JPS5847955B2 - coated arc welding rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the formulation of a coated arc welding rod, and particularly to a coated arc welding rod in which fine grained iron powder is added to improve arc regeneration.

Currently, JIS Z3211 D4327 Iron powder iron oxide type welding rod (hereinafter referred to as iron powder iron oxide type) JIS Z3211
D4340% special type welding rod (hereinafter referred to as special type) is
It is widely used for downward and horizontal fillet welding of various structures such as shipbuilding and bridges by hand or in combination with gravity welding machines and low-angle welding machines.

In manual welding in particular, when the welding line is short or when used for intermittent welding, when the arc is interrupted during welding and the arc is generated again, the tip of the welding rod is generally removed if the arc interruption time is longer than about 3 minutes. Even a light contact will make it difficult for the arc to occur again.

By the way, as a conventional means of smoothing out the re-generation of the arc, ■ Although the sheathing tube itself has poor electrical conductivity, applying an impact to the welding rod easily breaks the sheathing tube at the tip of the welding rod, exposing the tip of the core wire. Considerations are being made to make the coating cylinder itself more conductive than the coating material.

On the other hand, the following methods are known as means for imparting electrical conductivity to the coating material.

(b) Increase the amount of organic material added and take advantage of the fact that as the welding rod melts, the organic material at the tip of the sheathing tube carbonizes and increases electrical conductivity.

((d) Increase the amount of rutile (Ti02) added.

(C) Increase the amount of iron powder added to provide electrical conductivity.

Various studies have been conducted.

However, although it is certainly possible to improve the re-occurrence of the arc by incorporating a large amount of organic matter or rutile into the coating material, adding organic matter or rutile further may cause problems in the formulation. Balance will impose restrictions on other combinations.

In particular, it is well known that not only problems such as poor welding shape and rod burns occur when it comes to welding workability, but also that sound weld metal cannot be obtained. It is not possible to provide a practically satisfactory welding rod that is free from arc regeneration and has the ability to regenerate arcs.

In particular, the method of increasing the amount of iron powder added in the previous edict is extremely effective for re-occurring arcs when the amount of iron powder added is 60% or more, but on the other hand, with L. This causes problems such as a decrease in dielectric strength (arc occurs from the coating) and a tendency to cause stick burns.

Furthermore, if too much iron powder is added, productivity during the production of welding rods will deteriorate, so there is a limit to the amount of increase in iron powder.

Therefore, the inventors of the present invention have developed an iron powder containing 60% or more of fine particles with a particle size of 63 microns or more, in place of the iron powder particle size control conventionally used for iron powder iron oxide type and special type coated arc welding rods. By using 15 to 60% of powder (hereinafter referred to as fine iron powder), the arc can be interrupted for, for example, 30 minutes or more during welding and the arc can be generated again without causing problems such as impairing welding workability as described above. Even in cases where the welding rod tip lightly touches the object to be welded, current flows easily**
We have succeeded in developing a coated arc welding rod that enables arc regeneration.

That is, an example of the particle size structure of the fine iron powder used in the present invention and the conventional iron powder is shown in Table 1. Compared to the various iron powders that were previously used, the fine particles with a particle size of 63 microns or less were 63.
5%, and has a finer pore structure and irregular particle shape than conventional iron powders, so they link together to improve electrical conductivity, and as a result, the re-generation of the arc, which is the objective of the present invention. Not only does it improve the stability of the arc during welding, it also reduces the temperature rise of the coating material, making it possible to manufacture long rods, thereby significantly improving practical performance.

The present invention was made based on such knowledge, and the gist thereof is that 15 to 60% of iron powder, of which 60% or more of fine particles with a particle size of 63 microns or less, Si0210
~30%, Ti024~25%Mn3~12%, MgC
The sum of one or two of O3 and CaCO3 is 0.5 to 1
8%, FeO + Fe203 1.5-15%, 0 organic substances
．． A coated arc welding rod characterized in that a steel-free steel is coated with a coating material containing 1 to 4% of CaO and one or both of MgO and 10% or less of the total.

The present invention will be explained in detail below.

The reason for using iron powder containing 60% or more of fine particles with a particle size of 63 microns or less in the present invention is that the productivity in manufacturing welding rods is improved, and the addition of water glass improves the bond between the coating materials and between the coating material and the core wire. It greatly contributes to the electrical conductivity of the coating material and smooths out the re-occurrence of the arc.
This is because if the content of fine particles of 3 microns or less is less than 60%, the effect of improving arc regeneration cannot be expected to be that great.

The test results revealed that good arc regeneration can be obtained if 60% or more of the particles are 63 microns or less.

Further, the lower limit of the composition range is set at 15% because if the content is less than 15%, it is not expected to be effective in improving work efficiency and preventing arc re-occurrence.

On the other hand, if it exceeds 60%, the insulating properties of the welding rod will deteriorate and arcs will be more likely to occur from the side surfaces of the coating, which is unfavorable in terms of safety during welding work.

Further, the reason why the other compositions of the coating material of the present invention are set within the above range is as follows.

SiO2 acts as a slag generator and has a strong influence on the viscosity of slag during welding.
When the content is less than 0%, the viscosity of the slag decreases, and the beads exhibit non-uniform waveforms, making it difficult to adjust the bead shape.

If the content exceeds 32%, the viscosity of the slag becomes excessive and the slag does not cover the bead surface uniformly, resulting in defects in the bead.

If TiO2 is less than 4%, the leg lengths of the horizontal fillet beads will be uneven, so the content should be 4% or more.This improves the encapsulation of the slag to the bead, and particularly adjusts the viscosity of the slag in the horizontal fillet. The contribution to this will increase.

On the other hand, if it exceeds 25%, the arc re-occurrence is smoothed out, but the heat resistance of the coating material deteriorates, and the latter half of the welding rod during welding becomes burnt, resulting in uneven bead shape and prohole formation. defects such as frequent occurrence of

Therefore, the upper limit of the content of Ti02 was set to 25%.

The content of Mn as a deoxidizer affects weldability and must be carefully examined, but in the blend system of the present invention, 3 to 12% is appropriate, and a blend of less than 3% will cause pits and pits due to insufficient deoxidation. Proholes occur, resulting in defects such as poor bead shape and poor bead appearance.

On the other hand, if it exceeds 13%, there will be problems with slag viscosity and slag fluidity, resulting in defects such as poor rebead shape and poor bead appearance.

MgCO3 and CaCO3 act as gas generating agents and can be used alone or in combination, but the sum of one or two of MgCO3 and CaCO3 is 05~
18% is appropriate, and if it is less than this range, the fluidity of the slag will be poor due to the relationship with other components, and the removability of the slag will be poor.

Moreover, if the content exceeds the above range, the arc blowing strength will be too strong and will become unstable, resulting in an increase in the amount of sputtering and making undercuts likely to occur in the welded part.

Although organic substances have a remarkable effect of facilitating the re-occurrence of the arc, which is the object of the present invention, it is difficult to obtain a stable arc when the amount is less than 0.1%.

On the other hand, if the content exceeds 4%, the arc blowing strength will be too strong and the amount of spatter will also increase, and if used at excessive current, it will be easy to cause burns, so the upper limit was set at 4%.

The purpose of FeO+Fe203 is to adjust the viscosity of the slag and improve pitting resistance, but if it is less than 1.5%, the viscosity of the slag increases, fluidity deteriorates, and pits occur.

When it exceeds 15%, the melting point of the slag is lowered, the encapsulation properties of the slag are deteriorated, and the bead shape is deteriorated.

Finally, the reason for limiting CaO and MgO will be explained as another part.

Cab and MgO have different effects from CaCO3 and MgCO3, and since they are oxides, they are related to the stability of the arc and the fluidity of the slag.The appropriate content is 10% or less, and if it exceeds this, the fluidity of the slag will decrease. The appearance of the bead becomes disordered and the arc condition worsens.

Therefore, the sum of one or two of CaO and MgO was set to 10% or less.

The coating material containing the above-mentioned components is coated on the steel core wire using a binder such as water glass, using the normal welding rod manufacturing process.
It can be manufactured by drying.

The steel core wire used in the welding rod of the present invention is defined by JIS
Refers to the core wire that corresponds to G3523 Type 1 No. 1.

The effects of the welding rod of the present invention will be explained below based on Examples.

EXAMPLE Table 2 shows the results regarding the composition of the coating material, the difficulty of arc re-occurrence, and the welding workability of the coated welding rods tested according to the present invention.

The coating composition shown in Table 2 is JIS G3523-1.
Corresponds to type 1.

Using a mild steel core wire of 5.0φmm x 700mm, a mild steel plate (
T with plate thickness 12mm, width 100mm, length 1000mm)
Make a letter-shaped test plate or weld it by hand for 50m at a current of 230Amp.
After welding, the arc was cut off, and 30 minutes later, one end of the protective tube was brought into light contact with a mild steel plate to prevent the protective tube from chipping, and the difficulty of re-occurring the arc was examined.

In Table 2, A-1 to A-5, B-5, B6, B-1
1, B-12, C-1 to C-5 are comparative examples, B-1 to B-
4, B-7 to B-10 are examples of the present invention (those marked with ★).

A-1 to A-5 are conventional rJIs Z3211 coated arc welding rods for mild steel, which are formulation examples based on iron powder iron oxide welding rods and use ordinary commercially available iron powder, and A- Both 1 and A-2 have poor electrical conductivity and good bead shape, stick burn, etc., but A-1 in particular has poor electrical conductivity.
02, FeO + Fe203 is excessive, so it is inferior in terms of arc regeneration.

In A-3, A-4, and A-5, arc re-occurrence is possible only within 3 minutes after the arc is interrupted, and among A-4 and A-5, A-5 in particular has excessive TiO2, so it is difficult to coat it. The heat resistance of the welding agent deteriorates, and the latter half of the welding rod becomes burnt, which deteriorates the bead shape.

C-1 to C-5 are formulation examples of special welding rods in the coating material system, and these also use ordinary commercially available iron powder, and the bead appearance, slag removability, etc. are similar to that of iron powder iron oxide welding. Better than rods, but generally inferior in terms of arc regeneration.

In particular, C-1 has a large amount of MgCO3, C-2 has an excessive amount of MgO, and C-3 has an excessive amount of Mn and a shortage of Ti02, so that the arc re-occurrence is bad.

Among C-4 and C-5, especially C-5, there is no carbonate < Ti02, the content of organic matter is high, and Si02 is insufficient, so the arc re-occurrence is rather good, but the arc is interrupted. It lasts for about 1 minute.

On the other hand, B-5, B-6, B-11, and B12 are examples using fine iron powder, but B-6 and B11 have iron powder content higher than the appropriate range, so arc Although the regeneration is good, the latter half of the welding rod during welding causes a burn phenomenon, which deteriorates the bead shape.

In addition, B-5 and B12 have a low content of iron powder outside of the appropriate range, so the bead shape, bar burn, etc. are good, but the re-occurrence of arc is poor.

On the other hand, by using the fine iron powder according to the present invention in B-1 to B-4 and B-7 to B-10, arc regeneration is significantly improved without changing workability.

In particular, in the blending examples of B-2 to B-4 and B-8 to B-10 of the present invention, the arc re-occurs well even after the arc interruption time has passed for 30 minutes or more, and the welding workability is also as good as that of the conventional one. The practical effects of the present invention in the field of coated arc welding are extremely significant.

Claims (1)

[Claims] 1 Iron powder 15-60%, SiO2 10-32%, TiO24-24%, with 60% or more of fine particles having a particle size of 63 microns or less
25%, Mn3-12%, MgCO3 and CaCO3
The sum of one or two of these is 05-18%, organic substances 0.1
~4%, FeO + Fe2 031. 5 ~ 1 5
%, and the sum of one or both of CaO and MgO is 10% or less, on a steel core wire.