Weldability of chromium martensitic stainless steel

Welding of Chromium Martensitic Stainless Steel

Chromium martensitic stainless steels are extremely difficult to weld and usually require pre-and post-weld heat treatments to restore the mechanical properties and microstructures of the weld and heat-affected zone. These alloys are typically used in applications that require a high degree of toughness and wear resistance, since they typically exhibit superior properties in these areas compared to austenitic stainless steels. However, these alloys are also known to suffer from problems such as cracking and heat-affected zone embrittlement when welded, which is why extra care must be taken during welding.

The first step in welding chromium martensitic stainless steels is selecting a welding procedure that will produce the deepest joint penetration possible. The welding current should be kept low, typically between 30 and 50 amps depending on the thickness of the material being welded. If the current is kept too high, there is a risk of overheating the material and causing weld cracking. It is also important to note that these alloys tend to suffer from weld shrinkage, so a number of welding bead passes may be necessary in order to fill the joint completely.

After welding is complete, it is a good idea to perform a post-weld heat treatment to reduce the hardness of the heat-affected zone and relieve any residual welding stresses. Typically, this involves heating the welded section of the material to a temperature of 1050-1100°F for a period of 30-45 minutes. After the heat treatment, the part should be cooled in air or oil to prevent any residual stresses from developing.

Finally, it is important to note that chromium martensitic stainless steels are known to have problems with stress corrosion cracking in certain corrosive environments. Therefore, it is always a good idea to use corrosion resistant alloys or coatings to ensure that the part remains corrosion resistant in its intended application.

In conclusion, chromium martensitic stainless steels are difficult to weld but they can be successfully welded with proper technique and post-weld heat treatment. It is also important to note that these alloys need to be protected against corrosion in order to ensure their long-term service life. By following the correct welding procedures, the correct post-weld heat treatments and the correct corrosion protection techniques, chromium martensitic stainless steel can be safely welded and used in a wide range of applications.

Welding of chromium martensitic stainless steel

Chromium martensitic stainless steel is widely used in many fields because of its excellent corrosion resistance, high mechanical properties and high temperature oxidation resistance. But its high strength, hardenability, easy to precipitate intermetallic compounds and etc., will cause embrittlement of welded joint, detract from the overall performance of product, even cracking. Therefore it is necessary to pay attention to the welding of chromium martensitic stainless steel.

1. Welding process and operation

When welding chromium martensitic stainless steel, first use the following two measures to eliminate the adverse effects of martensite transformation heat affected zone.

① Preheating: The preheating temperature should not be lower than 150℃, and it is better to master up to 200℃.

② Inter-pass temperature: Generally control not more than 150℃, local should not exceed 200℃. It is better to prevent the inter-pass weld from continuously heating.

The welding parameters selected for welding should be adjusted according to plate thickness. Generally choose a lower current, slower welding speed and wider welding groove. When welding, try to completely eliminate the bridge welding section, especially for the eutectic carbides and carbide islands of the steel plate.

2. Welding material and post-weld treatment

(1) Welding material: Use stainless steel welding consumables with lower or equal strength to plate material.

(2) Post- welding heat treatment: Post-weld heat treatment shall be conducted. The post-weld precipitation treatment in the range of 600-650℃ can make the welded joint strength further increase, especially in the clean and stress-relieving annealing, microstructure adjustment annealing, so as to reduce the hot crack tendency of weldment.

3. Attention

(1) High strength steel cracking phenomenon often occurs at fine grain plates when welding with high current. Therefore, small current should be used for welding.

(2) Aggravated galvanic corrosion may occur when dissimilar steel welding.

(3) It is necessary to choose the right gas protection and do a good job of flux cleaning.

Although welding chromium martensitic stainless steel has certain difficulty and requires complete heat treatment after welding, its excellent performance has a good application effect. The above are the welding properties of chromium martensitic stainless steel, it is hoped to help you understand.