Due to its exceptional corrosion resistance, attractive appearance, and high strength, stainless steel is used in consumer and industrial markets. In the knifemaking world, stainless steel is commonly used for making various kitchen knives. Blacksmiths also use stainless steel for various other projects like brackets, forks, spoons, hooks, etc.
As you may already know, stainless steel is an iron and chromium alloy. Other common additives include carbon, manganese, nickel, nitrogen, sulfur, copper, molybdenum, and silicon. The ratios of these additives will vary based on the intended use and the grade requested. Note that the steel must have at least 10.5% chromium to be classified as stainless.
In this guide, we will cover:
- Can you forge stainless steel?
- Is stainless steel good for forging?
- Common applications of stainless steel
- Can you forge a knife from stainless steel?
- Does forged stainless steel rust?
- Is it safe to forge stainless steel?
Without any further stalling, let’s dive into the main topic.
Can you forge stainless steel?
The question of whether or not you can forge stainless steel is surprisingly very common, so let’s get it out of the way first. There are two sides where some will tell you that stainless steel is good for forging in most cases. The other side claims you cant forge stainless steel, and you should avoid it as much as possible. In my experience, I learned that the truth is somewhere in the middle.
Stainless steel can be forged, although the process may be harder than for other steels. Since it takes more work, a hammer, power hammer, or hydraulic press is generally recommended for forging stainless steel. Note that some grades of stainless steel will be harder to forge than others.
In my experience, forging stainless steel is often much more demanding in terms of shaping difficulty and the required heat-treating process. Last week when I worked with some 440c stainless steel, it felt a lot like a 5160 under the hammer. However, it took me half an hour longer to forge than it would for some 10x series steel. Unfortunately, my power hammer did not work, so I used a 4-pound hand hammer, making the forging much harder.
I would also say that many types of stainless steel have a narrow working range. For example, 440c steel requires a starting forging temperature between 1900 and 2100°F (bright yellow color). Anything lower than that, and you risk cracking. Note that some stainless steel requires annealing after every forging session. While that could be done in a gas or solid fuel forge, having a regulated treating oven is recommended.
If the stainless steel requires quenching in still air, quench it in still air. I don’t recommend experimenting on your own. I don’t favor quenching any faster than it is recommended. When it comes to tempering, you can use a kitchen oven in most cases. If you are unsure how to heat-treat particular stainless steel, it would be best to send it out to some professional heat treater, especially if you make knives.
Keep in mind that the surface of stainless steel needs clean-up and passivation to remain stainless. Let me explain. The addition of chromium produces a thin layer of oxide on the surface, called “the passive layer,” that protects the surface from corrosion. Without cleaning and passivation, higher chances for the accumulation of iron and dirt particles which can easily cause corrosion and rusting when exposed to air. Therefore, passivation is crucial in ensuring varying grades of stainless steel.
First, clean and degrease your stock to passivate your stainless steel properly, so dirt and iron don’t react with the acid. Otherwise, it would contaminate the whole process. After that, immerse the stainless steel in an acid bath. For this purpose, the most common acids are citric acid, nitric acid, and nitric acid with sodium dichromate passivation.
Is stainless steel good for forging?
Now that we know that stainless steel can be forged, let’s see if it’s a good choice for forging. Again, some people will tell you that it is while others are the exact opposite. In my opinion, both answers are not well thought out. I mean, you can’t just say that some steel is good or bad without knowing the intended use.
That would be asking something like – Is the internet good? It can be good and can also be bad. It depends on what you are planning to do with it. The same thing applies to forging stainless steel.
Stainless steel can be good and bad for forging, depending on the grade and the intended use. Grades like 303, 304, 316, 410,420, and 440c are generally used for forging purposes. However, if you want to forge a knife, 440c is usually recommended.
Note that the forging further increases the durability and strength of stainless steel, making it ideal for use in harsh environments. Another benefit of forged stainless steel is that forging creates a unique grain flow that follows the stainless steel part. Note that forging will also produce a higher strength-to-weight ratio by improving the mechanical properties.
304 stainless steel
304 stainless steel is commonly present in kitchen equipment and industrial applications. It is also one of the most widely used stainless steel. 304 stainless steel offers good corrosion resistance. When making Damascus, 304 is readily welded by the most common methods.
However, 304 is extra-low carbon steel which is not great for knife-making. 304 stainless steel is also difficult to drill and grind and will not take an edge. It also requires a complicated heat-treating process.
Element Percentage
- Fe 64.99-74%
- Cr 17%
- Ni 8%
- Mn 2%
- N 0.10%
- S 0.03%
- C 0.15%
- Si 0.75%
- P 0.045%
Chemical analysis of 304 stainless steel
316 stainless steel
316 stainless steel has better corrosion resistance and strength at elevated temperatures, thanks to molybdenum. That makes the steel convenient for valves, pumps, and marine applications. Unfortunately, not good for knifemaking purposes.
Element Percentage
- Fe 62.045-72%
- Cr 16-18%
- Ni 10-14%
- Mn 2%
- N 0.10%
- S 0.03%
- C 0.03%
- Si 0.75%
- P 0.045%
- Mo 2-3%
Chemical analysis of 316 stainless steel
440c stainless steel
44c is a martensitic alloy that shows good properties with maximum hardness (60 Rc). It is used for making cutlery, valves, valve seats, ball studs, and many other things. However, this steel is typically not good for use at high temperatures. Note that there is a big difference between 440a, 440b, and 440c. The first two are softer grades of 440 steel, and they don’t hold the edge nearly as well as 440c. That is why most factories them for production knives. 440 c is too expensive for this process. 440c is a much better steel for producing knives.
Element Percentage
- Fe 79.15%
- Cr 17%
- Mn 1%
- C 1.1%
- Si 1%
- Mo 0.75%
Chemical analysis of 440c stainless steel
Steel Forging Annealing Hardening Tempering
304 stainless steel 1900-2100°F 1950°F – –
316 stainless steel 1900-2100°F 1950°F – –
440c stainless steel 1900°F – 2100°F 1500°F – 1600°F 1850°F – 1950°F 300°F – 660°F
Heat-treating temperatures of popular stainless steel
Can you forge a knife from stainless steel?
There are many knifemakers out there in the bladesmithing community who say that you should not forge stainless steel. However, I think that statement is not well analyzed. From both my experience and many other bladesmiths I know, I have learned that forging can improve the performance of stainless steel.
Generally speaking, you can forge a knife from stainless steel, but the process may be more complicated. Stainless steel requires much more precise heat treatment than other steel. Some well-known stainless steels for knife forging include 440C, ATS-34, 154CM, S35VN, T440V, VG10, and AUS10.
Note that some stainless steel cannot be hardened, which means that it can’t be used for forging a knife. When we say “forging,” we are typically referred to as shaping a hot piece of metal with a hammer. The blade is usually drawn to a point and tapered. The bevels on the blade and point are forged to their final shape.
Still, most knife makers use the stock removal processes where the material is shaped into a blade without the use of heat or a hammer. However, people always had a greater appreciation for a forged knives. There is simply something about forged knives that is so special. Beyond that, there is another benefit that forged blades mostly has: edge packing.
“Edge packing” has been known for hundreds of years and continues to amaze so many people. The magic happens at the level of crystallization. Namely, by striking the edge of the heated blade, aligning the crystalline structure occurs. That translates into more organized crystals along the edge.
Finally, what that means is improved edge retention and reducing the need for constant sharpening. Remember that while edge packing is real, it is still not a miracle solution. If the steel doesn’t contain the right chemical properties, forging won’t help at all. I know that stock removal is much simpler and cheaper, but if you are a professional knifemaker, you want to produce the best possible blade you can for your customers.
Also, if you are a collector or just a fan of knives, you usually want the best blade you can get, so I would recommend forging stainless steel if possible.
Does forged stainless steel rust?
Before answering this question, I should explain why stainless steel is corrosion-resistant in the first place. That way, you will fully understand the concept of this amazing material.
Ok, I know you want the answer as soon as possible, so here is the short one.
Unfortunately, forged stainless steel can steel rust. However, with proper cleaning and passivation, you will drastically decrease the chances of rusting. To avoid rusting, periodical maintenance is required, including cleaning the steel with warm water, soap, and rust-resistant coating afterward.
Moving on.
As we already said, stainless steel contains chromium (minimum 10.5%, more precisely). Now, chromium reacts extremely quickly with surrounding oxygen to produce a thin oxide layer on the surface of the steel.
Unlike iron oxide, chromium oxide sticks to the steel and acts as a protective barrier. This resistance to oxidation makes this steel low maintenance, which is a deal for many applications. You have four types of stainless steel: austenitic, ferritic, martensitic, and duplex. Austenitic stainless steel is the most common in the industry and stands for over 70% of total stainless steel production. Its chemical properties include a minimum of 16% chromium and 0.15% carbon.
Ferritic stainless steel has lower corrosion resistance than austenitic grades but is much better than martensitic stainless steel. Martensitic stainless steel is characterized by high strength and hardness in heat-treated conditions. That is why they are predominantly used for knifemaking purposes.
Types of stainless steel corrosion
- General corrosion produces the loss of metal over the entire surface. Steel with a pH value of less than 1 is more prone to this type of corrosion.
- Galvanic corrosion is an electrochemical process where one metal corrodes more than the other in the presence of an electrolyte.
- Intergranular corrosion causes boundaries of crystallites to be more likely to corrode than the inside surfaces of the steel. Typically happens after heating austenitic stainless steel (842–1562°F)
- Pitting corrosion causes localized corrosion resulting in holes. Usually occurs at exposure to a chloride-containing environment.
- Crevice corrosion causes localized corrosion between two joining surfaces. It can be between two metals or between metal and some other material.
- Stress corrosion cracking refers to the growth of cracks in the corrosive setting. Corrosive environmental conditions in combination with tensile stresses usually lead to cracking.
Is it safe to forge stainless steel?
I see a lot of people online being worried about forging stainless steel. That is primarily due to the chromium content. I should note here that almost every heated metal produces some form of gas. Some of them are more toxic than others. I wouldn’t expect the fumes coming from stainless steel to be any worse than those found in a welding shop.
It is perfectly safe to forge stainless steel if you respect necessary safety precautions. During the forging process, ensure you have proper ventilation and don’t place your head near the steel. In some cases, wearing a respirator is also recommended.
Most problems typically occur during forge-welding stainless steel in a very small workshop with insufficient ventilation. That happens especially when you over-flux the steel. All these vapors coming out gave me some really bad sinus infections. But this was my fault because I didn’t make any safety precautions.
Note that the longer you work with stainless steel, the higher your chances are of developing some health problems. But for most amateurs who may work only a couple of hours per day, it probably won’t be any problems. To learn more about blacksmithing safety equipment, check Safety Equipment for Blacksmithing.