Hardenable martensitic stainless steel for knife blades produced by powder technology.
Modern tool steels for cutting or Nibbler blades are today manufactured from powder materials, RSP (Rapid Solidification Powder) - tool steel. In Söderfors the ASP-steel (trade name) manufactured for 20 years. ASP-steel found its place in the sectors of engineering, where cutting edge durability is essential.
The reason why the powder steel blade provide exceptional hiding in the structure.
Gross Carbide current steel structure reduces the fracture strength. Clusters of carbides can locally concentrate voltage stress. Significantly carbides in powder steels cause the fracture to occur at nearly double to stress. Powder steel have almost twice the fracture strength than comparable steel produced by conventional methods.
The best combination of hardness and toughness is just powdered steel.
Temperature for rolling - Hardware 1160 - 1050 C
The melting occurs at a temperature of 1220 C (2230 F). This means that the steel is quite sensitive to overheating. Burning may occur at too high temperature heating. It must allow for heat deformation. Prolonged heating leads to loss of material due to decarbonisation. Slow cooling or annealing gradually after heating prevents cracking.
Modern tool steels for cutting edge or Nibblers are now made from rapidly solidified powders, RSP - tool steel. In Söderfors the ASP-steel (trade name) manufactured for 20 years. ASP-steel has been of use in these sectors of the mechanical industry, where cutting edge stability is the foundation.
The reason why APS - steel provide exceptional edge lies in the solidified structure.
Coarse carbide structure limits the current steel tensile fracture. Carbide clusters act as initiators of fracture at a certain level of stress. Much smaller clusters of carbides in rapidly tužených materials cause the fracture to occur only at nearly double the level of stress. Powder steel have almost twice the fracture strength than ordinary steel.
The best combination of hardness and strength is precisely in the rapidly solidified powder steels.
The composition of martensitic stainless steels in RWL 34%.
Material C Si Mn Cr Mo V
RWL 34 1.05 0.50 0.50 14.00 4.00 0.20
Temperature for forging or rolling 1160 - 1050 ° C. Melting starts at 1220 ° C, which means an increased sensitivity of the material to overheat, careful monitoring is necessary temperatures recommended by the electric or gas furnace.
Compared to normal steel with a low admixture of pure carbon steel is almost 2 times higher deformation pressure, so the hand forging affects relatively small areas.
Long leads to overheating and popping uhlíkatění material.
Slow cooling after heat treatment we prevent fractures and cracks in the structure (200 ° C). It is recommended to cool or in the sawdust or other insulation material.
Soft tempering (annealing)
Due to the risk of rupture should be no cutting or machining after heat treatment before there was a tempering material, annealing time is 5 hours at 750 to 780 ° C.
(Rod material supplied by damasteel, AB is tempering below 300 HV)
The claim (hardening)
After rough grinding blade is ready for hardening. After quenching affects corrosion resistance of conventional steels. Heat treatment in vacuum brings the advantage of a surface that is without the presence of nitrogen, so it is possible to do this procedure most of the grinding and polishing, and grinding his own statement before the final finishing treatment. Vacuum processing for larger firms.
In our case it is used in an open electric furnace No. 1 and the procedure, the blades normal size to be heated at 1050 ° C (1920 ° F) for 10 to 15 min. Knives should be suspended, is not subjected to unequal temperatures and collapse. For lack of space can be placed knives (stored) on their back and fastened with steel wire. When processing is evolving surface oxides, which can cause uhelnatění surface under its own blade. This problem can be reduced fireproof coating or wrapping it in newspaper covered by flame resistant foil.
After removing the blade must be rapidly cooled below 500 ° C (930 ° F), knives, smaller sizes can be cooled by air. Any protective film should be immediately removed. Uneven cooling causes thermal stresses and distortion, are particularly sensitive long, thin blade. When cooling is good to put a knife into the barrel to prevent access to drafts.
The following chart shows the attainable hardness in HRC, depending on the temperature of annealing and quenching method for material RWL 34 (annealing time for temperatures around 200 ° C 1 x 2 hours, for temperatures around 500 ° C 3 x 1 hour) Low tempering temperatures are recommended for better anti-corrosion properties.
The product is stronger (thicker) by rapid cooling is important. The blade is immersed in water or oil quenching for a short time (just when the red color disappears). Too rapid cooling martensitské structure below 300 ° C (570 ° F) causes unwanted twisting. The cooling temperature is lower, the martensite transformation is complete. Many processors blade cooling in nitrogen at - 80 ° C after quenching and tempering for 15 min. To remove the brittleness of the material popouštíme at 220 ° C for 2 hours, we can use an ordinary kitchen stove (oven).
Recommended processing temperature
hardness of HRC
1050 ° C
220 ° C
1 x 2 hours
1050 ° C
175 ° C
1 x 2 hours
1080 ° C
220 ° C
1 x 2 hours
1080 ° C
175 ° C
1 x 2 hours
1100 ° C
175 ° C
1 x 2 hours
1100 ° C
520 ° C
3 x 1 hour
This treatment includes deep zachlazení at - 80 ° C for 15 min. after quenching and tempering.
Rust (oxides) formed at the claim may be difficult to remove, sometimes gently tilt the blade, so it should start sanding with 80-hrubozrného the tape. When the surface and form in order, followed by continuing finer 120 180, 320 and finally diamond bands from 15 to 6 microns. Beware of blade friction overheating - cooling water is recommended - sprays, etc.
The surface is then polished to a shine. Use a felt wheel and diamond cleaning pastes seems ideal.
Sharpening the blade
Etched blade must be ground to be earlier, until the finished handle and carrying case, because the blade can be easily destroyed in the course of work. After sharpening the blade should be lightly oiled before use and should not touch it with your hands. In addition, the artistically patterned structure, powder metallurgical Damascus also offers excellent performance edge. Resistance against the blade fracture is approximately doubled compared with conventional steels of the same composition. Carbide content is low and allows you to create extremely sharp blades with a radius of about several microns.
Test quality, test paper
Hold A4 paper (typewriter) in one corner and slowly let it hang. Cut diagonally from the top corner down without filing. When the paper is cut into two parts without difficulty, the blade is good. When the rough cut or torn should be re-sharpened or even sharpen the blade.
Test vyštípaného blade. The test timber
After a long period of use of such tools will be deformed or broken down blade that is unable to complete a test paper without some careful sharpening. Cut a piece of wood when a fingertip feel on the surface of small grooves cut is necessary to complete sharpening knives, which will improve the condition of the blade.
Grinding and sharpening
- Stone for wet grinding. C and 200 grain. Peripheral speed up to 100 m / min. (! Error?)
- Three sharpening stones, grain 280, 500 and 1,000 and sewing machine oil
- Polisher with a felt wheel. Max speed 700 m / min
- Diamond polishing paste for steel
When sharpening the blade of Damascus blades, it is important to prevent damage to the patterned sides of the blade. Therefore, the necessity for compliance with the grinding angle support system such as TORMEK
Blade angle is controlled by a simple tool
Be careful when you grind near the grip. It is difficult to avoid excessive grinding at the end of the blade.
First Sand in the direction from the top edge.
Extensively with water. Use nupevnění blade for good control
angle of the blade.
Sand carefully on both sides and be careful to have the same cut
thickness along the entire blade. When you can feel with your fingernail along the rough edge of the blade is the right time to focus.
Second Focus. Attach a base product to screw vice.
Third After sharpening the blade on one side coarse blade. This rough side of contact in the buttressing up.
4th Apply sharpening stone grit 280 Always work and a little oil until the blade is equal to the lower gross sleeker side.
5.Otočte blade sharpening and repeat. Repeat the same procedure with stone grit of 500 and 1000.
7th The last remnants of the gross short blade is removed by polishing with a felt disc. Polish down towards the blade. Too long or polishing too much pressure can damage the quality of the blade.
Use a paper test
8th If not available on the felt polishing disk can be replaced obtažením on a piece of leather.
This service meets the normal leather belt.
When the knife is normally used, it should always be sharpened blade to stand up in a paper test. If the blade is damaged, it is sufficient to focus in sections 3,4,5,6, and 8