Abstract
An experimental study was made on the weldability of 18Cr-10Mn stainless steels containing high concentration of nitrogen up to about 0.8%, prepared by a high-pressure melting process in nitrogen atmosphere. Main results obtained are as follows.
(1) In the arc welding of high nitrogen l8Cr-10Mn stainless steels, if ordinary welding conditions recommended for welding commercial austenitic stainless steels are adopted, we shall usually be able to get excellent and sound welded joints.
(2) In case of welding by using the electrode having the same composition, the tensile strength of welded joints increases in proportion to the nitrogen content of base metals. This strengtheing in the welded joints depends upon the extent of nitrogen diffusion, which occurs from the base metal to the welded metal.
(3) The decrease of impact strength in heat-affected zone scarcely occurs even in the steel containing about 0.8% nitrogen.
(4) While the base metal is melting, the nitrogen contained in the base metal diffuses and blows out of the metal a little. Consequently, in the base metal containing high concentration of nitrogen i.e. more than 0.65%, blowholes in the weld deposit increase and the concentration of nitrogen in the heat-affected zone decreases a little.
(5) But, the decrease of nitrogen content in the base metal occurs only in the limited portion near the weld bond, and the amount of the decrease is small. Therefore, in the steels containing nitrogen less than about 0.65%, the decrease of the nitrogen content scarcely influences the mechanical properties and the microstructures of the welded joints.
