Features welding of stainless steel 12Kh18N10T

General characteristics

Steel 12X18H10T refers to the well-welded materials. However, the raw after welding the weld will be prone to intergranular corrosion. It develops only in the heat affected zone, where the temperature is 500−800°C. Of steel in this critical temperature regime fall chromium carbides at the grain boundaries of austenite. This can cause adverse effects during use. More durability seam achieve using a particular method of welding which eliminates or substantially reduces the effect of carbide precipitation in the weld.

Features

During welding of austenitic type stainless steel it is important to note that he has significant differences in the physical characteristics of the properties of carbon steel. Its coefficient of thermal expansion is about 50% higher, and the specific resistivity is almost six times greater at 100 °C below the melting point, the thermal conductivity is about one-third from the same carbon.

Welding methods

Manual arc welding is used most often when the material thickness is over 1.5 mm. Arc welding-inert gas (TIG) tungsten electrode is used for welding thin sheets and pipes. Another method of arc welding with consumable electrode in inert gas. A method such as pulsed arc welding in inert gas consumable electrode used for welding sheets with a thickness of about 0.8 mm. the short arc Welding with consumable electrode in inert gas is used for joining metal sheets with a thickness of 0.8−3 mm. More widely used plasma-arc welding — plate thickness here does not really matter.

The final treatment of welds

After welding on the weld surface remains porous oxide layer which contains chromium carbides. This layer makes the affected welds to corrosion. In addition, in the base material below this layer, the chromium content is reduced. To enhance the resistance to corrosion, loose top layer and the zone with a reduced content of chromium is removed by various methods.

Mechanical processing methods

These include sanding bands, circles, brushes made of stainless steel and shot steel. Please note that the tool for machining of carbon steel cannot be used for stainless steel. And use steel shot or sand when treated carbon steel.

Etching

It is considered the most effective method post-processing of the welds. If etching is done correctly — it gives the opportunity to remove and loose top layer, and the area with lower chromium content. Etching is performed using surface coating or dipping in a solution or coating paste. Typically, when etching using a mixture of acids in the following proportions: 8−20% HNO3 and 0.5−5% HF in water. The time of etching depends on acid concentration, temperature, thickness, scale and type of rental.

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