JPS6030726B2 - Rail head heat treatment method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to heat treatment of rails, and more specifically, the present invention relates to heat treatment of rails, and more specifically, a rail row formed by connecting the ends of the rails with a connecting member is passed through a heating zone, and then passed through a cooling zone. In continuously heat-treating the head of the rail by passing the rail, the head of the rail near the connection part (
This article relates to a method and device for heat treatment of the rail head for the purpose of uniformizing the shape of the hardened layer (uniform structure and hardness) between the end head (hereinafter referred to as the end head) and other heads. be.

With the recent development of transportation, cars are being required to be able to withstand increasingly high loads and high speeds.

For this reason, there is an increasing demand for rails that are heat-treated to have high hardness and high wear resistance, rather than rails that are used as hot-rolled. For this reason, the rail head is heated to a surface temperature of about 700 to 95 mm, then quenched and competitively tempered to make tempered martensite or mirror-restored behnite (sorbite), or to a surface temperature of 700 to 700 mm. After being heated to about 1200℃, it is subjected to slack quenching to create a fine pearlite structure, thereby meeting the demand for rails with high hardness and high wear resistance. This is the current situation.

In such heat treatment (quenching and tempering, slack quenching) of the rail head, the rails are not treated one by one intermittently, but the ends of the rails are connected with a connecting member. This rail row is heated at a constant rate by a heating zone (induction coil or flame furnace).
A predetermined hardness and structure are obtained in the rail head by passing the rail through a cooling zone and then through a tempering furnace (if tempering is required). However, in the heat treatment of such rails, there has conventionally been a problem in that the shape of the competing hardened layer cannot be made uniform between the end head of the rail and the other head.

That is, since the connecting member lowers the atmospheric temperature in the furnace and absorbs the heat of the rail, the end of the rail is affected by its heat conduction and heat axis diffusion, and its competitively hardened layer The formed shape is different from the shape of the quenched hardened layer of the other heads. In particular, when gas flame heating is applied to the heating zone, the rail head is heated by the atmosphere in the furnace in the heating zone, so the shape of the quenched hardened layer of the total head is even more different from that of other heads. will be different. In addition, the first
As shown in the perspective view in the figure, an example of the result of heat treatment by passing a rail 2 whose ends are connected by a connecting member 1 through a heating zone made of gas flame heating and a cooling zone Shown in Figures A, C, and C. Second
Figure A is a diagram showing the shape of the competing hardened layer in the length direction of the seal head (in the figure, the shaded part is the partially hardened layer, and a shows the part in contact with the connecting member 1), The figure opening is A-A in Figure 2 A.
2C is a cross-sectional view taken along line BB in FIG. 2A. It is clear from the figure that the competitive hardening layer shape is not uniform along the length of the rail. For this reason, in order to obtain a uniform hardened layer shape over the entire rail head during heat treatment of the rail, for example, as described in Japanese Utility Model Publication No. 11285/1985, a gap is created between the rail and the contact surface. However, even with such a connecting member, it is still difficult to obtain a uniform hardened layer shape over the entire length of the rail head. Therefore, this invention was made in order to solve the problem mentioned above, and it involves passing a rail row formed by connecting the ends of the rails with a connecting member through a heating zone and then through a cooling zone. In the method of continuously heat-treating the head of the rail, the method includes heating the connecting portion to a predetermined temperature before entering the heating zone; and A rail head comprising a connecting member passage detection device that detects passage of a connected connecting member, and a burner provided in front of a heating zone that preheats the connecting member based on a detection signal from the detection device. It is characterized by the fact that it is a heat treatment equipment.

FIG. 3 is a schematic cross-sectional view showing one embodiment of the rail heat treatment apparatus (for obtaining Akibō sorbite on the rail head) according to the present invention.

In the figure, 3 is a drive roller for transporting the seal 2 in the direction of the arrow, 4 is a gas flame heated competition furnace (heating zone), 5 is a cooling device (water cooling zone), 6 is a tempering furnace, 7 is a receiving roller. As shown in FIGS. 3 and 4, between the drive roller 3 and the scale furnace 4, there is a connecting member passage detection device that detects when the connecting member 1' connecting the ends of the rails 2 has passed. A detection switch 8 that is turned on by mechanical contact, and a burner 9 that heats the connecting member 1' to a predetermined temperature based on a detection signal from the detection switch 8.
and are arranged. With this configuration, a rail row in which the ends of the rails 2 are brought into contact with each other by the connecting member 1',
First, the head of the rail 2 is continuously heat-treated by passing through a scale furnace 4, then through a cooling device 5, and then returning to a cold furnace. And the moving rail 2
Oribe's connecting member 1' (the tip thereof) is connected to the detection switch 8.
When it reaches the position of
is heated by the burner 9, and the connection part village 1
' is preheated to a predetermined temperature. Therefore, even if the connecting member 1' is inserted into the quenching furnace 4, it is prevented from lowering the atmospheric temperature in the furnace or absorbing the heat of the rail. A rail having a uniform curved hardened layer shape on the head in all directions is obtained. Figures 5A, 5A and 5C show an example of the result of heat treatment of a rail using the equipment shown in Figures 3 and 4 (in the figure, the shaded area is the quenched hardened layer, and a is in contact with the connecting member 1'. ). From the figure, it is clear that a substantially uniform shape of the hardened layer is obtained between the end portion and the other portions. Note that the preheating temperature of the connecting portion is preferably 600° C. or lower.

This is because if the temperature exceeds 600 degrees Celsius, the rail component material will exceed the temperature range A, and as long as this temperature does not exceed 600 degrees Celsius, it will vary depending on the size of the connecting member and the type of rail. Decide accordingly. Further, the operation of the burner 9 that preheats the connecting member may be controlled in the following manner, for example.

That is, the rail temperature, atmospheric temperature, connecting member shape coefficient, rail track type, cooling water temperature, and rail heating set temperature are input, and predetermined calculations are performed to determine the gas pressure of the burner 9 and the gas outflow time. , these may be controlled. As explained above, in the present invention, it is possible to obtain an extremely uniform shape of the hardened layer over the entire length of the head of the rail.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the connection state of the seal, Figure 2 A is a diagram showing the shape of the quenched hardened layer in the length direction of the seal head, and the opening in Figure 2 is A in Figure 2 A. - A sectional view, Figure 2 C is B in Figure 2 A
1B is a cross-sectional view, FIG. 3 is a diagram showing one embodiment of the rail heat treatment apparatus according to the present invention, FIG. 4 is a plan view of the connecting part village passage detection device and the burner, and FIG. 5A is the present invention. Figure 5 shows the shape of the quenched hardened layer in the length direction of the head of the rail heat-treated by
Figure C is a sectional view taken along the line BB in Figure 5A. DESCRIPTION OF SYMBOLS 1, 1'... Connecting member, 2... Rail, 3... Drive roller, 4... Akatsuki furnace, 5... Cooling device, 6...
- Scale furnace, 7...receiving roller, 8...detection switch, 9...burner. Hair' figure 2 figure 3 younger brother figure 4 figure ※5

Claims (1)

[Claims] 1. A rail row in which the ends of the rails are connected by connecting members is passed through a heating zone and then a cooling zone, thereby continuously cutting the heads of the rails. A method for heat treating a rail head, the method comprising: preheating the connecting member to a predetermined temperature before entering the heating zone. 2. Preheating the connecting member based on a connecting member passage detection device that detects passage of the connecting member connecting the ends of the rails, and a detection signal from the detection device provided in front of the heating zone. A heat treatment device for a rail head, comprising a burner.