H-13 is a chromium, molybdenum, vanadium hot work tool steel which is characterized by high hardenability and excellent toughness. The molybdenum and vanadium act as strengthening agents. The chromium content assists H-13 to resist softening when used at high temperatures. H-13 offers an excellent combination of shock and abrasion resistance, and possesses good red hardness. It is capable of withstanding rapid cooling and resists premature heat checking. H-13 has good machinability, good weldability, good ductility, and can be formed by conventional means.
Typical applications for are forging dies, forging die inserts, hot gripper dies, hot nut tools, hot header dies, brass forging and pressing dies, aluminum base dies, aluminum casting and extrusion dies, zinc die casting dies, extrusion mandrels, plastic molds, cores, die holder blocks, hot press dies, hot work punches, etc
Heating for forging must be done slowly and uniformly. Soak through at 1900°-2000°F and reheat as often as necessary, stopping work when the temperature drops below 1650°F. After forging, cool slowly in lime, mica, dry ashes or furnace. H-13 should always be annealed after forging.
Heat slowly to 1550°-1650°F, hold until entire mass is heated through, and cool slowly in the furnace (40F per hour) to about 1000°F, after which cooling rate may be increased. Suitable precautions must be taken to prevent excessive carburization or decarburization.
When desirable to relieve the strains of machining, heat slowly to 1050°-1250°F, allow to equalize, and then cool in still air (Strain Relieving).
PREHEAT PRIOR TO HARDENING
Warm slightly before charging into the preheat furnace, which should be operating at 1400°-1500°F.
H13 is a steel having very high hardenability and should be hardened by cooling in still air. The use of a salt bath or controlled atmosphere furnace is desirable to minimize decarburization, and if not available, pack hardening in spent pitch coke is suggested. The temperature employed is usually 1800°-1850°F, depending on size section.
Quench in still air or dry air blast. If complicated forms are to be hardened, an interrupted oil quench can be used. Quench part in oil and remove from bath when it just loses its color (1000°-1100°F). Finish cooling to below 150°-125°F in air, then temper immediately.
Tempering practice may vary with size and application, but is usually performed in the range of maximum secondary hardness or higher. Double tempering is recommended. The results below is H13 that was air quenched from 1800°F and tempered for 4 hours at various temperatures. The results may be used as a guide, keeping in mind that parts of heavy section or mass may be several points lower in hardness.