WELDING METHOD FOR MANUFACTURING A BI-COMPOSITIONAL SCREW

A welding method for manufacturing a bi-compositional screw includes a preparing operation, a welding operation and a forming operation. The preparing operation prepares two raw blanks made of different materials and respectively processed to provide a front section and a rear section. The welding operation places the two sections on a positioning device to allow the two sections to meet closely at a joint along an axis, and then applies a welding device to weld the two sections at the joint in a circumferential direction when the two sections are rotated in the same rotational direction, thereby attaining a bi-compositional blank without causing waste extruded out of the joint. The forming operation forms a plurality of threads on the bi-compositional blank to forma bi-compositional screw. The method prevents the generation of air and pores inside the joint after welding, reduces processing costs, and ensures preferable processing quality.

BACKGROUND OF THIS INVENTION

1. Field of this Invention

This invention relates to a welding method and relates particularly to a welding method for manufacturing a bi-compositional screw.

2. Description of the Related Art

A bi-compositional screw is made through welding two raw blanks which are provided with different materials into a bi-compositional blank and processing the hi-compositional blank to form a hi-compositional screw afterward. Generally, two materials of the bi-compositional blank are processed into a head portion and a drilling portion of the hi-compositional screw respectively. The drilling portion is usually made of a material with the higher strength in order to allow the drilling portion to screw into an object which is provided with larger hardness such as an iron plate effectively. On the other hand, the head portion is usually made of an antirust material such as stainless steel because the head portion is exposed to the air after the screwing operation is finished. Hence, the bi-compositional screw is provided with ti e antirust effect and the higher strength to attain a preferable screwing action.

Referring toFIG. 1andFIG. 2, a conventional welding method1for manufacturing a hi-compositional screw2B includes a preparing operation11, a welding operation12, a trimming operation13, and a threading operation14. The preparing operation11prepares two raw blanks2which are made of different materials and processes the two raw blanks2into a front section21and a rear section22respectively to provide the front section21and the rear section22. The front section21further has a head211formed on an end of the front section21and a front end212formed on another end of the front section21opposite to the head211and defining a front welding surface212A. The rear section22has a rear end221defining a rear welding surface221A which faces the front welding surface212A and a drill end222in opposition to the rear end221. After that, the welding operation12restricts the head211and moves the rear section22toward a direction of the front section21to contact the front welding surface212A with the rear welding surface221A closely to form a joint C1, and thence rubs the front welding surface212A against the rear welding surface221A to increase the temperature of the joint C1, thereby melting the joint C1caused by frictional heat to combine the front and rear sections21,22into a bi-compositional blank2A. Afterward the trimming operation13removes unnecessary waste extruded out of the joint C1where the front and rear welding surfaces212A,221A meet to provide a smooth peripheral face of the bi-compositional blank2A. Finally, the threading operation14rolls a plurality of threads21on the bi-compositional blank2A to form a bi-compositional screw2B.

The conventional welding method1is executed by the front welding surface212A against the rear welding surface221A in order to integrate the front and rear sections21,22into the bi-compositional blank2A. However, the rubbing procedure will cause the generation of air and pores inside the joint C1to result in the reduced strength and quality of the bi-compositional blank2A. Meanwhile, the rubbing procedure will cause that part of the front end212and the rear end221are pressed to form waste extruded outwards of the joint C1. The waste is carbide formed under a high temperature. Therefore, the waste needs t be softened before removing by a trimming device (not shown) in the trimming operation13, or it will wear the trimming device. Thus, the processing costs are increased and additional procedures are required. Further, the processing difficulty is also increased and that requires to be improved.

SUMMARY OF THIS INVENTION

The object of this invention is to provide a welding method for manufacturing a bi-compositional screw capable of reducing waste, ensuring preferable processing quality and decreasing processing costs.

The welding method of this invention includes a preparing operation, a welding operation and a forming operation. The preparing operation prepares two raw blanks made of different materials, then processes the raw blanks into a front section and a rear section respectively. The front section has a head, a shank extending outwards from the head, and a front end connected to the shank in opposition to the head and defining a front welding surface. The rear section has a rear end defining a rear welding surface which faces the front welding surface and a drill end opposite to the rear end. An outer diameter of the front end is equal to an outer diameter of the rear end. The welding operation equips a welding device and a positioning device disposed below the welding device, then aligns the front and rear sections on the positioning device along a same axis to contact the front welding surface and the rear welding surface closely at a joint, and thence rotates the front and rear sections in the same rotational direction to allow the welding device circumferentially welds the front and rear sections at the joint to integrate the front and rear sections into a bi-compositional blank. Therefore, the welding method prevents air and pores from generating inside the joint and prevents waste from being extruded out of the joint. Finally, the forming operation rolls a plurality of threads on the bi-compositional blank to form a bi-compositional screw. Thus, the processing procedures are simplified, the processing costs are reduced, and the preferable processing quality is attained.

Preferably, the welding operation heats directly without adding additional solder.

Preferably, in the welding operation, the joint where the front end and the rear end meet is circumferentially welded by the welding device to prevent waste from being extruded out of the joint after welding.

Preferably, in the preparing operation, both of the front welding surface and the rear welding surface are formed in a flat surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring toFIGS. 3 to 5, a welding method3for manufacturing a hi-compositional screw4B of a first preferred embodiment of this invention includes a preparing operation31, a welding operation32, and a forming operation33. The preparing operation31prepares two raw blanks4which are provided with different materials and processes the two raw blanks4respectively to form a front section41and a rear section42, both of which are provided with smooth peripheral faces. The front section41has a head411, a shank412extending outwards from the head411, and a front end413with a front welding surface413A formed on the front section41opposite to the head411. The rear section42has a rear end421with a rear welding surface421A formed on an end of the rear section42and a drill end422formed on another end of the rear section42opposite to the rear end421. In this preferred embodiment, both of the front welding surface413A and the rear welding surface421A are formed in a flat surface. Meanwhile, an outer diameter413dof the front end413is equal to an outer diameter421dof the rear end421, thereby providing a smooth peripheral face of the bi-compositional blank4A thereafter and an equal circumference (not shown) from the shank412to the rear end421. Further, the front section41can be made of a corrosion-resisting material such as stainless steel. On the other hand, the rear section42can be made of a material with higher hardness such as martensite or hardened materials.

Referring toFIG. 3andFIG. 5, after the preparing operation31, the welding operation32prepares a welding device5and a positioning device6disposed below the welding device5, then position the front section41and the rear section42on the positioning device6to allow the front welding surface413A and the rear welding surface421A to contact closely along an axis R and meet at a joint C2, and thence rotates the front section41and the rear section42in the same rotational direction driven by the positioning device6and simultaneously welds the front end413and the rear end421at the joint C2in a circumferential direction executed by the welding device5which is disposed above the joint C2where the front end413and the rear end421meet, thereby integrating the front section41and the rear section42to provide a bi-compositional blank4A. Comparing with the robbing procedure of the conventional welding operation12, the welding operation32of this invention is executed by direct heating without applying additional solder, the welding operation32can prevent air and pores from generating inside the joint C2and prevents waste from being projected out of the joint C2effectively.

Thus, no additional trimming procedure is required in the welding method3before executing the forming operation33. After the welding operation32, the forming operation33rolls a plurality of threads41on the bi-compositional blank4A via a threading machine (not shown) to forma bi-compositional screw4B. The drill end422can be processed into a drilling tail via a tail forming machine (not shown) according to needs. Hence, a succession of the operations31,32,33including the preparing, welding and forming attains the quick and smooth manufacturing operation of the bi-compositional screw4B, simplifies the processing procedures effectively, reduces the processing costs, and ensures the preferable processing quality.

To sum up, the welding method of this invention includes the preparing operation, the welding operation and the forming operation. The preparing operation prepares and processes two raw blanks provided with different materials into the front section and rear section respectively. The welding operation circumferentially welds the front and rear sections which are placed in the same axis at the joint by the welding device during the rotation of the front and rear sections in the same rotational direction driven by the positioning device, thereby combining the front and rear sections into the bi-compositional blank. The forming operation forms a plurality of threads on the bi-compositional blank to produce the bi-compositional screw, thereby preventing the generation of air and pores inside the joint, avoiding causing additional waste extruded out of the joint, simplifying the processing procedures, reducing the processing costs, and ensuring the preferable processing quality.

While the embodiments of this invention are shown and described, it is understood that further variations and modifications may be made without departing from the scope of this invention.