JPS6234471B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to arc stud welding, particularly cyclo-arc welding, which is used in various fields such as the assembly of upper decks in ship construction, the manufacture of composite beams in bridges, and the manufacture of composite beams in building construction. Regarding ferrules used for stud welding.

In cyclo-arc method stud welding, the tip of the stud of the appropriate shape and size is
The stud is surrounded by a short tube-shaped heat-resistant ceramic called a ferrule, and the tip of the stud is brought into contact with the base metal to be welded, and electricity is applied between the stud and the base metal.Then, the tip of the stud is moved slightly away from the base metal to generate an arc. This melts the tip of the stud and the base material, and quickly presses the stud against the molten pool of the base material.

The above ferrule surrounds the molten metal to prevent it from flowing out or scattering when the stud is pressed, and also acts as a mold to form an appropriate backing to obtain welding strength. , serves to prevent rapid cooling of the molten metal and ensure time for gas release from the molten metal.

Therefore, ferrules were required to not be easily destroyed by the influence of molten metal during welding operations and to have appropriate heat insulation properties.

However, in reality, due to rapid metal melting due to arc generation within the ferrule, the inner layer of the ferrule reaches the temperature of the molten metal from room temperature in just 1 to 2 seconds, resulting in a sudden temperature drop between the inner and outer layers of the ferrule. This difference caused the ferrule to often break due to the sudden generation of thermal stress.

As a result of research, the present inventor has found that in order to withstand such thermal shock, a large number of micropores are uniformly distributed in the ferrule, and even if a crack occurs due to thermal stress, the propagation of the crack is suppressed by the micropores. The inventors have discovered that it is sufficient to prevent the ferrule from being destroyed as a whole even if a part of the ferrule is destroyed, and that these pores also provide heat insulation properties.

However, if the porosity is too large or the pore size is too large, not only will the mechanical strength of the ferrule decrease, but also the water absorption rate of the ferrule will increase.
There was a problem in that moisture that entered the micropores rapidly expanded during welding and destroyed the ferrule.

The object of the present invention is to provide arc stud welding which has thermal shock resistance and heat insulation properties by having a large number of micropores, and which can completely or negligibly prevent water absorption into the micropores. The objective is to provide ferrules for

The above object of the present invention is achieved by a ferrule for arc stud welding characterized in that pores of about 100 microns or less in size are dispersed at a porosity of about 15 to 30% and treated to be water repellent.

According to the present invention, since the pores with a size of about 100 microns or less are dispersed in the ferrule with a porosity of about 15 to 30%, the ferrule has the necessary thermal shock resistance while maintaining an appropriate mechanical strength. It has the advantage of being able to provide properties such as heat and heat insulation. More specifically, these micropores prevent cracks caused by thermal stress from propagating, preventing the entire ferrule from being destroyed, and the heat insulating properties of the micropores also prevent the inner surface of the ferrule from coming into contact with molten metal and melting. Even when the ferrule is vitrified, the ferrule from the center to the outer periphery does not melt, and the original shape of the ferrule is maintained as a whole, and the molten metal inside the ferrule is prevented from rapidly cooling, giving time for gas to escape from the molten metal. It will be done. In addition, since the pores improve the heat insulation properties, it becomes possible to make the ferrule using a material with a correspondingly low fire resistance, which has the advantage of widening the range of materials to choose from. If the pore size exceeds 100 microns, it is unsuitable because coarse pores will be unevenly distributed. Furthermore, if the porosity is less than 15%, the thermal shock absorption ability and heat insulation properties will be reduced, whereas if it exceeds 30%, the mechanical strength of the ferrule itself will be significantly reduced.

Further, according to the present invention, since the ferrule is treated to be water repellent, water absorption into the pores is substantially prevented, and the moisture in the pores does not expand rapidly during welding and destroy the ferrule. The water repellent or waterproof effect of the water repellent treatment in the present invention is extremely large. That is, known ferrules are stored in a sealed state, and if opened, they absorb water and become unusable within a few hours. However, since the ferrule of the present invention absorbs virtually no water, there is no need to take special precautions in storage. In addition, welding work can be performed without being affected by weather conditions, work conditions, and work environments, and concrete pouring and water work can be performed nearby, and welding can be performed in areas with a lot of water, such as underground construction and tunnel construction. is possible. Furthermore, even if you interrupt your work or leave the ferrule anywhere, such as outdoors or in a place where there is a lot of water, you can use it again at any time. Furthermore, the effect of preventing water absorption through such water repellent treatment has opened the door to the use of ferrules in underwater welding.

The ferrule of the present invention can be obtained by kneading, molding, drying and firing refractory raw materials according to a conventional method, and then treating the fired product with, for example, a silicone emulsion. Treatment with a silicone emulsion can be carried out by any means such as coating, spraying, or dipping into an emulsion. Instead of silicone water repellent treatment, a carbon film may be formed on the ferrule to provide a water repellent effect to the film. This carbon film can be formed by, for example, blowing a carbon-containing reducing gas in the final stage of firing the ferrule.
It can be obtained by cutting off air, adding fuel, and causing thermal decomposition.

Example 1 After 85 parts by weight of Shinano Kibushi clay and 15 parts by weight of talc were pulverized and mixed in a ball mill for 8 hours, 7.5 parts by weight of water was added and mixed for an additional 10 minutes in a crusher. After putting 17.5g of the obtained mixture into a mold and molding it,
It was fired at 1160°C for 1 hour, allowed to cool in the furnace, and then taken out.
The baked product was immersed in a 0.5% silicone emulsion for 10 minutes and then dried at 150°C for an hour to reduce water absorption to zero.

The size of the pores in the obtained ferrule is less than 100 microns, and the average porosity of the six ferrules is
It was 22.92%.

Using the six ferrules thus obtained,
When welding tests were conducted on studs with a diameter of 22 mm, no ferrule fracture occurred during welding.

In addition, the obtained stud welds were subjected to a tensile test (3 pieces) and an impact test (3 pieces), but in each case, breakage occurred in areas other than the weld.

Further, when the ferrule obtained by the method of this example was left in the air for one day and night during the rainy season and then used for stud welding in the same manner as above, good results similar to those above were obtained.

Comparative Example 1 A ferrule was obtained in the same manner as in Example 1, except that the raw material mixture molded product prepared in the same manner as in Example 1 was fired at 1200°C.

The average porosity of the six ferrules obtained was 8.36%.
It was hot.

When stud welding was performed in the same manner as in the example using six ferrules obtained in this way, 5
Welding failed as several ferrules were destroyed. This is thought to be because the porosity is low and the thermal shock resistance is poor.

Example 2 A ferrule was produced in the same manner as in Example 1 except that 80 parts by weight of Shinano Kibushi clay and 20 parts by weight of talc were used.

The pores of the ferrule were less than 100 microns, and the average porosity of the six pores was 24.73%.

When used in stud welding, the ferrule did not break and the shape and strength of the welded part were good.

Claims (1)

[Claims] 1. A ferrule for arc stud welding characterized by having pores with a size of approximately 100 microns or less dispersed at a porosity of approximately 15 to 30% and treated to be water repellent.