RWL34

RWL34 is a sintered steel based on ATS34 steel. ATS34 was originally developed in Japan by Kobe Steel for making ball bearings. Renowned knifemaker Robert W. Loveless was the first to use Japanese steel in cutlery due to its remarkable properties. Damasteel has enhanced ATS34 steel through sintering, achieving an exceptionally high level of purity. The sintered variant is named after the knifemaker Loveless (abbreviated as RWL) and is not quenched (subjected to workability annealing) to facilitate processing. It can be hardened up to 64 HRC.

Steel Properties

• Stainless
• Long-lasting
• High purity - resulting in a homogeneous microstructure and good sharpness
• High toughness - extremely insensitive to breaking, twisting, and impact loads
• Easy to work
• Easy to polish

Operating Temperature 1050-1160°C

Compared to low-alloy steels, martensitic stainless steels have higher and nearly doubled deformation resistance. Hand forging can only be done on relatively small sizes. Melting starts at 1220°C, making the material highly sensitive to overheating. Good temperature control is essential, and an electric or gas furnace is recommended.

Long soaking times above 850°C lead to decarburization and scale formation.

After the hot working process, slow cooling is recommended due to the risk of cracking when the material phase transforms to martensite at about 200°C. The use of vermiculite or other thermal insulation material is recommended.

Thermal Treatment

Due to the risk of cracking, machining, cutting, or hot working is not necessary until the material is fully transformed. The recommendation is to anneal the material completely, meaning one hour at 900°C, then cool to 750°C for an hour, and finally hold at 750°C for four hours. All martensitic material supplied by Damasteel is soft annealed at 230-280 HV (20-28 HRC).

Cold Working

Martensitic stainless steel does not cold work as easily as conventional austenitic stainless steels, but it can be formed and fabricated by a full range of cold working operations. Cold working ductility is good, and any cold working process will increase the material's strength and hardness.

Welding

When martensitic stainless steel cools after any hot process, the martensitic phase transformation occurs at about 200°C and can lead to cracking. This can be avoided by preheating the piece or performing a post-weld heat treatment. Our RWL34TMM can be welded using a full range of conventional welding methods.

Machining

Similar to conventional austenitic stainless steels, martensitic steels have some specific workability properties. Martensitic stainless steels are generally easier to machine than other types of stainless steel. The machining characteristics for our martensitic stainless steel RWL34 include:

• Low tensile strength but strong work hardening
• Tendency to accumulate material on the tool edge
• Hard and stringy chips can be prevented by using curling tools

Grinding and Polishing

Normal grinding and polishing procedures for austenitic stainless steel can also be used for martensitic stainless steel.

Grinding Wheel Recommendation:

Silicon carbide, 46 grit, soft, open density, ceramic bonded. (C46J6V)

• Speed: 35 m/sec
• Feed: 0.01-0.05 mm/stroke

The workpiece speed can be 1/6th of the grinding speed.

Hardening:

For knife applications, the following heat treatments are recommended for a thickness of 3.2 mm.

The suggested heat treatment processes IV and V include deep freezing (DF) at -80°C to ensure achieving the best corrosion-resistant properties. For knife applications, a low tempering temperature is recommended.

The following time-temperature curve can serve as a guide.

Hardening: Temperature 1050° C

Soaking time 1.5 minutes per mm thickness, cooling between aluminum plates in forced air

Tempering:

2 times for 40 minutes