JP4841364B2 - Polishing method of link chain having fatigue strength of 230 N / mm 2 or more - Google Patents

Description

The present invention relates to a method for polishing a link chain having a fatigue strength of 230 N / mm ² or more only by applying mechanical vibration.

As a performance required for a chain block, particularly a link chain used for an electric chain block, there is a high fatigue strength characteristic. This is because when a load is lifted / suspended at high speed, the link chain undergoes load fluctuations, and this repeated action causes fatigue cracks from the site of maximum stress generation in the link chain, which eventually leads to failure. It has been. Conventionally, in the stress concentration part that causes fatigue failure in the manufacturing process of the link chain, a slight misalignment of the mating surface of the upper and lower molds used when forming the link shape, gaps, etc. are generated As a result, stripes and burrs with a maximum height of 200 μm are formed on the link. This protrusion becomes a stress concentration source during use and becomes a starting point of fracture. In addition, since the position of the protrusion coincides with the position where the maximum stress generated in the link chain, that is, the position corresponding to the boundary between the parallel portion and the curved portion of each link of the link chain, To remove by processing such as cutting and polishing, a great work is required. For this reason, in the above-described link chain having high fatigue strength, there is a demand for reducing protrusions to the minimum without protrusions. Various proposals have been made to meet this demand.

  For example, Patent Document 1 discloses that as a method for obtaining high fatigue strength, a corrosion resistant / abrasion resistant coating treatment is applied to a shoulder inner portion of an element ring of a quenched, tempered / tempered link chain. . On the other hand, barrel polishing is conventionally employed as a method for mechanically removing the protrusions and burrs. In this barrel polishing, a polishing grindstone, workpiece and other necessary chemicals are inserted and sealed in the polishing tank, the entire polishing tank is rotated at a constant speed by driving a separate motor, and the polishing tank is stirred for a predetermined time. By doing so, the protrusions and burrs of the workpiece are removed (rotary barrel polishing machine). Further, as proposed in Patent Document 2, the polishing tank is vibrated at a specific frequency, and a polishing grindstone, a workpiece, and other necessary chemicals are inserted into the polishing tank, and the vibration of a motor provided separately. There is a method of removing the protrusions and burrs of the workpiece by vibrating the whole polishing tank and stirring the polishing tank (vibrating barrel polishing machine). As this vibration source, a commercially available vibration motor or a method of generating vibration by rotating a counterweight through a motor-driven coupling is adopted, which is a commercial machine as a vibration barrel polishing machine.

  The present inventors tried to apply to the link chain by using the above-described conventional manufacturing method. However, the chain length (chain-like shape) has little polishing effect on the inner side of the link that needs to be deburred and withstands the productivity. ) Was stirred in the polishing tank of the vibration barrel polishing machine, and it was found that the chain became humped and the improvement of the polishing effect could not be expected. This is because the polishing tank is normally rotated in one direction, so that the chain can also rotate only in one direction, and the link chain is twisted, so that the degree of freedom of each link chain is impaired. . Therefore, the conventional method has almost no polishing effect inside the link.

JP 2003-221621 A Japanese Patent Application No. 2005-366305

The present invention provides a method for polishing a link chain having a fatigue strength of 230 N / mm ² or more only by applying mechanical vibration.

The present invention has been made to solve the above problems, and the gist thereof is as follows.
(1) After forming a low carbon alloy steel wire into a link shape using a mandrel consisting of an upper die and a lower die, and parallel portions of individual links of a chain-like link chain manufactured by welding end faces to each other The protrusions and burrs generated due to the overlapping surfaces of the upper and lower mandrels at the boundary of the curved portion are polished by a vibration polishing machine without using a polishing medium or fluid. A link chain having a fatigue strength of 230 N / mm ² or more, wherein the height is 60 μm or less .
(2) The link chain having a fatigue strength of 230 N / mm ² or more according to (1), wherein the protrusion and the burr height are 30 μm or less.
(3) A chain produced by welding the end surfaces of a low-carbon alloy steel wire before quenching / tempering treatment or after quenching / tempering treatment into a link shape using a mandrel consisting of an upper die and a lower die The link chain is oscillated in a stationary or transported state on the polishing tank, and the individual links of the link chain are removed without the use of polishing media or fluids by a vibration polishing machine that applies vibration that rubs or hits the links. The protrusions and burrs generated due to the overlapping surfaces of the upper and lower mandrels are polished at the boundary between the parallel part and the curved part so that the height thereof is 60 μm or less. A manufacturing method of a link chain having a fatigue strength of 230 N / mm ² or more.
(4) The method for producing a link chain having a fatigue strength of 230 N / mm ² or more according to (3), wherein the vibration applied by the vibration polishing machine has a vibration frequency of 10 to 40 Hz and an amplitude of 1 to 6 mm. .
(5) 230 N / mm according to (3), wherein the link chain placed on the polishing tank and subjected to vibration polishing is a long link chain having a plurality of folded portions on the polishing tank. ^A method for manufacturing a link chain having a fatigue strength of ² or more.
(6) The production of the link chain having a fatigue strength of 230 N / mm ² or more according to (3), wherein the polishing time of the long link chain conveyed on the polishing tank is 1 to 4 hours. Method.
(7) The method for producing a link chain having a fatigue strength of 230 N / mm ² or more according to (3), wherein the link chain that has been plated after the quenching and tempering treatment is subjected to vibration polishing.

According to the present invention, a link chain having high fatigue strength can be obtained by polishing fine protrusions, burrs, and the like inside the link generated during the manufacture of the link chain, without being limited by the length of the link chain, by simply applying mechanical vibration. Can be removed evenly and efficiently at low cost, and a high-quality link chain can be provided.

When forming into a link shape in the manufacture of a link chain, after forming into a link using a mandrel comprising an upper mold and a lower mold, the end faces are formed by welding. Due to the occurrence of minute deviations and gaps on the mating surfaces of the mandrels during this molding process, as shown in FIG. 1, projections or burrs with a maximum height of 200 μm are formed inside the link. If these protrusions and burrs are left as they are, they become stress concentration sources during use and become the starting point of destruction. It has been found that this protrusion position frequently occurs at the boundary between the parallel part and the curved part inside each link of the link chain.

  The inventors of the present invention are eager to eliminate the above-described protrusions or burrs easily or quickly without using a vibration barrel polishing machine using a complicated and expensive polishing medium or fluid as in the prior art. Study was carried out. As a result, in the vibration barrel polishing machine, the link chain polishing tank is mounted only on the polishing chain or the polishing chain of the link chain mounted on the polishing table without using a polishing medium or fluid. It was clarified that protrusions and burrs inside the link were remarkably reduced by devising and applying them so that the links could be freely rubbed, collided, and struck. Hereinafter, it is called a vibration polishing machine. The present invention has been made based on the above knowledge, and a link chain manufactured from a wire made of low carbon alloy steel before quenching / tempering treatment or after quenching / tempering treatment is placed on a polishing table of a vibration polishing machine. Place and vibrate the polishing tank in a stationary or conveying state, and further polish the surface by vibrating the link chain itself, minimizing protrusions and burrs at the boundary between the parallel part and curved part of each link of the link chain. It is possible to manufacture a link chain having a fatigue strength of 60 μm or less, preferably 30 μm or less of protrusions and burr heights at the boundary portions of the curved portions of the parallel portions of the individual links of the polished link chain. It has become.

  The polishing method according to the present invention uses only a vibration source used in a vibration type barrel polishing machine or a commercially available vibration motor, and directly connects the link chain placed on the polishing tank to the vibration source via the polishing tank. It is transmitted, vibrated, and polished. Specifically, the vibration type barrel polishing machine used in the present invention is provided with a polishing tank in which an elastic body is laid so that a link is not damaged via a spring spring on a base. It is not necessary to use any abrasive in the polishing tank regardless of whether it is a grindstone, solid or liquid. A vibration motor is directly attached to the lower part of the polishing tank, or a counterweight unit connected to or integrated with the polishing tank is provided, and a rotating shaft connected to a separately provided motor extending in parallel with the base connected to the counterweight unit. The rotation of the motor is converted into vibration by the counterweight unit via the rotating shaft, and the link chain placed in the polishing tank is vibrated.

  The link chain may be placed on the polishing tank in a straight line as long as it is a short link chain. For example, in the case of a long link chain with a length of several tens of meters, the chain link is heavy. As a structure that has a number of folding points on a straight parallel partition wall with a specific interval in the longitudinal direction of the polishing tank so that it does not become a sheave from the carry-in port at one end to the carry-out port at the other end, the polishing processing time The polishing speed is adjusted so as to be 1 to 4 hours, and polishing is performed while continuously conveying. And it is preferable that the vibration provided to the link chain conveyed is vibration frequency 10-40Hz and amplitude 1-6mm. Although the conveyance speed and the applied frequency vary depending on the size and length of the link chain, if the link size is about 3 mm to 13 mm in diameter, the polishing time is 1 to 4 hours, the vibration frequency is 10 to 40 Hz, and the amplitude is 1-6 mm can be sufficiently polished. When the vibration frequency is 10 Hz or less and the amplitude is 1 mm or less, a defective polishing portion is generated. On the other hand, when the vibration frequency is 40 Hz or more and the amplitude is 6 mm or more, polishing is saturated, and it is unrealistic to make an apparatus that can withstand production. Moreover, although the conveyance speed depends on the length of the link chain, the size of the polishing tank, the arrangement amount of the link chain, and the conveyance speed of the link chain, it is preferably about 0.02 to 3.33 m / min. Although the specific mechanism of this polishing is still unclear, the vibrations applied appropriately to guess the chain links are in a chain state, so the links rub against each other with high frequency and collide with each other. It is considered that the protrusions are rubbed together.

  The link chain according to the present invention thus processed provides a link chain in which the parallel part of each link of the link chain has a protrusion at the boundary of the curved part and a burr height of 60 μm or less, preferably 30 μm or less. Can do. FIG. 2 shows the result of observation of the surface of each link inner part of the link chain treated by the polishing method according to the present invention with an optical microscope (magnification × 200). FIG. 2A shows the observation results of the elementary links polished before the heat treatment, and FIG. 2B shows the observation results of the elementary links polished after the heat treatment. As can be seen from FIG. 2 (a), in the pre-heat treatment polishing, even if there are protrusions on the surface of the raw link, the surface of the raw link is soft, so the polishing effect is sufficient and only a few protrusions are seen on the link surface. I can't understand. In addition, since the surface of the raw link is hard in the post-heat treatment polishing, the polishing effect is inferior. However, the burr height as shown in FIG. A link chain having an excellent surface roughness of 60 μm or less, preferably 30 μm or less as shown in FIG.

  In addition, the steps of employing the polishing method according to the present invention in the chain manufacturing process are as follows: 1) before heat treatment (before quenching / tempering treatment), 2) after heat treatment (after quenching / tempering treatment), 3) surface treatment (electroless plating) It has been found that any of the following steps is effective for removing or reducing the protrusions and improving the fatigue strength.

  A chain link chain of elementary link diameters 6.0 mm, 7.7 mm, and 11.2 mm is provided on the polishing tank of the vibration barrel polishing machine with a partition wall in the longitudinal direction (conveyance direction), for a total of 8 folding points Eight transport passages having a width of 8 are provided, and the link chain is placed in the transport passage with a certain degree of looseness. A link chain for 8 m was arranged in this tank. A chain feeding sheave is provided at the chain carry-in port, and a chain take-up sheave is provided at the chain carry-out port, so that the feeding and winding of both sheaves are synchronized and can be carried at a constant carrying speed. It is like that. The thus prepared link chain was subjected to a polishing process by applying vibrations of 30 Hz and an amplitude of 3 to 4 mm for about 2 hours and 3 hours. In this case, the conveyance speed is 0.04 to 0.07 m / min. The results are shown in Table 1. As can be seen from Table 1, in the polishing method according to the present invention, the inner surface of each link is polished to the extent that it is about 30 μm, and halved compared to before the polishing process, and the surface is smooth and harmless as a starting point of destruction. A simple link chain was obtained. As described above, by removing or reducing the protrusions, the effect is recognized even when the polishing method of the present invention is performed before and after the heat treatment and after the plating, and the improvement of the fatigue strength is also confirmed. Further, the polishing method of the present invention is a very effective means from the viewpoint of productivity, such as being capable of continuous processing, not in batch units.

It is a figure which shows the state of the processus | protrusion and burr | flash which arise in the boundary part of the parallel part and curved part of a raw link which have not performed the grinding | polishing process. (A) is a figure which shows the grinding | polishing surface of the elementary link before heat processing, (b) is a figure which shows the grinding | polishing surface after heat processing, (c) is a processus | protrusion, burr | flash at the time of grinding | polishing on optimal grinding | polishing processing conditions. It is a figure which shows the state of.

Claims (7)

After forming a low carbon alloy steel wire into a link shape using a mandrel consisting of an upper die and a lower die, the parallel and curved portions of each link of a chain-like link chain manufactured by welding the end faces together At the boundary, the protrusions and burrs generated due to the overlapping surfaces of the upper and lower mandrels are polished by a vibration polishing machine without using a polishing medium or fluid, and the protrusions and burrs are heightened. A link chain having a fatigue strength of 230 N / mm ² or more, characterized by being 60 μm or less . The link chain having a fatigue strength of 230 N / mm ² or more according to claim 1, wherein the protrusion and the burr height are 30 μm or less. A chain-like link manufactured by forming low-carbon alloy steel wire before quenching / tempering treatment or after quenching / tempering treatment into a link shape using a mandrel consisting of upper and lower molds and then welding the end faces together With the vibration polishing machine that applies vibration that rubs the links in a stationary state or in a transported state on the polishing tank and collides or beats the chain, the parallel parts of the individual links of the link chain are not used. 230 N / mm , characterized in that protrusions and burrs generated due to the overlapping surfaces of the mandrel composed of the upper mold and the lower mold are polished at the boundary of the curved section so that the height thereof is 60 μm or less. ^A method for manufacturing a link chain having a fatigue strength of ² or more. The method of manufacturing a link chain having a fatigue strength of 230 N / mm ² or more according to claim 3, wherein the vibration applied by the vibration polishing machine has a vibration frequency of 10 to 40 Hz and an amplitude of 1 to 6 mm. The link chain placed on the polishing tank and subjected to vibration polishing is a long link chain having a plurality of folded portions on the polishing tank, wherein the link chain has a length of 230 N / mm ² or more. A method of manufacturing a link chain having fatigue strength. The method for producing a link chain having a fatigue strength of 230 N / mm ² or more according to claim 3, wherein a polishing time of the long link chain conveyed on the polishing tank is 1 to 4 hours. 4. The method of manufacturing a link chain having a fatigue strength of 230 N / mm ² or more according to claim 3, wherein the link chain that has been plated after the quenching and tempering treatment is subjected to vibration polishing.