JPH10113790A - Covered electrode for cast iron and its deposited part - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the development of a welding rod with a high impact value at the deposited part of the cast iron material which is related to the wire use development of the cost iron material. SOLUTION: A condition maintaining Sharpy impact value 5kgm/cm<2> of a deposited metal whose base material is the cost iron material, which has been welded with the covered electrode of a wire rod containing at least 40 to 60% Ni except 2.0% C, 2.5% Si and 2.5% Mn, is that the depositedimetal contains 1.20 to 2.20wt.% V. By adding an adequate amount of V from a covering material or the wire rod, a part of the V is solidified in the austenitic phase of a base material, and the strength and the hardness of the deposited metal are enhanced. Further, the grain refining of an austenitic grain size is performed. And, double carbide with VC or FeC3 is formed in the greater part of it, and an outstanding increase in hardness and a remarkable increase in level of the Sharpy impact value as a result of it, are induced. By too small addition of V, the impact value does not reach a target, by an excessive addition of V, high hardness is brought, and the toughness of the deposited metal is lost. Therefore, a range balancing with a target value is limited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding rod for cast iron, and in particular, to a high strength required for a non-fastened joint system of a ductile cast iron pipe whose application range is rapidly expanding in recent years due to its lightness in pipe laying. The present invention relates to an improvement in an arc welding rod for cast iron capable of forming a welded portion having high strength and high impact resistance.

[0002]

2. Description of the Related Art Among arc welding rods for cast iron and widely used as welding materials for various levels of cast iron, including ductile cast iron, is classified as DFCNiFe in JIS-Z-3252. The components of the wire are C: 2.0%, Si: 2.5%,
It is formed based on an austenitic material containing at least Ni: 40 to 60% in addition to Mn: 2.5%. That is, Ni is a typical austenite-forming element, has the property of maintaining the γ region up to room temperature by a large amount of addition, and if applied as a wire rod for a cast iron welding rod,
Since it melts at a relatively low temperature to form the welded part of the austenitic structure, the melting temperature of the wire is high, as in other materials, and the boundary between the base material and the cast iron material is increased by rapid temperature rise and rapid cooling during welding. The risk of cracks and peeling occurring in the heat-affected zone is reduced, and a welded portion having a soft but toughness and having a certain level of cohesion with the base material can be obtained.

[0003] However, the conventional arc welding rod for cast iron, which is designed to maintain a stable arc with a generally known coating material based on this wire, simply includes a flexible intermediate layer between the cast iron and the cast iron. Apparently,
Only the cast irons were bonded to each other, and even if there was mutual interaction of metal molecules between the welded part and the boundary where the base material was in contact, it stayed in a limited range only on the surface of the boundary, Unlike the case of carbon steel and alloy steel, which melt into each other and form a specific welded structure layer, the range of solid solution of the molecule beyond the boundary is extremely limited, so the strength of the base metal It is a natural consequence of not reaching the level at which near material strength can be planned.

[0004]

However, in recent years, even in the case of arc welding rods for cast iron, cases in which considerable strength and impact resistance are required may appear depending on the mode of use. Was. For example, conventionally, when laying a water pipe buried underground, an insertion hole is inserted into the socket of the ductile cast iron pipe, and the pressing ring and the receiving flange are pressed while pressing the end face of the rubber packing inside the joint with the leg end face of the pressing ring. And the pipes were joined by bolts and nuts, but in recent years, as a non-fastening method (slip-on type: S2 type), a joining method that does not use a press wheel or bolts and nuts has been attracting attention. became. For example, in the prior art disclosed in Japanese Utility Model Laid-Open No. 4-133090 shown in FIG. 9, a lock ring groove 2 is provided around an opening end of a receiving port 1 so that a lock ring 3 is fitted therein. And a rubber ring 6 is interposed in the hollow portion between the inner surface of the receiving port and the outer peripheral surface of the insertion port to maintain the water sealing action of the joint portion. When connecting ductile cast iron pipes and laying pipes underground, workers entered into narrow excavations and relied on manual work such as fastening the press ring and receiving flange in an unnatural posture Freed from the troublesome hard work of the past,
By simply preparing and using a specific jig from the ground, the joining process can be easily completed, which is extremely advantageous in terms of improving workability and ensuring workplace safety. The basic function of this joint is that even if rocking such as an earthquake directly hits and external force acts in the direction to pull out the joint between the pipes, the lock ring of the receiving port and the insertion ring will hit and Therefore, it is considered that it is an important premise that the insertion ring is firmly fixed on the inner periphery of the cast iron pipe in order to form a seismic isolation pipe in which separation of the pipes is prevented.

[0005] In order to fix the insertion ring to the inner peripheral surface of the insertion hole as in this example, it cannot be overestimated that welding is most generally suitable. The scheme is customary. The biggest issue is the reliability of the non-fastening method unless the receiving ring and the insertion ring collide with each other to prevent the movement of both when the external force is applied in the direction that the pipes separate in an emergency such as an earthquake. Are summarized in the points where questions arise. Since the insertion ring is an annular body made of carbon steel, there is no concern in terms of strength. However, the strength of the welded portion 7 between the inner peripheral surface of the ductile cast iron pipe and the insertion ring is sufficient to guarantee the function of preventing separation. In particular, the success or failure of this method depends on whether or not impact resistance can be ensured. Conditions that sufficiently suppress the movement of the pipe and protect the function of the pipeline are taken into account from the strength and impact resistance of the ductile cast iron itself, which is the base material, and at least the tensile strength is at least 28 kgf / mm ² even from repeated physical tests, It has been concluded that a Charpy impact value (Know Notch) is a requirement of 5 kgm / cm ² . However, on the other hand, the above-mentioned Ni-Fe-based arc welding rod for cast iron specified by the conventional JIS cannot reach this level at all, and the particularly important Charpy impact value is slightly 1 to 3 kg / m2.
Only a level of about ² cm is recognized, and it is too uneasy to entrust the function under such severe use conditions,
It is undeniable that no matter how much the slip-on type method surpasses the past methods in terms of workability and workplace safety, it will remain the biggest challenge to overcome in order to implement it.

[0006] Originally, the progress of welding technology has been remarkable along with the widespread development of metal materials and the transition of various use conditions, but most of them have been accompanied by the addition of appropriate amounts of alloying elements in low and medium alloyed steels and the accompanying progress. Related technology such as heat treatment. For example, in the prior art of Japanese Patent Application Laid-Open No. 7-323392, V is multiplied by the content of the core wire and the content of the coating material as the optimum coated arc welding rod for welding 490 N / mm ² class high strength steel. Is from 0.05 to 0.25%
Including wire rods, it claims to improve the low-temperature cracking resistance characteristic of high-tensile steel. It has been long known that the addition of V is effective in preventing welding defects in low hydrogen arc welding rods. It has been known for a long time that the addition of V acts as a trapping agent for hydrogen to prevent low-temperature cracking of welds based on solid solution of hydrogen. Its remarkable effect on prevention has been confirmed by metallurgical experiments and reported at academic conferences.

In the prior art of Japanese Patent Publication No. 60-59993, rust prevention primer is applied to steel for large structures, so if welding is performed with a low-hydrogen arc welding rod, pits frequently occur and repair is performed. The problem was that it was difficult to work, and SiC, Al-M
g, MgCO3, CaF2, etc., and in some cases, present a coating material containing at least 10% by total of at least one of Ni, Cr, V, Mo, Cu, and Nb to provide deoxidation, cracking resistance, It is said that the arc breaking resistance is also at the same time.

[0008] In addition, Japanese Patent Laid-Open No. 5-161 developed mainly for 9% Cr low alloy steel and having high temperature strength and toughness.
No. 993, arc welding rod, 2.25-3% C
In all conventional techniques, such as the arc welding rod disclosed in JP-A-2-220797, which is particularly effective for r-1Mo steel, research and development was carried out so as to have a special property and a specific resistance by adding an alloying element. Report the results.

Means for obtaining the tensile strength and the Charpy impact value specified by fillet welding between the ductile cast iron tube and the steel material described above are also limited to the most appropriate component from the most suitable range among many metallic materials. Must be identified. In the end, this work can only be found through a series of trial and error focusing on the characteristics of each element by carefully reading the vast literature, but in particular ductile cast iron is the base material, which is essentially familiar with cast iron material and cracks and While encouraging the strengthening of the base of a solid welded portion where cracks do not occur, it results in a problem of how to adjust the balance between the properties of absorbing the vibration and shock by the cushioning action of the deposited graphite.

The present invention solves the above problems by systematically and systematically repeating a number of experiments. After that, the welded portion between the ductile cast iron tube and the steel material has an excellent cast iron which exceeds the physical properties of a normal base material. The purpose of the present invention is to provide an arc welding rod.

[0011]

The arc welding rod for cast iron according to the present invention comprises: C: 2.0%, Si: 2.5%, Mn:
A weld metal welded with a cast iron material as a base metal by a coated arc welding rod for cast iron made of a wire containing at least Ni: 40 to 60% in addition to 2.5%, and has a V of 1.20 to 2.20.
The present invention is characterized in that a welded portion is formed by a coated welding arc welding rod for cast iron characterized by containing by weight.

As described above, there have been many reports on various measures for improving various physical properties by adding V to a steel material or a finely divided welded portion. Many proposals are applied to trap hydrogen to prevent low-temperature welding cracks in high-strength steel,
Next, high temperature strength, or improvement in creep strength, fracture toughness, and the like continue. However, studies on high-carbon arc welding rods for cast iron are extremely rare, and no reports aiming at drastic improvements in tensile strength and Charpy impact value have been recognized to the inventor's knowledge. Therefore, while full-scale metallurgical studies are to be waited for in the future, theoretical considerations must be inferred from the data of the present invention obtained at the present time to estimate the behavior of V.

FIG. 2 is a diagram extracted from an example of an experiment in the present invention. EPMA in which the distribution along a specific test line in the tissue is counted for each of the three elements Fe, C, and V is shown.
(X-ray microanalyzer). FIG. (A) shows the distribution of iron, FIG. (B) shows the distribution of carbon at positions corresponding to the respective positions in FIG. (A), and FIG. (C) also shows the amount of vanadium distribution. Things. The organization that is the base of the measurement position is shown in FIG.
(C), FIG. (A) is an iron, FIG. (B) is a carbon, and FIG. (C) is a compositional photograph (600 times) selectively showing only the presence of vanadium as an electronic image. Each probe in FIG. 3 scans on the same straight line drawn in each of FIGS. 3A and 3B, and only the component amounts at each position are counted and displayed as waveforms in FIGS.

2 (A), 2 (B), and 2 (C), the low iron portion in FIG. 2 (A) should correspond to high carbon, whereas the diagram corresponding to this portion (FIG. 2 (A)) should correspond to high carbon. In B), a high carbon peak is observed, so that the relationship between the two components is inextricably and closely matched, and further it can be confirmed from FIG. 3A that graphite is crystallized black on the iron base. Is clearly shown, and the comparison between the two figures shows that the indications of the carbon positions match well, suggesting that the detection method is highly reliable. Next, by looking at the distribution of vanadium in FIG. 2 (C), peaks corresponding to high carbon in FIG. 2 (B) can be recognized. Conversely, all peaks of high carbon in FIG. It can be seen that the peak does not always coincide with the high vanadium peak of (a). In other words, carbon is separated into a portion that crystallizes in the form of graphite as a structure and a portion that precipitates in the matrix in the form of carbide as a structure. The relationship between the carbon content crystallized as a graphite type and the carbon content precipitated as a carbide was clarified.

On the other hand, FIG. 4 is an explanatory diagram (B) showing a structure (A) of the same sample of the present invention by an optical microscope photograph (× 400) and a position where hardness is measured by a micro Vickers. Similarly, FIG. 5 is an optical microscope photograph (A) of the prior art in which V is not added to the coating material, and an explanatory diagram (B) similarly showing the indentation of the hardness measurement. Needless to say, in both cases, the matrix is based on an austenite phase, and graphite is crystallized into carbide, gray-black lump, or rod-like portions in the matrix surrounded by wires and precipitated. Although there is a gap between the shape of graphite and the precipitated shape of carbides between the present invention and the prior art, the difference between FIG. 4 which is an example of the present invention and FIG. 5 which is a comparative example is shown numerically. The micro-Vickers hardness was measured for each matrix and carbide part, leaving a diamond-shaped indentation in FIG. The results of the measurement are shown in Table 3. When comparing the example of the present invention with a comparative example under the same condition using JIS-3252-DFC NiFe, which is the prior art, the effectiveness of V carbide clearly appears. I have. That is, in the embodiment of the present invention, the average of the micro Vickers hardness around the carbide mainly composed of VC is 2
As compared with 98, the average around the carbide mainly composed of Fe3C of the comparative example is only 225, and the average value of the base structure is only 199 in the comparative example with respect to the average of 231 in the present invention. Can be understood to be the root of the dramatic improvement in tensile strength and Charpy impact value by strengthening the matrix and forming ultra-hard carbide.

The micro Vickers hardness test suggests that the addition of an appropriate amount of V increases the strength and hardness by partially dissolving in the austenite phase of the matrix, and furthermore, the austenite grain size is determined by the behavior during heating and cooling. It is presumed that, in addition to miniaturization, most of them formed double carbide with VC or FeC3, leading to a remarkable increase in hardness and consequently to a significant increase in Charpy impact value. Fig. 6 (Sato and Nishizawa: Bulletin of the Japan Institute of Metals, 2,
1963, 10, pp. 565 to 571) show the hardness of various carbides in steel materials.
It shows that the MC type carbide has extremely high hardness along with iC. V-added high-speed steel is a product utilizing this principle, and it can be interpreted that V plays a leading role in the formation of ultra-hard carbide from the interrelationship of FIGS. 2 to 6 of the present invention. Right from metallurgical common sense.

As a method of adding V, there are a case where it is blended into the welding wire itself and a case where it is blended into the coating material. Finally, the proper structure of the welded part and the Charpy impact value and the Upper limit of blending percentage for securing tensile strength,
It is necessary to set a lower limit. FIG. 1 is a chart showing the grounds for limiting the component ranges derived from the embodiment of the present invention described later. In the development of arc welding rods for cast iron containing carbon components at least 10 times that of alloy steels for which R & D has been concentrated in the past, there is almost no prior art document that can be used effectively, and a large amount of C It goes without saying that the behavior shows a completely different structure from steel, such as graphite crystallization, so determining the upper and lower limits of components to meet the standards required for individual welded materials is the royal road to solving problems. I interpreted that. FIG. 1 denies that the measurement result of the sample is a component range under so-called limited conditions in which the strength and impact value required for welding the above-described slip-on type ductile cast iron pipe are targeted in that sense. Although it does not mean that it forms a strong welding part that is outstanding compared to the conventional technology that uses cast iron base material, it has outstanding features that can be widely applied to other structural applications. No change.

The plotting data shown in FIG.
In particular, it was constructed by combining the values picked up from Table 3 relating to the hardness and Table 4 relating to the Charpy impact value for the purpose of limiting the components. As a general rule that could be grasped by experiments, the yield of V added to the coating material is as follows. 85 to 95%, Charpy impact value (Kg
m / cm ² ) is 1.81 at the minimum, 3.63 at the maximum, and 2.5 on average
1, the Charpy impact value (Kgm / cm ² ) of Example 1 containing 1.40% by weight of the V component in the deposited metal is 5.60 at the minimum, 6.82 at the maximum, and 6.15 on average; The Charpy impact value (Kgm / cm ² ) of Example 2 containing 1.60% by weight of the V component in the deposited metal is at least 6.36, the maximum is 8.39, and the average is 7.53. The hardness of the micro Vickers of Example 1 containing 1.40% by weight of the components is at least 290 around the carbide, at most 330, and an average of 298, and at least 21 in the matrix.
2, maximum 245, average 231; hardness of micro Vickers in the prior art without V added is minimum 212, maximum 234, average 225 around carbide.
It is also picked up that the base station has a minimum of 180, a maximum of 217, and an average of 199. If evaluated for the purpose of the present invention, the greatest requirement is that the Charpy impact value (Kgm / cm ² ) be 5 or more. Therefore, the V weight% is plotted on the horizontal axis and the Charpy impact value is plotted on the vertical axis. When the V weight% that cuts off the Charpy impact value of 5 kgm / cm ² is obtained, the average value of the measured values is V: 1.0 wt%. However, considering the maximum / minimum variation, the Charpy impact value at each V value is considered. When the point at which the lowest line L plotting only the lowest value intersects the line with a Charpy impact value of 5 kgm / cm ² is determined, the result is V: 1.20% by weight. This is the lower limit of V wt% assuming the lowest case among the variations. The tensile strength was 28 kgf /
since the recorded good results exceeding mm ² far, no particular need of interest discussion, the focus may be seen to have been narrowed down to only impact resistance.

The upper limit of V weight% is determined by the hardness. As V increases, the amount of solid solution in the austenite matrix further increases, increasing the hardness of the matrix and increasing the precipitation of carbides. However, the Charpy impact value of the welded portion does not increase endlessly in proportion to this. Absent. The increase in hardness is almost proportional to the increase in wear resistance, but there is an appropriate value for the Charpy impact value, and if it exceeds the limit, it naturally appears as a negative effect. In the present invention, the setting of the upper limit is based on the hardness of the base, because it is based on general principles known in metallurgy as a lesson from other fields, typically alloy steel research results. Determined that, to the extent that the target Charpy impact value was secured, securing toughness was the essence of sound weld formation,
Specifically, the micro Vickers hardness of the matrix was set to 250 as the upper limit, and it was read from FIG. 1 that V corresponding to this hardness was equivalent to V: 2.20% by weight. In this case as well, only the highest value of hardness was connected for each component of V, and the highest line H among the variations was selected as a factor for determining the range to absorb the variation of the sample. The line also almost converged at V: 2.20% by weight = Hv: 250 almost in the same manner, and the upper limit was double-proven.

The component range of V weight% in the deposited metal is determined. This V may be added to the coating rod of the arc welding rod or may be added to the welding wire itself. Alternatively, they may be added back from the two and summed up, respectively, and determined back from the yield so as to be contained in the deposited metal in the above range. The following is the basis of the calculation in the case of adding to the coating material, and Fe-V means powdered ferrovanadium that can be evenly mixed in the coating material. V weight% = (Fe-V / coating material) × (coating material / wire) ×
(V / Fe-V) × 0.85 {(Fe-V / coating) = V wt% / ((coating / wire) × (V / Fe-V) × 0.85] where 0.85 In order to ensure completeness by adopting the lower yield of V, (V / Fe-V) is provided as a standard product of each manufacturer at 50% by weight. (Coating material / wire material) has its own know-how based on the technology and experience of the welding rod maker, but the V weight% of the welded portion is 1.
Since it was specified as 20 to 2.20, (Fe-V / coating material) = 1.20 to 2.20 / [(coating material / wire material) x (V / Fe-V) x 0.85] ... The principle of adding from the coating material is to use a coating material in a range in which ... is satisfied. Here, the ratio of (covering material / wire) is 3
If it is limited to 0% by weight, (Fe-V / coating material) = 1.20 to 2.20 / 0.30
× 0.50 × 0.85 = 9.4 to 17.2% by weight, and Fe-V to be added to the coating material is calculated to be in the range of 9.0 to 17% by weight in consideration of variation in yield. Is done. However, it goes without saying that this addition amount is governed and varied by the conditions for forming the coating material when the arc welding rod for cast iron is manufactured.

It is, of course, possible to include V to be added to the weld metal not from the coating material but from the wire itself, and it is even an effective means if the wire can be mass-produced. In this case, V is added to the molten metal,
Unlike alloy steel, high-Ni cast iron contains a large amount of high-C, high-Si, high-Mn and high-affinity components with high oxygen, and also a large amount of Ni, which is a stable non-oxidizing austenitic phase-forming element. From this, it is understood that the depletion due to oxidation hardly needs to be considered, and the yield is 90% or more. However, if a lot of wire melting lots are not put together to some extent, small-quantity production of various types is economically disadvantageous, so it is considered that there are many cases where the addition by the coating material takes precedence, but the addition amount in this case is Based on the calculation formula, the amount of added Fe-V = V wt% × dissolved wire amount / [(V / Fe-V) × 0.90]... In order to be within .20, V to be blended into the wire should be 1.30 to 2.40.
% By weight, and if the Fe-V content is 50%, the wire may be dissolved and scoured by mixing twice the amount.
Naturally, it is possible to incorporate V both from the coating material and from the addition at the time of dissolving the wire, but in that case, it is calculated individually from the above formulas and the total is 1.20 to 2.2.
What is necessary is just to be contained in the range of 0 weight%. That is, (Fe-V / coating material) × (coating material / wire) × (V / Fe-V) × 0.85 + 0. If the value calculated by 90 × (V blended in the wire) is in the range of V wt% = 1.20 to 2.20, the operation and effect of the present invention can be reproduced as it is.

[0022]

FIG. 7 is a view showing the size of the insertion ring 5 which should satisfy the conditions imposed this time in the practice of the present invention. For the insert 4 of the cast iron tube,
= 15, X = 25, the steel plate insert ring 5 must be manually welded. Also the nominal diameter is 300-450m
It is specified that welding is performed with M = 20 and X = 30 for a medium diameter pipe of m. As the arc welding rod for forming the welded portion 7, the upper part of Table 1 is a general arc welding rod wire used for alloy steel and the like widely used in the past, and the latter part is a conventional technique and an embodiment of the present invention. This is the range of wire components commonly applied to
Although there is a great difference between Si and Mn, for cast iron, the components were almost the same, and the focus was purely on the effect of V addition in the coating material.

[0023]

[Table 1]

Table 2 shows the components of the coating material of the arc welding rod used in the present invention, and the wire rods shown in Table 1 were commercialized by a usual arc welding rod manufacturing technique. On the other hand, the prior art to be compared is the same as that of Table 2 except that only Fe-V was deleted from the components in Table 2.
Using each type of test welding rod, a test piece at the welded portion was prepared as shown in FIG. That is, the material of the ductile cast iron pipe having a thickness of 10 mm is used as a base material on both sides, and a groove having an inclination angle of 35 ° is formed to 9 to 11 mm below and 2 mm above.
A welding test was carried out with a welding current of 135 to 140 A on a groove having an opening angle of 0 to 23 mm and an inclination angle of 35 °. Table 3 summarizes the results of the micro-Vickers hardness measurement of the embodiment of the present invention and the comparative example according to the prior art, and the meaning of each numerical value is as described above.

[0025]

[Table 2]

[0026]

[Table 3]

Table 4 shows the Charpy impact value (without notch) (Kgm /
cm ² ). In the case of the present invention, although the amount of Fe-V added to the coating material was 11% by weight, in the analysis of the deposited metal, V : 1.40
%, V in Example 2 was 1.60% by weight. The difference between the two components was attributed to the difference in the yield of V in the coating material. 9
5% was discarded, and the appropriate range was limited based on a low 85% as a standard to cope with the variation in yield.

[0028]

[Table 4]

[0029]

As described above, the present invention requires structural strength in cast iron, especially ductile cast iron pipe,
We also provide arc welding rods for cast iron that require the same level of Charpy impact value as the base metal, and various structures,
For example, it has the effect of exerting the greatest power in fixing and welding an insertion ring of a non-fastening method (slip-on type / S2 type) which has attracted the most attention in recent years for laying water pipes. In other words, how the unfastened construction method far exceeded the conventional excavation method in terms of on-site efficiency and workplace safety,
When an external force is applied in the direction of separating the tubes due to vibration, swing, etc., the function of the stopper will depend on the robustness of the insertion ring and the strong fixing action, This is a critical requirement that determines the adoption of a good method. The effect of realizing the material strength that satisfies the requirement by providing the Charpy impact value, strength and hardness in a well-balanced manner according to the practice of the present invention and realizing the required strength is extremely remarkable.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating the basis for limiting the components of the present invention.

FIG. 2 shows wave lines of an X-ray microanalyzer for each component of iron (A), carbon (B), and vanadium (C) in the embodiment of the present invention.

FIG. 3 is an electron microscopic structure (× 600) for each component of iron (A), carbon (B), and vanadium (C), which was the measurement base of FIG. 2;

FIG. 4 Optical microscopic structure of the same embodiment (× 400)
(A) and the explanatory view (B) of the measurement location.

FIG. 5 shows a conventional optical microscope structure (× 400) (A)
(B) of FIG.

FIG. 6 is a table showing micro Vickers hardness of various carbides.

FIG. 7 is a view showing a form of an insertion ring of a non-fastening method (slip-on type / S2 type).

FIG. 8 is a front view (A) and a side view (B) showing a standard for preparing a material test piece of a welded portion.

FIG. 9 is a longitudinal sectional front view of the whole non-fastening method in which the present invention and the prior art are used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reception opening 2 Lock ring groove 3 Lock ring 4 Insertion opening 5 Insertion ring 6 Rubber ring

Continuation of the front page (72) Inventor Takaaki Hashimoto 3-156 Kaiyamacho, Sakai-shi, Osaka Special welding rod Co., Ltd. (72) Inventor Yoshiyuki Hashimoto 3-156 Kaiyamacho, Sakai-shi, Osaka Special welding rod, Inc.

Claims (4)

[Claims] 1. C: 2.0%, Si: 2.5%, Mn:
A weld metal welded with a cast iron material as a base metal by a coated arc welding rod for cast iron made of a wire containing at least Ni: 40 to 60% in addition to 2.5%, and has a V of 1.20 to 2.20.
Welded part by coated arc welding rod for cast iron characterized by containing by weight. 2. C: 2.0%, Si: 2.5%, Mn:
In a coated arc welding rod for cast iron made of a wire containing at least Ni: 40 to 60% in addition to 2.5%, at least 20 to 40% of calcium carbonate, and 10: barium fluoride.
Cast iron characterized in that it contains up to 30%, graphite: 5 to 20% and other effective auxiliary components, and the addition weight% of Fe-V to the coating material is coated with a coating material in a range satisfying the following formula. For coated arc welding rod. (Fe-V / coating material) = 1.20 to 2.20 / [(coating material / wire material) × (V / Fe-V) × 0.85] 3. The wire according to claim 2, wherein V: 1.30 to 2.4 instead of Fe-V added to the coating material.
A coated arc welding rod for cast iron, characterized by containing 0% by weight. 4. The method according to claim 1, wherein the V weight% contained in the welded portion calculated by the following equation is 1.20 to 20.
2. A coated arc welding rod for cast iron, which is included in the range of 2.20. (Fe-V / coating material) x (coating material / wire) x (V / Fe-V) x 0.85 + 0. 90 × (V compounded in wire) …………