www.welding-and-cutting.info Technical journal for welding and allied processes The Welding Institute Issue 2014 05 Welding and cutting technology at EuroBLECH 2014 - Announce- ments from exhibitors SRM stud welding - a new arc stud welding variant Designing thin sheet joints executed with little heat in a way appropriate for operation Every production challenge requires individual technologies to achieve optimal results. To ensure that you ma- nufacture and handle the best possible products and component parts, CLOOS supports you with excellent arc welding expertise and a broad product portfolio. No matter if automated or manual – with CLOOS you always weld and cut accurately, at the highest economic and technological level. Humans are individual. Just like welding. Stud welding TODAY We make a CLEAN JOB of it! www.soyer.de THE SRM EFFECT (Patent No.: 10 2004 051 389) . . www.hz-1.com SPECIAL EDITION
Transcript
www.welding-and-cutting.info Technical journal for welding and allied processes
The Welding Institute
Welding Cutting final indd 2 24 01 2012 15:47:24
Issue
201405
Welding and cutting technologyat EuroBLECH 2014 - Announce-ments from exhibitors
SRM stud welding - a new arcstud welding variant
Designing thin sheet jointsexecuted with little heat in a wayappropriate for operation
Weld your way.
Every production challenge requires individual technologies to achieve optimal results. To ensure that you ma-nufacture and handle the best possible products and component parts, CLOOS supports you with excellent arc welding expertise and a broad product portfolio. No matter if automated or manual – with CLOOS you always weld and cut accurately, at the highest economic and technological level.www.cloos.de
Humans are individual.Just like welding.
Visit us at EuroBLECH 201421st to 25th October 2014in Hanover, GermanyHall 13, Booth D25
The new stud welding in the radial-sym-metric magnetic field can make an impor-tant contribution to the improvement of thearc stud welding efficiency by repeatable,good welding quality, basically without bloweffect problems. A characteristic feature ofSRM stud welding is an extremely even anddefined partial melting of stud and sheetwith a considerably reduced energy inputinto the welded connection, reduced spatterformation and a small bead.
Transferring the advantages tolarger stud diameters Arc welding using the SRM technologyresults from first experience in 2005 [1] forstuds up to a diameter of 10 mm at alloyedsteel. In 2009, Heinz Soyer Bolzen-schweißtechnik GmbH, Wörthsee/Ger-many, presented this technology to an in-ternational audience on the occasion of the“Schweissen & Schneiden“ Fair in Essen.The reaction to the welding results of theSRM technology with simultaneous use of a
patented special welding stud oftype “HZ1” by Soyer was alreadyvery positive. For studs with a di-ameter of more than 10 mm, how-ever, no empirical values wereavailable then. In the industry,there were requests regarding theapplicability, especially with largerstud diameters, and for out-of-po-sition welding to both the WeldingTraining and Research InstituteSLV Munich and the machinemanufacturer.
In the further development ofthe SRM technology, it has in themeantime been possible to trans-fer its advantages regarding the useof the comparatively little energyinput and the small, however veryeven weld penetration geometry tostuds of sizes M12 and M16. Atthese diameters, as well, optically
In SRM stud welding (welding in a radi-al-symmetric magnetic field), a radial-sym-metric magnetic field in combination witha shielding gas atmosphere protects the arcfrom external influence. This results in high-er efficiency due to repeatable, high weldingquality without arc blow problems. In prac-tice, this means very even and defined par-tial melting of stud and sheet with consid-erably reduced energy input into the weldedconnection, reduced spatter formation anda small bead. The arc is protected in the area of thewelding point. Without this additional pro-tection, there are often blow effects on thearc considerably disturbing the applicationof the drawn arc stud welding proceduresresulting in incomplete bead formationand/or undercutting. So the user has to dealwith additional expenses in the ongoing pro-duction monitoring, however also in regu-larly required work tests and/or procedurequalifications according to DIN EN ISO14555.
298 Welding and Cutting 13 (2014) No. 5
REPORTS
SRM stud welding – a new arc stud welding variantappealing welded connections could be pro-duced, hardly causing any rework due to dis-turbing bead accumulation and spatters.The determination of relevant characteris-tics and the optimisation of the welding andboundary conditions were completed withinthe scope of a research project of BayerischeForschungsstiftung (Bavarian ResearchFoundation), Munich. The benefit of the SRM technology wasdiscovered in 2005 rather accidentally. Be-fore, magnetic fields were used in stud weld-ing primarily for the even movement of thearc at a hollow section, similar to MBP weld-ing (pressure welding with magneticallymoved arc) (Fig. 1). This technology devel-oped as sleeve or nut welding [2, 3] has beenused with an additional fixture for the cre-ation of the magnetic field and the shieldinggas cover in the market for years. The shield-ing of the welding point by a magnetic fieldin order to reduce unintended arc deflectionhas also been known for years; it has, how-ever, only established itself in individual cas-es, for example with alloyed materials. The SRM technology is an extension ofdrawn arc stud welding for common, unal-loyed and alloyed steel materials that aresuitable for stud welding. The weld pool pro-tection is implemented by means of com-mercially available shielding gases (argonor mixed gases with CO2) in combinationwith magnetic arc influencing. A ceramicring is not necessary. The SRM technologydistinguishes itself by the following features:• high welding quality with smooth bead
surface, little weld penetration depthand high carrying capacity,
• welding process with little blow effect,• good repeatability,• little welding energy and thus only min-
imum distortion of the component,• all welding positions possible (down-
hand position, vertical wall, overhead).For studs of sizes M12 and M16, welding con-ditions for the creation of highly loadable studwelds were determined after development ofthe suitable shielding gas magnetic field ad-ditional device; these conditions comply withthe current requirements of DIN EN ISO14555 with regard to bending and tensile loadas well as weld penetration shape.
Very simple device extension Fig. 2 shows the course of the SRM weld-ing procedure as variant of drawn arc stud
Fig. 1 • Sleeve or nut welding with thesupport of a magnetic field for the evenmovement of the arc at the ring-shapedhollow section: welded sleeve connec-tion at alloyed steel with good bead ap-pearance (top), a magnetic field sur-rounds the welding point and togetherwith the shielding gas, results in the arcmovement (bottom).
298_302_WC_reports_w30000052__ 17.09.14 16:50 Seite 298
Welding and Cutting 13 (2014) No. 5 299
welding. Except for the actuation of the ra-dial-symmetric magnetic field, the weldingprocess exactly corresponds to drawn arcshielding gas stud welding. Before the be-ginning of the main current phase, the addi-tional magnetic field is activated which sub-sequently influences the arc with regard toits movability of the arc starting points at studand sheet even with complete cross-section.The entire front face of the stud is evenly par-tially melted within a shorter period than inthe drawn arc procedures known until now.In this phase, partial rotations of the arcaround the stud axis with increasing rotationradius are identified. The device extension for the SRM studwelding is very simple. Depending on the di-ameter, you use the commercially available“PH-3N” welding gun for M12 or “PH-4L” forM16, which are in each case equipped with
an optimised SRM shielding gas magneticfield fixture according to Fig. 3. For the M12studs, there is a small, compact fixture (Fig.3a) that is hardly larger than a commonshielding gas fixture. For M16 studs, the fix-ture according to Fig. 3b was enlarged ac-cordingly, whereas the gas flow direction andthe degassing concept have been changed.With the “BMK-16i” (up to M12) and “BMK-30i” (currently up to M16) inverter powersources by Heinz Soyer Bolzenschweißtech-nik, the magnetic field is activated by an SRMmodule which can be retrofitted. These in-verter power sources are especially suitablefor stud welding using the SRM technology. SRM welding does not require specialtraining of the users. The stud welding pa-rameters are basically set at the weldingguns, welding heads and at the power source,as usual. In addition, you only need to set
the current intensity for the SRM magneticfield to up to 1.5 A depending on the mag-netic coil. Fig. 4 shows the adapted magnetic fieldshielding gas fixture at the support feet ofthe “PH-4L” welding gun with additionalelectrical connection to supply the magneticcoil. This is basically also possible when us-ing welding heads with stationary operation.As shielding gases, you can – in addition topure argon – particularly use mixed gaseswith 2.5, 10 or 18% CO2 share. The mixedgas Ar + 10% CO2 has proven of value in caseof high requirements regarding bead ap-pearance and carrying capacity of the SRMwelded connections.
Fig. 2 • Procedural process in SRM welding as variant of drawn arc stud welding: The magnetic influence on the arc leads to the even partial melting ofthe entire front face even with full cross-sections with identifiable rotation effects during the main current phase.
Fig. 3 • Additional fixture with different degassing concepts to create magnetic field and shieldinggas cover: a) small size up to M12, b) larger fixture for M16 with changed gas flow direction.
Fig. 4 • SRM welding gun for M16 studs – theconnection of the magnetic field shielding gasfixture to the support feet of welding guns andwelding heads is also easily possible with sta-tionary handling.
a) b)
298_302_WC_reports_w30000052__ 17.09.14 16:50 Seite 299
REPORTS
300 Welding and Cutting 13 (2014) No. 5
the bead, the weld pool depth slightly in-creases. This weld penetration geometry ishardly susceptible to pore and crack forma-tion if unalloyed steels suitable for stud weld-ing are used. When dipping the stud into theweld pool, only a small amount of melt isdisplaced whereas a smooth bead surfacewith almost fillet weld shaped bead geometryresults. Fig. 6 contains statistic data for the com-parison of the results of tensile tests at M12welds for the SRM, ceramic ring and shield-ing gas stud welding variants when usingmaterials from the same production batch.Every variant is based on 20 tests at studsmade of the stud material S235 (stability class5.8), welded at 10 mm thick sheets made ofS355. In all welded connections, the fractureposition was within the stud. Using the dia-gram, you can thus only evaluate the distri-bution of the stud material used in an overalldistribution range between 49 and 52 kN. Asmean values, the medians in the selected
box/plot presentation are at the same levelbetween 50.3 and 50.6 kN. Fig. 7 contains the welding dates usedregarding the individual welding variants. Itshows views and weld penetration shapes ofM12 studs that were welded using differentdrawn arc variants from Fig. 6. For this com-parison, the ceramic ring stud welding wasperformed with a welding energy of about 6kJ, the shielding gas stud welding with about5 kJ and the SRM stud welding with about 4kJ. In contrast to the SRM welds, stud weldswith the ceramic ring and shielding gas vari-ants frequently fail in the welding zone if thelow welding energy of 4 kJ is used. This “low-energy concept” of SRM stud welding par-ticularly distinguishes itself by the small beadand the little weld pool thickness. It can bedetermined as result of this examinationwithout doubt that with regard to the carry-ing behaviour with static bending and tensileloads and with regard to the repeatability,SRM stud welding can be used as innovative
Fig. 5 • View and weld penetration shape of aSRM welding connection with M12 stud madeof S235 material (stability class 5.8); the tensiletest resulted in a fracture position in the studafter contraction in the thread – a) completebead formation, fracture position in the stud,breaking force 50.5 kN, b) even, thin meltingzone, little weld penetration depth in the sheet,no weld defects visible.
Fig. 6 • Statistics of com-parative tensile tests atM12 stud welding con-nections – 20 tests pervariant, fracture positionin the stud in all weldedconnections, stud materialS235 (stability class 5.8)from the same batch;welding data see Fig. 7;repeatability and processreliability of SRM studwelding is equal to theconventional stud weldingprocedures.
Fig. 7 • Comparison of different drawn arc variants with M12 studs made of material S235 (stabilityclass 5.8); all studs were made of the same batch; sheet material S355, 10 mm thick. In another testseries, the basic sheet material broke due to bad Z quality. The procedure requires good surfacepreparation and good adjustment of shielding gas and welding parameters. If this is not done care-fully, failure of SRM stud welds in the welded connection cannot be excluded.
Similar welding result for M12 andM16 studsResults for M12 studs The effect of the influenced arc in SRMstud welding becomes particularly clear inthe weld penetration geometry. The veryeven partial melting is similar to that in thecapacitor discharge stud welding procedurein which the sheet only shows little weldpenetration depth. The carrying behaviourof stud welding connections is proven usinga simple bending test (site test) or a statictensile test according to DIN EN ISO 14555. Fig. 5 shows the view and weld penetra-tion shape of an SRM welding connectionwith M12 studs made of S235 material whichhas a tensile strength of about 560 MPa instability class 5.8. Fig. 5a documents the frac-ture position of studs in tensile tests requiredaccording to DIN EN ISO 14555. In this ex-ample, the stud breaks at a load of 50.5 kNafter contraction in the thread. In the section(Fig. 5b), you can clearly see the typical, even,thin melting zone as faultless link betweenstud and sheet. The weld penetration depthin the sheet is about 0.5 mm. In the area of
a)
b)
298_302_WC_reports_w30000052__ 17.09.14 16:50 Seite 300
Welding and Cutting 13 (2014) No. 5 301
alternative to the conventional stud weldingprocedures (ceramic ring or shielding gas).
Results for M16 studs In the examined SRM welds with M16studs, the bending tests were passed withoutproblems if suitable welding and boundaryconditions were used. Fig. 8 shows view andsection of an SRM stud weld at M16 studsmade of material S235 with a welding energyof 6.0 kJ. With regard to appearance and weldpenetration shape, the welding result resem-bles the previous experience with M12 studs.The welding times don‘t have to be extendedas compared to smaller diameters. To ensuresufficient partial melting, only the currentintensity is slightly increased from about 900A to 1,200 A and the coil current of the largerSRM fixture according to Fig. 3b is increasedto 1.1 A. In a ceramic ring stud weld withcomparable design, a welding energy ofabout 18 kJ is used with this diameter. The reduced and even weld penetrationresults in considerably reduced distortion ofthe component. With regard to the blow ef-fect, the even weld penetration can e.g. alsobe achieved with unilateral ground connec-tion. In static tensile tests, M16 stud weldsunder the shielding gases argon and Ar +18% CO2 break in the basic stud material at
breaking tensions of about 560 N/mm2 of thestud batch used. It can be determined basedon the results for M16 studs that SRM studwelding also offers potential for the econom-ic use with larger diameters than 12 mm.
High process reliability also inout-of-position welding One special advantage of the SRM tech-nology becomes apparent in out-of-positionstud welding, particularly at a vertical wall(PC position). Fig. 9 shows an SRM studwelding connection of an M12 stud out-of-position (PC) under shielding gas M21 – ArC– 18 with magnetic field additional fixture,carried out in the same form at unalloyedsheet steel. If you compare upper side andlower side of the weld in Fig. 9, you can see asimilar and complete bead formation. Fromthe section, you can hardly see any influenceof the PC welding position as compared toPA (downhand position = sheet horizontal). Fig. 10 shows SRM stud welding connec-tions with M16 studs that have been weldedout-of-position (PC) (at vertical wall) undershielding gas M21 – ArC – 18. In the weldingconnection in Fig. 10a, SRM results in a com-plete bead formation at the upper side ofthe welding. The bending test is passed. Thewelding connection in Fig. 10b, however,
Fig. 8 • View and weld penetration shape of anSRM welding connection with a stud M16 x 60at a sheet made of S355; a) condition bendingangle of more than 60° satisfied, b) thin meltingzone, slightly increased partial melting in thecentre due to the influence of the shielding gas;welding conditions: current intensity: 1,170 A,welding time: 220 ms, lift: 2.8 mm, penetrationdepth: 0.6 mm, SRM field: 1100 mA, weldingenergy: 6.0 kJ, shielding gas: M21 – ArC – 18
Fig. 9 • SRM studwelding out-of-posi-tion, PC (at verticalwall), under shieldinggas M21 – ArC – 18with magnetic fieldadditional fixture,stud: M12, S235,sheet: S355, weldingconditions: current in-tensity: 900 A, weld-ing time: 170 ms, lift2.0 mm, immersiondepth: 0.5 mm,shielding gas: M21 –ArC – 18
a)
b)
298_302_WC_reports_w30000052__ 17.09.14 16:50 Seite 301
REPORTS
302 Welding and Cutting 13 (2014) No. 5
Due to the low-energy concept, the SRMstud welding connections distinguish them-selves by very even bead and weld penetra-tion shapes. The radial-symmetric magneticfield effectively protects the arc from bloweffects, also during out-of-position welding.The shielding gases pure argon and argonwith up to 18% CO2 share are suitable forstud welding with the SRM procedure up toM16 (unalloyed steel). The SRM procedurerequires an effective magnetic field shieldinggas fixture as well as careful adjustment ofthe welding parameters to the boundaryconditions. The device extension is in many casespossible even with existing welding invert-ers. At the welding guns and/or weldingheads, the necessary shielding gas field cre-ating unit is attached to the existing supportequipment without problems. The SRM technology as innovation ofstud welding, which already received nu-merous awards, is continuously advanced.Apart from the potential of welding largerstud diameters, research is currently fo-cussing on questions regarding the carryingcapacity under fatigue load with cyclic load-ing and thus regarding vibration resistance. One part of the results explained in thecontribution was determined within theframe of a current research and develop-ment study regarding SRM stud welding
which is promoted by BayerischeForschungsstiftung (Bavarian ResearchFoundation), Munich.
Heidi Cramer, Andreas Jenicek and MarcMüller, GSI Gesellschaft für Schweißtech-
nik International mbH, Niederlassung SLVMünchen, Munich/Germany,
Günter Forster, Karsten Hartz-Behrendand Jochen Schein, Universität der Bun-
[2] N. N.: Research report no. 5105/2000:Schweißen zylindrischer Hohlkörper aufungelochte und gelochte Bleche mittelsmagnetisch bewegtem Lichtbogen.Schweißtechnische Lehr- und Versuch-sanstalt SLV München, subsidiary of GSImbH, Munich 2000.
[3] N. N.: Research report no. 5124/2003: Licht-bogenschweißen von zylindrischenHohlkörpern (Buchsen, Muttern, etc.) mitmagnetisch bewegtem Lichtbogen an Alu-miniumwerkstoffen, AiF project no. 12.753.Schweißtechnische Lehr- und Versuch-sanstalt SLV München, subsidiary of GSImbH, Munich 2003.
Fig. 10 • Views of SRM studwelding connections withM16 studs made of S235 ata sheet made of S355 out-of-position, PC (at verticalwall), under shielding gasM21 – ArC – 18 before andafter the bending test; a) with SRM technology:even bead formation at up-per and lower side of thestud, bending test withbending angle of more than60° passed; b) without SRMtechnology: bead formationat upper side incomplete,fracture position partially inwelding zone with identifi-able undercutting at the up-per side; welding conditions:current intensity: 1,380 A,welding time: 200 ms, lift:2.7 mm, shielding gas: M20– ArC – 10 (Figures: Soyer(1b, 2, 3), SLV Munich)
carried out without SRM magnetic field butfor the rest identical welding parameters,shows an incomplete bead formation at theupper side. With this welding, the bendingtest is not passed. At the break position inthe welding zone, you can see undercuttingat the upper side. The SRM welding process distinguishesitself by good repeatability of the weldingresults which is particularly due to the littleblow effect. This could be confirmed bymeans of tests with partially unilateralground connection. So the SRM stud weld-ing can – with regard to process reliability –at least be used on the same level as estab-lished stud welding procedures. First usersfrom vehicle construction confirm the out-standing process reliability of this technol-ogy.
Permanently advancedtechnology With good repeatability for M12 andM16 steel studs made of unalloyed and al-loyed materials being suitable for studwelding, the SRM welding procedure sat-isfies the acceptance criteria of DIN ENISO 14555 even with extensive quality re-quirements. This could be proven bymeans of corresponding bending and ten-sile tests as well as using metallographicexaminations.
a) b)
298_302_WC_reports_w30000052__ 17.09.14 16:50 Seite 302
Stud welding
SIMPLE!made
Seite 7+8_Sonderdruck_WuC_05_2014.indd 1 13.10.2014 14:27:44
