Question & Answer

Describe the shielded metal arc-welding (SMAW) process.

Why is the heat transfer factor in arc-welding processes that utilize consumable electrodes greater

than in those that use nonconsumable electrodes?

What are the two basic methods of arc shielding?

Electrodes in arc welding are divided into two categories. Name and define the two types.

What do the terms arc-on time and arc time mean?

Define what an electrical arc is.

What is the fundamental feature that distinguishes fusion welding from solid-state welding?

Name the principal groups of processes included in fusion welding.

An axle-bearing surface made of high carbon steel has worn beyond its useful life. When it was

new, the diameter was 4.00 in. In order to restore it, the diameter was turned to 3.90 in to provide a

uniform surface. Next the axle was built up so that it was oversized by the deposition of a surface

weld bead, which was deposited in a spiral pattern using a single pass on a lathe. After the weld

buildup, the axle was turned again to achieve the original diameter of 4.00 in. The weld metal

deposited was a similar composition to the steel in the axle. The length of the bearing surface was

7.0 in. During the welding operation, the welding apparatus was attached to the tool holder, which

was fed toward the head of the lathe as the axle rotated. The axle rotated at a speed of 4.0 rev/min.

The weld bead height was 3/32 in above the original surface. In addition, the weld bead penetrated

1/16 in into the surface of the axle. The width of the weld bead was 0.25 in, thus the feed on the

lathe was set to 0.25 in/rev. Assuming the heat transfer factor was 0.80 and the melting factor was

0.65, determine (a) the relative velocity between the workpiece and the welding head, (b) the rate of

heat generated at the welding source, and (c) how long it took to complete the welding portion of

this operation.

A surfacing weld is to be applied to a rectangular low carbon steel plate that is 200 mm by 350 mm.

The filler metal to be added is a harder (alloy) grade of steel, whose melting point is assumed to be

the same. A thickness of 2.0 mm will be added to the plate, but with penetration into the base metal,

the total thickness melted during welding = 6.0 mm, on average. The surface will be applied by

making a series of parallel, overlapped welding beads running lengthwise on the plate. The

operation will be carried out automatically with the beads laid down in one long continuous

operation at a travel speed = 7.0 mm/s, using welding passes separated by 5 mm. Assume the

welding bead is rectangular in cross section: 5 mm by 6 mm. Ignore the minor complications of the

turnarounds at the ends of the plate. Assuming the heat transfer factor = 0.8 and the melting factor =

0.6, determine (a) the rate of heat that must be generated at the welding source, and (b) how long

will it take to complete the surfacing operation.

A spot weld was made using an arc-welding process. In a spot-welding operation, two 1/16-in-thick

aluminum plates were joined. The melted metal formed a nugget that had a diameter of ¼ in. The

operation required the power to be on for 4 sec. Assume the final nugget had the same thickness as

the two aluminum plates (1/8 in thick), the heat transfer factor was 0.80 and the melting factor was

0.50. Determine the rate of heat generation that was required at the source to accomplish this weld.

A fillet weld is used to join 2 medium carbon steel plates each having a thickness of 5.0 mm. The

plates are joined at a 90° angle using an inside fillet corner joint. The velocity of the welding head is

6 mm/sec. Assume the cross section of the weld bead approximates a right isosceles triangle with a

leg length of 4.5 mm, the heat transfer factor is 0.80, and the melting factor is 0.58. Determine the

rate of heat generation required at the welding source to accomplish the weld.

In a certain welding operation to make a fillet weld, the cross-sectional area = 0.025 in2 and the

travel speed = 15 in/min. If the heat transfer factor = 0.95 and melting factor = 0.5, and the melting

point = 2000°F for the metal to be welded, determine the rate of heat generation required at the heat

source to accomplish this weld.

The power source in a particular welding operation generates 125 Btu/min, which is transferred to

the work surface with heat transfer factor = 0.8. The melting point for the metal to be welded =

1800°F and its melting factor = 0.5. A continuous fillet weld is to be made with a cross-sectional

area = 0.04 in². Determine the travel speed at which the welding operation can be accomplished.

A welding operation on an aluminum alloy makes a groove weld. The cross-sectional area of the

weld is 30.0 mm2. The welding velocity is 4.0 mm/sec. The heat transfer factor is 0.92 and the

melting factor is 0.48. The melting temperature of the aluminum alloy is 650°C. Determine the rate

of heat generation required at the welding source to accomplish this weld.

Solve the previous problem except that the metal to be welded is high carbon steel, the

cross-sectional area of the weld = 25.0 mm2, and the melting factor = 0.6.

The welding power generated in a particular arc-welding operation = 3000 W. This is transferred to

the work surface with a heat transfer factor = 0.9. The metal to be welded is copper whose melting

point is given in Table 29.2. Assume that the melting factor = 0.25. A continuous fillet weld is to be

made with a cross-sectional area = 15.0 mm2. Determine the travel speed at which the welding

operation can be accomplished.

Compute the unit melting energy for (a) aluminum and (b) steel as the sum of: (1) the heat required

to raise the temperature of the metal from room temperature to its melting point, which is the

volumetric specific heat multiplied by the temperature rise; and (2) the heat of fusion, so that this

value can be compared to the unit melting energy calculated by Eq. (29.2). Use either the SI units orU.S. Customary units. Find the values of the properties needed in these calculations either in this

text or in other references. Are the values close enough to validate Eq. (29.2)?

In a controlled experiment, it takes 3700 J to melt the amount of metal that is in a weld bead with a

cross-sectional area of 6.0 mm2 that is 150.0 mm long. (a) Using Table 29.2, what is the most likely

metal? (b) If the heat transfer factor is 0.85 and the melting factor is 0.55 for a welding process, how

much heat must be generated at the welding source to accomplish the weld?

Solve the previous problem, except that the metal to be welded is aluminum, and the corresponding

melting factor is half the value for steel.

A groove weld has a cross-sectional area = 0.045 in2 and is 10 inches long. (a) What quantity of

heat (in Btu) is required to accomplish the weld, if the metal to be welded is medium carbon steel?

(b) How much heat must be generated at the welding source, if the heat transfer factor = 0.9 and the

melting factor = 0.7?

A U-groove weld is used to butt weld 2 pieces of 7.0-mm-thick titanium plate. The U-groove is

prepared using a milling cutter so the radius of the groove is 3.0 mm. During welding, the

penetration of the weld causes an additional 1.5 mm of material to be melted. The final crosssectional

area of the weld can be approximated by a semicircle with a radius of 4.5 mm. The length

of the weld is 200 mm. The melting factor of the setup is 0.57 and the heat transfer factor is 0.86.

(a) What is the quantity of heat (in Joules) required to melt the volume of metal in this weld (filler

metal plus base metal)? Assume the resulting top surface of the weld bead is flush with the top

surface of the plates. (b) What is the required heat generated at the welding source?

A fillet weld has a cross-sectional area of 25.0 mm2 and is 300 mm long. (a) What quantity of heat

(in joules) is required to accomplish the weld, if the metal to be welded is low carbon steel? (b)

How much heat must be generated at the welding source, if the heat transfer factor is 0.75 and the

melting factor = 0.63?

Make the calculations and plot on linearly scaled axes the relationship for unit melting energy as a

function of temperature. Use temperatures as follows to construct the plot: 500°F, 1000°F, 1500°F,

2000°F, 2500°F, 3000°F, and 3500°F. On the plot, mark the positions of some of the welding

metals in Table 29.2. Use of a spreadsheet program is recommended for the calculations.

Make the calculations and plot on linearly scaled axes the relationship for unit melting energy as a

function of temperature. Use temperatures as follows to construct the plot: 200°C, 400°C, 600°C,

800°C, 1000°C, 1200°C, 1400°C, 1600°C, 1800°C, and 2000°C. On the plot, mark the positions of

some of the welding metals in Table 29.2. Use of a spreadsheet program is recommended for the

calculations.