On 2018-08-08 14:48:54
Heat treatment practice of H13 die steel
H13 die steel can be heat treated to obtain excellent properties, such as high strength, red hardness and high impact toughness value. Starting from the analysis of chemical composition of H13 steel, the selection of high temperature spheroidal annealing, quenching and secondary tempering are explained, the process data are provided, and five experiences obtained from production practice are given in the conclusion.
H13 steel is a kind of hot working die steel widely used in the world, because it has good impact toughness, wear resistance, ductility and thermal hardness under high temperature, it is used in the manufacture of die-casting die, hot forging die and extrusion die. This paper introduces the heat treatment process of H13 steel after modified forging.
The chemical composition of steel
H13 steel is ANSI steel, equivalent to 4Cr5MoSiV1 in GB/T1299. There are Cr, Mo, Si, V and other alloying elements in H13 steel , as shown in table 1. In addition to the fact that Si elements do not form carbides, Cr, Mo and V will combine with carbon to form special carbides, which will improve the fire resistance of the steel.
Influence of Cr: Cr can combine with carbon to form special carbides. When the carbides of chromium are dissolved in austenite, the stability of supercooled austenite can be improved. When it is solid dissolved in martensite, it helps to improve its tempering ability and promote secondary hardening effect. The main purpose of most Cr is to improve the hardenability, high temperature strength and high temperature oxidation resistance of H13 steel .
Influence of Mo: Mo is also a carbide forming element, which can improve tempering stability and wear resistance of H13 steel.
Influence of Si: improve the strength, hardness and resistance of steel, and weaken the oxidizing atmosphere in the heat treatment furnace.
Influence of V: reduce the superheat sensitivity of steel, improve the tempering stability and secondary hardening effect of steel, the dispersed vanadium carbide particle can greatly improve the wear resistance of steel.
H13 steel has good red hardness, high temperature toughness and thermal fatigue resistance after heat treatment. In order to ensure the quality of heat treatment, attention should be paid to the following points in production:
1) inspection of raw materials: macroscopic defects shall be inspected and defects such as slag inclusion, central shrinkage cavity, folding and surface crack shall be found in time.
2) after forging, the forging shall be cooled down or cooled down with the furnace and annealed in time.
3) as H13 steel is easy to oxidize and decarburize, the blank of forging die should be appropriately increased to avoid soft spot after quenching.
4) the mold must be annealed at low temperature before being re-hardened to avoid cracking.
5) in the process of heat treatment, the operation shall be performed in strict accordance with the operating instructions.