Stainless steel types
1. What is stainless steel and stainless acid-resistant steel?
A: The "chromium" content of the main elements in the metal material (Need to add nickel, molybdenum and other elements steel that can pass steel in a passivity state with stainless steel properties. Acid-resistant steel means Corrosion resistant steels in strong corrosive media such as acids, alkalis, and salts.
2. What are austenitic stainless steel types? What are the commonly used stainless steel grades?
A: Austenitic stainless steel is the most widely used and the most variety. Such as:
<1>18-8 Series: 0Cr19Ni9 (304) 0Cr18Ni8 (308)
<2>18-12 Series: 00Cr18Ni12Mo2Ti (316L)
<3>25-13 Series: 0Cr25Ni13 (309)
<4> 25-20 Series: 0Cr25Ni20 and so on
3. Why does have difficulty in welding stainless steel wire?
The main process difficulty is:
<1> Stainless steel wire has strong thermal sensitivity and stays in the temperature range of 450-850°C As the time is longer, the corrosion resistance of the weld and heat-affected zone is seriously reduced.
<2> Hot cracking easily occurs.
<3> poor protection, high temperature oxidation.
<4> The coefficient of linear expansion is large, resulting in a large welding distortion.
4. Why does the austenitic stainless steels take effective process measures when welding ?
A: General process measures include:
<1> According to the chemical composition of the base metal, strictly select the welding material.
<2> Small current. Quick soldering; Small wire energy, Reduce heat input.
<3> fine diameter welding wire, welding rod, no swing, multi-layer multi-channel welding.
<4> Forced cooling of welds and heat affected zone reduces 450--850°C residence time.
<5> TIG weld back argon protection.
<6> Welds in contact with corrosive media are finally welded.
<7> passivation of welds and heat affected zone.