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Material Weldability Data

Preface: Due to the complex nature of the subject matter, the following information is intended as a general summary guide in welding a particular alloy utilizing the gas tungsten arc or plasma arc process. Many variations and combinations of materials exist and thus welding applications are usually analyzed on a case by case basis.
Stainless Steels 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.
Carbon Steel 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 treatment.
Copper Alloys 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.
Aluminum Alloys 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.
Titanium alloys 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 of both.
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