Welding · Joining of Materials · GATE PI

In gas tungsten arc welding process, the material coated on pure tungsten electrode to enhance its current carrying capacity is

Brazing and soldering are

Which of the following welding process results in the smallest heat affected zone

In resistance seam welding, the electrode is in the form of a

The current in Amperes used in resistance spot welding of plain carbon steel sheets ($$1$$ to $$3$$ $$mm$$ thick) lies within the range:

The metal powder used in Thermit welding of steel is:

High speed electron beam welding is focused on the weld spot using

In resistance welding, heat is generated due to the resistance between

Which of the following powders should be fed for effective oxy-fuel cutting of stainless steel

The consumption of an oxy-acetylene flame for cutting of steel contains more oxygen

The composition of an oxy-acetylene flame for cutting of steel contain more oxygen.

Filler material is ......... A...... in resistance welding and the heat generated in the process is directly proportional to ........ B.........

(A). used / not used$$\,\,\,\,\,\,\,\,\,$$ $$\,\,\,\,\,\,\,\,\,$$ (B). square of the current / cube of the current

The joint configuration best suited for adhesive bonding is

The type of coated electrode most widely used for welding low carbon steel is

High alloy steel components are preheated before welding for reducing

In spot welding of aluminium sheets, the welding current should be .........A........ and weld time should be kept ............B......... than for $$MS$$ sheet of same thickness.

(A). higher / lower, (B). higher / lower

Continuous rails for Indian railways are welded by ........ Welding process.

....................... is the non-fusion method of joining dissimilar metals with metals whose melting temp is greater than $${400^ \circ }C$$.

With increasing joint thickness, the tensile strength of a brazed joint

The mode of metal transfer in $$C{O_2}$$-$$MIG$$ welding at low temperature is

In $$TIG$$ welding a ...........A. .......... and ..........B.......... electrode is used.

A. non-consumable / consumable
B. coated / bare

In welding brass with oxy-acetylene flame, the type of flame used is

Two flat steel sheets, each of $$2.5$$ $$mm$$ thickness, are being resistance spot welded using a current of $$6000$$ $$A$$ and weld time of $$0.2$$ $$s.$$ The contact resistance at the interface between the two sheets is $$200\,\,\mu \Omega $$ and the specific energy to melt steel is $$10 \times {10^9}\,\,J/{m^3}.$$ A spherical melt pool of diameter $$4$$ $$mm$$ is formed at the interface due to the current flow. Consider that electrical energy is completely converted to thermal energy. The ratio of the heat used for melting to the total resistive heat generated is _____________

In linear gas tungsten arc welding of two plates of the same material, the peak temperature $$T$$ (in $$K$$) is given as ܶ$$T = {{{c_1}q} \over \alpha },$$ where $$q$$ is the heat input per unit length (in $$J/m$$) of weld, $$\alpha $$ is the thermal diffusivity (in $${m^2}/s$$) of the plate materials and $${C_1}$$ is a constant independent of process parameters and material types. Two welding cases are given below.

where, $$V$$ is welding voltage, $$I$$ is welding current, $$v$$ is welding speed, and $$k,$$ $$\rho $$ and $$C$$ refer to the thermal conductivity, the density and the specific heat of the plate materials, respectively. Consider that electrical energy is completely converted to thermal energy. All other conditions remain same.

The ratio of the peak temperature in Case $${\rm I}$$ to that in Case $${\rm I}{\rm I}$$ is

Two aluminium alloy plates each $$10$$ $$mm$$ thick and $$1$$ $$m$$ long are welded without crowning by multipass tungsten inert gas butt welding. The joint configuration is $$V$$-type with $${60^ \circ }$$ angle and root gap is maintained at $$5$$ $$mm.$$ If electrode of $$5$$ $$mm$$ diameter with $$500$$ $$mm$$ length is used for welding, then the number of electrodes required is

In an arc welding operation carried out with a power source maintained at $$40$$ volts and $$400$$ amperes, the consumable electrode melts and just fills the gap between the metal plates to be butt-welded. The heat transfer efficiency for the process is $$0.8,$$ melting efficiency is $$0.3$$ and the heat required to melt the electrode is $$20$$ $$J/m{m^3}$$. If the travel speed of the electrode is $$4$$ $$mm/s$$, the cross-sectional area, in $$m{m^2}$$, of the weld joint is ________________.

In a $$DC$$ $$arc$$ welding operating, the length characteristic was obtained as $${V_{arc}} = 20 + 5l$$ where the $$arc$$ length $$l$$ was varied between $$5mm$$ and $$7mm.$$ Here $${V_{arc}}$$ denotes the arc voltage in volts. The $$arc$$ current was varied from $$400A$$ to $$500A.$$ Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are

During a steady gas metal arc welding with direct current electrode positive polarity, the welding current, voltage and weld speed are $$150A,$$ $$30V$$ and $$6m/min$$ respectively. A metallic wire electrode of diameter $$1.2mm$$ is being fed at a constant rate of $$12m/min.$$ The density, specific heat and melting temp of the wire electrode are $$7000$$ $$kg/{m^3},$$ $$500$$ $$J/kg$$ and $${1530^ \circ }C$$ respectively. Assume the ambient temp to be $${30^ \circ }C$$ and neglect the latent heat of melting. Further consider that $$2/{3^{rd}}$$ of the total electrical power is available for melting of the wire electrode. The melting efficiency (in percentage) of the wire electrode is

Autogeneous gas tungsten arc welding of a steel plate is carried out with welding current of $$500A,$$ voltage of $$20V,$$ and weld speed of $$20mm/min.$$ Consider the heat transfer efficiency from the arc to the weld pool as $$90\% $$. The heat input per unit length (in $$kJ/mm$$) is

Which of the following powders should be fed for effective oxy-fuel cutting of stainless steel

Two pipes of inner diameter $$100mm$$ and outer diameter $$110mm$$ each are joined by flash butt welding using $$30V$$ power supply. At the interface, $$1mm$$ of material melts from each pipe which has a resistance of $$42$$ Ohms.If the unit melt energy is $$64.4$$ $$MJ/{m^3}$$, then time required for welding (in $$S$$) is

Aluminium strips of $$2mm$$ thickness are joined together by resistance spot welding process by applying an electric current $$6000$$$$A$$ for $$0.15sec$$. The heat required for melting aluminium is $$2.9J/m{m^3}.$$ The diameter and thickness of the weld nugget are found to be $$5$$ $$mm$$ and $$2.5mm$$ respectively. Assuming the electrical resistance to be $$75$$ micro-ohms, the percentage of total energy utilized in forming the weld nugget is

Which pair among the following solid state welding processes uses heat from an external source
$$P$$- Diffusion welding
$$Q$$- Friction welding
$$R$$- Ultrasonic welding
$$S$$- Forge welding

The $$DC$$ power source for arc welding has the characteristic $$3V + 1 = 240,$$ where $$V=$$ Voltage and $${\rm I}\,\, = $$ current in amp. For maximum arc power at the electrode, voltage should be set at

Two $$8$$ $$mm$$ thick steel plates are placed $$5$$ $$mm$$ apart and welded by a butt joint. Welding is carried out at $$20$$ $$V$$ and speed of $$5$$ $$mm/sec.$$ Heat transfer efficiency is $$0.80.$$ If the heat required to melt steel is $$10$$ $$J/m{m^3}$$ and melting efficiency is $$0.625.$$ The weld current (in Amperes) will be

In a fabrication shop, a $$T$$-joint is to be made between two plates using a chain intermittent, double fillet weld of $$6$$ $$mm$$ leg length. The intermittent welds are $$40$$ $$mm$$ long and spaced $$80$$ $$mm$$ apart, edge to edge.

The welding symbol of the joint is

Match List - I (welding problems) with List - II (Causes) and select the correct answer using the codes given below the lists:

Consider the following statements :

The magnitude of residual stresses in welding depends upon
$$1.$$ Metal melted / deposited
$$2.$$ Design of weldment
$$3.$$ Support and clamping of components
$$4.$$ Welding process used

Which of the statements given above are correct?

Consider the following statements:

The size of the heat affected zone (HAZ) will increase with
$$1.$$ increased starting temperature
$$2.$$ increased welding speed
$$3.$$ increased thermal conductivity of the base metal
$$4.$$ increase in base metal thickness

Which of the statements given above are correct?

Which of the following process can be used for welding of Aluminium alloys
$$P.$$ Submerged arc welding
$$Q.$$ Gas metal arc welding
$$R.$$ Electroslag welding
$$S.$$ Gas tungsten arc welding

Match List - I (welding defects) with List - II (causes) and select the correct answer using the codes given below the lists

A $$900$$ $$mm$$ long steel plate is welded by manual metal arc welding process using welding current of $$150$$ $$A,$$ arc voltage of $$20$$ $$V$$ and welding speed of $$300$$ $$mm/min.$$ If the process efficiency of is $$0.8$$ and surface resistance is $$36$$ micro-ohm, the heat input will be

The cold cracking susceptibility of the heat affected zone in an arc weld is influenced by
$$P.$$ Entraped hydrogen,
$$Q.$$ Residual stresses
$$R.$$ Marternsitic transformation
$$S.$$ Slag inclusion

In spot pulsed laser welding of aluminium plates (density $$ = 2700kg/{m^3},$$ specific heat $$=896J/kg,$$ melting temp $$=933K,$$ latent heat of melting $$ = 398\,\,kJ/kg)$$ at a temp of $${30^ \circ }C,$$ pulse with energy of $$0.5J$$ is focused onto an area of $$0.05m{m^2}.$$ If the entire energy is coupled into the material, what will be the depth of weld assuming the $$CS$$ area of the weld is circular and is uniform throughout its depth and only heat conduction in the direction of penetration

During gas welding of copper sheets a neutral flame was used consuming $$8$$ liters of acetylene. But the weld was found to be defective. So it was re-welded using an oxidizing flame. The likely consumption of oxygen in liters will be

In welding process, penetration is increased by

Match the following

In welding a mild steel sheet using an oxy-acetylene flame, the total amount of acetylene consumed was $$8.0$$ liters the oxygen consumption from the cylinder is

Resistance spot welding of two steel sheets is carried out in lap joint configuration by using a welding current of $$3$$ $$KA$$ and a weld time of $$0.2s.$$ A molten weld nugget of volume $$20m{m^3}$$ is obtained. The effective contact resistance is $$200\mu \Omega .$$ The material properties of steel are given as (i) latent heat of melting $$1400$$ $$kJ/kg,$$ (ii) density $$8000$$ $$kg/{m^3},$$ (iii) melting temp $${1520^ \circ }C$$, (iv) specific heat $$0.5$$ $$kJ/kgC.$$ The ambient temp is $$20C.$$

Heat (in Joules) used for producing weld nugget will be (assuming $$100\% $$ heat transfer efficiency

Resistance spot welding of two steel sheets is carried out in lap joint configuration by using a welding current of $$3$$ $$KA$$ and a weld time of $$0.2s.$$ A molten weld nugget of volume $$20m{m^3}$$ is obtained. The effective contact resistance is $$200\mu \Omega .$$ The material properties of steel are given as (i) latent heat of melting $$1400$$ $$kJ/kg,$$ (ii) density $$8000$$ $$kg/{m^3},$$ (iii) melting temp $${1520^ \circ }C$$, (iv) specific heat $$0.5$$ $$kJ/kgC.$$ The ambient temp is $$20C.$$

Heat (Joules) dissipated to the base metal will be (neglecting all other heat losses)

A weld is made using $$MIG$$ welding process with the following welding parameters: Current: $$200A;$$ Voltage: $$25V;$$ Welding speed: $$18$$ $$cm/min;$$ wire diameter: $$1.2$$ $$mm;$$ Wire feed rate: $$4$$ $$m/min;$$ Thermal efficiency of the process: $$65\% $$

The heat input per unit length of the weld in $$kJ/cm$$ is:

A weld is made using $$MIG$$ welding process with the following welding parameters: Current: $$200A;$$ Voltage: $$25V;$$ Welding speed: $$18$$ $$cm/min;$$ wire diameter: $$1.2$$ $$mm;$$ Wire feed rate: $$4$$ $$m/min;$$ Thermal efficiency of the process: $$65\% $$

The area of cross section of weld bead in $$m{m^2}$$ is:

A weld is made using $$MIG$$ welding process with the following welding parameters: Current: $$200A;$$ Voltage: $$25V;$$ Welding speed: $$18$$ $$cm/min;$$ wire diameter: $$1.2$$ $$mm;$$ Wire feed rate: $$4$$ $$m/min;$$ Thermal efficiency of the process: $$65\% $$

The heat input per unit length of the weld in $$kJ/cm$$ is:

A weld is made using $$MIG$$ welding process with the following welding parameters: Current: $$200A;$$ Voltage: $$25V;$$ Welding speed: $$18$$ $$cm/min;$$ wire diameter: $$1.2$$ $$mm;$$ Wire feed rate: $$4$$ $$m/min;$$ Thermal efficiency of the process: $$65\% $$

The area of cross section of weld bead in $$m{m^2}$$ is:

Two plates with symmetrical $$V$$ joint penetration of $$V$$ angle $$60deg$$ are to be arc welded in a single pass. The power $$P(kW)$$-arc length $$L$$ $$(mm)$$ characteristic is given by $$P=4+0.8L-0.1$$$${L^2}$$. Assuming that the top surface of the weld is flat & flush with the plate top surface, & the energy losses are $$20\% $$, the density of filler material is $$8gm/cc$$ and the energy required to melt $$1$$ $$gm$$ is $$1400$$ joules. The plate dimensions are $$1000mm$$ length & $$5mm$$ thickness. The maximum welding speed is .......................

The voltage-arc length characteristics of a power source is $$V=20+40L,$$ where $$V=$$ operating voltage in volts and $$L=$$ arc length in $$cm.$$ The open circuit voltage and short circuit current for arc lengths ranging from $$3$$ to $$5mm$$ and current from $$400$$ to $$500$$ amps during welding operation are

Two sheets of low carbon steel $$1.5mm$$ thick each are spot welded by passing a current $$10000$$ amps for $$5$$ cycles in $$50$$ $$Hz$$ main supply.

i) What is the heat generated due to the supply of power if effective resistance has $$200$$ micro ohms,

ii) The maximum indentation is $$10\% $$ of sheet thickness and density of the spot weld nugget $$8$$ $$gm/cc.$$ If $$1380$$ Joules are required to melt $$1gm$$ of steel, determine heat required for welding operation if $$D=6SQRT$$ $$(t)$$ to determine nugget diameter $$D$$ and assume the nugget size to be equal to metal between the two electrodes

In $$MIG$$ welding the power source characteristics is $${V_p} = 36 - {\rm I}/60$$ and the arc characteristics is $${V_a} = 2{L_a}\,\,\,\, + 27.$$ Find the change in power of the arc if the arc length changed from $$2mm$$ to $$4mm.$$ If the maximum current capacity of the power source is $$300$$ Amps, the maximum arc length sustainable is

A resistance welder is rated at $$50$$ $$kVA,$$ at $$50\% $$ duty cycle. Secondary voltage is always constant at $$25$$ volts. If a job requires $$1500$$Amps current, determine the maximum welding time in a total cycle time of $$30$$$$secs$$.

The voltage-arc length characteristic of a $$DC$$ arc is given by $$V=20+40L.$$ where $$L=$$ arc length in $$cm.$$ The power source characteristics can be approximated by a straight line. Open circuit is $$80V$$ and short circuit current $$1000$$Amps. The optimum arc length in $$mm$$