JPH02200379A - Butt shielded metal arc welding method for rail - Google Patents

Abstract

PURPOSE:To improve welding work and to prevent the occurrence of weld defects by using an electrode having coating material in the limited range and performing flat welding without carrying out slag removal at a part in the head where flat multilayer welding is performed. CONSTITUTION:At the time of performing flat multilayer welding of the head 7 and foot 9, the electrode coated with coating material containing 42-55% carbonate, a 13-23% metallic fluoride, 0.5-9.5% rutile and the balance consisting of an alloy additive and a binder on the periphery of a core wire is used. Further, CaO/CaF2 is regulated in the range of 1.3-1.7 and 15-25% coating material is applied with respect to the total weight of the electrode and slag is not removed for each pass or slag is removed for more than two passes and flat multilayer welding is performed continuously. By this method, it is made possible to manufacture a welded joint without weld defects with satisfactory welding workability and the working time is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a butt covered arc welding method for rails used in railways, industrial machinery, etc.

(Conventional technology) Conventionally, rail joining methods include 7-way butt welding,
Gas pressure welding, thermite welding, sheathed welding, and the like are used. Among these welding methods, the enclosed arc continuous rod welding method, which uses a covered arc welding rod with a ■-shaped opening, and the arc welding method, which uses an X- or V-groove arc welding rod, is described in Japanese Patent Publication No. 56-4350 and [ As introduced in "Rails, Metal Materials, 1965, Vol. 5, No. 4, pp. 77-79", it has the advantage that it is possible to weld rails in a restrained state and the reliability of the joint is also high. , is often used as an on-site welding method.

Due to the purpose of rail welding, the welded joints are required to have high wear resistance and fatigue damage resistance, as well as good welding workability.Especially in on-site welding of railway rails, it is necessary to have high wear resistance and fatigue damage resistance. Due to the need to complete construction in the dark, welding time is also required to be kept as short as possible.

Conventionally, coating 7-
This welding method avoids welding defects such as slag entrainment,
This is done while ensuring stable welding rod operation and removing slag that occurs with each welding pass.

(Problem II to be Solved by the Invention) Slag removal work during covered arc welding of rails may involve attaching and detaching the welding pad, which not only increases the work burden on the welding operator. , there is a problem that the welding time becomes longer.

In order to solve this problem, if multilayer welding is performed without removing slag using a welding rod (low hydrogen coated arc welding rod) that meets JISD8016, which is conventionally used for multilayer welding, the slag will be removed. New problems arise in that stable welding is difficult because it is difficult to remelt or a large amount of slag is generated, and welding defects such as slag entrainment are likely to occur.

The present invention solves the problems in using the coated arc welding rod described in Qtj and provides a welding method for rails used in railways, industrial machinery, etc., which can ensure a good welded joint without welding defects.

(Means for Solving Problem A) The gist of the present invention is to perform Uranami welding on the sole of the rail, downward multi-layer welding on the foot, vertical upward welding on Hattori, or continuous entrainment from the abdomen to a part of the head. Close arc welding - butt covering of rails with downward multi-layer welding of the head! [7- In the welding method,
When performing downward multilayer welding on the inside of the head, excluding at least the multilayer hardfacing part on the head surface of the downward multilayer welding part, 42 to 55% carbonate and metal 7) compounds are added to the outer periphery of the core wire. 13-23
%, contains 0.5 to 9.5% rutile, the remainder consists of alloy additives, fixing agents, etc., Ca O / Ca F 2
Using a coated arc welding rod coated with a coating material having a ratio of 1.3 to 1.7 in an amount of 15 to 25% based on the total weight of the welding rod, slag generated during welding is removed after each pass. This is a butt covered arc welding method for rails, which is characterized by continuous downward multi-layer welding, with slag removed every two or more passes.

(Operation) The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example of a lamination method. First, the rail bottom 1 is welded using Uranami welding, and then the rail foot 2 is welded downward in multiple layers. At this time, slag is removed after each pass, and downward scrap welding is performed to avoid entrainment of puffballs, which is a conventional welding method. After welding of the rail foot portion 2 is completed, a pad 5 is applied and enclosed arc welding is performed in which a coated arc welding rod is continuously added from the rail 11 section to the m section -B3. After removing the slag, the rail head 94 is further welded downward in multiple layers. At this time, in the same way as for the rail foot part 2, the conventional welding method of removing slag for each pass and downward multi-layer welding is performed.Especially, in multi-layer head welding, slag is removed for each pass. At this time, it is necessary to attach and detach the pad 5.

In the present invention, the downward angle M at the rail foot 2 and the rail head 4 is
Multi-layer welding is performed continuously without removing the slag generated in each pass during f# welding, reducing the welding work burden and shortening the welding time. At this time, welding defects such as puffer entrainment do not occur. is important, and for this reason, the coating material for coated arc welding rods used for welding is required to facilitate remelting of the solidified slag generated in the previous pass during welding, and to minimize the amount of molten slag generated. .

Therefore, the reason why the welding rods used in the present invention are limited as described above will be explained.

First of all, carbonates refer to lime carbonate, barium carbonate, and magnesium carbonate, which generate CO gas to surround the core wire that is added during welding, and protect the molten pool from the atmosphere.
It is effective in preventing the occurrence of bits and blowholes, and improving 7-ring stability and slag removability. Carbonates are also effective in adjusting slag viscosity and are used as important raw materials for welding materials. Carbonates are used singly or in combination of two or more, such as lime carbonate and barium carbonate. If the amount is less than 42%, a protective tube at the tip of the welding rod will not be properly formed, leading to deterioration of the shielding effect, resulting in increased arc stability and spatter. Moreover, if it exceeds 55%, Co, t
TS is generated, the amount of spatter increases, and the amount of slag is large.
Also, the slag viscosity becomes excessive. For these reasons, the carbonate content was specified as 42-55%.

Further, metal heptafluoride refers to calcium heptafluoride, fluoride sorghum, and magnesium fluoride, and is effective in adjusting the viscosity and fluidity of slag and in producing slag. Metal heptafluoride is used singly or in combination of two or more, such as calcium fluoride and sodium heptafluoride, but if the amount is less than 13%, the slag viscosity becomes excessive, and the slag gets entangled with the tip of the welding rod, making it unstable. It is not possible to perform welding. In addition, if it exceeds 23%, the slag amount increases and at the same time the slag viscosity decreases extremely, causing the slag to wrap around the front of the welding pool and making it impossible to obtain stable welding.For these reasons, the amount of metal 7 fluoride added is reduced to 1.
It was defined as 3-23%.

Rutile maintains good slag viscosity and is highly effective in improving arc stability.However, if it is less than 0.5%, it has no effect and spatter occurs frequently, and if it exceeds 9.5%, the slag Rutile was specified as 0.5 to 9.5% because stable welding could not be achieved due to excessive viscosity and slag entangled at the tip of the welding rod.

In addition, the balance is alloy additives such as Si, Mn, Cr, and N1, and sodium silicate (N112s io 3).
and potassium silicate (K 2 S 1o-).

Furthermore, in the present invention, Cab/CaF2 in the coating material
The ratio of The relationship between the softening temperature and welding workability was investigated.

As a result, the findings shown in FIG. 2 were obtained. Here, a sample obtained by pressing the crushed coating material into a shape of 2 mm x 3 m was heated in an atmospheric furnace, and the sample melted to a size of 172 mm, which is the same as the original sample. The temperature at which the coating was applied was defined as the softening point of the coating. It can be seen that the softening point of the coating material is greatly influenced by the relationship between the ratio of CaO and C11F2 in the coating material and rutile, and as a result, the welding workability in covered arc welding is affected. That is, Cab/C in the coating material
If the aF2 ratio is less than 1.3, the viscosity of the slag will be too low, the slag will not be removed smoothly from the vicinity of the welding pool, the welding slag will get entangled with the welding rod tip, and welding workability will be poor, and the Cab/CaF2 ratio will be too low. If it exceeds 1.7, the viscosity of the welding slag increases and at the same time the amount of slag generated increases, making it impossible to perform sound welding.For these reasons,
aO/CaF2 was defined as 1.3 to 1.7.

It is necessary to apply the coating material in an amount of 15 to 25% based on the total weight of the welding rod. If the value calculated by formula (1), that is, the coverage rate, is less than 15%, a stable shielding effect cannot be obtained, and the strength of the protective tube at the tip of the welding rod, which is necessary to generate an arc, will be low, causing damage during welding. Chips fall off and stable welding cannot be achieved, and smooth application is not possible due to the thinness of the coating when manufacturing the welding rod. - If the coating ratio exceeds 25%, the amount of slag increases and the welding slag melts. Since the coating material remains on the pool and does not allow stable welding, the amount of coating material relative to the total weight of the welding rod was specified as 15 to 25%.

w Coverage rate = Rw + Fw ”oo ... (1) F
-2 Coating material weight Rw: Center M weight In the present invention, JISD8
A conventionally commercially available low-hydrogen coated arc welding rod such as No. 016 or the above-mentioned coated arc welding rod is used, and the above-mentioned coated arc welding rod is used for downward multi-M welding of legs and the like. However, in the present invention, during downward multi-layer welding using a covered arc welding rod, the rail is susceptible to cold pricking due to the chemical composition of the rail, and it is necessary to preheat or maintain the welding pass leap temperature (400 to 500°C). )is necessary. When performing multilayer welding under such conditions, it may be difficult to maintain the above temperature if slag removal is performed for each tS contact pass. For this reason, the downward multi-layer welding method, which omits the work of removing slag after each welding pass, makes it easier to maintain the temperature of the welded area and prevent cold cracks in the rail.

(*Example) Using the test rails shown in Table 1, welding was carried out using the combinations of the core wires shown in Table 2 and the compositions and coating rates of the coating materials shown in Table 3. Table 4 shows the chemical composition of the weld metal at that time, and evaluates the welding workability, presence or absence of welding defects, and welding time when downward multilayer welding is performed using these rails and welding rods. The welded parts shown in Table 5 and targeted for this evaluation are JIS
Overlay welding part of Uta table fi6 using D8016 melting rod,
1NfIls8 Tsuen9 a-X Ml continuation weld,
J [Excluding the Uranami welding part of tlO, 14 part 7 and foot part 9
This is the part where downward multi-layer welding is performed. In downward continuous multi-layer welding without slag removal using a welding rod with a limited range of coating material, welding workability is good, there are no welding defects, and welding time is short; When a welding rod with a chemical agent is used, welding is difficult in downward multi-layer welding without slag removal, and welding defects such as slag entrainment occur. In addition, welding for removing slag required installation and removal of the mold, and the welding time was about twice that of the method of the present invention.

(Effects of the Invention) As described above, the rail butt welding according to the present invention can produce a welded joint without welding defects with good welding workability, and furthermore, the welding time is shortened, and its industrial value is is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the lamination method, Fig. 2 is a diagram showing the relationship between Cab/CaF2 and the orbital point of welding slag, and Fig. 3 is a lamination diagram. 1...Rail bottom, 2...Rail foot, 3...Part of the rail head from the abdomen, 4...Rail head, 5...
- Pad, 6... Head surface, 7... Head, 8... Snout, 9... Feet, 10... Bottom.

Claims (1)

[Claims] (1) Uranami welding of the sole of the rail - downward multi-layer welding of the foot -
Upward welding of the abdomen or continuous enclosed arc welding from the abdomen to a part of the head - In the rail butt covered arc welding method that performs downward multilayer welding of the head, at least the head of the downward multilayer weld is When performing downward multi-layer welding inside the head excluding the multi-layer hardfacing part on the surface, add 42 to 55% carbonate, 13 to 23% metal fluoride, and 0.5 to 0.5 rutile on the outer periphery of the core wire. 9.5%, and the remainder consists of alloy additives, adhesives, etc.
Using a coated arc welding rod in which a coating material with an O/CaF_2 ratio in the range of 1.3 to 1.7 is applied in an amount of 15 to 25% based on the total weight of the welding rod, slag generated during welding is removed in each pass. A rail butt covering arc welding method characterized in that continuous downward multi-layer welding is performed without removing slag or after every two or more passes.