JP2010164128A - Female screw part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method which allows tightening force to be stably produced in an axial direction of a male screw when a male screw part is tightened by a female screw part with the same torque. <P>SOLUTION: When manufacturing a female screw part by cutting after hot forging, cold forging and cold drawing, an inclination of a bearing surface with respect to a shaft of a male screw is set to be 0.35° or less, so that a dispersion of torque coefficients is reduced by 50% or more as compared with that in torque coefficients of a female screw part having a bearing surface inclination of 2° or less. The female screw is cut smaller than an effective diameter by 0.2 to 0.3 mm and plastically machined up to an effective diameter by a rolling tap. The dispersion in the torque coefficients is reduced by 80% or more as compared with that in torque coefficients of the female screw part having a bearing surface inclination of 2° or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a female screw component, and more particularly, to a female screw component that can stably generate an axial tightening force on a male screw when the male screw component is tightened with the same torque.

  A method of fastening a member by combining an internal thread part (nut) and an external thread part (bolt) to generate an axial tightening force on the external thread by the internal thread tightening force is well known. The tightening force generated in the axial direction of the male screw depending on the member to be fastened and the application is controlled by the tightening torque of the female screw so that it is within a predetermined control range.

In general, it is well known that the torsion torque of the female screw and the axial tightening force of the male screw have the following relationship depending on the torque coefficient value and the nominal diameter of the screw.
K = Torque N · m / Bolt diameter (mm) · Tightening force (KN)
However, K is a torque coefficient value.

  When mass producing female screw parts, cold forging of materials, cutting out from cold drawn materials, and hot forging are widely adopted (Patent Literature 1, Patent Literature 2, Patent Literature 3, Patent Literature 4, Patent Literature). 5).

JP 07-276139 A JP 2006-26889 A JP 2004-186217 A JP 2000-326047 A JP 2007-107041 A

  However, when female thread parts manufactured in a normal mass production process are used, the torque coefficient value K described above varies greatly, and seizure of nuts due to overtightening, insufficient frictional joint force due to insufficient tightening axial force, and loosening of screws. It sometimes occurred.

  This invention makes it a subject to provide the internal thread component which enabled it to acquire the stable axial direction clamping force in view of this problem.

  Therefore, the manufacturing method of the internal thread component according to the present invention is such that, when the internal thread component is manufactured by hot forging, cold forging, and cutting after cold drawing, the tilt of the seat surface with respect to the axis of the external thread is 0.35 degrees or less. The variation in the torque coefficient value is reduced by 50% or more in comparison with the variation in the torque coefficient value of the female screw part with the tilt of the bearing surface being 2 degrees or less.

  In addition, the manufacturing method of the female screw part according to the present invention is such that when the female screw part is manufactured by hot forging, cold forging, and cutting after cold drawing, the tilt of the seat surface with respect to the male screw shaft is 0.35 degrees or less. The internal thread is cut to 0.2 to 0.3 mm smaller than the effective diameter, and is plastically processed to the effective diameter by a rolling tap, and the variation of the torque coefficient value is less than 2 degrees of the seat surface collapse. It is characterized in that it is reduced by 80% or more in comparison with the variation of the torque coefficient value of the female screw part.

The torque coefficient value K is considered to vary mainly due to the following factors.
1. Fluctuation in friction between the nut seat and its contact surface.
2. Fluctuation in frictional force between the contact surfaces of male and female screws.

  One of the features of the present invention is that the manufacturing conditions are controlled so that the inclination of the bearing surface of the female screw relative to the axis of the male screw is 0.35 degrees or less.

  As a result, it is possible to reduce the increase in local frictional force due to the unevenness of the female screw seat surface and the unevenness of the screw surface of the male screw and the female screw. It can be reduced by 50% or more in comparison with the variation of torque coefficient values of parts (finishing acceptable by JIS).

  Another feature of the present invention is that the manufacturing conditions are controlled so that the inclination of the bearing surface of the female screw with respect to the axis of the male screw is 0.35 degrees or less, and the effective diameter of the female screw is less than the intended screw. The surface roughness of the internal thread is improved by cutting it to about 0.3 mm smaller, and further plastically processing the thread to the target effective diameter with a rolling tap.

  Thereby, the fluctuation | variation of the friction with the thread surface of an external thread can be decreased, and the variation in a torque coefficient value can be further reduced by 30% or more and 80% or more in total.

  Moreover, the obtained internal thread component is also novel. In other words, according to the present invention, the tilt of the seat surface is formed to be 0.35 degrees or less with respect to the shaft of the female screw, and the torque coefficient of the female screw component whose tilt of the seat surface is 2 degrees or less It is possible to provide a female screw part characterized by being reduced by 50% or more in comparison with the variation in numerical values.

  Further, according to the present invention, the tilt of the seat surface is formed to be 0.35 degrees or less with respect to the axis of the female screw, and a cold plastic deformation layer having a thickness of 0.35 mm to 0.45 mm from the female screw surface is formed. Provided is a female screw component that is formed and has a variation in torque coefficient value that is 80% or more less than a variation in torque coefficient value of a female screw component with a seating surface tilt of 2 degrees or less. Can do.

  The cold plastic deformation layer is obtained, for example, by cold rolling using a rolling tap, and can be determined by measuring the hardness distribution.

It is a figure which shows the front and side of the internal thread component manufactured by preferable embodiment of the method which concerns on this invention. It is a figure which shows typically the fall of the bearing surface of the said internal thread component. It is a figure which shows the fall of the bearing surface of a comparative example. It is a figure which shows a test result.

  Hereinafter, the present invention will be described in detail based on examples.

  An M20 type 1 nut using austenitic stainless steel SUS304 as a material was manufactured by the method according to the present invention. The composition of this austenitic stainless steel SUS304 is C: 0.08% or less, Si: 1.00% or less, Mo: 2.00% or less, P: 0.045% or less, S: 0.030% or less, Ni : 8.00 to 10.50%, Cr: 18.00 to 20.00%.

  Using this austenitic stainless steel SUS304 material, a nut blank was forged at a temperature of 1200 ° C. to 1350 ° C. and a load of 30 to 40 tons with a pilot hole in the outer shape of the nut. Next, the forged nut blank was subjected to a solution heat treatment, and pickling for descaling was performed, followed by washing with water to remove the acid solution and drying. Finally, threading is performed using a tap in the prepared hole (hole diameter: 17.744 to 17.294 mm) of the nut bracket to form the female screw 11 (hole diameter: 18.4 to 18.2 mm), and the nut A product (female screw part) 10 was obtained.

  At this time, the manufacturing processes such as forging of the nut blank, threading, and surface finishing were controlled so that the fall of the seat surface 12 of the nut product 10 was 0.35 ° or less.

In the same manner as in Example 1, after obtaining a pilot hole (hole diameter: 17.744 to 17.294 mm) of the nut bracket, the hole diameter: 18.1 to 18.0 mm was cut and rolled to -200 μm. A female thread was formed using a tap to obtain a nut product (female thread part).
[Comparative Example 1]

  Although the nut product 20 was manufactured similarly to Example 1, the fall of the seat surface 22 was 0.1 degrees or less.

[Torque coefficient value test]
Torque is applied to the 5 nut products of Example 1, 5 nut products of Example 2 and 4 nut products of Comparative Example 1 thus obtained up to 5000 kgf, and then rotated in the opposite direction to loosen the screws. This operation was repeated four times, a chart of tightening force (KN) and torque (N · m) was taken, and a torque coefficient value K was obtained. The result is shown in FIG.

Example 1
Average torque coefficient value 0.290
Standard deviation 0.020
Variation width 0.067
Minimum 0.253
0.320 max
Number of samples 20

Example 2
Average torque coefficient value 0.287
Standard deviation 0.014
Variation width 0.053
Minimum 0.253
Max 0.307
Number of samples 20

Comparative Example 1
Average torque coefficient value 0.329
Standard deviation 0.047
Variation width 0.133
Minimum 0.267
0.400 maximum
Number of samples 16

  Based on the above, by controlling the tilting of the seat surface of the nut product, the variation of the torque coefficient value is compared with the variation of the torque coefficient value of the female thread part (the JIS acceptable finishing degree) where the tilting of the seating surface is 2 degrees or less. Improved by 58%.

  Furthermore, in addition to the management of the nut seat surface, it was confirmed that it could be further improved by 30% by controlling the thread accuracy by rolling.

  In the above description, the case where the SUS304 M20 type 1 nut is manufactured by hot forging has been described as an example. However, when a female screw part is manufactured by cold forging or cutting after cold drawing for other materials. However, the same torque coefficient value can be stabilized by managing the falling of the seating surface and improving the screw thread accuracy.

10 Nut product 11 Female thread 12 Seat surface 20 Nut product 22 Seat surface

Claims (4)

  The tilt of the seating surface is formed to be 0.35 degrees or less with respect to the shaft of the female screw, and the variation of the torque coefficient value is 50 as compared with the variation of the torque coefficient value of the female screw component with the tilting of the seat surface being two degrees or less. A female screw part characterized by being reduced by more than%.   The tilt of the bearing surface is formed to be 0.35 degrees or less with respect to the axis of the female screw, and a plastic deformation layer having a thickness of 0.35 mm to 0.45 mm is formed from the surface of the female screw. A female screw part characterized in that the seat surface tilt is reduced by 80% or more in comparison with the variation of the torque coefficient value of the female screw part having a tilt of 2 degrees or less.   When manufacturing female threaded parts by hot forging, cold forging, and cutting after cold drawing, it is manufactured so that the tilt of the bearing surface with respect to the axis of the male thread is 0.35 degrees or less, and the variation in torque coefficient value is limited. A method for manufacturing a female screw part, characterized in that the inclination of the surface is reduced by 50% or more compared to the variation in torque coefficient value of a female screw part having a degree of tilt of 2 degrees or less.   When manufacturing female threaded parts by hot forging, cold forging, and cutting after cold drawing, it is manufactured so that the tilt of the seat surface relative to the male threaded shaft is 0.35 degrees or less, and the female thread is made smaller than the effective diameter. Cut to 0.2 to 0.3 mm smaller, plastically processed to the effective diameter with a rolling tap, and the variation in torque coefficient value is 80 compared to the variation in torque coefficient value of female thread parts with a seat surface tilt of 2 degrees or less. A method for producing a female screw part, characterized in that it is reduced by at least%.

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