Structural characteristics and advantages of light steel villa
Structural Characteristics And Advantages Of Light Steel Villa
Duplex Stainless Steel
Duplex Stainless Steel

Abstract: steel is widely used and has a wide variety. According to different section shapes, it can be divided into four categories: profile, plate, pipe and metal products.

The selection of steel should not only ensure the safety and reliability of structures,no fake and inferior steel products, but also be economical and reasonable, which must be treated with caution.

The selection of steel shall be comprehensively considered according to the importance of the structure, load characteristics, connection method, working environment, stress history, steel thickness and other factors.

How to identify fake and inferior steel

  1.  Fake and inferior steel is easy to fold. Folding is a variety of broken lines formed on the steel surface, and this defect often runs through the longitudinal direction of the whole product. The reason for folding is that the fake and shoddy manufacturers pursue high efficiency, and the reduction is too large, resulting in ears. Folding will occur in the next rolling, and the folded products will crack after bending, resulting in a great decline in the strength of steel.
  2. The appearance of fake and inferior steel is often pitted. Pitted surface is a kind of irregular and uneven defect on the steel surface caused by serious wear of rolling groove. Due to the pursuit of profit by fake and shoddy steel manufacturers, the rolling groove often exceeds the standard.
  3. The surface of fake and inferior steel is easy to produce scabs. One is that the quality of fake and shoddy steel is uneven and there are many impurities. The other is that the guide equipment of fake and inferior steel manufacturers is simple and easy to stick to steel. These impurities are easy to scar after biting the roll.
  4.  The reason why the surface of fake and inferior steel materials is easy to crack is that its blank is adobe with many air holes. During the cooling process, the adobe will produce cracks due to the action of thermal stress, and there will be cracks after rolling.
  5. Fake and inferior steel is easy to scratch because the equipment of fake and inferior steel manufacturers is simple and easy to produce burrs and scratch the steel surface. Deep scratches reduce the strength of steel.
  6. Fake and inferior steel has no metallic luster and is light red or similar to pig iron for two reasons. Second, its blank is adobe.
  7.  The rolling temperature of fake and inferior steel is not standard. Their steel temperature is through visual inspection, so it is impossible to roll according to the specified austenite area, and the performance of steel naturally cannot meet the standard.
  8.  The transverse reinforcement of fake and inferior steel is thin and low, and there is often insufficient filling. The reason is that in order to achieve large negative tolerance, the reduction of the first few passes of the finished product is too large, the iron mold is too small, and the hole mold is not fully filled.

How to choose good steel

1. Importance of structure

According to the unified standard for reliability design of building structures (gb50068-2001), structures and components can be divided into important, general and secondary categories according to their use, location and severity of damage consequences, and the corresponding safety levels are level I, level II and level III.

Different types of structures or components shall be made of different steels. Heavy industrial building structures, long-span structures, high-rise or super high-rise civil building structures and heavy duty crane beams or structures are important primary structures, and high-quality steels shall be selected;

General industrial and civil building structures belong to secondary structures, and ordinary quality steel can be selected according to the nature of work.

The framework of temporary houses and the auxiliary components in general buildings, such as ladders and railings, belong to secondary three types of structures, and poor quality steel can be selected.

fake and inferior steel
2. Load case

The load can be divided into static load and dynamic load. High quality steel with good toughness and fatigue resistance, such as Q345 steel, shall be selected for structures directly bearing dynamic loads and structures in strong earthquake areas, and appropriate additional guarantee items shall be put forward.

Q235 steel with lower price can be selected for structural members generally bearing static load or indirect dynamic load at room temperature.

3. Connection method

There are two connection methods of steel structure: welding and non welding. During welding, welding deformation, welding stress and other welding defects (such as undercut, air hole, crack, slag inclusion, etc.) will occur, which may lead to cracks or brittle fracture of the structure. Therefore, the material requirements of welded structure should be strict.

For example, in terms of chemical composition, the limit content of carbon, sulfur and phosphorus must be strictly controlled for welded structures, and the carbon content of non welded structures can be reduced.

4. Temperature and environment of the structure

The environmental conditions of the structure, such as temperature change and corrosive medium, have a great impact on the mechanical properties of steel.

Structural members under low temperature conditions, especially welded structures and tensile members, are prone to low-temperature cold brittle fracture failure, so calm steel with good low-temperature brittle fracture resistance should be selected.

Steel structures in corrosive media, such as steel structure plants of chemical enterprises, shall adopt corrosion-resistant steel and strengthen the rust prevention treatment of exposed steel members.

In addition, the steel of open-air structure is prone to aging, and the steel under the action of harmful medium is prone to corrosion, fatigue and fracture. Different materials should also be selected differently.

5. Steel thickness

Thin steel has more rolling times and higher compression ratio;

The compression ratio of steel with large thickness is small. Therefore, the steel with large thickness not only has low strength, but also has poor plasticity, impact toughness and weldability. Therefore, the welding structure with large thickness shall be made of steel with good material.

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