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62 Cards in this Set

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  • Back

Define Wrought structure

Wrought Structure: During hot rolling, cast structure is converted to a wrought structure, which has finer grains and enhanced ductility.

Define bloom/slab

Bloom or slab: A bloom or a slab is product of first hot-rolling operation. A bloom has a square cross-section, and a slab is rectangular in cross-section. Blooms are processed further by shape rolling into structural shape, such as I-beams and railroad rails. Slabs are rolled into plates and sheets.

Define Billets

Billets are usually square shaped with a cross-sectional less than blooms. Billets are further rolled with shaped rolls into various shapes, such as round rods and bars.

Define Wavy edges

Wavy edges: Due to roll bending, the strip is thinner along its edges than at its center. Therefore, the edges elongates more than the center consequently the edges buckle because of constrained of the central region creating the wavy edges.

Define Alligatoring

Alligatoring is a complex phenomenon and is typically caused by nonuniform bulk deformation of the billet during rolling or by the presence of defects in the original cast material.

What is typically done to make sure that the product in flat rolling does not acquire a crown? What is thermal camber?

The usual method of avoiding crowning is to grind the rolls in such a way that their diameter at the center is slightly larger than at their edges (camber) Thermal camber is produced due to the heat generated due to the work in plastic deformation. The diameter of the roll is slightly increased in the center giving it a barrel shaped geometry. It can be corrected with proper cooling.

What is flattening of rolls? What is spreading?

Flattening: rolls force tending to flatten the rolls elastically. Spreading: With smaller width-to-thickness ratios, the widths of plates and sheets increase significantly as it passes through the rolls. This increase in width is called spreading.

What are 4 of the standard roll configurations? What are the advantages of the cluster-mill configuration? (4 points)

The 4 standard rolling configurations are two-high, three-high, four-high, and tandem. Cluster milling lowers roll forces and power requirements and reduces spreading. Moreover, when worn or broken, small rolls in cluster mills can be replaced at lower cost than can large ones.

Define Open-Die Forging

Open die forging is when the work piece is compressed between two flat dies. Also called upsetting or flat-die forging. Barreling can occur due to friction between the die face and the work piece. This can be reduced by lubrication. Barreling can also be caused by using hot work pieces and cold dies. This can be eliminated by using heated dies. Cogging is another type of open die forging. Where the thickness of a bar will be reduced by successive open die forging steps at specific intervals along the length of the bar.

Define Closed-Die Forging

In impression die forging and closed die forging the work piece is compressed between two shaped dies. In impression die forging, material flows outward and forms a flash. In closed die forging a flash is not formed. For this reason it is also called flash-less forging.

Why are most forging operations, particularly for large parts, carried out at elevated temperatures?

In order to enhance the ductility of the metals and lower the forces required.

What types of metals cannot be forged using hammers and presses?

High melting point metals, brittle metals, (and mercury). For very high melting point metals, it is difficult to find furnaces that can withstand extreme temperatures during a forging operation. Brittle materials, such as cast iron will crack if forged with hammers and presses. Also, mercury which is a liquid at room temperature cannot be forged with hammers and presses.

How do forged products compare to cast products?

Forged parts when subjected to a tension, will exhibit greater ductility and are generally tougher than cast parts. Depending on the type of processes and heat treatments used, forged parts will have smaller grain size. Contrarily, cast parts will be more isotropic than forged parts. For large quantities, forging is more economical. Sand casting is the more economical process for fewer than about 20,000 pieces

In edging during performing material is gathered into a localized area, while in fullering the material is distributed away from an area. (T/F)


In forging with hammers a gradual load is applied to the part while forging with presses exert impact loads. (T/F)


The velocity of the strip increases from its entry value as it moves through the roll gap, in flat rolling. (T/F)


A small draft is provided in sand-mold patterns to enable removal of the pattern without damaging the mold. (T/F)


In flat rolling, large-diameter rolls tend to deform the metal strip plastically more at its surfaces than in the bulk. (T/F)


The cost of making the mold cavities in sand casting is much higher than that in making mold cavities for die casting. (T/F)


Friction is necessary for rolling materials, but, energy is dissipated in overcoming friction. (T/F)


In flat rolling plates and sheets with very high width-to-thickness ratios, the width of the strip increases as a consequence of the reduction in thickness. (T/F)


A riser must not solidify before the casting. (T/F)


Hot rolling processes provide excellent tolerances and surface finish when compared against cold rolling processes. (T/F)


How do as-forged products compare to as-cast products in terms of structure and strength?

As forged products obtain a wrought structure, as opposed to as-cast products. The cast structure results in a coarse, equi-axed structure of medium to large grains if suitably inoculated. Otherwise, they have a mixture of equi-axed, columnar and chilled zones. The wrought structure is better processed, with finer grain size along preferred directions and enhanced ductility. The wrought structures are stronger as a result, even prior to heat treatment.

What are the advantages gained by using smaller rolls in flat rolling? What are 2 rolling configurations that best utilize the advantages of smaller rolls?

Smaller rolls have a smaller contact area with the strip. This results in lower friction and hence lower forces and power consumed. Also, lower rolls are cheaper to replace, if they are damaged during the process due to wear and tear. Four-high Mills and Cluster milling lowers roll forces and power requirements and reduces spreading. Moreover, when worn or broken, small rolls in cluster mills can be replaced at lower cost than can large ones

Why can’t lubrication be used in the coining process?

Lubrication cannot be applied because fluids or solids used in lubrication displace volume in the forged product. This is because these lubricants are not compressible.

What is crown in rolled plates? What is typically done to ensure that the product in flat rolling does not acquire a crown?

Due to roll bending, the rolled strip tends to be thicker at its center than at its edges. This is a crown on the strip. The usual method of avoiding crowning is to grind the rolls in such a way that their diameter at the center is slightly larger than at their edges. This is to say that the rolls are given a camber.

What is thermal camber?

Due to the heat generated by plastic deformation during rolling rolls can become slightly barrelshaped. Thus, they are said to have acquired a thermal camber.

What is flattening of rolls? What is side-spread or spreading?

Flattening: rolls forces tend to flatten the rolls elastically. Spreading or side-spread: With smaller width-to-thickness ratios, the widths of plates and sheets increase significantly as it passes through the rolls. This increase in width is called spreading.

Name three nonferrous casting alloys, which melt at low temperatures.

Three types of nonferrous casting alloys are Aluminum, Magnesium and Copper.

Define Upsetting Test

A solid, cylindrical specimen is upset between flat dies, and the reduction in height at which cracks on the barreled surface begin to develop is measure. The greater the deformation prior to cracking, the better the forgeability of the metal.

Define Hot-Twist Test

A round specimen is twisted continuously in the same direction until it fails. This test is performed on a number of specimens and at different temperatures, the number of complete turns that each specimen undergoes before failure at each temperature is then plotted. The temperature at which the maximum number of turns occurs becomes the forging temperature for maximum forgeability. The test has been found to be useful particularly for steels.

General requirements for die materials

-Strength and toughness, especially at elevated temperatures.

-Hardenability and ability to harden uniformly.

-Resistance to mechanical and thermal shock.

-Wear resistance, particularly resistance to abrasive wear, because of the presence of scale in hot forging.

Open Die Forging Advantages and Limitations


• Simple and inexpensive dies

• Wide range of part sizes

• Good strength


• Limited to simple shapes

• Difficult to hold close tolerances

• Machining necessary for final shape

• Low production rate

• Poor utilization of material

• High Degree of skill required

Closed Die Forging Advantages and Limitations


• Good material utilization

• Better properties than open-die forgings

• Good dimensional accuracy

• High production rates

• Good reproducibility


• High die cost

• Not economical for small quantities

• Machining often necessary

Precision Forging Advantages and Limitations


• Close dimensional tolerances

• Very thin webs and flanges possible

• Machining generally not necessary

• Very good material utilization


• High forging forces

• Intricate dies

• Provision for removing forging from dies.

Due to the heat generated by plastic deformation during rolling, rolls can become slightly barrel-shaped. (T/F)


As a result of roll bending, the rolled strip tends to be thicker at its center than its edges giving it a camber. (T/F)


Tolerances achieved in die casting is often better than what can be achieved with sand casting. (T/F)


The centrifugal casting process uses a polystyrene pattern which evaporates upon contact with molten metal to form a cavity for the casting. (T/F)


What is Investment casting? Is it an expendable mold type process? Discuss the tolerances achievable compared to sand casting. Discuss the economics.

The investment casting also called as lost-wax process is the process of making a wax pattern, loading with refractory slurry and melted out the wax and then used to make castings.

It is an expendable mold type process as the mold is broken to remove casting. Tolerances achieved are better (tighter control) than sand casting. It is an inexpensive process compared to die casting (set up/equipment cost of dies is very expensive).

What are the two types of die casting? Explain the differences.

- Hot-chamber die casting

- Cold-chamber die casting

Hot-chamber die casting requires lower pressure than in cold-chamber die casting because materials at lower temperatures need higher pressure to be forced into (and fill) the mold cavity. Hot-chamber die casting pressure ranges up to 35 MPa (5000 psi), while cold-chamber die casting pressure ranges from 70 MPa (10,000 psi) to 150 MPa (20,000 psi).

Two piece molds consist of a drag on top and a cope on bottom. (T/F)


The term "green" in green molding sand refers to the color of the sand used in molding. (T/F)


Flattening of rolls due to elastic deformation results in a smaller roll radius. (T/F)


The evaporative-pattern casting process uses a polystyrene pattern which evaporates upon contact with molten metal to form a cavity for the casting. (T/F)


Fine grained sand used to make molds enhances the mold strength but the fine grain also lowers mold permeability. (T/F)


What differences, if any, would you expect in the properties of castings made by permanent-mold versus sand-casting processes?

Examples of differences are that permanent-mold castings generally possess a better surface finish, closer dimensional tolerances, more uniform mechanical properties, and sounder thin-walled sections than sand castings. However, sand castings generally will be of more intricate shapes, larger overall sizes, and are lower in equipment cost than permanent-mold casting.

What are the important considerations when selecting pattern materials?

Size and shape of the casting, the dimensional accuracy and the quantity of castings required all should be considered. Strength and durability of the material selected for a pattern must reflect the number of castings that the mold will produce. Wear in critical regions should be reduced

What is the function of a core? What properties should cores have?

Cores are utilized for castings with internal cavities or passages. Cores are placed in the mold cavity to form the interior surfaces of the casting and are removed from the finished part during shakeout and further processing. Cores must possess strength, permeability, the ability to withstand heat, and collapsibility.

What is the difference between pressure casting and die casting?

In die casting, molten metal is forced into the die cavity at higher pressure than is commonly in pressure casting. In pressure casting, the molten metal is forced upward by gas pressure into a graphite or metal mold or by a vacuum.

Die casting produces thin parts, and yet there is a limit to how thin they can be. Why can thinner parts not be made by this process.

Because of the high thermal conductivity the metal dies exhibit, there is a limiting thickness below which the molten metal will solidify prematurely before completely filling the mold cavity.

What casting process is generally used for casting hollow cylindrical parts, such as pipes?

True centrifugal casting.

What is the purpose of a riser? A vent?

A riser supplies additional molten metal to the casting as it shrinks during solidification. A vent is placed in molds to carry off gases produced when the molten metal comes into contact with the sand in the mold and the core, it also exhausts air from the mold cavity as the molten metal flows into the mold.

Explain why die-casting is economical for large production runs.

Equipment costs, particularly the cost of dies, are somewhat high, but labor costs are generally low, because the process is semi- or fully automated.

List the factors on which the unit cost of cast depends.

Material, Equipment, Labor: Powering, solidification, extraction and finishing.

How would you compare and contrast die casting and investment casting processes?

Die casting is one further example of permanent-mold casting, while in investment casting process, the mold will be broken. In die casting, molten metal is forced into the cavities at high pressure, while in investment casting, the molten metal is just poured into the mold cavity through gravity. More intricate shapes can be produced from investment casting than from die casting.

The hot-chamber die casting process involves the use of a piston, which traps a certain volume of molten metal and forces it into a die cavity through a goose neck nozzle. (T/F)


Three ways to reduce roll forces during flat rolling.

-Smaller rolls

-Reduce friction through lubrication

-Reduce thickness reduction in a single pass

Under what condition does spreading occur?

Whenever the width is greater than the thickness, there is no spreading. When width is less than the thickness or nearby, there is spreading.

Define investment casting.

The pattern is made of wax, or a plastic

Three defects that could result in casting.