1. Connection mode. In the production of steel structures in iron sheet workshop, high-strength steel should be studied to greatly improve its yield point strength; In addition, new types of steel such as H-section steel (also known as wide flange section steel), T-section steel and profiled steel plate should be rolled to meet the needs of long-span structures and super high-rise buildings. Welds, bolts or rivets are usually used to connect all parts of the steel structure. Because of its light weight and simple construction, Beijing factory leasing is widely used in large factories, venues, super high-rise buildings and other fields. Steel structure engineering is a structure composed of steel, which is one of the main types of building structures. The structure is mainly composed of beam steel, steel column, steel truss and other components. The rust removal and rust prevention processes such as silylation, pure manganese phosphating, water washing and drying, and galvanizing are adopted. Due to the inevitable welding stress, welding deformation and welding defects in the welding process. Therefore, steel with low carbon, sulfur and phosphorus content, good plasticity, toughness and weldability should be selected... For non welded structures, these requirements can be relaxed

2. Importance of structure. Important structures, such as heavy industrial building structures, long-span structures, high-rise or super high-rise building structures or other structures, shall be used in high-quality steel. For general industrial and civil structures, it is selected according to the general properties of steel.

3. Structure of working and living environment. The structure and environment, such as the continuous change of temperature and the main role of corrosion, have a great impact on the development of steel. Killed steel with good low-temperature brittle fracture resistance shall be selected for the structure working at low temperature, especially the welding technology structure. The minimum temperature that may be caused by structural analysis shall be higher than the cold brittle transition temperature of steel. When there are corrosive media around, corresponding management requirements shall be put forward for the corrosion resistance of steel.

4. Load characteristics. Q235C or Q345C and other structures under dynamic load shall be made of steel with good plasticity and impact toughness; For the structure under static load, the steel with ordinary quality can be selected, such as q235bf.

Steel thickness. The thickness of steel is not only low in strength and ductility, but also poor in impact toughness and weldability. The application of good steel quality has a large welding structure thickness.