- •Aluminum
- •Welding
- •Cutting
- •Consumable electrode methods
- •Types of flame
- •Safety issues
- •Costs and trends
- •Quality
- •Operation
- •Flux-cored arc welding
- •Electrode
- •Spot welding
- •Applications
- •Electrical notes
- •Processing and Equipment
- •Effects
- •Welding power supply
- •Classification
- •Transformer
- •Submerged arc welding
- •Advantages
- •Robot welding
- •Welding gun and wire feed unit
- •Operation
- •Hyperbaric welding
- •Equipment
- •Energy beam
- •Solid-state
- •Shielding gas
- •Electroslag welding
- •Benefits
- •Short-circuiting
- •Modified short-circuiting
- •Pulsed-spray
- •History
- •Plasma arc welding
- •Gas metal arc welding
- •Laser beam welding
- •Resistance
- •Arc welding
- •Power supplies
- •Geometry
- •Processes
- •Heat-affected zone
- •Distortion and cracking
- •Electrogas welding
- •Operation
- •Weldability
Weldability
The quality of a weld is also dependent on the combination of materials used for the base material and the filler material. Not all metals are suitable for welding, and not all filler metals work well with acceptable base materials.
Steels
The weldability of steels is inversely proportional to a property known as the hardenability of the steel, which measures the probability of forming martensite during welding or heat treatment. The hardenability of steel depends on its chemical composition, with greater quantities of carbon and other alloying elements resulting in a higher hardenability and thus a lower weldability. In order to be able to judge alloys made up of many distinct materials, a measure known as the equivalent carbon content is used to compare the relative weldabilities of different alloys by comparing their properties to a plain-carbon steel. The effect on weldability of elements like chromium and vanadium, while not as great as carbon, is more significant than that of copper and nickel, for example. As the equivalent carbon content rises, the weldability of the alloy decreases. The disadvantage to using plain carbon and low-alloy steels is their lower strength — there is a trade-off between material strength and weldability.
Stainless steels, because of their high chromium content, tend to behave differently with respect to weldability than other steels. Austenitic grades of stainless steels tend to be the most weldable, but they are especially susceptible to distortion due to their high coefficient of thermal expansion. Some alloys of this type are prone to cracking and reduced corrosion resistance as well. Hot cracking is possible if the amount of ferrite in the weld is not controlled — to alleviate the problem, an electrode is used that deposits a weld metal containing a small amount of ferrite. Other types of stainless steels, such as ferritic and martensitic stainless steels, are not as easily welded, and must often be preheated and welded with special electrodes.
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____________ В.П. Павлов