Can You Forge Weld Mild Steel? (2021)


Forge welding is considered to be one of the fundamental blacksmithing skills. However, it is generally recommended to learn forging techniques first such as drawing out, bending, cutting, upsetting, etc. After that, you should learn forge welding as soon as possible. Choosing the right material before you start forge welding is crucial. In this article, I will focus on mild steel.

So, can you forge weld mild steel or not?

You can forge weld mild steel. In fact, mild steel is one of the most popular materials for forge welding among blacksmiths. Mild steel can also be forge-welded to high carbon steel. Due to low carbon content, mild steel requires higher forge welding temperatures than high-carbon steel.

In the rest of the article, I will discuss the quality of mild steel for forge welding, forge welding tips for beginners and forge welding with other types of steel. So, make yourself comfortable and let’s dive in.

Is Mild Steel Good for Forge Welding?

Mild steel is very strong steel made from natural and readily available materials. It has a very low carbon content (0.05%-0.3%). Mild steel is one of the most popular steels used in blacksmithing for both forging and forge welding purposes, mainly due to its price and availability. Because of its low cost, mild steel is often used when a large volume of material is required. Another benefit of mild steel is that it has good “forgeability”, meaning it is easy to shape with a hammer.

For all above-mentioned reasons, mild steel is the favourite choice of the material for beginner blacksmiths. It is hard but also malleable, which makes it a great choice for various purposes like construction materials and car manufacturing. A36 and 1018 steel are the two most commonly used mild steels in blacksmithing. Both of them offers a good balance of toughness, ductility and strength.

Note that as the carbon content increases, the forge welding temperature of the steel decreases. This is why mild steel requires higher temperatures than steels high in carbon. Mild steel is also less likely to crack after it has been forge-welded which makes it an excellent choice for this purpose.

Due to the high forge welding temperature, mild steel allows you to work much longer. This is great news for a beginner blacksmith trying to learn forge welding.

Forge Welding Mild Steel to High Carbon Steel?

Ok, we know that mild steel can be forge welded. But what about forging it to other steel, like high-carbon steel for example?

Mild steel and high carbon steel are compatible in terms of forge welding. Note that the high carbon steel cracks at a sparking heat. This is why you should use the lowest forge welding temperature of the steel involved in the process. When doing this, mild steel should be placed first in the forge.

In order to explain what happens during forge welding mild steel to high carbon steel, I have to address the concept of Transient Liquid Phase Diffusion Bonding. Actually, this one is neither liquid diffusion bonding nor solid diffusion bonding. Technically, it is considered to be solid-state as the liquid interface forms only temporarily and the liquid solidifies before cooling down.

This means it solidifies at the forge welding temperature. Liquid-state diffusion primarily relies on the production of the liquid phase at the bond which is filling the gaps in the surface. It eventually solidifies. Ok, enough science for now.

Have you ever wondered why an axe bit is called a bit? It is because a bit of high-carbon steel edges us forge-welded into the mild steel or wrought iron of the axe body. It is also known as a cleft weld, like a birds mouth. Also, a lot of carpenters chisel had a little bit of high carbon steel welded to mild steel on the non-bevelled side. That allowed constant sharpening into the high carbon.

The weld of these two materials takes place at a “sweating heat” with no sparks flying from the metals. The steel is at near white incandescence and it looks sweaty on the surface on which the flux and scale have melted together. The borax is typically used for this purpose. There is one more thing I should mention.

Do not use heavy blows. Instead, use light blows in the start and gradually increase the intensity once the two materials cohere. Keep in mind that a weld that is angled across the direction of the biggest stress will distribute the stress rather than making for a much stronger joint.

However, forge welding of mild steel to high carbon steel is not recommended to beginners. Instead, use two pieces of mild steels and forge weld them together. This kind of weld is considered complicated nowadays, but in the past, it wasn’t so hard, because it was the only way to weld.

What About Forge Welding to a Spring Steel?

In most cases, you will hear from many blacksmiths that spring steel is generally not good for forge welding. This is mainly due to the small amount of chromium they

contain. Namely, the formation of very stable and unaffected chromium oxide upon heating makes it extremely hard to forge weld. However, recently I went to my friend which succeed to forge weld mild steel to spring steel.

He ran his gas burner in a reducing range, but the biggest “secret” was adding finely ground charcoal to his borax (50/50 mix). But the charcoal needs to be almost dust to work. If you leave it the size of sand it will most likely to fail. This one is known as the Alaska flux. Understand that the carbon content decreases the chromium oxide back to chromium while the flux washes it out of the way.

Keep in mind that this was just one experiment. Just because he did it doesn’t mean that suddenly spring steel is good for forge welding. I still would not use it for this purpose unless I absolutely have no other choice.

3 Forge Welding Tips for Beginners

As I have already said in the beginning, forge welding is not easy to learn. This is why every piece of help is more than welcomed. In this article, I decided to give you 3 simple tips for all beginners.

Prepare everything

Before you take the material out of the forge, everything should already be prepared for hammering. Make sure you anvil is not far from the forge, otherwise you will lose your heat. You should know exactly where your hammer is when you take out the heated material. Everything needs to be in its place so you can start hammering as quickly as possible.

In the beginning, strike the material lightly, not hard. Apply the blows to the entire surface of the material. Hit it just enough to fuse the pieces. No more no less. Hitting too light won’t displace the flux. On the other hand, hitting too hard will simply distort the material.

Use flux

As a beginner, don’t try to imitate the experts. Just because you saw some master blacksmith on the youtube forge welding without flux very easily doesn’t mean you should also. The purpose of the flux is to reduce the temperature at which scale and other bad chemicals become fluid on the surface of the steel. Simply said, flux protects the surface of the metal from erosion.

Choosing not to use flux forces you to raise the temperature in order to make the surface chemicals fluid. I always recommend using flux for beginners. While it may not be absolutely necessary, it will make your life easier. However, keep in mind that no matter how much flux you use, make sure your material is cleaned properly. Otherwise, you won’t get a weld.

Borax is considered to be the most reliable and consistent flux for forge welding purposes. It is also a readily available and very cheap option. You can also mix borax with some other additives for better effect.

Minimize the distractions

Learning to forge welding requires a lot of focus and one of the ways of achieving that is to reduce as many distractions as possible. Forge welding is all about the right timing. Knowing when to remove the material from the forge, knowing when to stop hammering are just a few important things. You need to keep your attention as sharp as possible.

Turn off the radio and music. Instead, listen to the sound of the forge and airflow. Are you getting enough air? Are you getting too much air? Are paying attention to the color of the material? These are very important things. Also, try not to talk with anyone when you practice forge welding.

If someone enters the shop while you are doing forge welding, ask them to leave if possible. If you think it is difficult to forge weld, try teaching it. It will drain your energy levels very quickly explaining someone how to do it properly.

Recommended reading:

The Complete Guide to Forge-Welding with a Propane Forge

Can You Forge Weld Rebar? (2021)

Albert from Wyoming

Hi, Albert here... Forging World is the place where I share everything I've learned (and still learning) in my 20ish years of experience in forging. Hope you like the blog and #keepforging #keeplearning

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