DE2010125C3 - Process for the partial hardening of workpieces or tools - Google Patents

Description

The invention relates to a method for the partial hardening of workpieces or tools, with the it is possible to extend the scope of the known ri Warm bath hardening or the intermediate stage conversion to expand significantly and special advantages to achieve. It is known that in the case of the hardening processes mentioned, hardening does not take place until cooling from the relatively low hot bath temperature in the air, so that greater distortion is prevented and the risk of hardening stress cracks due to the temporal separation of the cooling and framework stresses is practically avoided.

The method according to the invention is characterized in that the workpieces are placed in a hot bath a temperature corresponding approximately to the intended transition temperature is heated or at this temperature are maintained, so that the zones intended for hardening are preferably through Induction heating brought to the hardening temperature and the workpieces at least up to temperature equalization be left in the hot bath, after which the cooling to room temperature is carried out in air.

Although it is preferred, the zones of the workpieces or tools that are intended for hardening Bringing it to the hardening temperature by inductive heating can of course be used for this purpose other methods, in particular flame or plasma heating, can also be used.

It goes without saying that the choice of the specific process conditions, in particular the hot bath temperature and the special type of hardening (intermediate stage conversion) are tailored in each individual case to the type of steel and the requirements applicable to the workpiece and are thus left to the skilled person skilled in this field must stay. In general, however Warmbadtemperatur will range between 150 and 500 ⁰ C. That this is the case with this procedure? the workpieces, after being heated in the bath, must be sufficient for the intermediate stage conversion to take place, probably does not require any special reference.

With the hardening process according to the invention, there are particular advantages especially when - how z. B. machine knives - the hardness zones are arranged asymmetrically, which has so far led to increased warpage Has given rise, or if z. B. with circular knives in the joint area or in the area of the almost inevitable Overlapping in the known hardening processes, undesirable tempering or double hardening effects have occurred.

The invention is explained below on the basis of exemplary embodiments explained in more detail:

example 1

The hardening of pressure bars in the dimensions: length 1500 mm, cross section 80X 10 mm; Hardening zone on the upper edge: 20 X 2.5 mm as an example for elongated workpieces was carried out in the following way. The workpieces were placed in a hot bath and, after reaching the hot bath temperature specified for the respective material, clamped in a receiving device located in the bath, as can be seen from the schematic sectional views according to FIGS. 1 and 2. In the transverse or longitudinal section while the hot bath 1 and the workpiece is located in the receiving device 4 with the hardening zone 2 la as well as the above to the workpiece surface movably disposed parallel inductor 3 is illustrated. For austenitizing, the hardening zone was inductively brought to the hardening temperature in the feed process (with a feed speed of about 5 cm / sec). The workpieces were then left in the bath during the holding time and finally cooled down to room temperature in still air. The details on this are summarized in Table 1 below, samples 1, 3, 4 and 5 indicating hot bath hardening, while samples 2 and 6 relate to an intermediate stage conversion. The chemical composition of the steels is given in Table 2.

Tabel

l'robe no. stole Austenitizing Hot bath Hold time in Hardness HRc temperature temperature Warm bath 1 100 MnCrW4 900 ⁰ C 230 "C 3 min. 64 2 100 MnCrW4 900 ⁰ C 32O ° C 30 min. 56 3 X 210 Cr12 1020 ° C 250-C 3 min. 62 4th X 210 Cr 12 1020X 400 C 10 min. 61 5 56 NiCrMoV7 900 "C 250 C 3 min. 58 H 56 NiCrMoW 900 "C 400 ' ¹ C 30 min. 44

Table 2

Mn

Cr

Ni

Mon

Fe

100 MnCrW4 0.95 X 210Crl2 2.0 56 NiCrMoV7 0.54

1.0

0.5

12.0

1.1

15th

The pressure bars hardened according to the invention exhibited during cooling even when they were placed freely a delay of max. 4 mm at room temperature, so that the straightening process can be carried out quickly and without any risk of cracking could be carried out. Depending on the material used, the holding time was Warm bath hardening 3-10 minutes and about 30-60 minutes for intermediate stage conversion.

Example 2

The hardening of circular knives with an outer diameter of 250 mm and a thickness of 6 mm was similar to that already described in a warm-0.6

0.1
0.1

0.6

rest
rest
rest

bath carried out in which the knife body was mounted vertically and axially rotatable. The inductor was in this case a little above the bath surface or directly above that which only barely protrudes from it Fixed knife edge. The austenitization was accordingly carried out during the rotational movement of the knife body in the bath after setting the required bath temperature or after the Temperature equalization made, then this temperature maintained the holding time and finally the knife is cooled in still air. The circular knives produced in this way showed excellent properties and also pointed to the joints or overlap points that are unavoidable in the course of the rotary movement equally good hardness values.

1 sheet of drawings

Claims (2)

Patent claims: 1. Process for the partial hardening of workpieces, characterized in that the workpieces in a hot bath on about the intended transformation temperature corresponding temperature heated or at this Temperature are maintained that then the zones intended for hardening to the hardening temperature and leave the workpieces in the hot bath at least until the temperature equals after which the cooling to room temperature is carried out in air. 2. The method according to claim 1, characterized in that the heating to hardening temperature takes place inductively.