JPS5934770B2 - Hardening treatment method for steel bars with different diameters - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for quenching and hardening steel bars of different diameters whose cross-sectional shapes change sequentially in the longitudinal direction.

Different diameter steel bars, such as various shafts and various spindles such as spinning spindles, have parts that require wear resistance such as 5 bearings, and parts that are subjected to bending or torsional loads and require toughness. It is necessary to provide appropriate hardness. For this reason, the conventional hardening treatment method involves uniformly heating and cooling the entire surface using a heating means such as an electric furnace.
After uniformly quenching the entire body, a method is employed in which a medium-temperature tempering treatment is performed locally in order to impart toughness to the required areas, or a method in which the above-mentioned cooling is performed only at the required areas.
However, the above-mentioned conventional method has the disadvantage that a large amount of oxide scale is deposited on the surface due to long-time heating, which adversely affects post-processing.

In addition, the surface hardness of the tempered part naturally decreases, and the wear resistance decreases.Especially when applying hard chrome plating, applying heat treatment to the core to make it hard is likely to be affected by hydrogen embrittlement, and the impact value will decrease. There are various drawbacks such as a significant decrease in the performance.

The present invention has been made in view of this point, and the quenching process is carried out while rotating the spindle blade (while changing the quenching conditions sequentially from one side to the other), and the quenching process is performed while rotating the spindle blade (while changing the quenching conditions sequentially from one side to the other). It is an object of the present invention to provide a processing method for continuously forming a hardened layer of a required depth suitable for imparting wear resistance or toughness, and the present invention will be specifically explained below based on the drawings.

In the figure, the spindle blade 1 is supported at both ends by upper and lower bearings 21022 of the support means 2, with the top portion 11 facing downward, and the upper bearing 21 is connected to the rotating device 3, and is constantly maintained at a predetermined speed, for example, 300 to 500. , p-m. The support means 2 is fitted into a dovetail-shaped guide 42 formed on the front surface of the vertical rod 41 of the frame 4, and a feed screw 43 mounted parallel to the guide 42 is screwed together.
A belt 52 is stretched between the driven pulley 44 attached to the upper end of the feed screw 43 and the drive pulley 51 of the variable speed drive motor 5 attached to the upper end of the vertical rod 41, and as described later, the variable speed motor 5 supports the support means 2 via the feed screw 43.
That is, the blade 1 is raised and lowered at a predetermined speed. A high-frequency heating device is used as the heating means 6 for the flade 1, and includes an oscillating device 61, an output converting device 62, one end fixed to the device 62, and extending through the vertical rod 41 and the supporting means 2. The heating coil 64 is attached to the tip of the supporting arm 68 and corresponds to the blade 1. The coil 64 has a horseshoe shape or a shape as shown in FIG. It is preferable to use one having a semicircular arc structure.

In order to change the output of the coil 64 according to the grade 1 cross-sectional area and the wear resistance and toughness required for each part, the position of the coil 64 relative to the blade 1 is detected at the appropriate location. Means 7 is provided.

In the illustrated example, the drive belt 52 is rotated in conjunction with the feed screw 43, and a signal current is generated when a predetermined rotation speed is reached. It goes without saying that an appropriate sensing method may be used, such as engaging a protrusion provided on the support means 2 to detect the vertical position of the support means 2. This elevation position detection means 7 detects the blade 1 of the heating coil 64 as described above.
The position relative to the motor is detected by converting it into a rotational speed, etc., and when a predetermined position is reached, a signal current is generated and transmitted to the control device 8, which controls the rotational speed of the variable speed motor 5 and the heating device 6 according to a predetermined program. The output of the output conversion device 62 is adjusted. In the drawing, reference numeral 9 denotes a cooling water jetting nozzle for quenching, which is arranged and fixed directly below the heating coil 64.

Next, the quenching procedure will be explained based on FIGS. 2 and 8.

Part A, which includes the top 11 of Grade 1, is a part that requires toughness, and it has been found through experimental results that this purpose can be achieved by forming a hardened layer of, for example, 1 to 2 mtn only on the surface, so we reduced the output of the heating coil. increase (e.g. 5
0KHZ. 6 to 7 A, 11 to 12 KV (The figure in parentheses indicates one example) Increase the transfer speed of the blade 1 (15 to 18
7Wff1/sec) to make only the surface reach a predetermined hardening temperature, and the surface that has reached the predetermined hardening temperature is rapidly cooled.

This provides high surface hardness, provides wear resistance and prevents hydrogen embrittlement during plating, and maintains sufficient internal toughness. Next, the high frequency current voltage of the heating coil is lowered (50 KHz.
4-5 A, 7.5-9 KV) The transfer speed of the blade 1 is slowed down (4-8 mm for 1 second) to reach the quenching temperature completely and uniformly down to the core, and then rapidly cooled.

This provides tensile strength and wear resistance against external forces. Next, the distance D from the bottom to the step bearing part E
For the section, increase the current voltage again (50KHZ, 6A)
Front and rear, 11-12Kv) Increase the transition speed of blade 1 (
15 to 18 mm/sec) Only the surface is hardened, and the transition speed is slowed down for the lower end E portion of the step bearing part 13 where the most hardness is required in order to obtain wear resistance and rolling fatigue resistance. (4 to 5 mm/sec) lower the current voltage (
50KHZ, 4~5A17~8KV) After reaching a completely uniform quenching temperature down to the core, it is rapidly cooled. The hardened layer T of the blade 1 hardened by the above method becomes as shown in FIG.

The mesh portion in the figure is the hardened layer. In this case, as is clear from the drawings, the boundaries between different depths have smooth steps due to continuous quenching, and no breakage or cracks occur at the steps. Although this embodiment shows a method in which the heating coil 64 is fixed and the spindle plate 1 is vertically supported to move it up and down, it is of course possible to fix the blade 1 and move the heating coil 64 up and down. 1 may be supported horizontally, and the blades or heating coils may be moved from side to side, or flame hardening may be used as the heating device, and other changes may be made without departing from the spirit of the present invention.

As described above, the present invention sequentially hardens the blade 1 from one side to the other while selecting hardening conditions to form a hardened portion up to the core and a hardened layer only on the surface leaving the core. Since the required wear resistance and toughness required for each part of the blade are obtained in one process, the partial tempering process can be omitted, shortening the heat treatment time and reducing the manufacturing cost. This prevents a decrease in hardness and the generation of surface oxidation scale due to the tempering process, and the hard chrome plating part (part A) can have the required hardness only on the surface, which prevents hydrogen embrittlement caused by chrome plating. can prevent the negative effects of Furthermore, according to the present invention, since the blade is rotated (quenched), a uniform hardened layer can be obtained in the radial direction.
Furthermore, since the quenching conditions are changed sequentially and quenching is performed continuously, even if there are differences in the hardened layer and chestnutness of each part, the steps are smooth and breakage or cracks do not occur at the boundary of depth. It has a number of effects, such as the absence of

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an apparatus for carrying out the method of the present invention, and FIG.
The figure is an explanatory view of the main parts, and FIG. 3 is a longitudinal cross-sectional view of a spindle blade that has been hardened by the method of the present invention. 1... Spindle grade, 2... Support means, 6.
... Heating means, 7... Lifting position detection means, T... Hardened layer.

Claims (1)

[Claims] 1. In the quench hardening treatment of steel bars of different diameters, rotation is applied to the steel bars, and the quenching treatment is performed continuously from one side of the steel bar to the other, and the rotation speed and quenching conditions of the steel bars are adjusted for each part of the steel bar. A method for hardening a deformed steel bar, characterized by selectively and sequentially changing the depth to successively form hardened layers with different depths.