JPH0587467B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an impeder cooling pipe used in electric resistance welding metal pipe welding. <Prior Art> When the temperature rises due to heat loss, the magnetic permeability decreases and the power efficiency of welding deteriorates. Therefore, the impeder needs to be cooled with a cooling medium such as water. Generally speaking, this cooling method involves inserting the impeder into a pipe through which a cooling medium flows, but heat-resistant resin such as epoxy resin has conventionally been used for this impeder cooling pipe. <Problems to be Solved by the Invention> However, conventional impeder cooling pipes have a lifespan of only 3 to 10 days due to adhesion of beads formed on the inner diameter due to welding and deformation due to heat, and require frequent pipe removal. It needed to be replaced. This required the removal of cooling water, which was a major cause of reduced productivity. SUMMARY OF THE INVENTION An object of the present invention is to provide an impeder cooling pipe that is free from adhesion of beads and deformation due to heat, is not subject to induction heating even when high frequency is applied, and has heat resistance and wear resistance. <Means for solving the problems> In order to solve the above problems, the present inventors have
As a result of various experiments, we found that a sintered body containing silicon carbide as a main component is the most suitable material for the impeder cooling pipe, and completed the present invention. That is, the gist of the present invention is an impeder cooling pipe characterized by being made exclusively of a silicon carbide sintered body and having a hollow cylindrical shape having a cooling medium passageway inside. It is. As described in claim 2, it is more preferable to replace a portion (10% by weight or less) with ferrite (MFe ₂ O ₄ ; M is mainly a divalent metal element). <Function> There are various heat-resistant pipe materials, but conductive materials such as metals and carbon are not suitable as materials that do not undergo induction heating even when high frequencies are applied, so materials that do not have electrical conductivity or Alternatively, a material that is a poor conductor, has heat resistance, and is difficult to deform is required. As a result of various experiments, it has been found that certain types of ceramics are optimal for use as impeder cooling materials. This type of ceramic is mainly composed of SiC, and these ceramics are optimal because they are oxidation resistant and difficult to undergo induction heating. In addition, the silicon carbide-based sintered body produced by reaction sintering has excellent strength such as bending strength, and is optimal as an impeder cooling pipe. Silicon carbide is an antiparamagnetic material, so it exhibits paramagnetism when a magnetic field is applied to it, so it works to reinforce the magnetic permeability of the ferrite core used in the impeder, so the power required for welding is less than that of other materials. It is 20-30% less than the standard. When ferrite is included in the SiC sintered body, the power required for welding is further reduced. The higher the ferrite content, the higher the magnetic permeability and the higher the power efficiency, but if the content exceeds 10% by weight, the hardness decreases and the strength such as bending strength decreases significantly, making it difficult to use as an impeder cooling pipe. cannot be used, and the content is less than 10% by weight (0 is not included)
It is required that Note that if the impeder cooling pipe body is made of ferrite such as Fe ₃ O ₄ , the power efficiency will increase, but this type of pipe is insufficient in strength and cannot be used as an impeder cooling pipe. This sintered body is wear-resistant, so even if the bead comes into contact with the pipe, it will not be damaged, and its life will be significantly longer than that of conventional impeder cooling pipes. <Examples> The present invention will be described in detail below while showing examples thereof.
However, the present invention is not limited to the scope of the following examples. Note that the contents described in the Examples section below are not necessarily limited to those within the scope of the claims of the present invention, but may also be referred to as comparative examples for comparing the effects and effects of the present invention with conventional techniques. It is noted that the contents are also described. That is, the impeder cooling pipe of the present invention and the conventional impeder cooling pipe made of epoxy resin were used to manufacture steel pipes by performing high frequency resistance welding, and the two were compared. As a reference, similar pipes were prototyped using other ceramics and practical tests were conducted. Regarding other ceramic products, commercially available products were processed and used for testing. The silicon carbide-based sintered body of the present invention was prepared as follows, and its physical properties were compared with those of other ceramic materials. Preparation of raw material powder A ₂ O ₃ with a purity of 99.9% (particle size 0.4 μm) and a purity of 99.9
% Er ₂ O ₃ (particle size 0.8 μm), 98.5% pure Fe ₃ O ₄ (particle size 0.8 μm) and 98.5% pure SiC (particle size 0.5 μm) were prepared in the proportions shown in the table. , Wet mixing was carried out in a ball mill for 15 hours. After drying, particle size
A powder of 0.5 μm was obtained. Preparation of Impeder Cooling Pipe of the Present Invention Using the obtained raw material powder, the impeder cooling pipe of the present invention was produced by the following method.
The raw material powder is placed in a pressure-resistant rubber bag along with an iron core material with a diameter of 40 mm and a length of 235 mm so that the powder covers the core material, and the bag is sealed, and then a cold hydrostatic pressure of 1 t/cm ² is applied to form a green compact. I made it, machined it, shaped it, and removed the core material. Thereafter, it was sintered at a temperature of 2000°C in an Ar atmosphere to obtain a cylindrical silicon-based sintered body with an outer diameter of 60 mm, an inner diameter of 40 mm, and a length of 230 mm. Preparation of transverse rupture strength test piece Using the raw material powder obtained in step 1, a compact was made using a mold press at a pressure of 1 t/ ^cm2 , and then it was pressed in an argon atmosphere.
It was sintered at 2000℃ for 1 hour. This result is approximately 50×50×5.5
A sintered body with a shape of mm was obtained. Using a diamond wheel cutting machine, ten test pieces each having a shape of 3 x 4 x 36 mm were produced.

【table】

[Table] Here, welding efficiency is a constant electric power a, and if the amount of welding work when epoxy resin is used for metal pipe welding (steel pipes here) is 100, it is the amount of work with the same electric power. shall be said. As a comparative test, pipes made of Si ₃ N ₄ , A ₂ O ₃ , ZrO _{2 ,} etc. were used, but the welding efficiency did not improve, and all pipes except Si ₃ N ₄ were weak against thermal shock. Next, Table 2 shows some of the physical properties measured for the impeder cooling pipe of the present invention and other ceramic materials.

【table】

[Table] <Effects of the Invention> As described above, according to the present invention, there is no adhesion of beads or deformation due to heat, and there is no induction heating, and the pipe can function satisfactorily as an impeder cooling pipe. It is something that can be demonstrated. The reason for this is that the material of the pipe of the present invention is made exclusively of silicon carbide, and in particular, the pipe according to claim 2, in which a part of silicon carbide is substituted with MFe ₂ O ₄ (M is mainly a divalent metal element), is made of silicon carbide. It is thought that the cause is that only the very surface layer of the pipe is heated, either due to the movement of the point or the arrangement of atoms that make up the material becomes disordered. This also means that ferrite can be added only to arbitrary parts.
By installing it, you can prevent only certain parts from getting heated.

Claims (1)

[Scope of Claims] 1. An impeder cooling pipe characterized by being made exclusively of silicon carbide-based sintered body and having a hollow cylindrical shape having a cooling medium passageway inside. 2. An impeder cooling pipe characterized in that 10% by weight or less (not including 0) of the silicon carbide-based sintered body is replaced with ferrite (MFe ₂ O ₄ ; M is mainly a divalent metal element).