JPH0464704A - Drill screw made of austenite group stainless steel and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve rust resistance and cutting property of a drill screw, and enable the mass production at low cost by performing cold forging to form a raw material having a head part and a drill blade part, in which the drill part is harder than the screw part and a diameter of the drill part is smaller than that of the screw part, and performing screw cutting processing to the raw material to scrape the residual thickness of the drill part, and setting a degree of hardness of the tip of the drill blade at Hv500 or more than and equal to HRC 49. CONSTITUTION:Cold forging is performed to the austenite group stainless steel wire to form a raw material having a head part, a screw part and a drill blade part, in which a diameter of the drill part is smaller than that of the drill part and a degree of hardness of the drill part is harder than that of the screw part. Molding, polishing and passivating are performed to the drill part of this raw material with a punching machine, and thereafter, screw rolling processing is performed and while the residual thickness of the drill part is scraped, and seizing preventing processing is performed, and a degree of hardness of the tip of the drill blade is set at Hv500 or more than and equal to HRC 49. Consequently, non-magnetic characteristic at a high and a low temperature, acid resistance, heat resistance, corrosion resistance, rust resistance and cutting property are improved, and mass production at low cost is possible.

Description

[Detailed Description of the Invention] [2] A material made by cold forging from austenitic stainless steel wire and having a 9-head, threaded portion, and drill bit, the hardness of the threaded portion and drill portion being the same as that of the drill portion. It is harder;
The diameter of the neck part of the semi-finished product is characterized by being manufactured from a material that is larger than the diameter of the drill part of the semi-finished product. Austenitic stainless steel according to item 1 [Technical field] The present invention relates to a heat-resistant stainless steel having a drill part for drilling holes at the tip;
An austenitic stainless steel drill bit with excellent corrosion and rust resistance and its manufacturing method.

[Background Art] Conventional screws of this type are used by having only the drill part quenched and hardened with a different material (as shown in Fig. 8), or are heat resistant and corrosion resistant.

Although its rust resistance is nowhere near as good as austenite, it was used for hardening martensitic. Carburizing.

If nitrided, brittle Cr carbides and nitrides are produced, which causes corrosion. Furthermore, when Cr carbides and nitrides are formed, Cr that resists oxidation and forms a protective film is reduced, making it bad for oxidation. In this respect, Cr-based stainless steel is susceptible to carburization and nitrogenization. However, in the past, austenitic materials that do not combine with C and N, are heat resistant and contain Ni, are strong, and materials with a lot of Nj are good, so currently high Ni austenitic materials are used, but the hardness is HRC45. The above was considered impossible, so
It was considered impossible to create a drill screw made of austenitic stainless steel using the same material.

[Purpose of the invention] The present invention has been made in view of the points stated above.

The object of the present invention is to be non-magnetic, have excellent properties at low and high temperatures, and have acid resistance, heat resistance, and corrosion resistance.

It is a drill screw with excellent rust resistance and good machinability. Another object is to provide a manufacturing method that can be produced in large quantities at low cost.

[Disclosure of invention] The present invention is made of austenitic stainless steel and is acid resistant.

Excellent heat resistance, corrosion resistance, and rust resistance. The hardness of the drill cutting edge is HV500 or HRC49 or higher.9. Drill screws with excellent machinability and their manufacturing method, as shown in Table 1, have no quench hardenability and are made of metals that cannot be hardened by quench hardening, and those that are hardened by diffusion and penetration of carbon and nitrogen. Although it has been researched and invented in various ways, it is acid resistant and heat resistant if heat treated.

The corrosion-resistant and rust-resistant properties of austenitic stainless steel change to those of 1-age stainless steel, and the differences in special properties become smaller. In addition, research has been conducted into a technology in which metal, carbon, or nitrogen is diffused and penetrated only at the cutting edge,9 but a perfect one has not yet been developed, and there is a need for an austenitic drill screw with excellent corrosion resistance. However, there is no solution to this problem, and only the one shown in Figure 8 has been developed.

The present invention compensates for the seven or more drawbacks described above and is inexpensive and can be supplied in large quantities.

Next, the manufacturing method will be explained, but the gist is that cold forging is used, the drill part is made harder than the threaded part by work hardening, and the drill blade has a hardness of HV500 or HRC49 or more. This is a method for manufacturing a drill screw with excellent corrosion resistance as set forth in claim 1, and will be explained in detail by way of examples.

Figure 1 is a diagram of a semi-finished product of a drill screw, and the drill part is a detail (d
) The figure is thinner, and the tip of the shaft part 2 corresponds to the drill part in the figure after finishing molding with a molding die. At the tapered part between the shaft part 2 and the tip part, the diameter of the drill part is expanded to be larger than the diameter of the material, and due to work hardening, the semi-finished product is kicked out of the molding die in a non-knockout bin after molding.

Although a semi-finished product of the drill screw is obtained, the diameter of the drill part is larger than the diameter of the finished shaft part shown in Fig. 4, and the diameter between the shaft part 2 and the tip part is Drawing is performed at the taper portion, further increasing the hardness of the drill portion.

Also, the diameter of the threaded part of the semi-finished product is 2 times larger than the diameter of the drilled part of the semi-finished product.
/100~5/100 Features large material. The method for manufacturing an austenitic stainless steel drill screw according to item 1.

As a practical example, as shown in Figures 1 and 4, work hardening can be achieved by drawing alone, and the area reduction rate is 27.
% can be drawn. - It is said that the tensile strength for boat fishing is work hardened by 1 kg/mm at a cross-section reduction rate of 1%.

Fig. 2 shows that the tip of the shaft part 2 in Fig. 1 is forged with a pair of forming dies 3 of the punching machine shown in Fig. 7, a drill part 5 is formed in the forming mouth part 4 of the forming die 3, and a forming cycle is performed. Part 4
It is a diagram in which a burr 6 is formed on the outer periphery of the drill part 5 using excess material that protrudes.

After forming the drill part with a punching machine, perform polishing and basivating, and with the blank in the state shown in Figure 2, roll the threaded part, remove the pre-thickness of the drill part, and perform a process to prevent seizure. It is characterized by 2. A method for manufacturing an austenitic stainless steel drill screw according to item 1. At this time, due to the effect of work hardening in the punching machine, the hardness of the drill part described in claim 1 is HV500.
．． Alternatively, it is a manufacturing method for obtaining a drill screw with excellent corrosion resistance characterized by having an HRC of 49 or more.

Next, this screw material 1 is sent to a rolling process and rolled through a rolling die 2.
Threaded at 5.

The pair of rolling dies 25 are arranged to face each other as shown in FIG.
A deburring surface 27 is provided below the threaded portion 26 on one end side. The thread material 1 with the burrs 6 attached is fed between a pair of rolling dies 25, and by sliding one of the rolling dies 25 in the direction of the arrow, the threaded portion 26 forms the shaft portion 2. The thread 7 is cut, and just before the thread cutting is finished, the burr 6 is removed on the deburring surface 27 as shown in Figure 1s11.
It will be cut off. In this way, a drill screw 10 as shown in FIGS. 3 and 6 is formed. Until the thread 7 is cut with the rolling die 25, the drill part 5 has a burr 6 attached to it, and when the thread is cut, the burr 6 is removed at the cutting surface 27, which improves the sharpness of the cutting edge on the outer periphery of the drill part 5. good. That is, after forming the drill portion 5 using the punching device 12 shown in FIG. 7, the burr 6 is removed.

During the process of conveying to the rolling process, etc., the edge of the cutting edge of the drill part 5 wears out and loses its sharpness, but if the burr 6 is removed during the rolling process, it is a process before it becomes a product.

The burr 6 is removed and the sharpness does not deteriorate. The method for manufacturing an austenitic stainless steel drill screw according to claim 3, characterized in that, at the same time as the thread rolling process, the pre-wall of the drill portion is removed to prevent seizure.

[Brief explanation of the drawing]

FIG. 1 is a front view of a semi-finished product of a top drill screw. FIG. 2 is a front view of the semi-finished product after punching the leading drill screw. FIG. 3 is a front view of a product obtained by rolling a semi-finished product of a leading drill screw. Figure 4 shows a semi-finished drill screw with a hexagonal flange head. Figure 5 is a semi-finished product after punching the drill part of a hexagonal flange head drill screw Figure 6 is a front view of a hexagonal 7 flange head drill screw product Figure 7 is a partial cutaway of the same punching process Perspective view. FIG. 8 is a front view and a side view of a conventional drill screw. FIG. 9 is a sectional view of the state in which molding is performed in the molding section same as above. FIG. 10 and FIG. 11 are perspective views of the rolling die same as above. FIGS. 12(a) and 12(b) are an enlarged front view and an end view of the same drill part.

Claims (1)

[Claims] [1] A drill screw having a head made of austenitic stainless steel, a threaded portion, and a drilled portion at the tip of the threaded portion, characterized in that the tip of the drill bit has a hardness of HV500 or HRC49 or more. Drill screw with excellent corrosion resistance. [2] It is a material made by cold forging from austenitic stainless steel wire and has a head, a threaded part, and a drill bit part, and the hardness of the threaded part and the drill part is harder,
2. The method for manufacturing an austenitic stainless steel drill screw according to item 1, wherein the diameter of the threaded part of the semi-finished product is made of a material larger than the diameter of the drill part of the semi-finished product. [3] Form the drill part using a punching machine using a material whose drill part is harder than the thread part described in item 2, and after polishing and passivating, remove the pre-wall of the drill part at the same time as the thread rolling process. 2. The method for manufacturing an austenitic stainless steel drill screw according to claim 1, wherein the screw is subjected to anti-seizure treatment.