1.718H mold steel is hardened and tempered before delivery, pre-hardened to 35~39HRC, with the following advantages:

No risk of cracking and heat treatment deformation;

No heat treatment cost;

Shorter tooling cycle time;

Reduced tooling costs (e.g., no need for distortion);

Easy mold correction;

Nitriding and eye hardening treatment can be applied to improve the surface hardness and wear resistance of the mold.

2.718H mold steel is similar to American material P20 mold steel, mainly used in:

Large long-life plastic injection mold, such as home appliances, computer cases and other molds;

High surface finish of plastic products mold;

Blow molding molds;

Due to the high hardness, it can be used in plastic molds for sliders;

Forming tools, compression braking molds (bending machine molds), (flame hardening or nitriding treatment can be applied depending on production needs);

Structural parts and shafts;

3.Treatment processing:

Annealing: In protected condition, heated to 700°C, heated evenly, cooled to 600°C in the furnace at 15°C/h, then air cooled.

Stress relief: After rough machining, heat to 550°C, hold for 2 hours, cool slowly to 500°C, then air cool.

Quenching and Tempering: Before quenching, it must be fully annealed to eliminate machining stress. Preheat at 500~600C for 2 hours and hold at 850°C quenching temperature for 30 minutes; to be heated and held in a protective atmosphere to avoid decarburization and oxidation. Then cool in oil, or 300°C isothermal for 4 minutes and then air cool. When cooled to 50-70°C, should be tempered immediately.

Flame quenching and tempering:It can make the mold surface hardness increase and make the wear resistance increase. The method is to use oxygen 2 acetylene flame (wind coal) in the mold surface heating, and then cooling hardening, hardness up to 45 ~ 52 HRC. treatment: preheat 150 ~ 200 HRC to prevent cracking; then in the mold surface continuous heating to 850 ~ 950 ° C (the surface is light red), and then to air cooling; cooling to 50 ~ 70 ° C, immediately at 180 ~ 200 ° C tempering, to prevent grinding to prevent cracking.

Carburizing: Carburizing temperature is 850~940°C and the time is determined by the depth of the product required. If the carburizing temperature exceeds 880°C and the time exceeds 2 hours, normalization must be performed to maintain the fine grain size. After carburizing, it is cooled to 830°C in the furnace, quenched in oil and tempered at the tempering temperature as listed; this increases the surface hardness and wear resistance. If only high hardness is required but not fine grain, it can be quenched at a carburizing temperature of 880°C or more.

Nitriding treatment: Nitriding treatment can get a harder surface layer, at the same time, there is good wear resistance and corrosion resistance, the hardness after nitriding treatment in ammonia can reach 650 HV. 570°C under soft nitriding treatment, can get the surface hardness of 700 HV, after 2 hours of treatment, the hardening layer depth is 0.01mm.

Hard chrome layer overlay:Tools that have been covered with a hard chrome layer must be tempered at 180°C for 4 hours to avoid hydrogen embrittlement.

Grinding: The correct grinding technique can avoid cracks and increase the life of the tool. Materials that have been tempered at low temperatures are highly susceptible to cracking during grinding, when grinding wheels must be dressed and softer and open grain wheels are suitable, while adequate lubrication and proper circumferential speed are also important.

Polishing: 718H mold steel has good polishability, usually polished with aluminum oxide powder and drilling plaster, polishing steps are as follows:

a.Finish the size and then prep 0.05mm ;

b. Polishing with No.45 drilling plaster to get a less sharp surface;

C. Use No.15 drill plaster to polish again;

d. Finish the surface with No.3 or special high grade drill plaster;

Each metal has a suitable polishing time, which is determined by the hardness of the material and the polishing technique, too long polishing time will produce a bark-like (orange peel-like) surface.