manufacturing method of thin-gauge high-Ti wear-resistant steel NM360, which adopts Mo, Cr, Nb, Ti and B alloying, and produces wear-resistant steel NM360 through two-stage controlled rolling, ultra-fast cooling, quenching after opening and tempering process. The alloy cost is high, and the process flow is long. Patent No. CN 107099731 A discloses a manufacturing method of thin-gauge high-Ti wear-resistant steel NM360 produced by online quenching, which adopts Mo, Cr, Nb, Ti and B alloying, and produces wear-resistant steel NM360 through thin slab continuous casting and rolling process and ultra-fast cooling online quenching process. The alloy content is high, the cost is high, and the application production process is thin slab continuous casting and rolling, which is different from the thick slab controlled rolling and controlled cooling process. SUMMARY

[0004] The purpose of the application is to provide a production method of high-strength steel for an easily-formed sand and gravel material transport vehicle compartment body. Through controlled rolling and controlled cooling and stage cooling process, ferrite and metastable austenite complex soft phase structure is introduced on the hard martensite matrix to increase toughness, plasticity and formability, and high-strength steel with low yield ratio and excellent bending performance is produced.

[0005] To solve the above technical problems, the application adopts the following technical scheme:

[0006] The production method of high-strength steel for an easily-formed sand and gravel material transport vehicle compartment body comprises the following steps: smelting: hot metal pretreatment, converter smelting, LF furnace outer refining, RH vacuum treatment, slab continuous casting and stack slow cooling; rolling: slab heating, high-pressure water descaling, E1R1 rough rolling, E2R2 rough rolling, flying shear, high-pressure water descaling, F1-F7 finish rolling, intensive laminar cooling, coiling, air cooling, opening, straightening, trimming and sizing; characterized in that:

[0007] 1) smelting and casting

[0008] The smelting process adopts KR method to desulfurize molten iron and high-quality scrap steel, so as to ensure that the element S of molten iron entering the converter is less than or equal to 0.003%; during the converter smelting, low-sulfur scrap steel is used, and the tapping temperature is greater than or equal to 1620℃; LF refining slagging desulfurization is adopted to ensure that S is less than or equal to 0.003%, and chromium iron and niobium iron are added during the refining process; the RH vacuum treatment time is greater than 20 min, and titanium iron and boron iron are added during the vacuum treatment process; after vacuum treatment, the molten steel is subjected to calcium treatment, and the argon soft blowing time is greater than 12 min, so that the inclusions are fully denatured and floated; during slab continuous casting, full-process protection casting is adopted, the superheat is controlled to be 15-25℃, and the drawing speed is 0.90-1.10 m / min;

[0009] 2), heating and rolling

[0010] A walking beam furnace is used for heating, the heating temperature is 1180-1220℃, the heating time is greater than or equal to 120 min, and the temperature uniformity is ensured; the rolling process adopts rough rolling and finish rolling, the rough rolling is carried out by using R1 two-high horizontal reversible rolling mill and R2 four-high horizontal reversible rolling mill; the finish rolling is carried out by using seven-stand four-high finish rolling mill, the finish rolling starting temperature is 980-1040℃, and the finish rolling ending temperature is 820-880℃;

[0011] 3), cooling

[0012] After rolling, laminar flow cooling is carried out, the cooling mode is stage cooling, the front stage adopts laminar flow cooling, the temperature is cooled from 820-880℃ to 600-700℃ at a cooling rate of 20-30℃ / s, then air cooling is carried out, the air cooling time is 8-12 s, the temperature is cooled to 500-600℃, and the temperature is rapidly cooled to 100-200℃ at a cooling rate of 40-50℃ / s, and then air cooling is carried out to room temperature;

[0013] 4), flattening, straightening and shearing

[0014] The steel coil is subjected to flattening and straightening, the plate shape after straightening is good, the flatness of the steel plate is less than or equal to 5 mm / 1 m, and the steel plate is cut to a required size and a rough edge according to requirements, so that the required high-strength steel is obtained;

[0015] The chemical composition of the high-strength steel is as follows in terms of percentage by weight: C: 0.15-0.20%, Si: 0.50-0.70%, Mn: 1.20-1.50%, P: ≤0.012%, S: ≤0.003%, Nb: 0.010-0.030%, Ti: 0.010-0.030%, Cr: 0.10-0.30%, B: 0.0005-0.0020%, Als: 0.020-0.050%, and the balance is Fe and inevitable impurities.

[0016] Further, the chemical composition of the high-strength steel is C: 0.18%, Si: 0.55%, Mn: 1.30%, P: 0.010%, S: 0.003%, Nb: 0.012%, Ti: 0.015%, Cr: 0.20%, B: 0.0008%, Als: 0.030%, and the balance of Fe and inevitable impurities.

[0017] Further, the chemical composition of the high-strength steel is C: 0.17%, Si: 0.60%, Mn: 1.25%, P: 0.009%, S: 0.002%, Nb: 0.020%, Ti: 0.022%, Cr: 0.15%, B: 0.0012%, Als: 0.035%, and the balance of Fe and inevitable impurities.

[0018] Further, the chemical composition of the high-strength steel is C: 0.19%, Si: 0.62%, Mn: 1.42%, P: 0.008%, S: 0.001%, Nb: 0.026%, Ti: 0.030%, Cr: 0.30%, B: 0.0010%, Als: 0.038%, and the balance of Fe and inevitable impurities.

[0019] Further, the slab heating temperature is 1190℃, the heating time is 120min; rough rolling is carried out by R1 and R2; the rough rolling temperature is 1000℃, the finish rolling temperature is 860℃, after the rolling is finished, laminar flow cooling is carried out, the cooling mode is two-stage cooling, the front-stage is fast cooling to 620℃, the air cooling time is 10s, the coiling temperature is 120℃, after air cooling to room temperature, the high-strength steel is obtained by opening flat, straightening and cutting to size.

[0020] Further, the slab heating temperature is 1200℃, the heating time is 130min; rough rolling is carried out by R1 and R2; the rough rolling temperature is 1010℃, the finish rolling temperature is 850℃, after the rolling is finished, laminar flow cooling is carried out, the cooling mode is two-stage cooling, the front-stage is fast cooling to 630℃, the air cooling time is 11s, the coiling temperature is 100℃, after air cooling to room temperature, the high-strength steel is obtained by opening flat, straightening and cutting to size.

[0021] Further, the slab heating temperature is 1200℃, the heating time is 125min; rough rolling is carried out by R1 and R2; the rough rolling temperature is 1020℃, the finish rolling temperature is 870℃, after the rolling is finished, laminar flow cooling is carried out, the cooling mode is two-stage cooling, the front-stage is fast cooling to 610℃, the air cooling time is 12s, the coiling temperature is 150℃, after air cooling to room temperature, the high-strength steel is obtained by opening flat, straightening and cutting to size.

[0022] Compared with the prior art, the present application has the beneficial technical effects of:

[0023] By means of low-cost component design and in combination with a two-stage cooling process, a ferrite, martensite and a small amount of residual austenite complex phase structure is obtained, ferrite and metastable austenite complex soft phase structures are introduced on the harder martensite matrix, the toughness, plasticity and formability are increased, the yield strength is ≥1000 MPa, the tensile strength is ≥1400 MPa, the product has the advantages of high strength, wear resistance, low yield strength ratio and easy forming, high strength, easy impact resistance and wear resistance, and low yield strength ratio and easy bending forming. BRIEF DESCRIPTION OF DRAWINGS

[0024] The present application will be further described below in conjunction with the drawings.

[0025] Figure 1 The metallographic structure of Example 1 of the present application. DETAILED DESCRIPTION

[0026] The present application will be further described below in conjunction with the drawings.

[0027] Example 1

[0028] The chemical composition in weight percent is shown in Table 1. The slab heating temperature is 1190℃, and the heating time is 120min. The rough rolling is carried out by R1 and R2; the rough rolling temperature is 1000℃, the finish rolling temperature is 860℃, after the rolling is finished, the laminar flow cooling is carried out, the cooling mode is two-stage cooling, the first stage is from 860℃ to 620℃ at a high speed, the cooling rate is 24℃ / s, the air cooling time is 10s, the cooling is to 580℃, the cooling to 120℃ is carried out at a cooling rate of 47℃ / s and is coiled, after the air cooling to room temperature, the opening, straightening and cutting to size are carried out, and the high-strength steel plate is obtained.

[0029] Example 2

[0030] The chemical composition in weight percent is shown in Table 1. The slab heating temperature is 1200℃, and the heating time is 130min. The rough rolling is carried out by R1 and R2; the rough rolling temperature is 1010℃, the finish rolling temperature is 850℃, after the rolling is finished, the laminar flow cooling is carried out, the cooling mode is two-stage cooling, the first stage is from 850℃ to 630℃ at a high speed, the cooling rate is 22℃ / s, the air cooling time is 11s, the cooling is to 560℃, the cooling to 100℃ is carried out at a cooling rate of 45℃ / s and is coiled, after the air cooling to room temperature, the opening, straightening and cutting to size are carried out, and the high-strength steel plate is obtained.

[0031] Example 3

[0032] The chemical composition in weight percentage is shown in Table 1. The slab heating temperature is 1200℃, and the heating time is 125min. The rough rolling is carried out by R1 and R2; the rough rolling temperature is 1020℃, the finish rolling temperature is 870℃, and after the rolling, the laminar flow cooling is carried out, the cooling mode is two-stage cooling, the first stage is from 870℃ to 610℃ at a high speed with a cooling rate of 28℃ / s, the air cooling time is 12s, and then the temperature is cooled to 530℃, and then the temperature is cooled to 150℃ at a cooling rate of 40℃ / s, and then the high strength steel plate is obtained after the coiling, the opening, the straightening and the cutting to size.

[0033] The chemical composition of the embodiments 1-3 of the present application is shown in Table 1.

[0034] Table 1 Chemical composition (wt%) of embodiments 1-3 of the present application

[0035]

[0036]

[0037] The mechanical properties of the embodiments 1-3 of the present application are shown in Table 2.

[0038] Table 2 Mechanical properties of embodiments 1-3 of the present application

[0039]

[0040] The above described embodiments are only to describe the preferred modes of the present application, and do not limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by the ordinary skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies, comprising: Smelting: Hot metal pretreatment - converter smelting - LF ladle refining - RH vacuum treatment - slab continuous casting - stacking slow cooling; Rolling: Slab heating - high-pressure water descaling - E1R1 roughing rolling - E2R2 roughing rolling - flying shear - high-pressure water descaling - F1~F7 finishing rolling - dense laminar flow cooling - coiling - air cooling - leveling - straightening - edge trimming - length setting; characterized in that: wherein: 1) Smelting and casting The smelting process uses KR desulfurized molten iron and high-quality scrap steel to ensure that the sulfur content of the molten iron entering the converter is ≤0.003%. During converter smelting, self-produced low-sulfur scrap steel is used, and the tapping temperature is ≥1620℃. LF refining and slag formation desulfurization ensure that the sulfur content is ≤0.003%. Ferrochrome and ferroniobium are added during the refining process, and the RH vacuum treatment time is greater than 20 minutes. Ferrotitanium and ferroboron are added during the vacuum treatment process. After vacuum treatment, the molten steel undergoes calcium treatment, and the argon soft blowing time is greater than 12 minutes to fully modify and float the inclusions. During slab continuous casting, the entire process is protected during casting, the superheat is controlled at 15-25℃, and the casting speed is 0.90-1.10m / min. 2) Heating and rolling Heating is performed using a walking beam furnace at a temperature of 1180-1220℃ for ≥120 minutes to ensure uniform temperature. The rolling process consists of roughing and finishing rolling. Roughing is carried out using an R1 two-high horizontal reversible mill and an R2 four-high horizontal reversible mill. Finishing is performed using a seven-stand four-high finishing mill with an initial rolling temperature of 980-1040℃ and a final rolling temperature of 820-880℃. 3) Cooling After rolling, dense laminar flow cooling is carried out. The cooling method is staged cooling. The first stage adopts dense rapid cooling, cooling from the final rolling temperature of 820-880℃ to 600-700℃ at a cooling rate of 20-30℃ / s. Then, air cooling is carried out for 8-12s to cool to 500-600℃. Then, rapid cooling is carried out at a cooling rate of 40-50℃ / s to 100-200℃ for coiling. Finally, air cooling is carried out to room temperature. 4) Leveling, straightening and shearing After the steel coil is leveled and straightened, the plate shape is good and the flatness of the steel plate is ≤5mm / 1m. According to the requirements, the required high-strength steel can be obtained by cutting to the required length and removing the burrs. The chemical composition of the high-strength steel, by weight percentage, is: C: 0.15-0.20%, Si: 0.50-0.70%, Mn: 1.20-1.50%, P: ≤0.012%, S: ≤0.003%, Nb: 0.010-0.030%, Ti: 0.010-0.030%, Cr: 0.10-0.30%, B: 0.0005-0.0020%, Als: 0.020-0.050%, with the balance being Fe and unavoidable impurities.

2. The method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies according to claim 1, characterized in that: The chemical composition of the high-strength steel, by weight percentage, is C: 0.18%, Si: 0.55%, Mn: 1.30%, P: 0.010%, S: 0.003%, Nb: 0.012%, Ti: 0.015%, Cr: 0.20%, B: 0.0008%, Als: 0.030%, with the balance being Fe and unavoidable impurities.

3. The method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies according to claim 1, characterized in that: The chemical composition of the high-strength steel, by weight percentage, is C: 0.17%, Si: 0.60%, Mn: 1.25%, P: 0.009%, S: 0.002%, Nb: 0.020%, Ti: 0.022%, Cr: 0.15%, B: 0.0012%, Als: 0.035%, with the balance being Fe and unavoidable impurities.

4. The method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies according to claim 1, characterized in that: The chemical composition of the high-strength steel, by weight percentage, is C: 0.19%, Si: 0.62%, Mn: 1.42%, P: 0.008%, S: 0.001%, Nb: 0.026%, Ti: 0.030%, Cr: 0.30%, B: 0.0010%, Als: 0.038%, with the balance being Fe and unavoidable impurities.

5. The method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies according to claim 2, characterized in that: The slab is heated to 1190℃ for 120 minutes. Rough rolling is performed using R1 and R2. The finishing rolling starts at 1000℃ and ends at 860℃. After rolling, laminar flow cooling is performed in a two-stage cooling method. The first stage is rapidly cooled to 620℃, followed by air cooling for 10 seconds. The coiling temperature is 120℃. After air cooling to room temperature, the slab is leveled, straightened, and cut to length to obtain the high-strength steel.

6. The method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies according to claim 3, characterized in that: The slab is heated to 1200℃ for 130 minutes. Rough rolling is performed using R1 and R2. The finishing rolling starts at 1010℃ and ends at 850℃. After rolling, laminar flow cooling is performed in a two-stage cooling method. The first stage is rapidly cooled to 630℃, followed by air cooling for 11 seconds. The coiling temperature is 100℃. After air cooling to room temperature, the slab is leveled, straightened, and cut to length to obtain the high-strength steel.

7. The method for producing high-strength steel for easily formable sand and gravel transport vehicle bodies according to claim 4, characterized in that: The slab is heated to 1200℃ for 125 minutes. Rough rolling is performed using R1 and R2. The finishing rolling temperature is 1020℃ at the beginning and 870℃ at the end. After rolling, laminar flow cooling is performed in a two-stage cooling method. The first stage is rapidly cooled to 610℃, and the air cooling time is 12 seconds. The coiling temperature is 150℃. After air cooling to room temperature, the slab is leveled, straightened, and cut to length to obtain the high-strength steel.

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