Hot and cold working

hot and cold working

1. YoucaN Unit-3-Metal Forming Process Hot and cold working Compiled by Pravinkumar Kamatchi St.Josephs College of Engineering Assistant Professor

2. Hot and cold working YoucaN Cold working: Plastic deformation process of a metals at a temperature below the recrystallization temperature is called cold working. Hot working: Plastic deformation process of a metals at a temperature above the recrystallization temperature is called hot working.

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8. Hot working It can be defined as the plastic deformation of metals and alloys at a temperature above the recrystallization and below melting point such that fine refined grain is obtained. Maximum working temperature is 0.7 to 0.9 times the melting point. Steels - 1100 to 1260 o C Cu and its alloy -760 to 925 o C Magnesium - 315 o C Aluminium and its alloy - 370 to 455 o C YoucaN

9. Hot rolling YoucaN Rolling process

10. Hot Drawing YoucaN

11. Hot Extrusion YoucaN

12. Hot S pinning YoucaN

13. Hot spinning Metal spinning , also known as spin forming or spinning or metal turning most commonly, is a metalworking process by which a disc or tube of metal is rotated at high speed and formed into an axially symmetric part. Spinning can be performed by hand or by a CNC lathe . YoucaN

14. Hot spinning Process: A block is mounted in the drive section of lathe and supported with tailstock. And the disk is attached with head stock. Spinning roller is attached with a T-rest lever bars. It may suitable for both hot and cold working. YoucaN Commercial applications include rocket nose cones, cookware , gas cylinders, brass instrument bells, and public waste receptacles

15. Hot working- Advantages Lower working force is enough to give shape. Very dramatic shape change is possible. Properties such as strength, ductility and toughness is improved. Density increases by removing voids. Desired shape can be easily obtained under plastic deformation . Effect of impurities can be reduced . Good grain structure. Atoms in same direction leads to better strength. YoucaN

16. Hot working- disadvantages Process takes place at higher temperature that Is above 730 C , So special protection of machines is necessary other wise machine and tool life is minimum. Handling cost is high. Automation is difficult one. If the die or the tool wears the surface finish also affects . While the objects cools form its recrystallisation temperature, due to shrinkage of the parts dimension may vary . YoucaN

17. Cold working The process in which plastic deformation occurs when the process Is carried out at a temperature lower than the recrystallisation temperature. The temperature is half of absolute melting temp (723 C) Theoretically. Practically, it is room temperature. (25 to 30 C) Cold forming is mostly suitable for axisymmetric components. Blanking Tube drawing Embossing Wire drawing Metal spinning YoucaN

18. Cold working- M aterials Low and medium carbon steels Low alloy steels Copper and light alloy such as aluminium , magnesium, titanium. YoucaN

19. Cold working- Advantages Widely applied as a forming process for steel. Cold working is done at room temperature , so no oxidation and scaling of work material occurs. Excellent surface finish , which reduces the secondary machining process. High dimensiona l accuracy. Highly suitable for mass production and automation , because of low working temperature. YoucaN

20. Cold working- Disadvantages Strength of the metal is high, so large forces are needed for deformation. Complex shapes cannot be formed. Too l must be specially designed , so high tool cost. Stress formation in the metal during cold working is higher . So this requires stress relieving . YoucaN

21. Cold working- limitations It depends on the Chemical composition (percentage of carbon or alloying) of the material. The maximum limit is usually 0.45% of carbon for steels in cold extrusion &1.6% for cold forging. Larger Grain size is easy for cold working. YoucaN

22. Hot working Cold working Working above recrystallization temperature Working below recrystallization temperature New crystals are formed New crystals are not formed It hardens the metal No hardening Impurities are removed from the metal Impurities are not removed from the metal Elongation of metal takes place Elongation decreases Large size metals also deformed Limited to size Internal stress is not formed Internal stress is formed. YoucaN

23. Forging Operations YoucaN Upsetting:

24. Forging operations Upsetting: The length is shortened and either or both its thickness and width increased, the piece(stock) is said to be upset. This operation is upsetting. Increase the cross sectional area. (bolt manufacturing) YoucaN

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26. Forging operations Heading: If upsetting process is done at only one end of the piece (stock) that process is known as heading. YoucaN

27. Forging operations Blocking: To refine the shape for finish forging YoucaN

28. Forging operations Fullering : Reducing the cross section at the center plane and increases its length. This technique is commonly used to make the internal combustion of  engines. YoucaN

29. Forging operations Edging OR Rolling: Distribute the metal longitudinally by moving metal from the portion of higher cross section and increases its length by compressive force. YoucaN

30. Forging operations Punching and blanking: The most common shearing operations are punching-where the sheared slug is scrap or may be used for some other purpose-and blanking-where the slug is the part to be used and the rest is scrap. YoucaN

31. Forging operations Bending Turn a part over the anvil YoucaN

32. Forging operations Punching Process of producing holes in W/P YoucaN

33. Forging operations YoucaN

34. Forging operations YoucaN

35. YoucaN Quiz Why aluminum is highly recommended in most industries for forging?

36. Dig it with the following 5 points: 1. High strength to weight ratio. This makes it a perfect choice for a number of applications such as automotive, wheels, airframes and panels. 2. Superior corrosion resistance Aluminum forged parts do corrode, even when they’re subjected to most adverse weather conditions. This is the main reason why they are used in the petrochemical and marine industries. In fact, most fasteners in these industries are manufactured from aluminum. 3. Wear resistance and durability This makes it a perfect choice for most automotive industry applications. 4. It is a versatile metal that be manufactured with a wide range of metal forging processes. 5. Its soft compared to other materials such as iron. This reduces the production cost. YoucaN

37. YoucaN Quiz Importance of role of FLASH ?

38. A small gap between the dies called flash gutter is provided so that the excess metal can flow into the gutter and form a flash. Flash has got a very important role during deformation of the work piece inside the die cavity. Due to high length to thickness ratio of the flash gutter, friction in the gap is very high. Due to this the material in the flash gap is subjected to high pressure. There is high resistance to flow. This in turn promotes effective filling of the die cavity. In hot forging, the flash cools faster as a result of it being smaller in size. This enhances the resistance of the flash material to deformation resistance. Flash is subsequently trimmed off in order to obtain the required dimensions on the forged part. Often multiple steps are required in closed die forging. Flash is to be properly designed so that the metal could flow and fill the intricate parts of the die cavity. A thin flash with larger width requires higher forging loads. YoucaN

39. Before getting forged to intermediate shape inside the primary die set called blocking die, the billet is fullered and edged. This is called preforming . Subsequently, it is forged to final shape and dimensions in the finishing die. Closer dimensional accuracy is possible in closed die forging. However, higher forging loads are required. Parts with wider and thinner ribs, or webs are difficult to forge as they require higher forming loads. Impression dies are usually provided with taper called draft of 5 in order to facilitate easy removal of the finished part. Die preheating may be required to prevent the die chilling effect which may increase the flow stress on the periphery of the billet. As a result, incomplete filling or cracking of the preform may occur. YoucaN

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41. YoucaN Quiz Why Stainless steel is mainly used in a number of applications?

42. 1 . The forged stainless steel parts can withstand sanitizing and frequent cleaning; this is one of the main reasons why it is used in the food processing and medical equipment. 2. Highly resistant to corrosion; this is the main reason why it is used in petrochemical, marine and chemical industries, especially in pumps. These parts can withstand prolonged exposure to corrosive environment . 3. The forged parts have high resistance to heat. This makes it a perfect choice for furnace, heat sinks and ovens. 4. They guarantee high wear and high performance. This explains the reason why they are used for landing gears and motor components . 5. The forged parts have high stability and strength. This makes it a perfect choice for most structural components. In short, stainless steel is one of the most popular materials used to manufacture a number of industrial parts. This is because having some of the best physical and chemical properties YoucaN

43. YoucaN Quiz Copper Forging importance?

44. Copper and its alloys used in a number of industrial applications. This is due to its excellent electrical and heat conductivity properties. It is known for its non-magnetic, corrosion resistance, machinability , ductility, malleability and wear resistance. Forged copper parts are a perfect choice in applications where there’s higher temperatures and at a higher load. Again, the parts can withstand high stress without unexpected failures. In most cases, Forged copper parts are highly recommended. Reasons: Electrical assemblies and transmission lines such as caps, connectors and fittings Electronic components such as connectors, heat sinks, etc Plumbing components such as impellers and valve components. Gaskets and seals, especially those that are used in high temperature and corrosive environment. Power plants Fittings for high pressure applications, among other components. YoucaN

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