Welding of stainless steel

Welding methods

When welding you need to consider the difference of physical properties, austenitic stainless steel or carbon rolled. Electrical resistivity of the austenitic steel alloyed by anyone and chromium is about 6 times higher and the conductivity is much smaller coefficient of thermal expansion along the length of 50% more. Welding of austenitic steels can be performed by any method. Manual arc welding is usually used in the case if the material thickness does not exceed 1.5 mm. Arc welding with tungsten electrode in inert gas suitable for connections of tubes and thin sheets. For sheets with a thickness of 0.8 mm suitable pulsed arc welding with consumable electrode in inert gas. Sheets with a thickness of 0.8 — 3 mm is necessary to connect the arc welding with spray metal transfer. Arc welding with consumable electrode in inert gas at very high efficiency. Sheets thicker than 3 mm it is better to connect in this method. Arc-welded submerged arc welded construction of thickness more than 10 mm. Plasma welding is versatile and used very widely.

Seams

If I may say so, welding «churns» the metal, forming on the surface of the weld porous oxide layer is depleted in chromium. Because of the looseness of this layer makes the material vulnerable to corrosion. In order to avoid this, you need to handle the seam after welding.

Heat treatment

In our case, the heat treatment is the dissolution of a loose layer, which occurs at temperatures over 1000 °C. the Suture then becomes smooth and less prone to corrosion.

Mechanical methods of final processing

We must remember that to apply to only those workers facilities that are provided for processing stainless steel. These include grinding wheels, belts and brushes that are used for processing stainless steel. It is worth noting that carbon steel is unacceptable to treat sand or steel fractions.

Etching

This is the most effective way of treatment of welding seams on stainless steel. If etching is done correctly, the removed friable oxide layer depleted in chromium. Etching occurs so. for steel or paste is applied or is dipped in a special solution. In most cases, for etching mixture of acids: 8 to 20% nitric acid and 0.5 to 5% hydrofluoric acid. How long is the etching of austenitic stainless steel depends on the acid concentration, the thickness of the oxide and temperature. In order for a weld to be of high quality, requires an additional grinding or polishing, which significantly increases the corrosion resistance.

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