SU1708452A1 - Strip hot rolling method - Google Patents

Abstract

The invention relates to rolling production and may be used in the hot rolling of carbon and low alloy steels on continuous broadband mills. The method includes compressing the slabs to the final thickness of the strips in the mill assortment at a rolling end temperature of 800-900 ° C, cooling the strips with laminar water jets with a regulated specific flow rate to a predetermined temperature. In order to obtain a given level of strength and stability of the strength properties on the slab of one heat, the coiling temperature is charged from the relationship Tem = -d- (AO + A2A1 + AZ F + A ^ Se - ob), where Tem is the coiling temperature, ;WITH; (TV - specified value of strength, kg / cm; H - final strip thickness, mm; Ce - carbon equivalent; F - specific coolant consumption, m '^ / m ^ h; AO, Ai, A2, AZ, A4 - coefficients whose values are in the range (39.2616- 44.9020),

Description

The invention relates to rolling production and can be used in the hot rolling of carbon and low alloy steels on continuous broadband mills.

The purpose of the invention is to obtain a predetermined level of strength and stability of the strength properties on the plates of one heat.

The strength of the hot rolled steel sheet and its stability depend mainly on its chemical composition, which can be estimated by carbon equivalent, coil temperature and cooling rate, which, in turn, is determined by the specific flow rate of cooling water and strip thickness. Thus, based on the chemical composition of the steel and the rolling parameters, it is possible to unambiguously determine the coiling temperature, which ensures a given level and stability of the strength properties at the same melting point.

The connection of the temperature of the coiling The, ° C with the ultimate strength of ob, kg / mm and the parameters of rolling: strip thickness H, mm; carbon equivalent of ce; specific consumption of water F, m / m-h is described by the equation

(AO + A2H + Az F + - TV), (1)

I see

Ai

The experimentally determined coefficients of equation (1) are equal for carbon steels AO 39.2616; Ai 0,0108; Aa-0.7730; AZ 0.0284; A4 37.9779; (2)

for low-alloy steels AO 44.9020; Ai 0.0264; A2 = 0.7259; AZ 0.0425; A4 137.2566. (3)

In tab. Figure 1 shows the coiling temperature values determined by equation (1) for stZ carbon steel and low alloyed 09G2S steel when each of the coefficients of AO - A4- is changed to 10%. The results obtained indicate a significant effect of each of the coefficients on the coiling temperature and tensile strength of sheet steel.

Example. If a single steel melting is loaded into a furnace and heated to 1250 ° C, the heated slab is pushed onto the furnace roller conveyor of a continuous 1700 wide-strip mill, compressed to an intermediate thickness of 40 mm in the roughing stand group and to a final thickness of 2-9 mm in the finishing group. - Using the interstand cooling of the strip and adjusting the rolling speed, the rolling end temperature is maintained at 900 ° C. The temperature range of 400-700 ° C winding of the strips into rolls is provided by cooling the strips with laminar jets of water with a regulated specific flow rate. The first mode (on the proposed method).

The strips with a thickness of 2-9 mm are rolled from stz steel slabs with carbon equivalent Ce 0.20-0.40 and from slabs 09G2S with carbon equivalent Ce 0.12-0.20. When the temperature of the end of the rolling Tcp of steel stz strip equal to 900 ° C, the specific water consumption F 75 h, the coiling temperature is determined from equation (1) for a given tensile strength of tS 43-47 kg / mm using coefficients (2). The temperature of the rolling end of the 09G2S steel strips is set equal to 900 ° C, the specific water consumption F is 75 hours, the coiling temperature is determined from equation (1) for the tensile strength Ov-50-52 kg / mm using coefficients

(3).

The second mode (by a known method).

For every second slab for the group of stZ and 09G2S steels with the same carbon equivalents of Сe and technological rolling modes (Н, Ф, Ткп) temperature

The winding is constant and equal to 600 ° C. After cooling of the strips, samples are cut from them for sample preparation and tensile testing. The results of the tests (table. 2) show that when

hot rolling in the second mode, the variation in tensile strength from a given level for steel stZ can reach 3 kg / mm, and for steel 09G2S - 3.5 kg / mm. Deviation of strength values from the specified

the level during hot rolling in the first mode does not exceed 0.5 kg / mm.

The technical and economic advantages of the proposed method consist in the fact that the adjustment of the coiling temperature depending on the chemical composition of the steel and the technological modes of hot rolling ensures a given level of strength and stability of the strength properties at the slab of one heat.

Claims (1)

Invention Formula The method of hot rolling of strips, predominantly of carbon and low alloyed steels, including rolling the slabs to the final thickness of the strips in the mill assortment at a rolling end temperature of 800-900 ° C, cooling the strips with laminar water jets with a regulated Specific flow rate to a predetermined temperature of coiling, characterized in that, in order to obtain a predetermined level of strength and stability of the strength properties on the slabs of one heat, the coiling temperature is established from Tem - (AO + AaN + AZ F + AdS - STv), one where Tem is the coiling temperature, ° С; 45STv - the specified value of the tensile strength, kg / mm; H is the final strip thickness, mm; Ce is the carbon equivalent; F - specific coolant consumption, 50 h; AO, AI, Aa, AZ, A / 1 - coefficients whose values are in the range (39.2616-44.9020), (0.0108-0.02.02), - (0.77300, 7259), (0, 0284-0.0425), (37.9779-137,2566) 55, respectively, in each of which the first value refers to carbonaceous and the second to low-alloyed steel m.