Welding Stainless Steel to Carbon Steel

Look to the right of this screen and you will see a box that says "Search this forum" and one that says "Search all of CR4"

Type your question in there and you will see this question answered already in one of those searches.

To put it simply, nickel bearing and cheap. Nickel is sticky and ductile, making it of great value in adhering to and asorbing stresses from dissimilar joinings. This alloy is also pretty cheap. It's stronger than 308L, and doesn't tend to work harden like 312.

I am not clear on point as per you why we should not use 309 for welding of 304 or 316. What about welding stainless steel with other materials like CS , LTCS , LOW ALLOY?

309 is used in welding SS to CS to avoid problem of dilution and formation of martensite and to achieve a correct ferrite number. When you weld SS to CS there is a dilution of element of SS ( CR, Ni..) and this cause the formation of hard brittle phase. the other thing is the ferrite number in order to avoid problem of cracking in the weld. The 309 has an higher content of Cr (22%), Ni (up to 15%) vs 304 and 316 (Cr 18% and Ni 10%) and the effect of dilution is reduced. To understand what happened you need to look a the WRC diagram.

have a look at this papers from NIDI:

Welding Guidelines (14018)

I heard from somebody that although 304 carries the required properties to be used as a filler metal but since it is available only in plate material form and not in wire form , so it cant be used as a filler rod. Is it true ??

For 304 material you would use a ER-308 flieer metal.