JPH09143552A - Method for forging precipitation hardening type stainless steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuous forging to a precipitation hardening type stainless steel which is a hardly workable material by a parts former at a low cost and to reduce the product cost. SOLUTION: The coil or bar material of a precipitation hardening type stainless steel is cut by prescribed length to obtain slug, and after that, edge face straightening is executed at a room temp. Thereafter, the slug is subjected to surface roughening treatment by barrell polishing to font the surface into a rugged shape. Then, the retaining capacity of lubricating oil is increased, and prescribed forging is executed under oil lubrication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forging precipitation hardening type stainless steel, and more specifically, forging which prevents seizure with a die during processing and enables continuous production by a parts former at a low cost Regarding the method.

[0002]

2. Description of the Related Art Precipitation hardening type stainless steel is known as a difficult-to-work material, and once it is heated to the austenite temperature range,
A processing method has been proposed in which the material is cooled to a warm area, processed in the warm area, cooled to a martensite state, and then subjected to an aging treatment (Japanese Patent Application No. 3-6897).
4, Japanese Patent Application No. 4-189861).

In this case, the material can be processed in a soft state with high dimensional accuracy, and the required strength can be exhibited by the subsequent aging treatment.

By the way, in the conventional forging process of precipitation hardening stainless steel, a film is formed on the material for lubrication at the time of processing, and oil lubrication is also performed. It was not sufficiently retained during processing and peeled off or disappeared during processing to cause seizure with the die, resulting in a decrease in yield during forging and an increase in product cost.

[0005]

The invention of the present application has been made to solve such a problem. Thus, the invention of the present application is to obtain a slag by cutting a coil or a bar material of precipitation hardening stainless steel at a predetermined length, and then, for the slag, a surface roughening treatment including the cut end surface by polishing treatment. Is applied to make the surface uneven, and before or after the surface roughening treatment, the cutting end surface of the slag is subjected to straightening processing, and the slag having the uneven shape is subjected to predetermined lubrication under oil lubrication. Forging is performed (Claim 1).

According to a second aspect of the present invention, in the first aspect of the present invention, the slag having the surface-roughened shape is heated to austenite temperature region in advance before the forging process.
It is characterized in that it is cooled within a temperature range from 0 ° C. to Ms, subjected to the forging process within the temperature range, cooled to a martensite region, and then subjected to an aging treatment.

According to a third aspect of the present invention, in the first or second aspect of the present invention, barrel polishing using a polishing stone is performed as the polishing treatment for roughening the surface.

The processing method of claim 4 is the processing method of claims 1, 2, 3
In any one of the above, the forging process is performed with oil lubrication as it is without performing a film forming process on the slag.

The processing method according to claim 5 is the processing method according to claims 1, 2, and 3.
In any one of the above, the forging process is characterized in that a film is formed and the forging process is performed under oil lubrication.

According to a sixth aspect of the present invention, there is provided the processing method according to the fifth aspect, wherein, when forming the coating film, the coating film includes a graphite simple substance, a molybdenum disulfide simple substance, an undercoat of an inorganic salt containing potassium sulfate as a main component, and a molybdenum disulfide coating. It is characterized in that a two-layer coating composed of a combination is formed.

[0011]

As described above, according to the first aspect of the invention, after the precipitation hardening stainless steel coil or bar material is cut to obtain slag, the slag is roughened and the end surface of the cut surface is treated. The surface including the surface is made uneven, and then a predetermined forging process is performed under oil lubrication. According to the present invention, when the lubricating oil is applied to the slag surface due to the uneven shape, the lubricating oil is slag surface. Held well,
The lubricant is prevented from disappearing during the forging process.

Therefore, according to the present invention, even in the case of precipitation hardenable stainless steel which is a difficult-to-machine material, it is possible to form a coating film of molybdenum disulfide or the like during the forging process.
It was confirmed that good forging can be performed only with oil lubrication.

If the processing can be performed only by oil lubrication without forming such a film, the cost for forming the film can be reduced and the product cost can be reduced. ).

Further, according to the present invention, burrs and edges generated during cutting are removed by polishing the slag end face during the polishing process or prior to the polishing process, and a predetermined forging process is performed on the burrs. It is possible to prevent the seizure of the mold due to the edge.

In the present invention, prior to forging, the uneven slag is heated in advance to the austenite temperature range, then cooled within the temperature range from 700 ° C. to the Ms point, and processed within the temperature range. Is desirable.

By doing so, it is possible to process the slag in a soft austenitic state, and it is possible to produce products such as bolts with high efficiency by a continuous forging machine such as a part former only with oil lubrication (claim 2). . After the forging process, this is cooled to a martensite state and then subjected to a predetermined aging treatment to give a required strength.

In the present invention, it is desirable to perform barrel polishing using a polishing stone as a polishing treatment for roughening the surface of the slag, whereby the surface including the cut end face of the slag can be satisfactorily made into an uneven shape, The ability to retain the lubricating oil can be increased (claim 3).

In the present invention, it is of course possible to form a film on the surface of the slag having an uneven shape and then perform a predetermined forging process under oil lubrication. In this case, the action of the coating can further reduce the frictional resistance with the die during the forging process, and can prolong the life of the die significantly (claim 5).

Further, since the ability of holding the coating on the surface of the slag is increased, the coating is prevented from peeling off during the forging process. The coating is preferably a two-layer coating composed of graphite alone, molybdenum disulfide alone, or a combination of an underlying film of an inorganic salt containing potassium sulfate as a main component and a molybdenum disulfide coating (claim 6).

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a precipitation hardening stainless steel coil or bar material is cut into predetermined lengths by a shearing machine or the like to obtain a slag. Then, the slag is subjected to surface roughening treatment by polishing.

Usually, prior to the surface roughening treatment, first, a step of correcting the cut end surface of the slag is performed at room temperature. In the straightening step, the burrs and the corner edges due to the distortion and cutting of both end faces can be plastically rounded. It should be noted that this straightening step can be continuously performed in the part former. However, the surface that has undergone this plastic working has little unevenness, and it is difficult to apply subsequent forging processing continuously.

Therefore, next, surface roughening treatment, preferably barrel polishing using a polishing stone such as alumina, is performed to make the surface including the end face of the slag uneven. At this time, the degree of unevenness is preferably such that the surface roughness (average value Ra) is 1.5 to 5.0 μm.

When the surface of the slag is made uneven in this way, the slag is then subjected to predetermined forging under oil lubrication. At this time, since the surface of the slag is provided with predetermined irregularities, the applied lubricating oil is sufficiently retained on the surface of the slag, and forging can be smoothly performed under the lubricating action of such oil lubrication. . Therefore, for example, in the forging process of a product mainly for the forward extrusion, only the oil lubrication can be used for the forging process.

On the other hand, at the time of forging including strong processing such as backward extrusion, it is preferable to form a film on the slag surface and then forge under oil lubrication. Even in this case, the unevenness of the surface of the slag has a high ability to retain the coating and the lubricating oil, which enables smooth processing without causing seizure in the die, and significantly extends the life of the die compared to the conventional method. be able to.

In any of the above cases, the surface-roughened slag is once heated to the austenite temperature region and then cooled within the temperature range from 700 ° C. to the Ms point, and the forging is performed within the temperature range. It is better to process it. Then, after the forging process, it is cooled to a martensite state and then subjected to an aging treatment according to a conventional method to develop a required strength.

As the above coating, graphite or molybdenum disulfide can be formed alone depending on the application. As the method, for example, a method of forming a film on the surface by immersing the slag in a solution of graphite or molybdenum disulfide can be adopted.

On the other hand, when performing processing with higher strength,
A coating composed of a combination of an undercoat of an inorganic salt containing potassium sulfate as a main component and a coating of molybdenum disulfide can be used. As a method of forming the film, the slag is batchwise placed in a treatment tank in which an inorganic salt is dissolved for a predetermined time, for example, 10 times.
Immerse for about a minute, then dry and then load into a barrel device with molybdenum disulfide powder and polishing stones,
A barrel can be used to form a film by treating with a barrel machine using a polishing stone.

[0028]

Next, embodiments of the present invention will be described in detail. Table 1
SUS630 coil (diameter 8 mm and 10
mm) was drawn by cold drawing. The oxalate film was treated during wire drawing. Next, after cutting this coil to obtain slag, according to the process shown in Fig. 1 or 2 in the parts former, end face correction (parallelism of both end faces) and corner at room temperature with lubricating oil applied. Chamfering (usually referred to as heading R and 0.2 to 0.4R) was performed.

[0029]

[Table 1]

FIG. 1 shows a slag working process for a flange bolt, and FIG. 2 shows a slag working process for an M8 cap bolt. If such correction and chamfering steps are not performed, seizure will occur early in the subsequent forging step. The parallelism of both end faces was secured in the slag thus produced, and the surface roughness was changed to the surface roughness as shown in Table 2.

[0031]

[Table 2]

Next, 15 × 15 × 10 m as a polishing stone
The slag was barrel-polished in batches using a triangular type alumina of m and a compound (for example, sodium phosphate) for controlling the surface roughness to make the surface uneven. Table 2 shows the changes in the surface roughness at that time.

Next, the slag subjected to the surface roughening treatment was subjected to various coating treatments according to Table 3 and subjected to forging. In Table 3, A, B, C, and D are the cases where the surface roughening treatment by barrel polishing was not performed, and E, F, G, and H were the cases where the surface roughening treatment by barrel polishing was performed.

[0034]

[Table 3]

Here, A and E were forged only by oil lubrication without forming a film. In the case of the graphite coating and molybdenum disulfide coating in the table, the coating is formed by immersing the slag in a solution of graphite or molybdenum disulfide powder dissolved in 50 ° C hot water. , A solution of an inorganic salt containing potassium sulfate as the main component is heated to 80 ° C., the slag is immersed in the solution for 10 minutes, and then dried and then spray coated with molybdenum disulfide, or with molybdenum disulfide powder and a polishing stone. It was charged into a barrel apparatus and barrel-treated to finally form a two-layer coating of an inorganic salt base coating and a molybdenum disulfide coating.

In this case, naturally, the adhesion strength of the coating differs depending on the state of barrel polishing performed for surface roughening. The method using shot blast was abandoned because the degree of skin roughening was poor and burr could not be completely removed.

When the slag-molded product was processed as it was, there were no coatings on the edges and end faces and the oil retaining ability was inferior.

Next, according to the steps shown in FIGS. 3 and 4, in order to confirm the effect of the coating film in the mass production line, forging of the flange bolt and the M8 cap bolt was carried out, and the die life in each step was examined. The results are shown in Table 4.

[0039]

[Table 4]

As is clear from the results shown in Table 4, when the slag is barrel-polished and then subjected to forging, the holding ability of the lubricating oil or the coating is improved, and the baking life with the die is significantly improved. The effect of doing is recognized. In particular, when the forging process is performed only by oil lubrication without forming a film, the mold life is extended by about 5 times for flange bolts and 10 times or more for M8 cap bolts by barrel polishing. .

Although the embodiment of the present invention has been described in detail above, this is merely an example, and the present invention can be implemented in various modified modes without departing from the spirit of the invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a slag forming process when manufacturing a flange bolt according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a slag forming process when manufacturing a flange bolt according to an embodiment of the present invention.

FIG. 3 is a process explanatory view when forging a flange bolt according to the embodiment of the present invention.

FIG. 4 is a process explanatory view when the M8 cap bolt is forged according to the embodiment of the present invention.

Claims (6)

[Claims] 1. A precipitation hardening stainless steel coil or bar material is cut into a predetermined length to obtain a slag, and then the slag is subjected to a surface roughening treatment including the cut end surface by a polishing treatment. The surface is made uneven, and the cut end surface of the slag is corrected at room temperature before or after the surface roughening treatment, and the predetermined forging is performed on the uneven slag under oil lubrication. A method for forging a precipitation hardening stainless steel, which is characterized by being performed. 2. The slag having a surface-roughened shape as set forth in claim 1, which is preheated to an austenite temperature region prior to the forging, and then cooled within a temperature range from 700 ° C. to the Ms point, and within the temperature range. The method for forging precipitation hardening type stainless steel, which comprises performing the above-mentioned forging process, cooling to the martensite region, and then performing an aging treatment. 3. The method for forging precipitation hardening stainless steel according to claim 1, wherein barrel polishing using a polishing stone is performed as the polishing treatment for roughening the surface. 4. The precipitation hardening stainless steel according to claim 1, wherein the forging process is performed with oil lubrication as it is, without forming a coating film on the slag. Forging method. 5. The method for forging a precipitation hardening stainless steel according to claim 1, wherein a film is formed during the forging, and the forging is performed under oil lubrication. . 6. A two-layer coating comprising a combination of a graphite simple substance, molybdenum disulfide simple substance, or an undercoating of an inorganic salt containing potassium sulfate as a main component and a molybdenum disulfide coating when forming the film. A method for forging a precipitation hardening stainless steel, which comprises forming a.