CA1187143A - Method for double end stud welding - Google Patents
Method for double end stud weldingInfo
- Publication number
- CA1187143A CA1187143A CA000403187A CA403187A CA1187143A CA 1187143 A CA1187143 A CA 1187143A CA 000403187 A CA000403187 A CA 000403187A CA 403187 A CA403187 A CA 403187A CA 1187143 A CA1187143 A CA 1187143A
- Authority
- CA
- Canada
- Prior art keywords
- stud
- welding
- projections
- contact
- arc
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/20—Stud welding
- B23K9/201—Stud welding of the extremity of a small piece on a great or large basis
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Mechanical Engineering (AREA)
- Arc Welding Control (AREA)
- Arc Welding In General (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Method and apparatus for simultaneously welding by the stud end welding technique a stud having two or more ends.
The stud includes at least one elongated relatively thin metallic projection from each end of the stud to be welded. The method and apparatus maintains a current density in a given projection sufficient to disintegrate the projection with consequent arc initiation. The resultant arcs melt all stud ends and plate.
The molten ends are lowered into the pools at a controlled rate at which time the current is extinguished and the material solidifies.
Method and apparatus for simultaneously welding by the stud end welding technique a stud having two or more ends.
The stud includes at least one elongated relatively thin metallic projection from each end of the stud to be welded. The method and apparatus maintains a current density in a given projection sufficient to disintegrate the projection with consequent arc initiation. The resultant arcs melt all stud ends and plate.
The molten ends are lowered into the pools at a controlled rate at which time the current is extinguished and the material solidifies.
Description
FIELD OF INVENTION
The present invention applies to -the art of stud welding and more particularly -to methods for welding s-tuds having two or more ends and to the design of such studs.
BACKGROUND OF INVENTION
The present invention relates to stud welding methods and, more particularly, to methods for weldiny, by the stud end welding technique, a stud having a plurali-ty of ends which are to be simultaneously welded to a workplece.
The stud end welding technique has been known and in practical commercial use for many years. In this welding -tech-nique, a single end of a metallic member, such as a threaded bolt or the like, is welded to a metallic member generally known as a base member by the application of sufficiently high current passing through -the stud and across an arc between the stud and the workpiece to create a molten pool of metal into which the stud is ul-timately plunged and secured following solidification of the molten pool.
There are many varia-tions of this technique. ~Iowever, _ lv ~
the tcchnique is generally divided into two major categories, i.e. drawn arc stud welding and capacitor discharge stud welding. In drawn arc stud welding current is passed through the stud to be welded while in contact with the workpiece and then lifted to create an arc between the stud and workpiece.
After sufficient time passes to permit the arc to create melting of the stud and workpiece, the stud is returned to the workpiece into the molten pool of metal. In this mode of welding, an arc shield is placed around the end of the stud and in contact with the workpiece to contain the molten pool of metal to form a weld fillet following solidification of the metal. This technique is used for larger diameter studs or the conven~ional shear connectors in ranges generally in excess of ~" of diameter.
The drawn arc stud welding technique generally employs a ro-mded, square or rectangular configuration on the end of the stud to be welded. The current density passing through the end of the stud being welded is relatively low compared to capacitor discharge welding as will be discussed hereinafter and is generally in the area of approximately S,000 amps per square inch.
The weld time for drawn arc stud welding varies depending on the application and the diameter of the stud but i~ is generally in the area of approximately .5 seconds for an average application for welding of a ~" stud. Thus, drawn .~arc stud welding is generally considered to be a longer low current welding process with essentially arc creation resulting in melting of the stud and the workpiece with little or no significant instantaneous disintegration of the end of the stud.
The capacitor discharge stud welding technique differs significant-ly from the drawn arc stud end welding technique in many ways. In capacitor discharge stud welding, the power source is not a continuous power source as in drawn arc stud welding but is a 3L~ 3 stored energy source 9UCll as -that from a bank of capacitors which have been charged to a predetermined level before ini~ia-tion of the welding cycle. Additionally, the studs utilized in capacitor clischarge stud welding are usually of a small diameter in the range of ~" or less and also inclucle a small diameter and length welding tip on the end of the stud. The welding tip serves to space the end of the stud to be welded from the work-piece at the beginning of the welding cycle. Upon initiation of the welding cycle, the readily available energy supply from the energy source such as the capacitors is dumped throu~h the s-tud at an extremely high current density r~sulting in complete d.isin-tegration and vapori~ation of the welding tip. The disintegra tion of the welding tip momentarily leaves the stud spaced from the workpiece while ~n arc is established between the stud and the workpiece substantially along the entire face of the stud due to the high energy level of the capacitors.
In an average capacitor discharge stud welding envi--ronment, the current density passing through the tip of the welding stud is, momentarlly, in the range of appro~imately 10,000,000 amps per square inch. mhis flash of high density current is substantially instantaneous and the entire weld cyele for an average capacitor discharge welding cyele is approxi-mately .003 seconds.
Capacitor discharge welding is used primarily but not restricted to rather small studs, high production rates and with thin sheet base material which cannot withstand the longer weld-r;~'~ ing and heating cycles of a~c stud welding~ Additionally, the weld strength of a capacitor discharge weld is somewhat less than that of theJ;arc stud welding technique.
The stuc~ end welding technique, eithe~;,arc stud welding or capacitor discharge stud welding, has not, heretofore, been r ~
1~L871~
successfully used in the welding of studs having two or more ends v .. ,~ (~ 'c~-~
which~E-eq-~l-Ee to be welded simultaneously to the base mernber.
There are numerous stud configurations which have two or more ends which are required to be welded and thus cannot utilize the stud end welding techniaue. Examples of such studs are double ended lifting hooks, handles and hold-down loops all of which must be welded by electric or gas hand welding.
Another major category o~ stud which includes two or more ends and which must currently be hand welded is the double ended shear connector. A double ended shear connector is a U-shaped metallic me~ber which is welded to an I-beam or the li~e and is later embedded in concrete lying upon the I-beam to provide a shear interconnection between the concrete slab lying upon the beam and the beam itself.
There are basica]ly two or more types of shear connec-tors in use in the industry today. One kind is the headed shear connector which is an elongate rod like member having one end weldable thereon and an enlarged flanged hea~ at the opposite end This stu~ is generally of round configuration and of approximatel~
5/8 to 7/8 inches in diameter and is capable of being welded by G~
the conventional~arc stud welding technique. Another design of shear connector conventionally in use is a generally U-shaped member of rectangular cross section of approximately eight gage thickness and 1 inches wide with a height of approximately 3 inches and a separation of the two legs of approximately ~ 5/8 inches. This class of shear connector may be referred to as the double ended shear connector whereas the single elongate shear connector is generally known as the headed shear connector.
~ double ended shear connector of less total metal weight than a headed shear connector can still provide equal or greater shear resistance when welded in place. Thus, the r~ ~ ~ ~
3~87~3 material costs and performance of a double ended shear connector is superior to that of a headed shear connector. However, -the double ended shear connec-tor suffers from the disadvantage ln that it must be manua~ly welded and has not, heretofore, been ca~able of being welded by the stud end welding technique. The hand welding technique ls more time consuming than the stud end welding technique and, additionally, the skill and time required to manually weld the double ended shear connector is greater than that required of the operator for the stud end welding technique with the further consbquent addition of expense in the trade utilized. According-ly, there is a real industry need for a method and apparatus to ~Jeld double ended shear connectors by the stud end welding technique.
Different techniques have,in the past, been attempted to arrive at apparatus and methods to successfully weld multi-ended studs. The foremost problem encountered with the welding operation of double ended studs is the initiation of an arc on both legs of the studr If the arc initiates on one leg and nothing is done to enhance initiation on the other leg, the arc will continue to operate on the first l.eg and the second arc will not be initiate~. There are two main reasons for this occurrence. First, the operating arc will cause a large voltage drop from the open circuit voltage. This will make it increas ingly difficult to break down the air gap resistance at the unarcing leg. Secondly, the heating of the arcing leg will lowex the work function and increase the elec-tron flow at that point, effectively lowering the resistance. These two effects comhine to make it extremely difficult to initiate a second axc at the remaining legs once there has been the estahlishment of a firs-t arc.
The desired solution to this problem of single arc .,._ initiation is to initiate arcs on both legs of the stud simul-taneously. However, with the conventional stud welding apparatus and method of stud liftoff initiation, it is nearly impossible to maintain equal initial arc gaps. Even a very small difference in sap size works to prevent one arc from starting b~cause the breakdown voltage can be in the order of 1,000 volts/mil. in air.
Both legs must leave the base plate surface at exactly the same time or only one arc will occur.
Assuming that dual arcs can be initiated, the second problem encountered is to insure that equal welding takes place on both legs of the stud. Essentially, this means that equal welding currents must be maintained in both legs. Dlfferences in cuxrentreadily result from such conditions as oxides on the S~ ,Je work surface or -s~t-t-~e changes in metal trar~sferred through either arc. ~ccordingly, it is extremely difficult if not impossible to maintain equal current density in the welding legs and thus, uneven melting occurs with the consequence of one leg of the double ended stud ~ ~g not being sufficiently welded.
One attempt made at solving the problem of establishing and regulating arcing between the two legs of a double ended stud was to place an insulator between the two lègs and apply separate current sources to the welding legs. Such a concept is disclosed in the U. S. Patent No. 2,788,434. This solution suffers the rather critical disadvantage of the two legs of the stud being separated by a weak insulator between the -two legs which seriously reduces the strength of the stud.
Another solution tried was to vary the geometry of the ends of the double ended stud by u-tilizing su~h configurations as chisel points as well as other configurations such as pointed ends, rounded ends and square ends. In some cases, fluxes were used to help lo~er the ionization potential and provide a r --.. . . . ... .. .. ~
11~714;3 shielding atmosphere. The use of differing stud end confiyura tions and Eluxes did not prove successful. In a few cases, two arcs would occur at the two legs. However, one arc was always larger than the other. The smaller arc usually produced no melting of either the stud or the base plate. The lighter arc generally became nothing more than a brief spark which caused slight heating of the stud and the base plate. The utilization of fluxes aided slightly in the process but still did not result in sound commercially acceptable welds. Even compounds that exhibit lower ionizatl~on potential and higher electroconductivity than iron, although aiding in establishing arcs on both stud legs, did not effectively and consistently initiate the required dual arcs.
Another approach which has been investigated but found unsuccessful for doub,le ended stud weldirlg is that based upon the principles of arc gap effect and arc initiation and thermal emissivity at elevated temperatures. In this approach, the hypothesis is that, if the arc could be briefly extinguished on the operating leg by removal of the welding power, then the arc could be reignited on the opposite leg by virtue of that being the shortest a,rc path. It was postulated that, in order for the shorter path effect to dominate, the time that the arc was exti.nguished would have to be sufficient to allow a complete dissipation of the electron cloud and for the arc atmosphere to cool below levels where thermal igni,tion effects dorninate.
In this approach, the power supply providing the weldin current to the double ended welding stud was operated through a controller in a manner such that the welding current was rapidly turned on and off to -the welding stud in bursts of energy spaced one from another in the order of 100 milliseconds. In some instances, dual arcing at bo-th legs of the double ended stud were ~ ~7~
achieved. However, control of positioning the stud with respect ~o the workpiece was extremely delicate and difficult and the control of the arcing between the two legs was erratic and generally unsatisfac-tory welds resulted.
SUMMARY OF INVENTION
The foregoing problems encountered in weldi.ng of studs having two or more ends by the stud end welding technique are overcome by the studs, methods and apparatus as hereinafter described.
1.0 The invention provides the method of simultaneously stud welding the ends of a multi-ended metallic stud to a meta].lic base member comprising the steps of: providing on each of the stud at least one elongate relatively thin metallic extending projection; applying a controlled pressure upon the stud in the direction of the base member; applying an electrical potential to the stud from a continuous current power supply;
bringing the metallic projections into contact with the metallic base member; and controlling the pressure on and the rate of advance of the stud toward the workpiece and controlling the electrical potential upon the stud all in proportion to one another and to the configuration of -the projections and stud ends to (1) provide a current density in the projections to essentially immediately and simultaneously disintegrate the pro-jections to establish arc initiation at all ends of the metallic stud and (2) thereafter maintain a continuous arc at all ends of the metallic stud of duration and current density a-t leas-t equaling that of drawn arc stud welding to maintai.n molten metal at each end thereof until the ends of the stud corne into contact with the base material. In larger s-tudsl two or -more projections or wires can be employed for each stud end.
The stud welding apparatus described herein includes a chuck for securing the stud which is of configuration comple-'~
mentary to the upper portion of the double ended stud. The chuck maintains the welding stud in proper orientation with respect to the weld base in order tha-t the projections will strike the weld base essentially simultaneously. The welding apparatus further includes a welding gun footpiece which secures two arc shields properly in place in alignment with the welding ends of the double ended stud.
There are four methods that can be employed in double end welding each of which employs a projection or projections 1/16" in diameter or greater by 1/16" long or longer or conical in nature.
One method entails holding the stud away from the work surface, establishing a welding voltage between the stud and the work then advancing the stud toward the work until the projection or projections contact the work whereby arcs are established '~' -8a-~L8'~3 between both stud ends and the work and then continue the forward motion of the stud until contact between stud end and work occur extinguishing the arcs.
A second method is similar except that when contact occurs and arcing begins, the resultant current flow in the circuit energizes a current relay which actuates a circuit to stop the forward motion of the stud for a time suitable to provide adequate melting of stud and work and then plunging the stud into the molten pool completing the weld.
A third method is to initially contact the stud projection or projections with the work under sufficient pressure to insure contact then connecting them to a source of welding power, creating an arc between both ends of the stud and the work, and then advancing the stud to the work at a controlled rate until contact between stud and work is made thus completing the weld.
A fourth method is similar to the third excep-t that when the arcs between the stud ends and the work is initiated, the stud is held immobile for a predetermined time then plunged into the molten pool completing the weld.
I'he welding power supply utilized is a continuous current welding supply. The welding power supply is operated in a manner to provide welding current density across the welding tip projections or wires of a density suf-ficient to disintegrate each projection permitting consequellt arc initiation.The relatively thin projection assures arc initiation at both legs of the double ended stud. Both arcs are maintained through high current densities while the stud is lowered into the resulting molten pools whereupon the arc is extinguished and the current swltched off.
Other features, advantages and variations of the studs, apparatus and methods of multiended stud welding of the present invention will become apparent to those skilled in the art form 11871'13 the 1 tailed description thereo~ whicll follows talcen in conjunc- ¦
tion with the drawing.
DETAILED DESCRIPTION OF DRAWING
Figure 1 is a perspective view, partially in section, of a double ended shear connector in accordance with the present invehtion welded in place in conjunction with a supporting member and concrete slabi Figure 2 is an elevational view of a double ended shear connector in accordance with the present invention;
Figure 3 is a perspective view of a portion of the welding apparatus, shear connector and arc shields prior to welding in accordance with the present invention; and Figure 4 is a perspective view of a portion of the welding apparatus and shear connector following welding thereof.
DETAILED DESCRIPTION OF INVENTION
. . ...
The foregoing detailed description of the studs, methods and apparatus for welding studs by the stud end welding technique wherein the studs have two or more ends to be simul-taneously welded will be undertaken in respect to a double ended stud of the double ended shear connecto`r type essentially as shown in Figures 1 and 2. However, it is to be understood that the present method and apparatus applies to and may be utilized in the welding of other configurations of studs as well as studs having more than two ends to be welded.
A double ended stud of a configuration suitable for use as a double ended shear connector is shown in Figures 1 and
The present invention applies to -the art of stud welding and more particularly -to methods for welding s-tuds having two or more ends and to the design of such studs.
BACKGROUND OF INVENTION
The present invention relates to stud welding methods and, more particularly, to methods for weldiny, by the stud end welding technique, a stud having a plurali-ty of ends which are to be simultaneously welded to a workplece.
The stud end welding technique has been known and in practical commercial use for many years. In this welding -tech-nique, a single end of a metallic member, such as a threaded bolt or the like, is welded to a metallic member generally known as a base member by the application of sufficiently high current passing through -the stud and across an arc between the stud and the workpiece to create a molten pool of metal into which the stud is ul-timately plunged and secured following solidification of the molten pool.
There are many varia-tions of this technique. ~Iowever, _ lv ~
the tcchnique is generally divided into two major categories, i.e. drawn arc stud welding and capacitor discharge stud welding. In drawn arc stud welding current is passed through the stud to be welded while in contact with the workpiece and then lifted to create an arc between the stud and workpiece.
After sufficient time passes to permit the arc to create melting of the stud and workpiece, the stud is returned to the workpiece into the molten pool of metal. In this mode of welding, an arc shield is placed around the end of the stud and in contact with the workpiece to contain the molten pool of metal to form a weld fillet following solidification of the metal. This technique is used for larger diameter studs or the conven~ional shear connectors in ranges generally in excess of ~" of diameter.
The drawn arc stud welding technique generally employs a ro-mded, square or rectangular configuration on the end of the stud to be welded. The current density passing through the end of the stud being welded is relatively low compared to capacitor discharge welding as will be discussed hereinafter and is generally in the area of approximately S,000 amps per square inch.
The weld time for drawn arc stud welding varies depending on the application and the diameter of the stud but i~ is generally in the area of approximately .5 seconds for an average application for welding of a ~" stud. Thus, drawn .~arc stud welding is generally considered to be a longer low current welding process with essentially arc creation resulting in melting of the stud and the workpiece with little or no significant instantaneous disintegration of the end of the stud.
The capacitor discharge stud welding technique differs significant-ly from the drawn arc stud end welding technique in many ways. In capacitor discharge stud welding, the power source is not a continuous power source as in drawn arc stud welding but is a 3L~ 3 stored energy source 9UCll as -that from a bank of capacitors which have been charged to a predetermined level before ini~ia-tion of the welding cycle. Additionally, the studs utilized in capacitor clischarge stud welding are usually of a small diameter in the range of ~" or less and also inclucle a small diameter and length welding tip on the end of the stud. The welding tip serves to space the end of the stud to be welded from the work-piece at the beginning of the welding cycle. Upon initiation of the welding cycle, the readily available energy supply from the energy source such as the capacitors is dumped throu~h the s-tud at an extremely high current density r~sulting in complete d.isin-tegration and vapori~ation of the welding tip. The disintegra tion of the welding tip momentarily leaves the stud spaced from the workpiece while ~n arc is established between the stud and the workpiece substantially along the entire face of the stud due to the high energy level of the capacitors.
In an average capacitor discharge stud welding envi--ronment, the current density passing through the tip of the welding stud is, momentarlly, in the range of appro~imately 10,000,000 amps per square inch. mhis flash of high density current is substantially instantaneous and the entire weld cyele for an average capacitor discharge welding cyele is approxi-mately .003 seconds.
Capacitor discharge welding is used primarily but not restricted to rather small studs, high production rates and with thin sheet base material which cannot withstand the longer weld-r;~'~ ing and heating cycles of a~c stud welding~ Additionally, the weld strength of a capacitor discharge weld is somewhat less than that of theJ;arc stud welding technique.
The stuc~ end welding technique, eithe~;,arc stud welding or capacitor discharge stud welding, has not, heretofore, been r ~
1~L871~
successfully used in the welding of studs having two or more ends v .. ,~ (~ 'c~-~
which~E-eq-~l-Ee to be welded simultaneously to the base mernber.
There are numerous stud configurations which have two or more ends which are required to be welded and thus cannot utilize the stud end welding techniaue. Examples of such studs are double ended lifting hooks, handles and hold-down loops all of which must be welded by electric or gas hand welding.
Another major category o~ stud which includes two or more ends and which must currently be hand welded is the double ended shear connector. A double ended shear connector is a U-shaped metallic me~ber which is welded to an I-beam or the li~e and is later embedded in concrete lying upon the I-beam to provide a shear interconnection between the concrete slab lying upon the beam and the beam itself.
There are basica]ly two or more types of shear connec-tors in use in the industry today. One kind is the headed shear connector which is an elongate rod like member having one end weldable thereon and an enlarged flanged hea~ at the opposite end This stu~ is generally of round configuration and of approximatel~
5/8 to 7/8 inches in diameter and is capable of being welded by G~
the conventional~arc stud welding technique. Another design of shear connector conventionally in use is a generally U-shaped member of rectangular cross section of approximately eight gage thickness and 1 inches wide with a height of approximately 3 inches and a separation of the two legs of approximately ~ 5/8 inches. This class of shear connector may be referred to as the double ended shear connector whereas the single elongate shear connector is generally known as the headed shear connector.
~ double ended shear connector of less total metal weight than a headed shear connector can still provide equal or greater shear resistance when welded in place. Thus, the r~ ~ ~ ~
3~87~3 material costs and performance of a double ended shear connector is superior to that of a headed shear connector. However, -the double ended shear connec-tor suffers from the disadvantage ln that it must be manua~ly welded and has not, heretofore, been ca~able of being welded by the stud end welding technique. The hand welding technique ls more time consuming than the stud end welding technique and, additionally, the skill and time required to manually weld the double ended shear connector is greater than that required of the operator for the stud end welding technique with the further consbquent addition of expense in the trade utilized. According-ly, there is a real industry need for a method and apparatus to ~Jeld double ended shear connectors by the stud end welding technique.
Different techniques have,in the past, been attempted to arrive at apparatus and methods to successfully weld multi-ended studs. The foremost problem encountered with the welding operation of double ended studs is the initiation of an arc on both legs of the studr If the arc initiates on one leg and nothing is done to enhance initiation on the other leg, the arc will continue to operate on the first l.eg and the second arc will not be initiate~. There are two main reasons for this occurrence. First, the operating arc will cause a large voltage drop from the open circuit voltage. This will make it increas ingly difficult to break down the air gap resistance at the unarcing leg. Secondly, the heating of the arcing leg will lowex the work function and increase the elec-tron flow at that point, effectively lowering the resistance. These two effects comhine to make it extremely difficult to initiate a second axc at the remaining legs once there has been the estahlishment of a firs-t arc.
The desired solution to this problem of single arc .,._ initiation is to initiate arcs on both legs of the stud simul-taneously. However, with the conventional stud welding apparatus and method of stud liftoff initiation, it is nearly impossible to maintain equal initial arc gaps. Even a very small difference in sap size works to prevent one arc from starting b~cause the breakdown voltage can be in the order of 1,000 volts/mil. in air.
Both legs must leave the base plate surface at exactly the same time or only one arc will occur.
Assuming that dual arcs can be initiated, the second problem encountered is to insure that equal welding takes place on both legs of the stud. Essentially, this means that equal welding currents must be maintained in both legs. Dlfferences in cuxrentreadily result from such conditions as oxides on the S~ ,Je work surface or -s~t-t-~e changes in metal trar~sferred through either arc. ~ccordingly, it is extremely difficult if not impossible to maintain equal current density in the welding legs and thus, uneven melting occurs with the consequence of one leg of the double ended stud ~ ~g not being sufficiently welded.
One attempt made at solving the problem of establishing and regulating arcing between the two legs of a double ended stud was to place an insulator between the two lègs and apply separate current sources to the welding legs. Such a concept is disclosed in the U. S. Patent No. 2,788,434. This solution suffers the rather critical disadvantage of the two legs of the stud being separated by a weak insulator between the -two legs which seriously reduces the strength of the stud.
Another solution tried was to vary the geometry of the ends of the double ended stud by u-tilizing su~h configurations as chisel points as well as other configurations such as pointed ends, rounded ends and square ends. In some cases, fluxes were used to help lo~er the ionization potential and provide a r --.. . . . ... .. .. ~
11~714;3 shielding atmosphere. The use of differing stud end confiyura tions and Eluxes did not prove successful. In a few cases, two arcs would occur at the two legs. However, one arc was always larger than the other. The smaller arc usually produced no melting of either the stud or the base plate. The lighter arc generally became nothing more than a brief spark which caused slight heating of the stud and the base plate. The utilization of fluxes aided slightly in the process but still did not result in sound commercially acceptable welds. Even compounds that exhibit lower ionizatl~on potential and higher electroconductivity than iron, although aiding in establishing arcs on both stud legs, did not effectively and consistently initiate the required dual arcs.
Another approach which has been investigated but found unsuccessful for doub,le ended stud weldirlg is that based upon the principles of arc gap effect and arc initiation and thermal emissivity at elevated temperatures. In this approach, the hypothesis is that, if the arc could be briefly extinguished on the operating leg by removal of the welding power, then the arc could be reignited on the opposite leg by virtue of that being the shortest a,rc path. It was postulated that, in order for the shorter path effect to dominate, the time that the arc was exti.nguished would have to be sufficient to allow a complete dissipation of the electron cloud and for the arc atmosphere to cool below levels where thermal igni,tion effects dorninate.
In this approach, the power supply providing the weldin current to the double ended welding stud was operated through a controller in a manner such that the welding current was rapidly turned on and off to -the welding stud in bursts of energy spaced one from another in the order of 100 milliseconds. In some instances, dual arcing at bo-th legs of the double ended stud were ~ ~7~
achieved. However, control of positioning the stud with respect ~o the workpiece was extremely delicate and difficult and the control of the arcing between the two legs was erratic and generally unsatisfac-tory welds resulted.
SUMMARY OF INVENTION
The foregoing problems encountered in weldi.ng of studs having two or more ends by the stud end welding technique are overcome by the studs, methods and apparatus as hereinafter described.
1.0 The invention provides the method of simultaneously stud welding the ends of a multi-ended metallic stud to a meta].lic base member comprising the steps of: providing on each of the stud at least one elongate relatively thin metallic extending projection; applying a controlled pressure upon the stud in the direction of the base member; applying an electrical potential to the stud from a continuous current power supply;
bringing the metallic projections into contact with the metallic base member; and controlling the pressure on and the rate of advance of the stud toward the workpiece and controlling the electrical potential upon the stud all in proportion to one another and to the configuration of -the projections and stud ends to (1) provide a current density in the projections to essentially immediately and simultaneously disintegrate the pro-jections to establish arc initiation at all ends of the metallic stud and (2) thereafter maintain a continuous arc at all ends of the metallic stud of duration and current density a-t leas-t equaling that of drawn arc stud welding to maintai.n molten metal at each end thereof until the ends of the stud corne into contact with the base material. In larger s-tudsl two or -more projections or wires can be employed for each stud end.
The stud welding apparatus described herein includes a chuck for securing the stud which is of configuration comple-'~
mentary to the upper portion of the double ended stud. The chuck maintains the welding stud in proper orientation with respect to the weld base in order tha-t the projections will strike the weld base essentially simultaneously. The welding apparatus further includes a welding gun footpiece which secures two arc shields properly in place in alignment with the welding ends of the double ended stud.
There are four methods that can be employed in double end welding each of which employs a projection or projections 1/16" in diameter or greater by 1/16" long or longer or conical in nature.
One method entails holding the stud away from the work surface, establishing a welding voltage between the stud and the work then advancing the stud toward the work until the projection or projections contact the work whereby arcs are established '~' -8a-~L8'~3 between both stud ends and the work and then continue the forward motion of the stud until contact between stud end and work occur extinguishing the arcs.
A second method is similar except that when contact occurs and arcing begins, the resultant current flow in the circuit energizes a current relay which actuates a circuit to stop the forward motion of the stud for a time suitable to provide adequate melting of stud and work and then plunging the stud into the molten pool completing the weld.
A third method is to initially contact the stud projection or projections with the work under sufficient pressure to insure contact then connecting them to a source of welding power, creating an arc between both ends of the stud and the work, and then advancing the stud to the work at a controlled rate until contact between stud and work is made thus completing the weld.
A fourth method is similar to the third excep-t that when the arcs between the stud ends and the work is initiated, the stud is held immobile for a predetermined time then plunged into the molten pool completing the weld.
I'he welding power supply utilized is a continuous current welding supply. The welding power supply is operated in a manner to provide welding current density across the welding tip projections or wires of a density suf-ficient to disintegrate each projection permitting consequellt arc initiation.The relatively thin projection assures arc initiation at both legs of the double ended stud. Both arcs are maintained through high current densities while the stud is lowered into the resulting molten pools whereupon the arc is extinguished and the current swltched off.
Other features, advantages and variations of the studs, apparatus and methods of multiended stud welding of the present invention will become apparent to those skilled in the art form 11871'13 the 1 tailed description thereo~ whicll follows talcen in conjunc- ¦
tion with the drawing.
DETAILED DESCRIPTION OF DRAWING
Figure 1 is a perspective view, partially in section, of a double ended shear connector in accordance with the present invehtion welded in place in conjunction with a supporting member and concrete slabi Figure 2 is an elevational view of a double ended shear connector in accordance with the present invention;
Figure 3 is a perspective view of a portion of the welding apparatus, shear connector and arc shields prior to welding in accordance with the present invention; and Figure 4 is a perspective view of a portion of the welding apparatus and shear connector following welding thereof.
DETAILED DESCRIPTION OF INVENTION
. . ...
The foregoing detailed description of the studs, methods and apparatus for welding studs by the stud end welding technique wherein the studs have two or more ends to be simul-taneously welded will be undertaken in respect to a double ended stud of the double ended shear connecto`r type essentially as shown in Figures 1 and 2. However, it is to be understood that the present method and apparatus applies to and may be utilized in the welding of other configurations of studs as well as studs having more than two ends to be welded.
A double ended stud of a configuration suitable for use as a double ended shear connector is shown in Figures 1 and
2 o~ the drawing. The double ended stud 10 is shown utilized ~? as a shear connector and is shown in Figure~ 1 we]ded in place upon an I-beam 11.
~~
In use, -the stud 10 is welded to thc I-beam 11 directly upon the I-beam or, in some instances, through decking 12 which is utili~ed as the bottom form member and protection for a concrete slab to ultimately be poured upon and supported by the I-beam 11.
A shear connector 10, welded in place, is shown partially embedded in a slab of concrete 13 as it would appear in actual use. The shear connec-tor 10 provides an interconnection between the I-beam 11 and the slab 13 to resist shearing action of the concrete slab 13 in respect to the supporting beam 11 in a heretofore known manner.
The details of the shear connector design of double ended stud of the present invention is shown in Figure 2 of the drawing. The shear comlector stud 10 includes two welcl ends 14 and 15. The ends 14 and 15 oE the stud are disposed in a common p]ane.
A pair of stud legs or portions 16 and 17 of the stud adjacent each end 14 and 15 thereof are formed straight. This straight leg or portion is disposed generally perpendicular to the weld base UpOII which the stud is to be welded and is necessary for cooperation with the configuration of the arc shields which are used in the process and which will be described hereinafter.
The remainder of the stud 10 includes a stud body 18 disposed between the legs 16 and 17 which may be of differing configurations from flat to U-shaped. In a preferred embodiment, the stud body is of a parabolic configuration.
The parabolic configuration of the remaining portion or body 18 of the stud provides for ready orientation of the stud in a stud welding chuck due to the noncircular configuration of the parabolic curve. Additionally, the parabolic configuration is of a shorter profile than a circular configur-ation and results in a material savings of approximately 17% to 25% over a circular configuration of -the same height without distracting from the shear strength capabilities of the stud.
The cross section of the stud 10 may be of any desired configur-ation, i.e. round,eliptical or rectangular. In a preferred embodiment, the stud is of rectangular configuration as shown in ~igures 1 and 2 of the drawing.
The weld ends 14 and 15 of the stud 10 are provided with elongate relatively thin projections or wires 19 extending parallel to the longitud-inal axis of the legs and Perpendicularly from the weld face of the weld ends 14 and 15 and thus, extend perpendicular to the weld base upon which the stud is to be welded. The projections or wires 19 may be formed of the parent metal of the stud during manufacture of the stud.
Alternately, the projections or wires may be affixed to the stud by any suitable means such as staking or welding. The projections or wires may be formed of a mild steel ma-terial such as the welding stud 10 itself or medium carbon or stainless steel.
The length of the projections 19 depends upon the configuration and general weld area of the end ofthe stud tobeweldecl. In smaller cliameter or cross sectional area studs, a projection of approximately 1/16 inch or greater is acceptable. In studs of larger cross sectional area, the leng-th of the projections 19 will range up to approximately 1/2 inch. The cross sectional configuration of the projection 19 may be of any desired configuration such as circular or rectangular~ By way of example, the cross sectional configur-ation of a rectangular projection may be in the area of 3/16 inch square down to the range of approximately 1/16 inch square or the equivalent cross sectional area in a round cross sectional configuration.
The welding gun apparatus including the stud chuck 118~143 and the weld gun footpiece utilized in accordance with the ¦ present invention are shown in Figures 3 and 4 of the drawing.
The welding gun 20 utilized may be generally of -the hand held type utilized for welding of conventional shear connectors.
Such a welding gun includes two legs ~1 extending from the welding gu~ and which provide the support for a footpiece 22.
The footpiece 22 provides the support for two arc shields 23. The arc shields 23 have an internal configuration complementary to the configuration of the stud 10 to be welded.
In the embodiment shown, the arc shields 23 are of a rectangular configuration.
The arc shields 23 are designed to fit into receptacles 24 in the footpiece 22 in the manner shown in Figure 4 of the drawing. A relieved.section 25 on the arc shields permits the upper portion 26 of the arc shield to fit into the receptacles 24 of the footpiece 22 with the lower portion of the arc shields projecting underneath the footpiece 22. In this manner, when the footpiece is placed in welding position, the arc shields are held in place between the footpiece and the workpiece as essentially shown in Figure 4 of the drawing.
The welding gun chuck 27 of the apparatus of the present invention inclù~es a backing plate 31 which is secured at it5 upper central portion to the gun extension rod 28 by means of a conventional threaded arrangement. The i~side configuration of the backing plate 31 is of a configuration complementary to the outside configuration of the upper portion of stud 10 to be utilized with the chuck.
Two chuc}c jaws 29 are disposed on either side of the backing plate 31. Either or both of the chuck jaws may be secured to the backing pla-te 31 by means of yieldable threaded fastener-spring arrangements 32. The width of the.backing plate ~_ ~ ~_ ~1871~3 31 is slightly less than the width of the stud 10 to be utilized in -the chuck. ~he yieldable spring--threaded fastener arrange-ments 32 thus provide the yield of the chuck jaws 29 to permit snug fi-t of the stud 10 within the backing plate and chuck jaws when placed in welding positlon.
The stud 10 is loadecl into the chuck assembly 27 upwardly thro~lgh the opening in the footpiece and into the chuck assembly. The complementary configuration of the inner surface of the bac!cing pla-te 31 will permit proper alignment of the stud within the chuck and in respeck to the weld base upon which the stud is to be we~ded in all cases where the s-tud 10 is not of a complete circular configuration. In the particular embodi-b,~/y ~r men-t shown, the~upper portion 18 of the stud 10 is of a parabolic configuration which provides for ready orientation of the stud ends 14 and-15 and projections 19 perpendicular to the weld base and the extremities of the projections 19 being dis-posed in a plane parallel to the weld base.
An alignment pin 33 may also be used to insure proper alignment of the stud 10 with respec-t -to the wor]cpiece. The alignment pin 33 is secured at its one end axlally to the extension rod 2~. The alignment pin 33 extends downwardly below the backing plate 31 and is adapted to cooperate with an align-ment aperature 34 formed into the stud 10 as shown in Figures 2 and 30 The length of the alignment pin 33 is such that the lower end of the alignment pin 33 will mate with the aperture 34 in the stud as the stud is being inser-ted upwardly through -the footpiece in-to the chuck 27.
Prior to welding, the stud 10 is inserted through the footpiece into tne chuck 27. The arc shields 23 are positioned in place within the footpiece and the entire assembly is then placed in position for welding as shown in Figure 4 of the drawin ¦.
~ _ -_v ~ ~_ ~ L87~3 .' In one embodiment, the stud welding gun 20 includes a lift solenoid which will retract the extension rod 28 to position the stud projection above the workpiece~ The lif-t mechanism of the gun is also designed such that the extension rod is biased toward the wor]cpiece. An extension rod locking mechanism is also provided which is capable of locking the extension rod at any position uvon application of a control signal to the locking mechanism, i.e. when the projections come into contact with the workpiece.
The stud wel~ing gun may also include an extension rod damper which is variable in nature and may be adjusted to control the rate of plunge between 1/4 to 3 inches per second.
The extension rod biasing means may be of different spring rates. In one embodiment, the spring pressure is approximately 40 pounds upon the chuck.
The stud welding gun of the present invention, depending upon the embodiments utilized, permits four different welding methods.
The first welding method utilizes the lift solenoid and the biasing spring of 40 pounds pressure. The stud is retracted, stud energized and stud plunged. Upon the stud tips contacting the workpiece, arc inltiation occurs. The extension rod biasing means urges the stud toward the workpiece until contact of the stud ends and workpiece extinguish the arcs.
In the second method, the extension rod locking mechanism is included along with the lift solenoid. When the energized stud tips contact the workpiece, this is sensed and the locking mechanism energized for a time suitable to provide adequate melting of the stud and workpiece. Thereafter, the extension rod biasirlg means plunges the stud in-to the molten pool completing the weld.
~_ . . ~
In the third method, the gun lift solenoid is not used but the gun includes the extension rod damper, and extension rod biasing means. The stud tips are engaged with the workpiece and the stud energized to initiate arcing.
The s-tud is advanced toward the workpiece at a controlled rate under control of the extension rod damper until contact between the stud and workpiece extinguishing the arcs.
In the fourth method, the extension rod biasing means and extension rod locking means are used without the lift solenoid. The stud tips are engaged with the workpiece and the stud locking mechanism engaged. After the stud is energized, the locking mechanism holds the stud immobile for a predetermined time after which the stud is plunged into the molten pool extinguishing the arcs.
The current density drawn from the welding power supply is selected for the particular projection configuration and method being utilized to permit the current density in the projections to be sufficiently high to cause disintegration or explosion of the projection in 5 - 10 milliseconds. This current density is significantly higher thanthat experienced in normal drawn arc stud welding which essentially provides only an arc without particular disintegration of the end of the stud being welded. ~lowever, the weld current density is controlled at a level signiEicantly below that of the capacitor discharge welding whic]l essentially causes almost instantaneous destruction of the entire smaller welding tip associated with the conventional capacitor discharge studs.
By way of example, with a stud having an approximate 1/16 by 1/16 inch square projection cross section, the power supply may be set to deliver approximately 3,500 amps. Under this condition, the current density experi-enced in the projection on the ~ 3 stud will be in the order of l,000,000 amps per square inch.
This is approximately l/10 of the current density experienced in a typical capacitor discharge welding cycle but 200 times the current densi-ty experienced in a typical arc stud welding cycle.
The control of the pressure upon the stud, the rate of plunge and the current density must be maintained all in pro-portion and ratio to one another and to the projection configura-tion to provide for arc initiation. ~ll of these factors are matters which can be ascertained for given stud and welding pro-jection configurations.
The welding controller may be calibrated to time-out and discontinue the weldiny current slightly before, at or after the stud ends reach the workpiece. In a preferred embodiment, the weld current is maintained on after the stud reaches the workpiece for a slight duration of time, which procedure is known as a hot plunge.
The welding time between the moment of contact of the projections o the stud and the discontinuance of welding current depends upon the length and cross sectional area of the projec-tions as well as the current setting. By way of example, a pro-jection of l/~ inch in length and of approximately l/16 inch square configuration results in a welding c~cle time of between .2 to .3 seconds. When a l/2 inch length projection is utilized Wit}l a l/16 inch square cross sectional projection, the welding cycle is from approximately .4 to .6 of a second. sy way of comparison, the welding cycle time of conventional~capacitor dis-charge welding is .002 to .004 seconds while conventional arc stud welding is .100 seconds or greater.
In a preferred embodiment, a positive ground connection to the workpiece is preferred. Under these circumstances as above descrihed, it is found that the base metal contributes to r~ ~
.. . . . . ~
11617~L43 .' a major portion of the weld joint with a lesser portion of the weld fillet material being formed Erom the stud.
From the foregoing description of a preferred embodi-ment of the double ended stud welding stud, apparatus and methods in accordance with the present invention, it will be appreciated that the apparatus and method as well as the s-tud described provide an effective and reliable method for effecting simul-taneous welding of a stud having two or more weld ends by the stud end welding technique. The description of specific embodi-ments and parameters has been made by way of illustration and not by way of limitation and the scope of the invention is to be interpreted in view of the following claims.
What is claimed is:
...
I -18~
r !_ ~
~~
In use, -the stud 10 is welded to thc I-beam 11 directly upon the I-beam or, in some instances, through decking 12 which is utili~ed as the bottom form member and protection for a concrete slab to ultimately be poured upon and supported by the I-beam 11.
A shear connector 10, welded in place, is shown partially embedded in a slab of concrete 13 as it would appear in actual use. The shear connec-tor 10 provides an interconnection between the I-beam 11 and the slab 13 to resist shearing action of the concrete slab 13 in respect to the supporting beam 11 in a heretofore known manner.
The details of the shear connector design of double ended stud of the present invention is shown in Figure 2 of the drawing. The shear comlector stud 10 includes two welcl ends 14 and 15. The ends 14 and 15 oE the stud are disposed in a common p]ane.
A pair of stud legs or portions 16 and 17 of the stud adjacent each end 14 and 15 thereof are formed straight. This straight leg or portion is disposed generally perpendicular to the weld base UpOII which the stud is to be welded and is necessary for cooperation with the configuration of the arc shields which are used in the process and which will be described hereinafter.
The remainder of the stud 10 includes a stud body 18 disposed between the legs 16 and 17 which may be of differing configurations from flat to U-shaped. In a preferred embodiment, the stud body is of a parabolic configuration.
The parabolic configuration of the remaining portion or body 18 of the stud provides for ready orientation of the stud in a stud welding chuck due to the noncircular configuration of the parabolic curve. Additionally, the parabolic configuration is of a shorter profile than a circular configur-ation and results in a material savings of approximately 17% to 25% over a circular configuration of -the same height without distracting from the shear strength capabilities of the stud.
The cross section of the stud 10 may be of any desired configur-ation, i.e. round,eliptical or rectangular. In a preferred embodiment, the stud is of rectangular configuration as shown in ~igures 1 and 2 of the drawing.
The weld ends 14 and 15 of the stud 10 are provided with elongate relatively thin projections or wires 19 extending parallel to the longitud-inal axis of the legs and Perpendicularly from the weld face of the weld ends 14 and 15 and thus, extend perpendicular to the weld base upon which the stud is to be welded. The projections or wires 19 may be formed of the parent metal of the stud during manufacture of the stud.
Alternately, the projections or wires may be affixed to the stud by any suitable means such as staking or welding. The projections or wires may be formed of a mild steel ma-terial such as the welding stud 10 itself or medium carbon or stainless steel.
The length of the projections 19 depends upon the configuration and general weld area of the end ofthe stud tobeweldecl. In smaller cliameter or cross sectional area studs, a projection of approximately 1/16 inch or greater is acceptable. In studs of larger cross sectional area, the leng-th of the projections 19 will range up to approximately 1/2 inch. The cross sectional configuration of the projection 19 may be of any desired configuration such as circular or rectangular~ By way of example, the cross sectional configur-ation of a rectangular projection may be in the area of 3/16 inch square down to the range of approximately 1/16 inch square or the equivalent cross sectional area in a round cross sectional configuration.
The welding gun apparatus including the stud chuck 118~143 and the weld gun footpiece utilized in accordance with the ¦ present invention are shown in Figures 3 and 4 of the drawing.
The welding gun 20 utilized may be generally of -the hand held type utilized for welding of conventional shear connectors.
Such a welding gun includes two legs ~1 extending from the welding gu~ and which provide the support for a footpiece 22.
The footpiece 22 provides the support for two arc shields 23. The arc shields 23 have an internal configuration complementary to the configuration of the stud 10 to be welded.
In the embodiment shown, the arc shields 23 are of a rectangular configuration.
The arc shields 23 are designed to fit into receptacles 24 in the footpiece 22 in the manner shown in Figure 4 of the drawing. A relieved.section 25 on the arc shields permits the upper portion 26 of the arc shield to fit into the receptacles 24 of the footpiece 22 with the lower portion of the arc shields projecting underneath the footpiece 22. In this manner, when the footpiece is placed in welding position, the arc shields are held in place between the footpiece and the workpiece as essentially shown in Figure 4 of the drawing.
The welding gun chuck 27 of the apparatus of the present invention inclù~es a backing plate 31 which is secured at it5 upper central portion to the gun extension rod 28 by means of a conventional threaded arrangement. The i~side configuration of the backing plate 31 is of a configuration complementary to the outside configuration of the upper portion of stud 10 to be utilized with the chuck.
Two chuc}c jaws 29 are disposed on either side of the backing plate 31. Either or both of the chuck jaws may be secured to the backing pla-te 31 by means of yieldable threaded fastener-spring arrangements 32. The width of the.backing plate ~_ ~ ~_ ~1871~3 31 is slightly less than the width of the stud 10 to be utilized in -the chuck. ~he yieldable spring--threaded fastener arrange-ments 32 thus provide the yield of the chuck jaws 29 to permit snug fi-t of the stud 10 within the backing plate and chuck jaws when placed in welding positlon.
The stud 10 is loadecl into the chuck assembly 27 upwardly thro~lgh the opening in the footpiece and into the chuck assembly. The complementary configuration of the inner surface of the bac!cing pla-te 31 will permit proper alignment of the stud within the chuck and in respeck to the weld base upon which the stud is to be we~ded in all cases where the s-tud 10 is not of a complete circular configuration. In the particular embodi-b,~/y ~r men-t shown, the~upper portion 18 of the stud 10 is of a parabolic configuration which provides for ready orientation of the stud ends 14 and-15 and projections 19 perpendicular to the weld base and the extremities of the projections 19 being dis-posed in a plane parallel to the weld base.
An alignment pin 33 may also be used to insure proper alignment of the stud 10 with respec-t -to the wor]cpiece. The alignment pin 33 is secured at its one end axlally to the extension rod 2~. The alignment pin 33 extends downwardly below the backing plate 31 and is adapted to cooperate with an align-ment aperature 34 formed into the stud 10 as shown in Figures 2 and 30 The length of the alignment pin 33 is such that the lower end of the alignment pin 33 will mate with the aperture 34 in the stud as the stud is being inser-ted upwardly through -the footpiece in-to the chuck 27.
Prior to welding, the stud 10 is inserted through the footpiece into tne chuck 27. The arc shields 23 are positioned in place within the footpiece and the entire assembly is then placed in position for welding as shown in Figure 4 of the drawin ¦.
~ _ -_v ~ ~_ ~ L87~3 .' In one embodiment, the stud welding gun 20 includes a lift solenoid which will retract the extension rod 28 to position the stud projection above the workpiece~ The lif-t mechanism of the gun is also designed such that the extension rod is biased toward the wor]cpiece. An extension rod locking mechanism is also provided which is capable of locking the extension rod at any position uvon application of a control signal to the locking mechanism, i.e. when the projections come into contact with the workpiece.
The stud wel~ing gun may also include an extension rod damper which is variable in nature and may be adjusted to control the rate of plunge between 1/4 to 3 inches per second.
The extension rod biasing means may be of different spring rates. In one embodiment, the spring pressure is approximately 40 pounds upon the chuck.
The stud welding gun of the present invention, depending upon the embodiments utilized, permits four different welding methods.
The first welding method utilizes the lift solenoid and the biasing spring of 40 pounds pressure. The stud is retracted, stud energized and stud plunged. Upon the stud tips contacting the workpiece, arc inltiation occurs. The extension rod biasing means urges the stud toward the workpiece until contact of the stud ends and workpiece extinguish the arcs.
In the second method, the extension rod locking mechanism is included along with the lift solenoid. When the energized stud tips contact the workpiece, this is sensed and the locking mechanism energized for a time suitable to provide adequate melting of the stud and workpiece. Thereafter, the extension rod biasirlg means plunges the stud in-to the molten pool completing the weld.
~_ . . ~
In the third method, the gun lift solenoid is not used but the gun includes the extension rod damper, and extension rod biasing means. The stud tips are engaged with the workpiece and the stud energized to initiate arcing.
The s-tud is advanced toward the workpiece at a controlled rate under control of the extension rod damper until contact between the stud and workpiece extinguishing the arcs.
In the fourth method, the extension rod biasing means and extension rod locking means are used without the lift solenoid. The stud tips are engaged with the workpiece and the stud locking mechanism engaged. After the stud is energized, the locking mechanism holds the stud immobile for a predetermined time after which the stud is plunged into the molten pool extinguishing the arcs.
The current density drawn from the welding power supply is selected for the particular projection configuration and method being utilized to permit the current density in the projections to be sufficiently high to cause disintegration or explosion of the projection in 5 - 10 milliseconds. This current density is significantly higher thanthat experienced in normal drawn arc stud welding which essentially provides only an arc without particular disintegration of the end of the stud being welded. ~lowever, the weld current density is controlled at a level signiEicantly below that of the capacitor discharge welding whic]l essentially causes almost instantaneous destruction of the entire smaller welding tip associated with the conventional capacitor discharge studs.
By way of example, with a stud having an approximate 1/16 by 1/16 inch square projection cross section, the power supply may be set to deliver approximately 3,500 amps. Under this condition, the current density experi-enced in the projection on the ~ 3 stud will be in the order of l,000,000 amps per square inch.
This is approximately l/10 of the current density experienced in a typical capacitor discharge welding cycle but 200 times the current densi-ty experienced in a typical arc stud welding cycle.
The control of the pressure upon the stud, the rate of plunge and the current density must be maintained all in pro-portion and ratio to one another and to the projection configura-tion to provide for arc initiation. ~ll of these factors are matters which can be ascertained for given stud and welding pro-jection configurations.
The welding controller may be calibrated to time-out and discontinue the weldiny current slightly before, at or after the stud ends reach the workpiece. In a preferred embodiment, the weld current is maintained on after the stud reaches the workpiece for a slight duration of time, which procedure is known as a hot plunge.
The welding time between the moment of contact of the projections o the stud and the discontinuance of welding current depends upon the length and cross sectional area of the projec-tions as well as the current setting. By way of example, a pro-jection of l/~ inch in length and of approximately l/16 inch square configuration results in a welding c~cle time of between .2 to .3 seconds. When a l/2 inch length projection is utilized Wit}l a l/16 inch square cross sectional projection, the welding cycle is from approximately .4 to .6 of a second. sy way of comparison, the welding cycle time of conventional~capacitor dis-charge welding is .002 to .004 seconds while conventional arc stud welding is .100 seconds or greater.
In a preferred embodiment, a positive ground connection to the workpiece is preferred. Under these circumstances as above descrihed, it is found that the base metal contributes to r~ ~
.. . . . . ~
11617~L43 .' a major portion of the weld joint with a lesser portion of the weld fillet material being formed Erom the stud.
From the foregoing description of a preferred embodi-ment of the double ended stud welding stud, apparatus and methods in accordance with the present invention, it will be appreciated that the apparatus and method as well as the s-tud described provide an effective and reliable method for effecting simul-taneous welding of a stud having two or more weld ends by the stud end welding technique. The description of specific embodi-ments and parameters has been made by way of illustration and not by way of limitation and the scope of the invention is to be interpreted in view of the following claims.
What is claimed is:
...
I -18~
r !_ ~
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. The method of simultaneously stud welding the ends of a multi-ended metallic stud to a metallic base member comprising the steps of:
providing on each end of the stud at least one elongate relatively thin metallic extending projection;
applying a controlled pressure upon the stud in the direction of the base member;
applying an electrical potential to the stud from a continuous current power supply;
bringing the metallic projections into contact with the metallic base member; and controlling the pressure on and the rate of advance of the stud toward the workpiece and controlling the electrical potential upon the stud all in proportion to one another and to the configuration of the projections and stud ends to (1) pro-vide a current density in the projections to essentially immedi-ately and simultaneously disintegrate the projections to esta-blish arc initiation at all ends of the metallic stud and (2) thereafter maintain a continuous arc at all ends of the metallic stud of duration and current density at least equaling that of drawn arc stud welding to maintain molten metal at each end thereof until the ends of the stud come into contact with the base material.
providing on each end of the stud at least one elongate relatively thin metallic extending projection;
applying a controlled pressure upon the stud in the direction of the base member;
applying an electrical potential to the stud from a continuous current power supply;
bringing the metallic projections into contact with the metallic base member; and controlling the pressure on and the rate of advance of the stud toward the workpiece and controlling the electrical potential upon the stud all in proportion to one another and to the configuration of the projections and stud ends to (1) pro-vide a current density in the projections to essentially immedi-ately and simultaneously disintegrate the projections to esta-blish arc initiation at all ends of the metallic stud and (2) thereafter maintain a continuous arc at all ends of the metallic stud of duration and current density at least equaling that of drawn arc stud welding to maintain molten metal at each end thereof until the ends of the stud come into contact with the base material.
2. The method of claim 1 further including the steps of:
positioning the stud and projections in contact with the base material at the initiation of the stud welding cycle and holding the stud at that position for a predetermined time then plunging the stud under control into the resultant molten pools.
positioning the stud and projections in contact with the base material at the initiation of the stud welding cycle and holding the stud at that position for a predetermined time then plunging the stud under control into the resultant molten pools.
3. The method in claim 1 further including the steps of positioning the stud and projections in contact with the base material at the initiation of the stud welding cycle and allow-ing the stud to arc during the controlled plunge time into the resultant molten pools.
4. The method in claim 1 including the steps of positioning the stud and projections out of contact with the base material at the initiation of the stud welding cycle and energizing the stud prior to contact with the base material.
5. The method of claim 1 further including the step of:
maintaining the stud energized through contact of the stud end with the base material.
maintaining the stud energized through contact of the stud end with the base material.
6. The method of claim 1 wherein the current density in the projections is approximately 200 times the typical drawn arc stud welding current density and 1/10 the typical capacitor discharge stud welding current density.
7. The method according to claim 1 in which the current density in the projections is in the order of one million amperes per square inch.
8. The method of claim 1 further including the steps of positioning the stud and projections out of contact with the base material and energizing the stud prior to contact with the base material and, upon contact of the projections with the base material, locking the stud against further descent toward the base material for a predetermined time and then permitting the stud to continue its descent into contact with the base material.
9. The method of claim 1 wherein the rate of descent of the stud toward the workpiece during the welding cycle is maintained within the range of approximately 1/4 inch per second to 3 inches per second.
10. The method of claim 1 wherein the amperage in the stud projections is of such density to disintegrate the projections in the range of 0.005 to 0.010 seconds and the remaining weld-ing cycle time is within the range of 0.200 to 0.600 seconds.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US265,239 | 1981-05-19 | ||
| US06/265,239 US4439661A (en) | 1979-11-19 | 1981-05-19 | Apparatus and method for double end stud welding |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1187143A true CA1187143A (en) | 1985-05-14 |
Family
ID=23009610
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000403187A Expired CA1187143A (en) | 1981-05-19 | 1982-05-18 | Method for double end stud welding |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0081559A1 (en) |
| CA (1) | CA1187143A (en) |
| WO (1) | WO1982003999A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0360910A1 (en) * | 1988-09-30 | 1990-04-04 | Siemens Aktiengesellschaft | Motor mounting |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2349547A (en) * | 1941-07-24 | 1944-05-23 | Gisondi Emanuel | Fastening device |
| CH230091A (en) * | 1942-06-11 | 1943-12-15 | Marquardt Alwin | Wire clips for staplers. |
| US2553499A (en) * | 1950-01-17 | 1951-05-15 | Graham Mfg Corp | Welding method |
| US2788434A (en) * | 1954-01-29 | 1957-04-09 | Gregory Ind Inc | Welding stud assembly |
| US4339653A (en) * | 1979-11-19 | 1982-07-13 | Omark Industries, Inc. | Method for double end stud welding |
-
1982
- 1982-05-18 CA CA000403187A patent/CA1187143A/en not_active Expired
- 1982-05-19 WO PCT/US1982/000684 patent/WO1982003999A1/en unknown
- 1982-05-19 EP EP19820902040 patent/EP0081559A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| WO1982003999A1 (en) | 1982-11-25 |
| EP0081559A1 (en) | 1983-06-22 |
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