Common materials used for QU70 crane rails include U71Mn, U75V, etc. The following is a comparative analysis of them:
Chemical composition
U71Mn: Contains a relatively high manganese content, generally between 1.10%-1.50%. The addition of manganese can improve the strength and hardness of steel, while enhancing the toughness and wear resistance of steel.
U75V: In addition to a certain amount of conventional elements such as carbon, silicon, and manganese, it also contains vanadium, and the vanadium content is usually around 0.04%-0.12%. Vanadium can refine grains, improve the strength, toughness and wear resistance of steel, and improve the fatigue resistance of steel.
Mechanical properties
U71Mn: High strength, tensile strength is generally above 880MPa, and yield strength is around 550MPa. It has good toughness, elongation after fracture can reach more than 10%, and impact absorption energy can also meet certain requirements, which makes it have good performance when subjected to impact loads and can adapt to the impact and vibration generated by the crane during operation.
U75V: The tensile strength is usually above 980MPa, and the yield strength is around 650MPa, which is significantly higher than U71Mn. At the same time, U75V also has good toughness, elongation after fracture can reach more than 8%, and impact absorption energy is also high. Due to the effect of vanadium, U75V has better fatigue resistance and can withstand more frequent load cycles. It is suitable for crane rails with harsh working conditions and frequent use.
Wear resistance
U71Mn: It has good wear resistance and can resist the friction and wear between the wheel and the rail to a certain extent. However, its wear resistance is slightly inferior to U75V. During long-term use, the rail surface may show a certain degree of wear and peeling.
U75V: Due to the refinement of grains by vanadium and the increase in the hardness of steel, U75V has better wear resistance. Under the same conditions of use, the wear rate of U75V rails is slower, which can maintain a good rail surface state, extend the service life of the rails, and reduce the frequency of maintenance and replacement of rails.
Processing performance
U71Mn: Good processing performance, easy to process by rolling, forging and welding. During the production process, it can be easily made into rails of various specifications and shapes, and it is not easy to have defects such as cracks during the processing, which is conducive to ensuring the quality and dimensional accuracy of the rails.
U75V: Although the strength is high, the processing performance is also good. The addition of vanadium does not significantly reduce the processing performance of steel. Through reasonable control of processing parameters, U75V can also be smoothly rolled, forged and welded to make crane rails that meet the use requirements.
Application scenarios
U71Mn: Suitable for crane rails under general working conditions, such as crane rails in factories, warehouses and other places where the frequency of use is not particularly high and the lifting weight is relatively small. It can meet the operating requirements of these cranes and has a good cost-effectiveness.
U75V: It is more suitable for crane tracks with harsh working conditions, frequent use, and large lifting weights, such as cranes in ports, mines, large steel mills, etc. Cranes in these places have high requirements for track strength, wear resistance, and fatigue resistance. QU70 tracks made of U75V material can better meet these requirements, improve the safety and reliability of crane operation, and reduce track maintenance costs.