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The Ohio Nut and Bolt Company33 Lou Groza Blvd. — Berea, Ohio 44017
Ohio Electrode Information ....................................... 12 – 14
HIWeld Data Guide
For Engineering Fastener Foundations
Weld D
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2001 Ohio Catalog Index.p65 8/31/01, 2:06 PM11
WeldData Guide
OHIOBasic Recommendations
The three basic requirements forproducing a good resistance weld involveheat, time and pressure. The properrelationship and control of each of theseelements will contribute to an optimumweld.
HeatHeat balance is extremely important togood welds. Proper heat balance isattained when the fastener and the part towhich it is being welded, are brought tothe welding temperature at the same time.Heat or current balance occurs when thedistribution of heat between the fastenerand the component part is equal.
Some variables which affect the heat:
1. The weld time is too long.2. The welding current is too high.3. Low electrode pressure.4. The electrode diameter is too small.5. Improper electrode alignment.6. Improper adjustments in changing
metal thickness.7. Unclean sheet or component part.
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Adjusting the heat or current with aregulator changes the ratio of primary tosecondary voltage. Most Ohio Weldproducts require from 5,000 to 20,000secondary amperes to produce enoughheat to make the weld. Set the heatregulator at a point where current will notcause flashing or sparking when the weldoccurs. A current meter will determineaccurate short circuit secondary amperereadings. This is an accurate method fordetermining correct current settings.
TimeTime, expressed in cycles, is animportant factor enabling a good weld.One cycle represents 1/60 of a second.The weld time should be as short aspossible and the weld should occur inone hit. Repeated hits add nothing to thestrength or appearance of the weld andmay damage the work. An average weldtakes from three to fifteen cycles. Thereare three groups of time in resistancewelding and they are all important.
Squeeze Time:The interval between the application ofpressure and the application of weldingcurrent.
Weld Time:The time which the current flows throughthe work during the weld process.
Hold Time:The time that pressure remains on theelectrodes after the end of the weldingcurrent.
PressurePressure plays a key part in obtainingoptimum welds. Pressure assures goodelectrical contact of the welded part ofthe sheet. In projection welding, pressurealso forces the projection into the sheetafter the metal reaches fusiontemperature. Extreme pressure willcause projections to flatten out beforereaching weld heat. Not enough pressurecauses flashing, spitting, burning anddiscoloration.
All standard OHIO Weld Products,except those with ring projections,require from 300 to 1,200 poundspressure at the electrodes. A force gaugechecks the pressure at the electrodes.
The selection of the proper type and sizeof welder depends on the work thewelder is to perform. OHIO WeldFasteners can be welded with the
Standard Press TypeWelding Machine
— Hydraulic or AirCylinder
Figure 1
Pressure GaugeFlexibleBands
Knee
Water Line
Heat Regulator
Electrodes
Foot Switch
— Throat —
Water Supply
simplest type of press or rocker-armwelder. Production requirements may callfor large automated machines. KVA(Kilovolt Amperes) determines weldersize. Many OHIO Projection WeldScrews weld with press welders as smallas 20 KVA, while others will require unitsas large as 200 KVA. For typical weldsetups, consult the weld setting tables onpages 4 - 11 in this section.
Projection welding uses a press welder(figure 1) because the air cylinder isdirectly over the electrodes and the travelis in a straight line. In addition, goodalignment and equalized pressure isachieved at the tips.
Spot welding uses rocker-arm welders.Air cylinders, a motor and cam or foottreadle supply electrode force (figure 2).Machines are available from 10 KVA to75 KVA or greater.
Standard Rocker–ArmSpot Welding Machine
Figure 2
Pressure Gauge
Heat Regulator
Electrodes
— Throat —
Foot Switch
Rocker ArmWater Lines
Water Supply
When welding OHIO Spot WeldFasteners, manufacturing can use thesame equipment, electrodes, and settingsused in regular production welding. OHIOSpot Weld Screws and Nuts are weldedwith welders which range in size from 30KVA to 75 KVA. For typical weld setups,consult the weld setting tables on pages 4- 11 in this section.
pany
WeldData Guide
OHIOProjection Welding
Projection weldingutilizes relatively largeelectrodes to insurecoverage of the entireprojection area. Themore bearing surface,the longer the electrodelife (figure 3).Electrodes should belocated directly on thecenter line of pressure
application to insure accurate alignmentand good contact for quality welds.
In projection welding, heat is localized inthe weld projections of the fastener. OnOHIO parts, these carefully locatedprojections cause the current to beconcentrated in small areas as it flowsbetween the fastener and the parent part.Welding occurs as the projections fusewith the surface of the part.
The face of the electrode should be ofsufficient diameter to completely coverthe surface of the part being welded. The
Figure 3
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more bearing surfacethat can be obtained, thegreater the electrode life.There are many suitablecopper alloys availablefor projection welding;however, it is best touse a material with aminimum Rockwell B 75and with as high anelectrical conductivity aspossible. Electrode lifecan be lengthened in high production bybrazing a pad of RWMA Class 12 copperalloy approximately 1/4” thick to thesurface of the regular electrode material.For details about the Ohio Electrodesavailable, see page 12 of this section.
Electrodes ForProjection Welding
To insure accurate alignment for goodcontact and quality welds, electrodes forprojection welding should be locateddirectly on the center line of pressure
application. In addition to producingfaulty welds, misaligned electrodes canresult in damage to the electrode face(figure 4). Another major contribution toa bad weld is nonparallel electrode faces.They cause unbalanced pressure onelectrodes which results in expulsion ofweld metal during theweld cycle. Thisdamages threads andcan burn electrodeinsulation when weldingscrews through theparent metal. Inaddition, nonparallelfaces cause weld nuts toskid against parent metalduring weld, resulting ina burned pilot withdistorted threads andpossible misalignment with mating parts(figure 5).
Figure 5
Figure 6
The spot welding principle involvesplacing the two pieces to be weldedbetween two copper or copper alloywelding tips. An electric current ofsufficient strength is passed through theentire area under the electrode tip,welding the pieces together (figure 6).This differs from projection welding inthat the heat concentration depends onthe size and shape of the electrode tiprather than on the size, shape and the
number of projections used.
Because the size and shapeof the electrode tip directlyaffect the size of the weld, italso determines the strength
of the weld in shear.Thus, control weldsize and strength bymaintaining a uniformtip contact area. Tipdiameters must bechanged for each
thickness of metal to be welded. Seeweld settings tables on pages 4 – 11 inthis section for recommended sizes forOHIO Fasteners.
In spot welding, indentations anddiscolorations appear in the weld area.This is caused by metal being drawn upto form the weld nugget or growthbetween the fastener and the part. It ispossible to reduce this indentation (anddiscoloration) by using a flat electrode onthe side where minimization of thesemarks is desired.
An important advantage of spot weldingis it can be utilized to attach fastenerswhere the assembly itself is beingwelded. This eliminates extra setup timeand adds to the flexibility of the basicwelding equipment.
Faulty welds can be eliminated orminimized by avoiding some of the easilyoverlooked pitfalls in resistance welding.
Figure 7
Some of the basicrequirements are thatthe material to bewelded is of goodwelding quality and isfree of oil, dirt andforeign matter of allkinds.
Spot welding electrodesmust be kept dressed toproper size.Mushroomed tips(figure 7) prevent necessary localizing ofheat for proper welding. Projectionwelding electrodes must be kept alignedfor optimum and uniform pressure.
On through the hole applications, allowsufficient clearance between part andparent material to prevent shunting ofcurrent into material. When using jigs,fixtures and stops for locating devicesare insulated form the electrode body.
pany6
WeldData Guide
OHIO
In spot welding, the heat concentrationdepends on the size and shape or theelectrode tips. The weld is made bypassing current through the entire area
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Figure 9F igure 8
Electrodes For Spot Weldingunder the electrode tip. The smallerelectrode tip diameters erode ormushroom much faster than projectionweld electrodes. They must be dressed
regularly to maintain proper contact(figure 6). Follow the recommendationson pages 5 – 12 in this section.
Faulty welds can be traced to a variety offactors such as the weld setup,electrodes, the control system, theselection of fasteners, the machine, theoperator or the process itself. Thefollowing check list can be helpful inisolating trouble areas
1. The weld setup; incorrect heat,time or pressure.
2. The electrodes (faulty design, lackof insulation, need for dressing).
3. The welding machine (mechanical,electrical, water or airinadequacies).
4. The electronic controls tubefailures, etc.
5. The parts being welded (poordesign, wrong material andprojection design or location).
6. The metal to which the parts arewelded (Is it good welding quality?).
7. Jigs, fixtures and the feedingdevices (are they effective?).
8. The operator (the human element).
Most welding difficulties are caused bytwo of these elements - poor electrodedesigns and improper weld setup.Figures 8, 9, and 10 illustrate the resultsof welds made with improper electrodes.Figures 8 and 9 also show indentationsmade by electrodes which did not coverthe entire head of the weld screw, whichis mandatory in projection welding.
Since the projections are fairly close tothe perimeter of the screw head, both ofthese welds failed to fuse all of theprojections resulting in weak welds. Infigure 10, you can see the weld spatterin the screw threads caused by poor orcomplete lack of insulation. Wheneverthe screw or nut is welded through a holein a sheet, the lower electrode must beinsulated.
Figures 11 and 12 show the results ofimproper weld setups. In figure 11 thereis expulsion at the projections and agreat deal or discoloration, both usuallycaused by inadequate electrode pressureor excessive current. In figure 12, theoperator attempted to offset the lack ofpressure by increasing the heat. You cansee the expulsion and discoloration hasincreased. In addition, the area aroundthe weld has been made over heated,weakening the sheet at the weld point.
Maintenance TipsMaintain a standby supply of electrodesat the welder to minimize downtime dueto electrode change.
— Do —Projection Weld Electrodes
Dress electrodes periodically on a lathe.Use a RWMA, Group A, Class 3 copperon the sheet side.
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— Do —Spot Weld Electrodes
Dress electrodes periodically on a lathewith an approved tip dresser.Change tip diameters to adjust to eachthickness of metal to be welded.
— Don’t —Use a file to dress electrodesStore electrodes where face damagecan result.Use a pipe wrench to remove theelectrodes.
G e n e r a l T i p s1. To assure perfect alignment, both
the faces and the axis of theelectrodes must be parallel. Tocheck this insert a piece of carbonpaper and a sheet of white paperbetween the electrodes and applypressure with the weld cycles turnedoff. The resulting impression on theplain paper will indicate thealignment of the electrodes.
2. Utilize a water jacket wheneverpossible and locate it as close aspossible to the welding surface.
3. Keep material to be welded free formoil, dirt and other foreign matter.
4. Follow welder size and settingrecommendations made byThe Ohio Nut and BoltCompany
pany
Figure 12ure 11
WeldData Guide
The Ohio Nut and Bolt Company33 Lou Groza Blvd. • Berea, Ohio 44017
OHIO Low CarbonThese are typical weld setups for use with C 1010 LowCarbon cold rolled sheets in a thickness range from .025to .187. Material to be welded should be free from oil,dirt or rust. Specific weld setups for other thicknessesand materials are available upon request.
OHIO Low CarbonThese are typical weld setups for use with C 1010 LowCarbon cold rolled sheets in a thickness range from .025to .187. Material to be welded should be free from oil,dirt or rust. Specific weld setups for other thicknessesand materials are available upon request.
Low CarbonThese are typical weld setups for use with C 1010 LowCarbon cold rolled sheets in a thickness range from .025to .187. Material to be welded should be free from oil,dirt or rust. Specific weld setups for other thicknessesand materials are available upon request.
WeldData Guide
The Ohio Nut and Bolt Company33 Lou Groza Blvd. • Berea, Ohio 44017
Low CarbonThese are typical weld setups for use with C 1010 LowCarbon cold rolled sheets in a thickness range from .025to .187. Material to be welded should be free from oil,dirt or rust. Specific weld setups for other thicknessesand materials are available upon request.
WeldData Guide
The Ohio Nut and Bolt Company33 Lou Groza Blvd. • Berea, Ohio 44017
Low CarbonThese are typical weld setups for use with C 1010 LowCarbon cold rolled sheets in a thickness range from .025to .187. Material to be welded should be free from oil,dirt or rust. Specific weld setups for other thicknessesand materials are available upon request.
Stainless SteelThese are typical weld setups for use with 18-8 stainless steel sheets in thickness range as indicated. Material to be welded should be free fromoil, dirt or film. Welding of stainless steel usually requires a shorter weld time with higher pressure and higher secondary volts than whenwelding low carbon steel. Modern controls are helpful in attaining good results when welding stainless steel.
WeldData Guide
The Ohio Nut and Bolt Company33 Lou Groza Blvd. • Berea, Ohio 44017
OHIO Stainless SteelThese are typical weld setups for use with 18-8 stainlesssteel sheets in thickness range as indicated. Material to bewelded should be free from oil, dirt or film. Welding ofstainless steel usually requires a shorter weld time withhigher pressure and higher secondary volts than whenwelding low carbon steel. Modern controls are helpful inattaining good results when welding stainless steel.
OHIO Stainless SteelThese are typical weld setups for use with 18-8 stainlesssteel sheets in thickness range as indicated. Material to bewelded should be free from oil, dirt or film. Welding ofstainless steel usually requires a shorter weld time withhigher pressure and higher secondary volts than whenwelding low carbon steel. Modern controls are helpful inattaining good results when welding stainless steel.
OHIO Stainless SteelThese are typical weld setups for use with 18-8 stainlesssteel sheets in thickness range as indicated. Material to bewelded should be free from oil, dirt or film. Welding ofstainless steel usually requires a shorter weld time withhigher pressure and higher secondary volts than whenwelding low carbon steel. Modern controls are helpful inattaining good results when welding stainless steel.