Stainless Steel Grade AISI 422 | AISI 616 | EN 1.4935 | DIN X20CrMoWV12-1

AISI 422 | AISI 616 | EN 1.4935 | DIN X20CrMoWV12-1 is a high-alloy stainless steel with a martensitic crystal structure and good corrosion resistance. It is mainly used for parts exposed to high temperatures of up to 649 °C. With the right heat treatment, parts of this steel can also have excellent mechanical properties depending on the cross-section, shape and application.

The steel has good resistance to scale and oxidation. It has excellent creep resistance characteristics at temperatures up to 649 °C. Among similar high-alloy steels with a martensitic structure, stainless steel AISI 422 has the highest electrical conductivity and a moderately high cost price. It has better strength at higher temperatures than similar steel AISI 403.

This grade of metal is used mainly for the production of ladles and blades of steam turbines, as well as in the aerospace industry for the production of high-temperature bolts, valves. Other, less common areas of application of AISI 422 stainless steel are oil refineries, heat pipe factories, pharmaceutical industry, textile industry, nuclear power plants, chemical industry, etc.

Martensitic stainless steel EN 1.4935 is resistant to creep. Additional heavy metal alloying elements give it good strength and resistance to temperatures of 649 °C. Alloying additives of molybdenum, vanadium and tungsten increase the melting point. Like stainless steel AISI 410, this grade has the ability to be heat treated to several different strength levels. Due to its heat resistance, this alloy is often used in the power generation market as components of steam and gas turbines or various other components with high operating temperatures, mainly turbine blades and fastenings. The upper limit of the continuous operating temperature is 580 ℃.

Machinability

Steel is fairly easy to machine, but special care is required to avoid abrasion if the parts are machined with sharp tools. The machining speed should also be slower and more constant, accompanied by a constant feed. For best results, cobalt tools are recommended.

Welding

Although AISI 422 stainless steel is easy to process, it is difficult to weld. To prevent cracking of the welded parts, preheating is mandatory, followed by post-weld unloading of the weld itself at a temperature of 590 °C - 760 °C for 4 hours. The use of welding wire will give the best welding results.

Forging

Regarding forging, parts should be preheated to 650 °C - 760 °C, and then heated to 1040 °C - 1175 °C. Slow cooling to room temperature, followed by annealing and tempering is recommended. If hardening of forged parts is required, preheat them to 650 °C - 760 °C.

Heat treatment

Due to the carbon in its structure, AISI 422 stainless steel can be hardened and strengthened by standard heat treatments used for carbon steels, such as quenching, annealing and tempering. Depending on the desired properties, various combinations of these heat treatments are recommended. For example, the highest corrosion resistance is achieved in the quenched and tempered condition.

Recommended hardening of AISI 422 stainless steel is carried out by heating to 1040 °C, followed by holding and quenching in oil. Complex-shaped parts can be subjected to hardening (hardening at a temperature exceeding the initial temperature of martensite) at a temperature of 340 °C. Tempering should be started after the part has completely cooled to room temperature.

The recommended annealing process to achieve a martensitic microstructure is heating to 730 °C - 780 °C and holding for 4 hours, followed by furnace treatment and air cooling. This treatment achieves a hardness of Rc 21 - 25, which may not be sufficient for some applications. If higher hardness is required, heat to 1040 °C, then cool to 690 °C and hold for 24 - 48 hours, followed by air cooling to room temperature for a hardness of 90 - 95 Rb.

Mechanical properties

Physical properties