Controlled rolling, controlled cooling and cold bending comprehensive forming method for variable-section U-shaped steel

Abstract

The invention discloses a controlled rolling, controlled cooling and cold bending comprehensive forming method for variable-section U-shaped steel. The controlled rolling, controlled cooling and cold bending comprehensive forming method mainly comprises the following steps: (1) conveying a longitudinal shearing steel band into a forming rack through a clamping and conveying device to realize cold bending initial deformation of a U-shaped steel piece; (2) conveying the steel piece into a heating region to realize controlled heating; (3) conveying the steel piece into a controlled rolling deformation region to synchronously realize variable section controlled rolling and cold bending finishing forming; (4) conveying the steel piece into a controlled cooling region to realize the material organization performance; and (5) conveying the steel piece into a finishing sizing region to guarantee an accurate form and location tolerance, cleaning the steel piece with derusting cleaning fluid, then storing the steel piece, and quickly removing rusts from the surface of the steel without damaging the surface of a metal structure. According to the controlled rolling, controlled cooling and cold bending comprehensive forming method for the variable-section U-shaped steel, local section deformation and cold bending forming for a set position are simultaneously completed; different materials are subjected to differential treatment; a heating procedure, a rolling procedure and a cooling procedure are designed according to the textures and the organization properties of the materials. The materials mainly comprise low-alloy high-strength steel subjected to controlled rolling and controlled cooling, such as bridge structural steel and building structural steel, and steel organizations such as ferrite-pearlite steel and dual-phase steel.

Description

technical field [0001] The invention relates to the technical field of steel structure forming, in particular to a comprehensive forming method of controlled rolling, controlled cooling and cold bending of variable-section U-shaped steel. Background technique [0002] In steel structure construction, for example, the orthotropic bridge deck of a bridge is mainly composed of bridge decks, beams and U-shaped steel; for example, the main frame structure of a building is composed of steel plates, square, U-shaped and H-shaped steels; for example, cold-formed U-shaped steel sheet piles are During the bending process, it is partially hot-rolled into the shape of a hook, which changes the shape of the traditional cold-formed hook, meets the water-avoiding requirements of engineering construction, and replaces the hot-rolled steel sheet pile. [0003] At present, the U-shaped steel used in bridges is mainly divided into constant-section U-shaped steel and variable-section U-shaped s...

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Problems solved by technology

[0003] At present, the U-shaped steel used in bridges is mainly divided into constant-section U-shaped steel and variable-section U-shaped steel. In recent years, there have been many reports on fatigue damage of constant-section U-shaped steel at home and abroad, resulting in the fatigue life of the steel bridge deck being much shorter than that required by the main body of the bridge. Design life

Experience has shown that in the above-mentioned equal-section U-shaped steel, the number of cracks at the weld between the steel box girder roof and the U-shaped steel is large, the damage is great, and the repair is difficult. The reasons for such fatigue cracks are: first, because the U-shaped steel is a closed structure. Section steel can only be welded from one side from the outside, and 75-85% of partial penetration welding is generally used, leaving 15-25% of the unfused part, about 1-2mm, and the 1-2mm unfused part itself forms a natural The initial cracks of the U-shaped steel become the source of fatigue cracks. Under the repeated action of the wheel load, the weld between the roof and the U-shaped steel is prone to fatigue cracking; the second is that the thickness of the welded part of the top plate of the U-shaped steel is reduced by 1 ~2mm, the cross-sectional area is reduced, resulting in a certain eccentricity at the connection, which will lead to additional bending to form stress concentration, thereby inducing cracks

Fatigue cracks will reduce the stiffness of the bridge deck and directly cause damage to the bridge deck pavement. In turn, the pavement damage will also aggravate the development of cracks in the bridge deck and reduce the fatigue life. Many steel box girder deck pavements in China are often repaired. this problem

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