Decarburization layer exceeded
The decarburization layer exceeded the standard. The decarburization layer is also a Class A project. Due to decarburization, the surface hardness and strength of the parts are greatly reduced, which seriously affects the surface contact strength and fatigue life of the fasteners, especially the damage to the threaded parts. The main causes of decarburization are decarburization of raw materials, decarburization during material reforming, and decarburization during product heat treatment.
Oversize. Fasteners are common parts, and the interchangeability requirements are high. The size difference will directly affect the interchangeability and even affect the joint strength, anti-loose performance or life. The main reasons for the size failure:
1. The process is not properly controlled. In order to save the material, the part size is controlled near the lower limit. The equipment is not adjusted in time during the production process, and the tool is used.
2. The inspection is weak, the process inspection and the factory inspection are not strict, so that some unqualified batches pass;
3. It is not possible to periodically perform metrological verification on the measuring tool, or even use a gauge that exceeds the wear limit.
Fasteners are a general-purpose basic component with a large amount of surface. The quality and reliability of the fasteners play an important role in the performance and structural safety of the main engine. Especially the quality of high-strength fasteners should be paid more attention.
Thread inspection tolerance zone principle
Tolerance belt principle for thread inspection: In the middle, there is a tolerance band diagram along the thread profile and a table of diameter tolerance values.
Most of the technicians in China believe that the thread gauges should be within the tolerance zone specified by the thread standard, and the thread quality should be no problem. When the quality of the thread of the qualified product was found to be very poor, they were at a loss and did not know where the problem was.
In fact, the thread is a complex geometry with many technical parameters. If you want to fully control the quality of the thread (using the tolerance band principle), you need to measure all the parameters of the thread, which takes a lot of time and high cost of inspection, which is not feasible in actual production. Moreover, in different occasions, the various parameters of the thread have different functions and different requirements, and some parameters can be guaranteed by the production process without separate inspection.At present, the thread pass and stop gauges used in China are derived from the Taylor principle invented by the British in 1905. Its advantage is that it is economical and can guarantee assembly; the disadvantage is that the quality assurance level of the thread is low, and there are many technical loopholes. China should seriously study and learn from the US thread inspection system technology (standard) to improve the manufacturing level of China's thread.
T-Bolt, known as hammer bolt in European standard, is made of galvanized or nickel plated carbon steel surface. T-shaped bolt can be directly put into the aluminum profile groove. During installation, it can be automatically positioned and locked. It is often used in conjunction with flange nuts. It is a standard matching connector when installing corner pieces. It can be selected according to the profile groove width and different series of profiles. T-bolts are movable foundation bolts.
T-Bolt,T Bolt,T Bolts,T Head Bolt
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