Some of the properties of stainless steel are that it is corrosion-resistant, durable, and has a mesmerizing appearance. However, metal is affected by factors such as oxygen, carbon, and many others. Conversely, the four different varieties of stainless steel are Austenitic, duplex, ferritic, and martensitic stainless steel. Different features can be found in each variety of stainless steel.
On the other hand, some methods used to weld stainless steel are gas metal arc welding (GMAW) and tungsten inert gas welding (TIG). One should keep a few important points in mind to obtain a satisfying output, such as rust prevention and deposition rate.
What are the Characteristics of Stainless Steel?
Stainless steel is popular for its mechanical properties, and its characteristics make it a significant alloy to use in different industries. There are a few properties given below; let's take a look at them:
Strength
The most important property of stainless steel is its strength. The metal may be remarkably robust even at very high or low temperatures. Besides, the property makes it in demand in the aviation industry.
Corrosion Resistance
Stainless steel can withstand rust and water stains because it has strong corrosion resistance.
Chromium oxide is the cause of excellent corrosion resistance. The chromium oxide coating forms as a result of the metal's surface being exposed to oxygen. Hence, this characteristic plays a huge role in stainless steel's protection.
Cleanliness
Stainless steel does not aid bacteria in growing on it; hence, one does not require an abundance of effort to clean it. As it is a clean material, stainless steel is utilized by catering and medical companies. One can use a swab to clean the metal, making it helpful in the kitchen.
Fascinating Appearance
Stainless steel is known for its strength, but it also possesses other important properties. It is often used in architecture since it looks amazing.
Furthermore, it provides classic and contemporary interiors with a clean, modern appearance without giving up utility.
Recycling
Recycling stainless steel to produce new materials is a great choice. This requires fewer raw resources and produces less waste, which lessens the environmental impact of producing the steel we require.
Various Forms of Stainless Steel
There are four types of stainless steel, and it solely depends on the ambiance that it can resist. Let's take a look at the five different kinds of stainless steel.
Austenitic Stainless Steel
Austenitic stainless steel has elevated concentrations of chromium, molybdenum, and nickel compared to other stainless steel forms. This form of stainless steel is known for its versatility and malleability. Besides, austenitic stainless steel shows amazing strength. Conversely, austenitic steel makes up about 70% of the total.
Ferritic Stainless Steel
Ferritic stainless steel has less carbon stability, which will not exceed 0.1%. However, the chromium content of stainless steel ranges between 10.5% and 30%. It is magnetic, and individuals choose this kind of stainless steel because it can withstand temperature oxidation. Besides, ferritic stainless steel is also recognized for withstanding stress corrosion, although ferritic stainless steel has poor fabrication.
Duplex Stainless Steel
This kind of stainless steel is formed by mixing ferritic and austenitic stainless steel. Duplex stainless steel is stronger than the other two kinds of stainless steel since it has the traits of both. Some of the features of a duplex are its tensile strength and great weldability. Besides, duplex stainless steel is used in marine applications because of its corrosion resistance.
Martensitic Stainless Steel
Martensitic has a higher proportion of carbon, about 1.2%, and a lower percentage of chromium content. Moreover, this form of stainless steel is magnetic, although its weldability is disappointing as compared to other kinds of stainless steel. However, its ability to harden is greater. Martensitic stainless steels are used for making medical tools.
Methods Used to Weld Stainless Steel
There are three types of methods used to weld stainless steel, and they are
Tungsten Inert Gas (TIG)
Gas tungsten arc welding is the common name for tungsten inert gas. The non-consumable tungsten electrode provides the current for the welding arc. Argon gas is mostly used to cool and protect. It produces significantly less smoke than various gasses and inhibits oxygen.
Conversely, TIG welding is popular for welding stainless steel, which is thin. Additionally, conventional and PH stainless steels are joined using the GTAW method, especially with thicknesses up to around 0.25 inches. The advantages of using TIG welding are pore-free and strong welds. Furthermore, it makes pleasing and clean welds.
Metal-Inert Gas Welding
It is also called gas metal arc welding. With the help of electricity, it melts and fuses metal components. It is popularly referred to as a "hot glue gun" in the field of welding.
The developers of GMAW started in the 1940s, and it primarily focused on welding non-ferrous metals. A wire should be attached to a direct current source and used like an electrode when it constantly travels via a welding gun to link two pieces of metal together with MIG welding. Helium has the highest proportion at 90%, followed by argon at 7.5% and carbon dioxide at 2.5%; these three gasses make up the shielding gas mixture for GMAW welding stainless steel.
The main benefit of GMAW welding is that using this method, one can weld stainless steel faster than traditional methods. Furthermore, GMAW welding makes long, continuous welds quicker than expected.
Resistance Welding
Resistance welding is commonly used for spot and seam welding. Resistance heat and a nugget are formed while an electric current is passed through electrodes making contact with the metal. Metal joints are the eventual result. However, it requires a significant quantity of current from the power source. Thus, it uses low voltage to work.
This form of welding can be significantly more efficient since it merely involves pressing a button to activate the process in manufacturing. Besides, the area being worked on is less affected because the heating duration and heat concentration are lower. The best advantage is that welders do not go through hectic pre-welding coaching.
Environmental Effects of Welding
Carbon and oxygen have a strong chemical attraction for chromium. The repercussions of chromium mixing with a considerable quantity of oxygen and carbon from an outside source should be taken into account whenever the metal is welded.
Besides, a few more elements influence the welding properties of stainless steel. A few of the impacts are given below:
Oxygen
The chromium oxide film that develops on the surface is what gives the stainless steel its resistance to tarnishing, oxidation, and corrosion. Despite the beneficial function it serves, the majority of welding and soldering procedures are hampered by this permanent oxide-forming property. However, the refractory slag coating on stainless steel provides some amount of shielding against further oxidation.
Carbon
For example, the metal's affinity for carbon may result in discouraging repercussions in the completed weld joints due to carburization.
Nitrogen
It has not been as problematic as oxidation to nitrify the surfaces that are exposed to heat. The constant precautions required to protect stainless steel from oxygen in the air also help keep nitrogen out. Fusion-line porosity has sometimes caused problems with welding types 321 and 347, although they typically have changes in composition to address this.
Copper or Lead
Free copper or lead present on the base metal's surface may cause the completed weldment to become embrittled and break. There should be no pollutants of any kind present in the joint region, which includes the HAZ.
How do I Obtain the Desired Result?
One should be aware of the points that are given below, which will assist you in welding successfully.
Deposition rate
Different welding methods have different deposition rates. The utilization of a flux-cored welder and a dual-shielded wire will help to provide you with deposition rates.
Rust Prevention
Stainless steel is bound to rust, but you can prevent this by keeping some points in mind.
Firstly, ensure to spread a thick layer of shielding gas. Secondly, after welding, make sure to clean the completed weld thoroughly. It is advisable to use a wire brush, not a steel brush because it might taint the weld. Finally, overheated stainless steel will lose its ability to resist corrosion.
Limit the size of your filler
To reduce the heat, keep your filler to a limited size. When it comes to stainless steel, the amps must be kept low. Therefore, limit the size of your filler so that you can turn down the heat.
Travel rate
Moving slowly is not desirable because it produces an abundance of heat in the metal; thus, you need to speed up your movement. The gradual weld travel will lead to a change in color to gray and increase the chances of porosity problems.
Final Words
The welding of stainless steel has many incredibly great traits that make it one of the most preferable metals in many industries. However, many environmental factors, such as oxygen, affect the metal, which leads to rusting. To avoid rusting, one needs to clean the completed welding. On the other hand, safety must be the priority while welding. And to stay safe, one must use welding PPE and wear clean gloves.
