Menu Close

Ageing

Goal:

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.

Methods:

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:

  1. 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.
  2. – 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.
  1. Vibration aging. This method takes place at ambient temperature with the help of fluctuations and lasts about 30 minutes.

Applications:

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.

 

Table 1: Thermal treatment of non-alloy tools
Practical examples in molding Hardness depth mm Hardness

HRC

Cooling materials(quench) Hardness temperature

C

Hardness after soft annealing

HB 30

Short name according to

DIN 17006

Material number
Cutting molds, Prissy punches 2,0…3,0 65 water 770…800 190 C 105 W1 1.1545
Cutting molds 3,5…5,0 58 water 800…830 190 C 45 W 1.1730
Hot working mold, stretch punches 3,5…5,0 62 oil 790…820 217 C 75 W 1.1750
Deep hole forging molds 2,0…3,5 60 water 790…820 170 C 55 W 1.820

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
Material number Characteristic according to DIN 17006 Annealing temperature

C

Hardness after soft annealing

HB 30

Hardening temperature

C

Quench material Hardness after quenching

HRC

Return temperature

C

1.2004 85 Cr 1 680…720 211 800…830 oil 65 150…300
1.2083 X 42 Cr 13 750…800 225 1020…1050 oil 58 150…300
1.2436 X 210 CrW 12 800….830 239 930…980 Oil, air 64 180…250
1.2710 45 NiCr 6 V 660…700 238 830…860 oil 56 180…350
1.2721 50 NiCr 13 610…630 217 840…870 Oil, air 59 160…300
1.2842 90 MnCrV B 690…720 211 760…820 oil 64 150…250
1.3247 S 2-10-1-8 770…820 1180…1210 Oil, air 67 510…540

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)
700 650 600 550 500 450 400 Return temperature

 

880 1030 1230 1320 1420 1520 1620 Strength N/mm2

 

Material number Short characteristic according to DIN 17006 Soft annealing temperature

C

Hardness after soft annealing

HB 30

Hardening temperature

C

Quench material Hardness with strength after quenching Return temperature

C

1.1730 C 45 W 680…710 190 790…820 water 58 HRC 400…500
1.2323 48 CrMoV 6 7 740…770 219 950…1000 Oil 2060 N/mm2 550…650
1.2343 X 38 CrMoV 5 1 760…780 235 1020…1050 Oil, air 1960 N/mm2 550…650
1.2365 X 32 CrMoV 3 3 760…780 230 1020…1050 Oil, ail 1720 N/mm2 550…670
1.2713 55 NiCrMoV 6 680…710  240 840…870 Oil 1860 N/mm2 500…650

 

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.

Leave a Reply

Your email address will not be published. Required fields are marked *