Welding Final

What is a tip cleaner? When and why should it be used?

A tip cleaner is like a very small drill bit and made for use in cleaning the tips of welding and cutting torches. It is pushed into the hole of the tip and slid in and out to remove any carbon buildup from within the tip.

What is a plug weld?

A type of weld used to overlap members by welding through circular holes or slots

What should be the depth of penetration?

1/3 - 1/2 total thickness of the weld bead

What is the general recommendation for adequate ventilation, in cu ft of air-flow per minute per welder?

2000 cubic feet

What should be the position of the torch for welding a T-joint?

45 degrees from the surface of the base metal

What is a carburizing flame?

A carburizing flame has three flame zones - the third one being a white cone surrounding the inner, brighter white cone. There is also an orange acetylene feather at the end of the flame.

What is the difference between an open and a closed butt joint?

A closed joint has no gap between the pieces being joint, an open joint does

What is a cover pass and why is it used?

A cover pass is the final weld pass deposited & it provides additional reinforcement to a multiple-pass weld and provides a good appearance

What is meant by a flashback in an oxyacetylene torch?

A flashback is a recession of the flame into or even back of the mixing chamber of the torch; it can quickly damage the torch and if it occurs the torch much be shut off immediately.

Of the various types of corner joints, which is the strongest?

A full-open corner joint is the strongest as it permits welding on both sides of the material and provides good stress distribution.

What are the characteristics of a neutral flame?

A neutral flame has a well-defined white cone surrounded by a blue outer cone that is fairly luminous.

What is a circuit?

A path taken by electric current from one terminal of a welding power source through a conductor and to the other terminal of the machine

What is a fillet weld?

A weld approximately triangular cross section that joins two surfaces at approximately right angles

How are the sizes of welding machines rated?

According to the max amount of current the machine can supply when operated at a specific duty cycle

What has been done to ensure uniformity of electrode specifications?

American Welding Society (AWS) established classifications

What term is used to indicate rate of current flow in a circuit?

Ampere

What is meant by an oxidizing flame?

An oxidizing flame is one in which there is an excess amount of oxygen, with an inner cone that is shorter than a neutral cone, more pointed and almost purple color rather than white and produces a slight hissing sound.

Why should containers be thoroughly cleaned and safety processed before any welding or cutting is done on them?

Any residue of contaminants left in the container could result in an explosion if not cleaned properly before welding

What is the proper method of testing for gas leaks?

Applying soapy water to the connections and submerging the hose in clean water.

What should be done if the electrode sticks to the plate?

Attempt to twist and break off the electrode, or remove the clamp to break the circuit and then attempt to break off the electrode

What factors must be taken into consideration when selecting an electrode?

position of weld, properties of base metal, type of joint, type of welding current

What two methods may be used in striking an arc?

tapping or scratching methods

What is polarity?

the positive or negative state of an object

When making a lap weld, what determines the proper joint overlap?

the thickness of the metal and the strength required

Why should strict attention be given to proper clothing and eye protection?

to prevent injury

In striking an arc, why should the electrode be withdrawn instantly?

to prevent the electrode from sticking to the base metal

How must the head and eyes be protected while arc welding?

wearing a welding mask with an automatic dimming filter to protect your face / eyes

How far should the acetylene needle valve be opened when lighting the torch?

½ a turn

What determines the proper arc length?

Having the arc length by approximately the same distance as the diameter of the electrode

What causes undercutting?

Improper work angle, too much current, or quick travel speed

What is the difference between AC and DC current?

In a DC circuit the current is always moving in the same directions, in an AC circuit, the direction the current is flowing is constantly changing

What are the basic types of T-joints?

Butt, tee, lap, edge & corner

How are sizes of welding tips indicated?

By the diameter of its opening

What should you do if your welding equipment malfunctions?

Get it repaired by a trained service technician

What are some of the basic principles which contribute to good joint geometry?

Good joint geometry uses root openings and groove angles that require the least amount of weld metal, but still provide proper accessibility to the root of the joint

Why is overhead welding more difficult to perform?

Gravity affects the molten weld pool, making it difficult to control

When is a weaving motion used?

Used on the cover pass to obtain the necessary weld width when covering intermediate passes

What general practice should be followed regarding ventilation during the performance of any welding operation?

Cross body movement of air close to the fume source

What instrument is used to measure voltage?

Voltmeter

Why does this usually indicate a poor weld?

Because there is poor fusion

How can undercutting be avoided?

Changing the electrode angle

Oxy-hydrogen is often used for what operations?

Commonly used for underwater welding as it can be used at higher pressure than acetylene.

Why should the holder never be placed on the workbench while the current is on?

Could cause arc flash, damage to the equipment, and/or electric shock

What is one advantage of an AC welder?

Doesn't have as many arc blow problems as DC - arc blow can be caused by magnetism in the material being welded or can be induced by the arc's current

Explain the identifying symbols of the electrode classification E-6010.

E: electrode 60: min tensile strength in 1000th/in^2 1: weld position 0: type of coating, weld current & operating characteristics of the electrode

What is gained by selecting electrodes with coatings containing powered iron?

Faster travel speeds, slag is easier to remove, low spatter

Fast-fill electrodes are intended for what types of welding?

Flat position production welding

How much should the cylinder valve be opened on an acetylene cylinder? How much on the oxygen cylinder?

For acetylene, ¼ turn. For oxygen, open all the way.

How does gas metal-arc welding differ from gas tungsten-arc welding?

GMAW is an arc welding process that uses an arc between a continuous wire electrode and the weld pool. GTAW uses an non-consumable electrode, tungsten, to produce the weld

What causes a bead to overlap the base metal?

Welding current being too low (base metal not getting enough heat)

How is it possible to determine if the gas flow is proper for shielding?

It is determined by the type of welding gun, weld joint design, base metal, type of metal transfer, and conditions in the weld area. For example, welding outdoors in breezy conditions requires higher shielding-gas flow rates to provide adequate coverage than when welding indoors

Why are smaller diameter electrodes used for overhead welding?

Larger electrodes make it too difficult to control the deposited metal

What are some of the requirements of a good electrode holder?

Lightweight, well insulated, heat resistant, balanced, and hold an electrode securely

What should be done when the crater gets too hot and the metal has a tendency to run over the surface?

Make sure the current is not set too low, and the correct electrode angle is being used

If the metal does not melt readily, what is the probable cause?

Metal might require preheating, torch may be at an incorrect welding angle, or filler rod may be too large.

When should a double fillet weld be used on a T-joint?

Might help when a t-joint is being used on a structure that will be subjected to heavy stresses from the opposite side of the welded joint.

In what type of joints are groove welds made?

Most commonly the butt joint

When is a butt joint used in welding?

Most suitable for welding steel that generally does not exceed 3/16" thick. It can be used on thicker metal, but only if the welding machine has enough current capacity and if larger diameter electrodes are used

What safety devices are used to prevent cylinders from exploding when subjected to intense pressure?

Oxygen cylinders have a special safety nut that permits the oxygen to drain slowly if the internal pressure exceeds a safe level. Acetylene cylinders have a fusible plug that will melt if in a fire or be pushed out if subjected to too high an internal pressure.

Why is oxygen generally a harmful element in welding?

Oxygen is a highly reactive gas and readily combines with other elements in molten metal to form oxides and gases which can cause porosity and other problems that affect the mechanical properties of the metal

Why is it dangerous to allow grease or oil to come in contact with the oxygen cylinder valve?

Oxygen strongly supports combustion if exposed to flammable materials such as grease or oil.

Why should the cylinder outlet nozzles be examined closely?

Particles of dirt can collect in the outlet nozzle of the cylinder valve. If not cleanout, the dirt can work into the regulator when the pressure is turned on.

Why are low-hydrogen electrodes used?

Prevent the introduction of hydrogen into the weld and heat affected zone

Why should the adjusting screw on a regulator be fully released before opening a cylinder valve?

Prevents damage to the regulator diaphragm

Why are the oxygen and acetylene hose fittings made with different screw threads?

So they don't become misconnected

How should an electrode be restarted to fill a crater left from a previously deposited weld?

Strike the arc approximately ½" in front of the crater, maintain a slightly longer arc, and move the electrode back through the crater retracing it with the arc

What are some of the characteristics of a weld made with an arc that is too short?

The bead is high & uneven with irregular ripples

What determines the rate at which the wire feed should be set?

The current that is to be used for welding

How is it possible to identify a weld that has been made with an arc that is too long?

The electrode melts off in large globules that wobble from side to side that end up producing wide, irregular beads with excessive spatter

What is voltage?

The electromotive force, or "pressure," that causes current to flow in an electrical circuit

Why is it a poor practice to light a torch with a match?

The flame produced by acetylene can cause serious burns.

What determines the size of the rod that should be used?

The rod should have the same diameter as the thickness of the base metal

What governs the size of the tip which should be used?

The size of the welding tip used depends on the thickness of metal to be welded.

Why are grooved butt joints usually superior to square butt joints for welding thick plates?

The square butt joint is used primarily for metals that are smaller in thickness. The joint is reasonably strong, but not recommended when the metals are subject to fatigue or impact loads. When welding metals with larger thicknesses, it is often preferred or necessary to se a grooved butt joint as it would give the joint the required strength.

What do we mean when we speak of the toes of a weld?

The toes of a weld are essentially the edges or points of the hypotenuse that is made by the weld geometry

Why should the torch be raised when it nears the end of the weld?

The torch should be raised near the end of the weld in order to reduce heat applied on the edge and prevent a concave puddle to form.

What is meant by the root of a weld?

The weld root is the point at which the back of a weld intersects with the base metal surfaces

Why is a filler rod used in welding?

To add strength to the joint.

What is the purpose of a root pass?

To join two members and fill the root opening - serves as the base for subsequent welds and typically must produce full joint penetration

When is a surfacing weld used?

To modify the properties of selected surfaces of a single component, such as an extruder

Why is correct wire stickout important?

To prevent damage to the end of the welding gun nozzle

Why are check valves used?

To prevent the reverse flow of gases that would result in a combustible mixture in the welding hose

When is argon or a mixture of argon and oxygen considered to be the ideal gas for shielding purposes?

When compensation is made for their oxidizing tendencies. All shielding gases should be welding grade (over 99% pure) and they provide the best protection and produce the best results

Why does nitrogen cause the most serious problems in welding?

When molten weld pool is exposed to nitrogen it forms nitrides as it cools, which increase hardness and decrease ductility and impact resistance. Loss of ductility often leads to cracking in the weld

When should the edges of butt joints be beveled?

When the metal is 3/16" thick or more

When is a whipping motion used?

When welders want to control the temperature of the molten weld pool - the electrode is struck and held momentarily, then moved forward about 1/4" & just as the weld pool begins to freeze, the electrode is moved back into the center of the weld pool and the sequence is repeated.

When is carbon dioxide better for shielding purposes than an inert gas?

When welding mild steel as long as the welding wire has deoxidizing elements that readily combine with oxygen and prevent the CO2 gas from causing porosity.

When should a multiple pass be used on a lap joint?

With members of 3/8" thickness or more that require an exceptionally strong joint

What are some of the specific advantages of gas metal-arc welding?

a wire feeder

What factors should be taken into consideration when selecting an electrode?

a. Base metal properties b. Electrode diameter c. Joint design & fit-up d. Welding position e. Service conditions f. Welding current & polarity g. Production efficiency

What equipment checks are made before proceeding to weld?

a. Check electrical connections for dryness, cleanliness, and security b. Check welding cables for any damages to the insulation and fix accordingly c. Verify that base metal is dry and free from all contaminants d. Set current to the suggested setting for the electrode diameter and welding position

What are the functions of the heavy coating on shielded electrodes?

a. Cleaning and deoxidizing agent to remove impurities and oxygen from the molten weld pool b. Permits better penetration and helps meet weld quality requirements c. Provides easier arc starting, arc stabilization & reduces spatter d. Forms a slag coating over the weld bead to protect it from elements in the atmosphere e. Produces a shielding gas to prevent the molten weld pool from reaching with elements in the atmosphere

What are some of the specific characteristics of fast-freeze electrodes?

a. Deep penetration b. Low deposition rate c. Crisp arc d. Rapidly solidifying weld bead

What are some of the signs of correct filler rod selection?

a. Leaves a smooth surface b. Flows smoothly c. Has minimal sparking when uniting the base metal

What is meant by open-circuit voltage and arc voltage?

a. Open-circuit voltage is the voltage at the terminals of power source when the machine is turned "on" but no welding current is flowing b. Arc voltage is the voltage from the bottom of the arc

What are some of the conditions that may cause a backfire?

a. Overheating the welding tip b. Obstruction in the welding tip c. Operating at too low of a pressure for the welding tip being used d. Touching the welding tip against the work

Some electrodes are classified as fill-freeze. What does this mean?

a. Shallow to medium penetration b. High deposition rate c. Moderately forceful smooth arc with low spatter d. Fluid weld pool

What are some of the factors that must be considered in the type of joint that should be used in welding any structural unit?

a. The type and thickness of the material to be welded b. Whether the load will encounter tension, compression, bending fatigue, or impact stresses c. How the load is to be applied to the joint d. The displacement of the load in relation to the joint e. The direction from which the load is to be applied to the joint f. Whether the joint can be welded from both sides or just one g. The cost of preparing the joint

What is likely to happen if cable connections are loose?

any exposed cable strands are live and conductive when welding which is a huge safety concern

What are the five essentials for securing a sound weld?

correct electrode selection, arc length, current, travel speed, electrode angle