welding shop.pptx

welding shop

1. CENTRAL WORKSHOP, U.I.E.T. CHHATRAPATI SHAHU JI MAHARAJ UNIVERSITY, KANPUR                 INSTRUCTION ON MANUALS WORKSHOP PRACTICE TCA 102 (WELDING SHOP)

2. INTRODUCTION The welding is a process of joining two similar or dissimilar metal by fusion, with or without the application of pressure. The fusion of metal takes place by means of heat. The heat may be obtained by electric arc, electrical resistance or by blacksmiths fire. The process of joining dissimilar metal using filler rod is called heterogeneous welding. The filler rod material is such that is melting point is less than the parent metals. The process of joining similar metals by the help of filler rod of the same metal is called homogenous welding.

3. SHAPING OF METAL There are many techniques to shape metals depending on the kind of metal and the object that we want to make. Some of the more common are given below. Blanking :- This is one of the simplest pressing operations also called punching. This method is used to form hollow objects like washers and bearings. Press Forging :- The heated unprocessed metal is placed between two dies, one fixed and the other mobile. The dies are the shape of the object that we want to make. They are pressed together to make the required shape. Rolling :- The heated metal is passed through a series of rollers that compress it, reduce its thickness and increase its length. It is used to make sheets and bars. By Casting :- Casting is one of the oldest manufacturing process. It is the first step in making most of the products.

4. JOINING OF METAL The methods of joining metals can be broadly divided into mechanical joining and metallurgical joining. There are various methods used for joining metals. Mechanical joining includes bolting, riveting, shrink fitting and folding all of which join work pieces by using mechanical energy. Metallurgical joining includes fusion welding (Arc welding), pressure welding and brazing/soldering which use different energies . Chemical joining that use adhesives glue.

5. ARC WELDING ARC welding is a type of fusion process to join two metals. As in any fusion process an intense amount of heat is required for melting the pieces to be joined or the filler material in some cases. In arc welding this heat is achieved by forming an arc between the welding electrode and the work piece. ARC LENGTH Arc length is the distance between two points along a section of a curve. There are three types of arc length Normal Long Short

6. Normal Arc Length :- The correct arc length or normal arc length is approximately equal to the diameter of the core wire of the electrode. Long Arc Length :- Long arc length in welding if the distance between the tip of the electrode and the base metal is more than the diameter of the core wire, it is called ‘long arc’. Short Arc Length :- Short arc length is welding if the distance between the tip of the electrode and the base metal is less than the dia. of the core wire, it is called a ‘short arc’. BASE METAL :- A base metal is also called Parent metal. It is that metal in the welding practice that has been cut by the various forms of cutting, then prepared and is to be welded. Welding is performed to join one section of the base metal to another section of base metal by means of the various welding processes.

7. FILLER METAL :- A filler metal is metal added in the making of joint through welding. ELECTRODE :- An electrode is metallic wire of standard size and length. Generally coated with flux ,may be bare or without flux coating also used the complete circuit and provide filler material to the point by an arc maintained between its tip and the work. Types of Electrode : Basically depending upon the process there are two types of welding electrodes Consumable Electrode Non-Consumable Electrode

8. Consumable Electrodes can be classified in the following groups Bare Electrode:- They don’t have any flux coating only the alloy of the metal wire. Light Coated Electrodes :- These are electrodes having coating factor of 1.25. Coating factor :- Diameter of the electrode / Diameter of the core wire. 3. Medium Coated Electrodes :- These have coating factor of about 1.45 4. Heavily Coated Electrode :- Coating factor is between 1.6 and 2.2. Non-consumable Electrodes   are not consumed during welding, with a separate welding rod serving as the filler metal that melts and joins the metals together. For instance, non-consumable electrodes are used in TIG welding.

9. METHODS OF COATING ( 1 ) BY DIPPING ( 2) BY EXTRUSION FLUX - Flux is a chemical cleaning agent, flowing agent, or purifying agent. As cleaning agents, fluxes facilitate soldering, brazing, and welding by removing oxidation from the metals to be joined . ADVANTAGE OF FLUX COATED ELECTRODE- 1 . Flux clean the surface of base metal. 2 . Flux helps to strike the arc easily 3 . Flux increases speed of. Work. 4 . Flux gives easy flow of metal. 5. Flux helps to cool the metal slowly. 6 . Hence minimizing the distortion. 7 . Flux from a gasses shield around the arc, which protect the molten weld from atmosphere contamination.

10. TOOLS TO BE USED IN WELDING SHOP Bench-Vice :- A device consisting of two parallel jaws for holding a work piece, one of the jaw is fixed and the other movable by a screw, a lever, or a cam. When used for holding a work piece during hand operations such as filling, hammering and sawing, the vice may be permanently bolted to a bench .

11. Face shield :- It is Shield (Screen) used to protect eyes from spark and highly luminous sparks. Tong :- Tongs are a type of tool used to grip and lift objects instead of holding them directly with hands. There are many forms of tongs adapted to their specific use .

12. Chipping Hammer :- A tool used to remove welding slag from a weld and welding spatter from along side welds. Used by carefully swinging and hitting the weld to shatter the slag. Wire Brush :- A wire brush is used for cleaning the welding surface, removal of slag rust etc the brush has stainless steel bristles

13. File: - It is a hand cutting tool used to remove materials from jobs by filing process. It’s made of crucible steel or high carbon steel. C-Clamp :- It consist of a made of steel or cast iron, through smaller clamp may be made of pot metal.

14. Try Square :- An implement used to check and mark right angles in constructional work.

15. Chipping Google:- Welding goggles provide a degree of eye protection while some forms of welding and cutting are being done. They are intended to protect the eyes not only form the heat and optical radiation produced by the welding such as the intense ultraviolet light produced by an electric arc, but also from sparks or debris. Apron :- It protect you and your clothing from hot metal and slag that is generated while welding, grinding or using a cutting torch.

16. Hand Gloves :- Welding gloves are personal protective equipment (PPE) that protect the hands of welders from the hazards of welding. These gloves allow digit articulation while protecting the operator from electrical shock, extreme heat, and ultraviolet and infrared radiation, and also provide abrasion resistance and enhanced grip. Electrode Holder :- An electrode holder commonly called a stinger, is a clamping device for holding the electrode securely in any position. The welding cable attaches to the holder through the hollow insulated handle.

17. Electrode :- An electrode is metallic wire of standard size and length. Generally coated with flux ,may be bare or without flux coating also used the complete circuit and provide filler material to the point by an arc maintained between its tip and the work. Welding table :- A welding table is a platform that is at waist level and it works like a workbench. You use it when you are working in metal fabrication with welding. A welding table is very useful because it gives the welder a stable place to work and also can provide assistance with both squaring and measuring .

18. Angle Grinder :- An angle grinder, also known as a side grinder or disc grinder, is a handheld power tool used for grinding (abrasive cutting) and polishing. Angle grinders can be powered by an electric motor, petrol engine or compressed air. Hand Hacksaw :- A hacksaw is a fine-toothed saw, originally and mainly made for cutting metal. Most hacksaws are hand saws with a C-shaped walking frame that holds a blade under tension. Such hacksaws have a handle, usually a pistol grip, with pins for attaching a narrow disposable blade. The frames may also be adjustable to accommodate blades of different sizes. A screw or other mechanism is used to put the thin blade under tension.

19. AC transformer (step-down) welding machine:- A step down transformer is used which receives current from the supply may at 400 – 440 Volts and transformers it to the required voltage for the welding, i.e., 80 – 100 Volts.

20. DC motor Generator set :- Direct current arc welding processes can be employed irrespective of the fact whether the main A.C. Supply is available or not. In absence of the same an engine driven D.C. Generator set can easily by used. Both Alternating current (A.C.) and Direct current (D.C. ) are used for Arc welding.

21. Spot Welding:- Spot welding (also known as resistance spot welding) is a resistance welding process. This welding process is used primarily for welding two or more metal sheets together by applying pressure and heat from an electric current to the weld area

22. Seam Welding :- Seam welding is the joining of work pieces made of similar or dissimilar materials along a continuous seam. Seam welding can be broken down into two main techniques, resistance seam welding and friction seam welding.

23. WELDING POSITION : - a. Flat position :- This type of welding is performed from the upper side of the joint the face of the weld is approximately is horizontal . b. Horizontal Position :- In horizontal welding, the weld axis is the approximately horizontal, but the weld type dictates the complete definition.

24. c. Vertical Position :- In vertical position welding the axis is the weld is approximately vertical. When welding is done on a vertical surface, the molten metal has a tendency to run downward and pile up. d. Over head :- Over head welding performed from the underside of a joint. In overhead welding the metal deposited tends to drop on the plate causing the bead to have a high crown.

25. WELDING JOINT :- A welding joint is a point or edge where two or more pieces of metal or plastic are joined together. They are formed by welding two or more work pieces according to a particular geometry. There are five types of welding joints. TYPES OF WELDING JOINT 1. Butt Joint :- Being the universally accepted method for attaching a pipe to itself it’s also used for valves, flanges, fittings, and other equipment.   A butt welding joint is also known as a square grove weld.  It’s the easiest and probably the most common weld there is.  It consists of two flat pieces that are side by side parallel. It’s a very affordable option.

26. 2. Tee Joint Tee welding joints are formed when two members intersect at a 90° angle which makes the edges come together in the center of a plate or component.  Tee Joints are considered a type of fillet weld, and can also be made when a pipe or tube is welded onto a base plate.  Extra care is required to ensure effective penetration into the roof of the weld .

27. 3. Lap Joint :- Lap welding joints are used most often to joint two pieces with differing thicknesses together.  Also considered a fillet type, the weld can be made on one or both sides.  A Lap Joint is formed when 2 pieces are placed in an over lapping pattern on top of each other.

28. 4. Edge Joint :- Edge welding Joints are often applied to sheet metal parts that have flanging edges or are placed at a location where a weld must be made to attach to adjacent pieces.  Being a groove type weld, Edge Joints, the pieces are set side by side and welded on the same edge.  For heavier applications filler metal is added to melt or fuse the edge completely and to reinforce the plate.

29. 5. Corner Joint:- Being one of the most popular welds in the sheet metal industry the Corner welding joint is used on the outer edge of the piece.  This weld is a type of joint that comes together at right angles between two metal parts to form an L.  These are common in the construction of boxes, box frames and similar fabrications.

30. EDGE PREPARATION Edge preparation consists of removing material along edges of metal surfaces. You must prepare edges for welding when parts and assemblies require certain strength. To achieve full welding penetration, you must cut the edges of the metal. 1. 3. 2. 4.

31. 6. 5. 7. 8. Welding Defects Welding defects are generated in a welding job due to the faulty or poor technique used by the inexperienced or unskilled welder or due to fundamental difficulties in the welding operation. An ideal weld or good weld should be such that adequate fusion exists between the filler metal and edge preparation together with good penetration.

32. WELDING TEST :- A. Distractive:- 1.Tensile test 2.Bending test 3.Hardness test B. Semi distractive:- 1.Cutting test 2.Drilling test C. Non distractive:- 1.Visual test 2.Paraffin oil test 3.Magnetic test 4.X -Ray test RECOMMENDATIONS OF FILTER GLASSES FOR MANUAL METAL ARC WELDING Shade No. of colored glass Range of welding current in amperes 8-9 Up to 100 10-11 100 to 300 12-14 Above 300

33. SIZE (mm) AMPS. 2.00×300 50-70 2.5×350 70-100 3.15×350/450 90-120 3.20×350/450 90-120 4.00×450 140-180 5.00×450 180-220 6.30×350 240-280 FLUX COATED MILD STEEL ELECTRODE CURRENT CONDITIONS USE AC 50 OR DC

34. Cable dia. Length of cable in meters Current capacity in amperes (mm) 0-15 15-30 30-75 24.0 600 600 400 21.0 500 400 300 19.0 400 350 300 18.0 300 300 200 16.5 250 200 175 15.0 200 195 150 14.5 150 150 100 13.5 125 125 75 RECOMMENDATIONS OF COPPER FOR ARC WELDING

35. SAFETY PRECAUTIONS All welding plants should be operated according to the maker’s instructions. Check all parts of machines by the help of an electrician before starting them. All electric connections should be sound and properly tightened. Always use welding shield or helmet to protect eyes and also use. Chipping goggles while chipping slag or that the time of grinding. Always use hand gloves and the apron while welding. Do not look at an electric arc with naked eyes. Do not use cracked or defective shields or helmets. Do not weld while wearing wet gloves or shoes. Do not strike an arc on a compressed gas cylinder. Do not weld on galvanized metal without permission from instructor. Do not leave the electric holders on the table or in contact with grounded metallic surface. Always switch off current when not welding. Always keep the shop clean, dry and ventilated. When leather gloves adequate clothing and heavy shoes tightly laced. Get prompt first aid burned or if your eyes have been injured by a flash, Memorize the location of the fire extinguisher.

36. GAS WELDING

37. Introduction :- Gas welding is a welding process that metals and joins metals by heating them with a flame caused by a reaction of fuel gas and oxygen. The flux may be used to deoxidize and cleanse the weld metal. OXY- ACETYLENE GAS WELDING:- Oxy-fuel welding and oxy-fuel cutting are processes that use fuel gases and oxygen to weld or cut metals. Is a process which relies on combustion of oxygen and acetylene. When mixed together in correct proportions within a hand-held torch or blowpipe, a relatively hot flame is produced with a temperature of about 3,200 C.

38. Water to Carbide Plant :- The simplest process reacts calcium carbide with water to produce acetylene gas and a calcium carbonate slurry, called hydrated lime. The chemical reaction may be written as :- CaC 2 + 2H 2 O C 2 H 2 + Ca (OH) 2 In industrial applications acetylene cylinders are maroon coloured, and with a left thread. The oxygen cylinders are black, and have a right-handed thread. That way you cannot get the regulators and hoses mixed up. Flame :- Flame mixing a fuel gas such as acetylene, natural gas, or propane with an oxidizer such as the ambient air or supplied oxygen, and allowing for ignition and combustion.

39. REGULATOR :- The main job of the welding pressure regulator is to control the pressure of the gases used in oxyfuel welding. For example, the pressure acetylene gas is under in the cylinder is typically more than seven times greater than the pressure of the gas in the torch. There are Three Types of Regulator :- Single Stage Regulator Double Stage Regulator Duplex Stage Regulator

40. NOTES :- Back Fire :- The flame action is having explosive violence. The flame clearly flashes back into the torch and burns insides with a shrill hissing or squealing noise. A flashback can occur in oxygen hose as well as in acetylene hose also. Flash Back :- A flashback arrestor or flash arrestor is a gas safety device most commonly used in oxy-fuel welding and cutting to stop the flame or reverse flow of gas back up into the equipment or supply line. It protects the user and equipment from damage or explosions. Blow Back :- Back blow occurs when welding toward the workpiece connection, or the end of a joint, or into a corner. Forward blow is encountered when welding away from the workpiece connection, or at the starting end of the joint.

41. SAFETY PRECAUTIONS Inspect equipment for leaks at all connections using approved leak test solution. Protect hoses and cylinders from sparks flame and hot metal. Use a flint lighter to ignite the flame. Open cylinder valves very slowly to keep sudden high pressure from exploding the regulators. Open and light acetylene first, then open and adjust oxygen to an neutral flame.

42. EXERCISE No. -1 Object :- To make a Single ‘ V’ Butt joint with gap as per given drawing. Material Required :- Mild Steel [ Size – 100 x 20 x 5 mm] Tools Required :- File Chipping Hammer Face Shield Wire Brush Scale C-Clamp Tong Try Square Bench Vice

43. Electrode :- M.S. Electrode 10 SWG and Medium coated size 3.15 x 450 mm Machine :- A.C. Transformer step – down oil cooled/ air cooled Machine Current Used :- 90 – 120 Amps Electrode Angle :- 60 – 70 Position :- Flat/Down hand Theory :- What is Welding shop and its uses. Procedure :- Write Point Wise Finishing of Weld :- Slag is removing by chipping hammer and the job is cleaned by brush.

44. RESULTS :-

45. EXERCISE No. -2 Object :- To make a ‘ T’ joint as per given drawing. Material Required :- Mild Steel [ Size – 100 x 20 x 5 mm] Tools Required :- File Chipping Hammer Face Shield Wire Brush Scale C-Clamp Tong Try Square Bench Vice

46. Electrode :- M.S. Electrode 10 SWG and Medium coated size 3.15 x 450 mm Machine :- A.C. Transformer step – down oil cooled/ air cooled Machine Current Used :- 90 – 120 Amps Electrode Angle :- 60 – 70 Position :- Flat/Down hand Theory :- What is Welding shop and its uses. Procedure :- Write Point Wise Finishing of Weld :- Slag is removing by chipping hammer and the job is cleaned by brush .

47. RESULTS :-