Stainless steel is a very popular material.
It is actively used in the industries and at home.
To be precise, stainless steel is good for houseware, buildings, and different equipment.
Also, stainless steel is in great demand due to its technical parameters.
Thus, it’s corrosion-resistant, strong, and durable.
Besides, stainless steel shines attractively and is easy to treat.
Choosing the Right Method
In the process of welding, a porous oxide layer appears.
As a result, the chromium in steel weakens the metal, increasing its tendency to corrosion.
Therefore, it is necessary to carefully process the product after welding.
In the beginning, the surfaces should be degreased with a suitable solvent.
For instance, you can use aviation gasoline or acetone.
Then this technique will reduce the porosity of the seam and increase the stability of the arc.
SMAW
As for the shielded metal arc welding, it is used for thin steel which is about 0.05 inches thick.
Commonly, people use this method at home.
As a matter of fact, every welder can afford an MMA inverter.
Because of showing the lowest results, the industrial processes do not rely much on such inverters.
SAW
In contrast, welding stainless steel with submerged arc welding allows you to get a high-quality connection.
In addition, it significantly accelerates and simplifies the work performance.
Finally, this method is best for steels thicker than 0.5 inches.
GMAW
GMAW is the most effective and fast way to weld steel joints, forming a straight seam.
This method is better for thicker parts.
In the same time, it requires high-cost equipment.
FCAW
Automatic welding under a flux layer is the most efficient welding method that allows welding parts from both ordinary structural steels and high-strength, stainless and heat-resistant steels with a thickness of 2-50 mm.
GTAW
For welding by non-consumable electrodes in an inert gas medium (TIG), inverters for argon arc welding apply.
Although welding stainless steel is rather complicated, you can carry it out efficiently even at home.
For a positive result, you must take into account the features of stainless steel and choose the most suitable welding method.
Thoroughly treat the welding spot before and after work, and use high-quality welding equipment and consumables.
Types of Stainless Steel
Duplex Stainless Steel
Due to its qualities, duplex steel is used in the marine environment and in saltwater, which makes it optimal for the oil and gas industry.
Duplex stainless steel has a two-phase microstructure consisting of ferritic and austenitic grains.
It has a higher resistance to stress corrosion cracking compared to austenitic stainless steels and better impact strength compared to ferritic stainless steels.
Duplex steel is prone to have large microstructural transformation during heat treatment, also including corrosion resistance.
Duplex stainless base steels don’t have appropriate filler metal, that’s why they have to include the main elements that give steel strength and corrosion resistance (chromium, nickel, molybdenum).
Austenitic Stainless Steel
Austenitic type of stainless steel is the first of the three main types.
People use this type of steel to manufacture bolts and nuts.
What is more, austenites are quite amenable to heat treatment, including welding.
The metal is heat-resistant, cold-resistant and corrosion-resistant.
Prolonged heating of austenitic stainless steel at or slow cooling at high temperatures causes the formation of a hard and brittle intermetallic phase.
This can lead to a very strong loss of viscosity and cause intergranular corrosion.
Martensitic Stainless Steel
Secondly, there is a martensitic class of stainless steels with the following characteristics:
- Self-hardening ability;
- High water resistance;
- High corrosion resistance.
Martensitic steels, due to their structural features, are the hardest among similar materials.
Moreover, steels with a martensitic structure become very brittle and prone to fracture after hardening.
Therefore, welders find it much harder to work with martensitic steel.
Ferritic Stainless Steel
The third common type is ferritic stainless steel.
It is used in the industries which do not require high corrosion resistance.
For example, it’s good for household and auto parts.
It contains about 18% chromium and has a ferritic metallographic structure, which is characterized by softness and good machinability.
However, when heated at high temperature, metallurgical problems arise.
The main difficulty is the risk of the formation of a brittle weld susceptible to cracking.
In this case, the welding technology involves preheating the metal to a temperature of 200°C.
Precipitation Hardening Stainless Steel
Due to its characteristics, precipitation hardening stainless steel is used in aerospace, shipbuilding or process industries.
Precipitation hardening stainless steels contain aluminum, niobium or tantalum.
They get their features through hardening, strain hardening, hardening by aging and martensitic transformation.
The steel is first heated and quenched with the conversion of austenite to martensite.
A welder should use different heating and cooling methods to harden martensitic, semi austenitic or austenitic precipitation hardening stainless steels.
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