What are the requirements and performance indicators for steel structure materials?
Steel structure in the process of use will be subjected to various forms of action (load, foundation uneven settlement, temperature, etc.), so it is required that the steel should have good mechanical properties (strength, plasticity, toughness) and processing properties (cold and hot processing and welding properties), to ensure the safety and reliability of the structure.There are many kinds of steel, only a few meet the requirements of steel structure, such as Q235 in carbon steel, l6Mn in low alloy steel, 20 manganese vanadium steel (20MnV) used for high-strength bolts, etc..
1, the intensity
The steel strength indicators are elastic limit E, yield limit y, and tensile limit U. The design is based on the steel yield strength. High yield strength can reduce the weight of the structure, save steel, and reduce the cost.Tensile strength U is the maximum stress that the steel can withstand before failure. At this point, the structure loses its performance due to large plastic deformation, but the structure does not collapse due to large deformation, thus meeting the requirements of resistance to rare earthquakes.The size of the U/y value can be considered as a parameter of steel strength reserve.
2, the plastic
The plasticity of steel generally refers to the property that after the stress exceeds the yield point, there will be significant plastic deformation without fracture.The main indicators of steel plastic deformation ability is elongation delta and reduction of area bits.
3. Cold bending performance
The cold bending performance of steel is a measure of the resistance of steel to crack when plastic deformation occurs in the bending process at room temperature.The cold – bending performance of steel is tested by cold – bending experiment.
4. Impact toughness
The impact toughness of steel refers to the ability of steel to absorb mechanical kinetic energy during fracture under impact load. It is a mechanical property to measure the steel’s resistance to impact load, which may lead to brittle fracture due to low temperature and concentrated stress.Generally, the impact toughness of steel is obtained by impact test of standard specimen.
5. Welding performance
The welding performance of steel refers to the welding joint with good performance obtained under certain welding process conditions.The welding performance can be divided into two kinds: welding performance in the welding process and welding performance in use.The welding performance in the welding process refers to the sensitivity of the weld and the metal near the weld without heat crack or cooling shrinkage crack.Good welding performance means that under certain welding conditions, the weld metal and the nearby base metal do not crack.In terms of service performance, the welding performance refers to the impact toughness and ductility performance in the heat-affected zone of the weld, and the mechanical performance of the steel in the weld and heat-affected zone shall not be lower than that of the base metal.In China, the welding performance test method in the welding process is adopted, and the welding performance test method in the usability is also adopted.
There are many factors affecting the durability of steel.First is the poor corrosion resistance of steel, must take protective measures to prevent corrosion of steel rust.Protective measures are: the regular maintenance of steel paint, are made of galvanized steel, with acid, alkali, salt and so on under the condition of strong corrosive medium, the use of special protective measures, such as offshore platform structure using anodic protection measures to prevent the corrosion of jacket, catheter frame fixed on zinc ingot, water electrolyte will automatically first corrosion of zinc ingot, so as to protect the function of steel jacket.Secondly, because the steel under high temperature and long-term load, its failure strength is reduced more than the short-term strength, so for the steel under long-term high temperature action, to determine the lasting strength.Steel over time will automatically become hard, brittle, that is, “aging” phenomenon.The impact toughness of steel under low temperature load should be tested.
The above is the introduction of the characteristics of steel structure;We are a steel structure manufacturer, the products are:steel column,steel frame,steel bridge;Welcome to consult ~
Post time: Oct-09-2020