JPH021207B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hardening control method suitable for surface hardening the hole walls of a member having holes unevenly distributed from the center of the member.

[Conventional technology]

By quenching and hardening the surface of uneven thickness parts that have large mass parts and small mass parts, the small mass parts have the same high toughness as the large mass parts, and the quenching process imparts wear resistance. Although cooling is an essential requirement, the conventional hardening method that simply combines an induction heater and a cooler is not suitable for uneven thickness parts where the shape and mass around the back of the part to be hardened is different.
In cases where the objective cannot always be satisfactorily achieved, and the hardening depth and hardness are uneven, and the thickness is extremely uneven, that is, when the hole wall of the hole D of the member W shown in Fig. 1 is hardened. As shown by the diagonal line H, surface hardening is considered unsuitable because the soft structure of the base metal is lost and extreme unevenness occurs. was.

[Problem to be solved by the invention]

However, carburizing requires extremely troublesome pretreatment and takes several hours, resulting in poor productivity.Therefore, there has been a desire to develop an efficient alternative treatment method.

The present inventor considered the reason why conventional methods of hardening are unsuitable for members with uneven thickness, and found that when surface hardening is applied to the walls of holes that are unevenly distributed from the center of the member, When the mass of the portion behind the hole wall is different, and therefore the heat capacity in each direction of the member is different, even if the amount of heating for the entire surface of the hole wall is constant, the mass of the rear portion of the hole wall is different. Since the degree of heat conduction around the hole wall surface differs significantly due to the difference in the temperature, the widening portion that reaches the high temperature state necessary for quenching is biased. FIG. 2 schematically illustrates this state. That is, as shown by the length and thickness of the arrows in FIG. 2, the heat conduction in the radial direction from the periphery of the hole wall is distributed non-uniformly and asymmetrically. Large mass part W from the hole wall
The heat conduction to 1 is as shown by the length of the arrow,
On the contrary, heat conduction to the small mass portion W2 directly reaches the end face and is blocked. Therefore, as the temperature rises, heat is accumulated at the side edge portion of the small mass portion W2, so as indicated by the thickness of the arrow, the temperature reaches the quenching temperature relatively quickly, but the large mass portion W1, on the contrary, reaches the quenching temperature.
Heat is diffused and delayed. This difference is due to the small mass part W
Even if the temperature around 2 rises to the quenching temperature, the large mass part W
1 is not heated to the quenching temperature to a predetermined sufficient depth range, and conversely, if the large mass part W1 is heated to a predetermined sufficient depth range, the small mass part W2 is in an overheated state. invite. Therefore, if the entire range of the small mass part W2 is heated to the quenching temperature as shown in Fig. 1, the soft structure of the base material that provides toughness to the part after quenching will not remain, and the non-formal structure of the small mass part W2 will not remain. If it is attempted to leave the hardened portion, the side edge portion on the side of the large mass portion W1 will be insufficiently hardened.

Differences in thermal stress and transformation stress caused by different temperature rise ranges from the hole wall tend to cause various types of distortion, and in severe cases, lead to inconveniences such as quench cracking and loss of toughness in the area. . It is clear that the most important cause of uneven firing is the difference in heat capacity between the large mass portion W1 and the small mass portion W2.

The present invention has been made in order to solve the above-mentioned conventional problems. It is an object of the present invention to provide a heat-controlled hardening method that makes it possible to uniformly surface harden the hole walls while leaving the material structure intact.

[Means to solve the problem]

In order to achieve the above object, the present invention extends a portion of a large mass portion located behind the hole wall that is slightly separated from the hole wall over the entire cross section of the portion in the width direction of the member, depending on the size of the mass. After heating to a predetermined temperature within the temperature range from 200°C to the transformation temperature to prevent the amount of heat during surface hardening of the hole wall from diffusing to the large mass part by heat conduction, The structure is such that the surface of the hole wall is uniformly hardened, leaving an unhardened portion in a small mass portion including the periphery of the hole wall and up to the side edge of the member.

[Effect]

In the present invention, before hardening the hole wall of the part to be hardened, a part of the large mass part existing at the back of the hole wall, which is slightly separated from the hole wall, is measured according to the size of the mass. After heating to a predetermined temperature across the cross section in the direction to form a thermal weir, the surface of the hole wall is hardened, so the thermal weir suppresses heat diffusion to large mass parts during hardening. This makes it possible to uniformly harden the hole wall, leaving an unhardened portion in the small mass portion.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 3a, 1 is an induction heater supported so that it can be raised and lowered by a support device (not shown), 2 is a heating controller supported movably by a movable support device (not shown), and W is a This is a material to be quenched supported by a support device (not shown). Hardened material W
As shown in Fig. 3b, it is a plate-shaped uneven thickness member in which a portion is formed with a relatively very thin wall part due to unevenly distributed holes D at the other end, and is used, for example, as a lever, etc. The wall surface of the hole D is the surface to be hardened.

A coil-shaped induction heater 1 is installed in the hole D of the material W to be quenched.
can be inserted, and the induction heater 1 is connected to a high frequency power source E1. Heating control heater 2
is located at the back of the hole D of the material W to be quenched, which is slightly apart from the hole D in the longitudinal direction.
It is disposed in a circular manner so that it can be heated to a predetermined temperature over a cross section perpendicular to the cross section, that is, a cross section in the width direction of the member, and is connected to a power source E2 having a frequency lower than that of the power source E1.

In this configuration, when quenching the material W to be quenched as shown in the figure, first, the heat conduction is not uniformly distributed due to the uneven distribution of the mass of the hole D of the quenched material W with respect to the material to be quenched. Then, the heating control heater 2 is positioned at a predetermined position with high thermal conductivity, and the heating control heater 2 is energized from the low frequency power source E2 for a predetermined time, and the transformation starts from 200°C depending on the mass of the positioned part. The thermal weir S is formed by heating to a predetermined temperature within a range of up to Next, the induction heater 1 is inserted into the hole D of the material to be quenched W, and electricity is applied to the induction heater 1 from the high frequency power source E1 to harden the wall surface of the hole of the material to be quenched W.

In this way, the large mass part W with large heat capacity
1, a thermal weir S is formed in advance to prevent the amount of heat during quenching from dispersing through heat conduction, so the hole wall is uniformly heated over the entire circumference and then cooled. As a result, as shown in FIG. 3b, a thin hardened layer H having a uniform depth over the entire circumference is obtained.

The present invention introduces the formation of a thermal weir as a new principle in order to control quenching heating.It is a large mass part that is connected to the cylinder to be quenched and has a large temperature drop due to thermal diffusion, in other words, it is difficult to increase the temperature. A thermal weir is formed in W1, and the large mass part W1 is adjusted according to the temperature rise of the small mass part W2.
Heating is controlled over the entire cross section of a predetermined portion. This principle, as shown in FIG. 3b, very effectively uniformizes the hardening layer around the area to be hardened. for example,
It is possible to achieve a hardening depth accuracy of 0.05 mm to 2 mm, especially 0.1 mm, and as mentioned above, in the small mass part W2, where quench hardening easily occurs in the entire area in the conventional method, a flexible matrix is applied to the outer edge of the hardened layer. It is possible to convey the strength and wear resistance of the member after quenching while preserving the material structure.

〔Example〕

Next, the test results (5th
Figure) will be explained. In the figure, △ marks indicate the installation positions of the heating control heaters 2.

(1) Test piece Dimensions: 150mm x 34mm x 20mm Hole diameter: 20mmφ Material: S45C (2) Induction heater Number of turns: 3.5 turns, outer diameter: 17mmφ Power source E1: 200KHz, 80Kw (3) Heating control heater Number of turns: 1 Turn, power supply E2: 30KHz, 80Kw (4) Heating/quenching conditions Heating conditions using a heating control heater Voltage: 8.0KV, current: 6.0A Grid current: 0.5A, heating time: 7sec Quenching conditions using an induction heater Voltage: 11.6 KV, current: 6.3A Grid current: 0.3A, heating time: 3.5sec Cooling time: 8sec (5) Test results
It shows the internal hardness distribution along the direction of the arrow from the hole wall of hole D in B and C.
It is understood that a thin hardened layer with a substantially uniform depth is formed over the entire circumference of the hole wall.

〔Effect of the invention〕

As explained above, the present invention deals with the uneven heat conduction distribution of the amount of heat during hardening around the part to be hardened.
By forming a thermal weir at the part to be quenched, the temperature during quenching heating can be controlled according to the temperature rise of the small mass part, so it is possible to maintain uniform and stable heat conduction around the part to be quenched. This makes it possible to harden the surface layer of the part to be hardened as desired and precisely.
Furthermore, it is also possible to maintain toughness in the member by leaving a non-hardened part even in a small mass part. the result,
Hardening treatment can now be applied to uneven thickness parts for which a satisfactory finish could not be obtained with hardening treatment, and it is possible to perform finish hardening with higher precision than before. There are advantages that can be obtained through simple operations.

[Brief explanation of drawings]

Fig. 1 is a front view showing the hardened layer when hardened by the conventional hardening method, Fig. 2 is a front view showing the state of heat conduction in Fig. 1 with arrows, and Fig. 3a is a front view showing the hardened layer when the present invention is implemented. FIG. 3b is a diagram for explaining the effects of the present invention, and FIGS. 4a and b are plan views of test pieces used in experiments of the method of the present invention, respectively. and a side view, and FIG. 5 is an internal hardness distribution diagram showing the test results of the above experimental example. 1...Induction heater, 2...Heating control heater, W
...Material to be quenched, W1...Large mass part, W2...Low mass part, D...Hole, H...Hardened layer, S...Heat weir.

Claims (1)

[Claims] 1. When surface hardening a hole wall with holes unevenly distributed from the center of a member made of carbon steel using induction heating means, a portion slightly separated from the hole wall in the large mass part existing behind the hole wall. is heated to a predetermined temperature within the temperature range from 200℃ to the transformation temperature over the entire cross section in the width direction of the part according to the size of the above mass, so that the amount of heat during surface hardening of the hole wall is increased. After making it possible to prevent heat from diffusing to the large mass part by conduction, the surface of the hole wall is uniformly hardened, leaving an unhardened part in the small mass part including the periphery of the hole wall and up to the side edge of the member. A heat-controlled quenching method characterized by: