How is Tool Steel Made?
Different materials are used for different purposes and have their own merits and demerits. Steel is one of the most widely used materials. Tool steel as the term suggests is a type of steel that is used for making tools. It contains different amounts of tungsten, chromium, molybdenum, magnesium, cobalt, manganese, and vanadium. It is a carbon steel alloy that is used for making tools due to their distinctive characteristics which make them suitable for making tools including:
- Corrosion Resistance
- Cryogenic Toughness
- High-Temperature Resistance
- Good Strength
- Greater Hardness
- Excellent Formability
- Shape Maintenance
- Superior Tolerance
- Ease of fabrication
Tool Steel is available in different grades and forms such as
1. Water Hardening (W)
2. Air Hardening (A)
3. Oil Hardening (O)
4. D type (D)
Each grade has its own characteristics and uses. The choice depends on the purpose of the use, for instance, working temperature, strength, hardness, cost-effectiveness, and toughness.
Water Hardening (W grade) is high-carbon steel. It is economical and suitable for lower temperatures only. They are water quenched and commonly used for manufacturing cutting and embossing tools, cutlery, and knives, etc.
Air Hardening (A grade) is used for various purposes and has lesser deformation under heat treatment. It is corrosion resistant and has good machinability. It is commonly used in applications such as embossing, cold forming, wood carving knives, die bending, coining, and several others.
Oil Hardening (O grade) has a higher level of toughness and corrosion resistance. It is used for several purposes including engraving rolls, die blanking, drill bushing, cold forming collets, etc.
D type or D grade has a high carbon and chromium content. It has cumulative characteristics of air-hardening and water hardening tool steel. Common applications of this grade are die cuts, paper, and wood carving knives, rotary slitters, seaming and forming rolls, etc.
Tool Steel Making Process
The processes used to produce tool steel are listed below
1. Electric Arc Furnace Melting
2. Electroslag refining
3. Primary breakdown
5. Hot and cold-drawing
6. Continuous casting
7. Powder Metallurgy
8. Osprey process
Electric Arc Furnace Melting (EAF)
Most the tool steel is produced by using scraps and these scarps are melted in Electric Arc Furnace, transferred to another container and then refined. The refined metal is sent to the casting station after which it is transferred to the ingots. They are then heated and allowed to cool down in order to prevent cracking.
Electroslag Refining (ESR)
The second process is Electroslag refining which involves melting in order to produce ingots that are free from imperfections and defects. This process improves the surface, workability, cleanliness, stress resistance, and ductility.
This process requires specific machinery such as rotary forging or open die hydraulic machines. These machines can produce various sizes and shapes of metal with good quality, fewer cracks, seams, and good alignment.
Rolling mills in rows are used to produce a steel sheet. This is done after heating the metal in the furnace which allows quick heating without decarburization. It is an automated process.
Hot Drawing and Cold Drawing
Drawing the technique is used especially in tool steel in order to obtain close tolerances, special shapes, and smaller sizes. Tool steels have good strength and medium ductility. Hot drawing provides better strength to the metal and cold drawing provides closer tolerances. This process is helpful in preventing cracking.
This process is performed in order to reduce the cost of production of tool steel. It also helps in improving the properties of the metal by annealing, rolling, and hammer forging.
Other processes such as powder metallurgy and osprey are used to produce high carbon and chromium metals which results in better properties including machinability, grind-ability, and heat treatment response.