It is defined as metal pieces or parts that arejoin together by heating the surfaces to thepoint of melting with electric arc, hammeringetc.
Def: A group of welding processes that join metalsat temperatures essentially below the meltingpoints of the materials, without the addition ofa brazing filler metal. Pressure may or may notbe applied to the joint. Examples include coldwelding , ultrasonic wielding, friction wieldingetc.
Cold welding is a solid state process in whichpressure is used at room temperature toproduce coalescence of metals with substantialdeformation at the weld. both butt and lapjoints can be cold welded.
At least one of the metals must be ductilewithout excessive work hardening Total absence of applied heating Dissimiliar metals can be jointed. Surface preparation is important.
The parts to be weldedare first cleaned A short section of thepart is sheared The parts are clampedin a die with someinitial extention A forging force isapplied to completewelding.DiesWorkpiece WorkpieceBefore weldingAfter welding
Cold welded butt joints are used in themanufacturing of aluminium ,copper,gold, silver, and platinum wire. Most commonly, successive reels of wire arejoined for continuous drawing to a smallerdiameter. Manufacture of kitchen utensils.
Def: A solid state welding process in whichcoalescence is produced at the faying surfacesby the application of high frequency vibratoryenergy while the work pieces are held togetherunder moderately low static pressure.
A static clampingforce is appliedperpendicular to theinterface between thework pieces. The contactingsonotrode oscillatesparallel to theinterface. Combined effect ofstatic and oscillatingforce producesdeformation whichpromotes welding.AnvilMassSonotrodetipClampingforcewedge TransducerForceWeldmentVibration
No heat is applied and no melting occurs. Permits welding of thin to thick sections. Welding can be made through some surfacecoatings. Pressures used are lower ,welding times areshorter, and the thickness of deformed regionsare thinner than for cold welding.
The thickness of the component adjacent to thesonotrode tip must not exceed relatively thingages because of power limitations of theequipment. Process is limited to lap joints. Butt welds can not be made because there is nomeans of supporting the work pieces andapplying clamping force.
Def:Friction welding is a solid state joining processthat produces coalescence by the heatdeveloped between two surfaces bymechanically induced surface motion.
One of the work pieces isattached to a rotating motordrive, the other is fixed in anaxial motion system. One work pieces is rotated atconstant speed by the motor. An axial or radial force isapplied. The work pieces are broughttogether under pressure for apredetermined time, or untila preset upset is reached Then the drive is disengagedand a break is applied to therotating work piece.WorkpiecesNon-rotating viseMotorChuckSpindleHydraulic cylinderBrake
Frequently competes with flash or upsetwelding when one of the work pieces to bejoined has axial symmetry. Used in automotive industry to manufacturegears, engine valves, and shock absorbers. Used to join jet engine compressor parts.
One of the work piece isconnected to a flywheel; the other isclamped in a nonrotating axial drive. The fly wheel isaccelerated to thewelding angularvelocity. The drive is disengagedand the work piece arebrought together Frictional heat isproduce at the interface.An axial force isrequired to completewelding.SpindleWorkpiecesNon-rotating chuckHydraulic cylinderFlywheelMotorChuck
In both mechanism welding heat is developedby frictional heat and plastic deformation Both method use axial force for upsettingpurpose. In both mechanism axial pressure may bechanged at the end of the rotation
Continuous drive1)One of the work piecesdirectly connected to arotating motor drive.2)Rotational speed may beconstant until the brake isapplied.3)Rotational energy of thework piece dissipatesthrough friction and plasticdeformation, producingwelding heat.Inertia drive1)One of the work pieceis connected to the flywheel.2)Rotational speeddecreases continuouslyto zero during theprocess.3)Kinetic energy of thefly wheel is dissipatesthrough friction andplastic deformation
The resistance welding process involves the joining ofmaterials through the resistance of an electricalcurrent. The electrical current generates heat andpressure which creates bonds between the parts beingwelded. Most resistance welding applications areapplied to metals, but plastic materials may also beused. This quick and efficient application usesmachines with copper electrodes that inject materialswith heat. Once the desired amount of heat is injected,the materials begin to cool; a bond is formed during thecooling process. What makes resistance weldingdifferent than regular welding is it uses both heat andpressure to weld, while regular welding only usedheat.
There are six different resistance weldingprocesses; each process involves the formationof a bond through heat produced by anelectrical current and pressure created by theelectrodes to hold the materials together.
1)Resistance Spot Welding- This is when a bond isformed at the joining surface of the material beingwelded. 2)Projection Welding- This involves the bonding ofmetal materials. 3)Flash Welding- This is when a bond is formed overthe entire area of the welded materials. 4)Upset Welding- This process connects materialsprogressively along a joint. 5)Percussion Welding- This is the welding of materialsthrough heat produced by an arc due to a rapiddischarge of energy. 6)High Frequency Resistance Welding- This is the
High speed< 0.1 seconds in automotive spotwelds Excellent for sheet metal applications, < ¼-inch No filler metal
Higher equipment costs than arc welding Nondestructive testing Low tensile and fatigue strength Not portable Lap joint require additional metal.