RU2356659C1 - Manufacturing method of lamellar cold-rolled steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes rolling of flat work of defined thickness with following annealing of coiled steel and its temper rolling. Increasing of ability to deep punching and increasing of other consumer properties of steel it is provided ensured by at manufacturing of low-carbon steel of vanadium-bearing steel of thickness h=0.7…3.0 mm and width 1.0…1.5 m semi-finished rolled products thickness is accepted equal, H=1.39h+0.96 mm, annealing of cold-rolled reels is implemented in bell-type furnace with hydrogenous protection atmosphere and with isolation during the heating process from 250°C up to 350°C during six hours, and temper rolling is implemented with clamping 1.0+0.1%.

EFFECT: improvement of consumer properties of cold-rolled iron steel.

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Description

The invention relates to rolling production and can be used in the manufacture of cold rolled sheet steel.

Mandatory operations in the production of such steel (usually coiled) are the cold rolling of hot-rolled strip billets in a continuous mill, annealing of coils in bell-type furnaces with a protective atmosphere, and the training of strips in a special mill. The manufacturing technology of cold-rolled sheet steel is described in sufficient detail, for example, in the book of P.I. Polukhin et al. “Rolling production”, M., “Metallurgy”, 1982, p.511-535.

A known method of manufacturing a sheet for particularly complex drawing from ageless boiling steel, for example 08Fkp, including hot rolling, etching, cold rolling and recrystallization annealing, in which the annealing of the tackle is carried out at 720 ... 740 ° C for 15 ... 20 hours (see a. S. USSR No. 456007, class C21D 1/26, publ. 05.03.75). However, this method is unsuitable for the production of vanadium-containing sheet steel with a thickness of 0.7 ... 3.0 mm grade 08GSUF with enhanced consumer properties.

The closest analogue to the claimed object is the technology for the production of cold rolled steel, described in the book by S. P. Efimenko and V. P. Slednev “Roller of sheet rolling mills”, M., “Metallurgy”, 1980, S.223 ... 225.

This production method involves rolling a strip billet of a given thickness, annealing and training strips, and is characterized in that the annealing is carried out in rolls, and after training, the rolled steel is cut into sheets with simultaneous dressing and oiling of the metal. The known method is also unsuitable for the production of vanadium-containing sheet steel due to the uncertainty of the main parameters of the process, which makes it impossible to obtain rolled products with enhanced consumer properties.

The main task solved by the present invention is to improve the consumer properties of low-carbon vanadium-containing thin steel.

To solve this problem, in a method involving rolling a strip billet of a given thickness with subsequent annealing of rolled steel and its training, in the production of low-carbon vanadium-containing steel with a thickness h = 0.7 ... 3.0 mm and a width of 1.0 ... 1.5 m, the rolled thickness assumed equal to H = 1.39h + 0.96 mm, annealing of cold rolled coils is carried out in bell furnaces with a hydrogen protective atmosphere and with holding in the process of heating from 250 to 350 ° C for six hours, and training is carried out with compression 1.0 ± 0.1%

The given process parameters are obtained empirically and are empirical.

The essence of the proposed technical solution is to optimize the values of the total relative compressions (εΣ = 1-h / H) during cold rolling, as well as the modes of recrystallization annealing and the relative compression during training after annealing. As a result of this, the best consumer properties are achieved (the main of which is the ability for deep stamping) of low-carbon vanadium-containing sheet steel with a cross section of 0.7 ... 3.0 × 1000 ... 1500 mm ² .

An experimental verification of the proposed technology was carried out at OJSC Magnitogorsk Iron and Steel Works.

To this end, in the manufacture of sheet steel of the specified assortment, εΣ was varied during cold rolling on a continuous broadband mill, the annealing modes of coils in bell furnaces, and the compression ratio during training. The results of the experiments were evaluated by the yield of high-quality sheets suitable for deep stamping.

The best results (yield of the required quality within 98.8 ... 99.6%) were obtained when implementing the proposed method. Deviations from its recommended parameters worsened the achieved indicators. So, with a decrease in εΣ (i.e., at H <1.39h + 0.96), the required strength characteristics of the rolled products were not achieved, and with an increase in εΣ (i.e., at H> 1.39h + 0.96), cases were observed cracking during tests for the ability to deep stamping, probably due to insufficient ductility of the metal.

The properties of steel deteriorated both during annealing in a different (than hydrogen) protective atmosphere of bell-type furnaces, and also when the proposed recrystallization annealing regime was not observed. Training after annealing with a relative compression of less than 0.9% reduced the strength characteristics of rolled products, and compression of more than 1.1% impaired the formability of steel. It was also found that the inventive method is suitable only for sheet low-carbon vanadium-containing steel with a thickness of 0.7 ... 3.0 mm and a width of 1.0 ... 1.5 m

The production technology of cold-rolled sheet steel, chosen as the closest analogue (see above), was not tested in experiments due to its obviously unsuitability for the production of low-carbon vanadium-containing steel used in deep stamping. Thus, an experimental verification proved the acceptability of the technical solution found to achieve the goal and its advantage over a known object.

Feasibility studies have shown that the use of the present invention at OJSC MMK in the production of the above cold-rolled sheet steel will increase the yield of high-quality rolled products with improved consumer properties by at least 3 abs.% With a corresponding increase in profit from its sale.

Concrete example

Low-carbon vanadium-containing thin steel sheet 08GSUF with a thickness of h = 1.8 mm and a width of 1.25 m is rolled from a strip billet with a thickness of H = l, 39 × h + 0.96-1.39 × 1.8 + 0.96≅3, 5 mm.

Annealing of cold rolled coils is carried out in bell-type furnaces with a hydrogen protective atmosphere and with holding during heating from 250 to 350 ° C for six hours. Annealed roll strips are trained with a relative reduction of 1%.

Claims (1)

A method for the production of strips with a thickness h = 0.7 ... 3.0 mm and a width of 1.0 ... 1.5 m of sheet cold-rolled low-carbon vanadium-containing steel, including rolling a strip billet of a given thickness with subsequent annealing of the rolled steel and its training, while the thickness of the rolled is taken equal to: N = 1.39h + 0.96 mm, annealing of cold rolled coils is carried out in bell furnaces with a hydrogen protective atmosphere and with holding during heating from 250 to 350 ° C for six hours, and the training is carried out with compression (1.0 ± 0.1)%.