阅读说明：本技术 一种超宽if钢防冷瓢曲应用方法 (Application method for preventing ultra-wide IF steel from being buckled by cold ) 是由 曾磊文 贾冬梅 李翔 曾松盛 于 2020-06-15 设计创作，主要内容包括：本发明提供一种超宽IF钢防冷瓢曲应用方法,通过控制超宽IF钢的加热温度为805±5℃、生产速度不低于140mpm、H<Sub>2</Sub>含量75%的高氢冷却方式,控制时效1段温度为240±20℃,时效2段为200±℃,实现超宽IF钢的冷瓢曲应对技术。(The invention provides a cold buckling prevention application method of ultra-wide IF steel, which is characterized in that the heating temperature of the ultra-wide IF steel is controlled to be 805 +/-5 ℃, the production speed is not lower than 140mpm, and H is controlled 2 The high-hydrogen cooling mode with the content of 75 percent controls the temperature of the aging 1 section to be 240 +/-20 ℃ and the temperature of the aging 2 section to be 200 +/-so as to realize the cold buckling coping technology of the ultra-wide IF steel.)

1. An application method of ultra-wide IF steel cold buckling prevention is characterized in that: controlling the heating temperature of the ultra-wide IF steel to be 805 +/-5 ℃, and the production speed to be not lower than 140mpm and H ₂The high-hydrogen cooling mode with the content of 75 percent controls the temperature of the aging 1 section to be 240 +/-20 ℃ and the temperature of the aging 2 section to be 200 +/-20 ℃, thereby realizing the cold buckling coping technology of the ultra-wide IF steel.

2. The ultra-wide IF steel cold buckling prevention application method as claimed in claim 1, wherein: the temperature difference between the strip steel and the furnace roller of the final cooling section is reduced by controlling the temperature difference of the strip steel at the inlet and the outlet of the final cooling section to 60 ℃, so that the thermal stress of the strip steel is reduced, and the cold buckling risk is reduced.

3. The ultra-wide IF steel cold buckling prevention application method as claimed in claim 1, wherein: by reducing the tension (1-4-7 KN of aging, 2-4-7 KN of aging and 6-9 KN of final cooling) of the strip steel in the cold zone in the furnace, the static stress borne by the strip steel and the friction stress of the strip steel transversely unfolded are reduced, the cold buckling risk of the strip steel is reduced, the strip steel is ensured to have no abnormity in shape change, and the strip breakage is prevented.

Technical Field

The cold buckling prevention coping technology for the ultra-wide IF steel is a process scheme for normal operation of a specific ultra-wide IF steel band in the annealing process, and is mainly applied to the field of material processing.

Background

For ultra-wide IF steel (the width is more than or equal to 1700mm, the thickness is less than or equal to 1.1 mm) in the continuous annealing production process, because the time-effect temperature is 400 ℃ (figure 2, an annealing curve chart), at the temperature, the strip steel is very easy to generate cold buckling, particularly the strip steel with the width exceeding 1800mm and the thickness less than 1mm is extremely sensitive to the tension in the furnace and the temperature in the furnace. The strip steel has buckling critical tensile stress in the furnace, which is mainly related to the performance of the strip steel and the structure and arrangement of furnace rollers, and the formula is as follows:

in the formula: t is _crCritical tension at which buckling occurs: a K-factor; r-guide roll radius; h is the thickness of the plate;

a-the length of the strip steel between the two rolls; sigma-a material yield strength; b-board width; -angle of taper of the roller;

e-modulus of elasticity of the material; mu-coefficient of friction between the strip steel and the guide roll; c-straight section length of roller.

The strip steel has an actual stress in the furnace, which is mainly related to the stress generated by the strip steel attaching to the conical surface, the transverse compressive stress caused by the friction counter force of the furnace roller in the transverse flattening process of the strip steel and the thermal stress in the width direction of the strip steel caused by the temperature difference between the strip steel and the furnace roller, and the following formula is as follows:

in the formula sigma₁Stress generated by the conical surface of the furnace roller corresponding to the strip steel

σ₂Transverse compressive stress caused by frictional reaction with furnace rollers during transverse flattening of strip steel

σ₃Thermal stress in the width direction of the strip caused by the temperature difference between the strip and the furnace rollers

Wherein sigma₁And σ₂Mainly related to the tension of the strip steel in the furnace, the smaller the tension is, the two stresses can be relatively reduced, and the buckling risk can be reduced.

And σ₃For thermal stress, the corresponding equation: σ = β Δ Ε Δ t/1.05

Sigma-thermal stress (Mpa)

Beta-coefficient of linear expansion (1/. degree.C.)

Δ t-temperature difference (. degree. C.)

E-object elastic modulus (Mpa)

For ultra-wide IF steel, when the average temperature of the strip steel is 400 ℃, cold buckling is easily generated, and the main reason is that in the cooling process, the surface of the strip steel is cooled unevenly, the transverse temperature difference is large, and therefore, large thermal stress is easily generated to cause buckling.

Disclosure of Invention

The invention aims to provide an application method for preventing cold buckling of ultra-wide IF steel, which has specific requirements on running speed, tension in a furnace, width transition and temperature control and realizes normal production of the ultra-wide IF steel.

In order to achieve the purpose, the technical scheme provided by the invention is as follows: the application method controls the heating temperature, the heating speed, the heat preservation time, the cooling mode and the cooling speed of the ultra-wide IF steel, and realizes the cold buckling coping technology of the ultra-wide IF steel by reasonably planning and scheduling strip steel in a protective atmosphere, preheating a furnace roller in a cold area, adjusting the power of a cooling fan and adjusting the tension of the strip steel.

By controlling the transverse temperature difference of the surface of the strip steel, the thermal convexity of the strip steel is reduced, the thermal stress of the strip steel is reduced, and the cold buckling risk is reduced.

The tension of the strip steel in a cold area in the furnace is reduced, so that the static stress borne by the strip steel and the friction stress transversely unfolded by the strip steel are reduced, the risk of buckling of the strip steel due to cold is reduced, the strip steel is ensured to have no abnormal shape change, and the strip breakage is prevented.

The scheme can reduce the thermal stress of the strip steel, reduce the risk of cold buckling, ensure that the strip steel plate shape has no abnormal change, prevent the strip breakage and ensure the stable operation of production.

Drawings

FIG. 1 is a schematic view of an annealing furnace of the present invention.

FIG. 2 is a table 1 diagram of the present invention.

FIG. 3 is a table 2 diagram of the present invention.

Detailed Description

The invention will be further described with reference to the accompanying drawings, in which preferred embodiments of the invention are: an IF steel strip with a specification of 1741mm by 0.605mm, which is highly susceptible to buckling, is taken as an example. Through research on the generation mechanism of the IF steel buckling, the influence of factors on the IF steel buckling is researched, and the most appropriate ultra-wide IF steel cold buckling responding technical scheme is researched and made in combination with the situation of field actual production. An annealing furnace as shown in figure 1 was used:

by using 75% of high H2 (H2 has the advantages of light weight and large heat transfer coefficient), and by using H2 as a cooling medium, the cooling efficiency can be better achieved, the vibration of the strip steel can be reduced, the scratch defect of the strip steel can be reduced, and the tension of the strip steel does not need to be increased), the strip steel is rapidly cooled from 650 ℃ to 280 +/-20 ℃ by using the cooling medium, the outlet temperature of the aging section 2 is 200 +/-20 ℃, and the temperature of the final cooling section is controlled to be about 140 +/-DEG C. While the temperature of the aging stage 2 before improvement is 400 ℃, and the temperature of the final cooling stage is 150 ℃. The difference in temperature of 2 sections of ageing and final cooling sections is reduced to 60 ℃ by 250 ℃, very big reduction 2 sections of ageing and final cooling section difference in temperature, further reduce the difference in temperature between belted steel and the stove roller, according to thermal stress formula sigma = beta can Δ t/1.05, thermal stress reduces to the 1/4 of original thermal stress, the very big reduction of buckling risk, the effectual production of preventing the cold buckling of belted steel, see from the actual conditions, production limit specification product, cold buckling obtains controlling basically.

The width of the furnace roller is changed to 1800mm by using a high-strength steel HSLA340 material, and the furnace roller in a cold area is preheated, so that the influence of the temperature difference of the furnace roller on the ultra-wide IF steel is prevented, and the buckling thermal stress is reduced.

And controlling the temperature difference delta t between the outlets of the fast cooling section and the aging section 2 to be within 80 ℃. Because the longitudinal area of the strip steel has temperature difference, the same temperature difference can exist in the transverse area, and the longitudinal temperature difference is also controlled to ensure that the thermal stress is controlled to be minimum in order to reduce the temperature difference in the transverse area.

Reducing the tension of the aging section and the final cooling section (see the attached figures 2 and 3).

The production line speed is not lower than 140mpm, the contact time of the strip steel and the furnace roller is reduced, and the influence of the furnace roller on the strip steel is reduced.

The thick and narrow materials are firmly prevented from being transited to the thin and wide materials, and the buckling caused by the large thermal stress generated by the large thermal convexity is prevented.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that the changes in the shape and principle of the present invention should be covered within the protection scope of the present invention.