JPH0677867B2 - Weld crossing and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to a welded crossing for a railroad turnout excellent in wear resistance and durability and a method for manufacturing the same.

(Prior art and its problems) As crossings for railway turnouts, manganese crossings made of high manganese cast steel and welded crossings made of carbon steel are used. The former crossings have excellent wear resistance, toughness, and durability. Although it has the advantage of excellent
Since it is difficult to weld the front and rear ends and it is necessary to connect them using a joint plate or the like, there is a drawback that a joint broken line portion is generated.

On the other hand, the latter welding crossing has the advantage that there is no joint broken line part because it can weld the front and rear ends, but in the case of hot-electrode welding (covered arc, MAG welding, etc.), consider the meltability. , Medium carbon steel with normal carbon content (C: 0.33-0.
38%), it does not exhibit sufficient strength even by heat treatment, and alloys such as Cr, Mo, B are added to improve hardenability during heat treatment. Compared with heat treated materials of carbon steel and high manganese steel, there is a drawback that wear and settling easily occur near the transfer portion.

In addition, since it is difficult to weld the narrow head portion of the front part of the nose rail, there is the economical disadvantage that a special section rail with a large abdominal thickness must be formed by rolling or forging and the processed material must be used. is there.

In any case, in the current situation where speed improvement and noise reduction of trains are desired, in addition to eliminating joint broken lines as much as possible in the branch, aim to improve wear resistance and durability of used members However, neither conventional manganese crossings nor weld crossings are satisfactory.

(Object of the invention) The present invention uses a welding crossing, and aims to improve its wear resistance and durability, which are its drawbacks, while utilizing the advantage of such a welding crossing that there is no joint missing line portion with the front and rear ordinary rails. It is an object of the present invention to provide an improved weld crossing and a manufacturing method thereof.

(Points of Intention and Structure of the Invention) In the present invention, the cause of the lack of durability of the conventional welding crossing is 0.33, which is about 1/2 of that of a normal rail, considering the weldability.
The carbon alloy steel rail as low as 0.38% was used to improve the wear resistance and toughness by heat treatment (quenching and tempering), but it is still not sufficient. Because it is manufactured by welding,
It was made paying attention to the fact that the head weld portion of the nose rail, which is easily subjected to impact load, remains in a softened state, and the first configuration thereof is a pair of wing rails. Welding crossings that sandwich a pair of nose rails between
C: a high carbon steel rail material containing 0.70 to 0.82%, the heads of a pair of nose rails are welded to each other directly or with a common metal wire having substantially the same chemical composition as the rail material, Weld crossing is based on the idea that the entire head has a nose rail tread that contains uniform fine pearlite.

The high carbon steel rail material used in the present invention may be the 50N or 60K rail material used as a material for NHH rails.

Further, the common metal wire having substantially the same chemical composition as the rail material, for example, C: 0.70 ~ 0.82%, Si: 0.15 ~ 0.30%, Mn:
It is preferable to use one having a composition containing 0.70 to 1.10%.

Since the welded part is intended to improve the wear resistance of the nose rail tread, at least the heads of a pair of nose rails are made directly from each other by base metal, or from a metal alloy containing almost the same chemical composition as the rail material. Welding may be performed using a wire, and other joints may be welded using a wire of 80K or 100K grade, but the base may be welded directly between the base materials or using a common metal wire.

Normally, the nose rail is welded to the head and the base, and the abdomen is hollow (Figs. 5 and 6). However, a pair of nose rails, for example, a symmetrical rail having the same cross-sectional shape as the normal rail, are used. When used, it is preferable to arrange the rails in parallel and weld the abdomen in the front part to make it solid (see FIG. 4) because the structural strength of the rail increases. Such an abdominal solid form is a desirable form even if it has a special cross-sectional shape as shown in FIG. 7 when a symmetrical one having the same cross-sectional shape is used.

The pair of welded nose rails are subjected to heat treatment to form a substantially uniform nose rail tread containing fine pearlite.
After heating to a quenching temperature of ℃ or more, fountain quenching is performed to once create a quenched martensite structure, and subsequently tempering at about 550 to 580 ° C (Q / T treatment)
After heating the rail head to a quenching temperature of about 800 ° C. or higher, it is preferable to slowly cool the slack quench (hereinafter also referred to as SQ) heat treatment method.

Here, in JIS heat treatment terminology, `` SQ means quenching that quenches from the austenitizing temperature range in the process of hardening the steel and cools at a speed slightly slower than the critical cooling rate of each steel, in this case, the steel is It does not completely harden, but in addition to martensite, it produces a mixed structure of bainite and fine pearlite. "However, the S / Q heat treatment method of the present invention controls the cooling rate to form a fine pearlite structure. It is essential to make

Specifically, the rail, at least the rail head, Ac ₃ points (800
(° C) or higher, after heating the material rail to austenite transformation and then slowly cooling along the SQ cooling curve in Fig. 8, the SQ cooling curve intersects the CCT diagram Ps.
The pearlite transformation starts at the point and the pearlite transformation is completed at the Pf point, and only a fine pearlite structure can be generated. In FIG. 8, CCT is a continuous cooling transformation curve, and Ms is a martensite transformation starting point.

On the other hand, the second structure of the present invention provides a method for manufacturing the above-mentioned weld crossing, and in order to manufacture the weld crossing having the above-mentioned first structure of the present invention,
(1) A welding rod made of a coil material can be manufactured by welding a welding rod made of the same material as the high carbon rail material whose rail material contains C = 0.70 to 0.82%, and (2) welding the high carbon rail with the welding rod,
The deposited metal and the heat-affected zone may have the same properties as the base metal rail, and (3) welding work can be performed efficiently, for example, automatic welding is possible, and (4) after welding the nose rail, S・ Since it is required that the Q heat treatment method is applicable, "When manufacturing a welded crossing in which a pair of nose rails are welded and sandwiched between a pair of wing rails, a pair of wing rails and a pair of nose rails are used. C: Manufactured using high carbon steel rail material containing 0.70 to 0.82%, at least the heads of a pair of nose rails are welded by the narrow groove welding method, and then heat treated by the slack quench method to heat the entire head. Is a fine pearlite ”.

In the method of the present invention, the narrow groove welding method that can be used is an electron beam welding method in which base materials are directly welded to each other, and a TI metal wire having almost the same chemical composition as the rail material is used.
G welding method can be mentioned.

Further, the pair of nose rails are usually welded at the head and the base to form the abdomen in a hollow shape (see FIGS. 5 and 6).
(Refer to the drawings), in the present invention, a pair of symmetrical nose rails are welded instead of welding long and short nose rails. It is preferable that the abdomen is formed by welding even from the base portion to the abdomen to make the abdomen solid (see FIGS. 4 and 7), and the abdomen is hollow from the middle to the rear.

When the fixed crossing is manufactured by integrating the wing rail and the nose rail, the normal side portion 10a and the base portion 10b are welded and integrated (see FIGS. 6 and 7), but only the base portion 10b is used. The structure can be simplified if the welding crossings are manufactured integrally by welding (see FIGS. 4 and 5).

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

(Embodiment) FIG. 1 is a plan view showing the whole of the welding crossing 1 manufactured by the manufacturing method according to the present invention. The pair of wing rails 10, 10 are symmetrical to each other as shown in FIG. A pair of nose rails 11 having the same cross-sectional shape as a normal rail are back-to-back welded, heat-treated, and then sandwiched by welding.

FIG. 4 is a sectional view taken along the line AA, and FIG. 5 is a sectional view taken along the line BB. A pair of symmetrical nose rails 11, 11 are, as shown in FIG. Is welded with a narrow groove using a common metal wire, and is welded with a narrow groove using a 80 or 100K class wire from the base portion 11b to the abdomen 11c,
The abdomen 11c is solid, while the head 1 from the middle to the back.
1a is welded with a narrow groove using a common metal wire, and the base portion 11b is welded with a narrow groove using an 80 or 100K class wire, and the abdomen 11c is hollow.

On the other hand, the welded nose rails 11, 11 are welded and integrated only at the wing rails 10, 10 located on both sides thereof and the base portion 10b to form a fixed crossing.

The welded crossing 1 is welded at its front and rear ends so that there is no joint broken line portion with the normal rail to form a branching device.

Hereinafter, a manufacturing example of the weld crossing will be specifically described. The above wing rail 10 and nose rail 11 are NHH
A high carbon steel for rails (carbon content 0.70 to 0.82% by weight) was used, and a wire having a chemical composition almost the same as that of the NHH high carbon steel for rails was used as a welding wire.

The groove between the pair of nose rails was set to about 8 to 10 mm, the base metal was preheated to about 400 ° C, and welded by the narrow groove TIG welding method.

With such a welding method, it is possible to perform automatic welding using a welding rod having substantially the same material as the NHH rail, and the tread surface of the nose rail has the same weld metal and heat-affected zone as the base metal rail. become.

Next, the V-shaped nose rail (see FIG. 2) manufactured by the above method is heat-treated as follows.

Put the welded nose rail in a preheating furnace and heat it to about 500 ° C, then heat the head of the V-shaped nose rail to about 800 ° C with a continuous heat treatment device, and further inject compressed air to cool it by S / Q. Gently cool along the curve to produce a fine pearlite structure.

After the heat treatment of the head of the V-shaped nose rail is completed, the nose rail and the wing rail are integrated by welding the base portion. In this case, the nose rail and the wing rail may be connected by using a spacer and bolts.

(Effect of the invention) As is apparent from the above description, according to the present invention, in a welding crossing in which a pair of nose rails are welded and sandwiched between a pair of wing rails, the rail material is C: 0.70 to
A high carbon steel rail material containing 0.82%, at least a pair of nose rail heads are welded with a common metal wire that has almost the same chemical composition as the rail material, and the heat treatment results in a substantially uniform nose rail tread containing fine pearlite. Since it is formed, it is possible to improve wear resistance and durability, which are disadvantages of the welding crossing.

Further, according to the present invention, in manufacturing a welded crossing in which a pair of nose rails is sandwiched between a pair of wing rails, the pair of wing rails and the pair of nose rails have a high C: 0.70 to 0.82% content. It is manufactured using carbon steel rail material, at least the heads of a pair of nose rails are welded in a narrow groove directly or with a gold wire, and then heat treated by the slack quench method, so high carbon steel rails are used. It is possible to inexpensively manufacture a welded crossing having excellent wear resistance and durability.

Further, since a pair of symmetrical nose rails are welded to form a V-shaped nose rail with a narrow groove, a material having a normal rail cross-sectional shape can be used as the nose rail. Can be planned.

As a result, not only can the joint broken line portion be eliminated in the branch device, but the durability of the used member can be improved,
The noise in the turnout and maintenance can be reduced, and the train passing speed on the reference line side of the turnout can be improved. Therefore, in the present situation where the improvement of the train speed is a problem, its significance is immeasurable.

[Brief description of drawings]

FIG. 1 is a plan view showing an entire welding crossing 1 manufactured by a manufacturing method according to the present invention, and FIG. 2 is a plan view of a V-shaped nose rail in which a pair of symmetrical nose rails are welded, and FIG. Is a central longitudinal sectional view thereof, and FIG. 4 is A of FIG.
A sectional view taken along line A, FIG. 5 is a sectional view taken along line BB, and FIGS. 6 and 7 show the welding mode of a pair of nose rails having a special sectional shape. It is a diagram for explaining the Q heat treatment method. 1 ... Weld crossing, 10 ... Wing rail, 11 ...
… Nose rail

Claims (6)

[Claims] 1. A welded crossing comprising a pair of nose rails sandwiched between a pair of wing rails, wherein the rail material is a high carbon steel rail material containing C: 0.70 to 0.82%. The head part is welded to the base materials directly or with a common metal wire having almost the same chemical composition as the rail material, and the whole head part forms a nose rail tread surface containing homogeneous fine pearlite. Weld crossing to do. 2. The weld crossing according to claim 1, wherein the pair of nose rails are symmetrically welded using a material having the same sectional shape as that of the normal rails. 3. The welded crossing according to claim 1 or 2, wherein a pair of symmetrical nose rails are arranged in parallel, and the front part is welded to the abdomen to be solid. 4. When manufacturing a welded crossing in which a pair of nose rails are welded and sandwiched between a pair of wing rails, the pair of wing rails and the pair of nose rails are C: 0.70.
Manufactured using high carbon steel rail material containing ~ 0.82%,
A method for manufacturing a welded crossing, characterized in that at least the heads of a pair of nose rails are welded by a narrow groove welding method and then heat-treated by a slack quench method to make the entire heads fine pearlite. 5. A pair of nose rails are arranged in parallel using a material having the same cross-sectional shape as a normal rail, and a front part forms a narrow groove not only in the head part but also from the base part to the abdomen. The manufacturing method according to the above-mentioned item 1, wherein welding is performed even on the abdomen to form a solid. 6. The manufacturing method according to claim 1, wherein when the wing rail and the nose rail are integrally fixed crossing, they are integrated by welding only the base portion.