JPH11193454A - Wear resistant part and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inexpensive, lightweight and wear resistant parts usable at high temp., and their production. SOLUTION: A member, composed of a martensitic chromium stainless steel containing, by weight, 0.4-0.6% C, 9.5-13.0% Cr, and 0.3-1.0% Mo at least, is hardened to <=HRC55 hardness by means of plasma carburizing and quenching and then tempered at 430 to 570 deg.C to undergo secondary hardening. Further, this member is subjected to cast-in insert by means of aluminum alloy casting, by which the wear resistant parts are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wear-resistant part having a complicated shape, such as a ball screw nut or a slider of a slide rail, having a wear-resistant surface hardened and hardened.

[0002]

2. Description of the Related Art As mechanical parts, many parts whose wear resistance is improved by quenching and hardening a raceway surface of a bearing or a sliding surface of a slide table are used. As a manufacturing method, a method of shaving a steel material by machining or a method of machining a hot, warm or cold-worked member is often used. The higher the hardness of the quenched surface of such wear-resistant parts, the more desirable it is, and at least a hardness of 55 or more is required. Conventionally, bearing steels are often used for such applications.

[Problems to be solved by the invention]

[0003] However, when these parts have a simple shape, they are easily formed by cutting or the like from an integral material, but a complicated shape, for example, a part such as a ball screw nut, has an inner diameter. The track surface requires high hardness due to the need for wear resistance, while the outer peripheral portion has a complicated shape because a steel ball circulation path is provided. Forming and heat-treating a round bar from a steel bar in order to manufacture it requires a great deal of man-hours and increases costs. In addition, there is also a problem that when the whole is made of steel, the weight increases, and in the case of moving body parts, the inertia increases and the response of movement is lacking. Therefore, in the present invention, the outer periphery of the member quenched to a predetermined hardness is formed by aluminum die casting to form a complicated shape, thereby reducing machining and manufacturing a lightweight and inexpensive wear-resistant part.

On the other hand, the bearing steels which have been widely used in the past are usually used after tempering at a temperature of 200 ° C. or less, and when the tempering temperature exceeds 200 ° C., the hardness rapidly decreases. Therefore, if the bearing steel quenched and tempered at such a temperature is fleshed with aluminum die casting, it will be tempered at the temperature during die casting higher than the original tempering temperature, and the hardness will decrease to obtain the required hardness. Could not. On the other hand, high alloy steel such as JIS. The use of high-carbon high-chromium tool steel such as SKD11 can prevent a decrease in hardness due to the temperature at the time of die casting, but such a steel material is expensive, so that the cost increases and it is not easy to obtain. .

Accordingly, the present invention provides a method of plasma carburizing and quenching inexpensive martensitic chromium stainless steel to obtain a high carbon content in a carburized layer which cannot be obtained by ordinary gas carburizing and the like. The purpose of the present invention is to provide an inexpensive wear-resistant part and a method for producing the same, by paying attention to secondary hardening when tempered at ° C. Also, focusing on the fact that the treated stainless steel does not soften even at the casting temperature during aluminum die casting,
It is an object of the present invention to provide a lightweight and inexpensive wear-resistant part having a hardened surface having a hardness of HRC 58 or more and a method of manufacturing the same, by forming a complicated shape by filling this with aluminum die casting.

[0006]

In order to achieve the above-mentioned object, a wear-resistant part of the present invention and a method for producing the wear-resistant part include at least C: 0.4 to 0.6 wt%, Cr: 9.5 to 13. 0w
After quenching a member made of martensitic chromium stainless steel containing t%, Mo: 0.3 to 1.0 wt% to HRC 55 or more by plasma carburizing and quenching 430
It is characterized in that it is tempered at a temperature of from 570C to 570C and is secondarily cured.

Conventionally, quenched and tempered bearing steel (JIS. SUJ) widely used for wear-resistant parts is 200.
There is a problem that when heated to a temperature of not less than ℃, the hardness is lowered, so that it cannot be used at a high temperature. On the other hand, the carburized and quenched layer obtained by plasma carburizing and quenching the above martensitic chromium stainless steel is secondarily hardened by tempering at 430 to 570 ° C., and the hardness increases. Therefore, the wear-resistant parts subjected to the treatment of the present invention can be used for wear-resistant members used at high temperatures without a decrease in hardness. This tempering hardening of the quenched layer is due to a phase change of retained austenite remaining during quenching and precipitation of a solid solution alloy. In addition, according to the plasma carburizing and quenching, a high carbon content of 2% or more, which cannot be obtained by gas carburizing, can be obtained in the carburized layer, and the carburizing is completed in a short time. There is an advantage that it can be reduced.

Conventionally, there is no example in which stainless steel is plasma carburized and used as in the present invention. Here, the component of the martensitic chromium stainless steel is C: 0.4 to 0.1.
The reason why the content of C is set to 6 wt% is that if C is too low, it takes too much time for plasma carburization, and the strength of the base material is lowered, so that cracks and peeling of the carburized layer are likely to occur. On the other hand, if C is too high, the hardness of not only the carburized layer but also the inside thereof increases to lower the overall impact resistance, and the material becomes expensive and the cost increases.

The above component is composed of Cr: 9.5 to 13.0 wt.
%, Mo: 0.3 to 1.0 wt% is widely known as an amount of alloy necessary for secondary hardening by tempering, and is intended to make it easier to obtain the tempering hardness of secondary hardening. It is. The above-described martensitic chromium stainless steel of the present invention has a higher carbon content such as AISI440C.
Easy to machine and cheaper than high alloy stainless steel.

[0010] Since a high carbon content of about 2% is obtained in the plasma carburized layer, the hardness may not be too high due to residual austenite during quenching. Here, the first quench hardness is set to HRC55 or more because the first quench hardness of the steel carburized with this chemical component is H
If it is RC55 or more, the retained austenite undergoes a phase change by tempering at 430 to 570 ° C. to become martensite,
This is because the required hardness of HRC 58 or more can be reliably obtained after tempering together with precipitation hardening.

Further, the wear-resistant part and the method of manufacturing the same according to the present invention are characterized in that at least C: 0.4 to 0.6 wt%, Cr: 9.
A predetermined surface of a member made of martensitic chromium stainless steel containing 5 to 13.0 wt% and Mo: 0.3 to 1.0 wt% is quenched to a hardness of HRC 55 or more by plasma carburizing and then 430 ° C to 570 ° C. Characterized by being tempered and secondarily hardened, and the member is formed by thickening by aluminum alloy casting.

That is, according to the present invention, a portion requiring wear resistance is formed by using a quenched and hardened steel material having a simple shape, and a portion having a complicated shape and not requiring wear resistance is formed by casting an aluminum alloy. The purpose of the present invention is to provide a lightweight and inexpensive wear-resistant member by forming it with a flesh.

[0013] If a portion that does not require abrasion resistance is formed by thickening by aluminum alloy casting, a complicated shape can be easily obtained as compared with shaving from a solid steel material and molding. Man-hours can be significantly reduced. Also, in the case of small-scale production, if an aluminum alloy is formed into a near net shape using an approximate die and the aluminum alloy portion is machined, it is easier than a steel material and requires less man-hours. Various casting methods such as die casting and gravity casting can be used as the aluminum alloy casting.

However, in the case of the conventional hardened and tempered bearing steel, when the aluminum alloy is cast, the bearing steel is softened at the temperature at the time of casting, so that a hardness higher than the predetermined HRC 58 cannot be obtained. Therefore, the present invention provides a method of forming a plasma-carburized carburized layer of the stainless steel at 430 to 570 ° C.
It was noted that the secondary curing caused by the heating caused the hardness to increase. That is, if tempering is performed at such a temperature, a hardness equal to or higher than the predetermined HRC 58 can be obtained without softening at the temperature at the time of casting, so that weight reduction and cost reduction can be easily achieved by thickening the aluminum alloy. . Although the casting temperature of the aluminum alloy is usually higher than the tempering temperature of 570 ° C., the solidification time of the molten metal is short, so that it is 430 to 430 ° C.
The stainless steel tempered at 570 ° C. does not soften during casting. Die steel with low tempering softening can be used for this purpose, but it is expensive and it is difficult to obtain a pipe material. On the other hand, the present stainless steel has an advantage that it can be obtained at low cost.

The bearing component and the method of manufacturing the same according to the present invention are characterized in that at least C is 0.4 to 0.6 wt% and Cr is 9.5.
１３13.0 wt%, Mo: 0.3〜1.0 wt%. A predetermined surface of the inner diameter of the steel pipe of martensitic chrome stainless steel is quenched to a hardness of HRC 55 or more by plasma carburizing and 430 ° C. to 570 ° C. And the steel tube is secondarily hardened, and the outer periphery of the steel pipe is formed by casting through an aluminum alloy casting.

For example, a bearing component such as a ball screw nut has a complicated shape such as a steel ball circulation path on the outer peripheral portion of a cylinder having a spiral groove rolling surface on the inside diameter. According to the present invention, the inner diameter portion where the wear resistance of the steel ball rolling surface is required is made of the above-mentioned martensitic chrome stainless steel steel pipe, and the inner diameter hole is drilled as compared with the conventional method of shaving from a round bar steel. Processing can be omitted, and a complicated shape can be easily formed at low cost by forming the outer periphery by casting with aluminum alloy casting. Further, since the weight is reduced by adopting such a configuration, there is an advantage that when used for a moving body or the like, the inertia is reduced and the response of movement is quick. In conventional bearing steels, such casting was not possible due to reduced hardness.

The hardness of the quenched surface after casting of the aluminum alloy is preferably as high as possible for the purpose of abrasion resistance. When used for a rolling bearing or the like, the hardness is preferably maintained at least at HRC 58 or more. However, the wear-resistant part of the present invention can sufficiently meet this demand.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, one embodiment of the present invention will be specifically described. FIG. 1 is a diagram comparing a manufacturing process of the present invention with a conventional process of a bearing member as one of the wear-resistant members, and FIG. 2 is a cross-sectional view schematically showing a product shape of an embodiment of the present invention.

In the ball screw nut of the product shown in FIG. 2, a steel ball 2 rolling in a spiral groove of a screw shaft 1 passes through steel ball circulation holes 6 and 7 at one end of outer cylinders 3 and 4 and a steel ball at the other end. The ball circulation hole 6 'returns to the spiral groove. The outside of the steel ball circulation hole 7 is covered with a cover material 5.

Conventionally, the inner cylinder 3 and the outer cylinder 4 shown in FIG. 2 are formed by cutting from an integral steel material. That is, as shown in the conventional manufacturing process of FIG. 1, first, a steel bar as a raw material was cut into a predetermined length, drilled, processed into a tubular shape, and the outer peripheral shape was formed by machining. After that, the required parts were gas carburized and quenched and the inner diameter was ground to obtain finished products. However, the outer peripheral portion has a steel ball circulation hole and the like, so that the shape is complicated and machining is difficult.
In addition, there has been a demand for increasing the weight and further reducing the weight by manufacturing the whole from a steel material.

On the other hand, according to the method of the present invention, the inner cylinder 3 and the outer cylinder 4 shown in FIG. The outer cylinder 4 having a complicated shape that does not require a property is formed by being filled with aluminum die casting. That is, in the present embodiment, as a method for casting an aluminum alloy, die casting is performed as shown in FIG.
As shown in the manufacturing process, after turning the outer diameter of the material steel pipe, cutting it to a predetermined length, plasma carburizing and tempering the required part, then casting the outer periphery with aluminum die casting did. After that, the product was finished by inner diameter grinding. As a result, the inner cylinder is easily machined and high wear resistance is obtained, and the outer cylinder part has significantly reduced machined parts,
Aluminum alloys are easier and lighter to process than steel, so the number of processing steps has been greatly reduced, reducing costs and achieving significant weight savings.

FIG. 3 shows the heat treatment characteristics of a quenched layer obtained by plasma carburizing and quenching martensitic stainless steel as shown in Table 1 as an example of the material of the inner cylinder 3 of the present embodiment.

[0023]

[Table 1]

As shown in the figure, the hardness of the quenched layer when vacuum quenching the above stainless steel without plasma carburizing is Hv700-750 (HRC60-
62), but softens as the tempering temperature increases, and decreases to Hv680 (HRC54) when the temperature exceeds 250 ° C. 50
Hv600 (H
RC55) is obtained, but when the temperature exceeds 500 ° C., the hardness sharply decreases and becomes unstable, so that the required hardness of HRC 58 or more cannot be obtained.

On the other hand, the hardness of the quenched layer subjected to the plasma carburizing and quenching according to the present invention is Hv760 as quenched.
(HRC 62.5). When tempering temperature increases, Hv
However, when the temperature exceeds 430 ° C., precipitation hardens and a high hardness of Hv 730 to 740 (about HRC 61.5) is obtained. If the tempering temperature exceeds 570 ° C, the hardness decreases again, so tempering at 430 ° C to 570 ° C is desirable. That is, if tempering is performed at this temperature after plasma carburizing and quenching, a wear-resistant part that can withstand long-term use even at a high temperature of 430 ° C. or higher can be obtained. The die casting temperature of the aluminum alloy for die casting is usually 570.
Although the temperature is higher than ℃, the solidification time is short, so that the stainless member tempered at the above temperature does not soften when the aluminum die-cast is cast. Therefore, if the martensitic stainless steel of the present invention is plasma carburized and quenched and then is thickened by aluminum die casting, the inner cylinder has a required hardness H used as a rolling bearing.
It was found that a hardness of v650 (HRC58) or more was obtained.

Although not shown in FIG. 4, even if the hardness at the time of plasma carburizing and quenching is low due to retained austenite, if Hv 600 (HRC 55) or more, the residual austenite undergoes a phase change due to tempering and becomes HRC 58 or more. It was found that the secondary hardening hardness was obtained.

[0027]

EXAMPLES The results of tests on actual parts under the following test conditions are shown below. Part dimensions: Shape shown in FIG. 2 Inner cylinder inner diameter d1: 26 mm φ Inner cylinder outer diameter d2: 33 mm φ Outer cylinder outer diameter D: about 60 mm φ Irregular length L: 30 mm Material of inner cylinder steel: Table 1 shows the components Martensitic stainless steel Manufacturing process: As shown in Fig. 1, it is processed using steel pipe and cast with aluminum die casting. Heat treatment conditions: After plasma carburizing and quenching shown in FIG.
0 ℃ × 2Hr tempering

As a result of the test under the above conditions, a very high hardness was obtained after die casting as follows. Test result: Surface hardness: Hv730 (about HRC61.5) Hardened layer depth higher than Hv650 (HRC58): 0.7
mm

As described above, according to the method for producing a wear-resistant part of the present invention, at least C: 0.4 to 0.6 wt.
%, Cr: 9.5 to 13.0 wt%, Mo: 0.3 to
After plasma carburizing and quenching a martensitic chromium stainless steel containing 1.0 wt% and then tempering at 430 ° C to 570 ° C, secondary hardening is achieved and a required HRC of 58 or more can be obtained. A wear-resistant member that can be used at high temperatures, which could not be used with the bearing steel, can be obtained at low cost. In addition, there is little deformation due to heat treatment, so that the machining allowance such as grinding is reduced, and the number of processing steps can be reduced.

Further, plasma carburizing and tempering is performed using martensitic chromium stainless steel having the above composition, and the member is hardened by casting with an aluminum alloy such as aluminum die casting. While the HRC satisfies HRC 58 or more, a complicated and large-volume portion is formed into an approximate product shape with an aluminum alloy, so that the number of machining steps is reduced, the cost is reduced, and the weight can be reduced.

In the above embodiment, the ball screw nut was tested. However, the manufacturing method of the present invention can be applied to a wear-resistant member in which the roller rolls or slides on a flat surface. In the case of a cylindrical shape, a stainless steel tube is used. By doing so, the cost can be further reduced, but this does not preclude cutting out from bar steel or flat steel. Further, the bearing component is used, but is not limited to the bearing component, and is widely used for wear-resistant parts.

[0032]

As described above, according to the wear-resistant part and the method of manufacturing the same according to the present invention, a martensitic stainless steel having a predetermined component is plasma-carburized and quenched and tempered, and is then filled with an aluminum alloy casting. A high hardness can be obtained in the required part, so that the weight can be reduced, and even a part having a complicated shape can reduce the number of mechanical steps and cost.

[Brief description of the drawings]

FIG. 1 is a diagram comparing a manufacturing process of a wear-resistant part of the present invention with a conventional manufacturing process.

FIG. 2 is a sectional view showing a shape of a wear-resistant part according to the embodiment of the present invention.

FIG. 3 is a diagram showing plasma carburizing quenching and tempering conditions of the wear-resistant part of the present invention.

FIG. 4 is a graph showing heat treatment characteristics of a quenched layer obtained by plasma carburizing and quenching the martensitic stainless steel of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Steel ball 3 Inner cylinder 4 Outer cylinder 5 Cover 6 Steel ball circulation path 6 'Steel ball circulation path 7 Steel ball circulation path

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI C22C 38/22 C22C 38/22 (72) Inventor Masatoshi Akiyama 5600 Higashi-Naka, Higashine-shi, Yamagata Pref. Inventor Isamu Sasa 5600 Higashi-Kone Ko, Higashine-shi, Yamagata Prefecture Netulen Kofu Co., Ltd. (72) Inventor Toshiharu Arishima Yamanoi Industrial Park, Sanyo-cho, Asa-gun, Yamaguchi Prefecture Netulen Kofu Co., Ltd.

Claims (7)

[Claims] 1. At least C: 0.4-0.6 wt%, C
r: 9.5 to 13.0 wt%, Mo: 0.3 to 1.0 w
A wear-resistant part characterized in that a member made of martensitic chromium stainless steel containing t% is hardened to a hardness of HRC 55 or more by plasma carburizing and quenching, and then tempered at 430 ° C to 570 ° C and secondarily hardened. . 2. At least C: 0.4 to 0.6 wt%, C
r: 9.5 to 13.0 wt%, Mo: 0.3 to 1.0 w
A predetermined surface of a member made of martensitic chromium stainless steel containing t% is subjected to HRC 55 by plasma carburizing and quenching.
A wear-resistant part formed by quenching to the above hardness, tempering at 430 ° C. to 570 ° C., secondary hardening, and forming the member by casting with an aluminum alloy. 3. At least C: 0.4 to 0.6 wt%, C
r: 9.5 to 13.0 wt%, Mo: 0.3 to 1.0 w
A predetermined surface of the inner diameter of a martensitic chrome stainless steel pipe containing t% is subjected to HRC 55 by plasma carburizing and quenching.
A bearing part characterized by being quenched to the above hardness, then tempered at 430 ° C. to 570 ° C. and secondarily hardened, and the outer periphery of the steel pipe is formed by casting an aluminum alloy. 4. The wear-resistant part according to claim 1, wherein the quenched surface after the casting of the aluminum alloy is maintained at a hardness of at least HRC 58 or more. 5. At least C: 0.4 to 0.6 wt%, C
r: 9.5 to 13.0 wt%, Mo: 0.3 to 1.0 w
A wear-resistant part obtained by quenching a member made of martensitic chromium stainless steel containing t% to a hardness of HRC 55 or more by plasma carburizing and quenching at 430 ° C. to 570 ° C. and secondary hardening. Manufacturing method. 6. At least C: 0.4-0.6 wt%, C
r: 9.5 to 13.0 wt%, Mo: 0.3 to 1.0 w
A predetermined surface of a member made of martensitic chromium stainless steel containing t% is subjected to HRC 55 by plasma carburizing and quenching.
A method for producing a wear-resistant part, comprising: quenching to the above hardness, tempering at 430 ° C. to 570 ° C., secondarily hardening, and forming the member by casting with an aluminum alloy. 7. At least C: 0.4 to 0.6 wt%, C
r: 9.5 to 13.0 wt%, Mo: 0.3 to 1.0 w
A predetermined surface of the inner diameter of a martensitic chrome stainless steel pipe containing t% is subjected to HRC 55 by plasma carburizing and quenching.
A method for producing a bearing component, comprising: quenching to the above hardness, tempering at 430 ° C. to 570 ° C., secondary hardening, and forming an outer periphery of the steel pipe by casting aluminum alloy by casting.