Welding method and apparatus therefor

Abstract

A welding process involves a fixture for holding a workpiece and a welder, or welding electrode. The fixture imposes ultrasonic vibration on the workpiece. The welder vibrates during vibration, and is operable at a first voltage for elding and a second voltage for peening. The peening may occur while the weldmetal is crystallizing. The welding process may be a process of welding two parts together, or of filling a groove or other feature, or of applying or restoring a surface, or of applying a hard facing or ceramic to a parent metal or object. The weldmetal may be the same, or substantially the same, as the parent metal, or it may be different. The different material may be a ceramic material.

We claim: 
     
         1 . A welding apparatus comprising:
 a fixture to which to secure at least one workpiece;   a welding head positioned to address a workpiece held in the fixture;   said fixture having a vibration source by which to transmit vibration to the workpiece; and   said welding head being one at least of
 (a) operable during welding to vary voltage between a first magnitude and a second magnitude; and 
 (b) operable during welding to vibrate independently of said fixture. 
   
     
     
         2 . The welding apparatus of  claim 1  wherein said apparatus includes at least one ultrasonic vibration head operable to transmit ultrasonic vibration to the workpiece during welding. 
     
     
         3 . The welding apparatus of  claim 1  wherein said apparatus includes a power source operable to drive said welding head in a welding mode and in a peening mode. 
     
     
         4 . The welding apparatus of  claim 1  wherein at least one of said fixture and said welding head includes a motion transmitting drive apart from a vibration drive, said motion transmitting drive being operable globally to cause relative motion between the fixture and the welding head. 
     
     
         5 . The welding apparatus of  claim 5  wherein at least one of said fixture and said welding head is programmable to move according to a pre-set course. 
     
     
         6 . The welding apparatus of  claim 1  wherein, in use, the welding head is biased against the workpiece. 
     
     
         7 . The welding apparatus of  claim 1  wherein the vibration source of the fixture has an engagement member for contacting the workpiece, and said engagement member is free from plastic deformation elements. 
     
     
         8 . The welding apparatus of  claim 1  wherein said welding apparatus is both
 (a) operable during welding to vary voltage between a first magnitude and a second magnitude; and 
 (b) operable during welding to vibrate independently of said fixture. 
 
     
     
         9 . A method of welding a workpiece, said method comprising:
 mounting a vibration source to transmit a first vibration signal to the workpiece;   opposing the workpiece with a welder;   operating the welder according to at least one of:
 (a) operating at a first voltage magnitude for a first time period; and operating at a second voltage magnitude at a second time period; and 
 (b) vibrating the welder according to a second vibration signal; and 
   operating the vibration source while operating the welder.   
     
     
         10 . The method of  claim 9  wherein said method includes vibrating the welder to peen deposited weld metal during transmission of the first vibration signal. 
     
     
         11 . The method of  claim 9  wherein the second voltage magnitude is zero. 
     
     
         12 . The method of  claim 9  wherein said method includes securing the workpiece in a fixture. 
     
     
         13 . The method of  claim 12  wherein said method includes moving at least one of the fixture and the welding head along a pre-programmed path while transmitting said first vibration signal to the workpiece. 
     
     
         14 . The method of  claim 9  wherein the workpiece has more than one part, and said method includes welding at least two parts of the workpiece together. 
     
     
         15 . The method of  claim 9  wherein the method includes operating the welder to deposit a material on the workpiece that is different from the parent material of the workpiece. 
     
     
         16 . The method of  claim 9  wherein said method is a method of surface coating the workpiece. 
     
     
         17 . The method of  claim 9  wherein the first vibration signal is an ultrasonic vibration signal said method includes both
 (a) operating at a first voltage magnitude for a first time period; and operating at a second voltage magnitude at a second time period; and 
 (b) vibrating the welder according to a second vibration signal; and operating the vibration source while operating the welder. 
 
     
     
         18 . The welding process of  claim 9  wherein ultrasonic vibration is applied directly to the workpiece during at least one of:
 (a) application of a welding rod to the workpiece; 
 (b) crystallization of welded material; and 
 (c) peening of welded material. 
 
     
     
         19 . The welding process of  claim 18  wherein ultrasonic vibration is applied to the workpiece during at least two of:
 (a) application of a welding rod to the workpiece; 
 (b) crystallization of welded material; and 
 (c) peening of welded material. 
 
     
     
         20 . The welding process of  claim 19  wherein said welding process is an ESD process and the welder uses a welding rod having a ceramic material composition that includes at least one of (a) TiC; and (b) TiB 2 .