Stainless Steel Welding Knowledge
Stainless steel has been coined as is alloy steel which contains at least 11.5% chromium. When oxygen in air reacts with chromium in stainless steel, a thin but dense film of chromium oxide forms on the surface of stainless steel, making it corrosion resistant. and prevent reaction with oxygen There are 5 types of stainless steels, depending on the type of addition of other alloys.
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type of stainless steel
- Austenitic stainless steels – This is the most widely used grade, with groups 200 and 300, type 304 being the most common. The first added alloying elements are chromium and nickel.
- Ferritic stainless steel group – This is a magnetic stainless steel with low carbon content and chromium as the main alloying element may be between 10.5 %-27% and contains little or no nickel as an ingredient. can not harden Representatives of this group are 405,409,403,422 and 446.
- Martensitic stainless steel group Martensitic – A magnetic stainless steel with a mixture of 12-14% chromium and a moderate carbon content. It contains about 0.2-1% molybdenum, no nickel. This family of stainless steels can be hardened by heating and then quickly cooling (Quenching) and by annealing (Tempering) can reduce hardness. similar to carbon steel and found important applications in the manufacture of cutting machines. Aircraft industry and general engineering Representatives of this group are types 403,410,416, and 420.
- Duplex stainless steel group (Duplex) – has a mixed structure between Ferritic and austenitic structures with alloying elements ranging from 19-28% chromium and above 5% molybdenum and less than 5% nickel have been found to be very active, especially in atmospheric environments. of chloride The numbering system of stainless steels in this group is not included in the 200,300 or 400 range.
- Stainless steel is hardened by crystallization. Add elements such as Aluminum, which is strengthened by melting and heat treatment is curing. They are further stratified into subgroups. It is a stainless steel that is hardened by martensitic precipitation. semi-austenitic and Austenitic
for high quality welds Joints must be clean and dry (CLEAN AND DRY), POWER BRUSHING, DEGREASING, PICKLING, GRINDING OR MORELY. WIPING) depends on the type and amount of dust. Some specific recommendations are
get rid of moisture By heating (HEATING) or by blowing (BLOWING) with dry air. (Beware of humidity in the wind: AIR LINE) in high humidity conditions. Moisture can collect on the welding workpiece at night.
FLAME BEVELING and MACHINING may remain contaminated. or oxide film to be removed
Remove organic contaminants such as PAINTS, ANTI SPATTER COMPOUNDS, GREASE PENCIL MARKS, CUTTING COMPOUNDS, adhesion from protective paper, and soap used for testing marks. leak
Avoid zinc contamination from brushes or tools used on galvanized steel. Zinc contamination causes cracking. Use only stainless steel wire brushes that are used on stainless steel.
Avoid copper contamination from abrasion. Stainless steel over copper on the HOLD DOWN FIXTURE. Copper contamination causes cracking.