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During arc welding there is a zone adjacent to the weld metal that reaches high temperatures but does not melt. What is the name of this region? ✔✔Heat Affect Zone (HAZ) In parallel electrical circuits, the voltage across each resistor is the same since each path is connected to the same voltage source. Select the correct statement. A. in each parallel path the resistance must be equalized to create equal voltage. B. the current flowing in each parallel path must be the same as the voltage. C. the current flowing in each parallel path depends on the resistance in each path D. the current flowing in each parallel path depends on the capacitance in each path ✔✔C. the current flowing in each parallel path depends on the resistance in each path Welding is a joining process that by definition requires: ✔✔The application of either heat or pressure The duty cycle of a welding power supply is based upon delivering its rated output for a given number of minutes. Which of the following statements is correct. A. a 300 amp/60% duty cycle machine is rated to deliver 300 amps for 6 minutes in a ten minute period B. a 300 amp/30% duty cycle machine is rated to deliver 300 amps in a ten minute period C. a 250 amp/30% duty cycle machine is rated to deliver 250 amps for 30 minutes separated by 10 minutes at rest D. a 300 amp/60% duty cycle machine is rated to deliver 500 amps maximum for 6 minutes in a ten minute period ✔✔A. a 300 amp/60% duty cycle machine is rated to deliver 300 amps for 6 minutes in a ten minute period Conventional transformer-rectifiers; A. convert direct current into alternating current B. convert alternating current into direct current
C. convert alternating current into pulsed current D. convert direct current into pulsed current ✔✔B. convert alternating current into direct current A conventional diode placed in a circuit allows the passage of current in one direction only. A silicon controlled rectifier(SCR) operates slightly differently. How does it work? A. an SCR conducts current in both directions until turned on and current flow is then prevented B. an SCR is non-conductive until turned onland then allows current to flow in both directions C. an SCR is non-conductive until turned on, allowing current to flow in one direction only until the flow of current stops D. an SCR is a unique rectifying device which allows only alternating c1:1rrent to flow until turned off ✔✔C. an SCR is non-conductive until turned on, allowing current to flow in one direction only until the flow of current stops What is the term for voltage measured across the output terminals of a welding machine when no current is being drawn? A. diode voltage B. operating voltage C. open circuit voltage D. terminal voltage ✔✔C. open circuit voltage A 60% duty cycle means that the power supply can deliver its rated output for: A 60% of the rated output only B. 60% over the rated output followed by 4 minutes at rest C. 6 minutes at rest followed by 4 minutes at rated output D. 6 minutes at rated output followed by 4 minutes at rest ✔✔D. 6 minutes at rated output followed by 4 minutes at rest The DC output of a single phase power supply can be "ripply" and does not produce the friendliest DC arc. How is this problem overcome? A. single phase power supplies produce the smoothest DC of all common machines
D. to convert electrode positive to electrode negative ✔✔B. to convert DC current to high frequency AC current How is power flow analyzed in alternating current circuits? A. AC circuits can be evaluated the same as DC circuits when RMS values of voltage and current are used B. when analysing AC circuits, inductive and capacitive reactance must be included C. average current in an AC circuit is zero and therefore no work is done D. the peaks and valleys of sine wave curves balance to zero with the load ✔✔C. average current in an AC circuit is zero and therefore no work is done Which of the following methods is commonly used to control the output of a transformer? A. an auxiliary power supply which feeds the secondary as required B. a saturable reactor in series with the output C. resistance placed in parallel with the primary of the transformer D. taps on the secondary of the transformer ✔✔D. taps on the secondary of the transformer A transformer type welding power source without a rectifier outputs what type of current? A. direct current B. alternating current C. high frequency current D. pulsed direct current ✔✔B. alternating current When gas tungsten arc welding steels electrode polarity is most commonly; A. electrode positive B. electrode negative C. alternating current D. electrode square wave ✔✔B. electrode negative
A disadvantage of SCR control is that the output is very 'choppy'. How is the output made more suitable for welding? A. the output is smoothed out by the addition of capacitors B. the large inductor or choke will be added to the circuit C. the output from an SCR bridge is smooth enough for welding purposes D. the diodes added to all SCR controlled machines to prevent "choppy" output ✔✔A. the output is smoothed out by the addition of capacitor Gas tungsten arc and plasma arc welding power sources are commonly designed with high frequency units. What does the high frequency unit do? A. increases heat input due to the increased frequency which increases the total time at high current flow B. outputs high voltage, low current to create and maintain a stable conductive path for the flow of power C. decreases the cleaning action created by electrode negative polarity present in alternating current arcs D. outputs balanced current flow between electrode positive and electrode negative half cycles ✔✔B. outputs high voltage, low current to create and maintain a stable conductive path for the flow of power Gases are not normally electrically conductive. To start an arc; A. requires high voltage B. requires high inductance 'C. requires high current D. requires AC power ✔✔A. requires high voltage What voltage is required to cause 5 amps of current to flow through a resistance of 22 ohms? A. 110 volts B. 0.22 volts C. 4.4 volts
Conventional transformer-rectifiers; A. convert high frequency current into lower voltage output B. convert alternating current into direct current at lower than line voltage C. convert low voltage directcurrent into high frequency alternating current D. convert high voltage alternating current into low voltage, high frequency direct current ✔✔D. convert high voltage alternating current into low voltage, high frequency direct current Name the two main methods of arc shielding. ✔✔Flux shielding and gas shielding. In which direction do the electrons flow in an electrical arc? From anode to cathode, or cathode to anode? ✔✔Cathode to anode. In arc welding, the electric arc is intensely hot with temperatures exceeding: ✔✔ 30000 °C Which arc welding process has the highest arc efficiency? And what is its approximate value? ✔✔Submerged arc welding. 90 top 95%. How do the arc voltage and arc stiffness change when the arc length is increased? ✔✔Arc voltage increases and arc stiffness decreases. What is the generic name for the electrode used in GTAW and does it melt to provide filler metal for the weld? ✔✔Tungsten electrode. In the GTAW process what type of penetration and weld width can be expected when using D.C. electrode positive? ✔✔Shallow penetration and a wide weld. Which polarity is chosen most often for direct current GTAW welding of steels and why? ✔✔Direct current electrode negative. More heat is produced at the workpiece leading to deeper weld penetration.
Why must the shielding gas for GTAW be completely inert? ✔✔Presence of active gases like oxygen and carbon dioxide will oxidize the tungsten electrode and limit its life. State two advantages of the GTAW process. ✔✔It gives high quality deposits, and the process can be used to weld virtually all metals and alloys. What does SMAW stand for? ✔✔Shielded Metal Arc Welding Why is SMAW a very commonly used welding process? ✔✔It provides great flexibility in terms of the broad range of materials and their thicknesses that can be joined in all welding positions. Constant voltage power sources are preferred for SMAW.True or false? ✔✔False. Why is care necessary in proper storage and handling of electrodes for welding steels? ✔✔Improperly stored electrodes can pick up moisture leading to increased weld metal hydrogen content and therefore increased risk of cold cracking in the weld zone. Larger diameter electrodes are preferred for welding the root passes in V grooves and for out of position welds.True or false? ✔✔False. Constant voltage power sources is generally used for GMAW. True or false? ✔✔True. Which metal transfer mode in GMAW would be applied for welding (a) cast iron, (b) aluminum alloy? ✔✔(a) Short circuiting mode, (b) Spray. Between 100% C02 and 95%Ar-5%C02, which shielding gas will you chose to ensure spray transfer in semi-automatic welding of carbon steel with ER49S-6 wire? ✔✔95%Ar-5%C
b) All positions except V-down c) Welding with C02 shielding gas only d) Welding in the overhead position with electrodes 3.2 mm (1/8")or larger ✔✔c) Welding with C shielding gas onl Rutile type flux cored electrodes operate on: a) DCEN and give a globular type arc b) DCEP and give a globular type arc c) DCEN and give a spray type arc d) DCEP and give a spray type arc ✔✔d) DCEP and give a spray type arc Which of the following gases is required to achieve spray transfer when welding carbon steels? a) Argon b) Carbon-dioxide c) Helium d) Nitrogen ✔✔a) Argon For the ER49S-G classification, the chemistry requirements of the electrode: a) are specified by the welding supervisor b) are specified in the electrode standard c) are specified by the electrode manufacturer d) are not required to meet specific chemistry requirements ✔✔d) are not required to meet specific chemistry requirements Which of the following is an important function of the electrode coating? a) protect the molten metal b) add hydrogen to weld metal c) prevent slag removal
d) maintain electrode temperature e) decrease deposition rate ✔✔a) protect the molten metal Calcium carbonate is an important ingredient in which type of electrodes? a) cellulose electrodes b) rutile electrodes c) basic electrodes d) oxide electrodes ✔✔c) basic electrodes Tungsten electrodes of a given type and size should be operated near their: a) Maximum current carrying capability b) Minimum current carrying capacity c) Midpoint current carrying capacity d) Widest range of current carrying capacity ✔✔a) Maximum current carrying capability Shielded metal arc welding of aluminum should be used for: a) Critical applications b) Non-critical applications c) Thick aluminum applications d) Thin aluminum applications ✔✔b) Non-critical applications In general, which GMAW mode of transfer is NOT suited for the welding of thin sheet steel? a) spray transfer b) dip transfer c) short-circuiting transfer d) pulsed-spray transfer ✔✔d) pulsed-spray transfer Toughness can be best defined as:
a) All position welding b) Vertical down fillets and grooves only c) Flat grooves and horizontal fillets only d) Overhead fillets and grooves only ✔✔c) Flat grooves and horizontal fillets only Basic type flux cored electrodes operate on: a) DCEP only and give a smooth spray type arc b) DCEP and DCEN and are characterized by globular transfer c) DCEN only and are characterized by globular transfer d) DCEP only and give a rough spray type arc ✔✔b) DCEP and DCEN and are characterized by globular transfer Which of the following is considered to be a Low Alloy Steel Electrode? a) E b) E c) E d) E4918-A e) E7018-R ✔✔d) E4918-A The toughness of submerged arc welding weldments is affected when ____ is present in the weld a) Nitrogen b) Oxygen c) Aluminum d) co2 ✔✔b) Oxygen Welds made with self-shielded electrodes can suffer from excessive nitrogen absorption. Excessive nitrogen in the weld pool will result in: a) Gross porosity during solidification
b) Oxides that are removed by the fluxing action c) No noticeable weld deposit defects d) Cracking in the centre of the weld deposit ✔✔a) Gross porosity during solidification When welding aluminum with the gas tungsten arc process using a pure tungsten electrode a ball is formed on the end. This is accomplished by: a) Striking an arc on a steel block using DCEP polarity b) Striking an arc on a copper block using AC or DCEP polarity c) Striking an arc on the aluminum using DCRP d) Grinding a ball on the end of the tungsten ✔✔b) Striking an arc on a copper block using AC or DCEP polarity Gas metal arc welding electrodes for welding aluminum have a wider range of alloys available than shielded metal arc welding. Which series of alloys is available for gas metal arc welding but not available for shielded metal arc welding? a) 5xxx b) 9xxx c) 4xxx d) 3xxx ✔✔a) 5xxx Slag from shielded metal arc welding electrodes used to weld aluminum can be corrosive if not completely removed, In some cases washing the final weld with hot water and will remove any residual slag and reduce corrosion a) 5% silver nitrate b) 10% sulphuric acid c) 5% nitric acid d) 15% hydrochloric acid ✔✔c) 5% nitric acid What does the third digit (E4918) in the identification system of covered electrodes represent? a) Weld deposit strength
What are the effects of increasing the arc voltage when using an active flux for submerged arc welding of carbon steels? ✔✔It increases the flux consumption and in the case of active fluxes, the Mn and Si content of the weld metal is increased. What is the source of heat in the resistance welding process? ✔✔Electrical resistance of the workpieces Which of arc welding process( es) is (are) non-consumable electrode type? ✔✔GTAW The electron beam welding process results in: ✔✔Narrow, deep penetrating weld and heat affected zones In thermite welding, what is the name of the reaction from which the required heat and molten metal is obtained? ✔✔Exothermic In electroslag welding, what is the usual cooling medium used on the copper shoes? ✔✔Water With a tungsten arc, most of the current across the arc is carried by: ✔✔Electrons The chief feature of an electron beam weld is: ✔✔A very narrow weld and heat affected zone Which gases are used with the GMAW process? ✔✔Argon and C02 and their mixtures in various proportions Which of the following processes is a non-consumable electrode process? ✔✔GTAW Projection welding is a resistance spot welding process in which: ✔✔The current is localized by using a projection or embossment on the part to be joined Which of the following processes is not used in the overhead position? ✔✔SAW
Witch of the following shielding gas (mixtures) is suitable for spray transfer when welding with 1.1 mm diameter GMAW ER49S-6 wire? ✔✔5% C02 - 95% Ar The deposition rate of some SMAW electrodes is increased by including which of the following in the flux coating: ✔✔Iron powder The electrode in flux cored arc welding is: ✔✔Tubular wire containing flux or other ingredients What would be a typical current range for a 4mm (5/32") E4918 (E7018) electrode: ✔✔ 150 - 220 amperes In electric arc welding what is the proportion of total energy that is converted into heat that eventually enters the plate known as? ✔✔Efficiency With manual welding the technique will influence the energy input. Of the following techniques, which involves the higher energy input? a) Weaving techniques b) Depositing stringer beads ✔✔a) Weaving techniques When GTA welding, a strong positive voltage is applied to the tungsten electrode because of its high melting point. ✔✔True To initiate an arc requires high current and low voltage power. ✔✔False How much current will flow through a resistance of 200 ohms when 100 volts is applied? ✔✔0.5 amps A generator consists of rotating conductors in a stationary magnetic field and an alternator consists of rotating magnetic field inside the conductor windings. ✔✔True
Welding cable length should be kept minimum where possible. Because there is a voltage drop over the length of the cable, it must be compensated in order to maintain the correct welding voltage. ✔✔True Choose the correct statement to match the welding power characteristics between (1) is CV power source, (2) is CC power source, (1) is CC power source and (2) is CV power source ✔✔(1) is CC power source and (2) is CV power source How much current will flow through a resistance of 50 ohms when 25 volts is applied? ✔✔0.5 amps Inductance is a property of a circuit just as resistance is a property. Changing current flow through a circuit creates an "induced" magnetic field. What effect does the frequency of AC current have on the strength of the Induced magnetic field? ✔✔The higher the frequency, the stronger the induced magnetic field From the following, select the ferrous metals; Wrought iron, Copper, Aluminum, Carbon steel, Stainless steel ✔✔a) Wrought iron d) Carbon steel e) Stainless steel What is taconite? ✔✔Iron ore "Limestone is a fluxing agent that removes impurities to form a slag. True or false? ✔✔True In the basic oxygen furnace what does the term "basic" refer to: The chemical nature of the molten steel, The chemical nature of the refractory lining of the furnace, The chemical nature of the steel after pouring ✔✔The chemical nature of the refractory lining of the furnace In the electric furnace, what provides the heat to melt the metal charge? ✔✔An arc between carbon electrodes and the metal
What are the advantages of continuous casting over ingot casting? ✔✔Less segregation, less rolling required, less cost When making semi-killed steel what is the usual deoxidizing material which is added to the melt Magnesium, Silicon, Aluminum Manganese ✔✔b) Silicon "Alloy steels and steels with greater than 0.3% carbon are fully killed." True or false? ✔✔True "Metals have a crystalline structure in which the atoms are arranged in an irregular pattern."True or false? ✔✔False Ferrite, austenite, and cementite are known as: ✔✔Phases Which is the harder- martensite or fine pearlite? ✔✔martensite Complete the following sentence- If a steel Is being heat treated to produce maximum hardness, it must be heated prior to quenching at a temperature sufficient to remove any .......... present. ✔✔Ferrite Martensite is extremely brittle. Can martensite be tempered to enhance its toughness? ✔✔Yes When steel is normalized how is the steel cooled? ✔✔In air What are the three major groups of steels? ✔✔Carbon Steel, low alloy steel, alloy steel. Chromium has an effect on hardenabillty, what other major property does It affect? ✔✔Corrosion resistance In the SAE and AISI system of steel classification what does the designation 1020 signify? ✔✔Carbon steel with 0.20% carbon
