When it comes to metalworking, there is a whole host of different metals that you could choose to work with. Whilst you could just use forged steel, you may wonder whether it’s possible to forge stainless steel.
Due to its ability to resist heat and corrosion, stainless steel is able to be forged. The stainless steel grades which are most suited to forging are 304, 316, and 400. It’s necessary to passivate stainless steel after forging to improve its corrosion resistance so that it functions properly and lasts a long time.
Let’s take a look at the benefits of forging stainless steel and how suitable each grade is for being forged.
Why forge stainless steel?
Stainless steel is actually a good metal to use in many small forging projects and it has a number of benefits over standard steel. Stainless steel is most commonly used in sinks, stovetops, and medical equipment due to it having a smooth surface and being easy to clean and disinfect thoroughly.
It has a high resistance to heat which makes it ideal to use in ovens and in any other environment where it would encounter very high temperatures. This is useful when forging as it allows it to adapt new qualities while under extremes of temperature, making it particularly strong and sturdy and therefore also a good material to use in welding projects.
A particularly good benefit of stainless steel is that it has a very good resistance against corrosion which means that if it is exposed to corrosive materials, such as chemicals, then the metal doesn’t break down or rust easily, unlike some other types of metal.
It is also able to withstand heavy weights due to its high quality and strength which, when combined with its other desirable properties, give it a variety of different uses and makes it a good choice for forging since forging only enhances the qualities that it already possesses.
Forging makes it stronger and less likely to be damaged over time and improves its resistance to corrosion, which means it is less likely to rust and degrade over time and use.
Types of stainless steel
There are many different types of stainless steel and each different type is a different strength. This means that different types might be more suited to a project than others, especially as some types forge better than others. The grades which are most suited to forging are 304, 316, and 400.
304 stainless steel
300 series stainless steel types are known as chromium alloys and are a type of austenitic steel. There are slight differences between the types, and 304 is one of the most popular types of stainless steel. It has a wide range of uses as it has a high resistance to corrosion and a high heat strength.
The 300 series are much stronger than the non-300 series types. Therefore, as the 304 type has such a high strength it takes a lot more power and blows with the hammer to forge it than some of the other types of stainless steel do.
When forging 304-type stainless steel it is important to cool it quickly in water as if it cools slowly then it loses some of its resistance to corrosion.
When used in welding projects, the 304 type is very tough and strong and has good resistance to corrosion which makes it a good type to use.
316 stainless steel
316 is a similar type of stainless steel to 304 and is also an austenitic type that is often used for forging. It is similar to the 304 in that it also takes a lot of hammer strength to forge.
Molybdenum is an alloy that is often used in forging and it is usually added to the 316 type to increase its resistance to corrosion. This makes it a useful type of stainless steel to use in food and medical equipment as there will be no corrosion or rusting to contaminate anything.
400 series stainless steel
The 400 series is a much easier type to forge as it requires much less effort. The 400 series is also known as ferritic steel. Ferritic steel is much easier to shape than the 300 series. It is also magnetic, unlike austenitic steel. It is not as strong or as resistant to corrosion as the 300 series, nor is it heat treatable.
The 400 series is often used in engineering projects and in the manufacturing of agricultural machinery and heavy tools.
400 series stainless steel is able to be welded and the 405 type is most commonly used for welding. However, the 400 series is not as good for welding as the 300 series, which is often better to use for many projects.
How to passivate steel
Stainless steel needs to be passivated after it is forged to increase its resistance against corrosion. Passivation is a process that creates a very thin protective layer over the steel which protects its surface from anything which could contaminate it and cause it to rust.
When clean steel is exposed to oxygen, it is automatically passivated; however, forged steel accumulates dust and dirt particles which cause corrosion and rust when exposed to oxygen. Therefore, forged steel needs to be passivated to prevent it.
To passivate stainless steel you must have a clean workplace so that any dust and dirt there does not react with the acid which is used in the passivation process. Once your workplace is clean you need to cover it in an acid bath.
Citric acid, nitric acid, and nitric acid with sodium dichromate are the most frequently used acids in the process, although which one you use might depend on which type of steel you are using.
As you can now see, stainless steel can be forged and is a good metal to use for many forging projects around the home or business as it has many good qualities such as a high strength and weight-bearing capacity, a good resistance against corrosion and rusting, and it is heat resistant. Due to its excellent properties, stainless steel is widely used across the food and medical industries.
When working with stainless steel, it is important to remember to check which series and type of steel is the most appropriate for the purpose you are going to be using it for, and always remember to passivate it to prevent rusting or corrosion.