800 MPa grade high-strength plastic product Q&P steel plate and preparation method thereof

Abstract

The invention discloses a 800 MPa grade high-strength plastic product Q&P steel plate and a preparation method thereof, and belongs to the technical field of cold-rolled automobile steel production. The steel plate comprises the following chemical components of, in percentage by weight, 0.38%-0.42% of C, 0.10%-0.30% of Si, 0.80%-1.20% of Mn, 2.80%-3.20% of Al, less than or equal to 0.020% of P, less than or equal to 0.0030% of S, less than or equal to 0.0060% of N, the balance Fe and inevitable impurity elements. The preparation method comprises the following steps of smelting; continuous casting; hot rolling; acid pickling; cold rolling; and continuous annealing, specifically, heating a cold-rolled plate to 830-860 DEG C during continuous annealing, then slowly cooling to 700-730 DEG C, finally, rapid cooling cold-rolled plate to 350-400 DEG C at 40-60 DEG C per second cooling rate to carry out overaging distribution treatment. The Q&P steel plate has advantages that the mechanical property is excellent, the yield strength is larger than or equal to 480 MPa, the tensile strength is larger than or equal to 800 MPa, the elongation percentage is greater than or equal to 25%, the n isgreater than or equal to 0.20, the yield ratio is less than or equal to 0.75, and the cold forming property is good. The Q&P steel plate and the preparation method have low requirements on process equipment, and are suitable for production of an existing continuous annealing production line.

Description

[0001] Technical field: [0002] The invention belongs to the technical field of cold-rolled automobile steel production, and in particular relates to a high-strength plasticity cold-rolled Q&P steel plate with a tensile strength of 800 MPa and a preparation method thereof. [0003] Background technique: [0004] In recent years, with the rapid development of my country's automobile industry and the increasingly acute energy and environmental issues, in order to improve automobile fuel economy and reduce CO 2 To deal with global climate change, my country's "Passenger Car Fuel Consumption Limits" stipulates that by 2020, the average fuel consumption of passenger cars produced in my country should be reduced to 5 liters per 100 kilometers. The increasingly stringent emission standards put forward higher requirements for automobile manufacturers, and also provide development opportunities for the lightweight of automobile materials. For every 100 kg weight loss of the car, the f...

AI Technical Summary

Problems solved by technology

At present, the widespread application of Q&P steel mainly encounters two bottlenecks: (1) In the production process of traditional Q&P steel, in order to obtain better comprehensive performance, it is often necessary to quench at a lower temperature, and then rapidly heat up to a higher temperature. Alloying elements are distributed at the specified partition temperature, and the difference between the quenching temperature and the partition temperature is often about 100°C. Since the traditional continuous annealing production line has no rapid induction heating function in the aging section, it is difficult to promote the use of this process in the existing continuous annealing production line.

(2) At present, for cold forming, the stamping equipment and dies in the automotive industry generally have a bearing capacity of 600-800MPa, and it is difficult for existing stamping equipment to meet the force requirements for higher-level steel types

Among them, the content of Si and Mn is relatively high, and it is easy to produce external oxidation in the production of traditional continuous annealing production line, resulting in yellowing of the surface color

Chinese patent CN105018843A discloses Q&P steel compounded with vanadium and titanium and its manufacturing method. Its strength reaches 1350-1450 MPa. It is difficult to cold form due to its high strength and can only be used for simple parts production.

Chinese patent CN108660369A discloses a quenched and partitioned cold-rolled steel plate with a tensile strength greater than 1180MPa and its production method, Chinese patent CN103555902A discloses a heat treatment process for 980MPa-level high-strength plastic product automotive steel, and Chinese patent CN103555894A discloses a heat treatment process for Q&P980 steel In the process of annealing, the temperature difference between quenching and partitioning is very different, which makes it difficult to mass-produce the traditional continuous annealing production line

Chinese patent CN104988391A discloses a 1200MPa grade cold-rolled Q&P steel and its manufacturing method. In the annealing process, the temperature difference between quenching and partitioning is very different. At the same time, the rapid cooling process requires roll cooling and water cooling, which cannot be realized in the current traditional continuous annealing production line.

Chinese patent CN101487096A discloses a low-alloy high-strength C-Mn-Al-based Q&P steel and its manufacturing method. It adopts a low-Si plus Al composition system, wherein the Al content is 1.0-1.5%. During the heat treatment, the quenching temperature and The distribution temperature is also high, and it is difficult to implement in the traditional continuous annealing production line

Chinese patent CN103215491A discloses a method for preparing carbon-silicon-manganese-based Q&P steel by partitioning alloy elements. The annealing temperature of this invention is as high as 900-950°C. Before annealing, it needs to be pre-allocated at 720-800°C for 250-600s. At the same time, the quenching temperature is the same as the final The distribution temperature difference is more than 100°C, which cannot be realized in the existing continuous annealing production line

However, for 800MPa grade Q&P steel, its production is difficult, and it cannot be realized by using the conventional CSiMn composition system, and the addition of alloy elements is small, which cannot meet its hardenability requirements; the addition of alloy elements is slightly higher, and its strength can reach 1000MPa and above. , so it is necessary to adopt a new composition system and design concept to achieve

In addition, in the above-mentioned technology, the requirement of soaking temperature is too high, the cooling rate is too fast, and the temperature difference between quenching and partitioning is very different, which is difficult to realize in the existing continuous annealing production line.

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