Engineering, Materials And Components Quiz

When metals solidify, the atoms lose their mobility and assume fixed positions in the space lattice of the unit cell. This means that the atoms become locked into a specific arrangement within the crystal structure. As the metal cools and solidifies, the atoms slow down and eventually come to a stop, settling into their designated positions. This fixed arrangement is what gives metals their characteristic crystalline structure.

When a metal is folded in a thin plate on the surface of a forging, it can cause a lap. A lap is a defect that occurs when the metal folds over itself during the forging process, creating a thin layer of metal that is not properly bonded. This can weaken the structure of the metal and reduce its overall strength and integrity. Laps are undesirable because they can lead to failure or breakage of the forged part under stress or load.

Lack of penetration refers to a welding defect where the weld does not fully penetrate the base metal, resulting in an incomplete bond. This defect occurs at the root of the weld and runs parallel to it. It can weaken the joint and compromise its structural integrity.

Cold shuts are most likely found in castings. Cold shuts occur when two portions of molten metal fail to fully fuse together during the casting process, resulting in a visible line or seam in the final product. This defect is more commonly observed in castings because the molten metal has a higher likelihood of solidifying before complete fusion can occur. In contrast, extrusions, forgings, and sintered parts involve different manufacturing processes that are less prone to cold shut defects.

In gas welding, acetylene is typically burned with oxygen. This is because acetylene requires oxygen to support combustion and produce a high-temperature flame necessary for welding. Oxygen acts as the oxidizer, reacting with acetylene to generate heat and create a stable flame. Hydrogen, argon, and nitrogen are not commonly used as the primary gas for burning acetylene in gas welding processes.

Wooden patterns used in casting can be made in one, two, or more pieces depending on the complexity of the casting. The number of pieces required for the pattern is determined by factors such as the shape, size, and intricacy of the final casting. For simpler castings, a single-piece pattern may be sufficient. However, for more complex castings, a pattern may need to be made in multiple pieces to ensure accurate and precise molding. Therefore, the number of pieces for wooden patterns can vary based on the complexity of the casting being produced.

A chill is a metal insert that is placed in a sand mold to increase the cooling rate at a specific point. It helps to rapidly cool and solidify the metal in that area, preventing defects such as shrinkage or porosity. Chills are commonly used in foundry processes to control the solidification and cooling of the metal, ensuring a uniform and high-quality final product.

Heat exchanger tubes are prone to defects in regions adjacent to support plates, under support plates, and in between support plates. Support plates are used to hold the tubes in place, and due to the stress and pressure exerted on the tubes in these areas, they are more likely to develop defects. This can include cracks, leaks, or corrosion. Therefore, all of the mentioned regions are susceptible to defects in heat exchanger tubes.

Non-metallic inclusions are present before the billet is worked. During the manufacturing process of a billet, non-metallic inclusions such as oxides, sulfides, and silicates can form due to impurities in the raw materials or reactions with the surrounding environment. These inclusions can negatively impact the mechanical properties and quality of the final product. Therefore, it is important to control and minimize the presence of non-metallic inclusions through proper refining and processing techniques.

Hot working an ingot involves subjecting it to high temperatures and mechanical deformation, such as rolling or forging, to shape it into a desired product. The process of hot working can lead to changes in the microstructure of the material, which may result in the formation of new defects or the elimination of existing defects. Therefore, depending on the specific circumstances, hot working can either reduce the number of defects in the original ingot, introduce more defects, or maintain the same number of defects in the final product.

Gas tungsten-arc welding is the correct answer because in this process, the electrode is made of tungsten which is non-consumable. The tungsten electrode creates an arc with the workpiece, and the heat generated melts the base metal to form the weld. Since the electrode is not consumed during the welding process, it remains intact and does not need to be replaced, making it non-consumable.

The bottom portion of a molding flask is called a "drag". In foundry casting, a molding flask is a container used to hold the sand mold. The drag is the lower half of the flask, and it is filled with sand to create the bottom part of the mold. The cope, on the other hand, refers to the upper half of the flask, which is filled with sand to create the top part of the mold. The cheek and separator are not commonly used terms in the context of molding flasks.

A chaplet is a metal support used to hold cores in place within a sand mold. It is designed to prevent the core from shifting or moving during the casting process. Chaplets are typically made of a material that can withstand the high temperatures of the molten metal. They are placed between the core and the mold cavity to provide support and stability.

Pressure welding does not involve melting of the parts to be joined. In this process, the parts are joined together by applying pressure, without the need for melting. This can be achieved through various methods such as friction, ultrasonic vibrations, or explosives. Pressure welding is commonly used for joining materials that are difficult to melt or materials that have different melting points.

Oxides in weldments can create discontinuities that are similar to non-metallic inclusions. These discontinuities are known as slag inclusions. Slag inclusions occur when molten slag becomes trapped in the weld metal during the welding process. Slag is a byproduct of the welding flux and can cause defects in the weld if not properly removed. These defects can weaken the weld and compromise its integrity. Therefore, it is important to ensure proper removal of slag to prevent slag inclusions in weldments.

Lack of penetration is a weld discontinuity that occurs when the weld metal does not fully penetrate the joint. This means that the weld does not reach the root of the joint, resulting in a weak and incomplete bond. Lack of penetration can lead to structural integrity issues and reduced strength in the welded joint. It is important to ensure proper penetration during welding to avoid this discontinuity.

In the production of a casting, the first step is the making of a pattern. A pattern is a replica or model of the desired object, typically made from wood, plastic, or metal. It is used to create the mold into which the molten material will be poured to form the final casting. The pattern is designed to have the exact shape, dimensions, and surface finish of the desired casting, and it serves as a guide for creating the mold. Without a pattern, it would be impossible to create an accurate and consistent casting.

The correct answer is "Through the length of the bar." Steel bar stock typically exhibits a grain direction that runs parallel to the length of the bar. This is due to the manufacturing process, where the steel is rolled or extruded into its final shape. The grain structure aligns along the length of the bar, which can affect the mechanical properties and performance of the steel in certain applications.

A chaplet is a type of casting insert that is used to support or hold a core in place during the casting process. It is typically made of metal and is placed between the mold and the core to provide support and prevent distortion or movement. Chaplets are commonly used in sand casting and other casting processes to ensure the integrity and accuracy of the final casting.

Permanent mold casting and die casting differ in terms of how the molten metal enters the mold. In permanent mold casting, the molten metal enters the mold by gravity, meaning it simply flows into the mold due to its own weight. On the other hand, in die casting, the molten metal enters the mold under pressure. This means that force is applied to inject the metal into the mold, resulting in a more controlled and precise filling of the mold cavity.

When thick and thin casting sections are adjacent to each other, a potential discontinuity that may result is shrinkage. Shrinkage occurs when there is a difference in cooling rates between the thick and thin sections, causing the metal to contract at different rates. This can lead to internal voids or defects in the casting, compromising its structural integrity. Shrinkage is a common issue in casting processes and needs to be carefully managed to ensure high-quality castings.

Premature blocking of a gate during the pouring of a casting can cause microshrinkage. Microshrinkage refers to the formation of small voids or shrinkage cavities in the casting due to the inadequate supply of molten metal. When the gate is blocked too early, it restricts the flow of molten metal into the mold cavity, leading to insufficient filling and solidification. This can result in the formation of tiny voids within the casting, causing microshrinkage defects.

In the submerged arc welding process, flux is added separately and heaped along the joint to be welded. Flux is a material that is used to protect the weld from atmospheric contamination and to facilitate the welding process. By adding the flux separately and heaping it along the joint, it ensures that the weld is protected from any impurities in the atmosphere and that the welding process can occur smoothly. This method allows for better control and coverage of the weld, resulting in a stronger and more reliable joint.

Micro shrinkage is a defect that can occur during the casting process. It happens when there is insufficient molten metal to fill the entire mold, resulting in small voids or shrinkage cavities in the casting. These shrinkage defects are more likely to occur at junctions between light and heavy sections of the casting. This is because the heavier sections require more molten metal to fill them, leaving less material available for the lighter sections. Consequently, the junctions between these sections may not be completely filled, leading to micro shrinkage defects.

Extrusion is the process used to produce seamless tubing. This process involves forcing a metal billet through a die, resulting in a tube with a consistent diameter and thickness. Unlike other methods mentioned, extrusion does not require welding or the use of filler metal, making it a preferred method for producing seamless tubing.

In the resistance welding process, the correct answer states that the pieces to be joined are held firmly together under pressure, followed by the generation of heat at the interface. This is the accurate explanation of the resistance welding process. The pressure applied helps to ensure that the pieces are securely held together, and the generation of heat at the interface allows for the welding of the two parts. This process does not involve melting the parts or adding a filler metal, but rather relies on the application of pressure and heat to create a strong weld.

During on-line manufacturing inspection of components, it is common to automatically mark defective areas for two main purposes. Firstly, marking the defects allows for their removal after the inspection if desired. This ensures that the final product is of high quality and free from any defects. Secondly, marking the defects also allows for destructive examination of those areas after the inspection if desired. This can help in identifying the root cause of the defects, improving the manufacturing process, and preventing similar issues in the future. Therefore, the correct answer is "Both a and b."

Unequal heating or cooling of the material can cause heat treat cracks. When there is a significant difference in temperature between different parts of the material during the heat treatment process, it can lead to thermal stress and differential expansion or contraction. This can result in the formation of cracks in the material. It is important to ensure proper and uniform heating and cooling to prevent these cracks from occurring.

When a pouring gate in a casting blocks off prematurely, it can cause the metal to shrink before it completely fills the mold cavity. This shrinkage can result in the formation of many small, subsurface holes in the casting, which is known as microshrinkage.

Most manufacturing defects in a tube are axial in direction. This means that the defects occur along the length of the tube, parallel to its axis. Axial defects can include cracks, splits, or deformations that run along the tube's length. These defects are typically caused by issues during the manufacturing process, such as improper heat treatment or insufficient material quality control. Axial defects can have a significant impact on the structural integrity and performance of the tube, making them a critical concern in manufacturing and quality control processes.

When a metal is stressed below its elastic limit, it means that the applied stress does not exceed the maximum stress the metal can handle without permanent deformation. Therefore, once the stress is removed, the metal will be able to return to its original shape because it has not undergone any permanent changes in its structure. Heating the metal to its curie point or applying an equivalent stress in the opposite direction are not necessary for the metal to return to its original shape.

The Curie point refers to the temperature above which the steel is no longer magnetic. At this temperature, the steel undergoes a phase transition and loses its magnetic properties. This phenomenon is named after Pierre Curie, a French physicist who discovered it in the late 19th century.

The correct answer is "All of the above". Inserts such as chills, chaplets, and cores can be found in sand molds. Chills are used to control the solidification rate of the metal, chaplets are used to support cores in the mold, and cores are used to create internal cavities in the casting. Therefore, all of these inserts are commonly used in sand molds.

A forging lap may occur if faulty dies are used for forging, as they can cause irregularities in the shape of the metal. Additionally, if the metal is either too hot or too cold during the forging operation, it can lead to a forging lap. The temperature of the metal is crucial for proper forging. Lastly, if the metal is forced to flow too fast, it can cause excessive strain on the material and result in a forging lap. Therefore, all of the mentioned factors can contribute to the occurrence of a forging lap.

Brazing is a joining process that occurs without fusion of the base metal. In brazing, a filler metal is heated above its melting point and distributed between two or more close-fitting parts. The filler metal then solidifies to form a strong bond between the parts. Unlike welding, where the base metal itself is melted, brazing only melts the filler metal, allowing for joining of dissimilar metals or delicate parts that cannot withstand the high temperatures of welding. Therefore, brazing is the correct answer as it involves joining without fusion of the base metal.

Undercutting is a defect that occurs when the sidewalls of the welding groove melt away at the edge of a layer of weld metal and runs parallel to the weld bead. This defect is characterized by a groove or depression in the base metal adjacent to the weld. It is caused by excessive heat or improper welding technique, leading to the erosion of the base metal. Undercutting weakens the weld joint and can result in structural failure or leakage.

Grinding cracks are usually caused by grinding hard metal surfaces. When hard metals are being ground, the high pressure and friction generated can cause the metal to become overheated and brittle, leading to cracks. Soft metal surfaces are less likely to cause grinding cracks as they are more malleable and can withstand the grinding process better. Heat treatment may affect the hardness of the metal but is not directly responsible for grinding cracks. Similarly, too slow feeding rates may result in inefficient grinding but are not the primary cause of grinding cracks.

Forging laps can occur where the dies come together. When the dies close during the forging process, there can be a misalignment or inadequate pressure at the point where they meet, leading to a lap. This can result in a defect in the forged part, causing a weak spot or a seam. Therefore, it is important to ensure proper alignment and pressure at the point where the dies come together to avoid forging laps.

Brazing is a joining method where flaws, when they occur, are essentially two-dimensional. In brazing, a filler metal is melted and flowed into the joint, creating a strong bond between the base metals. The filler metal has a lower melting point than the base metals, allowing it to flow and fill the joint. Flaws in brazing typically occur in the form of surface defects, such as cracks or voids, which are two-dimensional in nature. This is in contrast to the other joining methods mentioned, such as gas tungsten arc welding, gas metal arc welding, and submerged arc welding, where flaws can occur in three dimensions.

Investment casting allows for the production of more complex shapes compared to green sand casting. This is because investment casting uses a wax pattern that can be intricately designed and then coated in a ceramic shell, which allows for greater detail and precision in the final casting. Green sand casting, on the other hand, uses a mold made of sand, which may not be able to accurately reproduce complex shapes. Therefore, investment casting is advantageous when it comes to creating intricate and complex parts.

A reducing flame is produced when there is excess acetylene in the flame. In gas welding, a reducing flame is used to protect the metal from oxidation by limiting the amount of oxygen available. This helps prevent the metal from becoming brittle and allows for a cleaner weld. Excess acetylene in the flame creates a fuel-rich environment, reducing the amount of oxygen and promoting a reducing flame.

Martensite is the hardest structure that can be produced by heat treating steel. It is formed when austenite is rapidly cooled, causing a transformation from a face-centered cubic (FCC) structure to a body-centered tetragonal (BCT) structure. This rapid cooling prevents the carbon atoms from diffusing and forming other structures, resulting in a highly distorted and hard material. Martensite is known for its high strength and hardness, making it desirable for applications that require toughness and wear resistance.

A cold shut refers to a type of defect that occurs during the casting process. It happens when two streams of molten metal do not properly fuse together, resulting in a seam or line in the final product. This seam appears smooth and curved, which distinguishes it from other types of defects such as a ragged shape, a straight thin line, or an undulating shape.

In a rolling mill, flattening and elongation of metal is primarily accomplished by applying compressive stresses. This is because the metal is passed through a series of rollers that exert pressure on it, causing it to deform and elongate. The compressive stresses help to reduce the thickness of the metal and increase its length. Tensile stresses, bending stresses, and high frequency cyclical loads may also play a role in the process, but the primary mechanism for flattening and elongation is the application of compressive stresses.

The middle portion of a molding flask is called a cheek. The cheek is the section of the flask that separates the cope (top) and drag (bottom) portions. It provides support and stability to the mold during the casting process. The cheek is typically made of a sturdy material such as metal or wood to withstand the pressure and heat of the molten metal.

The work metal for working with a forging hammer can be any of the above options mentioned, which are a bloom, a billet, or a bar. This means that all three forms of metal can be used as the workpiece when using a forging hammer. The choice of which form to use would depend on the specific requirements of the forging process and the desired outcome.

The correct answer is "All of the above" because all three materials - Nickel, Cobalt, and Iron - are considered to be ferromagnetic. Ferromagnetic materials are those that can be magnetized and retain their magnetization even after the external magnetic field is removed. These materials have strong magnetic properties due to the alignment of their atomic magnetic moments. Nickel, Cobalt, and Iron are commonly used in various applications that require magnetic properties, such as in the production of magnets and magnetic storage devices.

Investment casting is the most suitable method for processing aircraft turbine blades because it allows for the production of complex shapes with high dimensional accuracy and a smooth surface finish. This process involves creating a wax pattern of the desired blade shape, which is then coated with a ceramic material. The ceramic shell is heated to remove the wax, leaving behind a hollow mold. Molten metal is then poured into the mold, filling the cavity and solidifying to form the turbine blade. This method ensures the blades have the necessary strength, durability, and aerodynamic efficiency required for their function in an aircraft engine.

The correct answer is "The upper die only" because in the forging process, the upper die is responsible for delivering the striking force onto the work metal. The upper die is usually attached to a mechanical or hydraulic system that provides the necessary force to shape the metal. The lower die, on the other hand, acts as a support or guide for the metal and does not impose any striking force. Therefore, the correct answer is that the striking force is imposed on the work metal by the upper die only.

Allotropy is the property of a material to exist under different lattice structures at different temperatures. This means that the material can have different crystal structures depending on the temperature. This phenomenon is commonly observed in elements such as carbon (diamond and graphite) and oxygen (oxygen gas and ozone). Ductility refers to the ability of a material to be stretched without breaking, crystallinity refers to the regular arrangement of atoms in a material, and hardenability refers to the ability of a material to be hardened by heat treatment.

In gas metal-arc welding, a stream of protective gas is passed through an inverted cup or a nozzle which surrounds the electrode. This is different from shielded metal-arc welding where the shielding gas is contained in the flux covering the electrode. The passing of protective gas through a cup or nozzle helps to protect the weld from atmospheric contamination and ensures a clean and strong weld.

Excessive working of the metal during the forging or extruding operation can cause a burst. This means that when the metal is being shaped or formed, if too much force or pressure is applied, it can lead to the metal becoming weak and eventually bursting. This can happen due to the metal being overworked or stretched beyond its limits, resulting in a processing defect known as a burst.

A reducing flame is produced when there is excess acetylene in the flame. This means that there is more acetylene than the necessary amount to completely burn with the available oxygen. The excess acetylene creates a flame with a fuel-rich mixture, resulting in a reducing atmosphere where oxygen is limited. This type of flame is commonly used in gas welding as it helps prevent oxidation and promotes better control over the welding process.

Fine lines that occur in groups and are caused by non-metallic impurities present in the original ingot and extruded lengthwise are known as stringers.

Metals that recrystallize at room temperature cannot be work hardened because work hardening is a process that involves deforming the metal's crystal structure. When a metal is work hardened, dislocations and defects are introduced into the crystal lattice, making it harder and stronger. However, if the metal has the ability to recrystallize at room temperature, it means that the crystal structure can recover and rearrange itself, eliminating the dislocations and defects caused by work hardening. Therefore, these metals cannot retain the increased hardness and strength obtained through work hardening.

Slugging is not normally found in a casting. Misrun refers to a defect where the molten metal does not completely fill the mold cavity. Porosity refers to the presence of small voids or gas pockets in the casting. Shrinkage is a defect caused by the solidification and cooling of the metal, resulting in a reduction in size. However, slugging is not a common discontinuity in castings and is not typically associated with casting defects.

Forging is the correct answer because it is a forming operation that involves shaping the material by applying compressive forces. The process of forging involves heating the material and then applying pressure to shape it into the desired form. This method allows for precise control over the dimensions and results in a high level of dimensional accuracy. Cold rolling of sheet, hot rolling of sheet, and cold rolling of bars may also result in dimensional accuracy, but forging is known to provide the greatest level of accuracy.

Materials of low ductility, which are less likely to deform under pressure, are best forged using hydraulic presses. Hydraulic presses provide a controlled and gradual application of force, allowing for precise shaping of the material without causing excessive deformation or cracking. The gradual application of pressure also helps to minimize the risk of material failure. On the other hand, gravity drop hammers, power drop hammers, and high energy rate forging hammers deliver a sudden and intense impact, which may not be suitable for materials with low ductility.

A fatigue crack is caused by cyclic loading of the part below the yield strength of the material. When a material is subjected to repeated loading and unloading, stresses are generated within the material. If these stresses are below the yield strength of the material, they can cause the formation and propagation of cracks over time. This is known as fatigue failure. Cyclic loading above the yield strength can cause plastic deformation and yield, but it is not the main cause of fatigue cracks. Local overheating and corrosive atmosphere can lead to other types of damage, but they are not specifically related to fatigue cracks.

Fine lines that occur in groups and are caused by non-metallic impurities present in the original ingot and extruded lengthwise are called stringers. These stringers can weaken the material and affect its overall integrity.

A hot tear, also known as a hot crack or solidification crack, is a type of defect that propagates along grain boundaries in metals and alloys during solidification or cooling. These cracks occur due to the inability of the material to compensate for the stresses induced by thermal contraction and shrinkage during the cooling process.

As cold working progresses, the energy required for further processing increases. This is because cold working involves deforming the material at room temperature, which causes strain hardening. Strain hardening increases the strength and hardness of the material but also makes it more difficult to further process or deform. Therefore, more energy is needed to continue working or processing the material as cold working progresses.

Copper, steel, and aluminum are all examples of crystalline materials, not amorphous materials. Amorphous materials lack a regular, ordered atomic structure and instead have a disordered arrangement of atoms. Examples of amorphous materials include glass, rubber, and some plastics.

Cropping is a method commonly used to remove a number of flaws in an ingot prior to forming. This process involves cutting off the defective or unwanted parts of the ingot, such as cracks, impurities, or uneven surfaces. By removing these flaws, cropping helps to improve the overall quality and integrity of the ingot, making it more suitable for further processing and forming into desired shapes or products. Heat treating, welding, and sand blasting are not typically used for removing flaws in ingots.

Forging is the millworking process used most to form metals into 3D shapes. It involves the application of compressive forces to shape the metal by heating it to a high temperature and then hammering or pressing it into the desired shape. This process allows for the creation of complex and strong metal components, making it a commonly used method in industries such as automotive, aerospace, and manufacturing. Casting involves pouring molten metal into a mold, cold rolling is a process for shaping metal sheets, and welding involves joining metal pieces together, but they are not as commonly used for forming 3D shapes as forging.

Seams are not sub-surface discontinuities. Seams are actually visible lines or ridges that occur when two pieces of material are stitched or joined together. They are typically found in fabrics or other materials that have been sewn or fused together. Unlike sub-surface discontinuities, seams can be seen and felt on the surface of the material. Therefore, the correct answer is False.

Resistance welding differs from fusion welding because it requires the use of pressure. In resistance welding, the two metal pieces to be joined are pressed together under pressure while an electric current is passed through them. This pressure is essential to create a strong bond between the metals. In fusion welding, on the other hand, the metals are melted and fused together without the need for pressure.

Full annealing is the correct answer because it involves heating the steel above its upper critical temperature to transform it into austenite, and then slowly cooling it through the transformation range. This process helps to refine the grain structure of the steel, relieve internal stresses, and improve its mechanical properties. Tempering involves heating the steel to a lower temperature to reduce its hardness, while normalizing involves cooling the steel in still air after heating it above its upper critical temperature. Quenching involves rapidly cooling the steel to increase its hardness.

Investment casting is a casting process in which a pattern is created from wax or a similar material, and then coated with a ceramic material. The ceramic shell is then heated to remove the wax, leaving behind a hollow cavity in the shape of the desired part. Molten metal is then poured into the cavity, creating the final casting. Unlike other casting processes, investment casting does not involve the use of a reusable pattern. Instead, each pattern is destroyed in the process, making it a non-reusable casting method.

A heat treat crack is a rupture or crack that occurs in a material due to localized stresses that exceed the material's tensile strength, often as a result of the heat treatment process. This process involves heating and cooling metal to alter its physical properties, which can sometimes introduce residual stresses or uneven cooling. If these stresses exceed the tensile strength, cracks may form, potentially in any direction. Heat treat cracks can compromise the integrity and durability of a part, and their formation might require adjustments to heat treatment methods or improved stress-relief processes to prevent reoccurrence. User

Intergranular corrosion is the correct answer because it is a service defect that manifests as small micro-openings that do not follow a specific pattern and extend in any direction along the grain boundaries. This type of corrosion occurs due to the preferential attack of the grain boundaries by corrosive agents, leading to the formation of cracks and pits. It is different from fatigue cracks, fillet cracks, and hydrogen embrittlement, which have distinct characteristics and causes.

Using a welding rod that is too large can result in a lack of penetration. When the welding rod is too large, it requires more heat to melt and fuse the metal together. This can cause the welding current to be spread out over a larger area, resulting in insufficient heat concentration at the joint. As a result, the metal may not fully melt and penetrate, leading to a weak and incomplete weld. To ensure proper penetration, it is important to use a welding rod that is appropriate for the thickness and type of metal being welded.

In forgings, the grain follows the shape of the dies. This means that during the forging process, the metal is deformed and shaped according to the shape of the dies. As a result, the grains within the metal also align and follow the same shape. This is important because it helps to improve the mechanical properties of the forgings, such as strength and durability. By aligning the grains, the metal becomes more uniform and less prone to defects or weaknesses. Therefore, it is crucial for the grain to follow the shape of the dies in order to produce high-quality forgings.

Grinding cracks occur crosswise to grinding wheel rotation because the grinding process generates high heat and stress on the workpiece. As the grinding wheel rotates, it applies pressure and friction on the workpiece, causing it to heat up and expand. This expansion, combined with the stress from the grinding process, can result in cracks forming in a crosswise direction to the rotation of the grinding wheel. Therefore, the statement is true.

Non-metallic inclusions are a type of discontinuity found in ingots. These inclusions are foreign substances that are trapped within the metal during the solidification process. They can be in the form of oxides, sulfides, or other impurities that are not part of the desired composition of the ingot. Non-metallic inclusions can have detrimental effects on the mechanical properties of the metal, such as reducing its strength and ductility. Therefore, they are considered a type of defect or discontinuity that needs to be minimized or eliminated during the ingot production process.

A burst is a processing discontinuity.

A cold shut is a generally smooth indication on a cast surface that occurs when two streams of metal, coming from different directions, fail to fuse together. This can happen due to improper pouring or inadequate fluidity of the metal. As a result, a visible line or seam forms on the cast surface, indicating the incomplete fusion.

Continuous casting is a metal production process that eliminates the need for ingot cropping. In this process, molten metal is poured into a water-cooled mold, which solidifies the metal into a continuous form. The solidified metal is then continuously pulled out of the mold, creating a long strand or slab. This eliminates the need for traditional ingot cropping, where the ends of the ingot are cut off to remove any impurities or unevenness. Continuous casting allows for a more efficient and cost-effective production process, as it reduces waste and provides a continuous supply of metal.

Bursts in metal can be caused by working at extreme temperatures, either too low or too high. When the temperature is too low, the metal becomes brittle and prone to cracking under stress. On the other hand, when the temperature is too high, the metal can become overheated and lose its structural integrity, leading to bursting. Therefore, it is important to work within the appropriate temperature range to avoid bursts in metal.

Laminations are produced when a pipe or blisters present in the original ingot are made directional by rolling. This means that during the rolling process, the pipe or blisters in the ingot are elongated in a specific direction, resulting in the formation of laminations.

The presence of several sprues or gates in the mold can be one of the main causes of cold shuts. When there are multiple sprues or gates in the mold, it can lead to uneven filling of the molten metal, causing the metal to solidify before it completely fills the mold cavity. This results in incomplete fusion of the metal, leading to cold shuts. Cold shuts are defects where two streams of molten metal fail to fuse together properly, resulting in a visible line or seam in the final product.

Forging is a metal forming operation that allows three-dimensional control over the shape of the product. It involves heating the metal and then applying compressive forces to shape it into the desired form. This process allows for precise control over the dimensions and contours of the final product, making it an ideal choice when three-dimensional control is required. Rolling and extruding are also metal forming operations, but they do not offer the same level of control over the shape as forging does.

As cold working progresses, the energy required for further processing increases. This is because cold working involves deforming the material at room temperature, which causes strain hardening. Strain hardening increases the strength and hardness of the material, but it also makes it more difficult to further deform the material. Therefore, as cold working progresses, more energy is needed to continue processing the material.

Intergranular corrosion is the correct answer because it is a service defect that appears as small micro-openings following the grain boundaries. These openings do not have a definite pattern and can extend in any direction. This type of corrosion occurs at the grain boundaries due to chemical reactions, causing the material to weaken and deteriorate. Fatigue crack, fillet crack, and hydrogen embrittlement do not exhibit the same characteristics as described in the question.

Submerged arc welding (SAW) is a limited-position welding process. The welding positions are limited because the large pool of molten metal and the slag are very fluid and will tend to run out of the joint. Welding can be done in the flat position and in the horizontal fillet position with ease. SAW is ideally suited for longitudinal and circumferential butt and fillet welds. However, because of the high fluidity of the weld pool, molten slag, and loose flux layer, welding is generally carried out on butt joints in the flat position and fillet joints in both the flat and horizontal-vertical positions.

Grinding involves the use of abrasives to remove material from a workpiece, resulting in a very fine surface finish. This process can achieve tight tolerances and smooth surface finishes, making it ideal for precision components where surface finish is critical.

The presence of several sprues or gates in the mold can cause cold shuts. When there are multiple sprues or gates, the flow of molten metal can be disrupted, leading to incomplete filling of the mold cavity. This can result in a lack of fusion between the metal streams, causing a cold shut. A cold shut is a defect where two metal streams do not fully merge, resulting in a visible line or seam in the final casting. Therefore, the presence of multiple sprues or gates increases the likelihood of cold shuts occurring.

Incomplete penetration refers to a welding defect where the weld does not fully penetrate the joint, resulting in a dark narrow line down the center of the weld. This occurs when the weld pool does not fully fuse with the base metal, leaving a gap. Incomplete penetration weakens the weld and reduces its integrity, making it more susceptible to failure under stress. It is important to ensure proper penetration during welding to maintain the strength and quality of the joint.

An ingot is a correct term for a steel casting suitable for working or remelting. It refers to a solid block of metal that is typically rectangular in shape and is produced by pouring molten metal into a mold to solidify. Ingots are commonly used in the steel industry for further processing and shaping into various products. They can be easily reheated and manipulated to meet specific requirements, making them suitable for working or remelting.

Porosity refers to the presence of small holes or voids in a material. In the context of ingots, porosity can occur during the solidification process when gases or impurities become trapped in the metal. This can result in weakened areas within the ingot, reducing its structural integrity. Therefore, porosity is a common defect that can be found in ingots.

High strength aluminum alloy (7075) is the most easily forgeable material among the given options. This is because aluminum alloys have a lower melting point and are more malleable compared to other metals like stainless steel, carbon steel, and nickel-based alloys. The 7075 alloy specifically is known for its high strength-to-weight ratio, making it desirable for applications requiring strength and lightness. However, this same characteristic also makes it easier to forge and shape compared to the other materials listed.

A common processing indication in rolled bar stock is a seam. A seam refers to a line or crack that is formed during the rolling process of the bar stock. It occurs when the edges of the metal sheet do not properly join together during the rolling process, resulting in a visible line or crack on the surface of the bar stock. This can affect the structural integrity and quality of the bar stock, making it an important consideration in the manufacturing and inspection processes.

Bursts are described as three-dimensional discontinuities with smooth internal surfaces that are typically situated near the surface of the wrought material. They appear as smooth indentations on metal surfaces and are cavities of varying sizes, usually parallel to the grain. Bursts are extremely thin and flat, aligning parallel to the work surface of the material.

Spot welding is a process in which two metal surfaces are joined together by applying pressure and heat. In this process, no filler metal is added because the heat generated by the electric current passing through the metal surfaces causes them to melt and fuse together. Therefore, spot welding does not require the use of filler metal.

The correct answer is "Feed the castings as the metal shrinks before and during solidification." A riser in the mold is designed to provide additional molten metal to compensate for the shrinkage that occurs during solidification. As the metal cools and solidifies, it contracts, which can lead to defects like shrinkage cavities. By having a riser, the extra molten metal can feed into the casting as it shrinks, ensuring that it fills any voids and prevents defects. The other options, letting air escape from the mold and ensuring impurities segregate outside the casting, are not the primary purpose of a riser.