JP2572238B2 - Inner and outer peripheral surface hardening method for small bore cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) In the present invention, when forming a hardened hardened layer on the inner and outer peripheral surfaces of a cylindrical body, the inner diameter of the cylindrical body is small. The present invention relates to a method for quenching the inner and outer peripheral surfaces of a small-diameter cylindrical body to cope with a case where it is difficult.

(Prior art and problems) In a cylindrical body such as a bush, it is desirable to form a quenched hardened layer on the inner and outer peripheral surfaces of the cylindrical body and not to harden the core in order to maintain strength and toughness.

However, many of these types of cylinders are small, for example, if the inner diameter is 35 mm or less, it becomes difficult to manufacture a heating coil to be opposed to the inner peripheral surface. In addition, since the steel tube is heated to a predetermined quenching temperature in an electric furnace or the like, then rapidly cooled and quenched, the entire cross-section of the cylinder wall becomes a hardened hardened layer, and the toughness must be reduced.

Therefore, although measures for reducing the toughness have been conventionally sought, they have reached today without creating effective measures.

(Object of the Invention) The present invention has been made in order to solve the above-mentioned problems existing in the conventional heat treatment method for a small-diameter cylindrical body. It is an object of the present invention to provide a method of hardening the inner and outer peripheral surfaces of a small-diameter cylindrical body capable of forming a quench hardened layer having a desired depth and adjusting the depth of the quench hardened layer.

(Summary of the Invention) The gist of the present invention is as follows: (1) The entire cross section of the cylindrical wall of the cylindrical body is heated by a heating means capable of
(2) Then, while cooling the entire inner peripheral wall of the cylindrical body with a controlled flow rate of the cooling fluid, (3) connect the outer peripheral surface of the cylindrical body to a high-frequency power source having a predetermined frequency and output. (4) When the outer peripheral surface layer is heated to a predetermined quenching temperature, the outer periphery is rapidly cooled with a controlled flow rate of a cooling fluid when the outer peripheral surface layer is heated to a predetermined quenching temperature. There is a method of hardening around the surface.

(Operation of the Invention) The present invention forms a hardened hardened layer having a desired depth on each of the inner and outer peripheral surfaces of a small-bore cylindrical body in which it is difficult to manufacture a heating coil to be opposed to the inner peripheral surface, and has a tough core. It has the effect of making the refining tissue rich.

(Example) The present invention will be described in detail below.

In the present invention, as a first stage treatment, the entire cross section of the cylindrical wall of the cylindrical body is a quenched and hardened layer. In this case, the type of the heating means is not limited as long as the heating means can raise the entire cross section of the cylindrical wall to a predetermined quenching temperature. For example, a heating coil that can be opposed to the outer peripheral surface of the cylindrical body with a predetermined gap therebetween, furnace heating, or the like may be used as the entire wall heating means of the cylindrical wall. The cylinder wall of the cylinder subjected to the first-stage treatment is shown in a schematic hardness distribution diagram of FIG. 1 in which the vertical axis represents hardness (HRc) and the horizontal axis represents the cylinder wall cross-sectional dimension. As can be seen, the entire cross section becomes a hardened and hardened layer.

Next, the cylinder is subjected to a second stage of processing using the apparatus shown in FIG. In the figure, W is a cylinder, J is a cooling jacket inserted into the cylinder, and C is a heating coil.

In the cylindrical body W, the hardened layer is indicated by the double oblique line H, and the entire cross section of the cylindrical wall is the hardened layer.

The cooling jacket J is a cylindrical member having an outer periphery capable of opposing the inner peripheral surface of the cylindrical body W at a predetermined interval and a length capable of opposing the entire inner peripheral surface at a predetermined interval. A cooling fluid injection hole as shown is provided, and a cooling fluid can be supplied through a pipe P into the cylinder. Therefore,
The cooling fluid is ejected from the cooling fluid ejection holes s and can hit the entire inner peripheral surface of the cylindrical body W.

The heating coil C is relatively movable with respect to the cylindrical body W and the cooling jacket J according to the arrow, and includes a heating conductor c on the front side in the moving direction and a cooling jacket j for quenching on the rear side. . The heating conductor c is connected to a high-frequency heating power supply indicated by E, and is formed to have a predetermined width and an inner peripheral diameter opposed to the outer peripheral surface of the cylindrical body W with a predetermined gap therebetween. The cooling jacket portion j is connected to a pipe line (not shown) connected to a cooling fluid supply source for quenching, and is configured to be capable of injecting the cooling fluid to the outer peripheral surface of the cylinder W at the rear in the moving direction.

Thus, the flow rate of the cooling fluid injected from the cooling fluid injection holes s of the cooling jacket J is set to a predetermined value, the power source E is selected to have a predetermined frequency and output, and After setting the moving speed to a predetermined value and setting the flow rate of the quenching cooling fluid injected from the cooling jacket j to a predetermined value, the second stage processing is executed.
Note that the processing in the second stage is preferably performed while the cylinder W is being rotated, and in this case, known means is used.

In the processing of the second stage, the heating conductor portion c of the heating coil C sequentially raises the temperature of the opposed outer peripheral surface layer of the cylindrical body W to a predetermined quenching temperature within a heating time determined in accordance with the relative moving speed and the width thereof, and cools. The jacket j sequentially quenches and quenches the heated portion, while the heat of the outer surface heating portion of the cylinder W moves toward the core of the cylinder W by heat conduction. By the way, the inner peripheral surface of the cylindrical body W is the cooling jacket J as described above.
Is being cooled by the cooling fluid having a controlled flow rate injected from the cylinder W, and the conduction heat is lost without reaching the inner peripheral surface of the cylindrical body W. Accordingly, as shown in FIG. 3, the quenched and hardened layer indicated by the double hatched portion h is reformed on the outer peripheral surface side of the cylindrical body subjected to the second stage processing, and the inner peripheral surface is formed. The hardened layer H formed in the first stage is preserved as it is on the side, and the hardened layer H formed in the first stage has a core portion sandwiched between the hardened hardened layers h and H on the outer and inner peripheral surfaces. Transforms into a tempered structure R that is softened and stippled by heat conduction.

As is known, the tempered structure R is rich in toughness,
The intended purpose is achieved.

(Specific Examples) Some of the examples of the present invention will be disclosed below as specific examples.

☆ Implemented cylinder: Material; S53C equivalent material Dimensions; Outer diameter …… 41mmφ Inner diameter …… 24mmφ (Wall thickness …… 8.5mmφ) Length …… 88mm After raising the temperature to the quenching temperature, the entire cross section was rapidly cooled and quenched. The heating conditions are shown below for comparison with and reference to the first-stage treatment described below.

Power frequency: 6KHz Output: 200KW Inner diameter of heating coil: 60mmφ 2nd stage processing: ○ Cylinder inner surface cooling condition; Cooling fluid …… Water flow rate… 3.5 / min ○ Cylinder outer surface heating and cooling condition; However, the heating coil C is moved relatively to the cylinder.

Heating power frequency: 30KHz Output: 100KW Heating coil c Inner diameter: 50mm Width: 10mm Cooling jacket j Cooling fluid: Water supply Flow rate: 1.5 / min Relative moving speed: 8mm / sec ☆ Accuracy test: The cylinder subjected to the first stage treatment and the cylinder subjected to the first and second stage treatments were each subjected to a hardness measurement test. The test results are shown in FIG. In the figure, a curve A is a hardness distribution curve after the first-stage processing, and a curve B is a hardness distribution curve of the entire cross-section of the cylinder wall obtained from the measured values of the cylinder after the first and second-stage processing. In addition, hardness is represented by Vickers hardness Hv,
It indicates that 450 lines or more are quenched and hardened layers.

From FIG. 4, it can be seen that hardened hardened layers H and h are formed at a depth of 2.5 mm on the inner and outer peripheral sides, respectively, and that the hardened hardened layer H formed by the first stage treatment is formed. Was softened through the second-stage treatment, indicating the hardness of the tempered tissue R.

(Other embodiments) In the above embodiment, the inner and outer peripheral sides of the cylindrical body are 2.5 m each.
The example of forming the quench hardened layers H and h with a depth of m has been described above.
By changing conditions individually or in combination, such as changing the output, changing the relative moving speed of the heating coil C, changing the width of the heating conductor c in the heating coil C, and changing the flow rate of the cooling fluid injected from the cooling jacket j. The depth of each of the hardened and hardened layers H and h can be adjusted as desired within a range of 1 to 4 mm.

Also, the values of the respective heating / cooling conditions, the relative moving speeds, and the like in the second stage processing described in the above embodiment can be changed depending on the thickness of the cylindrical body.

In the embodiment, for the sake of simplicity, the cylinders are subjected to the second stage processing one by one. However, in practice, a plurality of cylinders are connected in series in an end contact state, and a plurality of cylinders are connected. A cooling jacket J for cooling a long inner peripheral surface in a cylinder that extends over the entire length of the body
, And the heating coil C is sequentially moved from one side to the other side, thereby improving processing efficiency.

Although the embodiment employs the moving quenching method in which the heating coil C is relatively moved with respect to the cylindrical body, if the length of the cylindrical body is relatively short and the output of the power supply used is large, the heating coil section c and the cooling jacket are used. The heating coil C comprising the heating coil C having a width opposed to the entire length of the cylindrical body and a cylindrical cooling jacket are used for the heating coil C. For example, the axes of the heating coil and the cooling jacket are on the same straight line. As described in (1), the heating coil may be opposed to the cylinder and one-shot heating may be performed for a predetermined time, and then the cooling jacket may be opposed to the cylinder by relative movement to perform one-shot cooling.

(Effect of the Invention) The method of the present invention ensures the required abrasion resistance to the inside and the outer peripheral surface of the cylinder, and enhances the strength of the cylinder itself by forming the core portion into a toughened and tempered structure. Greatly improved,
In addition, since the tempering step conventionally performed as a pretreatment for quenching is omitted, the effect to be achieved is awarded as being extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic hardness distribution diagram of a cylindrical tube wall after a first stage process in the method of the present invention, FIG. 2 is a sectional front view showing a second stage process in the method of the present invention, and FIG. FIG. 4 is a hardness distribution diagram showing the results of a hardness measurement test of the cylindrical wall of the cylindrical body after the two-stage processing.

Claims (1)

(57) [Claims] When forming a quenched and hardened layer on the inner and outer peripheral surfaces of a cylindrical body, it is difficult to manufacture a heating coil to be opposed to the inner peripheral surface because the inner diameter of the cylindrical body is small. The entire cross section is heated and quenched by a possible heating means to form a quenched hardened layer, and then, while cooling the entire inner peripheral wall of the cylinder with a cooling fluid having a controlled flow rate, the outer peripheral surface of the cylinder has a high frequency of a predetermined frequency and output. The small-diameter cylindrical body is characterized in that the heating is performed for a predetermined time by a heating coil connected to a power source, and the outer periphery is rapidly cooled with a controlled flow of a cooling fluid when the outer peripheral surface layer rises to a predetermined quenching temperature. Inner and outer surface quenching method.