JPS5823812B2 - Manufacturing method of steel quenched piston ring - Google Patents

Description

[Detailed Description of the Invention] Conventionally, pressure rings and the like attached to the pistons of white-fired engines were manufactured from cast iron, but recently, for the purpose of improving strength, they have been replaced with steel rings made of drawn or rolled steel. A review is underway.

The present invention relates to a hardened steel piston ring obtained by improving the forming method in order to process this type of ring economically and to obtain a product with accurate dimensions and shape.

Generally, to form rings, one method is to cut a piece of material a according to the diameter of the ring in advance as shown in Figure 1, and then wind it with a ring winding machine as shown in b, or with a long material and one turn with a ring winding machine. A method of continuously supplying material by cutting the ring once it has been wound and then winding the next ring.

Also, as shown in Figure 2, during ring bending, the material was wound into a tendril shape as shown in d, and one end of the material was later cut out as shown in C to form a ring shape.

However, most of these processes have conventionally been carried out by cold-forming pre-quenched steel, which makes it difficult to wrap and form materials with very high hardness and tensile strength. It was limited to HRc of 45 or less (tensile strength of 150 kg/- or less).

Therefore, HRc 45-60 (tensile strength 150 kg/mm
For high-strength rings that reach ~240 kg/mA), the material is annealed in advance to sufficiently reduce its hardness, cold-processed into a ring shape, and then heated to quench and temper. It was given a certain strength.

In the case of such processing, if the material is cold-formed from a material that has been quenched and tempered in advance, if it is subjected to various machining processes after ring forming, deformation will occur due to residual strain caused by bending, so accuracy cannot be guaranteed. In the latter case, when the annealed material is heat treated (quenched) after forming, distortion due to heating and quenching distortion may occur, which may affect the roundness and other dimensions of the ring. The shape deteriorates and the yield drops significantly.

Items with a large cross-sectional area that are difficult to bend are often heated to around 700°C to 750°C to form a ring, and then heated again to the standard quenching temperature for heat treatment (quenching and tempering). However, in this case, the purpose is simply to increase the material temperature to make the material easier to work with, and in most cases the material is in a ferritic state.

After the ring is formed, it is once cooled and then reheated to perform the heat treatment of quenching and tempering, resulting in the same problem of shape defects due to heating and quenching distortion as in the latter case.

Furthermore, when processed by heating to high temperatures, the shape of the main material deforms, making it generally difficult to maintain accuracy.

This has been a problem mainly when considering switching parts in which cast products are used, such as pressure rings for automobile engines, to hardened steel rings.

The present invention is suitable for manufacturing individual rings by heating and ring-bending a drawn or rolled steel material in the form of a wire or strip, and for continuous ring-forming into a spiral shape such as a coil spring. An object of the present invention is to provide a method for manufacturing a hardened piston ring having high hardness.

The present invention involves the step of selecting the temperature at which the material is heated for the above-mentioned steel quenched piston ring. Step 1 of bending a ring of the heated material within the quenching temperature range of the material. By combining the process of rapidly cooling the ring while it is held in a bending jig immediately after the ring bending process, all functions are included in each process to manufacture piston rings for use in automobiles, etc. The ring is subjected to a tempering process.

Furthermore, in order to specifically clarify the difference between the present invention and the conventional method, 2-
Comparing with 3 examples, conventional forming method example (1) Material → pultrusion or roll forming → strain relief annealing → heating → quenching → tempering → final forming → cold swing forming → shape modification Example of the above 8 steps (2) Material → Drawing or roll forming → strain relief annealing → final forming → cold ring forming → heating → quenching → tempering → shape correction Shape Modification Tempering The above 4-step conventional forming method example (1) requires 8 steps, and since the above-mentioned cold ring forming is particularly performed in the final step, the ring hardness must be limited to approximately HRc45 or less to be commercialized.

Further, when cold molding is performed, the ring undergoes springback within the range of elastic deformation, making it difficult to ensure dimensional accuracy.

Conventional forming method example (2) also requires 8 steps, and the amount of springback during ring forming is less than f[), but the shape changes due to thermal distortion during heating, quenching, and tempering processes, and distortion due to structural changes in the steel material. Therefore, it is difficult to ensure the accuracy of the dimensions and shape.

In the example of the present invention, the ring forming process can be shortened to four steps.

The material is drawn or roll-formed into a strip of steel, which is then heated, but the heating temperature must be higher than the quenching temperature of the material.The material heated to this temperature is introduced into a ring forming machine. The inlet guide serves as a final forming device for the material shape.

After that, it is introduced into a ring winding machine and is machined and formed at a high temperature higher than the quenching temperature. After the forming is completed, it is mechanically restrained and held in its shape. 3. It is then quenched with a mist of oil or water, if necessary, to perform quenching. .

After the ring completes its multisite transformation and is quenched and hardened, it is removed from the device in which it was held.

As described above, the piston ring manufactured by the method of the present invention is formed into a ring, and is quenched and hardened at a high temperature while maintaining its shape. Therefore, the size and shape can be maintained accurately, and a piston ring with arbitrary hardness can be obtained. It has the following characteristics.

In the method of the present invention, if the ring shape has a large thickness in the direction of the center axis of the ring and a small width in the diametric direction, the ring shape can be maintained without any problem, but in the case of so-called edgewise winding where the thickness is small and the width is large. Although the "sag" and "warp" of the shape are improved compared to conventional cold ring forming, there are some difficulties in obtaining a ring that completely prevents these defects. .

As variously explained above, the present invention, in manufacturing a steel quenched piston ring, heats the material to a quenching heating temperature range, performs ring forming processing at that temperature, and then mechanically restrains the ring without removing it from the apparatus. A ring with accurate dimensions and shape is manufactured by rapidly quenching and hardening the ring in the same condition. After quenching and hardening, the ring undergoes the necessary processing and is then fixed to a jig and tempered. The shape can also be corrected during this tempering process. This will be implemented in

Piston rings manufactured by such a series of ring molding methods are accurate to desired dimensions, and the effect of efficiently molding pressure rings and oil rings with high hardness is remarkable.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic diagram of manufacturing a conventional steel piston ring. FIG. 2 is a schematic diagram of manufacturing a helical piston ring.

Claims (1)

[Claims] 1. Bending and forming the band material into a ring shape at or above the quenching temperature, and at the same time or immediately after forming the ring, quenching and hardening it by rapidly cooling the ring shape while mechanically restraining it, and tempering the ring. A method of manufacturing a hardened steel piston ring, which is characterized by mechanically constraining the shape.