“L” Grade filler metal

Date 11-23-2011 15:44

A2. Classification System
A2.1 The chemical composition of the filler metal is
identified by a series of numbers and, in some cases, chemical
symbols, the letters L, H, and LR, or both. Chemical
symbols are used to designate modifications of basic alloy
types, e.g., ER308Mo. The letter “H” denotes carbon content
restricted to the upper part of the range that is specified
for the standard grade of the specific filler metal. The letter
“L” denotes carbon content in the lower part of the range
that is specified for the corresponding standard grade of
filler metal. The letters “LR” denote low residuals.

By vdao3004 (**)

Date 11-23-2011 16:15

kilgoretrout,

Big help, and Can you tell me what Code or specification which is coming from?

Thanks alot.

By 803056

Date 11-28-2011 20:25 Edited 11-28-2011 20:33

You can refer to the filler metal specifications if you are interested in filler metal classification systems. The information is typically listed in the annex.

Carbon has a couple of affects. It is a strengthening agent when added to steel. ASME typically allows for higher stresses at elevated temperatures when comparing the high carbon alloy stainless (304H for example) when compared to the low carbon material (again, 304L grade).

The flip side is that carbon is a bad actor when sensitization is a concern in wetted system where halides like chlorine are involved. Reducing carbon content, i.e., L grades, reduced the tendency to form M23C6 (on in our case chromium carbides) in the HAZ. Sensitization leads to stress corrosion and stress corrosion cracking in the HAZ along the grain boundaries.

Failure to use matching grades of filler metal will reduce the allowable stress at high temperatures or promote, or at least not enhance, the resistance to sensitization in wetted systems where it is a concern.

Best regards - Al