How To Weld Tool Steel: 10 Tips

Tool steel has a low carbon content and can be welded using conventional methods. It is important to use tools specially designed for tool steel due to its high tensile strength, hardness, and wear resistance properties. Tool steels are often used in cars and other industrial projects.  

Read on to discover ten of the most vital tips for welding tool steel. We will discuss some of the properties for welding and repairing tool steel and what tool steel is typically used for. Additionally, we will discuss some of the different types of tool steel and how to weld those correctly. 

Do I Need to Preheat Tool Steel Before Welding It?

Preheating tool steel is done using an acetylene torch or other high-temperature source and heating the welded metal with that flame. When the welded area becomes red hot (about 400 degrees Fahrenheit), turn off your torch and continue welding. 

Tool steel must be preheated before welding. It cannot be welded at room temperature. To weld successfully, more heat is required. To weld hardened steel, it must be reheated and maintained at a temperature close to the tempering level.

The welder must have safety gear in order not to get burned while working near any fire. Safety goggles should always be worn when around some heated object because they protect against flying objects which can come from one direction at any time without warning.

How Is Tool Steel Different from Other Types of Steel?

Tool steels come in different grades according to their hardness and other properties. These grades make tool steel different than many other types of steel. Because of this, they must be handled and welded much differently. Some of the most well-known types of steel are: 

  • O (tool steel)
  • HSS (high-speed steel)
  • W (water hardening)
  • TCT (tungsten carbide tooling steel). 

Tool steels are different from other steel types because they are specially formulated and hardened as tools such as drills, dies, and cutting edges. Its hardness makes it difficult to form by machining but easier than others when used at higher temperatures without developing brittleness.

Weldability varies with grade. Welders should be knowledgeable about how each type of steel is welded. For example, water or oil quenched alloy such as W may only need preheating before welding, while air-cooled alloy like HSS will require post-heating after welding.

What Is the Welding Process for Tool Steel?

To weld steel, it must be preheated to a specific temperature before welding. The correct heat will depend on the type of wire you are using (for example, if you’re using an arc torch rather than shielded) but should never exceed the original color put into the tool. Preheating on a furnace is preferable but not always possible without proper tools.

The process for welding tool steel involves using a stainless rod for non-critical areas and preheating to the original tempering temperature of your tools. Anneal tools go into the furnace once they’re preheated. Post heat at 50 degrees Fahrenheit below your original tempering level.

Annealed tools should also be re-annealed through hardening and tempering to make them more durable and reduce the hardness gradient across their surface due to heating, cooling, and working cycles during machining. 

The principle of preheating your welding area is vital because, without these precautionary steps, cracks could form in the weld as thermal stresses move metal past its melting point. Local conditions may vary these instructions, but there are general guidelines that should be followed.

What Is the Correct Bevel Depth for Tool Steel?

When welding, prepare the pieces to be welded by cutting a 45-degree angle on all areas that will contact each other. For example, if the pieces have a triangular shape, you need to cut 3-45 degree bevels to touch at their corners when joined together.

The correct bevel depth for tool steel is having one-third of the total thickness as the depth when welding tool steel. This ensures you have enough welds on both sides to align them with each other.

The bevel width has a crucial role in the welding process. Without enough of this surface, you may have trouble getting a good weld and keeping it steady while you’re applying pressure to keep the weld going. Be sure to use the correct depth and angle to keep your welds as sturdy and durable as possible. 

Should I Post Heat Tool Steel After Welding?

After welding tool steel, the metal should be placed in a furnace to anneal. Post Heating is the process of heating the weldment to a temperature between 850- and 1150-degrees Fahrenheit. Post heating is also known as “heat treatment.” 

When welding with hard tool steel, it should first be permitted to cool down to 700°C and then post-heated. The duration of the post-heat must be specific to the cross-section of metal welded.

When heavy machining or grinding is required to remove excess weld metal, the die should be post-heated again to relieve the stresses set up by machining, etc. When tool steel has reached an optimum post-welding tempering range (usually 900°F), it should be heated no higher than 1275°F because any more than that would change its strength properties. 

This process reinforces welds by relieving mechanical stresses in metal, removing residual stresses from welding heat cycles, stabilizing the grain structure of the welded area for better corrosion resistance, and improving machinability characteristics.

Can I Repair Tool Steel?

Tool steel welds must be ground smooth, and then the welded area should be preheated to 500°F before welding occurs. Once welded, the die should be post heated again to relieve stresses from machining, etc. 

Tool and die steels will wear out or become unexpectedly damaged in service but can be repaired with welding. This is structurally sound and economical because it provides quick relief for punch and die components prone to damage.

After a repair, the dies are usually cooled in water for one hour or until they reach room temperature, depending on which option is chosen by the manufacturer of the material being heat treated. This process reinforces welds by:

  • Relieving mechanical stresses in metal
  • Removing residual stress from welding and heat treating

It helps welds solidify.

The weld repairs should be made as soon as possible to take advantage of the tempering effect they have on tool steel. It is not recommended for welders to make weld repairs in hardenable steels where welding will be followed by quenching or other treatments. 

These are known to cause embrittlement, leading to severe cracking under stress (not just at the weld). In cold-working die and punch components, such cracks could render them useless. 

What Welding Rod Do I Use for Tool Steel?

The weldability of tool steel has been improved in recent years with appropriate weld rods and techniques. Still, those welds are not as strong as they should be due to an excessive amount of hydrogen present from welding at higher temperatures than necessary. 

For welding thick metals, such as structural steel, welders often use E7018 weld-repair weld rods. These electrodes can also produce strong welds with high impact properties – even in cold weather – and work on carbon steel, high-carbon, low-alloy, or high-strength base metals.

You can use two weld-repair weld rods for tool steel: a low-carbon type or high carbon. 

  • A low carbon weld rod is better than no weld at all. Still, it’s not going to work as well on tough alloy steels because, like aluminum, there is a tendency for the weld metal and base metal to react due to their dissimilarity in composition. 
  • The higher carbon content of this welding rod makes it more suitable for repairing cracks that may be caused by stress relief welding with hardenable parts such as stainless steel or case-hardened tool steel. 

For minor surface defects only, a 360° weld would suffice without affecting toughness as long as the part isn’t stressed again too soon after heating up.

Can You Weld O1 Tool Steel?

The most common tool steels are O-series (ordinary) grades, followed by D grade or “high-speed steel,” which is more expensive but provides greater wear resistance for forming tools and dies. O series steel, like O1 steel, is weldable with the right composition, heat treatment, and welding process.

O1 steel is weldable, but the process is complex because it tends to crack. When repairing hardened and tempered O1 steel, it should be preheated to the same tempering temperature and welded at that level.

O1 is oil-hardening steel that can be used as non-shrinking, non-deforming tool steel. Due to the properties of this type of steel, it must use temperatures below 540 degrees Celsius and be hardened to Rockwell Hardness C65.

You can weld O1 Tool Steel by following these steps: 

  • Remove excess weld metal 
  • The die should be post-heated again to relieve stresses set up by machining and heat cycles.
  • When tool steel has reached an optimum post-welding tempering range (usually 900°F), it should not exceed 1275 degrees Fahrenheit so that its strength properties remain high. 

This process reinforces welds by relieving mechanical stress in metal, removing residual welding stress from heat cycles, and improves machinability characteristics. These processes should be followed whenever welding tool steel ensures you have a solid weld and sturdy end product. 

What is O1 Tool Steel Used For?

O-type tool steel is a weldable, high-carbon alloy that offers good toughness at elevated temperatures and weldability. O1 tool steel has many uses, including some that you may find in your own home. 

O1 tool steel can be used for cutting tools in industry and knives, and other blades meant to withstand heat because it has an excellent combination of strength properties.

Tool steels are costly due to the work required for refinement. They must undergo several steps before being considered ready for use by manufacturers. The most notable process is carburization, which requires heating carbon up to 1500 degrees Fahrenheit until it becomes liquid and then injecting this into bars.

Other Tool Steel Applications: 

  • Cutting tools (axes)
  • Drilling bits 
  • Molds for crankshafts 
  • Automotive parts (brakes) 

The finish of tool steel is classified as either “ground” or “milled.” Ground steels are typically very coarse and can have weld lines that need to be ground away, while milled finishes look smooth and clean in appearance because they are cut with a machine instead.

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What Is O1 Tool Steel Composition?

O1 Tool Steel is a high carbon steel alloy that provides excellent cutting and other machining applications. The composition of O1 tool steel is different from many other types of steel out there but gives it a unique edge. 

The composition of O1 tool steel offers high carbon content, which increases its hardness and wear resistance while improving enforceability. O1’s manganese levels improve hardening, stability, and dimensional accuracy.

The composition of “O” type steel also contains more manganese than other types of steel, which produces higher hardness. This is why tool steel is used for high impact tools like drill bits and some knife sets.

O1 Tool steel also contains:

  • Silicon
  • Phosphorus 
  • Sulfur
  • Niobium
  • Titanium
  • Copper

“O” steel is a high carbon tool steel made from the best qualities of many different plates of steel that are combined in a particular proportion to produce an alloy with desirable properties at least equal to those it was designed or intended to replace. 

Conclusion

Tool steel is a high-end metal alloy with many properties that make it an excellent choice for machining. It can be welded using conventional methods, but special tools are required when working with tool steels due to their toughness and hardness. These metals are often used in automotive or aerospace applications because of their strength at such low weights.

They have a low carbon content which makes them easier to weld with conventional methods. The high tensile strength and wear resistance properties of these alloys make it essential that tools are designed specifically for this type of material. Otherwise, your project will not get good results due to excessive heat generation when cutting through the metal chip control during welding techniques. 

Sources

https://www.millerwelds.com/resources/article-library/stuck-on-stick-easy-answers-to-not-so-simple-questions-about-common-electrodes

https://www.grainger.com/category/welding/filler-metals/tig-welding-rods?attrs=Material%7CTool+Steel&filters=attrs

https://www.uddeholm.com/files/TB_welding-english.pdf

https://weldreality.com/TOOLSTLS.htm

https://www.welding-advisers.com/Welding-Tool-Steel.html

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Alexander Berk

A bit about myself: I am a certified international welding engineer (IWE) who worked in different welding projects for TIG, MIG, MAG, and Resistance Spot welding. Most recently as a Process Engineer for Laser and TIG welding processes. To address some of the questions I frequently got asked or was wondering myself during my job, I started this blog. It has become a bit of a pet project, as I want to learn more about the details about welding. I sincerely hope it will help you to improve your welding results as much as it did improve mine.

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