Stainless steel threaded pipe fittings are divided into two types: imported and domestic. Domestic materials. Since they use the European (iso) system, they are more intuitive and not prone to problems. Now we will focus on some of the issues that need attention in imported stainless steel:
1. Material standards
Now, the imported stainless steel standards that we often see are the American asme standard sa240, the astm standard a240, and the Japanese jis standard sus; the frequently used brands are 304, 304l, 316l and so on. Let's take 304 as an example to illustrate their representation methods: the material in the jis standard is relatively simple, which is sus304; there are several representations of asme and astm: sa240-304, sa240tp304, a240-304, a240tp304, in fact, Adding in the middle means the same as adding tp. We mentioned that there are 304l materials in the front, where l is the suffix, which means that the carbon content is low; you can often see h, which means that the carbon content is higher, and it is mainly used in higher temperature occasions; in addition, the common ones are There is n, which means adding element n to increase strength. Sometimes, we can also see in the back: 2b, no.1 and other suffixes, these suffixes indicate the surface condition of the material; 2b indicates the steel plate with a good surface after hot rolling and cold rolling; 2d indicates After hot rolling and cold rolling, the surface of the steel plate is general; no.1 indicates the hot rolled surface.
2. About the substitution of materials
In the minds of many people, it is a matter of course for the material to be “higher to lower, and thicker to thin”. There is no need for multiple management. In fact, this view is wrong. Let’s take 304, 304l, and 304h as examples to illustrate : Generally speaking, 304l has a lower carbon content and better corrosion resistance than 304, so it can be used instead of 304 material. It is true that 304l meets the requirements of 304 and is better than 304. It seems that it can automatically replace 304, but from the perspective of mechanical properties, the strength of 304 is higher than 304l. When designed according to 304, replacing 304l with 304 will result in insufficient strength; in addition, In my country's pressure vessel standard gb150-1998, Article 4.1.6 stipulates that when the service temperature of austenitic stainless steel is higher than 525℃, the carbon content in the steel should not be less than 0.04%. Therefore, it is wrong to think that 304l can be used in place of 304. Whether it can be used is related to the occasion of use, and in accordance with the regulations, we have no right to "material substitution". Only the original design department can have the right to "material substitution." "work.
