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Intention of post-weld heat treatment of steel structure ins
     China Steel Network News: "Details determine success or failure", there are many details in the installation process of steel structure engineering need to pay attention to, today we are introducing the steel structure installation process, after welding, why do you want to do after welding Heat treatment, and how to do it.
     The post-weld dehydrogenation treatment refers to a low-temperature heat treatment performed after the weld is completed and the weld is not cooled to 100 ° C or lower. The general specification is to heat to 200~350 °C and keep warm for 2-6 hours. The main function of post-weld dehydrogenation treatment is to accelerate the escape of hydrogen in the weld and heat affected zone, and the effect of preventing weld cracking during welding of low alloy steel is extremely significant.
       During the welding process, due to the unevenness of heating and cooling, and the constraining or external restraint of the component itself, welding stress is always generated in the component after the welding work is completed. The presence of welding stress in the component will reduce the actual bearing capacity of the welded joint zone, resulting in plastic deformation, and in severe cases, damage to the component.
       The stress relieving heat treatment is to reduce the yield strength of the welded workpiece at a high temperature to achieve the purpose of relaxing the welding stress. There are two commonly used methods: one is the overall high temperature tempering, that is, the whole weldment is placed in the heating furnace, slowly heated to a certain temperature, then kept for a period of time, and finally cooled in the air or in the furnace. In this way, 80%-90% of the welding stress can be eliminated. Another method is local high temperature tempering, that is, heating only the weld and its vicinity, and then slowly cooling, reducing the peak of the welding stress, making the stress distribution relatively flat, and partially eliminating the welding stress.
       Some alloy steel materials have hardened structures on the welded joints after welding, which deteriorates the mechanical properties of the materials. In addition, this hardened structure may cause joint damage under the action of welding stress and hydrogen. If the metallurgical structure of the joint is improved after heat treatment, the plasticity and toughness of the welded joint are improved, thereby improving the overall mechanical properties of the welded joint.
       Steel welding points
       A. Introduction to steel welded mesh: Steel welded mesh (also known as steel mesh) is a mesh in which longitudinal steel bars and transverse steel bars are arranged at a certain interval and are at right angles to each other, and all intersections are welded together.
       B. Classification of steel welded mesh: The steel mesh can be divided into: cold-rolled ribbed steel mesh, cold-drawn round steel mesh, and hot-rolled ribbed steel mesh. Among them, cold-rolled ribbed steel mesh is the most widely used. The steel mesh is divided into two types: fixed steel mesh and custom steel mesh according to the grade, diameter, length and spacing of the steel bar.
       C, steel welded mesh features:
       1. Significantly improve the quality of steel works
       2, significantly improve the construction speed
       3. Reinforce concrete crack resistance
       4. Have better comprehensive economic benefits
       D, steel mesh specifications:
       1. Rebar mesh diameter: R4, R4.5, R5, R6, R7, R8, R9, R10, R11, R12
       2. The surface of the steel mesh is smooth or ribbed.
       3, the mesh spacing of the steel mesh: longitudinal 100, 150, 200, 300, 400mm; horizontal 100-400mm
       4, the width and length of the steel mesh can be customized.
       The welding procedure of the welded steel mesh is controlled by computer to ensure the stability of the welding quality and the spacing of the steel mesh without losing the strength and cross-sectional area of ​​the original steel. The use of steel welded mesh saves 30%~40% of steel, shortens the construction period by 80%, saves 60% of labor, and greatly reduces the cost, thus bringing huge economic and social benefits.

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