||302/304/309/316/321. All 300 series stainless steels have a high degree of weldability with the exception of 303/303SE which
contain additives for ease of machining. 400 series stainless steels are often weldable but may require post weld heat treatment.
Straight argon gas, Argon/Hydrogen, or Argon/Helium gases are employed according to the benefit required.
||The material specification of "carbon steel" is extremely vague as many grades exist. Low carbon steels may have high weldability
and consistency if the material specification has tight tolerances. The addition of free machining additives usually has
a detrimental effect on weldability. Susceptibility to cracking is an issue with high carbon steels and may require heat
||Oxygen free/Electrolytic tough pitch/Deoxidized/Beryllium coppers; these pure copper material have a high degree of weldability,
the addition of other elements may present challenges and cause weld outgassing. It is recommended to remove any heavy oxide
that might be present to improve weldability. Weld soundness decreases as oxide content increases. It is important to recognize
that low melting elements such as lead, tellurium, sulfur, and zinc have an adverse effect on weldability and make the material
susceptible to hot cracking. Welding gases normally employed are argon/helium mixtures.
||The weldability of aluminum material varies very much according to the alloy involved. There are two basic issues involved
in welding Aluminum; 1) Removal of surface oxides in order to create a clean surface to weld, 2) Preventing cracking of the
material after welding. Preweld cleaning of aluminum is essential for optimum weld quality. A source of contamination is
the oxide layer present on all aluminum alloys. Base metals such as 1100 and 3003 have a relatively thin oxide coating as
fabricated, while 5xxx and 6xxx series alloys generally have a thick dark oxide coating. The thicker the oxide, the greater
its adverse effect on weld metal flow, solidification, and degree of porosity. Some aluminum alloys require a filler material
to prevent cracking. Alloys 1100/2219/3003 have been successfully welded in production using direct current (DC). The 6061
alloy causes more difficulties and is usually welded with a filler material (4043, 718 or other) using AC which provides a
cleaning action but may limit automation. Shield gas is normally argon or helium.
|Nickel Base Alloys
||Inconel 600/625/718/750. Most nickel base alloys possess a high degree of weldability. The precipitation aged hardened group
however may require a post weld heat treatment. Monel, Hastalloy and other alloys may present challenges with surface oxides
and molten material flow. Argon/Hydrogen gas mixes are generally used to reduce oxides back into the base metal. The net
effect is to provide a oxide free weld pool with greater fluidity that wets out and flows more consistently.
||Unalloyed titanium is available in several grades ranging in purity from 98.5 to 99.5% and generally possess good weldability.
All grades are usually welded in the annealed condition. Welding of cold worked alloys anneals the heat affected zone (HAZ)
and negates the strength produced by the cold working. Titanium is often post weld heat treated or cold worked to restore
the mechanical properties. Titanium should have no discoloration after welding which shows contamination when the metal was
hot. Trailing shields or welding in a chamber are often employed. High shield gas purity is most desirable. The shield
gas should have a dew point of -60degrees F or lower. The hose(es) used for shielding gas should be clean, nonporous, and
flexible. Because rubber hose absorbs air, it should not be used. Shield gases employed are argon or helium or a combination