What are the material requirements of steel structure?

intensity

The strength index of steel is composed of elastic limit, yield limit and tensile limit. The design of steel structure is based on the yield strength of steel. High yield strength can reduce the weight of the structure, save steel, reduce costs. Tensile strength is the maximum stress that steel can withstand before failure. At this time, the structure loses its performance due to large plastic deformation, but the structure deformation is large and does not collapse, which should be able to meet the requirements of the structure to resist rare earthquakes.

plasticity

The plasticity of steel generally means that after the stress exceeds the yield point, the plastic deformation is obvious and the fracture is not broken. The main index to measure the deformation ability of steel is elongation and section shrinkage.

Cold bending property

The cold bending property of steel is a measure of the resistance of steel to cracks when bending and deforming at normal temperature. The cold bending property of steel is tested by cold bending test.

Impact toughness

The impact toughness of steel refers to the ability to absorb mechanical kinetic energy during the fracture process under the impact load of steel, and is a measure of the mechanical properties of steel that may be brittle fracture due to low temperature and stress concentration. The impact toughness index of steel is generally obtained by impact test of standard specimens.

weldability

The weldability of steel refers to the welding joint with good performance obtained under certain welding process conditions. Welding performance can be divided into welding performance and service performance in the welding process. The weldability in the welding process refers to the sensitivity that the weld and the metal near the weld do not produce hot cracks during the welding process or cooling does not produce cooling shrinkage cracks. Good welding performance means that under certain welding process conditions, the weld metal and the nearby base metal do not crack. Weldability refers to the impact toughness of the weld and the extension properties of the heat-affected zone, requiring that the mechanical properties of the steel in the weld and heat-affected zone are not lower than the mechanical properties of the base material. Our country adopts welding performance test method and welding performance test method.

durability

There are many factors that affect the durability of steel. First of all, steel corrosion resistance is poor, protective measures must be taken to prevent steel corrosion and rust. Protective measures include: regular paint maintenance of steel, the use of galvanized steel, in acid, alkali, salt and other strong corrosive media conditions to take special protective measures. For example, the offshore platform structure uses anodic protection measures to prevent jacket corrosion, zinc ingots are fixed on the jacket, and seawater electrolytes will automatically corrode zinc ingots first, thus achieving the function of protecting steel jacket. Secondly, because the failure strength of steel under high temperature and long-term load is much lower than the short-term strength, the durability strength of steel under long-term high temperature should be measured. Steel will automatically harden and become brittle over time, that is, the phenomenon of timeliness. Steel under low temperature load should be checked for impact toughness.