JPS5942152A - Manufacture of roll by gradient heating forging process - Google Patents

Abstract

PURPOSE:To heighten density of an outer layer and improve a mechanical property by forging a composite roll outer layer of which is made of a hard alloy and an inner layer is made of a soft alloy by heating the outer layer to a proper temperature for forging and keeping the inner layer at a lower temperature. CONSTITUTION:A composite roll is formed by cold forming a powder metal (high speed steel) on the outer periphery of a round bar. Outer periphery is enclosed with ordinary steel to prevent deformation at the time of forging, and forged by heating. At this time, the forging machine is heated rapidly by induction heating. The outer layer is heated to the proper temperature for forging and the inner layer is maintained at the low temperature. By this way, the time of forging is shortened, and the deterioration of the mechanical property of the inner layer of the roll is improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a composite roll by gradient heating forging. [Relating to a method for increasing f- and improving mechanical properties.

Conventionally, when forging a composite roll, the entire roll is placed in a heating furnace, and after the roll temperature reaches a predetermined temperature, forging is performed. According to this method, both the inner and outer layers of the roll undergo similar deformation during forging, so in order to increase the density of the outer layer, which is usually formed from powder metal, more forging is required. It is not industrially or economically advantageous.

That is, the method of forming a roll using powdered gold hw generally includes a method of pressurizing powdered gold N' at room temperature to form it, and then heating it to a suitable forging temperature for forging.
With this method, when high pressure is applied at room temperature, only about 70% of the density obtained with a conventional melting machine can be obtained. Therefore, it is required to obtain a density equivalent to that obtained by

Unfortunately, in conventional forging methods, the forging ratio has to be larger than in melting machines.

An object of the present invention is to provide a method for manufacturing rolls by gradient heating forging, which eliminates all of the problems of the above-mentioned conventional techniques and can manufacture rolls with high density without providing a large forging ratio.

The present invention provides a composite roll in which the outer layer part is made of a hard alloy and the inner layer part is made of a soft alloy. The gist of the present invention is a method for manufacturing a roll by gradient heating forging, which is characterized by:

The present invention will be explained in detail below by giving examples.

Round bar with outer diameter of 50++ on and length of 500mm (S45C material)
A composite roll was formed by cold-opening powder metal (high-speed steel, FZ-7) on the outer periphery of the roll using a rubber press method.

After forming, the outer periphery is wrapped in a plain copper plate to prevent deformation during forging, and heat forging is performed.

In the present invention, heating is preferably carried out by induction heating. For example, the forging machine is rapidly heated using a power source with a frequency of 1000 to 50 Hz, and the outer layer is heated to the appropriate temperature for forging, while the inner layer is kept at a temperature as low as possible. It is preferable to forge it while keeping it at a constant temperature.

In this example, induction heating was performed using an inductor, and the outer layer of the roll was rapidly heated to 1200 C for forging. During forging, when the temperature dropped, the same heating process was performed again, and this was repeated to perform the hot forging process.

The relationship f between the forging ratio (S) and the density ratio (%) of the composite roll obtained in this example is shown in FIG.

Further, the relationship between the forging ratio (S) and the density ratio (%) of a composite roll obtained by heating and forging the entire roll by a conventional method is also shown in FIG. 1 as a comparative example.

As is clear from FIG. 1, the method of the present invention (FIG. 1A)
According to
The desired density can be achieved, the forging time is significantly shortened, and it is extremely advantageous industrially. (In Figure 1, 100% density refers to the density when a melting machine is used.) Also, since the inner layer is kept at a low temperature, the mechanical properties of the inner layer of the roll are less likely to deteriorate than before. It can be significantly improved compared to the method. Furthermore, fMI is the only heating effective for forging.
This is extremely advantageous in terms of energy saving.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the forging ratio (S) and density (%) of composite rolls obtained by the method of the present invention and the conventional method.

Claims (1)

[Claims] 1. A composite roll having an outer layer made of a hard alloy and an inner layer made of a soft alloy, the outer layer being heated to a suitable forging temperature and the inner layer being kept at a temperature lower than the proper forging temperature. , a method for manufacturing a roll by gradient heating forging, characterized by forging. 2. The method for manufacturing a roll by gradient heating forging according to claim 1, wherein the hard alloy is high alloy steel. 3. The method for manufacturing a roll by gradient heating forging according to claim 1 or 2, wherein the soft alloy is a low alloy steel. 4. A method for manufacturing a roll by gradient heating forging according to any one of claims 1 to 3, wherein the composite roll is a powder sintered roll. 5. A method for manufacturing a roll by gradient heating forging according to any one of claims 1 to 4, characterized in that the composite roll is heated and forged by an induction heating method.