DE3809786A1 - Method for the removal of rolling defects in the rolling of tool steels of high Brinell hardness - Google Patents

Abstract

The invention makes it possible to roll problematic steel grades - tool steels of high Brinell hardness - on modern light-section or rod mills.

Description

Patent description: With newer fine rolling mills - wire mills - that one have continuous Waiz flow is about a number a certain material start from a rolling stand to an end cross-section deformed, for example from 140 mm to 5 mm; being about high rolling speed of the rolling stock and falling rolling material temperatures, which already in the middle of the rolling process, particularly strong deformation loads occur, which can be checked, which lead to surface cracks.

A way out that is being attempted here is difficult because of the high Roll throughput speeds determine the level of performance, therefore not from can be reduced, and on the other hand the increase in the initial rolling temperatures is not possible because then the hardening temperature of the rolled material can be reached those that also lead to surface cracks during rolling.

For these reasons, including the lack of better practices tried to roll out such steel grades on older rolling mills because here discontinuous with less deformation load and intermediate heat treatments necessary rolling conditions can be maintained.

This circumstance - the current state of the art in the rolling of above-mentioned steel qualities - leads, on the one hand, to the considerable cost burden indicated by the fact, on the other hand, that one only has to operate older rolling mills for such qualities, which requires more organization and additional space requirements . A technical emergency that urges for better procedures so that steel grades with high Bri nell hardness can be rolled out more easily on modern wire mills!

For some time now, the modern wire mills have had many considerations accounts for the advantageous performance for tool steels high Brinell hardness can be used, which unfortunately has so far been unsuccessful there is.

The possible solution to this problem is: A heat treatment within the continuous rolling process of modern wire mills !; just how?

Here the idea of the invention begins to write a such heat treatment be by at a specific site - approximately in the middle of the kontinuier handy rolling process - this heat treatment is possible. Firstly, because the rolling temperature is already in the lower temperature range, and on the other hand there are already considerable temperature differences between the material core and its outer layer, which is known to lead to material stresses during further rolling, so that heat treatment helps to eliminate causes of material defects at this specific point!

For this necessary heat treatment, a Roll-up and roll-off device installed within the continuous rolling process,  so that the rolled material can be unrolled into a compact bundle.

A process that is known about so-called reels in the rolling mill and not Ge subject of the invention; for the same reason it is not the subject of this Invention can be that here already partially through the heat of the material bundle temperature compensation between the material core and its outer layer he follows. This process also does not provide a sufficient patent basis, because the rolling temperature drops further, which in turn reduces the rolling ability of the named steel qualities is reduced. The latter illustrates the need for heat treatment if here is an optimal solution for Improvement in troubleshooting should be sought.

After this clarification, the actual description of the method for realizing the patent idea follows: by the roll-up and roll-off device with refractory masses - including stones - receiving a highly heatable rolling material contact surface; and in addition the roll-up and roll-off device is provided with a cover, likewise lined fire-proof and heatable.

In this way, both parts can be heated very high - approx. 1200 ° C -, which leads to the fact that not only the above is rolled up when the rolling material is rolled up described temperature compensation take place more intensely, but also the Material rolling temperature can be increased further via convection and thus also the deformability of the steel qualities mentioned above.

To clarify the patent idea and its procedure, can again To be summarized: That the reel for bundling rolled material alien is known, a limited temperature adjustment between Material core and its outer layer due to the inherent heat of the material bundle; it is also known that heat treatments for tool steels with high Brinell harden improve the roll formability.

However, it is still unknown that the heat treatment described above is internal half of the continuous rolling process of modern wire mills via heatable and unrolling devices and can be made possible without disruptive disability, to improve the roll formability of the above steel grades to be able to. Such a heat treatment is state-of-the-art a novelty in technology!

It should also be noted that the heating of the named parts - parts with refractory linings - can be carried out using electrical resistance heating and other types of heating. It is important that, depending on the type of heating, a more or less strong protective gas atmosphere for decarburization protection for the rolled material must be sought during the heat treatment.

Claims (3)

1. A method for eliminating rolling material defects when rolling alloyed tool steels with high Brinell hardnesses, characterized in that heat treatments within this process are made possible in the continuous rolling process of modern fine rolling mills via heatable winding and unwinding devices. 2. Claim according to claim 1, characterized in that known Reeling and unwinding devices from the rolling mill area through additional Liche heating devices for heat treatments in continuous Rolling sequence can be used. 3. Claim according to claim 1 and 2, characterized in that be Known roll-up and roll-off devices with heated covers to be equipped for heat treatment in the continuous rolling process to be able to be used.