JP5104819B2 - Low temperature welding brazing for rail bonds - Google Patents

Description

  The present invention relates to a low-temperature welding brazing for rail bonding that connects a steel rail and a steel rail to establish electrical continuity.

Railroad tracks consist of ballasts, sleepers, steel rails (simply called rails), etc. The rails not only serve as guides to guide and advance the vehicle carriage, but also return. It also serves as an electrical conductor that transmits line current, instruction signal current for switching operation display and point switching, control signal current for ATS, and the like.
By the way, since rails of a rail thermally expand due to the heat of summer, there is a gap between the rail and rail joints by the amount of thermal expansion. Therefore, the rail is electrically cut off at this joint, and the aforementioned various signal currents and return currents are interrupted. For this reason, the rail and the rail are connected via a rail bond across the joint, and at this time, the rail bond and the rail are joined by a low-temperature welding brazing (hereinafter referred to as “brazing”) to achieve electrical conduction. I'm taking it.

  Here, the “rail bond” is a bundle of a plurality of copper wires, and both ends thereof are bound by brass fittings called terminals. By electrically connecting each terminal of the rail bond and the rail by soldering, the rail and the rail sandwiching the joint are electrically connected. Rail bond specifications are defined in JIS E 3601.

  On the other hand, the connection between the rail and the rail bond (hereinafter simply referred to as “rail bond connection”) is not simply an electrical connection. Since it is added to the bonding surface, particularly the bonding surface between the terminal and the rail, a bonding strength strong against vibration is required.

  In addition, when the railway vehicle passes, vibration in the vertical direction is generated in the rail, so that a strong shear strength in the vertical direction is required for the joint surface between the rail and the rail bond. Furthermore, in track maintenance work for ballast tracks, rail bonds are stepped on by sleepers with sleepers, or are caught by a pickaxe during track maintenance work to smooth crushed stones, so they will be used for joining rails to rail bonds. Are required to have excellent bonding properties, particularly high shear strength against strong impacts.

Furthermore, since the rail bonds are connected with the train stopped, each brazing must be done in a short working time of a few minutes.
Conventionally, brazing that can be bonded at a low temperature has been used for bonding rail bonds. Brazing the rail to the rail bond, fix the rail bond (for example: terminal size: 60X20 mm) to the rail side with a special jig, apply the rod-shaped brazing to the connection point, and melt the rod-shaped brazing with the gas burner A method is used in which the rails and the rail bonds are connected by filling the interface gaps of the connecting portions with wax. This build-up welding is to increase the bonding strength by allowing a sufficient amount of brazing to exist at the bonding interface.

It is said that a solder used for joining this rail bond is suitable to have a melting temperature (liquidus temperature) of 260 ° C. or less on the premise of a heating operation with a gas burner or the like.
There are brazing alloys disclosed in Patent Document 1 and Patent Document 2 that have been put to practical use as conventional rail-bonding brazes, but both of them contain cadmium as an alloy component, so that an alternative is required today. ing.
Patent Document 3 discloses a rail-bond solder alloy composed of Ag: 0.5 to 2% by mass, Zn: 7 to 15% by mass, and remaining Sn.

Japanese Patent Publication No.31-862 JP 61-154788 A JP-A-8-267270

  As a means for metallicly connecting the rail and the rail bond, welding, hard brazing, or the like that has electrical continuity and has sufficiently high bonding strength can be considered. However, methods such as welding and brazing cause the rail to be heated at the same time as the rail's guaranteed temperature range of 800 ° C or higher, and the rail body is annealed to weaken the mechanical strength, or the rail is thermally strained. Adverse effects such as causing Therefore, the soldering temperature that does not affect the rails is preferably 300 ° C. or lower and the brazing liquidus temperature is 260 ° C. or lower.

  As shown in Patent Document 1 and Patent Document 2, those that have been put into practical use as conventional rail bond solders are Sn-Zn-Cd type. Since the brazing alloy of this system has a liquidus temperature of 260 ° C. or less, there is no thermal effect on the rail during soldering. However, all of these conventional rail bond waxes have a problem of containing harmful cadmium.

  The rail bond solder disclosed in Patent Document 3 does not contain cadmium, which is a harmful substance, but the solder overflows from the gap between the jig that sandwiches the rail and the rail bond during the welding operation of the rail and the rail bond. It was easy to drop and fall on the sleeper or ballast. In addition, it is conceivable that after the brazing filler metal has been solidified, additional filling is considered, but such a working method is a so-called “potato soldering” working method, in which joined solders are formed in a laminated form. This is a soldering work method in which the joint strength is reduced due to the above. In addition, such a working method has a problem that the working time becomes long because the wax is solidified and then filled thereon.

  In general low-temperature brazing, the so-called eutectic composition in which the solidus temperature and the liquidus temperature are the same, or the brazing composition in which the solidus temperature and the liquidus temperature are close to each other is better. Easy to use. This is because the eutectic composition and the brazing composition similar to the eutectic can dissolve all the brazing with a small amount of heat if the brazing composition is the same system, and the solidification of the brazing is performed quickly.

  However, the connection work between the rail and the rail bond is often performed at night because the train is stopped, and brazing work is performed in an open-air environment, so a simple instrument such as a gas burner is used for a short time. The work can be carried out in a special environment, such as the work must be completed. For this reason, it depends largely on the skill of track maintenance workers.If a wax with a brazing composition that is close to the eutectic composition or the eutectic is used, the wax will fall during the filling operation. When heating was interrupted to prevent dropping or dropping of the wax, it was not possible to prevent the filled wax from solidifying first and then forming a layer of the filled solder to become a so-called solder.

  Moreover, in recent years, track maintenance workers have also entered a transition period from experienced baby boomers, and there are an increasing number of track maintenance workers with little experience, and there is a problem that some workers cannot perform complete rail bond joining work. It was. Accordingly, there is a need for a solder that can be safely joined even if such an operator joins the rail bond, and that can be brazed with a stable quality.

The problem of the present invention is that it does not contain harmful cadmium and lead at all, and not only does it have a thermal effect on the rail during soldering, but also allows safe rail bond joining work regardless of the operator's experience, It is to provide a brazing capable of stable quality brazing.
Since recent railways have been speeded up and diamonds have been made denser, the torsion and vibration applied to the rails have increased, and a strong force has been applied to the rail bond. In addition, there is a demand for brazing with higher shear strength, and this tendency is increasingly strong, and the required properties are becoming increasingly severe.

  Accordingly, a further object of the present invention is to provide a low-temperature welding brazing that can be used for rail bonds of high-speed railways in recent years and has a strong shear force required for rail bond joining. is there.

  The present inventors have learned that the above-mentioned problems of the rail bond brazing operation using the conventional brazing are caused by the closeness of the solidus temperature and the liquidus temperature, and The solder used to connect the rail and the rail bond has a difference between the solidus temperature and the liquidus temperature of 30 ° C or more. It overflows from the gap between the sandwiched jigs and does not fall on the sleeper or ballast. Also, the previously melted solder solidifies and becomes a so-called "potato solder" where the wax is layered. Without finding out, the present inventors have found that the rail bond can be thickened and completed the present invention.

  The present invention is a low temperature welding brazing used for joining a steel rail and a signal cable binding terminal, wherein the solidus temperature is 200 ° C. or lower, the liquidus temperature is 260 ° C. or lower, and the solidus temperature The low-temperature welding brazing for rail bonds is characterized in that the difference between the liquidus temperature and the liquidus temperature is 30 ° C. or more.

  Here, the temperature at which melting starts when the temperature is raised is the solidus temperature, and the temperature at which the metal completely changes to a liquid when the temperature is raised is the liquidus temperature. These are called melting temperatures.

  The wax according to the present invention has been developed to solve the above-mentioned problems of the prior art, and since the solidus temperature and the liquidus temperature are separated by 30 ° C. or more, the wax is in a semi-molten state. Due to the wide area, wax fluidity is poor. Therefore, the heated and melted brazing during the welding operation between the rail and the rail bond does not overflow from the gap between the jigs sandwiching the rail and the rail bond, and does not fall on the sleeper or the ballast.

  According to the present invention, a rail having a composition of Zn: 11 to 15% by mass, Bi: 1 to 5% by mass, and the balance: Sn is used for rail bond connection, thereby joining the rail bond terminal and the rail. It was found that a joint having particularly excellent shear strength was obtained.

  The solder alloy disclosed in Japanese Examined Patent Publication No. 3-28274 is used as a solder for joining an inner wire and a base of a control cable for automobiles, and is thick as a so-called “potato soldering”. Whether overlay soldering is possible is unclear, and in fact, the wax of the present invention is not disclosed for rail bonding and as a specific composition example. Further, the shear strength is not subject to evaluation.

  Since the rail bond solder of the present invention does not contain cadmium or lead at all, there is no concern about toxicity due to heavy metals, and the difference between the solidus temperature and the liquidus temperature is 30 ° C. or more. During the welding operation of the rail and rail bond, the wax overflows from the gap between the jig that sandwiched the rail and rail bond, and does not fall on the sleeper or ballast, but the previously melted wax solidifies. As a result, it is possible to thicken the rail bond junction without overlapping the wax in layers. Therefore, even if it is not an experienced worker, it is possible to braze with a safe and stable quality regardless of who performs the rail bond joining work.

It is explanatory drawing of joining of a rail and a rail bond. FIGS. 2A and 2B are schematic explanatory views of rail bonds in good working condition. It is a photograph of the good rail bond connection part of the working state of No. 1 of Example 1. It is a photograph figure of the rail bond connection part with a bad working state of No. 1 of a comparative example. It can be seen that the wax is falling on the rail. It is explanatory drawing which showed the terminal attachment position of the vibration test.

FIG. 1 is a schematic explanatory view showing a rail bond to a rail, that is, a joining state of a binding terminal of a signal cable.
The two rails 10 are fixed on the sleeper 12 with a slight gap at their ends. Because the two rails 10 are not electrically connected due to the gap, they are electrically connected by the rail bond 14. In the case of the illustrated example, two rail bonds are joined.

  Each rail bond 14 is provided at both ends of a plurality of copper wire bundles 16 constituting the signal cable, a metal fitting 18 for binding the copper wire bundles, and supports the metal fittings 18 and constitutes a brazed surface with the rail. And the terminal 20 to be configured. The terminal 20 constitutes a bundling terminal for a signal cable composed of a plurality of copper wire bundles, and is made of copper and itself has a good brazing property. Hereinafter, the binding terminal of the signal cable is simply referred to as “terminal”.

  Brazing the rail 10 and the rail bond 14 includes preheating the rail, fixing the rail bond terminal to the rail with a jig, filling the gap between the rail bond terminal and the rail with molten solder, and removing the jig. , Do by.

In addition, after fixing the rail 10 and the rail bond 14 with a jig (not shown), the metal fitting 18 is putty-packed and melted by heating, but overflows from the gap between the rail and the rail bond. Do not flow toward the wire bundle.
Rail bond bonding needs to be performed outdoors in a short time, and usually in a bad environment such as at night. Since the rail is also fixed at the brazing position at that time, the brazing posture also has no degree of freedom. Conventionally, the molten solder is not sufficiently filled, and the strength is insufficient, or the molten wax may leak from the lower end of the rail bond terminal. All of these fields have been solved by the skill of skilled workers. However, according to the present invention, in the case of the same brazing conditions, the molten brazing can hold the semi-molten state longer than the conventional one, so that it can be stirred in the semi-molten state if necessary without overflowing. The above-mentioned gap can be easily filled with a sufficient amount of molten solder, and the amount of brazing at the joint can be increased (thick build-up).

Next, after the rail bond 14 is brazed to the rail 10, a schematic explanatory view showing a peeling surface obtained by peeling the rail and the brazing surface is shown in FIG. 2. FIG. 2A is a front view thereof, and FIG. 2B is a partially enlarged sectional view. The same reference numerals as those in FIG. 1 denote the same members.
From FIG. 2A, it can be seen that the hatched portion 22 indicates a brazed portion, and the braze is uniformly attached to the entire back surface of the terminal 20. FIG. 2 (b) is an explanatory view schematically showing a partially enlarged cross section of the brazed portion at the peripheral edge of the terminal 20, and a peeling surface 24 showing a joint surface with the rail and an edge 25 of the brazed portion 22. It is clear that there is no leakage of the molten brazing during brazing. In the drawing, the black thick line indicates the outline of the terminal 20.

  Thus, according to the present invention, since the difference between the solidus temperature and the liquidus temperature is as large as 30 ° C. or more, the solid-liquid coexistence time from the melting of the wax to solidification can be increased, The gap is filled quickly and does not become “potato solder”, and since the liquidus temperature is 260 ° C. or less, there is no leakage.

In the present invention, the liquidus temperature is set to 260 ° C. or less in order to make the brazing temperature in the field as low as possible and to prevent the rail from being heated to a high temperature. This is preferably 250 ° C. or lower. The reason why the solidus temperature is 200 ° C. or lower is to make the difference from the liquidus temperature 30 ° C. or higher, and preferably 190 ° C. or lower.
In the present invention, the upper limit of the difference between the solidus temperature and the liquidus temperature is not particularly specified, but generally does not exceed 100 ° C. for brazing alloys. Considering the liquidus temperature, the temperature difference between the solidus temperature and the liquidus temperature is preferably 30 ° C. or higher and 90 ° C. or lower.
The composition of the wax according to the present invention, in which the solidus temperature is 200 ° C. or less, the liquidus temperature is 260 ° C. or less, and the difference between the solidus temperature and the liquidus temperature is 30 ° C. or more is Zn Is 11 to 15% by mass, Bi is 1 to 5% by mass, and the balance is Sn. In the composition of Sn—Zn—Bi in this range, the solidus temperature is 200 ° C. or less, the liquidus temperature is 260 ° C. or less, and the difference between the solidus temperature and the liquidus temperature is 30 ° C. or more. The condition can be met. In the composition of Sn—Zn—Bi in this range, the shearing force of the wax is 39.2 KN or more, preferably 40.8 KN or more, and it has a durability of 1000 minutes or more in the vibration test.

Examples of compositions in which the solidus temperature of the present invention is 200 ° C. or lower, the liquidus temperature is 260 ° C. or lower, and the difference between the solidus temperature and the liquidus temperature is 30 ° C. or higher are described above. In addition to the composition examples and the examples described later, the following compositions are exemplified.
(1) Zn is 13% by mass, Bi is 3% by mass, In is 2% by mass, the balance is Sn,
(2) Zn is 14 mass%, Bi is 2 mass%, Ag is 0.5 mass%, the balance is Sn,
(3) Zn is 13% by mass, Bi is 3% by mass, Ni, Cu, Sb and the like total 1.0% by mass or less, the remaining Sn
(4) Zn is 10 mass%, Sb is 2 mass%, the balance is Sn,
According to a preferred embodiment of the present invention, a rail bond terminal and a rail are further obtained by using a solder having a composition of Zn: 11 to 15% by mass, Bi: 1 to 5% by mass, and balance: Sn for rail bond connection. A joint having particularly excellent shear strength at the joint is obtained.
The reason why the preferable alloy composition of the braze used in the present invention is defined as described above is as follows. Here, “%” is “% by mass” unless otherwise specified.
If Zn is less than 11%, the required strength cannot be ensured. If it exceeds 15%, the liquidus temperature rises and exceeds 260 ° C. A more preferable range is 12 to 14%.
If Bi is less than 1%, the liquidus temperature and solidus temperature cannot be lowered sufficiently in the Sn-Zn-Bi composition, and if Bi exceeds 6%, the shear strength is secured. It is not possible. A more preferable range is 2 to 4%.

If necessary, one or more of Ag, In, Ni, Cu, Sb and the like may be added to the above brazing composition in order to improve the mechanical strength of the joint. Street.
Ag: 0.5% or less is added, but if it exceeds this, the liquidus temperature may increase.
In: 2% or less is blended, but if it exceeds that, it may become brittle due to coexistence with Bi.
Ni, Cu, Sb: At least one kind is added in a total amount of 1.0% or less.

  Even in a composition in which these mechanical strength improving elements are blended at the above-described ratio, the difference between the solidus temperature and the liquidus temperature is 30 ° C. or more within the composition range of the present invention. The phase line temperature is 260 ° C. or lower and the solidus temperature is 200 ° C. or lower.

Waxes having the respective brazing compositions shown in Table 1 were cast into rods having a size of 10.0 × 5.0 × 400 mm to produce brazing materials as test materials for Examples and Comparative Examples.
Next, the 50N rail specified in JIS E1101 and E1120 and the CLB type rail bond specified in JIS E3601 were welded using each brazing.
The brazing method in this example was performed as follows.
(1) The rail was preheated with a gas burner.
(2) Flux was applied to the surface of the preheated rail, and then each braze was heated with a gas burner to make contact with the welded portion of the rail to preliminarily plate the rail covering the rail surface.
(3) The rail bond terminal was aligned with the rail on which the brazed portion was pre-plated, and the end surface of the rail bond terminal and the pre-plated portion of the rail were adhered and fixed using a dedicated jig.
(4) Putty was put on the copper wire side of the rail bond so that the wax would not overflow from the copper wire side of the rail bond.
(5) The wax was melted by heating with a gas burner, and filled in the gap between the rails and the dedicated jig that fixed the rail bond.
(6) After the wax is completely melted in the gap between the rail and the special jig to which the rail bond is fixed, the molten wax in the gap between the terminal and the rail is stirred, and the gap is sufficiently filled with the wax. Brazing was completed with the solidification of the brazing.
In this example, each test brazing was used to braze up to three places on one rail.
Workability was judged by confirming whether or not the wax fell down during melting. The workability of the wax that did not fall during melting of the wax was evaluated as “good” (good), and the solder that dropped during melting of the wax was rated as “poor” (impossible). The results are summarized in Table 1.

  In Table 1, “Inferior durability” in the remarks column of the comparative example 3 is a result of a shear test and a vibration test described later, as a result of joint strength that is insufficient for today's high-speed railway applications. Is satisfactory, and can be sufficiently applied to conventional applications.

  FIG. 3 is a photograph of a good rail bond connection part in the working state of Example No. 1 in Table 1. It can be seen that a sufficient amount of brazing has been applied and that the bonding is sufficient. A bulge in the upper braze indicates that a sufficient amount of molten braze has been supplied.

  On the other hand, FIG. 4 is a photograph of the rail bond connecting portion when the working state of Comparative Example No. 1 in Table 1 is poor. It can be seen that the molten wax leaked downward from the gap between the rail and the terminal. This is because the difference between the solidus temperature and the liquidus temperature is as small as 18 ° C. As soon as the wax melts, the liquidus temperature is exceeded, and the molten wax becomes highly fluid. This is because the molten wax has flowed down from between the jigs for fixing.

A shear test and a vibration test were performed on the brazed portions where the brazing was performed in Example 1. The results are shown in Table 2.
Test Method for Shear Test (1) A 300 N long 50 N rail was placed on the base of the Amsler universal testing machine so that the brazed terminal portion was hit from above.
(2) A load was applied to the brazed terminal portion from above with an Amsler universal testing machine and the shearing load force was measured.
Test Method for Vibration Test (1) A 50N rail was firmly attached to the base with a fastening spring, and the rail and rail bond were brazed as shown in FIG. As shown in the figure, the left and right rails were fixed on the sleeper, and three binding terminals were brazed in accordance with the present invention. The numbers in the figure indicate dimensions (unit: mm).
At each rail end, a flea with a 26mmφ tip is attached to each rail end, and the rail is constantly vibrated by a 50-horsepower compressor, causing the brazed part to break and drop off. The time (minutes) to do was measured.

  The results of the shear test and vibration test are shown in Table 2.

From the results shown in Tables 1 and 2, it can be seen that the brazing of the present invention can be operated with peace of mind because the brazing of the rail and the rail bond does not drop during the brazing operation. Furthermore, the brazing material of the present invention has good results in the shearing test and vibration test, indicating that it can be brazed with high reliability.

Claims (5)

  A low-temperature welding brazing used for joining a steel rail and a signal cable binding terminal, wherein the solidus temperature is 200 ° C. or lower and the liquidus temperature is 260 ° C. or lower. Low temperature welding brazing for rail bonds, characterized in that the temperature difference is 30 ° C. or more.   The low-temperature welding solder for rail bonds according to claim 1, wherein the low-temperature welding solder is Cd-free.   The low-temperature welding brazing for rail bonds according to claim 1 or 2, wherein the low-temperature welding brazing has a composition of Zn: 11 to 15 mass%, Bi: 1 to 5 mass%, and the balance: Sn. The low-temperature welding solder for rail bonds according to claim 3, wherein the composition further contains at least one of the following components.
Ag: 0.2 to 0.5% by mass,
In: 1 to 2% by mass,
Ni, Cu, Sb: At least one kind, in total, 0.3 to 1% by mass.   In the method of fixing the signal cable binding terminal to the steel rail and then melting the low temperature welding brazing in the gap between the steel rail and the binding terminal to build up the rail bond connection, the low temperature welding brazing As described above, a low-temperature welding solder for rail bonds having a solidus temperature of 200 ° C. or lower, a liquidus temperature of 260 ° C. or lower, and a difference between the solidus temperature and the liquidus temperature of 30 ° C. or higher is used. The rail bond connection method.