1. Enumerate five heat treating practices in ferrous metals and describe each briefly:
        Annealing – heating above t...
Boring machine
      Used to enlarge a hole by means of an adjustable cutting tool with only one cutting edge.




Power s...
Broaching machine
                Used to finish internal or external surfaces, such as holes or keyways by the use of a c...
5. Describe the basic operation or steps in hardening of steel.
         From the PSME Code 2003 Edition Page 367, Article...
9. Enumerate the factors to be considered in estimating welding costs.
                  (1) Cost of materials required (w...
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Reading 1

  1. 1. 1. Enumerate five heat treating practices in ferrous metals and describe each briefly: Annealing – heating above the transformation range, usually 1300 to 1350oF, and cooling slowly to soften the metal and increase ease in machining. Hardening – heating above the transformation temperature and quenching usually in oil, for the purpose of increasing the hardness. Normalizing – heating to some 100oF above transformation range with subsequent cooling to below that range in still air at room temperature to produce uniform structure of the metal. Stress Relieving – heating to a subcritical temperature, about 1100 to 1300oF and holding at that temperature for a suitable time for the purpose of reducing internal residual stresses. Tempering – reheating to a temperature below the transformation range, followed by any desired rate of cooling to attain the desired properties of the metal. 2. Listed below are common machine tools found in machine shops offering general engineering and fabrication jobs. For each machine tool, give the specific job it is intended for use and make a simple drawing indicating the important parts: Drilling machine Used mainly for producing holes in metal by the use of a cutting tool called drill. Milling machine Used to form metal parts by removing metal from a work piece by the use of revolving cutter with many teeth, each tooth having a cutting edge which removes its share of the stock. Tool grinder Used to sharpen or shape tools by using an abrasive wheel.
  2. 2. Boring machine Used to enlarge a hole by means of an adjustable cutting tool with only one cutting edge. Power saw Used to cut metal of light, medium and large sections using a reciprocating hacksaw blade. Shaper Used to machine flat or plane surfaces with a single point cutting tool. Planer Used for production of flat surfaces on pieces too large or too heavy to hold in a shaper.
  3. 3. Broaching machine Used to finish internal or external surfaces, such as holes or keyways by the use of a cutter called a broach, which has a series of cutting edges or teeth. 3. Give specific usage of bronze and brass. State the differences between the two materials. Give the specific usages of cast-iron and cast-steel. State the differences between these two materials. Give the differences between the two methods of hot working metals, rolling and forging. Bronze and Brass: Uses of Bronze: clutch disks, pump rods, shafts, valve stems, cutter pins, lock washers, bushings, springs, wires, bolts, nuts, rivets, screws, tubes. Uses of Brass: propeller shafts, piston rods, valve stems, nuts, bolts, rivets, screws, springs, radiator cores, pins, tubes. Differences: Bronze is an alloy of copper and tin while brass is an alloy of copper and zinc. Cast-iron and Cast-steel: Uses of Cast-iron: cylinder block, brake drums, gears, machine tool ways, and in general, where there is metal-to-metal contact and relative motion. Uses of Cast-steel: gears, crackshafts, aircraft radial engine cylinder barrels. Differences: Cast-iron contains much carbon (2.6 to 3.6%), while cast-steel contains 0.25 to 0.50% carbons. Cast-steel has higher strength and ductility than cast-iron. Rolling and Forging: Rolling is the process of forming metal parts by the use of dies after the metal is heated to its plastic range. Forging is the process of forming metal parts by the use of powerful pressure from a hammer or press to obtain the desired shape, after the metal has been heated to its desired plastic range. 4. Give the range of motor power in kW and the type of motor required for the following: Forging machine, 100 mm size D, E or F; 37 kW Punch press, 50 mm hole diameter 25 mm thick plate, soft steel A, C, D or E; 7.5 kW Engine lathe, average service 685 – 915 mm swing A, B or C: 15 – 8.5 kW Hydraulic press, 300 tons Capacity B or C; 4.5 – 5.5 kW Engine late with swing of 457 mm to 610 mm 7.5 – 11 kW, Type A, B or C Milling machine with maximum feeding movement of 864 mm lengthwise, 355 mm lateral and 589 vertical. 5.5 – 7.5 kW, Type A, B or C Hydraulic press of 200 tons capacity 3.7 – 5.5 kW Type B or C Shears for soft steel of 914 mm to 1575 mm width and 1.55 mm thickness 1.5 – 2.2 KW, Type C, D or E Punch press for soft steel 28.6 mm thickness and for 57 mm hole 7.5 – 11 kW, Type A, C, D or E The above answers are taken from the PSME Code 2003 Edition Page 289, Table 13-1
  4. 4. 5. Describe the basic operation or steps in hardening of steel. From the PSME Code 2003 Edition Page 367, Article 16.4.1.2 The basic operation in hardening of steel consists of two steps. The first step is to heat the steel to some temperature usually at least 38oC above its transformation point so that it becomes entirely austenic in structure. The second step is to quench the steel at some rate faster than the critical rate (which depends on the carbon content, the amounts of alloying elements present other than carbon, and the grain size of the austenite) to produce a martensitic structure. The hardness of a martensitic steel depends upon its carbon content and ranges from about 460 Brinell at 0.20 per cent carbon to about 710 Brinell, pearlite about 240 Brinell, and cementite around 550 Brinell. 6. When steel is described as SAE 1320, what does it mean in terms of mineral content? SAE 1320 is Manganese steel containing approximately 0.20% Carbon. Its typical composition (as taken from Kent’s Mechanical Engineering Handbook: Design and Production Volume, Table 3, Page 2-27) is as follows: C: 0.18 – 0.23% Mn: 1.60 – 1.90% P (max): 0.040% S (max): 0.040% Si: 0.20 – 0.35% 7. By means of sketch, illustrate the following welded joints: a. For Butt welded joint i. Single V-groove iii. Square groove ii. Double V-groove iv. Single-U b. For Fillet welds i. Lap joint iii. Corner joint ii. Tee joint iv. Strap joint 8. Name three factors which must be considered when preparing work for welding in order to get best results. Explain. From Ken’s Design Handbook Page 21-10 (1) The work should be positioned so that it is within easy reach of the welding operator. This means that wherever possible welding should be done in the down hand position rather than the difficult overhead position. (2) The dimensions of the joint should be such that complete fusion through the thickness of the sections being welded will be attained. A weak welded joint will result if incomplete fusion is obtained. (3) Butt joints are preferable because it produces uniform stress distribution across the weld. If fillet welds are used, a 30-60 degree weld provides more uniform transfer of stress through the weld than a 45-45 degree weld.
  5. 5. 9. Enumerate the factors to be considered in estimating welding costs. (1) Cost of materials required (welding rods, oxy-acetylene, etc.) (2) Salary of welding operator (3) Cost of power to operate welding machine (4) Cost of cutting and forming the parts (5) Cost of positioning and machining 10. Name at least 5 requirements that bearing must meet, more or less fully, in order to function properly. From Kent’s Mechanical Design Handbook, Page 4-73 (1) Score resistance (2) Compressive strength (3) Deformability, including conformability and embedability (4) Fatigue strength (5) Corrosion resistance 11. Name at least four (4) common areas found in a machine shop (1) Welding area (2) Mass production area (3) Foundry area (4) Tool and die area 12. What are two principal reasons for tempering steel? (1) To restore a certain amount of ductility and reduce the brittleness (2) To reduce internal stresses 13. Name four (4) operations involved in the heat treatment of steel (1) Heating (2) Cooling slowly in a furnace (3) Quenching or rapid cooling in water or other cooling medium (4) Nitriding or heating steel alloys immersed in ammonia fumes 14. Name at least four (4) classifications of workers in machine shop. (1) Welder (2) Machinist (3) Foundry man (4) Tool and die maker 15. Give three (3) desirable qualities of steel resulting from alloying. (1) Improved hardenability (2) Increased tensile strength (3) Increased toughness 16. In alloying steel with chromium, what three (3) desirable qualities result? (1) Improved hardenability (2) Resistance to corrosion (3) Strength at high temperature 17. What are the characteristics of free cutting steels and its intended usage? Free cutting steels are easy to machine, that is easy to turn, easy to mill, easy to saw. They are usually used in the production of bars, rods and wires. 18. Name three (3) common cutting fluids used for metals. (1) Thin soluble oil solution, approximately 40-1 (2) Solution of soda or borax in water (3) Oil containing large percentage of sulfur

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