When buying a car bridge, some car owners like to go to the car bridge factory to investigate the scale and production technology of the manufacturer, so as to judge the production level and quality of the manufacturer. For the trailer axle, its main function is to carry the weight of the body, so the requirements for stiffness and toughness are higher.

Then, how does the axle factory guarantee the rigidity or toughness of the trailer axle?

This also depends on the three major production processes of the axle factory: hot rotary rolling, quenching and tempering heat treatment, and medium frequency strengthening treatment. Whether these three production processes meet the standards directly reflects the production level of the axle factory. Next, Darong axle will introduce the functions of these three processes in detail.

1. Hot rotary rolling

Hot rotary rolling is a key process of axle shaft production, and it is also the first process of raw materials after blanking. After hot rotary rolling, the shaft head is preliminarily formed, which provides a certain foundation for the subsequent series of rough machining and finish machining.

However, the main function of hot rotary rolling is to improve the internal mechanical properties of seamless steel tubes.

As we all know, the material of raw materials has a very significant impact on the structure and comprehensive mechanical properties of the finished axle. If the metallurgical quality of raw materials is poor, there will be a large number of non-metallic impurities. When they exist in a continuous, aggregated, network, series, it is easy to cause the continuous splitting of local base metal, and the plasticity and strength will be reduced, In the subsequent processing or use, it is easy to form micro cracks or internal acute angles, which eventually leads to stress concentration and fatigue failure.

The maximum temperature of hot rotary rolling can be close to 1300 ℃, which can break the acicular proeutectoid ferrite in the grain of raw materials, significantly improve and correct the widmanstatten structure in the material, greatly reduce the plastic resistance and deformation energy consumption of raw materials, reduce or eliminate casting defects, and provide a solid foundation for the rigidity of finished axle.

2. Quenching and tempering heat treatment

Here, heat quenching and tempering mainly refers to quenching + tempering, which is also a common treatment process in steel processing.

Darong axle adopts a fully automatic quenching machine tool, whose temperature is generally set at about 865 ℃, which greatly reduces manual intervention and has higher operation accuracy.

During the heating process, the content of austenite in the steel will gradually increase, and then through water cooling, austenite will be transformed into martensite, which is the desired product of the quenching process. Because of its high carbon content, it is very hard in nature, which plays a key role in improving the stiffness and strength of the axle.

However, the stability of martensite that has just been converted is relatively poor, and there is also a part of residual austenite that has not been completely converted. Once it meets appropriate conditions, it will produce transformation, causing axle deformation and changing the machining size. In addition, the quenched axle generally has large residual thermal stress and structural stress, which are often distributed in the corners or some holes. If it is not eliminated in time, it is also easy to cause axle deformation or cracking.

Therefore, although the stiffness and strength of the quenched axle are improved, the toughness is relatively poor. At this time, high temperature tempering should be carried out in time. The tempering process temperature of Darong axle is generally set at about 480 ℃, which can fully reduce or eliminate the quenching internal stress and improve the ductility and toughness of the shaft.

In this way, the strength and toughness of the axle can achieve "double standards".

3. Intermediate frequency induction processing

Although the axle after quenching and tempering heat treatment can meet the load demand in subsequent use, medium frequency induction treatment is still indispensable.

Medium frequency induction treatment is also an enhanced process, mainly for the shaft head. The axle head is used to connect bearings, hubs and other key accessories. If you want to ensure the stable performance output of all accessories under high-speed operation, the performance of the axle head is very important.

The medium frequency induction treatment adopts the non-contact heat treatment strengthening technology, which forms an alternating electromagnetic field by inputting the medium frequency current, and transmits the alternating current to the shaft head through the induction coil to form the induced electromotive force of the same frequency. The heating is rapid, and can reach 800-1000 ℃ in a few seconds. The heat transmission depth is large, the internal and external temperature difference is small, and the temperature field is uniform. It can not only improve the strength and toughness of the axle to a greater extent, but also improve its magnetism, corrosion resistance Oxidation resistance plays a positive role in improving its safety and stability and prolonging the service life of the shaft.

Axle factories that can do the above three processes well can basically rest assured of the strength and toughness of their products. It is worth mentioning that in addition to the above three processes, Darong axle has also set up a special fatigue test workshop to spot check the finished products. Only after passing the fatigue test for millions of times and the data is qualified, can it be successfully delivered to the factory, which is also a guarantee for the strength, toughness and fatigue resistance of the axle.

Of course, to determine the quality of the axle and the production strength of the manufacturer, we need to comprehensively consider multiple factors such as processing accuracy, accessory quality, assembly technology, personnel quality, etc., but if the strength and toughness meet the standard, the service performance of the finished product can be guaranteed to a great extent. Car owners can pay more attention when inspecting the axle factory.