JPH01127117A - Winding method for hot roller steel strip - Google Patents

Abstract

PURPOSE:To prevent the quality of a hot rolled steel sheet from deteriorating on account of quick cooling at its winding end part and the yield of the hot rolled sheet from lowering by fitting a thermal insulating sleeve to a mandrel in a winder for hot rolled steel sheet, heating it in advance to a specified temperature and then winding the hot rolled sheet. CONSTITUTION:When a rolled steel heated at a high temperature immediately after hot rolling is wound by a winder, the end part of the hot rolled sheet is brought into direct contact with the mandrel of the winder, cooled quickly, deteriorated in quality and the part is cut off and accordingly the yield of the hot rolled sheet is lowered. In this case, on the outer surface of the mandrel 6 is provided with a sleeve 1 consisting of the inside of an iron sheet cylinder 2 and insulating material 4 such as asbestos, etc., and the outside of an iron sheet cylinder 3, and the sleeve 1 is heated by an induction heating device 7 near a winding temperature of the hot rolled sheet, then, the heating device 7 is removed and the hot rolled sheet is wound. In this case, the thickness of the outside iron sheet cylinder 3 is made thicker than that of the hot rolled sheet or thicker than 3mm to prevent the quality deterioration based on the quick cooling of the point part to wind the hot rolled sheet.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a winding belt that suppresses the cooling of a hot rolled steel strip (hot rolled steel strip) by attaching a heat insulating sleeve to the mandrel of a winder. Relating to a winding method.

(Prior Art) The leading end portion, ie, the inner winding portion, of a hot rolled steel strip is in direct contact with the mandrel of a winding machine. For this reason, the tip of the steel strip is rapidly cooled, and the deteriorated tip, which causes quality deterioration, is sheared off in the next process. This causes a decrease in yield. On the other hand, mandrels are susceptible to deformation and damage as a result of rapid heat transfer, and to prevent this, mandrels are generally cooled from within.

Methods have already been proposed to overcome such conventional methods of winding hot-rolled steel strips.

For example, Japanese Patent Publication No. Sho 62-19244 proposes a winding method in which a required length of the strip at the beginning of winding is co-wound with a vapor-like heat insulating material to prevent direct contact between the steel strip and the mandrel.

However, with this method, it is extremely difficult to send out the heat insulating material in line with the tip position of the steel strip at the start of winding the steel strip, and a paper-like heat insulating material with appropriate strength is relatively expensive.

In addition, the heat insulating material is susceptible to water, etc., and is disposable, which increases the cost and makes it impractical.

On the other hand, Japanese Patent Application Laid-Open No. 57-47525 discloses that a sleeve made of a double iron cylinder with a heat insulating material sandwiched between the cylinders is attached to the mandrel of a winding machine to reduce the temperature at the tip of the wound steel strip. We are proposing a method to suppress this.

(Problems to be Solved by the Invention) The method disclosed in Japanese Patent Application Laid-Open No. 57-47525 involves winding up a mandrel with a heat insulating sleeve, and the tip of the band is cooled by direct contact with the mandrel. to prevent This method further reduces heat transfer to the mandrel.

Further, even after winding is completed, the sleeve is integrated with the coil and removed, thereby preventing heat dissipation due to loosening of the inner winding portion.

However, the surface of the heat insulating sleeve is at room temperature before winding is started.

Therefore, especially when winding a Tlifm band, cooling is not sufficiently suppressed, leading to a decline in the quality of the tip.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to overcome the problems of the conventional method of mounting an insulating sleeve on a mandrel to suppress cooling of the steel strip. That is, an object of the present invention is to provide a method for winding a hot-rolled strip that can suppress a sudden drop in temperature of the tip of the steel strip in contact with the sleeve outer cylinder at the start of winding and improve the quality of the tip. shall be.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the inventor of the present invention has conducted extensive research and has come up with the idea of preheating the heat insulating sleeve from the outside to a temperature close to the steel plate winding temperature. Furthermore, at this time, the thickness of the cylinder made of iron plate on the outside of the sleeve necessary to ensure the effect of preheating was determined, and the present invention was completed.

Thus, the gist of the present invention is to provide a method for winding a steel strip in which a heat-insulating sleeve is attached to a mandrel of a winding machine for a hot-rolled strip to suppress cooling of the steel strip. The thickness of the outer iron plate cylinder of the double cylinders that sandwich the material is greater than the thickness of the steel strip to be wound, and the iron plate cylinder is preheated to a temperature approximately equal to the winding temperature of the steel strip. This is a method for winding hot rolled steel strip.

When preheating is performed by induction heating, it is preferable that the thickness of the outer cylinder made of iron plate is 3 times 1 ml.

The preheating temperature is best set to the target coiling temperature of the steel strip, but there is usually a range of coiling temperatures. Therefore, preheat to at least the lower limit of the winding temperature. For example, if the winding temperature is predicted to be 650 to 550°C,
The sleeve preheating temperature is 550°C.

(Function) In the present invention, heat is accumulated in the sleeve in advance. In order to accumulate sufficient heat, the steel strip needs to be as thick as the rolled steel strip (or at least as thick as the rolled steel strip).In the case of induction heating, if the steel strip is not thick enough, the frequency of the AC power source needs to be increased.
It is difficult to raise the temperature, so in the case of induction heating, 3IllI1
It is preferable to have a thickness of 1 or more.

The heat insulating sleeve has a heat insulating material sandwiched between the inner and outer cylinders. Therefore, the rise in temperature of the inner surface of the sleeve during winding is very small and the mandrel is not overheated and damaged.

(Example) Next, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view of a heat-insulating sleeve used in carrying out the method of the invention, and FIG. 2 is an axial cross-sectional view thereof, mounted on a mandrel and preheated with an induction heating device. FIG. 3 is a diagram schematically showing the state.

Here, an embodiment of the present invention in which preheating is performed by induction heating will be described.

The heat insulating sleeve 1 is constructed by interposing a heat insulating material 4 between an inner cylinder 2 made of iron plate and an outer cylinder 3 made of iron plate. The inner and outer cylinders 2.3 are fixed and supported to each other by reinforcements 5.

Examples of materials and dimensions for each part of the sleeve 1 are as follows: Inner cylinder: 3ff 111 thickness, steel plate Outer cylinder: 6II 11 thickness, steel plate Insulation material: 1011II + thickness, asbestos (SiOz: 50%
, CaO: 50%) Sleeve length: 1800+a++ Sleeve outer diameter: 800IIl111 Preheating of the heat insulating sleeve 1 is performed as follows.

As shown in FIG. 2, a heat insulating sleeve 1 is attached to a mandrel 6 of a winder (down coiler), and the outer diameter of the mandrel 6 is expanded and fixed. Next, a hollow cylindrical induction heating coil 7 is fitted around the outer periphery of the sleeve 1, and a power source 8 (2KHz
Single-phase AC (500 V, 600 A) is applied and moved from side to side to heat the outer cylinder 3 of the sleeve. When the surface temperature of the sleeve reaches 600°C from room temperature (20°C), remove the heating coil 7 and immediately start winding the hot rolled steel strip (1.6 mmg, target winding temperature 600°C to 650°C). Start.

A thermometer is installed near the sleeve surface to control the preheating temperature.

In the above embodiment, an induction heating device is used for preheating, but an electric heater or a gas burner may also be used for preheating. However, in either case, it is necessary to preheat the sleeve to a temperature close to the temperature at which the outer surface of the sleeve is rolled up.

In addition, a plurality of devices for preheating the heat insulating sleeve will be installed in consideration of its heating capacity and the location of the winding device.

The preheating temperature is set at the lower limit of the temperature range by predicting the next winding temperature. Therefore, the heat source and structure of the preheating device may be a general heating device, but it is preferable to measure the temperature of the outer surface of the heat insulating sleeve and automatically control the temperature to near that temperature based on information about the next winding temperature.

(Effects of the Invention) FIG. 3 shows the weave transition of the tip of the steel strip and the inner surface of the sleeve in the embodiment of the present invention and in the conventional case (where a heat insulating sleeve is simply attached and no preheating is performed).

As can be seen from FIG. 3, when the preheating sleeve according to the present invention is used, the temperature a at the tip of the steel strip in contact with the outer surface of the sleeve and the temperature a at the inner surface of the sleeve in contact with the mandrel change very slowly. On the other hand, when using a conventional heat-insulating sleeve without preheating, the temperatures a" (tip of the steel strip) and b" (inner surface of the sleeve) change drastically, especially at the tip of the steel strip immediately after the start of winding. The part temperature a° has fallen sharply. On the other hand, in the winding method of the present invention, the temperature a at the tip of the band gradually decreases from the start X to the end Y of winding. As described above, as a result of using the heat insulating sleeve preheated to near the coiling temperature according to the present invention, the temperature drop at the tip of the steel strip becomes extremely small, making it possible to self-anneal the entire length of the steel strip after coiling.

This effect can be explained more specifically as follows.

1. When using a sleeve made of 6 mm thick high carbon steel strip and without preheating, it was necessary to cut down the tip by about 51 I. On the other hand, in the case of winding according to the method of the above-mentioned embodiment, only 500 mm of the tip was cut down due to poor shape, and there was no need to cut down due to poor material (hardness), resulting in improved yield.

As described above, according to the present invention, by attaching the heat insulating sleeve whose outer surface is preheated to a temperature approximately equal to the winding temperature to the mandrel immediately before winding, it is possible to use the steel plate as a good product from the leading edge. This results in a significant yield improvement effect.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the heat insulating sleeve used in carrying out the method of the present invention, taken along line 1--1 in FIG. A diagram schematically showing a winding machine mandrel and an induction heating device; and FIG. 3 show the temperature transition of the belt tip and sleeve inner surface when winding is performed according to the method of the present invention and the conventional method. This is a graph showing. 1: Insulation sleeve.゛ 2: Inner cylinder made of iron plate 3: Outer cylinder made of iron plate 4: Insulation material 5: Reinforcement material 6: Mandrel 7: Induction heating device 8: Source

Claims (2)

[Claims] (1) In a steel strip winding method in which a heat-insulating sleeve is attached to a mandrel of a winding machine for hot-rolled steel strip to suppress cooling of the steel strip, a double cylinder sandwiching a heat insulating material constituting the heat-insulating sleeve. The thickness of the outer iron plate cylinder is equal to or greater than the thickness of the steel strip to be wound, and the iron plate cylinder is preheated to a temperature approximately equal to the coiling temperature of the steel strip. Winding method. (2) The method for winding a hot rolled steel strip according to claim 1, wherein the preheating is performed by induction heating, and the thickness of the cylinder made of iron plate is 3 mm or more.