100 ton Overhead Crane Steel for Steel Works

100 ton Overhead Crane Steel for Steel Works

After learning about bridge cranes, gantry cranes, jib cranes and other products, some friends must have doubts about the choice of steel. Is the production steel of the crane all uniform in specification? Is there any difference in steel selection in different working environments?

In fact, the selection of steel is based on the actual situation of steel production in my country, combined with the working characteristics of the crane structure, on the premise of ensuring the safety and reliability of the structure, fully considering the economy of materials and the characteristics of domestic steel, to determine the steel.

Specifically, the selection principles are as follows:

1. The importance of structure

According to the type of metal structure, generally light-duty truss structures mostly use steel rolled from carbon structural steel, and the minimum angle steel should not be less than 45m x 45m x 5m;

Low-alloy steel may be considered for heavy-duty truss structures. The plate girder structure is mostly made of rolled carbon structural steel. The thickness of the steel plate should not be less than 6mm. If there is a special anti-corrosion coating, it may not be less than 5mm.

For special-purpose crane structures, if the thickness has to be reduced due to weight restrictions and structural requirements, the welding process can also be considered to be no less than 4mm.

2. load characteristics

The load on the steel structure of hoisting machinery can be: static or dynamic, often acting, sometimes acting or occasionally occurring (such as earthquakes), often fully loaded or not often fully loaded, etc.

Appropriate steel materials should be selected according to the above-mentioned characteristics of the load, and the necessary quality assurance project requirements should be put forward. For structural members directly bearing dynamic loads, steel materials with better quality and toughness should be selected:

General-quality steel can be used for structural members subject to static or indirect dynamic loads.

For the structure bearing the dynamic load or the structure with a higher level of operation, the killed steel should be used, and the aluminum alloy should not be used.

3. connection method

Structural steel connections may be welded or non-welded (bolts or rivets).

For welded structures, uneven heating and cooling during welding often cause high welding residual stress in the components;

Welding structure and unavoidable welding defects often cause crack-like damage to the structure;

The overall continuity and rigidity of the welded structure make it easier for defects or cracks to penetrate each other;

In addition, excessive carbon and sulfur content will seriously affect the weldability of steel.

Therefore, the quality requirements of welded structural steel should be higher than that of non-welded structural steel in the same situation, the content of harmful elements such as carbon, sulfur, phosphorus should be lower, and the plasticity and toughness should be better.

For non-welded structures, the above requirements can be appropriately relaxed in comparison.

4. The working environment temperature of the structure

The plasticity and toughness of steel decrease with the decrease of temperature. At low temperature, especially in the brittle transition temperature zone, the toughness decreases sharply, and brittle fracture is prone to occur.

Therefore, for steel structures that often work or may work at relatively low negative temperatures, especially welded structures, steels with better chemical composition and mechanical properties and brittle transition temperatures that are lower than the working environment temperature of the structure should be selected.

5. Steel thickness

Due to the small compression ratio during rolling, the steel with large thickness has poor strength, impact toughness and welding performance, and is prone to produce residual stress.

Therefore, welded structures with large component thickness should use good quality steel.

6. Qualified guarantee of impact toughness at room temperature

For steels of welded structures that require calculation fatigue, they shall have a qualified guarantee for impact toughness at room temperature.

When the working temperature of the structure is not higher than 0°C but higher than - 20°C, Q235 steel and Q345 steel should have the qualified guarantee of 0°C impact toughness;

For Q390 steel and Q420 steel, there should be a qualified guarantee for impact toughness at -20°C;

When the working temperature of the structure is not higher than - 20 ℃, Q235 steel and Q345 steel should have the qualified guarantee of - 20 ℃ impact toughness;

For Q390 steel and Q420 steel, it should have the qualified guarantee of - 40 ℃ impact toughness.