Regarding the issue of when to perform spectroscopy on alloy steel bolts
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Today, the company received a batch of 35CrMoA/35# double-headed bolts, all with specifications of M33×190 or less. These bolts are used to secure the valve flanges of buried circulating water pipes (with a working pressure of around 5 kilograms). Some people suggest that spectral analysis should be performed, but after searching through numerous sources, no evidence supporting such an analysis was found. I hope experts can help clarify this: 1. Under what conditions of use and for what types of materials are spectral analyses necessary for these bolts?； 2: What is the basis or current standard for conducting spectral analysis to determine components? Thank you
If it is used on flanges at 0.5 Mpa, ordinary screws will suffice; or if there is a material certificate and a quality certificate indicating that it was produced by a reputable manufacturer, then spectral testing is not necessary. For critical connections, spectral testing is required when the material of the screws is unknown.
Strictly speaking, it is advisable to conduct spectral analysis on samples of all bolts made of alloy steel upon their arrival; nowadays, with spectrometers available, material testing is very convenient. Material analysis is necessary for important connection bolts used under high-temperature (above 250°C), low-temperature (below -29°C), and cryogenic conditions.