阅读说明：本技术 一种低锰b280vk碳素结构钢冷轧板的罩退及平整工艺 (Cover annealing and flattening process of low-manganese B280VK carbon structural steel cold-rolled sheet ) 是由 胡洪林 马孝娟 卢鹏程 于 2021-06-24 设计创作，主要内容包括：本发明公开了一种低锰B280VK碳素结构钢冷轧板的罩退及平整工艺,其包括如下步骤：1)在氮气和氢气保护的情况下将B280VK碳素钢冷轧卷以100-200℃/小时加热速度高速加热2-3小时到退火炉温工艺温度；2)将加热到冷点工艺温度600-620℃的B280VK碳素钢冷轧卷在氮气和氢气保护的情况下保温7-9小时进行退火；3)B280VK钢冷轧卷带罩2小时,在氮气和氢气保护的情况下随炉风冷冷却到560℃；4)停止风冷,吊离加热罩,B280VK碳素钢自然冷却到105℃出炉,时间在16-18小时；5)B280VK碳素钢退火后采用1.7%-2.6%的延伸率进行平整。(The invention discloses a cover annealing and flattening process of a low-manganese B280VK carbon structural steel cold-rolled sheet, which comprises the following steps: 1) under the protection of nitrogen and hydrogen, the B280VK carbon steel cold-rolled coil is heated at a high speed for 2-3 hours at a heating speed of 100-200 ℃/hour to the process temperature of the annealing furnace; 2) b280VK carbon steel cold-rolled coils heated to the cold point process temperature of 600-620 ℃ are subjected to heat preservation for 7-9 hours for annealing under the protection of nitrogen and hydrogen; 3) b280VK steel cold rolling strip cover for 2 hours, and furnace air cooling to 560 ℃ under the protection of nitrogen and hydrogen; 4) stopping air cooling, lifting off the heating cover, naturally cooling the B280VK carbon steel to 105 ℃, and discharging for 16-18 hours; 5) b280VK carbon steel is annealed and then flattened by the elongation of 1.7-2.6%.)

1. A cover annealing and flattening process of a low-manganese B280VK carbon structural steel cold-rolled sheet is characterized by comprising the following steps:

1) under the protection of nitrogen and hydrogen, the B280VK carbon steel cold-rolled coil is heated at a high speed for 2-3 hours at a heating speed of 100-200 ℃/hour to the process temperature of the annealing furnace;

2) b280VK carbon steel cold-rolled coils heated to the cold point process temperature of 600-620 ℃ are subjected to heat preservation for 7-9 hours for annealing under the protection of nitrogen and hydrogen;

3) b280VK steel cold rolling strip cover for 2 hours, and furnace air cooling to 560 ℃ under the protection of nitrogen and hydrogen;

4) stopping air cooling, lifting off the heating cover, naturally cooling the B280VK carbon steel to 105 ℃, and discharging for 16-18 hours;

5) b280VK carbon steel is annealed and then flattened by the elongation of 1.7-2.6%.

Technical Field

The invention relates to a cover annealing and flattening process of a low-manganese B280VK carbon structural steel cold-rolled sheet.

Background

The final chemical components of patent CN201210200748.7 are as follows by mass percent: c: 0.145-0.185%, 0.05-0.15% of Si, 0.55-0.65% of Mn, less than or equal to 0.025% of P, less than or equal to 0.015% of S, 0.013-0.023% of Als, less than or equal to 0.004% of N, no microalloy element is added, the yield strength is improved by improving the content of C and reducing the content of Si, Mn and P through controlling the steelmaking process, the steel for the automobile plate structure with the yield strength of more than 280MPa and the elongation of more than 30% is produced through improving the steelmaking, hot rolling and cold rolling continuous annealing processes, the toughness is matched well, the cost is low, and the mechanical property indexes of the finished product are as follows: the yield strength is about 300MPa, the tensile strength is about 430MPa, and the elongation is more than or equal to 30 percent.

The patent CN201410742582.0 comprises the following chemical components in percentage by mass: c: 0.07-0.08%; mn: 0.8 to 1.0 percent; si is less than or equal to 0.05 percent; 0.015-0.025% of P; s is less than or equal to 0.010 percent; 0.04-0.05% of Als, 0.0020-0.0040% of N, 0.035-0.045% of Nb and less than or equal to 0.006% of O.

Patent CN201710863495.4 discloses a rolling process of a steel B280VK continuous casting billet for automobile structures, which comprises the following steps: (1) heating time: the heating time of the continuous casting plate blank is more than 160 minutes, and the head-tail temperature difference of the plate blank is less than 20 ℃; (2) the initial rolling temperature of the hot-rolled plate blank is 1180 +/-30 ℃, the final rolling temperature of the last pass of the hot continuous rolling is 860 +/-20 ℃, the coiling temperature of the strip steel is 580 +/-20 ℃, and the warping and scratching caused by hot rolling are eliminated; (3) cold rolling reduction: the reflectivity of the plate surface is more than or equal to 60 ℃, and the purging pressure is more than 0.5 MPa; (4) annealing requirement: the temperature of the bell-type annealing furnace is 600 +/-10 ℃, the heating temperature is raised to 430 ℃, and the heating rate is 30-40 ℃/h; (5) the flattening process comprises the following steps: the elongation percentage mode is preferably selected, and the rolling force mode is preferably adopted, and the rolling force range is 2600KN to 3200 KN. The invention adopts the measures of optimizing the process and improving the equipment, reduces the internal defect rate of the continuous casting billet of the steel B280VK for the automobile structure to a lower level, and improves the quality of the continuous casting billet of the steel B280VK for the automobile structure.

The cold rolled carbon structural steel B280VK is mainly used for manufacturing automobile interior structural parts and supporting parts. The cold-rolled steel strip for the carbon structure is steel which is obtained by adding elements such as Mn, Si, V, Ti and the like into low-carbon steel and improving the strength by solid solution strengthening and incomplete annealing, has the typical marks of B280VK, B340LA and the like, has the characteristics of high strength, high yield ratio, high rigidity and low plasticity, and is widely applied to materials of automobile reinforcements and structural parts. Solid solution strengthening is a method of adding a substitution type solid solution element such as P, Si, Mn, or a gap type solid solution element such as C, N to steel to obtain a strengthened matrix. The C — Mn solid solution strengthening method is developed to produce the structural cold-rolled steel strip B280VK, in which C, N is the cheapest solid solution strengthening element, and it acts as a strengthening element by forming an interstitial solid solution or a substitutional solid solution with Mn, P, Si, etc., but it exists in a solid solution state in the steel to drastically decrease the r value, and also causes aging to deteriorate workability of the steel, increase yield point, yield elongation, etc., and therefore, the content thereof should be controlled, and in this design, ω (C): 0.06% -0.10%, ω (N): less than or equal to 0.006 percent. Mn: the Mn has the effect of solid solution strengthening, does not influence the recrystallization temperature of the steel, but has the effect on the occurrence rate of recrystallization crystal nuclei. And an increase in Mn will deteriorate the r value. ω (Mn) in this design: 1.00 to 1.10 percent. P, S: harmful elements are reduced as much as possible. P is the most effective element for improving the strength of steel, but an increase in P in steel increases the brittleness of steel, decreases elongation, plastic strain ratio, and the like. The design is that omega (S) is less than or equal to 0.010 percent and omega (P) is less than or equal to 0.025 percent.

The low Mn content can cause the product to have low strength, particularly low yield strength, and spot welding pits can be generated when the surface of the steel plate is soft, so that the production efficiency is influenced, and therefore, a novel carbon structural steel cold-rolled steel coil bell-type furnace annealing process and a flattening process are needed to make up for the defects of the prior art.

Disclosure of Invention

The invention aims to develop a cover annealing and flattening process of a low-manganese B280VK carbon structural steel cold-rolled sheet, which is to perform annealing treatment on a coiled cold-rolled sheet and perform flattening treatment after annealing to ensure the yield strength of the steel sheet.

In order to achieve the purpose, the technical scheme of the invention is that the cover annealing and flattening process of the low-manganese B280VK carbon structural steel cold-rolled sheet comprises the following steps:

1) under the protection of nitrogen and hydrogen, the B280VK carbon steel cold-rolled coil is heated at a high speed for 2-3 hours at a heating speed of 100-200 ℃/hour to the process temperature of the annealing furnace;

2) b280VK carbon steel cold-rolled coils heated to the cold point process temperature of 600-620 ℃ are subjected to heat preservation for 7-9 hours for annealing under the protection of nitrogen and hydrogen;

3) the steel cold-rolled strip cover of B280VK steel is cooled to 560 ℃ with furnace air cooling under the protection of nitrogen and hydrogen for 2 hours.

4) Stopping air cooling, lifting off the heating cover, naturally cooling the B280VK carbon steel to 105 ℃, and discharging for 16-18 hours.

5) B280VK carbon steel is annealed and then flattened by the elongation of 1.7-2.6%.

The method is characterized in that the B280VK carbon steel cold-rolled coil is heated at a high speed of 200 ℃/hour at the heating speed of 100-; and (3) annealing the cold-rolled B280VK carbon steel product at the steel coil cold point process temperature of 600-620 ℃ and under the high temperature condition of nitrogen and hydrogen protection for 7-9 hours to keep full recrystallization at the high temperature and then cooling to 560 ℃ along with furnace air cooling. B280VK carbon steel is flattened by adopting the elongation percentage of 1.7-2.6% after being annealed so as to ensure the yield strength of the steel plate.

The bell-type furnace annealing process can better realize the annealing and leveling process for improving the performance of the B280VK carbon structural steel cold-rolled sheet, the metallographic structure of the B280VK carbon steel is cake-shaped ferrite, the structure is uniform, cementite particles are dispersed and distributed in the ferrite, the yield strength of the product is averagely increased by 15-25MPa, the elongation after fracture is reduced by 1% -2%, and a certain safety space is provided. By adopting the process, the B280VK carbon structural steel cold-rolled steel coil meeting the high yield strength requirement of downstream users can be produced by adopting larger flat elongation under the condition of limited annealing time on the premise of low manganese content, and a new way for producing the B280VK carbon structural steel cold-rolled coil is opened up.

Detailed Description

A cover annealing and leveling process for a low-manganese B280VK carbon structural steel cold-rolled plate comprises the steps of placing a B280VK carbon steel cold-rolled coil in a cover furnace, arranging a heating cover, filling nitrogen in the inner cover for purging, then introducing nitrogen and hydrogen, starting to heat at a high speed of 100 plus materials at a heating speed of 200 ℃/h for 2-3 h, carrying out annealing at a heat preservation temperature of 600 plus materials at 620 ℃ for 7-9 h under the protection of nitrogen and hydrogen, cooling the B280VK cold-rolled coil with the cover to 560 ℃ along with furnace air cooling under the protection of nitrogen and hydrogen, stopping air cooling, hanging away the heating cover, naturally cooling the B280VK cold-rolled coil from 560 ℃ to 105 ℃, and taking out of the furnace. B280VK carbon steel is annealed and then flattened by the elongation of 1.7-2.6%.