Lecture 7 Homework PDF

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Lecture 7 Homework...

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Lecture 7 HW ME215

2.

“Materials processing” is a series of operations that transforms raw materials into

finished parts or products that have a desired structure and properties of a desired shape in the desired quantity. 8.

The mold materials for the casting can be controlled by various means to obtain the

desired properties. Metals contract during solidification and cooling, porosity caused by gasses evolved during solidification can causes a problem, the adverse effect on the mechanical properties of the metals. Although most metals shrinks during solidification, if the mold material provides too much restraint to the solidifying and cooling metal, dimensional changes and cracks will begin to form in the casting since it will contract when its strength is low. 10.

The various components that make up gating system are the sprue, pouring cup , runners

and gates. Chapter 14 1.

The factors that influence the selection of a specific casting process as a means of making

a product are the properties of material, cost of mold, surface finish and production rate. 50.

The shell molds have excellent permeability and collapsibility because they have thin

gapes allowing the gas to escape from the mold quickly and some of the resin binder in the shell molds burns off when heated by molten material. Chapter 15

1.

The various disadvantages of the expendable-mold casting process is that a new mold has

to be made for each casting which might cause difference in dimensional variations. Which affects mold consistency, strength, moisture and pattern removal between all the molds. 3.

The various materials that are used in making permanent-mold castings are bronze, steel,

graphite and gray cast iron. The metals more commonly used for castings are magnesium, aluminum and copper alloys. 4.

The process advantages of permanent-mold casting are a. Excellent surface finish b. Reusable mold c. Perfect dimensional accuracy d. Faster cooling rate e. Controlled solidification

28. Chapter 16 1.

Accurate parts with controlled characteristics would be considered a prospect for powder

metallurgy manufacture because powder it involves belding of various powders into desired shape. Due to blending of powders different properties can imparted. 2.

Some of the earliest powder metallurgy products are a.

Platinum ingots

b. Tungsten wires c. Coin and Medallions d. Metallic filters

5.

Some of the primary market areas for P/M products are hand tools, hardware items

,industrial motors, hydraulics, automotive applications and business machines. 11.

Elemental metal particles are produced by thermal decomposition, chemical reduction

and condensation process. 15.

Green strength of the powder metallurgy material after pressing but before sintering.

Good green strength is needed to produce smoother surface, sharp corners and finishing it is an important property to manufacture high quality P/M products. Chapter 35 3.

Welding is a process in which two bodies are joint permanently by coalescence made by

a combination of pressure, temperature and metallurgical conditions. 7.

The three primary aspects required to produce a high quality weld a.

A way to protect or clean the metals to joined

b. A source of satisfactory heat/pressure c. Caution to avoid negative metallurgical effects. Chapter 36 2.

The combustion of oxygen and acetylene is two stage reaction. The outer flame preheats

the metal and protects it from the surrounding atmosphere while the inner part of the flame produces the required temperature. 9. 11.

Filler metal is added between two parts being welded to fill the gapes. The low heat has low rate of heat in welding can cause distortion and changes in metal

properties.

Chapter 37 7.

The resistance between the electrodes and the workpiece can be reduced by high quality,

high conductive materials such as copper. Chapter 38 6.

Electroslag welding is possible by passing an electric current through the liquid slag.

18.

Laser-beam welding more attractive than electron-beam welding because vacuum work

is not needed, there is no physical contact between workpiece and welding equipment and there are no x-rays to contend with. 33.

Types of materials are applied during surfacing operations are a. Copper alloys b. Stainless steel c. Nickel based alloys d. Silicates e. Aluminum alloys f. Tungsten and Chromium g. Oxide and borides h. Refractory carbides.

40.

Brazing is forming, fixing, or a joining method by soldering alloy with copper and zinc

at a high temperature. Soldering is the process of joining two or more electronic parts using solder....