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How to prevent cracks in crane wheel sets

When manufacturing crane wheel sets, cracks can occur in the wheel set. What exactly is the reason for this? Crane wheel set manufacturers based on years of production experience summed up the following points:

1. wheel set to improve the value of hydrostatic pressure  

As can be seen from the previous analysis, the generation of cracks and the stress situation and the plasticity of the material, plasticity is a state of the material, which depends not only on the organization of the deformed object, but also on the external conditions of deformation (including the state of stress, deformation temperature and deformation speed).  

Three-way isostatic stresses not only do not cause cracks in the crane wheel set to expand. Even small unoxidised cracks in the deformation can be forged under high three-way compressive stresses. For low plasticity materials the use of counter-thrust extrusion and upsetting with sleeves are used to prevent cracking by increasing the value of hydrostatic pressure. The reduction of additional tensile stresses during extrusion and drawing length is a very effective measure to prevent cracking (e.g. hydrostatic extrusion). 

2. Strict control of deformation temperature in wheel sets   

Deformation temperature has an important influence on the plasticity of the material, low temperature, cold deformation hardening serious, plasticity decline; temperature is too high, easy to overheat, overburning. Magnesium alloy and other dense hexagonal lattice of metal materials at room temperature only a set of slip surface (i.e. base surface), when the temperature exceeds 200 ℃ after the increase of new slip surface, therefore, should ensure that in the process of deformation, can be fully recrystallized, and as far as possible in the state of single-phase deformation.

3. Suitable strain rates are used for wheel sets  

The strain rate has a great influence on low plasticity materials, and suitable forging equipment should be selected according to the specific material. For example, a factory MB5 magnesium alloy in the hammer on the hot forging easy to crack, and in the water press with the same temperature forging is not forging crack. The reason is that the magnesium alloy recrystallization process is slow, high speed deformation easy to crack. Alloy in the press deformation recrystallization temperature of 350 ℃, and in the impact load need to be deformed at 600 ℃ to obtain a complete re-crystallization products organization


4. Wheel sets require intermediate annealing if necessary  

    When the degree of cold deformation is too large, it is often easy to cause cracking in crane wheel sets and intermediate annealing is required to eliminate some of the defects caused by hardening and deformation.

5. Hot press deformation of wheel sets  

    When hot deformation is used, the defects caused by the deformation are usually partially eliminated due to the smooth recrystallisation process, thus increasing the plasticity.

6. Wheel set to improve the organisation of the billet  

    In order to improve the plasticity of the material, low melting point substances and brittle compounds at the grain boundaries should be avoided from the organisation.

7. Wheel set using high temperature homogenisation  

    High-temperature homogenisation can improve the non-uniformity of the organisation and increase the plasticity of the material.  

    Through these measures, can come to prevent crane wheels to avoid cracks, to ensure the quality of crane wheels.





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