JP2000314412A - Screw member and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw member and a manufacturing method of the screw member, allowing simple joining work even in a narrow space without the possibility of cutting of a male screw part due to sufficient elongation of a shaft body, even if a large force is applied to a member to be joined. SOLUTION: A tensile strength of a male screw portion 3, formed on an end of a shaft body 2, is made 1.2 times to 1.5 times higher as compared with that of the shaft body 2, and the tensile strength of the shaft body 2 is made to 65 kgf/mm2 or less. Even if a large force is applied to a screw member 1 by an earthquake or the like, the shaft body 2 will be sufficiently elongated. The outer diameter dimension of the shaft body 2 is made same as a threaded ridge diameter dimension of the male screw portion 3. Thereby, the inserting hole of the screw member 1 formed on the member to be joined need not be set as large as a conventional one, and a nut threaded to the male screw portion 3 can be also made small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw member such as an anchor bolt used for building civil engineering and a method for manufacturing the screw member.

[0002]

BACKGROUND ART Conventionally, anchor bolts have been used to construct a building body on a concrete foundation. In this anchor bolt, a lower portion of the shaft main body is embedded in the foundation, and a male screw portion is formed at an upper end of the shaft main body protruding from the upper surface of the foundation. The building frame is joined to the foundation by screwing a nut into the male screw via a building frame such as a steel column. In this anchor bolt, generally, a steel rod-shaped material has a uniform tensile strength over its entire length. An anchor bolt is manufactured by thread-cutting an end of a steel rod having a uniform tensile strength.

When a large vibration is applied to a building due to an earthquake or the like, a force may be generated in the building body to move it away from the foundation. At this time, the anchor bolts extend in the axial direction to absorb the force applied to the building body. I do. Since a general anchor bolt has no difference in tensile strength between its shaft portion main body and the threaded portion, when a member to be joined, for example, a force that pulls out the building body from the foundation acts, the shaft portion main body becomes. Will not be sufficiently extended and will be broken at the threaded portion. That is,
When a force is applied to the anchor bolt, the function of the shaft main body is not sufficiently utilized. Therefore, conventionally, in order to ensure the breakage of the shaft portion main body, an anchor bolt in which the root diameter of the male screw portion is larger than the outer diameter of the shaft portion main body is used.

[0004]

In the above-mentioned conventional example, since the root diameter of the male screw portion is larger than the outer diameter of the shaft portion main body, the male screw portion is formed to protrude radially from the shaft portion main body. Therefore, when joining a steel column or the like to the foundation with anchor bolts, it is necessary to form a hole large enough to allow the male thread to pass through the bracket provided on the steel column or the like. You have to prepare something big. As a result, the accommodation of the anchor bolts becomes poor, and it becomes difficult to join the steel column or the like and the foundation using the anchor bolts in a narrow place.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a screw member and a screw which can be easily joined even in a narrow space without the shank body being sufficiently extended even when a large force is applied to the member to be joined and being cut by a male screw portion. An object of the present invention is to provide a method for manufacturing a member.

[0006]

Therefore, according to the present invention, the outer diameter of the shaft portion main body is made equal to the outer diameter of the male screw portion, and the tensile strength of the male screw portion is reduced by the tensile strength of the shaft portion main body. It is intended to achieve the above-mentioned object by setting the tensile strength of the shaft portion main body to a predetermined value or less and a predetermined value or less. Specifically, the screw member of the present invention is a screw member in which a male screw portion is formed at an end of a shaft portion main body, and the tensile strength of the male screw portion is smaller than the tensile strength of the shaft portion main body. 1.2 times or more and 1.5 times or less, preferably 1.4 times or more and 1.5 times or less, and the tensile strength of the shaft body is 65 kgf / mm ² or less;
The outer diameter of the shaft portion main body and the ridge diameter of the male screw portion are the same. Here, in the present invention, the screw member may be an anchor bolt.

In the present invention, the outer diameter of the shaft main body and the ridge diameter of the male screw portion are the same, so that the insertion hole for the screw member formed in the member to be joined is not increased as in the prior art. Alternatively, the nut to be screwed into the male screw portion can be reduced. For this reason, the screw member can be accommodated well, and the joining operation can be easily performed even in a narrow place.

Further, since the tensile strength of the male screw portion is 1.2 times or more and 1.5 times or less as compared with the tensile strength of the shaft main body, after the member to be welded is joined with the screw member, it becomes large due to an earthquake or the like. Even if a force is applied, the shaft portion main body is sufficiently extended without cutting the male screw portion. for that reason,
The function of the shaft main body of the screw member can be sufficiently achieved.

In the present invention, the reason why the tensile strength of the male thread portion and the tensile strength of the shaft portion main body are limited to the above values is as follows. The reason why the tensile strength of the male thread portion is set to be 1.2 times or more the tensile strength of the shaft portion main body is that if the value is less than this value, the shaft portion main body is not sufficiently extended when a force is applied to the screw member. The reason for this is that the external thread part may be cut off in the absence of it, and the tensile strength of the external thread part is set to 1.5 times or less the tensile strength of the shaft main body. This is because the production cost for increasing the tensile strength of the steel is too high.

[0010] The tensile strength of the shaft body is not more than 65 kgf / mm ^2, preferably, 50 kgf / mm ² or more 60 kgf / mm ² or less. The reason why the tensile strength of the shaft body is set to 65 kgf / mm ² or less is that when the screw member is an anchor bolt, the tensile strength required by the anchor bolt standard is 50 kgf / mm ² ,
From this 50kgf / mm ² because saw a margin of 15kgf / mm ^2. If the tensile strength of the shaft body is set to a value exceeding 65 kgf / mm ² , the production cost for increasing the tensile strength of the male thread portion becomes too high.

According to the method of manufacturing a screw member of the present invention, only the portion of the steel rod-shaped material forming the male screw portion is quenched, and then the quenched portion is tempered, and the hardened portion is thread-cut. It is characterized by processing. In the present invention, instead of quenching the entire screw member as in the related art, the quenching and tempering process is performed only on the portion where the male screw portion is formed, so that the tensile strength of the male screw portion is reduced by the tensile strength of the shaft body. It can be easily enlarged. here,
The quenching is performed by a predetermined heating means, for example, high-frequency induction heating at a predetermined temperature, for example, about 50 to 100 ° C. higher than the temperature at which the steel reaches the austenite region.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing an embodiment of the present invention. In FIG. 1, the screw member of the present embodiment is an anchor bolt 1. The anchor bolt 1 is a steel bar in which a shaft body 2 and male screw parts 3 adjacent to both ends of the shaft body 2 are integrally formed. It is.

The male screw portion 3 is engaged with a concrete product such as a foundation (not shown), and is inserted into an opening of a ring-shaped washer 4.
The two nuts 5 can be screwed from the outside of the nut. The other male screw portion 3 is engaged with a steel column bracket (not shown), and can be screwed to two nuts 6. A fixing plate 7 engaged with the bracket is interposed between the nuts 6, and a washer 8 is interposed between the fixing plate 7 and the outer nut 6.

The shaft body 2 has a tensile strength of 50 kgf / mm ²
It is 65 kgf / mm ² or less. Set the tensile strength of the shaft body 2 to 50
The reason why the weight is set to kgf / mm ² or more is that the anchor bolt 1 usually has a required tensile strength of 50 kgf / mm ² . In contrast, it had a tensile strength of the shaft body 2 and 65 kgf / mm ² or less is because from 50 kgf / mm ² which is the reference on request a margin of 15 kgf / mm ^2. The tensile strength of the shaft body 2 is 65 kgf / mm ²
Is exceeded, the manufacturing cost for increasing the tensile strength of the male screw portion 3 becomes too high, which is not practical.

The tensile strength of the external thread portion 3 is 1.2 times or more and 1.5 times or less as compared with the tensile strength of the shaft portion main body 2, and preferably,
It is 1.4 times or more and 1.5 times or less. The reason why the tensile strength of the male screw portion 3 is set to be 1.2 times or more the tensile strength of the shaft portion main body 2 is that, when the tensile strength is less than this value, when the screw member 3 generates a force, the shaft portion main body 2 This is because the male screw portion 3 may be cut in a state where the screw is not sufficiently extended. On the other hand, the reason why the tensile strength of the male screw portion 3 is set to 1.5 times or less of the tensile strength of the shaft portion main body 2 is that if this value is exceeded, the manufacturing cost for increasing the tensile strength of only the male screw portion 3 is increased. Is too impractical. FIG. 2 shows the male thread 3 of the anchor bolt 1
The neighborhood is shown. In FIG. 2, the outer diameter dimension d of the shaft portion main body 2 is the same as the crest diameter (outer diameter) dimension D of the male screw portion 3 (d = D).

Next, a method of manufacturing the anchor bolt 1 will be described with reference to FIG. In this manufacturing method, the total length is 50 times the nominal diameter of the male screw part, the male screw part 3 is 100 to 150 mm at each end, the tensile strength of the shaft body 2 is 50 to 65 kgf / mm ² or less, and the male screw part 3
Is 75% of the cross-sectional area of the shaft portion main body 2, and the tensile strength of the male screw portion 3 is 1.4 times the tensile strength of the shaft portion main body 2 to manufacture the anchor bolt 1 for construction. First, FIGS. 3A and 3B
As shown in Fig. 4, hardening is performed only on the portion 3A of the steel rod-shaped material 1A which forms the male screw portion. This portion is preferably set slightly wider than the portion forming the male screw portion.

The steel rod material 1A has a tensile strength of 50 to 50%.
A steel bar of 65 kgf / mm ² (for example, S30C in a standard state) is used. In addition, as shown in FIG. 3A, the quenching is performed by using a high-frequency heating device 10 and is heated to a predetermined temperature, for example, about 50 to 100 ° C. higher than the temperature at which the steel reaches the austenite region so that the shaft core is uniformly heated. This is performed by high-frequency induction heating at a temperature. Specifically, in the example of the bar steel of S30C, heating is performed to 900 to 950 ° C. The heated steel rod-shaped material 1A has a portion 3A forming an external thread portion.
However, as shown in FIG. 3 (B), the water is rapidly cooled to around room temperature by the cooling water injected from the water pipe 11.

By this quenching, for example, the mixed structure of ferrite and pearlite of the steel rod material 1A of S30C exhibits a single phase of martensite or a mixed structure of martensite and fine pearlite. The quenched steel bar 1A is shown in FIGS. 3 (C) and 3 (D).
Temper as shown in. The tempering is performed because the martensite structure is hard and rich in strength, but brittle and cannot withstand practical use. This tempering can make the steel tough.

In order to improve the mechanical properties of the quenched portion, high-frequency induction heating is performed at a predetermined temperature using a high-frequency heating device 10 as shown in FIG. After heating,
As shown in (D), the part is cooled by cooling water injected from the water pipe 11. The tensile strength of the quenched and tempered portion (corresponding to the male screw portion 3) is 70 to 90 kgf /, which is 1.4 times the tensile strength of the portion not quenched and tempered (corresponding to the shaft body 2). The heating temperature and the heating time of the high-frequency heating device 10 and the cooling condition by the water pipe 11 are set so as to obtain mm ² . After the quenching and tempering, as shown in FIG. 3 (E), a thread cutting process is performed using the cutting tool 12 on the quenched and tempered portion (the portion corresponding to the male screw portion 3).

Therefore, according to the present embodiment, the shaft body 2
Is the same as the outer diameter dimension d of the male screw portion 3, the insertion hole formed in the bracket for supporting the steel column, which is the member to be joined, does not need to be enlarged as in the conventional case. Also, the nut 6 screwed into the male screw portion 3 can be reduced. Therefore, the fitting of the male screw portion 3 of the anchor bolt 1 is improved, and the work of screwing the nut 6 into the male screw portion 3 can be easily performed even in a narrow place.

Further, the tensile strength of the male screw part 3 is
Since the tensile strength is 1.2 times or more and 1.5 times or less as compared with the tensile strength of the steel column, after the steel column supporting bracket as the member to be joined is joined with the anchor bolt 1, the anchor bolt 1
Even if a large force is applied, the shaft portion main body 2 is sufficiently extended without cutting the male screw portion 3. for that reason,
It is possible to prevent the building from being damaged due to the breakage of the male screw portion 3 of the anchor bolt 1 or the like.

Further, in the present embodiment, when the anchor bolt 1 is manufactured, only the portion 3A of the steel rod-shaped material 1A forming the external thread portion is quenched, and then the quenched portion is tempered. Since the thread tempering is performed on the tempered portion, the tensile strength of the male screw portion 3 can be easily increased as compared with the tensile strength of the shaft portion main body 2.
In addition, the high-frequency heating device 10
Since the appropriate high-frequency induction heating was performed using, the shaft core of the steel bar can be heated instantaneously.

It should be noted that the present invention is not limited to the above-described embodiment, but includes modifications and improvements as long as the object of the present invention can be achieved. For example,
In the above embodiment, the screw member is the anchor bolt 1, but in the present invention, the screw member may be a PC steel rod used for joining adjacent concrete members, or another screw member.

In the above embodiment, the quenching and tempering need not always be performed by high-frequency induction heating. For example,
The steel bar may be put in the heating furnace for a predetermined time. further,
It is not always necessary to use cooling water for cooling the steel bars. For example, liquid nitrogen may be sprayed. However, the use of cooling water can reduce the manufacturing cost of the anchor bolt 1.

[0025]

According to the present invention as described above, even when a large force is applied to the members to be joined, the shaft body is sufficiently extended and is not cut by the male screw portion, so that the joining operation can be easily performed even in a narrow space. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a front view showing a screw member (anchor bolt) according to an embodiment of the present invention.

FIG. 2 is a front view showing a main part of the embodiment.

FIGS. 3A to 3E are schematic diagrams for explaining a method for manufacturing a screw member according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw member (anchor bolt) 2 Shaft main body 3 Male thread 10 High frequency heating device

Claims (3)

[Claims] 1. A screw member having an external thread portion formed at an end of a shaft portion main body, wherein a tensile strength of the external thread portion is 1.2 times or more and 1.5 times or less as compared with a tensile strength of the shaft portion main body. A screw member, wherein a tensile strength of the shaft portion main body is 65 kgf / mm ² or less, and an outer diameter dimension of the shaft portion main body and a ridge diameter size of the male screw portion are the same. 2. The screw member according to claim 1, wherein said screw member is an anchor bolt. 3. The method for manufacturing a screw member according to claim 1, wherein the hardening is performed only on a portion of the steel rod-shaped material forming the male screw portion, and thereafter, the hardened portion is tempered. And performing a thread cutting process on the tempered portion.