JPH11287227A - Stainless steel tapping screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tapping screw in which the surface hardness of the ferrite and austenite stainless steel can be comparatively easily improved with the low cost. SOLUTION: In a tapping screw 1 manufactured by using the ferrite and austenite stainless steel as a material, a stainless steel tapping screw is manufactured by forming a screw thread 6 on a leg 4 comprising a cold (or warm) pressed head 2, plating a screw material with the electroless Ni-P alloy, and then heating the same for a specific time, so that the processes for manufacturing the tapping screw can be reduced, and the working cost can be also reduced. The process is simple, so that the tapping screw can be effectively massproduced with the low cost. Further the manufacturing processes can be reduced, so that the due data can be sufficiently shortened, and the management of the stock of the products can be simplified. Further a small tapping screw can be used in a comparatively fine part, so that the cost of the assembling work can be reduced, and the assembled product can be provided with the low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses ferritic and austenitic stainless steels as materials to improve the corrosion resistance and abrasion resistance of tapping screws as products, and to improve the mechanical properties when used for workpieces. In particular,
The present invention relates to a relatively small tapping screw, that is, a tapping screw suitable for assembling spectacles, cameras, watches, or the like.

[0002]

2. Description of the Related Art Conventionally, this kind of tapping screw made of stainless steel has been widely studied for use in various applications, but at present, the reliability of corrosion resistance and tapping property is still insufficient. is there. As this tapping screw, there is a so-called self-drilling type self-drilling tapping screw in which a drill portion is formed at the tip, and this is generally a screw as shown in FIG. In the manufacture of this screw, the head 2 is forged in a predetermined shape in a header process on a blank previously cut to a predetermined size, and then a drill portion 5 is cold-forged at the tip of the leg portion 4 and then the leg portion is formed. 4. In the rolling step, the thread is formed by rolling. In the case of a tapping screw which is not a self-drilling type but is screwed while forming a female screw into a prepared hole previously drilled in a work, the leg is immediately formed in a rolling process without cold forging the drill portion. The thread is roll formed in the part. After the screw is machined in this way, a nitriding process for forming a nitride layer on the entire screw is performed to increase the hardness. However, when the entire screw is nitrided as described above, the corrosion resistance is deteriorated and the hardness is increased, but the brittleness is brittle. Therefore, there is a problem that the engaging portion of the head with the driver bit is chipped by an impact force or the like.

For this reason, a screw as disclosed in Japanese Utility Model Publication No. 5-4564 has recently been devised. This is a screw in which the thread and the drill portion are surface hardened and the head remains at the hardness of stainless steel, and this screw is usually produced by a process as shown in FIG. The head of the screw is formed by a header processing step 110 on a blank (not shown) which is first cut to a predetermined size. Thereafter, in a drill / rolling process 111, a drill portion is cold forged at the tip of the leg portion, and subsequently, a thread is formed on the leg portion by rolling. Then, in a masking process step 112, a masking process for preventing nitridation is performed on a head that does not require nitriding, and subsequently, in a nickel plating process step 113, nickel plating is performed on the head. When this process is completed, a nitriding process is next performed in a nitriding process step 114, and then a peeling process is performed in a masking peeling process step 115 to peel off the masking performed in the masking process step 112. In the processing step 116, plating as a product is performed. When the masking process is not performed, a method of mechanically aligning the screw material so that the head does not enter the vacuum furnace so that only the leg portion of the screw is subjected to the nitriding process is used.
Also in the present invention, this drilling step is unnecessary for a tapping screw which does not require a drill portion.

[0004]

However, in Japanese Unexamined Utility Model Publication No. 5-4564, the hardening process is performed only on the leg portion having the thread. And the number of steps increases, and the processing cost used for this increases. In addition, when a process for nitriding only the screw legs is performed mechanically, only the legs need to be placed in a vacuum furnace, and it is necessary to mechanically align the screws. Is not suitable for mass production, such as screw production. Furthermore, ferritic and austenitic stainless steels have excellent corrosion resistance, but have a lower hardness than other stainless steels, so if used without hardening, the head of the screw may be damaged during screwing work, There is a problem that the thread is crushed in the course of screwing, the female screw forming of the work is insufficient, and the screw is in a floating state. In addition, due to such a long manufacturing time, there is a limit to shortening the delivery time, and in order to respond to the request from the user, a predetermined amount of screws as a product is always stored in stock as a product in advance. And the cost of product inventory management is high.
In addition, when using screws in relatively small assembled products such as eyeglass frames and watches, the strength of tapping screws is low, so it is necessary to form female screws for screwing screws into these workpieces in advance. There is a problem that the screw cannot be screwed in while forming a female screw directly into the prepared hole of the work.

An object of the present invention is to solve the above-mentioned problems and to provide a tapping screw which is inexpensive and in which the surface hardness of ferritic and austenitic stainless steels is relatively easily improved.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a tapping screw 1 made of ferritic and austenitic stainless steels, a head 2 having a head 2 having a predetermined shape formed by header processing. The leg 4 of the screw material 1 having the thread 4 is subjected to rolling to form a screw thread 6.
This is achieved by providing a stainless steel tapping screw which has been subjected to a heat treatment at a heat treatment temperature of about 400 ° C. for a predetermined time after applying an electroless nickel-phosphorus alloy plating with a film thickness of μ.

[0007]

FIG. 1 is a block diagram showing an embodiment of the present invention.
4 through FIG. In FIG. 1, 1 is a head 2
2 is a self-drilling type tapping screw that is screwed while forming a pilot hole (not shown) in a work by forging a cross hole 3 in the header processing step 10 shown in FIG.
The work shown in Figure 7 is a work 7
Tapping screw 1 which is screwed in while forming a female screw on the tapping screw. The screw material of the tapping screw 1 is composed of the head 2 and the leg 4. The self-piercing type tapping screw 1 as a product shown in FIG. 4 and a head 2 having a cross hole 3.

After the head 2 and the legs 4 are forged in the header processing step 10 shown in FIG. 4 in the header processing step 10 shown in FIG. Is formed by pressing, and subsequently, a thread 6 is formed on the leg 4.

[0009] An electroless nickel-phosphorus alloy plating step 12 is provided following the step of forming the screw material in which the shape of the tapping screw 1 is formed by the steps of such head forming and rolling forming. In the screw material, nickel-phosphorus alloy plating is applied on the whole
-25 μm. In this step, the screw material has a hard surface with a surface hardness of about HV700. Further, after this step, a heat treatment step 13 is provided.
The heat treatment at about 00 ° C. is performed for a predetermined time, that is, about 1 hour in this embodiment, and in this step, a hard surface having a surface hardness of about HV1450 of the screw material is further obtained. .

For this purpose, a blank (not shown) of a predetermined length made of ferritic and austenitic stainless steels is supplied to a header processing step 10 shown in FIG. The head 2 having one end is pressed and formed at one end to form a screw material. This screw material is transferred to a drill / rolling processing step 11 where a drill portion 5 is formed.
In the case of forming, the tip of the leg portion 4 of this screw material is inserted between the forging dies (not shown), and the forging is performed with these forging dies, whereby the drill portion 5 is formed at the tip. Instead of the forging, the drill 5 may be cut. On the other hand, when the drill part 5 is unnecessary,
This drilling step becomes unnecessary. When the screw material obtained in this way is rolled in the rolling process,
A thread 6 is roll-formed on the entire leg 4 to obtain a shape as the tapping screw 1.

Subsequently, the screw material is transferred to an electroless nickel-phosphorus alloy plating step 12, in which the entire screw material is plated with nickel-phosphorus alloy in a thickness of 10 μm to 25 μm. By this treatment, the surface of the screw material has a relatively higher surface hardness than the screw material. It can be screwed sufficiently with a relatively soft work such as resin and aluminum with this hardness, but the work is harder than iron, stainless steel or sticky nickel silver or zinc die cast. In the case of manufacturing, for example, the plated screw material is transferred to the next heat treatment step,
By performing a heat treatment at a predetermined temperature of about 00 ° C. for a certain period of time, for example, about one hour, a higher surface hardness can be obtained. For this reason, the screw can be surely screwed into a work other than resin and aluminum without occurrence of jumping of the screw head or floating of the screw. Thereafter, the tapping screw 1 thus obtained is further transferred to the next finish plating step 14, where the screw material is finished as a product.
A finish plating process such as a nickel zinc alloy is performed.

Incidentally, since the color of the final finish plating step 14 changes depending on the use of the self-tapping screw 1, it is not limited to the nickel zinc alloy. For example, plating of the same color as stainless steel or plating of black may be used. it is obvious. Further, in this embodiment, the self-drilling type tapping screw 1 having the drill portion 5 at the tip of the leg portion 4 has been mainly described, but the female screw is screwed into the prepared hole previously formed in the work while forming the female screw. The manufacture of the tapping screw 1 having no drill portion 5 may be performed without the drilling step as described above, and the same operation can be obtained in this case.

When the tapping screw 1 thus obtained has a drill portion 5 at the tip of the leg portion 4, it can be screwed in while drilling a pilot hole by pressing the screw portion against the work and screwing it. On the other hand, when the pilot hole is drilled in another assembling work step, particularly when the pilot hole is used for a work 7 such as a hinge connecting between a frame (not shown) of eyeglasses and a temple (not shown). This tapping screw 1 is shown in FIG.
As shown in FIG. 5, the female screw 8 is screwed into the prepared hole having the same diameter as the effective diameter of the thread 6 previously drilled in the work 7 while forming the female screw 8 with the thread 6 of the tapping screw 1.

[0014]

As is apparent from the above-described embodiments, the present invention is applied to a tapping screw 1 manufactured using ferritic and austenitic stainless steels as a material. A rolling process is performed on the leg portion 4 of the screw material having the formed leg portion 4 to form a screw thread 6. An electroless nickel-phosphorous alloy having a coating thickness of 10 to 25 μ is formed on the screw material having the screw thread 6. After plating, heat treatment temperature of this screw material is 4
It is a stainless steel tapping screw 1 which has been subjected to a heat treatment at 00 ° C. for a predetermined time.

[0015] For this reason, the number of manufacturing steps required until a tapping screw is obtained as a product from a screw material can be reduced as compared with the related art, and the processing cost used for this can be reduced. Also,
In the surface treatment operation and the heat treatment operation of the screw material, there is no need to mechanically align the screw material, and the process is simplified, which is suitable for mass production of low-cost tapping screws. Furthermore, since the surface of ferritic and austenitic stainless steels can be easily hardened, a tapping screw with excellent corrosion resistance and relatively high hardness, which is a unique effect of stainless steel, can be obtained. There is no problem that the head of the screw is sometimes damaged, the thread is crushed during the screwing, the internal thread is not formed sufficiently, or the screw is in a floating state. In addition, since the number of manufacturing processes is reduced, it is possible to sufficiently respond to shortened delivery times, promptly respond to requests from users, and always keep a large quantity of screws as products in stock in advance in large quantities at all times. There is no need, and inventory management of products is simplified. In addition, since small tapping screws can be used instead of small ordinary screws used for relatively small parts such as glasses and watches, assembly costs of these can be reduced, and assembling products can be provided at low cost. Specific effects can be obtained.

[Brief description of the drawings]

FIG. 1 is a front view of a self-piercing type tapping screw of the present invention.

FIG. 2 is a front view of another tapping screw of the present invention.

FIG. 3 is a sectional front view showing a state where the tapping screw of FIG. 2 is screwed into a work.

FIG. 4 is a process chart showing a manufacturing process of the present invention.

FIG. 5 is a process chart showing a manufacturing process of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tapping screw 2 Head 3 Cross hole 4 Leg 5 Drill part 6 Thread 7 Work 8 Female screw 10 Header processing step 11 Drilling / rolling processing step 12 Electroless nickel-phosphorus alloy plating step 13 Heat treatment step 14 Finish plating step

Claims (3)

[Claims] 1. A tapping screw 1 manufactured using ferritic and austenitic stainless steel as a material. The head 4 of a predetermined shape is formed by header processing into a leg 4 of a screw material. Forming a thread 6 by rolling, applying an electroless nickel-phosphorus alloy plating to the screw material having the thread 6, and then subjecting the screw material to heat treatment for a predetermined time; Self-tapping screws. 2. Electroless nickel-phosphorus alloy plating is 10 μm.
The stainless steel tapping screw according to claim 1, wherein the coating has a thickness of 25 μm. 3. The stainless steel tapping screw according to claim 1, wherein the heat treatment is performed at a heat treatment temperature of about 400 ° C.