JP2001011534A - Austenitic stainless steel screws - Google Patents

Abstract

(57) [Abstract] [Problem] To provide an austenitic stainless steel screw that enables smooth screwing work and has excellent corrosion resistance. A screw material comprising a head portion (2) and a leg portion (3) integrally formed with the head portion (2) and having a thread (5) is obtained by forging and rolling, and the screw material is treated in a fluorine-based reaction gas atmosphere. An austenitic stainless steel screw that has been subjected to a surface hardening treatment that diffuses carbon to the surface of the screw material by heating at a temperature of 500 ° C or less, so processing is easy, corrosion is prevented, and the surface hardness of the screw is improved. Will be
A very ideal screw with excellent corrosion resistance and a high hardness surface is obtained. Moreover, since this surface is not magnetic, there is no rust. In addition, scratches and the like that occur when screwing with the driver bit do not occur, and the appearance and reliability are improved. In addition, a seizure phenomenon is unlikely to occur between the screw leg and the work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an austenitic stainless steel screw which is screwed into a work having a pilot hole in which a female screw is formed in advance and which fixes a component to the work.

[0002]

2. Description of the Related Art Conventionally, when a screw is screwed into a metal work, a pilot hole for screwing the screw is drilled in advance using a tool such as a drill. Is formed. Then, by screwing a screw into the prepared hole, the component is fixed to the work.

[0003] As a material of a screw used for such a screw, conventionally, an iron-based wire rod is cut into a predetermined length, and this is subjected to forging and rolling to engage a driver bit on the head. The thread material is formed by forming threads in the engagement groove and the legs, and then this screw material is heat-treated so that its surface is hardened, and is plated with zinc and chrome to prevent corrosion. To produce screws as products. However, the demand for these screws has been widespread recently, and the place where they are used is affected by the natural environment.
There is a problem that the screw itself is corroded in a relatively short time and the durability of the screw is reduced. Recently, such screws are used for the appearance of products, but it is necessary to prevent the occurrence of rust and the like. Recently, instead of manufacturing screws using iron-based materials, austenitic screws have been used. The use of stainless steel has been attempted.

[0004] As described above, in recent years, the production of screws made of corrosion-resistant austenitic stainless steel in place of screws obtained by applying a surface treatment such as plating to iron-based materials has increased. Although it has corrosion resistance as a property of the material, when a screw is manufactured using this, the surface needs to be hardened, so the nitriding treatment is adopted as a surface hardening process in this manufacturing process. I have. This is a screw in which the threads are nitrided and hardened, leaving the head at the hardness of stainless steel, and this screw is usually produced in a process as shown in FIG. This is performed by first forming a header processing step 11 on a blank (not shown) cut to a predetermined size.
0 forms the head of the screw. Thereafter, in a rolling step 111, a thread is formed on the leg by rolling to complete the screw material. Then, this screw material is subjected to a masking process on the legs in order to prevent the head portion that does not need to be nitrided in the next masking process step 112 from being subjected to nitriding. The head is plated with nickel. When this process is completed, subsequently, a peeling process is performed in a masking peeling process step 114 in order to peel off the masking of the leg portions performed in the masking process step 112, and then the nickel-plated head is subjected to a nitriding process step 115. Except for the portion, the legs are subjected to nitriding treatment, and further, plating is performed as a product in a finish plating step 116. When the masking process is not performed, a special method of performing nitriding process only on the leg portion of the screw is used.

[0005]

However, austenitic stainless steel has a higher corrosion resistance to acids and salts than iron-based materials such as carbon steel, but is inferior to carbon steel in terms of surface hardness and strength. The material conventionally used for this stainless steel (SUS305J1)
When using, processing is easy and corrosion is prevented,
When using this as a screw, the material is soft,
Hardness of each part of the screw material due to work hardening (Vickers hardness H
v) is a value as shown in Table 1.

[0006]

[Table 1]

[0007] Screws using this material are disadvantageous in that the threads are easily crushed in the fastening operation, and such screws are mainly made of plated iron-based carburized products or martensitic 13Cr. Stainless steel quenched products are used, but they have poor acid resistance and have problems such as short life due to rust.

Further, in another conventional example shown in FIG. 5, since the hardening treatment is performed only on the legs, the pre-process for performing the nitriding treatment for the hardening is complicated. Therefore, the processing cost used for this is high. In addition, in the case of mechanically performing a process for nitriding only the legs of the screw, it is necessary to heat-treat only the legs, so that it is necessary to mechanically align the screws in advance, Since the process is complicated, it is not suitable for mass production such as screw production. In addition, the nitridation treatment causes the nitrided layer to become magnetic and rust to be generated in this layer. At present, the layer is plated to have corrosion resistance. However, in this case, there is a problem in the adhesion of the plating and the reliability of the plating is lacking, such as the aesthetic appearance being impaired due to scratches or the like generated when screwing with a driver bit. In addition, when this screw is screwed into a pilot hole formed with a female screw of a soft work, a seizure phenomenon easily occurs between the screw leg and the work, and in order to prevent this, lubricating plating or lubrication Although use is considered, there are also problems such as generation of plating powder and gas.

In addition, in order to improve the acid resistance of the screw, an austenitic stainless steel cap having good acid resistance is press-fitted over the head of the iron-based screw to cover it, thereby preventing corrosion. However, since the legs of the screws are iron-based, the manufacturing cost of the screws is extremely high, and corrosion is still caused by gaps and rust of the work, and the life is shortened. .

[0010] An object of the present invention is to provide an austenitic stainless steel screw that solves the above-mentioned problems, enables a smooth screwing operation, and has excellent corrosion resistance.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a head 2 having an engaging hole 4 engageable with a driver bit and a leg 3 formed with a thread 5 integrally with the head 2. An austenitic screw material obtained by subjecting a screw material to be formed by rolling and rolling and heating the screw material at a processing temperature of 500 ° C. or less in a fluorine-based reaction gas atmosphere to diffuse carbon to the surface of the screw material. Achieved by providing stainless steel screws.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
4 through FIG. 1 and 2, 1
Is a screw made of austenitic stainless steel composed of a head 2 and a leg 3, and a head 2 having a diameter larger than the diameter of the leg is integrally formed at one end of the leg 3. An engaging hole 4 is formed in the head 2 so that a driver bit (not shown) for applying a screwing force for screwing the screw 1 is engaged with the leg 3 and the center line of the head 2. This leg 3
Has a thread 5 which is substantially parallel to the tip and has substantially the same outer diameter. The surface of the screw 1 has a processing temperature of 5 in a fluorine-based reaction gas atmosphere during the manufacturing process.
The surface of the screw 1 is heated at a temperature of 00 ° C. or less to diffuse carbon into the surface of the screw 1.

Further, a manufacturing process of the austenitic stainless steel screw 1 will be described. A blank (not shown) having a predetermined size is formed by a header processing step 10 for forming the head 2 in the processing step shown in FIG. The thread material is formed by continuous processing in a rolling process step 11 of rolling and forming the screw 5, and each part of the head 2 and the screw thread 5 has a work hardening due to the forging and the rolling. Table 2 shows the hardness (Vickers hardness) of each part of the screw member due to the work hardening.

[0014]

[Table 2]

Next, the screw material thus hardened is transferred to a surface hardening step 12. The surface hardening step 12 is set at a processing temperature of 500 ° C. or lower, and the inside of the furnace is in a fluorine-based reaction gas atmosphere. For this reason, this screw material is activated by fluorination, and carbon is diffused on the surface, and the surface is further hardened. on the other hand,
Since the heating temperature of the carbon is 500 ° C. or less, the carbon hardly affects the inside of the screw material, and the properties of the austenitic stainless steel itself are not impaired. That is, the excellent corrosion resistance characteristic of the austenitic stainless steel wire effectively acts on this screw material, thereby preventing the progress of corrosion and enhancing the acid resistance and corrosion resistance.

Using such an austenitic stainless steel screw 1, a pilot hole 2 in which a female screw is formed in advance in a plate-shaped work 20 made of aluminum, resin or iron.
1, when the leg 3 is pressed and screwed in,
The screw 1 is screwed along the internal thread of the pilot hole 21 as shown in FIG. At this time, even if the work 20 is relatively soft, the leg 3 is smoothly screwed into the work 20 without causing a seizure phenomenon. On the other hand, a reliable screwing force is stably transmitted without causing any damage to the head 2.

[0017]

As described above, the present invention comprises a head 2 having an engaging hole 4 engageable with a driver bit, and a leg 3 integrally formed with the head 2 and having a thread 5 formed thereon. An austenitic stainless steel obtained by screw forming and rolling forming a screw material, and heating the screw material in a fluorine-based reaction gas atmosphere at a processing temperature of 500 ° C. or less to diffuse carbon to the surface of the screw material. Since the screws are used, the flow of material during forging is good, and the life of a punch as a tool for forging the heads of these screws is long, and the manufacturing cost can be reduced. Also, corrosion resistance to acids and salts is higher than iron-based materials such as carbon steel.On the other hand, austenitic stainless steel, which is inferior in surface hardness and strength to carbon steel, is used. By applying a surface effect treatment for diffusing the surface, the surface hardness thereof is improved, and an extremely ideal screw having excellent corrosion resistance and a high hardness surface can be obtained.

Further, as compared with the conventional manufacturing method in which only the leg portion is subjected to the hardening treatment, the pre-process for hardening is simplified, and the processing cost for this is reduced. You. In addition, since only the legs of the screw are hardened, there is no need to heat-treat only the legs, and the process is simplified, which is suitable for mass production such as the production of screws. Moreover, unlike the conventional case, the surface does not take on magnetism, so that no rust is generated. Furthermore, even if plating is not performed after the surface hardening treatment in order to prevent this rust, sufficient corrosion resistance is obtained, and scratches or the like generated when screwing with a driver bit do not occur, thereby improving the appearance and reliability. Also,
Even if this screw is screwed into the female screw hole of a soft work, the seizure phenomenon hardly occurs between the screw leg and the work, and there is no need to use lubricating plating or a lubricant. Is also solved. Thereby, the torque at the time of the screwing operation, that is, the screwing starting torque is reduced, and a stable screw tightening operation can be obtained. In addition, since the thrust applied at the time of screwing is also reduced, a unique effect that has not been achieved in the past can be obtained, such as the occurrence of dents around the hole position of the work and the so-called burring action does not occur.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is an enlarged cross-sectional view showing a working state of the work.

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

FIG. 5 is a process chart showing a conventional processing step of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 screw 2 head 3 leg 4 engagement hole 5 screw thread 10 header processing step 11 rolling processing step 12 surface hardening processing step 20 work 21 pilot hole

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16B 35/00 F16B 35/00 J

Claims (1)

[Claims] 1. A threaded material comprising a head 2 having an engagement hole 4 engageable with a driver bit and a leg 3 integrally formed with the head 2 and having a thread 5 formed by pressing and rolling. Get
A screw made of austenitic stainless steel, wherein the screw material is heated in a fluorine-based reaction gas atmosphere at a processing temperature of 500 ° C. or lower to perform a surface hardening treatment for diffusing carbon on the surface of the screw material.