Q690MPa-grade high-strength wide and thin steel plate and production method thereof

Abstract

The invention relates to the technical field, in particular to a Q690MPa-grade high-strength wide and thin steel plate and a production method thereof.The production method specifically comprises the steps that production scheduling is conducted, specifically, at least three transition blanks with the width not smaller than that of a to-be-rolled blank are arranged so as to homogenize a load roll shape, then heating, rolling by a steekle mill, hot straightening, quenching and tempering heat treatment, and carrying out third-time strong cold straightening on the steel plate subjected to quenching and tempering heat treatment. According to the production method provided by the invention, batch production of high-strength wide thin steel plates with the thickness of 4mm and the width of 2800mm can be realized, the problems that the width of a hot continuous rolling mill is relatively narrow and the difficulty of rolling the high-strength steel with the thickness of 4mm by a heavy and medium plate mill is high are solved, a customer can conveniently carry out integrated workpiece processing, and a tailor-welding procedure is reduced.

Description

Technical Field

[0001] The invention relates to the technical field, and in particular to a Q690MPa grade high-strength wide thin steel plate and a production method thereof. Background Art

[0002] Q690MPa high-strength steel plates are widely used in hydraulic supports, port machinery, cranes, coal mining machinery, excavators and other engineering machinery and equipment. In recent years, with the development trend of lightweight and large-scale engineering machinery, the demand for Q690MPa high-strength steel wide thin plates has increased. For high-strength steel plates with specifications of ≤4mm, it is difficult to produce them using medium and thick plate rolling mills, the rolling temperature drops quickly, and the plate shape control is poor. It is currently difficult to supply them in batches. If hot rolling production lines are used, they have the advantages of uniform rolling temperature, good plate shape control, and high rolling efficiency. However, due to the current limitation of the width of hot rolling mills, only steel plates with a width of less than 2200mm can be produced. For ultra-wide structural components, only welding can be used, and one-piece processing is impossible.

[0003] Based on the above, the present invention provides a Q690MPa grade high-strength wide thin steel plate and a production method thereof, which can be applied in a medium and thick plate rolling mill to achieve batch production of high-strength wide thin steel plates with a thickness of 4mm and a width of 2800mm. Summary of the invention

[0004] In view of the above technical problems, the present invention overcomes the shortcomings of the prior art and provides a Q690MPa grade high-strength wide thin steel plate and a production method thereof, thereby realizing mass production of high-strength wide thin steel plates with a thickness of 4mm and a width of 2800mm.

[0005] In a first aspect, the present invention provides a method for producing a Q690MPa grade high-strength wide thin steel plate, comprising the following steps:

[0006] (1) Production scheduling: Arrange production within the rolling tonnage of 300-700 working rolls, and arrange at least 3 transition billets with a width not less than the width of the billet to be rolled to uniformly load the roll shape and improve rolling stability;

[0007] (2) Heating: The steel billet is heated to 1220-1250°C, the furnace time is 10-15 min / cm, and the soaking time is not less than 1.8 min / cm. In the process of rolling thin-gauge steel plates using medium and thick plate rolling mills, the temperature drops quickly, and the rolling is difficult. Therefore, the heating temperature is relatively high, and the furnace time is extended to ensure the uniformity of the core and surface temperature of the slab and reduce the difficulty of rolling;

[0008] (3) Steckel mill rolling: Conventional rolling is adopted, with 11 passes. In order to control the temperature drop during rolling, descaling is performed only in the first two passes. Reducing the number of descaling passes can minimize the temperature drop. The reduction rate of the last three passes does not exceed 20%, which effectively avoids the generation of waves in the rolled piece.

[0009] (4) Hot straightening: Perform at least one hot straightening on the rolled steel plate to improve the rolled plate shape, thereby improving the plate shape after quenching and allowing re-straightening, which lays a good foundation for the subsequent quenching process;

[0010] (5) Quenching and tempering heat treatment: The steel plate after hot straightening is subjected to offline heat treatment, including quenching at 900-920°C for 5-10 min and tempering at 590-610°C for 10-20 min;

[0011] (6) Strong cold straightening: The steel plate after quenching and tempering heat treatment is subjected to three strong cold straightening to meet the plate shape requirements of wide and thin plates.

[0012] Optionally, in the heating step, the uniformity of the steel temperature does not exceed 10°C, and the uniformity of the steel temperature is controlled to ensure the uniformity of the slab temperature before rolling.

[0013] Optionally, the steel plate after strong cold straightening has a thickness of 4 mm and a width of 2800 mm.

[0014] Optionally, the yield strength of the steel plate after strong cold straightening is not less than 690 MPa, the tensile strength is 770-940 MPa, and the elongation is not less than 10%.

[0015] Optionally, the flatness of the steel plate after strong cold straightening meets 5mm / m and 10mm / 2m, that is, the maximum flatness deviation within a length of 1m does not exceed 5mm, and the maximum flatness deviation within a length of 2m does not exceed 10mm.

[0016] The second invention, the present invention also provides a Q690MPa grade high-strength wide thin steel plate, which is obtained by producing by any production method described in the first aspect.

[0017] The beneficial effects of the present invention are:

[0018] (1) The production method provided by the present invention can realize the mass production of high-strength wide thin steel plates with a thickness of 4 mm and a width of 2800 mm, which makes up for the problem that the width of the hot rolling mill is narrow and the medium and thick plate mill is difficult to roll 4 mm high-strength steel, facilitates customers to carry out integrated workpiece processing, and reduces the welding process;

[0019] (2) The present invention breaks through the technical bottleneck in the production process of wide and thin plates in the prior art by optimizing the combination of process parameters, realizes the unity of high strength and excellent plate shape, and provides a reliable technical solution for the large-scale production of high-strength wide and thin steel plates. The method adopted has a simple production process and a wide adjustable range of process parameters, which is easy to implement in steel mills. DETAILED DESCRIPTION

[0020] Example 1

[0021] This embodiment provides a method for producing a Q690MPa grade high-strength wide thin steel plate, which specifically includes the following steps:

[0022] (1) Production scheduling: 150*2875mm billet is used to roll 4*2800mm specification steel plate, which is arranged to be rolled on a working roll with a rolling capacity of 300 tons. Before loading the furnace, 3 Q345B transition billets are arranged, and the rolling thickness is 6*2800mm.

[0023] (2) Heating: Heating temperature 1239°C, furnace time 11.2 min / cm, soaking time 2.0 min / cm, steel temperature uniformity 5°C.

[0024] (3) Steckel rolling: Conventional rolling is adopted, with 11 rolling passes. Descaling is performed in the first two rolling passes, and the reduction rate of the last three rolling passes does not exceed 20%.

[0025] (4) Hot straightening: After rolling, the entire rolled piece is straightened in one pass.

[0026] (5) Quenching and tempering heat treatment: After rolling, offline heat treatment is carried out, including quenching temperature of 900℃, quenching holding time of 10min; tempering temperature of 590℃, tempering holding time of 20min.

[0027] (6) Strong cold straightening: The steel plate after quenching and tempering heat treatment is subjected to strong cold straightening three times.

[0028] Example 2

[0029] This embodiment provides a method for producing a Q690MPa grade high-strength wide thin steel plate, which specifically includes the following steps:

[0030] (1) Production scheduling: 150*2875mm billet is used to roll 4*2800mm specification steel plate, which is arranged to be rolled on a working roll with a rolling capacity of 500 tons. Before loading the furnace, 5 S355J2 transition billets are arranged, and the rolling thickness is 5*2820mm.

[0031] (2) Heating: Heating temperature 1247°C, furnace time 13 min / cm, soaking time 2.3 min / cm, steel temperature uniformity 6°C.

[0032] (3) Steckel rolling: Conventional rolling is adopted, with 11 rolling passes. Descaling is performed in the first two rolling passes, and the reduction rate of the last three rolling passes does not exceed 20%.

[0033] (4) Hot straightening: After rolling, the entire rolled piece is straightened three times.

[0034] (5) Quenching and tempering heat treatment: After rolling, offline heat treatment is carried out, including quenching temperature of 910℃, quenching holding time of 5min; tempering temperature of 600℃, tempering holding time of 15min.

[0035] (6) Strong cold straightening: The steel plate after quenching and tempering heat treatment is subjected to strong cold straightening three times.

[0036] Example 3

[0037] This embodiment provides a method for producing a Q690MPa grade high-strength wide thin steel plate, which specifically includes the following steps:

[0038] (1) Production scheduling: 150*2875mm billets are used to roll 4*2800mm steel plates. The working rolls are arranged to roll 700 tons. Before loading the furnace, 3 AH36 transition billets are arranged. The rolling thickness is 5*2800mm.

[0039] (2) Heating: Heating temperature 1230°C, furnace time 15 min / cm, soaking time 2.6 min / cm, steel temperature uniformity 2°C.

[0040] (3) Steckel rolling: Conventional rolling is adopted, with 11 rolling passes. Descaling is performed in the first two rolling passes, and the reduction rate of the last three rolling passes does not exceed 20%.

[0041] (4) Hot straightening: After rolling, the entire rolled piece is straightened three times.

[0042] (5) Quenching and tempering heat treatment: After rolling, offline heat treatment is carried out, including quenching temperature of 920℃, quenching holding time of 5min; tempering temperature of 610℃, tempering holding time of 20min.

[0043] (6) Strong cold straightening: The steel plate after quenching and tempering heat treatment is subjected to strong cold straightening three times.

[0044] The tensile properties of the steel plates obtained in each example were tested according to the room temperature tensile test method for metal materials in GB / T228-2002. The performance test results are shown in Table 1.

[0045] The unevenness of the steel plates in each example was measured using 1m and 2m levels, and the data are shown in Table 1.

[0046] Table 1

[0047]

[0048] It can be seen from Table 1 above that the mechanical properties of the steel plate obtained by the production method of the Q690MPa grade high-strength wide and thin steel plate of the present invention meet the standard requirements, and the unevenness meets 5mm / m and 10mm / 2m.

[0049] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for producing Q690MPa grade high-strength wide thin steel plate, characterized in that: The following steps are involved: (1) Production scheduling: Arrange production within the rolling tonnage of 300-700 working rolls, and arrange at least 3 transition billets with a width not less than the width of the billet to be rolled; (2) Heating: Heat the steel billet to 1220-1250°C, with a furnace time of 10-15 min / cm and a soaking time of not less than 1.8 min / cm; (3) Steckel mill rolling: 11 passes are used, with descaling only in the first two passes and the reduction ratio in the last three passes not exceeding 20%; (4) Hot straightening: perform at least one hot straightening on the rolled steel plate; (5) Quenching and tempering heat treatment: The steel plate after hot straightening is subjected to offline heat treatment, including quenching at 900-920°C for 5-10 min and tempering at 590-610°C for 10-20 min; (6) Strong cold straightening: The steel plate after quenching and tempering heat treatment is subjected to three strong cold straightenings.

2. The production method according to claim 1, characterized in that During the heating step, the uniformity of the steel temperature does not exceed 10°C.

3. The production method according to claim 1, characterized in that The steel plate after strong cold straightening has a thickness of 4mm and a width of 2800mm.

4. The production method according to claim 1, characterized in that The yield strength of the steel plate after strong cold straightening is not less than 690MPa, the tensile strength is 770-940MPa, and the elongation is not less than 10%.

5. The production method according to claim 1, characterized in that: The maximum flatness deviation of the steel plate after strong cold straightening shall not exceed 5mm within a length of 1m, and the maximum flatness deviation shall not exceed 10mm within a length of 2m.

6. A Q690MPa grade high-strength wide thin steel plate produced by the method according to any one of claims 1 to 6.

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