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.