CN102943204A - Yield strength 1100MPa level engineering machinery non-quenched and tempered hot rolled strip and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of metallurgy and in particular to a yield strength 1100MPa level engineering machinery non-quenched and tempered hot rolled strip and a preparation method thereof. The chemical components of the yield strength 1100MPa level engineering machinery non-quenched and tempered hot rolled strip comprises, by weight, C 0.06-0.12%, Si 0.10-0.30%, Mn 1.60-2.00%, Nb 0.00-0.04%, V 0.00-0.04%, Ti 0.15-0.20%, Ni 0.4-0.80%, Mo 0.20-0.60%, P<0.012%, S<0.01%, and the balance Fe. The yield strength is greater than or equals to 1100MPa, the tensile strength is greater than or equals to 1180MPa, and percentage elongation after fracture is greater than or equals to 11%. The yield strength 1100MPa level engineering machinery non-quenched and tempered hot rolled strip is designed by adopting low carbon components, and by reasonably adding microalloy elements and controlled rolling and controlled cooling technology, production yield strength is greater than or equals to 1100MPa, the tensile strength is greater than or equals to 1180MPa, and percentage elongation after fracture is not lower than 11%. Simultaneously, structure steel strips is provided with good usability, the metallographic structure is bainite/ martensitic structures which are small in grain, cost capable of being reduced no less than 300 yuan per ton, and great economic benefit can be generated.

Description

Non-quenched and tempered hot-rolled strip steel for construction machinery with a yield strength of 1100MPa and its preparation method

technical field

The invention belongs to the technical field of metallurgy, and in particular relates to a non-quenched and tempered hot-rolled steel strip for engineering machinery with a yield strength of 1100 MPa and a preparation method thereof.

Background technique

With the development of the construction machinery industry, the demand for high-strength steel with a strength level above 900MPa is becoming more and more urgent. At the same time, in order to save resources, save energy and protect the environment, it is urgent to develop high-quality steel with higher strength. At present, the strength level of high-strength steel ranges from a yield strength of 900MPa to a yield strength of more than 1100MPa. Generally speaking, the comprehensive requirements for strength, toughness and welding performance are getting higher and higher.

Foreign scholars Koo et al., used low C and high Mn, added Nb, V, Ni, Mo, B and other alloying elements, and prepared medium-thick plate steel with a tensile strength exceeding 930 MPa through controlled rolling and on-line quenching. The microstructure of the steel plate Has a certain proportion of lath martensite. Tamehiro et al. developed hot-rolled high-strength steel with low C and high Mn-Ni-Mo chemical composition, and believed that to make the tensile strength exceed 950MPa, the microstructure of the steel plate must contain more than 90% martensite. Therefore, A large amount of Ni and Mo elements are added in the composition design, and the cost of the alloy is relatively high . Domestic scholars such as Kang Yonglin, Zheng Hua, Yao Liandeng have conducted detailed research on high-strength low-carbon bainite, through the addition of alloying elements such as Nb, Ti, Ni, Mo, B, and the formation of niobium-titanium precipitation to strengthen bonded bainite The phase transformation strengthening of the structure makes the steel have better formability and low temperature toughness. In terms of composition design, a large amount of precious alloying elements such as Nb, Ni, and Mo are used, so the production cost is relatively high. At present, the 900MPa hot-rolled high-strength steel actually produced by SSAB in Sweden, Japan, Finland, and domestic Wuyang, Hunan Iron and Steel, Nangang, Baosteel and other major steel plants have added high value-added Mo, Cr, Alloying elements such as Ni, and the production process is hot rolling + quenching and tempering treatment. The treatment process of the quenching and tempering process is to first heat the hot-rolled steel plate to the high-temperature austenite zone or two-phase zone at a temperature of 850-950°C. Keep warm at this temperature for 30-60 minutes, then quench, and temper the quenched steel plate at 400-600 °C, and the microstructure is mainly tempered martensite. For a high-strength steel plate with a yield strength of 1100MPa,

Zhao Sixin, Jiang Hongsheng, etc. described a heat-treated high-strength steel whose composition characteristics are C: 0.15~0.25%, Si: 0.10~0.50%, Mn: 0.60~1.20%, P≤0.013%, S≤0.003%, Cr: 0.20 ~0.55%, Mo: 0.20~0.70%, Ni: 0.60~2.00%, Nb: 0~0.07%, V: 0~0.07%, B: 0.0006~0.0025%, Al: 0.01~0.08%, Ti: 0.003~ 0.06%, H≤0.00018%, N≤0.0040%, O≤0.0030%, adopt quenching and tempering heat treatment to obtain tempered martensite structure. Pan Hui, Guo Jia, Zhu Guosen, etc. described a heat-treated high-strength steel of 1100-1200MPa, whose chemical composition characteristics are: C: 0.15-0.18%; Si: 0.20-0.25%; Mn: 0.85-1.25%; ~0.60%; Mo: 0.45~0.65%; V: 0.035~0.060%; Nb: 0.015~0.020%; Ni: 0~0.55%; Cu: 0~0.035%; Al: 0.01~0.06%; %; S: ≤0.01%; N: ≤0.008%. The process features are heating the billet to 1150-1250°C, finishing rolling temperature is 860-920°C; coiling temperature is 650-750°C; quenching heating temperature is 880～930℃, holding time is 20～90min, tempering heating temperature is 100～450℃, holding time is more than 90min, slow cooling or air cooling to room temperature. Sun Quanshe, Zhang Aiwen, etc. described an ultra-high-strength steel plate with a yield strength of 1100MPa or more, and its composition characteristics are C 0.10-0.20%; Si≤0.6%; Mn 0.5-2.5%; Al≤0.03%; N 0.001-0.006%; B 0～0.0025%; Ca 0～0.006%; P≤0.015%; S≤0.005%; Ni 0.2～1.2%, Cr 0～0.8%, Cu 0～0.5% and Mo 0～0.6% or Several or more; One or more of Ti 0.01-0.03%, V 0-0.1% and Nb 0.01-0.1%; the process route is online quenching + offline tempering.

To sum up, for ultra-high-strength steel with a strength level above 1100MPa, its composition design and process design are relatively complicated. A more complicated heat treatment process is used to obtain 1100MPa grade high-strength steel with bainite or tempered martensite structure.

Contents of the invention

In view of the above technical problems, the present invention provides a non-quenched and tempered hot-rolled steel strip for engineering machinery with a yield strength of 1100MPa and a preparation method, the purpose of which is to increase the yield strength of the strip steel through reasonable composition design and controlled rolling and cooling process. Higher than 1100MPa, eliminating the complicated heat treatment process, simplifying the production process, and replacing the same level of quenched and tempered hot-rolled steel plate or low-level low-alloy high-strength steel.

The chemical composition of the non-quenched and tempered hot-rolled steel strip for construction machinery with a yield strength of 1100MPa according to the present invention is: C 0.06-0.12%, Si 0.10-0.30%, Mn 1.60-2.00%, Nb 0.00-0.04%, V 0.00~0.04%, Ti 0.15~0.20%, Ni 0.4~0.80%, Mo 0.20~0.60%, P<0.012%, S<0.01%, the balance is iron Fe, its yield strength ≥ 1100MPa, tensile strength ≥ 1180MPa, elongation after break ≥ 11%.

Preparation method of the present invention carries out according to the following steps:

(1) Smelt molten steel according to the set composition and cast it into a slab. The set composition is C0.06~0.12% by weight, Si 0.10~0.30%, Mn 1.60~2.00%, Nb 0.00~0.04%, V0.00 ~0.04%, Ti 0.15~0.20%, Ni 0.4~0.80%, Mo 0.20~0.60%, P<0.012%, S<0.01%, the balance is iron Fe, and the thickness of the slab is 220~250mm;

(2) Heat the billet to 1220~1250°C, carry out rough rolling for 5~7 passes, the starting temperature of rough rolling is 1120~1170°C, and the finishing rolling temperature is 980~1070°C to obtain the intermediate thickness of 38~58mm. Blank;

(3) Perform 5-7 passes of finishing rolling on the intermediate billet, the starting temperature of finishing rolling is 950-1020°C, the finishing rolling temperature is 800-880°C, and the reduction of each pass of finishing rolling is controlled at 15-40%. The strip thickness after finishing rolling is 2~6mm;

(4) After finishing rolling, the steel strip is cooled to 200-400℃ at a speed of 15-60℃/s, and coiled to obtain hot-rolled steel strip products, with yield strength ≥ 1100MPa, tensile strength ≥ 1180MPa, elongation after fracture Length ≥ 11%.

The present invention adopts low-carbon composition design, through reasonable addition of micro-alloy elements and controlled rolling and controlled cooling process, the yield strength is greater than 1100MPa, the tensile strength is greater than 1180MPa, the elongation after fracture is not less than 11%, and has good performance. Structural steel strip, its metallographic structure is bainite/martensite structure with relatively fine grains.

The setting of steel type composition among the present invention has considered following points:

C is effective for strengthening the steel plate, but at the same time reduces its formability and weldability, these properties are essential for its performance, so the carbon content is controlled within the range of low carbon steel; Mn can pass solid solution Strengthening and phase transformation strengthening can effectively improve the performance of steel, but at the same time it will reduce its spot welding ability and electroplating ability. Considering the actual performance requirements of high-strength steel plates, the content of manganese is controlled below 2%; Si and P can improve The strength of the steel, but at the same time will reduce the plating ability of the steel, so their content is controlled very low; in order to increase the yield strength to above 1100MPa on the basis of low carbon steel, a large amount of microalloying element titanium is added. The precipitation strengthening effect of the alloying element titanium effectively improves the performance of the experimental steel, and the addition of Mo alloying elements inhibits the phase transformation of the ferrite structure at high temperature, improves the hardenability of the steel, and is conducive to the formation of low-temperature phase transformation products - bainite , Martensite, etc.

The present invention uses TMCP (Thermo-Mechanical Control Process) to prepare the non-quenched and tempered hot-rolled steel strip with a yield strength of 1100MPa. grains; the finishing rolling temperature is controlled at 800~880°C, so that a large cumulative strain is generated during the rolling process; through rapid cooling after rolling and coiling at a moderate temperature, refined bainite and martensite are obtained. Complex tissue;

The present invention provides a new production process route for non-quenched and tempered hot-rolled strip steel with a yield strength of 1100 MPa, cancels the current quenched and tempered heat treatment process for producing this level of steel, and realizes the reduction of the process. The structure of the product is Bainite/martensite structure, the refined bainite/martensite structure makes the material have high mechanical properties and good plasticity. At the same time, due to the low carbon content in the composition design, the welding performance of the material is greatly improved. Big improvement.

Compared with the heat-treated high-strength steel of the same strength level, the hot-rolled steel strip of the present invention has the following advantages:

(1) Since the hot-rolled steel strip of the present invention cancels the quenching and tempering heat treatment process, the reduction of the process is realized, and the production cost is greatly reduced. By adopting the hot-rolled steel strip of the present invention, the cost can be reduced by no less than 300 yuan per ton. Can produce great economic benefits.

(2) The composition design of the hot-rolled steel strip of the present invention adopts a low-carbon composition route. On the basis of ensuring the mechanical performance requirements, the product has better welding performance, effectively reduces the welding preheating temperature, and reduces the cost and difficulty of welding.

Description of drawings

FIG. 1 is a metallographic structure diagram of a hot-rolled steel strip product prepared in Example 1 of the present invention.

Detailed ways

The rolling mill adopted in the embodiment of the present invention is a 2250mm hot continuous rolling mill.

Example 1

Molten steel is smelted in a 150-ton converter according to the set composition, and continuously cast into billets. The set composition is C 0.06%, Si 0.20%, Mn 1.60%, Nb 0.02%, V 0.04%, Ti 0.15% by weight , Ni 0.4%, Mo 0.20%, P<0.012%, S<0.01%, the balance is iron Fe, and the thickness of the slab is 220mm.

The cast slab was heated to 1250°C for rough rolling, the rough rolling process was 5 passes, the rough rolling start temperature was 1170°C, and the rough rolling finish rolling temperature was 1070°C to obtain an intermediate slab with a thickness of 38mm.

Finish rolling of the intermediate billet, the finishing rolling process is 7 passes, the starting temperature of the finishing rolling is 980°C, the temperature of the second rolling is 950°C, the temperature of the third rolling is 930°C, the temperature of the fourth rolling is 890°C, and the temperature of the fifth rolling is 850°C ℃, the sixth rolling temperature is 820 ℃, the final rolling temperature is 800 ℃, the reduction of each pass of finishing rolling is controlled at 15~40%, and the strip thickness after finishing rolling is 2mm.

After finishing rolling, it is water-cooled to 300°C at a speed of 60°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.06%, Si 0.20%, Mn 1.60%, Nb 0.02%, V 0.04%, Ti 0.15 %, Ni 0.4%, Mo 0.20%, P<0.012%, S<0.01%, and the balance is iron Fe. The metallographic structure of the finished hot-rolled strip steel is shown in Figure 1, and the structure is fine bainite/ Martensite, the mechanical performance test results are: yield strength 1150MPa, tensile strength 1250MPa, elongation after fracture 12%, cold bending test (B=35, d=2a) qualified.

Example 2

The preparation method and composition of the slab are the same as in Example 1, and the thickness of the slab is 250mm.

The rough rolling process was the same as in Example 1, and an intermediate billet with a thickness of 58 mm was obtained.

The intermediate billet is finished rolling, the finishing rolling process is 6 passes, the starting temperature of the finishing rolling is 950°C, the temperature of the second rolling is 930°C, the temperature of the third rolling is 910°C, the temperature of the fourth rolling is 880°C, and the temperature of the fifth rolling is 850°C ℃, the finish rolling temperature is 830 ℃, the reduction in each pass of finish rolling is controlled at 15~40%, and the strip thickness after finish rolling is 6mm.

After finishing rolling, it is water-cooled to 400°C at a speed of 35°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.06%, Si 0.20%, Mn 1.60%, Nb 0.02%, V 0.04%, Ti 0.15 %, Ni 0.4%, Mo 0.20%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1100MPa, tensile strength 1185MPa, elongation after fracture The rate is 11.5%, and the cold bending test (B=35, d=2a) is qualified.

Example 3

The preparation method and composition of the slab are the same as in Example 1, and the thickness of the slab is 240mm.

The rough rolling process was the same as in Example 1, and an intermediate billet with a thickness of 45 mm was obtained.

The intermediate billet is finished rolling, the finishing rolling process is 5 passes, the finishing rolling temperature is 1020°C, the second rolling temperature is 980°C, the third rolling temperature is 920°C, the fourth rolling temperature is 900°C, and the final rolling temperature is 880°C ℃, the reduction in each pass of finish rolling is controlled at 15~40%, and the strip thickness after finish rolling is 4mm.

After finishing rolling, it is water-cooled to 200°C at a speed of 15°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.06%, Si 0.20%, Mn 1.60%, Nb 0.02%, V 0.04%, Ti 0.15 %, Ni 0.4%, Mo 0.20%, P<0.012%, S<0.01%, and the balance is the finished hot-rolled steel strip of iron Fe. The corresponding mechanical performance test results are: yield strength 1120MPa, tensile strength 1190MPa, after fracture The elongation is 12%, and the cold bending test (B=35, d=2a) is qualified.

Example 4

Molten steel is smelted in a 150-ton converter according to the set composition, and continuously cast into a billet. The composition is C 0.08%, Si 0.10%, Mn 2.00%, Nb 0.00%, V0.00%, Ti 0.20%, Ni 0.80%, Mo 0.60%, P<0.012%, S<0.01%, the balance is iron Fe, and the thickness of the slab is 220mm.

The cast slab was heated to 1220°C for rough rolling, the rough rolling process was 7 passes, the rough rolling start temperature was 1150°C, and the final rolling temperature was 1000°C to obtain an intermediate slab with a thickness of 38mm.

Finish rolling of the intermediate billet, the finishing rolling process is 5 passes, the finishing rolling temperature is 1020°C, the second rolling temperature is 970°C, the third rolling temperature is 940°C, the fourth rolling temperature is 910°C, and the final rolling temperature is 880°C ℃, the reduction in each pass of finish rolling is controlled at 15~40%, and the strip thickness after finish rolling is 2mm.

After finishing rolling, it is water-cooled to 400°C at a speed of 60°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.08%, Si 0.10%, Mn 2.00%, Nb 0.00%, V 0.00%, Ti 0.20 %, Ni 0.80%, Mo 0.60%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1110MPa, tensile strength 1190MPa, elongation after fracture The rate is 11%, and the cold bending test (B=35, d=2a) is qualified.

Example 5

The preparation method and composition of the slab are the same as in Example 4, and the thickness of the slab is 230mm.

The rough rolling process was the same as in Example 4, and an intermediate billet with a thickness of 45 mm was obtained.

Finish rolling of the intermediate billet, the finishing rolling process is 6 passes, the starting temperature of the finishing rolling is 970°C, the temperature of the second rolling is 950°C, the temperature of the third rolling is 920°C, the temperature of the fourth rolling is 880°C, and the temperature of the fifth rolling is 840°C ℃, the final rolling temperature is 820 ℃, the reduction of each pass of finishing rolling is controlled at 15~40%, and the strip thickness after finishing rolling is 4mm.

After finishing rolling, it is water-cooled to 350°C at a speed of 30°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.08%, Si 0.10%, Mn 2.00%, Nb 0.00%, V 0.00%, Ti 0.20 %, Ni 0.80%, Mo 0.60%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1100MPa, tensile strength 1180MPa, elongation after fracture The elongation rate is 11.5%, and the cold bending test (B=35, d=2a) is qualified.

Example 6

The preparation method and composition of the slab are the same as in Example 4, and the thickness of the slab is 240mm.

The rough rolling process was the same as in Example 4, and an intermediate billet with a thickness of 58 mm was obtained.

The intermediate billet is subjected to finish rolling, the finish rolling process is 5 passes, the finish rolling start temperature is 950°C, the second rolling temperature is 930°C, the third rolling temperature is 900°C, the fourth rolling temperature is 850°C, and the final rolling temperature is 800°C ℃, the reduction in each pass of finish rolling is controlled at 15~40%, and the strip thickness after finish rolling is 6mm.

After finishing rolling, it is water-cooled to 200°C at a speed of 15°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.08%, Si 0.10%, Mn 2.00%, Nb 0.00%, V 0.00%, Ti 0.20 %, Ni 0.80%, Mo 0.60%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1100MPa, tensile strength 1200MPa, elongation after fracture The elongation rate is 11.5%, and the cold bending test (B=35, d=2a) is qualified.

Example 7

Molten steel is smelted in a 150-ton converter according to the set composition, and continuously cast into a billet. The composition is C 0.12%, Si 0.30%, Mn 1.80%, Nb 0.04%, V 0.02%, Ti 0.18%, Ni 0.60%, Mo 0.40%, P<0.012%, S<0.01%, the balance is iron Fe, and the thickness of the slab is 240mm.

The cast slab was heated to 1240°C for rough rolling, the rough rolling process was 6 passes, the rough rolling start temperature was 1120°C, and the final rolling temperature was 980°C to obtain an intermediate slab with a thickness of 42mm.

The intermediate billet is finished rolling, the finishing rolling process is 7 passes, the starting temperature of the finishing rolling is 1000°C, the temperature of the second rolling is 970°C, the temperature of the third rolling is 940°C, the temperature of the fourth rolling is 900°C, and the temperature of the fifth rolling is 860 ℃, the sixth rolling temperature is 820 ℃, the final rolling temperature is 800 ℃, the reduction of each pass of finishing rolling is controlled at 15~40%, and the strip thickness after finishing rolling is 2mm.

After finishing rolling, it is water-cooled to 400°C at a speed of 60°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.12%, Si 0.30%, Mn 1.80%, Nb 0.04%, V 0.02%, Ti 0.18 %, Ni 0.60%, Mo 0.40%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1120MPa, tensile strength 1190MPa, elongation after fracture The elongation rate is 12%, and the cold bending test (B=35, d=2a) is qualified.

Example 8

The preparation method and composition of the slab are the same as in Example 4, and the thickness of the slab is 240mm.

The rough rolling process was the same as in Example 4, and an intermediate billet with a thickness of 48 mm was obtained.

Finish rolling of the intermediate billet, the finishing rolling process is 5 passes, the finishing rolling temperature is 1020°C, the second rolling temperature is 970°C, the third rolling temperature is 940°C, the fourth rolling temperature is 910°C, and the final rolling temperature is 880°C ℃, the reduction in each pass of finish rolling is controlled at 15~40%, and the strip thickness after finish rolling is 5mm.

After finishing rolling, it is water-cooled to 300°C at a speed of 30°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.12%, Si 0.30%, Mn 1.80%, Nb 0.04%, V 0.02%, Ti 0.18 %, Ni 0.60%, Mo 0.40%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1130MPa, tensile strength 1190MPa, elongation after fracture The elongation rate is 11.5%, and the cold bending test (B=35, d=2a) is qualified.

Example 9

The preparation method and composition of the slab are the same as in Example 4, and the thickness of the slab is 240mm.

The rough rolling process was the same as in Example 4, and an intermediate billet with a thickness of 38 mm was obtained.

Finish rolling of the intermediate billet, the finishing rolling process is 6 passes, the starting temperature of the finishing rolling is 980°C, the temperature of the second rolling is 950°C, the temperature of the third rolling is 910°C, the temperature of the fourth rolling is 880°C, and the temperature of the fifth rolling is 860°C ℃, the finish rolling temperature is 840 ℃, the reduction of each pass of finish rolling is controlled at 15~40%, and the strip thickness after finish rolling is 2mm.

After finishing rolling, it is water-cooled to 200°C at a speed of 40°C/s, and coiled by a coiler to obtain components by weight percentage of C 0.12%, Si 0.30%, Mn 1.80%, Nb 0.04%, V 0.02%, Ti 0.18 %, Ni 0.60%, Mo 0.40%, P<0.012%, S<0.01%, the balance is the finished hot-rolled steel strip of iron Fe, the mechanical property test results are: yield strength 1150MPa, tensile strength 1200MPa, elongation after fracture The elongation rate is 12%, and the cold bending test (B=35, d=2a) is qualified.

Claims (2)

1. a yield strength 1100MPa level non-quenched and tempered state hot rolled strip for engineering machinery, it is characterized in that chemical composition is by weight percentage: C 0.06 ~ 0.12%, and Si 0.10 ~ 0.30%, Mn 1.60 ~ 2.00%, and Nb 0.00 ~ 0.04%, V0.00 ~ 0.04%, Ti0.15 ~ 0.20%, Ni0.4 ~ 0.80%, Mo0.20 ~ 0.60%, P<0.012%, S<0.01%, surplus is iron Fe, its yield strength >=1100MPa, tensile strength >=1180MPa, elongation after fracture >=11%.

2. the preparation method of non-quenched and tempered state hot rolled strip for a yield strength 1100MPa level engineering machinery is characterized in that carrying out according to following steps:

(1) by the set component smelting molten steel and cast strand, set component is C0.06 ~ 0.12% by weight percentage, and Si 0.10 ~ 0.30%, Mn 1.60 ~ 2.00%, Nb 0.00 ~ 0.04%, and V 0.00 ~ 0.04%, and Ti 0.15 ~ 0.20%, Ni 0.4 ~ 0.80%, Mo 0.20 ~ 0.60%, P<0.012%, S<0.01%, surplus is iron Fe, and slab thickness is 220 ~ 250mm;

(2) strand is heated to 1220 ~ 1250 ℃, carries out 5 ~ 7 passage roughing, the roughing start rolling temperature is 1120 ~ 1170 ℃, and finishing temperature is 980 ~ 1070 ℃, the intermediate blank that acquisition thickness is 38 ~ 58mm;

(3) intermediate blank is carried out to 5 ~ 7 passage finish rolling, the finish rolling start rolling temperature is 950 ~ 1020 ℃, and finishing temperature is 800 ~ 880 ℃, and the finish rolling draught per pass is controlled at 15 ~ 40%, and after finish rolling, belt steel thickness is 2 ~ 6mm;

(4) after finish rolling, with the speed of 15 ~ 60 ℃/s, will be with steel to be cooled to 200 ~ 400 ℃, and be batched, the coil of strip product after batching is directly used, its yield strength >=1100MPa, tensile strength >=1180MPa, elongation after fracture >=11%.

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