Welding Characteristics of Precipitation Hardening Martensitic Stainless Steel

Welding Characteristics of Precipitation-Hardened Martensitic Stainless Steel

Stainless steel is an ideal material for a wide range of industries due to its corrosion resistance and strength. Its corrosion resistance can be enhanced further by introducing alloying elements and heat treating processes. One of the more popular heat treating processes is precipitation hardening. This process is most commonly used to produce martensitic stainless steel. Martensitic stainless steel is a type of ferritic stainless steel that is strengthened and hardened through heat treatment.

The mechanized welding of precipitation-hardened martensitic stainless steel is an effective and efficient way to join components and construct structures. When welding precipitation-hardened martensitic stainless steel, a number of factors must be taken into consideration in order to have high quality welds. One of the first factors that must be considered is the welding process itself. Commonly used welding processes for precipitation-hardened martensitic stainless steel are gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and shielded metal arc welding (SMAW). The type of welding process selected should depend on the size and location of the weld as well as the application of the weldment.

In order to achieve optimal weld quality in precipitation-hardened martensitic stainless steel, it is important to use the correct filler metal. A filler metal with a low hydrogen content is typically desirable for the higher strength and corrosion resistance levels of precipitation-hardened martensitic stainless steel. It is also critical to ensure that the filler metal and base metal match when it comes to alloying elements such as chromium, nickel, and molybdenum.

Prior to welding precipitation-hardened martensitic stainless steel, proper preheating and postheating operations are essential. Preheating is advised at temperatures between 400°F and 600°F in order to reduce thermal stresses and prevent excessive cooling rates. The postheating process is necessary to ensure that the welding parameters are consistent and are able to reach the desired degree of strength and corrosion resistance.

The original heat treating procedures of the precipitation-hardened martensitic stainless steel should be of top priority when welding. When these parameters are followed, the welding process should be straightforward. If the original heat treating process is unknown, an annealed filler metal should be used in order to avoid any problems with cracking or other defects.

Finally, proper cleaning of the joint edges is important prior to welding as well as appropriate selection of an interlayer or backing strip. The backing strip should be applied in order to prevent overwelding and also for the assurance that proper side-to-side joint penetration will occur.

By taking into consideration the welding process, filler metal, pre- and post-heat treating operations, the original heat treating procedures, and the joint cleaning and backing strip operations, it is possible to obtain high quality welds in precipitation-hardened martensitic stainless steel. The quality of welds achievable in these types of materials has allowed it to be used in numerous applications across multiple industries.

Welding of Precipitation Hardening Martensitic Stainless Steel

Precipitation hardening martensitic stainless steel is a kind of stainless steel used widely in a variety of products due to its excellent corrosion resistance and mechanical properties. Welding this stainless steel is desirable to provide bonding integrity between parts, and in manufacturing and fabrication processes.

Precipitation hardening stainless steel is closely related to its regular martensitic counterpart. It can be hardened by a series of heat treatments and usually is heat treated before welding for maximum service strength. In general, pre-heat prior to welding is strongly recommended. The heat also removes stresses and reduces the chance of cracking. Pre-heat temperatures are usually from 600 to 900°F (316 to 482°C) depending on material thickness and overall workpiece size.

When welding precipitation hardening martensitic stainless steel, it is important to use the correct filler metal. Typically, an AWS E/ER430 or 309 type filler metal is often used, since these are closely related to the alloy being welded. Special attention should be given to maintain the preheat and interpass temperatures for optimum results. The TIG process is preferred due to its control over heat.

Post-weld heat treatment (PWHT) should also be done to achieve maximum service strength from the weldment. Typical solution temperatures range from 1450 to 1550°F (788 to 843°C) with quench on a specially designed fixture or in a suitable quenching medium.

Welding precipitation hardening martensitic stainless steel requires expertise and experience. Depending on the material properties being welded and desired outcome, any welding of stainless steels may require special attention and welders should be aware that improperly performed welding may actually reduce the corrosion resistance of the material.