According to the international stainless-steel Foundation (ISSF), stainless steel productions reached 47.7 million tons in 2020. This considerable value of steel is used in everything around you, and building everything require welding in one way or other. Welding of stainless steel is not as straightforward as other materials. In this article, we will discuss everything about the welding job of stainless steel.
Stainless steel is the most commonly used material in the construction and manufacturing industries. It is used almost everywhere, from the manufacturing of automobiles to the construction of large buildings. The most crucial benefit of using stainless steel in your structures is its strength. When hardened, stainless steel can bear up to 1500MPa of stress on its surface. This factor depicts the reason for so much stainless-steel usage.
So, Lets Start because this guide is going to be very extensive and you will not find it at any place else. My Welding Yard is dedicated to provide you the top notch welding knowledge so you can excel in this field.
List of Contents
- What is Stainless Steel?
- Different Grades of Stainless Steel
- What are the different types of stainless steel?
- Welding Stainless Steel
- The Best method for welding Stainless steel
- Welding Stainless Steel with other metals
- Frequently Asked Question FAQs
What is Stainless Steel?
Steel is an alloy of carbon mixed with a percentage of carbon to improve strength and fracture resistance. Different grades of steel are classified due to the variable ratio of carbon in them. When Low carbon steel is mixed with a minimum of 10.5% chromium, it produces stainless steel. A layer is chromium oxide is added to the surface that resists any corrosion or rusting of material. The amount of chromium can differ as per applications.
Stainless steel is very durable with very high tensile strength. It is also temperature resistant so that you can use it in applications dealing with high temperatures. Moreover, stainless steel requires low maintenance and has an attractive appearance. Finally, stainless steel is also eco-friendly. It can be recycled and used in other applications. All of these appealing factors make stainless steel one of the most frequently used manufacturing materials.
Different Grades of Stainless Steel
Sometimes along with chromium, a percentage of nickel is also used in stainless steel. This gives endurance to the material and increases its strength. Based on the rate of chromium and nickel used, stainless steel is divided into different grades. According to ISSF, almost 150 different grades of stainless steel are currently being used in industries. A three-digit number showing chromium and nickel content in steel distinguishes one quality of steel from another.
The most commonly used grades of stainless steel used are 304 and 316. They are preferred in construction industries because of their superior corrosion resistance. Stainless 316 have 16 percent chromium, 10% nickel, and also have 2% of molybdenum.
Using molybdenum gives grade 316 an increased reluctance from chloride and chlorine solutions, making it better for marine environments and pharmaceutical industries. The stainless steel grade commonly used in consumer goods is 416 because of its high tensile strength. The machinability of grade 416 is almost 85% more than other steel grades that accounts for its excessive use in industry.
What are the different types of stainless steel?
Based on the composition of different materials and formation methods, stainless steel is divided into four main types. Another type of stainless steel has additional strength, flexibility, and properties. Molecular geometry also plays an essential role in the division of steel into different kinds. Each type of stainless steel has its molecular structure. Following is a detailed note on all four types of stainless steel.
1.Ferritic stainless steel
The type of steel that contains about 10.5% to 30% of chromium is called ferritic steel. Common grades of ferritic steel are 409, 430, 439, and 444. This type of stainless steel is commonly used in consumer products and automobile parts manufacturing.
Ferritic steels can be welded in a single pass and usually in thickness ranging from 0.20 to 0.50 inches. However, ferritic steel grades with more carbon contents require pre-heating for their welding. These steels have a low inter-pass temperature, which is about 300 degrees Fahrenheit.
Inter-pass temperature is the maximum temperature material can endure without a change in molecular structure and subsequent loss of strength.
In austenitic steel, chromium content ranges from 16% to 30%, and along with chromium, they also have nickel from 2% to 20%. The 200 and 300 series of stainless-steel compromise of austenitic type. This is the most common type of steel used that is used in machining and fabrication.
Austenitic steel has high strength and endurance. The inter-pass temperature reaches the value of 800 degrees Fahrenheit. This steel category can use several welders for complete weld and can be worked with welders having high power outputs.
Martensitic steel contains chromium ranging from 11% to 17%. This is a type of steel that is tempered and hardened using multiple ways of heat treatment. Due to hardening, martensitic steels have high strengths and durability. They are commonly used in manufacturing medical instruments, mechanical valves and instruments, turbine parts, and much other product’s manufacturing.
4.Duplex Stainless steel
Duplex steel has a metallurgical structure, a combination of a crystalline form of austenitic and ferritic steel. This type of steel has about 20% of chromium along with 5 to 10% of nickel. Duplex steel has increased strengths and durability. The most used grade is stainless steel in 2205. Duplex steel can be used with temperatures of up to 1100 degrees Fahrenheit. They have high machinability and can be welded using standard welding processes.
Welding Stainless Steel
You can use different methods to weld a stainless-steel workpiece. Each method has its benefit and losses. Some people think Gas Tungsten Arc Welding (GTAW) is the best method for welding stainless steel as it can help give specific jobs. However, modern inverter technology has made Gas Metal Arc Welding (GMAW) very stable and precise. As stainless steel is most widely used, different welding techniques are used in its working. We will discuss all these in detail here.
Preparing the Welding Specimen
Cleaning the working area is the main factor that can also change the quality of your weld. You have to clean moisture entirely from the layer. If any paint or adhesive material is used on the material layer, you need to clear it before welding. Spots on stainless steel should be avoided during your job.
Stainless steel can be sensitive to the presence of carbon steel, so you should keep your brushes, hammers, and clamps away from stainless steel projects.
The availability of filler metal is also a primary factor during welding stainless steel. You have to choose a filler metal which is of the type of base metal. Sometimes, when welding different materials, it is not as straightforward to select a filler metal out of many options. But you need to pay special attention while choosing one filler metal.
After thoroughly preparing the weld, we are ready to weld the workpiece. Following are the main welding types that can be used to weld stainless steel.
Stainless Steel Welding with MIG
This is a powerful process that can be used to weld high carbon steel and thick steel plates. It also uses a shielding gas to protect the weld against contaminants so that you can use this process for on-field welding of steel. GMAW doesn’t create slag and gives the finest welds over your workpiece. This is one of the best methods to be used for steel welding.
The equipment used in MIG welding is expensive and requires some welding background for you to operate the device. Professionals use this method of welding a lot to weld steel because it grants users to design their welds completely and set amperage, pulse rate, and Pre-flow or Post-flow controls. Austenitic steel is the best to be welded with MIG techniques. However, when you fuse stainless steel with a different metal, you must use a proper filler metal.
GMAW provides fast welds along with great deposition rates. You don’t need to do any post welding cleaning as this method does not create any slag. Welds done by MIG welding are strong enough to be used in applications. If you are curious which mig welder is great you can check reviews about them.
Stainless Steel Welding with TIG
GTAW is used where you have to weld thin plates of steel. TIG technique is suitable to be used with lower thickness metals of up to .5inches. TIG welding produces the minimum spatter and provides the most precise welds to the stainless steel.
GTAW is not an easy welding method and requires an expert to operate thoroughly. You will have to use a filler rod according to the type of steel you are using that will cost you the length of your weld. You can set the wire flow rate, pulse arcs, and almost everything of your steel welds through the machine.
This method is ubiquitous among fabricators to weld stainless steel as it produces precise and durable welds. TIG machine is expensive, and consumables are also pricey, so it is not a very productive method to choose from in your job. TIG welding is best to be used where precision is required.
Most of the time, argon is used as a shielding gas in welding stainless steel; however, sometimes argon is being mixed with other gases like hydrogen or helium. GTAW is an excellent way to weld stainless steel, but it requires some skills to operate and a skillful welder to use the machine.
Stainless Steel Welding with Stick
SMAW is one of the standard techniques used to weld carbon steels and different alloys. In this arc welding process, we use a consumable and protected electrode according to your working metal. Electrode melts during the process and provides a cover for the protection of welds against dust and atmospheric gases. Users can use this method to weld stainless steel joints up to several inches thick.
STICK welding creates a lot of splashes and doesn’t precisely weld. This is the most straightforward technique to weld as it doesn’t require any configurations to set from the machine. Beginners usually rely on this method of steel welding for their jobs.
You will need a stainless steel electrode to weld from this technique. This type of electrode can be a little expensive. Also, SMAW doesn’t involve a shielding gas, so Welders cannot use it for outdoor welding. However, the welds given by the SMAW technique are stable and don’t break easily. Thus, arc welding is a useful technique that beginners can use to provide strong welds to stainless steel. Professionals should avoid this technique as it doesn’t offer fair and reasonable appearance welds. you can check these stick welders for your tasks.
Stainless Steel Welding via Fluxed Core
This is a semi-automatic process that can weld mild steel. However, this technique produces spatter and cannot give precise welds over stainless steel. Fumes are also produced in great deed using this method, which is bad for health. However, many welders still use it because of its increased productivity of welding steel over other metals.
The alloying metal used in FCAW can sometimes be expensive, so it’s better to avoid this method in your job. To weld steel, CO2 and Argon are commonly used as shielding gases in this method, but they can also contaminate your weld. FCAW is best to be used in beginner applications as it is relatively more straightforward than other techniques. But as an expert, you should avoid this method as it uses costly equipment and doesn’t give satisfactory welds over stainless steel.
Stainless Steel with Submerged Arc Welding
This technique can be used to weld steel workpieces of thickness more than 0.5 inches. A powdered flux metal is used to shield the weld, and it is best to be used in outdoor applications. This method doesn’t spatter and is very productive in the usual routine of the job.
As this method creates more heat, it is not acceptable to use it with mild steel or thin workpieces. It can be used on most of the austenitic steels. This technique is straightforward and can be performed by beginners easily. However, you should pay special heed while selecting the alloy metal that should be neutral. If you choose an alloy from unwanted composition, it can change the base metal’s composition.
SAW welds are more robust, and you can use them with steels of heavy loading. You can do the welding job, both indoor and outdoor using this technique. Welds given by SAW penetrate deep into the workpiece, and you require minimal edge preparation of stainless steel. Altogether, this is a perfect method for stainless steel welding by both beginners and professional fabricators.
The Best method for welding Stainless steel
You can use most of the welding methods available for the welding of stainless-steel objects. But the best suitable way for you depends on your requirements. You have to choose the best for your job by keeping in mind the following things.
Welder’s Skill Level
The most important thing to consider is your skills and the type of machine you can use easily. Suppose you are a beginner, then MIG and TIG machines can be complicated for you to operate. As a beginner, you can go with SAW or STICK welding as per your preferences. But if you are professional and can easily configure your arc, then MIG welding would be best for your job. TIG welding is also an option for skilled fabricators.
The Aesthetics of Final Piece
Sometimes the only concern is joining the stainless steel firmly without worries about appearance. FACW can be used in these types of jobs as it has more productivity than other methods. But sometimes, welders need to be concerned about bead appearance and the precision of the welding job.
It is better to choose a technique that gives acceptable welding outcomes like TIG welding or SAW in these jobs. TIG welding can be complicated for beginners, but it provides the most satisfactory welding outcomes.
The Thickness of your Specimen
Thickness matters a lot when doing welding work. GTAW can only weld up to ½” inch thickness. If your workpiece is thicker, you should go with some other type of welding. SAW can be used with a workpiece of consistency more than 0.5 inches. TIG welding is usually suitable for working with thin metals as it creates moderate heat that is good for working with most mild steel projects.
Difficulties Faced during Steel Welding
The microstructure of steel creates hurdles during the job of welding. It would help if you were careful about the temperature you are using and how you are using it. One of the crucial factors to be cautious in this regard is sensitization in the steel, altering the steel’s corrosion resistance characteristics. Following are some main points that can you need to keep in mind when going for stainless steel welding.
Chromium Oxide Layer
Steel is mixed with littler to moderate concentration of chromium oxide to save it against rust. The composition of chromium oxide in a steel block can be more than 20%. This creates a layer of chromium over the surface of steel that makes it difficult to weld. The thicker the coating, the slower is puddle formation.
Some welders try to increase the heat input to form puddles swiftly, but doing so results in damaging of steel’s surface. It would be best to give as much information as required for proper puddle formation and be concerned about steel structure.
One other factor that makes steel welding difficult is fumes due to this chromium oxide layer. Hexavalent chromium is produced by heating the chromium, which is challenging to respirate in such an environment. According to OSHA, these fumes are also damaging to the skin, eyes, and kidneys. While stainless steel welding, you should wear proper protective equipment, including a respirator, and take appropriate care while dealing with steel welding.
Co-efficient of Thermal Expansion
Steels expand when the temperature is applied to its ends. This is called thermal expansion. Austenitic steel has a significant rate of expansion as compared to mild steel. It would help if you used heat to your weld below this co-efficient of thermal temperature, or otherwise, steel can expand and crack.
Stainless steel has a low melting point than standard steel. This makes it melt at lower temperatures as compared to ordinary metals. However, this factor has the advantage of created more fusion for the same heat. But when you convert from mild steel to austenitic steel, you need to be careful about this factor.
Welding Stainless Steel with other metals
Most of the time, stainless steel is used to apply with some other metals like copper or aluminum. In these cases, you have to weld using a filler metal. We will discuss how you can weld stainless steel with some other metals it is probably used with.
Stainless Steel and Copper Welding
Most of the time, steel is used along with copper in an application. But it’s not that easy, and the strength of the welded material is not the best. Copper is used along with stainless steel in electrical applications. TIG welding is one best option to weld stainless steel to copper, but you need to be extremely careful and perform it precisely.
A silicone bronze rod is used as filler metal between copper and stainless steel in a TIG process. Other than welding, most of the time between copper and steel soldering or brazing is used depending on as per applications.
Stainless Steel and Aluminum Welding
Aluminum and steel are very different for metallurgy and their relative properties. So, it is challenging to join these metals together for an application. Modern processes like fusion welding and laser welding are used to join steel with aluminum in industries.
Special intermediate filler metals can also be used to give manual welds between steel and copper. Aluminum 4043 is one of the most popular filler metals used between aluminum and steel. Welders can also do aluminizing steel (Dipping it in an aluminum solution) before welding to attach steel with aluminum firmly. Applications are probably joining decks of ships, connecting tube sheets, and pipelines together.
Welding Stainless Steel to Carbon Steel
Austenitic steel is welded with carbon steel using TIG and MIG techniques. You will need to use filler metal in welding stainless steel to carbon metal. You will need to perform the welding job correctly and with care as due to the difference in metallic structure, carbon steel and stainless steel don’t have many adhesive forces.
Welding Stainless Steel to Galvanized Steel
Galvanized steel is a type of steel coated with zinc; thus, you will need to remove this layer of zinc to perform any welding job. Otherwise, zinc can contaminate the weld. After removing this layer, you can use MIG or TIG welding as per metal thickness to give welds over the workpiece.
Welding Stainless Steel to Inconel
Classical techniques of TIG welding can be used to weld Stainless Steel to Inconel. Inconel 625 is the best filler metal for this job. MIG welding is also a good option for welding stainless steel and Inconel together, but the TIG method is preferable.
Frequently Asked Question FAQs
Do stainless steel welds rust?
Stainless steel has a layer of chromium oxide that prevents it from rust. But you need to keep the surface clean for longer life. Exposure to humidity and salinity can remove the protective layer and cause rust to the stainless steel. So, you need to keep the steel away from humid environment for long durations in order to keep it free from rust.
Can I weld stainless steel with a wire feed welder?
Wire feed welder can be used to weld stainless steel but you need to use a shielding gas. Surface of steel should be cleared of any paint or humidity before applying weld. The wire selected should be compatible with stainless steel.
Can stainless steel be welded to stainless steel?
Yes, you can weld stainless steel to stainless steel using MIG welding or TIG process. However, if the welded steels are different in carbon content than you need to use a filler metal. Stainless steel creates strong welds with other stainless steel and used in many applications for strength of their bond.
What are the hazards of welding stainless steel?
Stainless steel is coated with a layer of chromium oxide which when heated create fumes. These fumes are bad for skin, eyes and respirations. Welders must take proper care while welding stainless steels and use mask to protect his lungs.
Can you weld aluminum to steel?
Aluminum can be easily welded with stainless steel using common TIG or MIG techniques. You need to use a filler metal for this purpose. Aluminum 4043 is used as filler metal most of the time. One other way of welding stainless steel to aluminum is by brazing steel in the solution of aluminum.
In this article, I have discussed everything you need to know about welding stainless steel. I have also discussed some common causes of failure and how to give a good welding job over stainless steel. After discussing briefly all the welding methods used for steel welding, I also pointed out how you can choose your welding method. As a whole, this article is everything you need to know about steel welding, and after reading, you can start giving artistic welds over steel.