SU1834723A3 - Method of producing cold-roller strips - Google Patents

Description

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

The purpose of the invention is a simultaneous increase in the strength and formability of a cold-rolled steel sheet by controlling the processes of phase and texture formation.

This is achieved by the fact that in the method for the production of cold rolled strips from steel, containing, wt.%: C <0,09; Mn = 0.02-1.0;

SI <0.25: 0.02 <A1 <0.08; P = 0.04-

0.10; S <0.025; V = 0.005-0.05; Mo = 0.005 ~ 0.03; balance iron and unavoidable impurities, comprising a hot rolling, a forced cooling prior to coiling the strip into a coil, coiling into a roll with SCI = 500-600 ° ^C, cold rolling with a reduction of 60-80%, with a final recrystallization annealing by heating at 700-780 ° C and training, cooling of the strip after hot rolling is carried out with a gradient heat dissipation perpendicular to the plane of the strip on the discharge roller table due to the excess of no more than 1.5 times the intensity of scenting on the upper surface of the strip, compared to the lower surface, cold rolling of the strip is carried out on ragged work rolls with a roughness ratio of R _a '/ Ra ² = 3-5, and rolls with a higher roughness of the surface of the barrel are combined with the surface of the strip located during hot rolling from the bottom, while bell-shaped recrystallization annealing is carried out in three stages with different heating rates; up to 450 ° С with the speed Vi = 0.08-1.6 deg / min, in the intermediate temperature range 450 ~ 560 ° С - with the Velocity V2 = 0, 0δ0.08 deg / min in the temperature range 560 ° С - the final annealing temperature is 700 -780 ° C - at a speed of \ 7z = 0.35-0.8 deg / min.

The proposed method allows you to take into account the mechanisms of formation of the necessary structure and texture of steel with increased strength and excellent ability to deep drawing. Gradient heat removal of the strip after hot rolling and cold rolling in raznosher®® grooved rolls are used to create axial fields of internal stresses in the metal that stimulate the formation of phosphorus-containing segregations at special grain boundaries that effectively block numerous texture formation during recrystallization annealing of steel, inhibiting the development of cubic undesirable for stamping texture components and retaining in the steel sheet after annealing a high level favorable for deep drawing lining of an octahedral texture, Three-stage annealing with delayed heating in the temperature range 450–560 ° С is used to isolate metastable aluminum nitride, which causes the formation of a recrystallization texture with a high intensity of octahedral orientation. Molybdenum and vanadium additives are introduced into steel to bind carbon and nitrogen to carbonitrides and enhance the effect of phosphorus-containing segregations on the steel structure. Microalloying of steel and the specified set of technological methods at different stages of the production of sheet steel provides texture uniformity of steel with a very high proportion of octahedral grain orientation with increased strength and maximum normal plastic anisotropy coefficients.

The proposed method can be implemented as follows.

Example 1. Steel with a mass fraction of elements, wt.%: C 0.06; SI 0.07; MP 0.37; P 0.06; ΑΙ 0.05; V 0.02; Mo 0.01; S 0.013; N 0.007 was smelted in a 350-ton oxygen converter, cast on a continuous casting machine into 250 mm thick slabs, rolled into a hot mill with a temperature of the end of hot rolling Tkp = 830 ° C and a strip winding temperature Tms = 520 ° C. Before winding, the strips were cooled on the discharge roller table with water, while the intensity of the scenting of the upper surface of the strip was 2.3 times greater than the intensity of the scuffing was established by the water flow rate by turning off part of the lower sections of the scenting unit.

Asymmetrically cooled strip was rolled on a 4-stand cold rolling mill with a total compression of 70% to a thickness of 0.7-0.9 mm, while the upper work roll with a roughness of R _a ¹ = 2-5 μm, the lower working one was installed in the last stand a roll with a surface roughness of Ra ² = 0.2 μm. When the strip was rewound into a roll during cold rolling, the upper side of the strip on hot rolling became the lower side on cold rolling. Rolls of cold-rolled steel weighing 20 tons and a width of 1250 mm were annealed in a single-foot cap furnace. The following conditions were provided during the heating process: to a temperature of 450 ° C, the coils were heated with a maximum average speed Vi = 1.1 deg / min, in the temperature range 450560 ° C, the average metal heating rate was 0.06 deg / min, and the average heating rate in the range 560 740 ° C was 0.50 deg / m. Exposure at the final annealing temperature of 740 ° C is 15 hours. Next, the coils were cooled in accordance with the current annealing instructions and processed on a temper mill with a compression ratio of 1%.

The cold-rolled sheet steel of the OSV drawing category, obtained by new technology, had the following mechanical properties σ _Γ = 260 MPa. σ _Β = 390 MPa,

04 = 34%, du = 40% hardening coefficient = 0.211, Eriksen hole depth 1112 mm, normal plastic anisotropy coefficient R = 1.81.

Example 2. Steel of chemical composition, wt.%: C 0.05; Si 0.02; MP 0.20; P 0.052; AI 0.04; V 0.01; Mo 0.03: S 0.013; No. 0,008; Cr 0.03; Cu = 0.07; Ni 0.05 was smelted in an oxygen converter, cast on a continuous casting machine into 250 mm thick slabs, rolled into hot mill with Ткп = 850 ° С and Тcm = 520 ° С. After hot rolling, it was cooled with a gradient heat dissipation: the intensity of cooling by showering of the upper surface of the rolled product exceeded that of the lower surface by 2.7 times. Cold rolling was carried out with a total degree of compression of 67% to a thickness of 0.9 mm, the roughness of the upper work roll R _a ¹ = 3.1 μm, the roughness of the lower work roll in the last pass was R _a ² = 0.8 μm. Cold rolled coils were annealed in a single-foot bell furnace. The heating rate to 450 ° C is 1.2 deg / min, the heating rate in the temperature range 450 ~ 560 ° C is 0.05 deg / min, the heating rate is from 560 ° C to the final annealing temperature of 760 ° C - 0.47 deg / min.

Exposure at an annealing temperature of 760 ° C for -17 h. Cold rolled steel strips were trained with a compression ratio of 0.9%.

The cold-rolled sheet steel of the OSV extract category obtained by the new technology had the following mechanical properties: σ _Γ = 240 MPa. σ _Β = 350 MPa, 04 = 38%, 0yu = 43%, Eriksen hole depth 11-12 mm, hardening coefficient 0.207, normal anisotropy coefficient R = 2.1.

Phase and texturization control makes it possible to achieve high levels of strength and plastic properties in low-carbon microalloyed steels, the highest among the well-known steel grades, the coefficient of normal plastic anisotropy R and excellent ability to deep drawing.

The results of comparative tests are shown in the table.

Rolled steel obtained using advanced technology was tested by consumers for stamping front and power parts of complex shapes of cars and trucks. The yield was 99.8-100%.

The introduction of a new technology using a set of agreed technological methods at the stages of hot 10 rolling, cold rolling, and recrystallization annealing made it possible to obtain cold rolled steel with an especially high formability and high strength that fully meets the requirements of consumers.

Claims (2)

Claim 1. Method for the production of cold rolled strips from steel containing. wt.%: C <0.09; Mn = 0.02-1.0; SI <0.25; 20 0.02 <A1 <0.08; P = 0.04-0.10; S <0.025; V = 0.005-0.05; Mo = 0.005-0.03; the rest is iron and unavoidable impurities, including hot rolling, forced cooling before winding the strip into a roll at the 25 discharge roller table, winding into a roll at 500-600 ° C, cold rolling with 60-80% compression, recrystallization annealing with final exposure at 700-780 ° C and training, characterized in that 30 cooling of the strip after hot rolling is performed with a gradient of heat removal perpendicular to the plane of the strip on the discharge roller due to not exceeding; less than 1.5 times the intensity of cooling35 of the upper surface of the strip compared to. with the bottom. surface, cold rolling of the strip is carried out in ragged work rolls with a roughness ratio of R _a ^ / R _a ² = 3-5, the rolls with 40 greater surface roughness are combined with the surface of the strip located during hot rolling from the bottom. 2. The method according to claim 1, characterized 45 by the fact that they produce bell-type recrystallization. annealing in the three stages with different heating rates up to 450 ° С with the speed Vi = 0.8-1.6 deg / min, in the intermediate temperature range 450-560 ° С - with the speed V2 = 0.05-0.08 deg / min, in the temperature range 560-700-700 ° С - with a speed of Х / з = 0.35-0.8 deg / min. Mechanical properties and stampable ™ indicators of low-carbon steels made according to the known and proposed methods (according to the results of mechanical tests of 10 heats)