How to Weld Stainless Steel

Stainless steel is one of the most common metals found across many industries. Thanks to its corrosion resistance, quality strength and clean aesthetic, it is an ideal metal for projects and mechanical work. However, if you have not worked with this product before, it is recommended to find out all you need to know to get the job done. We explore stainless steel, its applications and how to achieve the perfect weld.

Stainless Steel: Its Properties and Applications

As a metal, stainless steel offers strength and corrosion resistance, making it an excellent material for the manufacturer of cooking utensils, medical equipment and the construction of offshore technology. It can also be used for car manufacturing, shipbuilding and the construction of buildings and roofs.

This metal is also divided into three categories, and depending on which group you are welding, it will determine your welding equipment and methods. In addition, stainless steel can also be a very brittle metal to work with, which results in cracking when put under too much pressure.

The Three Categories of Stainless Steel

Stainless steel is a composition of iron, carbon and chrome, and it is the chrome element which is vital to the grading of stainless steel.

Martensitic stainless steel – This grade of stainless steel has a chromium ratio between 11.5% and 18% and is magnetic. It creates long white sparks with few forks during welding and can offer ideal material for more wear-resistant projects. Some examples are AISI 410, 416, 420, 431, 501, and 502 sheets of steel.

Ferritic stainless steel – Containing between 17-18% chromium, this category of stainless steel is ideal for work requiring a magnetic property from the metal elements. During the welding process, this material produces white or red sparks with few forks, and examples of ferritic stainless steel include AISI 405, 409, 432, 439, 442, and 446.

Austenitic stainless steel – The total nickel and chromium content is 23% of this category of stainless steel. This is one of the more common stainless steel metal grades, and their number usually stars with the number three. They are non-magnetic and do not harden by heat treatment.

Getting the Correct Method of Welding

Choosing a method before carrying out your weld will determine your required equipment. For example, MIG or TIG welding methods can be used for stainless steel, but depending on the thickness of the metal sheets, it could ascertain a preferred process.

MIG welding is perfect for thicker applications and workpieces, whereas TIG offers delicate but strong welds for more nominal thicknesses and details. Of course, if you need to use MIG welding, you will also need to find an adequate filler for each stainless steel grade.

The most common austenitic steels are 304, 308, 309 and 316. For 304 and 308, a 308 filler metal can be used. Popular ferritic grades are 409 and 430, with matching filler metals of 409 and 430. For the most used martensitic stainless steels, 410 and 420, these can be matched with 410 and 420 filler metals with similar characteristics.

The Best Gas for Stainless Steel

At Adams Gas, we understand the importance of having not only suitable gas but the best quality of gas for a perfect finish. Poor quality gas can lead to compromised joins and messy finishes, which is why we check every bottle of welding gas we sell, making us one of the leading bottled gas suppliers in the south of the UK.

MIG Welding Gas – We offer a range of options for MIG welding, all reliant on the thickness of the material being used.

• 2% CO2 and argon mix – Suitable for up to 10mm thickness of stainless steel
• 5% CO2 and argon mix – Ideal for welding up to 6mm thickness of stainless steel
• 12% CO2 and argon mix – Perfect thicknesses between 4mm – 10mm of stainless steel
• 20% CO2 and argon mix – Used ideally for thicknesses of between 6mm – 14mm of stainless steel.

TIG Welding Gas – We can also supply high-quality shielding gases for various applications if you require TIG welding for your project. When welding stainless steel using this method, it is recommended that pure argon is used for shielding your join as you carry out the weld. Argon helps protect the weld pool from environmental impurities such as oxygen and maintains a strong welding arc. Although helium is another alternative, by choosing argon, you help keep the project’s cost down, especially with our cost-effective rent-free bottled gas options.

We can supply pure argon in various sizes depending on your required needs, from 2L, which is great for mobility, to 50L, used for more industrial applications.

Things to Consider When Welding Stainless Steel

When it comes to welding with stainless steel, it is paramount that you consider your safety equipment. Ideally, we recommend a welding apron, gloves and helmet before carrying out any work with welding. Covering any exposed skin is essential regardless of methods or size, but safety boots are also recommended if you work with larger pieces of metal.

For TIG welding, you must ensure that the metal does not splash when joining stainless steel. Splashing results from too little amperage, and you require more strength and power. Alternatively, too much force can melt more metal than needed and compromise the workpiece.

MIG welding is a little trickier, and more must be considered when welding stainless steel. First, the torch’s protruding wire must be at least half a centimetre. In addition, when holding the torch to create the arc, you must ensure it sits at 30° to the workpieces you are joining. Like in TIG welding, if there is a splash from the metal, you must offer more power to your equipment, and if you find that your metal is melting too quickly, the power must be reduced to produce a smooth liquid cord which is easy to control.

With either method, allowing the piece to cool before moving the metal is essential. Moving it too quickly will adjust the molten metal and can concede to a poor join. In addition, you will also need to ensure that all your equipment has also cooled to prevent injury or harm to either yourself, others or the environment.

Suppose you are ready for your next welding project but are looking for a suitable bottled gas supplier. In that case, you can order our high-quality welding gases online, and we will be sure to take care of all your needs, including speedy delivery.