Copper Welding With Industrial Robots

Nov 1, 2017

Industrial robots can accomplish a wide range of welding materials such as copper and copper alloys. These make unique combination for any manufacturing environments because of their electrical and thermal conductivity, outstanding resistance to corrosion, ease of fabrication, good strength, and fatigue resistance. If you are interested in integrating a welding solution on your production line, contact the experts at today.

Welding copper with robots

Cop­per and cop­per alloys offer a unique com­bi­na­tion of mate­r­i­al prop­er­ties that make them ide­al for many man­u­fac­tur­ing envi­ron­ments. They are wide­ly used because of their excel­lent elec­tri­cal and ther­mal con­duc­tiv­i­ties, out­stand­ing resis­tance to cor­ro­sion, ease of fab­ri­ca­tion, good strength and fatigue resis­tance. Oth­er use­ful char­ac­ter­is­tics include spark resis­tance, met­al-to-met­al wear resis­tance, low-per­me­abil­i­ty prop­er­ties, and dis­tinc­tive color.

Cop­per Weld­ing Processes

Cop­per is often joined by weld­ing. The arc weld­ing process­es are of pri­ma­ry con­cern. Arc weld­ing can be per­formed using shield­ed met­al arc weld­ing (SMAW), gas-tung­sten arc weld­ing (GTAW), gas-met­al arc weld­ing (GMAW), plas­ma arc weld­ing (PAW), and sub­merged arc weld­ing (SAW).

Weld­ing process­es that use gas shield­ing are gen­er­al­ly pre­ferred, although SMAW can be used for many non-crit­i­cal appli­ca­tions. Argon, heli­um, or mix­tures of the two are used as shield­ing gas­es for GTAW, PAW, and GMAW. Gen­er­al­ly, argon is used when man­u­al­ly weld­ing mate­r­i­al is less than 3 mm thick, has low ther­mal con­duc­tiv­i­ty, or both. Heli­um or a mix­ture of 75% heli­um and 25% argon is rec­om­mend­ed for machine weld­ing of thin sec­tions and for man­u­al weld­ing of thick­er sec­tions of alloys that have high ther­mal con­duc­tiv­i­ty. Small amounts of nitro­gen can be added to the argon shield­ing gas to increase the effec­tive heat input. Shield­ed met­al arc weld­ing can be used to weld a wide range of cop­per alloy thick­ness­es. Cov­ered elec­trodes for sub­merged arc weld­ing (SAW) of cop­per alloys are avail­able in stan­dard sizes rang­ing from 2.4 to 4.8 mm.

Gas-Tung­sten Arc Welding

Gas-tung­sten arc weld­ing is well suit­ed for cop­per and cop­per alloys because of its intense arc, which pro­duces an extreme­ly high tem­per­a­ture at the joint and a nar­row heat-affect­ed zone (HAZ).

In weld­ing cop­per and the more ther­mal­ly con­duc­tive cop­per alloys, the inten­si­ty of the arc is impor­tant in com­plet­ing fusion with min­i­mum heat­ing of the sur­round­ing, high­ly con­duc­tive base met­al. A nar­row HAZ is par­tic­u­lar­ly desir­able in the weld­ing of cop­per alloys that have been pre­cip­i­ta­tion hard­ened.

Many of the stan­dard tung­sten or alloyed tung­sten elec­trodes can be used in GTAW of cop­per and cop­per alloys. The selec­tion fac­tors nor­mal­ly con­sid­ered for tung­sten elec­trodes apply in gen­er­al to the cop­per and cop­per alloys. Except for the spe­cif­ic class­es of cop­per alloys, tho­ri­at­ed tung­sten (usu­al­ly EWTh‑2) is pre­ferred for its bet­ter per­for­mance, longer life, and greater resis­tance to contamination.

Gas-Met­al Arc Welding

Gas-met­al arc weld­ing is used for join­ing cop­per and cop­per alloys for thick­ness less than 3 mm, while GMAW is pre­ferred for sec­tion thick­ness above 3 mm and for join­ing alu­minum bronzes, sil­i­con bronzes and cop­per-nick­el alloys.

Plas­ma Arc Welding

The weld­ing of cop­pers and cop­per alloys using PAW is com­pa­ra­ble to GTAW of these alloys. Argon, heli­um, or mix­tures of the two are used for the weld­ing of all alloys. Hydro­gen gas should nev­er be used when weld­ing coppers.

Plas­ma arc weld­ing has two dis­tinct advan­tages over GTAW

  1. Tung­sten is con­cealed and entire­ly shield­ed, which great­ly reduces con­t­a­m­i­na­tion of the elec­trode, par­tic­u­lar­ly for alloys with low-boil­ing-tem­per­a­ture con­stituents such as brass­es, bronzes, phos­phor bronzes, and alu­minum bronzes.
  2. Con­struct­ed arc plume gives rise to high­er arc ener­gies while min­i­miz­ing the growth of the HAZ. As with GTAW, cur­rent pul­sa­tion and cur­rent ramp­ing may also be used. Plas­ma arc weld­ing equip­ment has been minia­tur­ized for intri­cate work, known as microplas­ma welding.

Plas­ma arc weld­ing of cop­pers and cop­per alloys may be per­formed either auto­ge­nous­ly or with filler met­al. Filler met­al selec­tion is iden­ti­cal to that out­lined for GTAW. Automa­tion and mech­a­niza­tion of this process is read­i­ly per­formed and is prefer­able to GTAW where con­t­a­m­i­na­tion can restrict pro­duc­tion effi­cien­cies. Weld­ing posi­tions for PAW are iden­ti­cal to those for GTAW. How­ev­er, the plas­ma key­hole mode has been eval­u­at­ed for thick­er sec­tions in a ver­ti­cal-up posi­tion. Gen­er­al­ly, all infor­ma­tion pre­sent­ed for GTAW is applic­a­ble to PAW.

Sub­merged Arc Welding 

The weld­ing of thick gage mate­r­i­al, such as pipe formed from heavy plate, can be achieved by con­tin­u­ous met­al-arc oper­a­tion under a gran­u­lar flux. Effec­tive de-oxi­da­tion and slag-met­al reac­tions to form the required weld-met­al com­po­si­tion are crit­i­cal and the SAW process is still under devel­op­ment for cop­per-base mate­ri­als. A vari­a­tion on this process can be used for weld cladding or hard­fac­ing. Com­mer­cial­ly avail­able flux­es should be used for the cop­per-nick­el alloys.

Alloy Met­al­lur­gy and Weldability

Many com­mon met­als are alloyed with cop­per to pro­duce the var­i­ous cop­per alloys. The most com­mon alloy­ing ele­ments are alu­minum, nick­el, sil­i­con, tin, and zinc. Oth­er ele­ments and met­als are alloyed in small quan­ti­ties to improve cer­tain mate­r­i­al char­ac­ter­is­tics, such as cor­ro­sion resis­tance or machinability.

Nine Cop­per and Cop­per Alloy Groups:

  1. Cop­pers, which con­tain a min­i­mum of 99.3% Cu
  2. High-cop­per alloys, which con­tain up to 5% alloy­ing elements
  3. Cop­per-zinc alloys (brass­es), which con­tain up to 40% Zn
  4. Cop­per-tin alloys (phos­phor bronzes), which con­tain up to 10% Sn and 0.2% P
  5. Cop­per-alu­minum alloys (alu­minum bronzes), which con­tain up to 10% Al
  6. Cop­per-sil­i­con alloys (sil­i­con bronzes), which con­tain up to 3% Si
  7. Cop­per-nick­el alloys, which con­tain up to 30% Ni
  8. Cop­per-zinc-nick­el alloys (nick­el sil­vers), which con­tain up to 7% Zn and 18% Ni
  9. Spe­cial alloys, which con­tain alloy­ing ele­ments to enhance a spe­cif­ic prop­er­ty or char­ac­ter­is­tic, for exam­ple machinability.

Many cop­per alloys have com­mon names, such as oxy­gen-free cop­per (99.95% Cu min), beryl­li­um cop­per (0.02 to 0.2% Be), Muntz met­al (Cu40Zn), Naval brass (Cu-39.5Zn‑0.75Sn), and com­mer­cial bronze (Cu-10Zn).


Many of the phys­i­cal prop­er­ties of cop­per alloys are impor­tant to the weld­ing process­es, includ­ing melt­ing tem­per­a­ture, coef­fi­cient of ther­mal expan­sion, and elec­tri­cal and ther­mal con­duc­tiv­i­ty. Cer­tain alloy­ing ele­ments decrease the elec­tri­cal and ther­mal con­duc­tiv­i­ties of cop­per and cop­per alloys.


Sev­er­al alloy­ing ele­ments have pro­nounced effects on the weld­abil­i­ty of cop­per and cop­per alloys. Small amounts of volatile, tox­ic alloy­ing ele­ments are often present in cop­per and its alloys. As a result, the require­ment of an effec­tive ven­ti­la­tion sys­tem to pro­tect the welder and/​or the weld­ing machine oper­a­tor is more crit­i­cal then when weld­ing fer­rous metals.

Zinc reduces the weld­abil­i­ty of all brass­es in rel­a­tive pro­por­tion to the per­cent of zinc in the alloy. Zinc has a low boil­ing tem­per­a­ture, which results in the pro­duc­tion of tox­ic vapors when weld­ing cop­per-zinc alloys.

Sil­i­con has a ben­e­fi­cial effect on the weld­abil­i­ty of cop­per-sil­i­con alloys because of its deox­i­diz­ing and flux­ing actions.


Tin increas­es the hot-crack sus­cep­ti­bil­i­ty dur­ing weld­ing when present in amounts from 1 to 10%. Tin, when com­pared with zinc, is far less volatile and tox­ic. Dur­ing weld­ing, tin may pref­er­en­tial­ly oxi­dize rel­a­tive to cop­per. The results will be an oxide entrap­ment, which may reduce the strength of the weldment.

Tena­cious Oxides

Beryl­li­um, alu­minum, and nick­el form tena­cious oxides that must be removed pri­or to weld­ing. The for­ma­tion of these oxides dur­ing the weld­ing process must be pre­vent­ed by shield­ing gas or by flux­ing, in con­junc­tion with the use of the appro­pri­ate weld­ing cur­rent. The oxides of nick­el inter­fere with arc weld­ing less than those beryl­li­um or alu­minum. Con­se­quent­ly, the nick­el sil­vers and cop­per-nick­el alloys are less sen­si­tive to the type of weld­ing cur­rent used dur­ing the process. Beryl­li­um con­tain­ing alloys also pro­duce tox­ic fumes dur­ing the welding.


Oxy­gen can cause poros­i­ty and reduce the strength of welds made in cer­tain cop­per alloys that do not con­tain suf­fi­cient quan­ti­ties of phos­pho­rus or oth­er de-oxi­dizes. Oxy­gen may be found as a free gas or as cuprous oxide. Most com­mon­ly weld­ed cop­per alloys con­tain deox­i­diz­ing ele­ment, usu­al­ly phos­pho­rus, sil­i­con, alu­minum, iron, or manganese.

Iron and man­ganese do not sig­nif­i­cant­ly affect the weld­abil­i­ty of the alloys that con­tain them. Iron is typ­i­cal­ly present in some spe­cial brass­es, alu­minum bronzes, and cop­per-nick­el alloys in amounts of 1.4 to 3.5%. Man­ganese is com­mon­ly used in these same alloys, but at low­er con­cen­tra­tions than iron.

Free-Machin­ing Additives 

Lead, sele­ni­um, tel­luri­um and sul­fur are added to cop­per alloys to improve machin­abil­i­ty. Bis­muth is begin­ning to be used for this pur­pose as well when lead-free alloys are desired. These minor alloy­ing agents, while improv­ing machin­abil­i­ty, sig­nif­i­cant­ly affect the weld­abil­i­ty of cop­per alloys by ren­der­ing the alloys hot-crack sus­cep­ti­ble. The adverse effect on weld­abil­i­ty is evi­dent with about 0.05% of the addi­tive and is more severe with larg­er con­cen­tra­tions. Lead is the most harm­ful of the alloy­ing agents with respect to hot-crack susceptibility.

Fac­tors Affect­ing Weldability

Besides the alloy­ing ele­ments that com­prise a spe­cif­ic cop­per alloy, sev­er­al oth­er fac­tors affect weld­abil­i­ty. These fac­tors are the ther­mal con­duc­tiv­i­ty of the alloy being weld­ed, the shield­ing gas, the type of cur­rent used dur­ing weld­ing, the joint design, the weld­ing posi­tion, and the sur­face con­di­tion and cleanliness.

Effect of Ther­mal Conductivity

The behav­ior of cop­per and cop­per alloys dur­ing weld­ing is strong­ly influ­enced by the ther­mal con­duc­tiv­i­ty of the alloy. When weld­ing com­mer­cial cop­pers and light­ly alloyed cop­per mate­ri­als with high ther­mal con­duc­tiv­i­ties, the type of cur­rent and shield­ing gas must be select­ed to pro­vide max­i­mum heat input to the joint. This high heat input coun­ter­acts the rapid head dis­si­pa­tion away from the local­ized weld zone.

Depend­ing on sec­tion thick­ness, pre­heat­ing may be required for cop­per alloys with low­er ther­mal con­duc­tiv­i­ties. The inter­pass tem­per­a­ture should be the same as for pre­heat­ing. Cop­per alloys are not post-weld head treat­ed as fre­quent­ly as steels, but some alloys may require con­trolled cool­ing rates to min­i­mize resid­ual stress­es and hot shortness.

Weld­ing Position

Due to the high­ly flu­id nature of cop­per and its alloys, the flat posi­tion is used when­ev­er pos­si­ble for weld­ing. The hor­i­zon­tal posi­tion is used in some fil­let weld­ing of com­er joints and T‑joints.

Pre­cip­i­ta­tion-Hard­en­able Alloys

The most impor­tant pre­cip­i­ta­tion-hard­en­ing reac­tions are obtained with beryl­li­um, chromi­um, boron, nick­el, sil­i­con, and zir­co­ni­um. Care must be tak­en when weld­ing pre­cip­i­ta­tion-hard­en­able cop­per alloys to avoid oxi­da­tion and incom­plete fusion. When­ev­er pos­si­ble, the com­po­nents should be weld­ed in the annealed con­di­tion, and then the weld­ment should be giv­en a pre­cip­i­ta­tion-hard­en­ing heat treatment.

Hot Crack­ing

Cop­per alloys, such as cop­per-tin and cop­per-nick­el, are sus­cep­ti­ble to hot crack­ing at solid­i­fi­ca­tion tem­per­a­tures. This char­ac­ter­is­tic is exhib­it­ed in all cop­per alloys with a wide liq­uidus-to-solidus tem­per­a­ture range. Severe shrink­age stress­es pro­duce inter­den­drit­ic sep­a­ra­tion dur­ing met­al solid­i­fi­ca­tion. Hot crack­ing can be min­i­mized by reduc­ing restraint dur­ing weld­ing, pre­heat­ing to slow the cool­ing rate and reduce the mag­ni­tude of weld­ing stress­es, and reduc­ing the size of the root open­ing and increas­ing the size of the root pass.


Cer­tain ele­ments (for exam­ple, zinc, cad­mi­um, and phos­pho­rus) have low boil­ing points. Vapor­iza­tion of these ele­ments dur­ing weld­ing may result in poros­i­ty. When weld­ing cop­per alloys con­tain­ing these ele­ments, poros­i­ty can be min­i­mized by high­er weld speeds and a filler met­al low in these elements.

Sur­face Condition

Grease and oxide on work sur­faces should be removed before weld­ing. Wire brush­ing or bright dip­ping can be used. Milis­cale on the sur­faces of alu­minum bronzes and sil­i­con bronzes is removed for a dis­tance from the weld region of at least 13 mm, usu­al­ly by mechan­i­cal means. Grease, paint, cray­on marks, shop dirt, and sim­i­lar con­t­a­m­i­nants on cop­per-nick­el alloys may cause embrit­tle­ment and should be removed before weld­ing. Milis­cale on cop­per-nick­el alloys must be removed by grind­ing or pick­ling; wire brush­ing is not effective.

Cop­per Weld­ing Alloys

The ide­al elec­trode mate­r­i­al would have the com­pres­sive strength of tool steel and the con­duc­tiv­i­ty of sil­ver. Unfor­tu­nate­ly, no such mate­r­i­al exists. So sev­er­al dif­fer­ent cop­per alloys have been devel­oped. All RWMA rec­om­mend­ed mate­ri­als have high­er anneal­ing or soft­en­ing tem­per­a­tures than pure cop­per, togeth­er with improved com­pres­sive strength and wear resis­tance. Because the cop­per has been alloyed to achieve high­er strength and wear prop­er­ties, there is some sac­ri­fice in conductivity.

Cop­per Alloys Classes:

Class 1: This class is most often spec­i­fied for weld­ing Alu­minum and oth­er high­ly con­duc­tive mate­ri­als. This is the most con­duc­tive of the RWMA Alloys. It is also the soft­est (and has the low­est strength and wear characteristics).

Class 2: This class of cop­per alloy is the most wide­ly used and rec­om­mend­ed cop­per alloy. It is rec­om­mend­ed for a wide range of steel alloys. The mate­r­i­al is rec­om­mend­ed for spot, seam, pro­jec­tion weld­ing, and cross wire weld­ing. It has slight­ly low­er con­duc­tiv­i­ty than class 1, and has high­er strength and wear characteristics.

Class 3: This one has the low­est con­duc­tiv­i­ty, but the high­est strength prop­er­ties of the main three grades of cop­per elec­trode mate­r­i­al. It is rec­om­mend­ed for most appli­ca­tions where high strength and wear resis­tance are imperative.

For more infor­ma­tion, con­tact Robots​.com experts today at 8777626881 or you can reach rep­re­sen­ta­tives online.

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