JPS63310919A - Method and equipment for heating rail - Google Patents

Abstract

PURPOSE:To uniformly heat a rail by brief heating and to obtain a rail with less variance of toughness by initially heating the whole rail, and then heating the rail head while thermally insulating at least the rail bottom between the bottom and the stem. CONSTITUTION:A rail 1 is introduced into a heating furnace 2 from an input side 3, and moved on a skid rail 6 formed with a fixed skid 4 and a movable skid 5 toward an extraction port 7. Meantime, the whole rail is heated to a specified temp. during the movement of the rail 1 in the furnace 2 with the temp. of the rail bottom 15 easy to heat as a reference. The wholly heated rail 1 is then moved into a tunnel furnace 8 by a pusher, etc., through the extraction port 7. The head 12 of the rail passing through a heating chamber 9 in the furnace 2 is heated by the combustion gas of a burner 11, and the bottom 15 of the rail passing through a heat insulating chamber 19 is thermally insulated by a heat insulating material 10. As a result, the rail can be uniformly heated by brief heating. In addition, symbol 14 in the figure shows the rail stem.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rail heating method and equipment for heating a rail for heat treatment.

[Conventional technology]

In a treatment method in which a rail is heated from pearlite (P) to austenite (1) and then accelerated cooled to make it high in strength, hardness, and toughness, the toughness is as follows: 1. Since it greatly depends on the V grain size during heating, uneven heating of different parts of the rail causes uneven toughness, and overheating causes a decrease in toughness.

Therefore, when trying to obtain a rail with high toughness, the rail must be heated so that the head, abdomen, and bottom of the rail have a uniform temperature. However, due to the shape of the rail, the abdomen and bottom of the rail Because it has the characteristic of being heated more easily than the head, if you set the furnace temperature higher than the specified heating temperature and heat the head so that it reaches the specified heating temperature in a short time, the abdomen and bottom will exceed the upper limit of allowable heating temperature. It becomes a result. It is well known that when heating a steel material to be heated in a heating furnace, if heating is difficult depending on the part of the material to be heated, it is sufficient to increase the time in the furnace at a predetermined heating temperature (
JP-A No. 61-58228 B. The same goes for rails; conventionally, the furnace temperature is set to a predetermined heating temperature, and the rail temperature is slowed down by lengthening the furnace length or slowing down the conveyance speed of the rail in the furnace to lengthen the heating time. It was heating up as it rose.

[Problem that the invention seeks to solve]

However, with the above-mentioned conventional technology, when heating the rail, it is necessary to slowly raise the temperature of the rail, which increases the time required for heating, resulting in poor heat treatment efficiency.In addition, in order to increase heat treatment efficiency, the length of the furnace must be increased. Therefore, there was a problem in that the required space was large and a large amount of equipment cost was required. In order to avoid such problems, if the rail is rapidly heated in a furnace with a short furnace length, the temperature will vary widely, and therefore the toughness of each part of the rail will vary widely, making it impossible to obtain a good product. It is an object of the present invention to solve the problems of the prior art as described above and to provide a method and equipment that can uniformly heat a rail in a short time.

Means for Solving Problem C] The present invention is characterized by a method in heating the rail, first heating the entire rail, and then heating the rail head while insulating and keeping at least the bottom of the rail bottom and abdomen warm. In addition, a heating chamber installed to cover the rail head and a heating chamber installed to cover the bottom of the rail are integrated into the heating furnace that heats the entire rail used directly for carrying out the method. It is characterized by a rail heating facility equipped with a tunnel furnace consisting of a combination of

[For production]

According to the method of the present invention, the entire rail is heated first, then the rail head, which is difficult to heat, is forcibly heated, and at least the bottom of the rail, which is easy to heat, is insulated and kept warm, so each part of the rail is heated. The final heating temperature of the parts can be made uniform.

[Embodiments of the invention]

An embodiment of the heating equipment used directly in the method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic plan view of the heating equipment. The rail 1 is charged from the entrance side 3 of the heating furnace 2, and is moved toward the extraction lower on a skid rail 6 composed of a fixed skid 4 and a movable skid 5 disposed inside the heating furnace 2 in the direction of the large arrow. Moving. As shown in FIG. 2, the entire rail 1 is heated to a predetermined heating temperature while being moved in this heating furnace. In this case, the temperature at the bottom of the rail, which is easily heated, is taken as a reference. After the entire rail 1 is heated, it is then passed through the extraction port by a butcher or the like to the tunnel furnace 8.
will be moved to Here, rail 1 is processed tree by tree.

The structure of the tunnel furnace 8 consists of a heating chamber 9 configured to cover the top of the rail, as shown in the cross-sectional view of FIG. It is integrally combined with a heat preservation room 18 made of wood 10. The heating chamber 9 is equipped with a gas Φ burner 11 on its side wall, and the combustion gas fed from here heats the rail head 12 and then is heated to the upper part 1 of the heating furnace.
7 or its lower part 18. The insulating chamber 19 includes at least the bottom 15 of the bottom 15 of the rail l and the abdomen 4.
It is constructed with a heat insulating material 10 so as to cover the heating chamber 9, and most of the exhaust gas from the heating chamber 9 is exhausted from the upper part 17 of the heating chamber 9, so that the bottom part 15 of the rail etc. is not overheated.

The bottom part 15 of the rail, etc., is kept warm by the exhaust gas from the lower part 18 of the heating chamber 9 and the heat insulating material lO wall without decreasing the temperature. The arrows in the figure indicate the flow of the exhaust gas.

A specific example in which the method of the present invention was carried out using heating equipment as shown in FIG. 1 will be shown below.

[Example 1] A rail having a chemical composition shown in Table 1 was charged into a heating furnace at a temperature of 550° C. at the center part 13 of the rail head as shown in FIG. 4, and then heat-treated in a tunnel furnace. Accelerated cooling.

Table 1 (Note) The remainder includes unavoidable impurities. Table 2 shows the temperature distribution over time of each part of the rail in the heating furnace and tunnel furnace, and the Charpy impact value (Kg, m) that represents the toughness after accelerated cooling. shows.

In this case, a conventional method using only a heating furnace was used as a comparative example.

Table 2 As is clear from this table, the method of the present invention was able to shorten the rail heating time by about 40% from the conventional 1740 seconds to 1100 seconds without changing the Charpy impact value.

[Example 2] Here, a comparison is made between the method of the present invention under the same conditions as Example 1 and the conventional method under the same heating time as the method of the present invention until the final temperature distribution. The results are shown in Table 3.

As is clear from Table 3, when heating for 1100 seconds using the conventional method, the difference between the maximum and minimum temperatures of each part of the rail was 58°C.
The difference in Charpy impact value between the highest and lowest values is 0.5Kg, m, whereas in the method of the present invention, the difference is 28℃ and 0.3K, respectively.
g, m and tt, and the present invention can reduce variations in the toughness of the rail.

〔Effect of the invention〕

According to the method of the present invention and its heating equipment, the whole rail is first heated based on the bottom part of the rail that is easy to heat, and then at least the bottom part of the rail is kept warm, and the head part of the rail which is difficult to heat is forcibly heated. Since the final temperature of each part of the rail can be made uniform, the heating time of the rail can be shortened and variations in toughness can be reduced, making this invention highly effective industrially.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the heating equipment of the present invention, FIG. 2 is a vertical side view taken along the line n-II in FIG. 1, and FIG.
A sectional view taken along the line ■-■ in the figure, and FIG. 4 are explanatory views of each part of the rail. 1...Rail, 2...Heating furnace, 3...Inlet side, 4...
...Fixed skid, 5. Movable skid, 6. Skid rail, 7. Outlet, 8. Tunnel furnace,
9...Heating chamber, 10...Insulating material, 11...Gas burner, 12...Rail head, l3...Rail head center, 14...Rail abdomen, 15... Rail bottom, 16...Rail foot, 17...Heating chamber top, 18
...Heating chamber lower part, 19... Warming room.

Claims (1)

[Claims] 1. A rail characterized in that when heating the rail, first the entire rail is heated, and then the rail head is heated while at least the bottom of the rail bottom and abdomen is insulated and kept warm. Heating method. 2. A tunnel furnace is attached to the heating furnace that heats the entire rail, which is an integral combination of a heating chamber installed to cover the rail head and a heating chamber installed to cover the bottom of the rail. Features: Rail heating equipment.