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Stainless Steel Intergranular Corrosion Control
Nov 29, 2016

Control of stainless steel intergranular corrosion, 304 stainless steel, 304 stainless steel rust and corrosion in stainless steel intergranular corrosion in some 10%, it will make the adhesion of grains has declined, in the presence of stress, extremely easy to crack, even crumple, and hidden, invisible from its shape. It is also induced by the other main causes of corrosion. Intergranular corrosion of austenitic stainless steel caused by poverty is largely due to grain boundaries Cr, Cr and c easy form chemical compounds, the Cr content.

1, the chemical composition and structure

(1) C content

C content of steel effect of intergranular corrosion of austenitic stainless steel is the most major factor. On one hand, strictly control c and keep carbon content in base metal and welding rod at 0.08%, on the base metal and welding material add stabilizer elements of Ti, Nb, strong affinity with c, carbon prior to Cr bind, producing a stable compound.

(2) dual phase structure

Dual phase structure will greatly increase the capacity of resistance to intergranular corrosion. On one hand, joined the ferrite forming elements, such as chromium, Silicon, aluminum, molybdenum, weld formation of dual-phase structure, on the selected build agent containing ferrite more welding materials.

2, welding technology

(1) the temperature in 450~850℃ the temperature range, especially at 650 ° c is most easily generated intergranular corrosion danger temperature zone (also known as temperature area-sensitive). Stainless steel welding, welds can be taken under laminate, or directly in the back water cooling of the weld, to cool quickly, reducing time in the temperature range, are effective measures for improving corrosion resistance of joints.

(2) increase of welding line energy, will accelerate corrosion of austenitic stainless steel. During the welding process, with low current, high welding speed, short-arc, multiple pass welding method, and reduce the heat. Low heat input, by way of sensitizing temperature quickly enough to avoid intergranular corrosion of heat affected zone.