JPS595398B2 - Welding electrode with excellent arc stability - Google Patents

Description

Detailed Description of the Invention The present invention provides a welding electrode, particularly a welding electrode with excellent arc stability useful for MIG arc welding. compared to about 9
.

Although it was possible to manufacture a material that was relatively lightweight, as shown in Table 2, the yield was significantly reduced, and therefore,
The present invention attempts to propose a welding electrode that can advantageously realize welding in a pure, inert gas atmosphere, which has been difficult until now, without deteriorating the material quality of the weld metal. In MIG arc welding, when pure, inert gas such as argon gas is used as a shielding gas, the welding arc becomes unstable and welding defects such as slag entrainment and blowholes occur frequently. It has been common practice to use a mixed gas consisting of an inert gas and an appropriate amount of an active gas such as oxygen or carbon dioxide.

However, although mixing active gas is effective in stabilizing the arc and preventing welding defects, it inevitably increases the amount of oxygen in the weld metal, which leads to deterioration of toughness at low temperatures and In some cases, the drawback was that the required performance could not be met.

The inventors previously discovered that adding rare earth elements to the electrode is effective for stabilizing the welding arc, and that by adding an appropriate amount of rare earth elements to the electrode, stable welding can be achieved even in pure, inert gas. It was discovered that welding could be performed under an arc, but in steel types that are highly susceptible to hot cracking, simply adding rare earth elements would cause cracks during the processing of the steel ingot, which poses a problem in terms of practical application. I had left it behind.

For example, if the material for the core wire has the chemical composition shown in Table 1,
When casting into steel ingots weighing 50, 100, and 5000 kg, respectively, cracks spread during forging in the 5000 kg steel ingot, making it impossible to manufacture.

(% by weight) and is therefore difficult to implement on an industrial scale.

The inventors conducted various experiments and studies to solve the above problem, and found that only the surface of the molten metal at the end of the electrode needs to be activated by rare earth elements to stabilize the arc. The rare earth elements inside the droplet do not contribute to arc stabilization at all, and therefore, for arc stabilization, it is not necessary to distribute the rare earth elements evenly over the entire cross section of the electrode, but only on a portion of the electrode surface, for example. It has been found that even if it is unevenly distributed, the effect is no different from that when it is evenly distributed.

Based on the above findings, the inventors conducted further experiments and studies to resolve the difficulties in manufacturing electrodes. First, they created a steel ingot that does not contain rare earth elements as the material for the core wire of the electrode. Next, applying a build-up weld to the surface of a metal with low hot cracking susceptibility that contains an appropriate amount of rare earth elements to make it into an electrode material is extremely effective in preventing the occurrence of cracks during subsequent stretching processing. As a result, even if the steel type is highly susceptible to hot cracking, it can be easily drawn without reducing the yield.Moreover, the electrode surface after the processing is activated, which has the disadvantage of reducing arc stability. It was also found that this does not occur. This invention is based on the above findings.

That is, the present invention provides a welding electrode having a steel coating containing a rare earth element on at least a portion of the outer periphery over the entire length, and the coating has a surface of a core wire material of the electrode.
A weld overlay containing a rare earth element in the range of 0.02 to 0.30% by weight as Ce is formed, and the material is subjected to conventional hot and cold drawing processing along with the core wire material. This is a welding electrode with excellent arc stability.

The basic components of the core material of the welding electrode used in this invention are:
It can be applied regardless of the type as long as it corresponds to the chemical composition of electrodes used for normal purposes.

However, the type of steel used to form the weld overlay is one with low hot cracking susceptibility. The experimental results that led to this invention will be explained below.

Using the welding flux with the chemical composition shown in Table 3 and the strip electrode, rare earth metals were applied to the surface of the core wire material of the welding electrode with dimensions of 25 x 30 x 100 cm under the welding conditions shown in Table 4. Weld metals with different contents of the element (cerium) are built up, and then subjected to hot and cold drawing processing until the diameter reaches 1.2 mm according to the conventional method, and the quality of workability and yield are evaluated. I looked into it.

Next, MIG arc welding was performed in a pure argon gas atmosphere using these electrodes, and the arc stability at this time was investigated. The results are shown in Table 5. For comparison, we conducted the same investigation as above for an electrode in which cerium was added as a rare earth element (0.02 wt ql) (hereinafter simply expressed as %) at the stage of melting the electrode material, and the results are shown in Table 5. Also shown.

The welding conditions when performing MIG arc welding are current:
300A1 voltage: 22V, speed: 30cm/Min, and DC reverse polarity was used. As is clear from Table 5, the electrode according to the present invention has extremely good workability, and no cracking occurs even during hot and cold stretching, and the yield is 80% or higher than that of the conventional electrode. This is a dramatic improvement compared to .

In addition, the cerium content of the overlay metal needs to be 0.02q1) or more for arc stabilization, and 0.02
% or more, it will have an excellent effect on the activation function, but
If it exceeds 0.30 (II), there is a disadvantage that cracks will occur during drawing even if a steel with low cracking susceptibility is used to form the overlay metal layer, so the cerium content is 0.
．． The upper limit is 30(f).

The same goes for other rare earth elements, and their content is 0.
It was confirmed that a range of 0.02 to 0.30% is effective for stabilizing the arc.

Therefore, as a rare earth element, if there is a commonly available mishi metal, for example, about half of which is Ce, the yield of the rare earth element in the overlay metal can be calculated using the amount of Ce as a guide. It is easy to handle by determining the amount added.

Next, we investigated the workability and arc stability depending on the coating state of the overlay metal, and found that it is not necessary to perform overlay welding on all four longitudinal sides of the core material 1, as shown in Figure 1a. However, as shown in Figures B, C, and D, even if only one, two, or three of the four surfaces are overlay welded, if the amount of rare earth elements in the overlay metal 2 is within the appropriate range, It was confirmed that they had the same effect. In particular, when overlaying is applied to the four sides of the core wire material 1 shown in FIG. 1a, the corrosion resistance of the electrode surface can be improved by adding an appropriate amount of Cr to the overlay metal 2. Therefore, it is possible to omit the process of imparting corrosion resistance such as Cr plating after drawing, which is advantageous.

As described above, according to the present invention, arc stability is advantageously achieved in a pure inert gas atmosphere without the need for adding active gases such as oxygen and carbon dioxide that cause material deterioration of weld metal as in the past. As a result, the amount of oxygen mixed into the weld metal can be reduced, and the toughness can be significantly improved.Moreover, even if a steel ingot with a large unit weight is used as the material for the core wire of a welding electrode, it can be stretched. There is no cracking in the welding electrode, and the product yield is significantly improved even when using steel types that are highly susceptible to hot cracking, so it is useful for greatly increasing the production efficiency of this type of welding electrode.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an electrode material and a product electrode showing the state in which the welding electrode is built up on the surface of the core wire material. 1... Core wire material, 2... Overlay metal.

Claims (1)

[Claims] 1 A welding electrode having a steel coating containing a rare earth element on at least part of its outer periphery over its entire length, the coating including a rare earth element (Ce) on the surface of the core material of the electrode.
The product is characterized by forming a weld overlay layer containing 0.02 to 0.30% by weight of 0.02% to 0.30% by weight, and subjecting it to a conventional hot and cold drawing process along with the core material. A welding electrode with excellent arc stability.