Effect of heat treatment for submerged arc welding on corrosion resistance in sea water at different temperature

Abstract EN

This paper is aimed to study the effect of heat treatment for submerged arc welding joint in the dimension of 100*50*16 mm on corrosion resistance in sea water at different temperatures.

Submerged arc welding is carried out for Low carbon steel St37 under welding conditions of 750 Amper DC current straight polarity (DCSP) and 32 volt, welding wire type EM12K.

70- 18 in diameter of 4mm and wire speed of 4.2m/min with Flux .

A joint geometry of single V at 45P o P butt joint welded two passes was adopted.

The welded pieces were tested by X-ray radiography and faulty pieces were excluded.

After welding, the joints without defects have be submitted to heat treatment including quenching where the joint heated to 900 C for one hour then water cooled and followed by normalizing heat treatment by heating to 900 C for one hour then air cooled.

Corrosion specimens prepared from the weld joint with the dimensions of (15*15*3) mm according to ASTM G71-31 then optical microscopy was used to observe the welded joint microstructure.

Corrosion tests were investigated by electrochemical potential state cell in a prepared salt water (sea water) at different temperatures (25, 50.

75) C.

Tafle equation was adopted to calculate the corrosion rate.

Results show that heat treatment contributed in reducing corrosion rate and normalizing gives better results than quenching but the effects of media temperature give the opposite