JPS6369913A - Strengthening apparatus for surface of steel part - Google Patents

Abstract

PURPOSE:To effectively and efficiently execute the surface strengthening method for steel part, by shifting the steel part as holding by a holding means at the prescribed position, cooling it to the prescribed temp. after high frequency induction heating and further executing shot peening working and quenching cooling. CONSTITUTION:In a surface strengthening apparatus 5, the steel part 1 for working material is held by a jig 2 of the holding mechanism 2 and ascended in an upper room 10a of a hausing 11 by driving a lifting cylinder 14 in a driving mechanism 3. Here, while rotating the steel part 1 by driving an induction motor 19, the steel part is heated by the high frequency induction heating mechanism 9 through a high frequency coil (not shown in the figure) held by the holding member 6' at the prescribed quenching temp. Next, the steel part 1 is descended to a middle room 10b and cooled to the temp. of metastable austenite range by forced cooling means 39. After that, the shot peening working is executed to the above steel part by a shot grain injecting mechanism 4. Further, the above steel part 1 is quenched by cooling to near the room temp. as continuing before, under and after shot peening working.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a surface strengthening device used to strengthen the surface of steel parts.

b. Prior Art Steel parts and the like have traditionally been treated to strengthen their surface portions in order to improve their fatigue strength. When surface strengthening treatment is performed, a large compressive residual stress is generated on the surface and subsurface portions of the steel component, and this compressive residual stress, together with the reinforcement layer on the surface portion, contributes to improving the fatigue strength of the component.

Methods for performing such surface strengthening treatment include various methods using heat treatment, surface strengthening cold working methods, and processing heat treatment methods that combine working and heat treatment. An example of a heat treatment method is induction hardening.

There are fire hardening methods, carburizing hardening methods, nitriding methods, etc., and these treatments are performed as appropriate depending on the usage conditions and purpose of the steel parts. In addition, as a surface strengthening cold working method,
There are surface rolling methods, shot peening methods, etc. Furthermore, there are various combinations of processing heat treatment methods that combine processing and heat treatment, but the ausforming method is the most important and is representative of the processing heat treatment.

As mentioned above, various methods have been put into practical use as surface strengthening methods for improving the fatigue strength of steel parts.

However, although the surface heat treatment method and the cold working method have many practical advantages, they have the disadvantage that fatigue strength is inferior to the above-mentioned heat treatment method.

On the other hand, a heat treatment method represented by the ausforming method is a method of significantly increasing the fatigue strength of steel by organically combining plastic working and heat treatment. In other words, the ausforming method is a processing method in which austenitized steel is rapidly cooled to the metastable austenite eTJ region of the isothermal transformation diagram, processed at that temperature, quenched to cause martensitic transformation, and then tempered. It is. According to this method, steel parts are significantly strengthened without much loss of toughness, so this ausforming treatment method is considered to be the most excellent treatment among thermomechanical treatments.

Problems to be Solved by the C8 Invention However, the ausforming method described above also has major drawbacks. In other words, in order to apply ausfform treatment to steel parts, the steel parts are processed into metastable austenite, and rolling with rollers is usually used for this processing, so steel parts with complex shapes are processed. It is difficult to perform strong processing on steel parts, and the reality is that only plate-shaped steel parts can be processed.

Although any processing method may be used, the current situation is that there is no suitable processing method that performs strong processing other than rollability.

In addition, we can transform austenitized steel into pearlite transformation.
It must be rapidly cooled to the metastable austenite region in as short a time as possible without reaching the noseco region. This metastable region of austenite varies considerably depending on the type of steel material, but in order to perform ausforming, it is advantageous for the transformation curve to be on the long time side as much as possible. For this reason, the steel type currently targeted for ausform is Ni.

These are various alloy steels containing Cr, Mo, W, V, etc., and in order to exhibit the orthoform effect, it was necessary to use expensive alloy steels containing a large amount of these alloy elements.

As described above, there are two major problems with the orthoform processing as described above.

Therefore, in order to solve this problem, one of the applicants of the present invention has proposed a method of "heating the surface layer of steel parts to make them austenitic", in order to solve these problems. MS point ~ 600 at a cooling rate that does not affect the nose of pearlite transformation by self-cooling or forced cooling
℃, and then the surface layer in the metastable austenite state is subjected to plastic working or is cooled to below the M5 point, thereby imparting an ausform effect to the surface layer of the steel part. We proposed a surface strengthening method for steel parts.

The main object of the present invention is to provide a surface strengthening device suitable for carrying out the above-mentioned "method for strengthening the surface of steel parts" effectively and more efficiently.

d0 Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides: <A> a steel part holding means for holding a steel part as a workpiece; and <B> a means for holding the steel part as required. a high-frequency coil that performs high-frequency induction heating to a quenching temperature; (C) a shot particle projection mechanism that performs shot peening on the steel component; and (D) a shot particle projection mechanism that arranges the steel component so as to correspond to the high frequency coil and the shot particle projection mechanism. and a steel parts drive mechanism that moves the steel parts arranged correspondingly to the steel parts; (F) a quenching cooling means that cools the steel part to around room temperature for quenching before, during, or after the shot peening process; I am trying to set it up.

Note that in this specification, the cooling means referred to in the above item <E> includes not only a specially provided forced cooling device but also a means for natural cooling.

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

FIG. 1 schematically shows the configuration of a device for strengthening the surface of steel components. A device main body 5 having a shot particle projection mechanism 4 etc., and a third
As shown in the figure, a coil holding member 6' for holding a high frequency coil 6, a high frequency induction heating mechanism 9 consisting of a coil lead 7 and a high frequency transformer 8 are each provided.

The device main body 5 described above has a chamber 10a divided into three stages.

Vertical robust housing 11 with 10b and 10c
A central opening 12a is formed in the partition wall 12 above the housing 11. A steel component holding mechanism 2 is installed on the partition wall 13 below the housing 11, and the housing 11 is connected to the holding mechanism 2.
A steel parts drive mechanism 3 is disposed in the lower chamber 10c. That is, the drive mechanism 3 includes an elevating cylinder 14, a plate-like member 15 that is moved up and down by the elevating cylinder 14, a drive shaft 16 that is vertically and rotatably attached to this plate-like member 15, and this drive shaft. 16, and an induction motor 19 that applies rotational force to the drive shaft 16 via a rotational force transmission mechanism 18 consisting of a belt, a pulley, etc. The shaft 16 is rotatably inserted through the bearing portion 20 of the steel component holding mechanism 2, and its tip is connected to the steel component holding jig 21.

Further, the above-described shot projection mechanism 4 is disposed on the side wall 11a of the middle chamber 10b of the housing 11.

The shot particle projection mechanism 4 of this example is of a centrifugal force type, and includes a shot particle supply source 23 , a shot particle supply pipe 24 , and a side wall 11 of the housing 11 connected to the shot particle supply source 23 and a shot particle supply pipe 24 .
a horn-shaped member 25 disposed through the horn-shaped member 25, an impeller 26 rotatably disposed within the horn-shaped member 25, and a motor 27 that rotationally drives the impeller 26 in a vertical plane.
It is composed of. The impeller 26 used has a diameter of 400 to 500 m and a number of blades of 4 to 8, and is driven by the motor 27 and belt 28.
Rotationally driven at a rotation speed of 000 to 1600 r, p, m,
This allows Shore particles to be projected into the chamber 10b at a speed of 50 to 60 m.

Furthermore, a through hole 29 is formed at the outer edge of the partition wall 13 below the housing 11, and a shot grain guide wall 3 is formed near the inside of the side wall 11a of the chamber 10c of the housing 11.
0 is provided, and a passage 31 is formed by the side wall 11a and the guide wall 3o. Further, one end of a shot suction tube 32 is connected to the lower end of the passage 31, and the other end of this tube 32 is connected to a separator 33 arranged above the housing 11. This separator 33 is
Among the projected shot particles, shot particles that are damaged to the extent that they cannot be reused are separated and discharged to the outside, and those that are intact or similarly unusable are sent to the outside via the connecting pipe 34. This is fed back to the shot grain supply source 23 mentioned above. Further, a collection B device 36 is connected to the horn-shaped member 25 of the shot particle projection mechanism 4 via a suction pipe 35.

Further, a shielding plate 37 is configured to be horizontally moved in parallel with the partition wall 12 above the housing 11 near the bottom thereof, and the shielding plate 37 allows the uppermost chamber 10a and the middle chamber 10b of the housing to be moved horizontally. are now isolated from each other. Furthermore, the earth wall 1 of the housing 11
A rotation center 38 is rotatably attached to 1b at a position corresponding to the steel component holding mechanism 21 described above.

Furthermore, as shown by the imaginary line in FIG. 1, a forced cooling means 39 is arranged around the steel component holding jig 21,
The rapid cooling means 39 is configured so that cooling air, inert gas, water, or the like is injected into the chamber 10b of the housing 11 from a compressor, cylinder, pump, or the like (not shown).

On the other hand, a high-frequency induction heating mechanism 9 consisting of the high-frequency coil 6, coil lead 7, and high-frequency transformer 8 described above is arranged so as to be movable in the horizontal direction on a mounting table 40 disposed on the side of the device main body 5. has been done. That is, the sliding member 41 attached to the bottom of the high frequency transformer 8 is engaged with the rail member 42 on the mounting table 40, so that the high frequency transformer 8 is driven horizontally by the air cylinder 43. It has become. As shown in FIG. 3, the above-mentioned high-frequency coil 6 is formed by bending so as to correspond to the outer shape of the steel part 1, which is the workpiece, and the length of both ends of the steel part 1 in the longitudinal direction is It is composed of coil parts 6a, 6b extending corresponding to the half circumferential surfaces and both sides of the diameter parts 1a, lb, and coil parts 6c extending corresponding to both sides of the small diameter part 1c formed in the middle of the steel component 1. .

Next, a case will be described in which the surface of the steel component 1 is strengthened using the apparatus configured as described above.

First, as shown in FIG.
One end of the steel component 1, which is a workpiece, is attached to a holding jig 21 disposed in the chamber 10a of the steel component 1, and the steel component 1 is held vertically. Thereafter, the lifting cylinder 14 is actuated to move the steel part 1 upward together with the drive shaft 16, so that the upper end of the steel part 1 is engaged with the rotation center 38, as shown in FIG. This positions the steel component 1. By operating the air cylinder 43 under this condition, the high-frequency induction heating mechanism 9 in the retracted position (the right position in FIG. 1) is advanced, and the high-frequency coil 6 is moved to the The parts are arranged near the middle part of the part 1.

Next, by operating the induction motor 19, the holding jig 21 and the steel component 1 are rotated at a rotation speed of 1.
At the same time, the high frequency current is supplied from the high frequency power source to the high frequency transformer 8, and the high frequency current is passed through the high frequency coil 6, for example in the direction of the arrow A in FIG. 1 is uniformly heated by high frequency induction to a predetermined quenching temperature (austenite region). Note that at this time, the frequency of the high-frequency power source is appropriately selected depending on the dimensions and heating depth of the steel component 1.

When the steel component 1 reaches a predetermined quenching temperature by high-frequency induction heating by the high-frequency coil 6, the supply of high-frequency current to the high-frequency coil 6 is cut off, and the high-frequency induction heating process is completed. Thereafter, by operating the air cylinder 43, the high frequency coil 6 is moved back to the original retracted position shown in FIG.

Thereafter, the lifting cylinder 14 is operated to move the steel part 1 together with the holding jig 21 downward through the central through hole 12a of the partition wall 12 of the housing 11, and the horn member 25 and forced cooling means 39 are moved inside the chamber 10b. Place it at the height position corresponding to . Next, the shielding plate 37 is horizontally moved from the outside of the housing II by a moving means not shown in the drawings, and placed in the vicinity of the lower part of the partition wall 12, substantially closing the central through hole 12a of the partition wall 12 and opening the housing 11. Room 10a
and 10b from each other.

Under such conditions, a cooling medium is injected from the forced cooling means 39 toward the steel component 1, and the steel component 1, which has been heated to a temperature in the austenitic region, is brought to a state of Ms (martensitic temperature) to 600°C. Forced cooling rapidly to a temperature in the stable austenite region. Subsequently, shot grains are supplied from the shot grain supply source 23 through the supply pipe 24 into the horn member 25, and the impeller 26, which is rotated at high speed by the motor 27, has a diameter of 0.5 to 0.8 nm. Shot particles are projected onto the steel part 1 at a speed of 50 to 60 m/s to perform plastic working. Note that at this time, the steel component 1 will be cooled by the shot particles. Next, oxygen is supplied from the forced cooling means 39 described above before, during, or continuously after the plastic working by shot particle projection.

A cooling medium such as an inert gas or tap water is injected onto the steel part 1 at a pressure of 3 to 5 kg/- to cool it to around room temperature for quenching.

After completing the surface strengthening treatment of the steel component 1 over the predetermined shot projection time and cooling time as described above, shot projection and cooling medium supply are stopped.

Incidentally, the projected shot particles pass through the through hole 29 of the partition wall 13 and fall in the passage 31 of the chamber 10c, and are transferred to the separator 33 via the shot particle suction pipe 32. and,
Only the crushed grains that cannot be reused are separated and discharged to the outside, and the reusable shot grains are again supplied to the shot grain supply source 23 and reused. Furthermore, if the cooling medium is water, it is drained to a water tank (not shown) by a drainage means (not shown). By the way, when water is used as a coolant, the shot particles are exposed to water and become wet, but if the shot particles are sprayed onto the steel part 1 in a wet state, the retroactive machining effect will be greatly reduced. This will result in a decline. In order to prevent this, in this embodiment, although not shown in the drawings, the water content of the shot particles is removed by a drying means provided on the way of conveying the projected shot particles to the separator 33.

Further, as another example of the water cooling method, there is a method of preventing the shot particles from getting wet by providing a nozzle that sprays atomized water and a suction port at a position opposite to the nozzle.

In this case, after the surface is rapidly heated to an austenitic state, the steel part 1 is rapidly cooled by immediately spraying water in the form of mist, and excess water in the form of mist and the steam that evaporates on the steel part 1 are removed using a suction device. Orthoform hardening of 540C carbon steel becomes possible by applying a zero-line water cooling method that discharges shot particles to the outside and prevents wetting of the shot grains and the wetting of the inner wall of the device.

A specific example of implementing the method according to the present invention using the above-described apparatus according to the present invention will be described below.

Between bodies (1) Material of steel part 1 SCM 435 (2) Dimensions of steel part 1 Total length: 210 weight l Diameter of large diameter part 1a, lb = 17 φ Diameter of small diameter part 1c = 8 φ Small diameter part 1c Length: 50n (3) Processing conditions <a> Heating conditions [43 Frequency: 400Ktlz [mouth] Power: 50KW [c] Heating time: 160 seconds <b> Cooling conditions [a] Cooling medium: compressed air [mouth] pressure crab 3. Okg <C> Shot particle projection conditions [Itashot particle size: 0.5 Tsuru [mouth] Projection speed: 50 m/s [C] Projection time = 10 seconds (4) Implementation results (1) to (3) above When the steel part 1 subjected to processing heat treatment under various conditions was measured using an Ono rotary bending fatigue tester, its fatigue limit was approximately 100 kgf/m''.

As described above, after rapidly heating the surface layer of the iron mesh component l to a predetermined quenching temperature (austenite region) by high-frequency induction heating by the high-frequency coil 6, this heated surface is
The heated surface is forcedly cooled to a temperature of 00°C, that is, the metastable austenite Hi region, and shot particles are applied to the heated surface to apply plastic working, and then the surface layer is heated to below the MS point for quenching. By cooling, ausformed martensite with an ausforming effect imparted to the surface layer can be obtained, thereby making it possible to manufacture a steel component 1 with high fatigue strength.

Although one embodiment of the present invention has been described above, the present invention is not limited to the embodiment described above, and various modifications and changes can be made based on the technical idea of the present invention.

For example, in the above-mentioned embodiment, a centrifugal force type using an impeller 26 was adopted as the shot particle projection mechanism 4, but the shot particle projection mechanism 4 is not limited to this, and the shot particle projection mechanism 4 may be 1 to 5 kg/ell! It is also possible to adopt a complete set of compressor and nozzle that shoots compressed air from a nozzle.

Further, in the case of the embodiment described above, the small diameter portion 1c is provided in the middle portion.
Since the workpiece is a steel component 1 having Gear (steel parts) 1' as shown
When applying high-frequency induction heating to the tooth surface using an annular high-frequency coil 6', when the gear 1' is held by the holding jig 21 and moved up and down, the gear 1' is heated by the high-frequency coil 6'. Since there is no collision, there is no need to provide a means for moving the high-frequency wave 6', and the high-frequency coil 6' can be fixedly placed at a predetermined position.

In addition, in the embodiment described above, the rapid cooling of the heated steel component 1 to the metastable austenite region and the quenching cooling after shot peening were performed by one forced cooling means 39, but different cooling means 39 are used. Two cooling means may be provided for the use of the medium. Furthermore, the steel part 1 heated by high frequency induction is cooled to the metastable austenite region at a slower rate than during plastic working.
In the case of steel parts made of materials with a long nose area, or in cases where the diameter is large and the self-cooling capacity is large, it may be carried out by natural cooling. good. In such a case, it is not necessary to provide the forced cooling means 39, and the number of parts can be reduced.
It is possible to reduce the cost of the device.

On the other hand, in the above-mentioned embodiments, the apparatus is configured vertically, but it goes without saying that it is also possible to configure it horizontally.

e0 Effects of the Invention As described above, according to the apparatus according to the present invention, the surface strengthening method for steel parts can be carried out effectively and efficiently. Moreover, since the present invention combines high-frequency induction heating using a high-frequency coil and shot peening processing, it is possible to use a material with a fairly complex shape as long as the surface layer can be uniformly heated by high-frequency induction heating. An extremely strong martensitic structure can be obtained even in steel parts due to the ausform effect, thereby greatly improving the fatigue strength of the steel parts and providing good durability.

Furthermore, in the present invention, since the steel parts to be processed are heated by high-frequency induction heating, only the surface layer can be heated to the required quenching temperature (austenite region) in a very short time. Can be done. In this case, since the volume of the heated surface layer of the steel part is small compared to the volume of the unheated part of the core, the core of the steel part still remains at a low temperature when high-frequency induction heating is completed. The steel mesh parts have what is called a self-cooling ability.

For this reason, the surface layer of the steel component is rapidly cooled due to the presence of the unheated part of the core, combined with the cooling effect of the cooling means, so the "nose" of the S curve in the isothermal transformation curve diagram Even for steel parts made of materials on the short-term side, the surface layer can be heated to 60% without pearlite precipitation.
It is possible to achieve a temperature in the metastable austenite region of 0° C. or lower. Therefore, according to the device according to the present invention, even if the "nose" is made of a material on the short-time side,
Surface treatment can be heat treated.

[Brief explanation of the drawing]

FIGS. 1 and 2 each schematically show the configuration of a surface treatment heat treatment apparatus for steel parts used to carry out the method according to the present invention! A cross-sectional view, FIG. 3 is a perspective view showing the correspondence between a high-frequency coil and a ring-shaped steel part, and FIG. 4 is a perspective view similar to FIG. 3, showing a case where the steel part is a gear. 1... Steel parts, 1'... Gear, la,
lb...Large diameter part, lc...Small diameter part, 2...Steel parts holding mechanism, 3...Steel parts drive 1) J mechanism, 4...Shot particle projection mechanism, 5...Device Main body, 6... High frequency coil, 6a
, 6b, 6cm coil part, 6'... High frequency coil holding member, 9... High frequency induction heating mechanism, 10a, 10b, 10cm chamber, ll... Housing, 14... Lifting cylinder, 18... Rotational force transmission mechanism, 19... Induction motor 21... Jig for holding steel parts, 23... Shot grain supply source, 26... Impeller, 33... Separator, 3
6... self-collection device, 37... shielding plate, 39...
・Forced cooling means. Patent applicant: Nissan Motor Co., Ltd.
Denki Kogyo Co., Ltd., Tegen 1 (and 2 others)

Claims (1)

[Scope of Claims] <A> Steel part holding means for holding a steel part as a workpiece; <B> A high-frequency coil for high-frequency induction heating of the steel part to a required quenching temperature; <C> The above-mentioned a shot peening mechanism for shot peening a steel part; a steel component drive mechanism for moving the component; <E> a cooling means for cooling the steel component heated by high-frequency induction heating by the high-frequency coil to a temperature in the metastable austenite region; <F> before the shot peening process. and a quenching cooling means for cooling the steel part to around room temperature for quenching during processing or continuously after processing.