Physics of Projection Welding

Projection Physics Lesson Objectives When you finish this lesson you will understand: The collapse of the projection during welding Factors effecting the projection collapse Learning Activities 1.View Slides; 2.Read Notes, 3.Listen to lecture 4.Do on-line workbook Keywords Current Concentration, Projection Collapse

[Reference: Resistance Welding Manual, p.3-13, RWMA] Projection Welding of Low Carbon Steel (Two Equal Thicknesses)

Functions of Electrode Force l The electrode force must hold the projection firmly against the mating part during the initial period of “weld time” where the current density is high and the collapse rate is rapid. l The electrode force must cause complete collapse after welding, so the resulting sheet separation is minimized. l The electrode force has a major influence on the degree of porosity in the weld nugget. It must be low enough to give proper projection collapse without metal expulsion and yet high enough to produce comparatively sound welds. l The suitable dynamic force characteristic must prevail without producing excessive initial impact force.

Effect of Weld Time Weld Time (Cycles) Nugget Diameter Projection Collapse Tensile-Shear Strength (lbs) Weld Time (Cycles)

Factors Affecting Heat Balance Projection Design Part Thickness Die Material Backing up the Weld Metal Conductivity Heating Speed

Projection Weld Formation [Reference: Resistance Welding Manual, p.3-9, RWMA] Stage 1 Stage 3 Stage 2 Stage 4

Projection Weld Formation (CONT.) [Reference: Resistance Welding Manual, p.3-9, RWMA] Stage 5 Stage 7 Stage 6 Stage 8

Link to projection weld video

Recommended Projection Designs [Reference: Recommended practice for resistance welding, AWS Document C1.1-66, AWS, 1966] T(in.) D(in.)H(in.)L(in.) / / / / / / / / / / / / / / /4 H T D T: Thickness of thinnest outside piece D: Diameter of projection H: Height of projection L: Minimum contacting overlap L

Effect of Welding Time Stage 1 Stage 5 Stage 2 Stage 6 Stage 3 Stage 7 Stage 4 Stage 8 [Reference: Resistance Welding Manual, p.3-9, RWMA]

Variation in Weld Head Position during Projection Welding inch Thick Steel [Reference: A study of projection welding, Welding Journal Research Supplement, 27(12), p.712s-713s, Hess & Childs] Weld Cool Current Electrode Position 60 Cycle Timing Trace Initial Collapse Final Collapse Nugget Expansion

Variation in Weld Force during Projection Welding inch Thick Steel [Reference: A study of projection welding, Welding Journal Research Supplement, 27(12), p.712s-713s, Hess & Childs] 1000 lbs. Weld Cool Time

Effect of Welding Current [Reference: A study of projection welding, Welding Journal Research Supplement, 27(12), p.712s-713s, Hess & Childs] Projection: D = 0.40” H = 0.027” Electrode Force: 1500 lbs Diameter of Fused Zone, in. 20,000 15,000 10,000 5,000 Welding Current, Amps 30 cycles 45 cycles 60 cycles

Relations between Weld Current, Weld Time and Weld Strength on inch Thick Mild Steel [Reference: Further studies in projection welding, Welding Journal Research Supplement, 28(1), p.15s-23s, Hess & Childs] Shear Nominal Tension Projection D = 0.10” H = 0.025” Electrode Force 400 lbs 10 cycles 15 cycles 20cycles Welding Current, Amps Weld Strength, lbs

Effect of Projection Shape Shear Normal Tension Projections Electrode Force D H lbs 0.010” 0.025” ” 0.025” Welding Current, Amps Weld Strength, lbs [Reference: Further studies in projection welding, Welding Journal Research Supplement, 28(1), p.15s-23s, Hess & Childs]

Effect of Electrode Material [Reference: Further studies in projection welding, Welding Journal Research Supplement, 28(1), p.15s-23s, Hess & Childs] RWMA Classification Group B, Class 12 RWMA Classification Group A, Class 2 RWMA Classification Group A, Class 3 Weld Time: 15 cycles Welding Current, Amps Fused Zone Diameter, inches

Effect of Weld Spacing on Nugget Development [Reference: A study of projection welding, Welding Journal Research Supplement, 27(12), p.712s-713s, Hess & Childs] (a) 1-in. Spacing (b) 3/4-in. Spacing (c) 1/2-in. Spacing

Additive Effect of Projection Weld Strengths for Multiple Welded Assemblies [Reference: Further studies in projection welding, Welding Journal Research Supplement, 28(1), p.15s-23s, Hess & Childs] Shear Normal Tension Weld Current: No. of welds x 6340 Amps Electrode Force: No. of welds x 400 lbs Weld Spacing: 0.75” Weld Time: 15 cycles Projection: D = 0.10” H = 0.025” AISI 1010 AISI 1015 AISI Number of Welds Weld Strength, lbs

Variations in Projection Weld Hardness [Reference: A study of projection welding, Welding Journal Research Supplement, 27(12), p.712s-713s, Hess & Childs] Fused Zone Thickness: 0.125” Weld Time: 45 cycles Distance across Weld, inches Hardness, VPN

Effect of Material Hardenability on Weld Strength [Reference: Further studies in projection welding, Welding Journal Research Supplement, 28(1), p.15s-23s, Hess & Childs] Shear Normal Tension Weld Time: 15 cycles Projection: D = 0.10” H = 0.025” Electrode Force: 400 lbs AISI 1010 AISI 1015 AISI Welding Current, Amps Weld Strength, lbs

Cold Projection Collapse [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] Annular : 0.110” Diam. Spherical: 0.075” Diam. Spherical: Diam. Spherical: Diam. Projection Height, inches Electrode Force, lbs

Nugget Development Using Spherical Projections for in. Thick Steel [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] 3760 Amps4950 Amps 4260 Amps5330 Amps

Nugget Development Using Annular Projections for in. Thick Steel [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] 4740 Amps5100 Amps 5520 Amps5940 Amps

Current Range Characteristics [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] Annular Projection Height: 0.015” Diameter: 0.110” Weld Time: 6 cycles Electrode Force: 225 lbs Spherical Projection Height: 0.020” Diameter: 0.075” Weld Time: 6 cycles Electrode Force: 150 lbs Weld Current, Amps Plug Diameter, inches 0.020”-1010 Steel

Strength Characteristics [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] Spherical Projection Height: 0.020”Diameter: 0.075” Electrode Force: 75 lbs Weld Time: 6 cyclesPickled in 50% HCl Shear Strength Normal Tension Annular Projection Height: 0.016” Diameter: 0.077” Electrode Force: 110lbs Shear Strength Normal Tension Welding Current, Amps Load, lbs 0.020”-1010 Steel

Effect of Weld Force on Strength Characteristics [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] 0.020”-1010 Steel Shear Normal Tension Annular Projection Height: 0.015”Diameter: 0.110” Weld Time: 6 cycles Electrode Force: 110 lbs Electrode Force: 130 lbs Load, lbs Welding Current, Amps

[Reference: Resistance Welding Manual, p.3-13, RWMA] Projection Welding Schedule of Light-Gauge Steels

Additive Effect of Multiple Projection Welds [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] Annular Projection Height: 0.015” Diameter: 0.110” Shear Normal Tension Theoretical Weld Time: 6 cycles Weld Current: 5200 Amps/weld Weld Pressure: 225 lbs/weld 0.020”-1010 Steel Number of Welds Load, lbs

Projection Design for Light- Gauge Steels [Reference: The projection welding of and inch steel sheet, Welding Journal Research Supplement, 29(9), p.3-13, Nippes & Gerken] 0.010” 0.020” 0.040” 0.062” 0.125” Sheet Thickness in. Projection Diameter in. Projection Height in. Punch Top Diameter in. Punch Height in. 30°

Typical Embossed Projection Design for Heavy-Gauge Steel Sheets [Reference: Resistance Welding Manual, p.3-4, RWMA] 90° 45° 60° 120° 0.45” 0.25” 0.094” 0.52” 0.15” 0.50”

Recommended Projection Geometries and Punch & Die Design for Heavy-Gauge Steel Sheets [Reference: Resistance Welding Manual, p.3-15, RWMA]

Projection Dimensions Vs. Sheet Thickness [Reference: Projection welding of steel in heavy gauges and in dissimilar thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s, Nippes & Gerken] Diameter Height Projection Dimension, inches

Electrode Force and Current Sequence for Heavy-Gauge Steel Sheets Time CurrentForce

Electrode Force and Current Sequence for Heavy-Gauge Steel Sheets (CONT.) Time CurrentForce

Nugget Vs. Current for Different Weld Times [Reference: Projection welding of steel in heavy gauges and in dissimilar thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s, Nippes & Gerken] Weld Time: 150 cycles Weld Time: 200 cycles Weld Time: 250 cycles Weld Time: 300 cycles 20,000 22,000 24,00026,000 28,000 30,000 Welding Current, Amps Diameter, inches

Nugget Size Vs. Welding Current for Different Electrode Forces [Reference: Projection welding of steel in heavy gauges and in dissimilar thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s, Nippes & Gerken] Electrode Force: 3000 lbs Electrode Force: 4000 lbs Electrode Force: 5000 lbs 20,000 22,000 24,000 26,000 28,000 30, Diameter, inches Welding Current, Amps

Weld Strength Vs. Welding Current [Reference: Projection welding of steel in heavy gauges and in dissimilar thicknesses, Welding Journal Research Supplement, 31(3), p.113s-125s, Nippes & Gerken] Shear Strength Normal Strength Two step current start, total weld time 250 cycles 20 cycles for each step 225 cycles weld time, forge force applied for first 25 cycles and end of weld 15,000 20,000 25,000 30,000 Welding Current, Amps Load, lbs x 10 2