JPS6161507B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a billet heater that includes a hollow cylindrical heating coil and heats a billet conveyed inside the coil by electrolytic induction.

This type of billet heater is widely used for heating materials for forging. In this case, it becomes imperative to protect the heating coil by some means against the heat from the billet, which ultimately reaches a temperature of approximately 1250°C. A common protective measure of this kind is to line the inner surface of the heating coil with a monolithic refractory material. However, the inner surface of the lining is constantly exposed to high temperatures due to the heat from the billet during operation of the billet heater, and rapid heating and cooling are repeated frequently, so over a long period of time, the refractory material that makes up the lining deteriorates, causing damage and cracks. etc. In this case, it is strongly required that the lining be configured so that the refractory material can be safely and reliably peeled off from the heating coil and replaced with a new refractory material without damaging the insulation of the heating coil.

In conventional lining construction techniques, for example, as shown in FIGS. 1 and 2, a non-magnetic support 3 is used.
a and 3b in a non-metallic coil box 2, and after performing predetermined taping with glass mica tape and glass tape, the inner surface of the heating coil 1 impregnated with fire-resistant varnish is coated with castable alumina (Al ₂ O ₃ ) type monolithic refractory material 4 is applied to cover the entire surface. This method is relatively time-consuming, and since the insulation of the heating coil 1 and the refractory material 4 are in close contact with each other, when replacing the refractory material 4, only the refractory material can be peeled off without damaging the insulation of the heating coil 1. This is very difficult and there is often a risk of destroying the insulation of the heating coil 1 and eventually having to replace the heating coil itself.

As another protective means, a method is known in which the outer surface of a hollow cylindrical shaped refractory material is provided with the necessary insulation and a heating coil is directly wound thereon (not shown). Although this method has the advantage of being relatively simple and constructing the heating coil and its internal refractory lining at the same time, it is also true that in this case the refractory hollow cylinder is replaced without compromising the insulation of the heating coil. above is impossible.

In any case, it is difficult to protect the insulation of the heating coil and replace the refractory material at the same time using conventional protection methods, and since replacing the refractory material requires a lot of man-hours, it is extremely disadvantageous in terms of maintenance. You can't escape certain things.

In view of the above-mentioned drawbacks, the present invention provides a highly reliable billet heater in which the formation and disassembly of the refractory layer on the inner surface of the heating coil can be performed extremely easily, and the insulation of the heating coil is hardly damaged during disassembly. The purpose is to provide.

According to the present invention, the above-mentioned object is to provide the above-mentioned billet heater, in which a hollow cylinder made of a refractory material is disposed coaxially with the heating coil and inside the heating coil, and a powdered refractory material is placed between the hollow cylinder and the heating coil. This is achieved by dense filling.

Next, details of the present invention will be explained based on embodiments shown in the drawings.

In FIGS. 3 and 4, the heating coil 1, which has been impregnated with heat-resistant varnish after being taped with glass mica tape and glass tape, is attached to non-magnetic supports 3a and 3b arranged around its outer periphery. Therefore, it is held in a coil box 2 made of a heat-resistant non-metallic material such as asbestos lumber. A hollow cylinder 5 made of a refractory material is arranged coaxially inside the heating coil 1, and a powdered refractory material 6 is placed between the heating coil 1 and the hollow cylinder 5 using the dry method of induction furnace construction. The relative positions of the heating coil 1 and the hollow cylinder 6 are fixed by densely filling the heating coil 1 with a known vibrator or stamping fork. In particular, the refractory material 6 is molded by adding a binder to the vicinity of both end faces. Thereafter, a skid rail 8 is provided inside the hollow cylinder 5. The billet 7 is fed into the heating coil 1 from one end by a conveying device (not shown), and is passed over the skid rail 8 to the heating coil 1.
While being conveyed in the axial direction of the heating coil 1, it is heated to a predetermined temperature and taken out from the other end of the heating coil 1.

In the configuration of FIGS. 1 and 2, the hollow cylinder 5
It has sufficient thermal strength against the billet temperature (approximately 1250℃) and can withstand thermal shock caused by frequent repeated rapid heating and cooling, and has low thermal conductivity to protect the insulation of the heating coil. It is necessary that the material has a low coefficient of thermal expansion. As this type of material, silicon nitride (Si ₃ N ₄ )-based or high alumina (Al ₂ O ₃ )-based ceramic products are particularly suitable, as they have excellent high-temperature strength and thermal shock resistance.

The powdered refractory material filled between the heating coil 1 and the hollow cylinder 5 also has excellent high-temperature strength and thermal shock resistance, and in particular has low thermal conductivity to protect the insulation of the heating coil from high temperatures. Preference is given to amorphous powder refractory materials, such as fine powders of silica (SiO ₂ ), alumina (Al ₂ O ₃ ).

In the structure of the refractory layer on the inner surface of the heating coil 1 of the present invention, the heating coil 1 is filled with a powdery refractory material to fix the relative position of the heating coil 1 and the hollow cylinder 5, so if necessary, the heating coil 1 and the hollow cylinder 5 can be easily separated and dismantled, so the disassembly work is extremely easy, and the insulation of the heating coil 1 is hardly damaged by the disassembly work.

Furthermore, a hollow cylinder 5 and a powdered refractory material 6 for filling
Both are dry materials and do not contain moisture, and no water is used to fill the powdered refractory material, so the effort for drying after forming the refractory layer on the inner surface of the heating coil 1 can be saved. Since no special pouring form is required, the formation of the refractory layer is simple and can be done with a small number of man-hours, making it very economical.

As explained above, the present invention is a billet heater that is equipped with a hollow cylindrical heating coil and heats a billet conveyed inside the billet by electromagnetic induction, in which a hollow cylinder made of a refractory material is provided inside the heating coil coaxially with the billet. By arranging the hollow cylinder and the heating coil, and densely filling the space between the hollow cylinder and the heating coil with a powdered refractory material, an inner refractory layer is formed to protect the heating coil, and the heating coil is separated and dismantled for repair. This can be carried out extremely easily, and the insulation of the heating coil is hardly damaged when the refractory layer is separated and dismantled, which has the effect of significantly reducing man-hours and costs in maintaining the billet heater.

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal and cross-sectional views, respectively, showing the configuration of the heating coil and the inner fireproof layer for insulation protection of a conventional billet heater, and FIGS. 3 and 4 are views of the billet heater of the present invention. FIG. 2 shows a longitudinal cross-sectional view and a cross-sectional view, respectively, showing the configuration of the heating coil and the inner fireproof layer for insulation protection. 1... Heating coil, 5... Hollow cylinder, 6... Powdered refractory material, 7... Billet.

Claims (1)

[Scope of Claims] 1. A billet heater that is equipped with a hollow cylindrical heating coil and heats a billet conveyed inside the heating coil by electromagnetic induction, in which a hollow cylinder made of a refractory material is arranged coaxially with the heating coil and inside the billet heater. death,
A billet heater characterized in that a powdered refractory material is tightly filled between the hollow cylinder and the heating coil. 2. The billet heater according to claim 1, wherein the hollow cylinder is a silicon nitride (Si ₃ N ₄ )-based or high alumina (Al ₂ O ₃ )-based ceramic product.