Tool steels that require high dimensional stability should be aged after hardening or returning. As a result of aging, much of the remaining austenite change into mathnosite. After the aging of the steel, the dimensions of the steel remain stable, which means that its dimensions will not change any more.


In the natural aging method, the work piece is kept in storage for several months, and since this method is not economical, the artificial aging is used. Artificial aging is carried out as follows:

Thermal aging is at temperatures of 100-120 ° C in an oil bath or hot air furnace, depending on its dimensions, for 20-60 hours.
– Fluctuating aging at 100 ° C in an oil bath or hot air furnace for 2-4 hours. Cooling in brine at -5 ° C. This process is repeated several times. Low temperature aging at -80 ° C to -100 ° C. Low temperature cooling operation is carried out in special equipment and reservoirs. For low-temperature cooling, dry ice materials (from -55 ° C to -60 ° C), dry ice-alcohol mixtures (about -80 ° C), liquid air (-191 ° C), liquid oxygen (-183 ° C) Celsius) and liquid nitrogen (-196 degrees Celsius) are used. After all sections of the work piece have cooled down, depending on the defective parameters, it takes about 10 to 20 minutes, the return operation must always be done. For this, it is best to heat the work piece for a short time to 100 degrees Celsius.
Vibration aging. This method takes place at ambient temperature with the help of fluctuations and lasts about 30 minutes.
Aging of orders, measuring components and precision components will result in high stability – dimensional and – form. In molds, it increases hardness and uniform hardness.

Heat treatment of tool steel:

In molding, non-alloy tool steels, cold work steels and hot work steels are more widely used. High-speed steels are rarely used in molding.

Non-alloy tool steels:

In non-alloy steel, its carbon content indicates its properties. The amount of carbon in these steels is 0.45-1.5 degrees Celsius. These steels are often hardened with water. Its hardening depth is about 2-5 mm.
The soft annealing temperature is 680-710 ° C. The return is depending on the application target between 180 ° C and 300 ° C. The hardness and abrasion resistance of these steels will remain stable only up to 250 ° C.
table1: Thermal treatment of non-alloy tools
Practical examples in molding Hardness depth mm Hardness
Cooling materials(quench) Hardness temperature
Hardness after soft annealing
HB 30
Short name according to
DIN 17006
Material number
Cutting molds, Prissy punches 2,0…3,0 65water 770…800190C 105 W11.1545
Cutting molds 3,5…5,058water 800…830190C 45 W1.1730
Hot working mold, stretch punches 3,5…5,062oil790…820217C 75 W1.1750
Deep hole forging molds 2,0…3,560water 790…820170C 55 W1.820
Cold work steels:

Regarding the cold work steels thermal treatment instructions, it is very helpful to take into consideration the manufacturer’s recommendations (Table 2).

Soft annealing, hardening and return temperature depend heavily on its alloying elements and are therefore very different. The cold work steel with the material number 1.2436 at a return temperature of 100 ° C, hardness of 64 HRC, at a return temperature of 200 ° C, will have a hardness of 83 HRC, and at a temperature of 300 ° C, a hardness of 60 HRC.
The hardness of the high-speed steel with the material number 1.3247 after the return is greater than its hardness after the quenching. In addition, in the case of this steel, first of all, it takes up to 400-600 ° C, then in the initial preheating up to 850 ° C and in the preheat secondary to 1050 ° C, and its hardening at a temperature between 1180 and 1210 ° C The temperatures and maintenance periods should be strictly observed.
Table 2 : Heat treatment of cold work steels

Return temperature
Hardness after quenching
Quench material Hardening temperature
Hardness after soft annealing
HB 30
Annealing temperature
Characteristic according to DIN 17006 Material number
300…15065روغن830...800211720...68085 Cr 11.2004
300…15058روغن1050...1020225800..750X 42 Cr 131.2083
250...18064روغن، هوا 980...930239830...800X 210 CrW 121.2436
350...18056روغن860...830238700...66045 NiCr 6 V1.2710
300...16059روغن، هوا 870...840217630...61050 NiCr 131.2721
250...15064روغن820...760211720...69090 MnCrV B1.2842
540...51067روغن، هوا1210...1180820...770S 2-10-1-81.3247
Hot work steels:

The heat treatment instructions of the hot working steels, especially its alloy types, are particularly useful for keeping the heating time and storage time accurate. The hardness of these steels depends on the temperature of the return. For example, steel mold forging with material number 1.2713 at return temperatures below has different strength values. (Table 1)
Table 1:Relationship between strength and return temperature (for steel, 1.273)

700650600550500450400Return temperature
880103012301320142015201620Strength N/mm2

Return temperature
Hardness with strength after quenching Quench material Hardening temperature
Hardness after soft annealing
HB 30
Soft annealing temperature
Short characteristic according to DIN 17006 Material number
500...40058 HRCwater820...790190710...680C 45 W1.1730
650...5502060 N/mm2 oil1000...950219770...74048 CrMoV 6 71.2323
650...5501960 N/mm2oil، air1050...1020235780...760X 38 CrMoV 5 11.2343
670...5501720 N/mm2oil، air1050...1020230780...760X 32 CrMoV 3 31.2365
650...5001860 N/mm2oil870...840240710...68055 NiCrMoV 61.2713

Thermal treatment of structural steels:

In the case of structural steels, not only the increases in the hardness of the strength, but also the maximum amount of toughness that is available are considered. Therefore, the process of thermal treatment of structural steels from tool steels is different.

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