The world loves stainless steel. According to figures released by the International Stainless-Steel Forum (ISSF), more than 50 million metric tons of stainless steel was produced in 2018.
China was the biggest producer of stainless steel during the previous year, followed by Europe and the United States. The U.S produced 2.8 million metric tons of stainless steel in 2018. However, this equaled only 2% of the global stainless-steel production.
While the U.S lags far behind the likes of China and Europe in terms of the volume of stainless steel produced in a year, the country greatly values the production of quality stainless steel. This is because there is a massive demand for it from several different application areas including consumer goods, building and construction, heavy industries, and more.
The Different Grades of Stainless Steel
There are different grades of stainless steel and specific grades are used in specific industries for certain qualities. For example, the construction industry prefers grades 303, 304, and 316 because of their superior corrosion resistance. On the other hand, consumer goods manufacturers are more likely to use stainless steel of grades 410 and 416 due to their high tensile strength. Here is a complete reference guide on the different grades of stainless steel and what they are best for.
Now, there are five different ways to weld stainless steel. The best method for welding stainless steel may depend on the grade and type of stainless steel you want to produce. However, this is not a rule of thumb. Still, you’d do well to consider the different grades and types of stainless steel when choosing a method to weld the material. We’ve already provided a reference guide on the different grades of stainless steel. Now, we will discuss the different types of stainless before moving onto the five methods for welding stainless steel.
The Different Types of Stainless Steel
There are five different types of stainless steel with varying qualities. However, all five types are categorized based on their microstructure; this is basically their composition and how they are heated and worked. The microstructure of stainless steel greatly influences its strength, flexibility, and other chemical and physical properties.
Austenitic stainless steel, ferritic stainless steel, and hard martensitic stainless steel are the three most common types of stainless steel. However, the other two types: duplex stainless steel and precipitation-hardening stainless steel, also have wide application. Following is a brief discussion on each of the five different types of stainless steel.
Austenitic Stainless Steel
Common applications of this type of stainless steel are fabrication and machining. When it comes to characteristics, this stainless-steel type does not need any preheating and it has the following properties:
- Great strength and endurances across a wide range of temperatures
- High oxidation resistance
- High resistance to corrosion
This stainless-steel type has a maximum interpass temperature of 800°F; this makes it prone to rupture due to low melting materials. In areas affected by heat, the weld of the stainless steel may become sensitive and develop corrosion.
Martensitic Stainless Steel
This stainless-steel type has high-wear applications, such as water-resistant materials, hardfacing, and reinstating rolls of steel in continuous casting mills. Preheating is required by this stainless-steel type; it also needs slow cooling after being weld. As it is heated, martensitic stainless-steel gains strength. This stainless-steel type has a maximum interpass temperature between 400 and 600°F. While it is cooling down, the martensitic stainless-steel can get hard and fragile.
Ferritic Stainless Steel
This stainless-steel type is used in consumer products; an example of this is automotive parts. Typically, this stainless-steel type is welded in a single pass and its thickness in less 0.25 inches. Ferritic stainless steel requires preheating only when there are high levels of carbon. This stainless-steel type has a maximum interpass temperature of 300 °F. If the temperature exceeds this, then this cause loss of strength and grain growth in the ferritic stainless steel.
Duplex Stainless Steel
Common applications of this stainless-steel type are the process and aerospace industries. Ferrite and austenite microstructures are combined to form duplex stainless steel; this ensures greater strength and corrosion-resistance than either ferrite or austenite stainless steel. In order to maintain the balance of austenite and ferrite, a low interpass temperature, and high heat input should be used to weld the duplex stainless steel.
Precipitation Hardening Stainless Steel
Like duplex stainless steel, this stainless-steel type is used in high-performance applications, such as the process and aerospace industries. Elements like niobium are able to increase material strength and drive cost-effectiveness with precipitation hardening stainless steel. The properties of austenitic and martensitic stainless steels are combined to form the precipitation hardening stainless steel. This stainless- steel type is hardened using different methods for heating and cooling the material.
These are the five different types of stainless steel produced today. Each type varies in terms of applications, characteristics, and a maximum interpass temperature. Now that you about the different types of stainless steel, let’s discuss the different methods used to weld stainless steel.
The Different Methods to Weld Stainless Steel
Many people today are interested in knowing how to weld stainless steel; some of these people have some use of the material while others simply want to increase their knowledge about stainless-steel. Regardless of which category you fall into, you will find the information on how to weld stainless steel provided here extremely useful.
As mentioned earlier, there are five different methods for welding stainless steel. Regardless of which method you choose, the stainless steel you weld should be spotless. Some things that you can do to ensure this is using tools and brushes meant specifically for stainless steel and not previously used on galvanized steel; this will allow you to avoid zinc contamination.
Another thing that you can do to ensure the quality of the stainless-steel weld is removing any moisture and contaminants such as soap, adhesive, grease, paints, or oil from the material. However, the most important thing is that you pick the right method for welding stainless based on your application and the type and grade of stainless steel you want. Following are the five different types of methods for welding stainless steel.
Shielded Metal Arc Welding
A popular choice for repair and maintenance work, shielded metal arc welding (SMAW) involves the use of simple and portable equipment; joints ranging in thickness from 0.05 to several inches thick can be weld using this method.
Also known as stick welding, shielded metal arc welding is infamous for producing considerable splash and being less productive than other methods; the time and cost associated with the cleanup following the use of this method can be significant. On the flip side, the welding method is a good way to start for fabricators who have no prior experience of welding stainless steel.
The method does not involve any shielding gas. Therefore, a stainless-steel electrode and a power source relevant for the SMAW method is all that is needed to weld stainless steel with this method. The cost of the electrodes used in SMAW is in the mid-range; it is less slightly more than solid wires but less than metal-cored and flux-cored arc welding wires.
You can buy the electrodes for SMAW in small quantities to manage costs depending on the size of the job. Although it has low deposition rates, SMAW can is generally cost-effective. You can determine if the low costs of the method’s electrodes make it cost-effective by considering the slag removal and stub loss of the shielded metal arc welding process.
A good choice of electrode for this method would be a 309 or 312 SMAW electrode; there are especially useful in repair and maintenance applications. These SMAW methods stainless steel with increased strength and cracking resistance. Additionally, it can join stainless steel that is already in use.
Submerged Arc Welding
Generally, this method for welding stainless steel is used to weld parts with a thickness greater than 0.5 inches. Submerged arc welding (SAW) is the stainless-steel method preferred by most fabricators to weld carbon steel. There are many benefits of using this method including increased productivity and extremely low levels of spattering; this helps save both time and money.
This method for welding stainless steel can apply to most austenitic stainless steels; however, heat can cause the austenitic stainless steel to crack if it is welded with the SAW method, but no ferrite is present in the weld metal. Materials with increased thickness and large applications such as liquid or storage gas tanks are ideal places for use of the SAW method.
One of the best things about this method is that it can be performed by less-skilled operators. However, it is important to pick the right flux. To prevent adding alloy that can potentially alter the completed weld’s chemistry, you should use a neutral or non-alloying flux. Additionally, you should keep track of the welding conditions; doing this will allow you to control ferrite content and deposit composition.
Gas Metal Arc Welding
Ideal for a large number of welds or for long joints in thick materials, the gas metal arc welding (GMAW) method can join two pieces of stainless steel strongly when performed correctly. A welding method that involves a solid wire electrode and an argon rich shielding gas, GMAW has fast deposition rates and does not require you to remove slag between passes.
The equipment used in GMAW makes it a pricey welding method. However, the good-bead appearance and efficiency offered by this method make the price worth it. Today, the gas metal arc welding method is increasingly popular amongst fabricators; a major reason for this is that the method allows welders to use a pulsed current supply. How is this useful? it makes it easier to complex stainless steel projects that require welding tough-to-reach spots.
In the GMAW method, gases mixtures are often used to provide stability to the arc and improve the quality of the weld. Today, the GMAW method can be used by the less-skilled fabricators to weld stainless steel thanks to filler metal and the advances in equipment.
The operator skills requirements for GMAW are moderate and the equipment involved in the method isn’t too complicated. There are many fabricators that use only a solid wire when welding with this method; the argon rich shielding gas is an optional and additional expense. However, the use of this shielding gas is recommended as it is known to significantly reduce spatter.
Flux-Cored Arc Welding
Compared to the GMAW method, the flux-cored arc welding (FCAW) method is generally more productive. However, it can produce spatter and slag which can increase the time and money involved in the cleanup.
Another reason why you would want to avoid this method is that manufacturing the alloying elements of its flux can be quite expensive; this is the cost per pound for stainless filler metals is higher with FCAW than any other welding method. Further, a common shielding gas for the wires involved in the method is carbon dioxide; this can add carbon to the weld metal. What is the outcome of this? Reduced corrosion resistance in the stainless steel being weld.
The good news is that there are several wires that can be used in FCAW that required common shielding gas mixtures such as 100 percent CO2 and argon. Typically, you’ll need to invest in various delivery systems or type of gas if you’re new to welding stainless steel.
On the positive side of things, fast travel speeds that do no exert too much heat onto the weld are provided by the metal-cored arc welding method; this is regardless of whether you use the standard or pulsed spray methods. This helps prevent distortion and warping when stainless steel is being welded.
Compared to other methods, less spatter is produced by flux-cored welding; however, the filler metal’s price per pound should concern you. Ideally, you should compare the upfront costs versus the potential reduction in cleanup and rework as well as the gains in productivity before you choose to use the FCAW method and the filler metal associated with it.
Gas Tungsten Arc Welding
Generally used for welding stainless steel with a thickness of up to 0.25 inch, the gas tungsten arc welding (GTAW) method joins together traditional and PH stainless steels.
A welding method that produces minimal spatter, GTAW can ensure a good welding job if you choose the right filler material and monitor the temperature of the steel being weld. Additionally, the method will have a moderate cost per pound if you use filler rod or wire. However, the method generally involves complex equipment and requires a high level of fabrication skill.
One of the most commonly used methods for welding stainless steel, the gas tungsten arc welding method ensures a versatile, durable, and high-quality stainless steel. GTAW is a great welding method for stainless steel if bead appearance and aesthetics are most important to you. However, it is not the best choice in terms of productivity.
Typically, 100 percent argon shielding gas is used on stainless steel by the GTAW method. Often, a secondary argon tank is kept in reserve for a back-purge between passes. Since it creates a low heat input, the GTAW method is ideal for thin material. Additionally, the welding method produces a precise and clean weld; these aesthetic reasons are why some fabricators prefer GTAW over other methods for welding stainless steel.
Depending on the specific project’s needs, the argon gas used in GTAW is often mixed with other gases such as nitrogen, hydrogen, and helium. Also, a one-sided welding process is often used to provide the interior and exterior welds with inert backing gas protection to prevent oxidation and increase corrosion resistance.
There you have it—the five different methods for welding stainless steel. Now that you know the different types and grades of stainless steel as well as the methods to weld them, you can get down to work and start welding stainless steel.
Which Welding Method is the Best?
So, you know how to weld stainless steel but how do you pick a method for welding? What is the best choice for welding stainless steel? Well, this will depend on the qualities you’re looking for. For instance, if you’re looking to keep costs low, then submerged arc welding (SAW) can be a good option. On the other hand, if you’re working on a thin material, then gas tungsten arc welding (GTAW) would be a good choice.
For increased productivity, you can go with the flux-cored arc welding (FCAW) method. Good bead appearance and efficiency offered by gas metal arc welding (GMAW) are two reasons to choose this method. Lastly, shielded metal arc welding (SMAW) is ideal for people with no prior experience of welding stainless steel or those who need to perform repair or maintenance work on stainless steel.