General Characteristics

12x18n10t steel is a well-welded material. However, the untreated weld after welding will be prone to intergranular corrosion. It develops only in the heat affected zone, where the temperature reaches 500-800 ° C. Chromium carbides precipitate out of the steel at this critical temperature range along the boundaries of austenite grains. This can cause adverse effects during use. Greater resistance of the weld is achieved by using a particular welding method that eliminates or significantly reduces the effect of carbide precipitation in the weld.

Features

When welding the austenitic type of stainless steel, it is important to take into account that it has significant differences in physical characteristics from the properties of carbon steel. Its coefficient of thermal expansion is about 50% higher, and specific electrical resistance is almost six times higher, the melting point is 100 °C lower, thermal conductivity is about one-third of that of carbon grades.

Welding techniques

Manual arc welding is most commonly used for material thicknesses over 1.5 mm. Tungsten inert gas (TIG) arc welding is used for welding thin sheets and pipes. Another method is arc welding with a melting electrode in inert gas. Such a method as pulsed arc welding in an inert gas with a melting electrode is used for welding sheets with a thickness of about 0.8 mm. Short arc welding with a flaming electrode in inert gas is used for joining sheets with a thickness of 0.8-3 mm. Plasma welding is more widely used - sheet thickness does not matter here.

Final processing of welds

After welding a porous oxide layer is left on the surface of the weld, which contains chromium carbides. This layer makes the weld vulnerable to corrosion. In addition, the chromium content in the base material underneath this layer is reduced. To increase corrosion resistance, the loose top layer and the area with reduced chromium content are removed by various methods.

Mechanical Treatment Methods

These include grinding belts, wheels, brushes made of stainless steel and steel shot. Note that carbon steel tools cannot be used on stainless steel. And steel shot or sand cannot be used when machining carbon steel.

Etching

It is considered the most effective way to finish welds. If pickling is performed correctly, it is possible to remove both the loose top layer and the area with low chromium content. Etching is performed by surface application or immersion in a solution, or paste coating. Etching is usually performed using a mixture of acids in the following proportions: 8-20% _HNO3 and 0.5-5% HF in water. Etching time depends on the acid concentration, ambient temperature, scale thickness and type of rolled material.

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The range of stainless steel products in stock of Evek GmbH meets international quality standards. A wide range of products of any parameters, comprehensive advice of our managers, reasonable prices and on-time delivery determine the face of our company. We accept wholesale and retail orders. With wholesale purchases there is a system of discounts.