Wire thread manufacturing process and quality control

1, material aspects

The material for manufacturing the wire screw sleeve is austenitic stainless steel wire of the Crl8Ni9 type. In the early stage of the development of wire screw sleeves, due to the limitations of material conditions and material standards at that time, 1Crl8Ni9Ti single grade material was selected in the formulation of standards. With the advancement of metallurgical technology, the popularity of low carbon stainless steel materials, the use of titanium to improve stainless steel resistance to crystal The measures of the boundary corrosion ability are not adopted. The original 1Crl8Ni9Ti can be completely replaced by OCrl8Ni9. For the wire screw sleeve, all the crl8Ni9 type materials (such as 1Crl8Ni9, OCrl8Ni9, 1Crl8Ni9Ti, etc.) under the normal working conditions, as long as the mechanical properties meet the requirements. ) can be used. At present, the wire screw sleeves at home and abroad are generally made of OCrl8Ni9 materials without special requirements.

OCrl8Ni9 is austenitic stainless steel. It can not be heat-treated and can only be strengthened by cold deformation. The degree of deformation is different. In order to ensure sufficient flexibility after forming the wire screw sleeve, the strength requirement must be made for the manufacture of the round wire for the wire screw sleeve. The tensile strength of the round wire is slightly lower than the strength of the diamond wire specified in the standard, so that the strength of the diamond wire after rolling forming Meet the standards. The strength of the steel wire of different cross-section dimensions is also different.

The round steel wire used to make the wire screw sleeve must have the same strength of the same bundle of steel wire.

The diameter of the round wire must be precise. For the wire screw sleeve produced according to the national standard, it can be formed by single-rolling. The diameter of the round wire directly determines the height of the diamond-shaped section after molding. The diameter of the round wire corresponding to each pitch needs to be Determined by experiment. Moreover, the diameter of the same bundle of steel wires must be uniform.

If the wire screw sleeve is produced according to the military standard, because it is an asymmetrical profile, the height of the external thread is higher than the height of the internal thread, and it is necessary to stand up to obtain an asymmetric tooth shape during the rolling process, when selecting the diameter of the round wire. It is necessary to increase the size slightly to ensure the asymmetrical profile size requirement by vertical rolling.

2. Rolling of diamond-shaped steel wire

The round-section steel wire is passed through a diamond-shaped groove formed by a pair of rolls, and is rolled into a diamond-shaped wire by multiple rolling, as shown in Fig. 22-12).

Figure 22-12

The quality of the diamond-shaped steel wire is the basis of the quality of the wire threaded bushing. With the high-quality diamond-shaped steel wire, the high-quality wire screw bushing can be obtained. The cross-section size of the diamond-shaped steel wire is required to be very precise, and the diamond-shaped cross-sectional dimension must be uniform along the length of the steel wire. This requires high precision for rolls and mills.

The cross-sectional dimensions of the diamond-shaped steel wire are determined by examining the dimensions of the wound wire profile.

According to the requirements of the national standard, the diamond threaded steel wire is used. As long as the diameter of the selected round wire is suitable, the single-direction rolling (rolling) can roll out the qualified profile size, in order to ensure that the profile height meets the standard requirements, the round wire The diameter must be selected.

When the production according to the requirements of military standards, the size of the crest forming the external thread is different from that of the crest forming the internal thread. In order to ensure that the internal and external thread crests meet the standard requirements, the profile must be rolled vertically. The crests forming the internal thread diameter are rolled to the standard required H/4. The crests that form the large diameter of the external thread must meet the requirements of H/8. This type of profile requires many problems for the production of wire thread inserts. In the rolling process, vertical rolling is required and the vertical rolling cannot be completed in the finish rolling, otherwise the stress generated at the rolling H/4 will affect the winding.

The bending deformation of the wire screw sleeve will cause a change in the angle of the inner and outer teeth. When the diamond-shaped steel wire is bent and deformed, the inner side is compressed and the outer side is stretched, and there is an intermediate layer which is neither stretched nor compressed in the middle, and the height of the profiled surface outside the interposer is lowered, the height of the inner layer of the interposer is increased, and the width of the interposer is constant. The outer angle of the profile increases and the inner angle decreases. The angle change is related to the diameter of the wire screw sleeve. The outer angle of the coarse thread increases by about 4°, and the inner angle decreases by about 4°. In order to improve the thread matching precision, the angle of the diamond-shaped steel wire profile of the coarse thread is corrected in the opposite direction in advance, and the outer angle is made 56°, the inner angle is made 64°, and the winding deformation is close to 60°, as shown in Fig. 22-13.

Figure 22-13

3, the processing of wire threaded sleeve

The roll-formed rhomboid steel wire is wound to form a wire screw sleeve, a handle is attached, and a fracture groove is guided and machined. For the locking type wire thread insert, a polygonal locking ring is formed in the middle of the wire screw sleeve. Blind hole type wire thread insert. No mounting handle, guide, and a tapered end.

The processing technology of wire thread inserts has developed rapidly in recent years. The operation mode of single-piece manual process has been developed into full-automatic production of special machine CNC, and the production efficiency has been greatly improved. Most of the wire screw sleeve CNC automatic winding machine is designed on the basis of the spring machine, and it is also designed on the basis of small lathes. It is still not perfect and needs to be improved.

The winding of the wire thread insert is core-wound, which is wound on the threaded mandrel, the outer diameter of the wire threaded sleeve, the guiding size, the position of the mounting handle, the polygonal shape of the locking ring and the tapered end of the blind hole type. It is formed by a wound mandrel. The winding mandrel is an important tool for the forming of the wire screw sleeve, and a good winding core rod can be processed to produce a high quality wire threaded sleeve product. Due to the influence of the strength and cross-section size of the diamond-shaped steel wire on the amount of springback after forming, the outer diameter of the wire screw sleeve, the guiding dimension, the position of the mounting handle, the locking torque of the locking wire screw sleeve, etc. should be processed first. The test piece is adjusted to the size of the wound mandrel and is produced after the test is passed.

With the increase in the amount of wire thread inserts. Installation efficiency is a problem that users are very concerned about. The application of pneumatic or electric installation tools puts higher requirements on the technical specifications of the free-state outer diameter size and the gap between the ring and the ring. For this reason, the steel wire material must be Rod diameter and winding process and tooling are strictly controlled to meet user needs.

The national standard and the military standard have different specifications for the profile, and the outer diameter of the free state is also different. It should be handled separately in production.

The broken groove is used to remove the mounting handle after the screw thread is screwed into the screw hole. Whether the mounting handle is continuously lost during the installation of the wire screw sleeve, the wire screw sleeve is screwed into the screw hole and then washed off with a handle tool. This is very important for users with large dosage. In order to ensure this function, the depth of the fracture groove, the radius of the bottom of the groove, the processing technology, the material strength, the heat treatment and other factors must be strictly controlled. The friction wheel processing effect is not as good as the special milling cutter. The effect is good.

4, heat treatment and cleaning

In order to eliminate the influence of the rolling and winding on the stress state of the material, the elasticity of the material is restored, and the formed wire screw sleeve is subjected to stress relief heat treatment. Before the heat treatment, the product should be degreased and cleaned. After heat treatment, the surface of the part will produce a light yellow oxide film, which needs to be brightly processed. The surface of the finished part should be clean and bright.

The wire thread insert without stress relief by heat treatment does not recover the elasticity of the material, and if it is bent sideways with a finger, it will be inclined and deformed.

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