Welding 2 go. alhuzaim_af [Type the company name] 8/2/2012

Transcription

1 2012 Welding 2 go alhuzaim_af [Type the company name] 8/2/2012

2 One must try by doing the thing; for though you think you know it, you have no certainty until you try. - Sophocles 2

3 I would like to express my gratitude to all those who gave me the possibility to complete this handbook. I want to thank the Royal Commission for Jubail for giving me the opportunity to continue my education and be able to prepare such a handbook. Special thanks are reserved for Jubail Technical Institute for support and providing the facility and workshops Many thanks are represented to Hobart institute of welding Technology for providing great training and materials Also I would to thank My Photographer Mr. Mohanad Mohammed Alnajdi for his great photos 3

4 What is welding? Welding is the joining of metals or other materials at their molecular level. There are four components to a weld. The four components are the metals weldment, a heat source, filler material, and shield from the air whether its gas or flux. Welding Concept The welding process works as following. The weldment gets heated to its melting point, with shielding from the air to protecting the weldment from oxidizing, and then a filler metal is added to the area that needs to be joined eventually producing a single piece of metal. History of Welding A process known as forge welding was used when the Industrial Revolution began around 1750 AD. It s a very simple process that takes two or more pieces of metal and heated. When the metal is hot enough you simply hammer the joint areas together until they fuse. This all worked well enough until

5 Introduction It is very important to know the difference between a joint and a weld and use terms properly Standard terms must be used when dealing with weld joint and weld geometry to avoid errors in communication 5 Basic Joint Types Butt Joint Corner Joint T-Joint Lap Joint Edge Joint Butt Joint A Joint between two members aligned in the same plane Bevel-groove Flare-bevel-groove Flare-V-groove J-groove Square-groove U-groove V-groove Edge-flange Braze 5

6 Corner Joint A joint between two members located approximately at right angle to each other Fillet Bevel-groove Flare-bevel-groove Flare-V-groove J-groove Square-groove U-groove V-groove Corner-Flange Edge-flange Plug Slot Spot Seam Projection T-Joint A Joint between two members located approximately at right angles to each other in the form of a T Fillet Bevel-groove Flare-bevel-groove J-groove Square-groove Plug Slot Spot Seam Projection Braze 6

7 Lap-Joint A Joint between two overlapping members in parallel planes Fillet Bevel-groove Flare-bevel-groove J-groove Plug Slot Spot Seam Projection Braze Edge Joint A joint between the edges of two or more parallel or nearly parallel members Bevel-groove Flare-bevel-groove Flare-V-groove J-groove Square-groove U-Groove V-groove Edge Corner-flange Edge-flange Seam 7

8 Groove-Weld Type Square-Groove Welding type that the edge of the weldment is square with or without root opening Single-V-Groove The edge of the weldment is beveled to a cretin degree usually 37 Double-V-Groove Used with thicker material to maintain penetration and prevent distortion Single-Bevel-Groove Weld Used to provide accessibility and help in penetration Single-U-Groove Weld This design reduce the stress in the joint therefore less cracking 8

9 Fillet- weld Type A weld usually accurse in T-joints or Lap joints Surfacing Weld Used in corroded material to rebuilt and increase thickness Seam Welds and Spot Welds This is resister weld where the electrode apply pressure and heat to form the weld usually used in sheet metals and automobiles 9

10 Welding Sequence Z-weave a technique used to move the electrode in Z motion to fill up the joint Stringer bead multiple beads beside each other to fill up the joint this technique reduce the heat input in the joint Boxing technique used in welding pressure vessels prevent leaking from corners Chine intermittent fillet weld used to save consumables and reduce the heat input in the weldments Staggered interment fillet weld used to prevent distortion in weldments 10

11 Back-step Sequence used to reduce the heat input in the weldments Parts of a Weld Weld Face: is the contour of the weld this could be convex, concave and flat Face Reinforcement: is the distance from the parents metal to the weld face Root reinforcement: is the distance from the parents metal to the weld root Weld Toes: is the side lines where the weld ends and the Heat Affected Zone starts 11

12 Root Surface: is the contour of the root Weld Root: the filler metal penetrating between parent metals Back Weld: is a weld made from the root side of the joint after the main weld is done Backing Weld: is a weld made from the root side of the joint before the main weld is done 12

13 Joint spacer: used to fill the root opening between parent metal Fusion Face: is the beveled face where the fusion takes place HAZ: is the area next to the weld that been affected by the heat and change the structural property Weld Interface: is the deepest penetration the filler metal reach in the base metal 13

14 Weld Size: is the size of the weld from the surface of the base metal to the deepest point in the root Incomplete point penetration: means the joint is not fully penetrated by the molten fillet metal This is a combination of square groove and fillet weld its clearly shows that this joint is not a complete joint penetration 14

15 Incomplete fusion is not limited to the root can accrue in the hot, fill and even cover pass Incomplete fusions can accrue due to the lack of accessibility and cleaning 15

16 Correct fusion must be throw out the legs of a fillet weld Welding Positions 1F Position: it s a fillet weld where the weld is flat the travel angle is and the work angle is 90 16

17 2F Position: it s a fillet weld where the weld is horizontal, the travel angle is and the work angle is 45 3F Position: it s a fillet weld where the weld is vertical, the travel angle is 45 and the work angle is push angle 4F Position: it s a fillet weld where the weld is overhead and horizontal, the travel angle is and the work angle is 45 17

18 1G Position: it s a groove weld where the weld is flat the work angle is 90 and the travel angle is G Position: it s a groove weld where the weld is horizontal the work angle is 90 and the travel angle is G Position: it s a groove weld where the weld is vertical the work angle is 90 and the travel angle is G Position: it s a groove weld where the weld is overhead the work angle is 90 and the travel angle is

19 1G Position: the pipe is turning while the welding the axle of the pipe is horizontal 2G position: the pipe is fixed, the axle of the pipe is vertical and the weld is horizontal 5G Position: the pipe is fixed, the axle of the pipe is horizontal and the weld is vertical 6G Position: the pipe is fixed; the axle of the pipe is 45 19

20 Welding Symbols All welding symbols have an arrow and a reference line. P: Pitch (center-to-center spacing) of welds L: Length of weld F: Finish symbol A: Groove angle; included Angle of countersink For plug welds R: Root opening; depth of filling or plug and slot welds S: Depth of preparation; size or strength for certain welds T: Specification, process or other reference E: Groove weld size The line between F and A is Contour symbol (Tail omitted when reference is not used) 20

21 Fillet Welding Symbols Fillet weld symbols it looks just like the cross sectional area of the weld. The symbol in the top of it is the contour which is in this case is convex. It can be concave or flat/flush 1/8 4-8 In the top fillet weld symbols 1/8 is the leg size LS in this case the leg LS1 and LS2 are equal if they are not equal it should be written as the following 1/8 X 3/16 Then show at the drawing which LS should be 1/8 and which should be 3/16. Shown one of them is enough to know the other. LS1 LS2 21

22 When the weld symbol is placed below the reference line, it shows that a weld is on the arrow side of the joint. When the weld symbol is above the reference line, it indicated that a weld is on the other side of the joint When the weld symbol is both above and below the reference line, it indicates that welds is in both sides The Leg size of fillet weld is always on the left side of the symbols The length of a fillet weld is always in the right side of the symbols Example: In this a Double fillet weld Size of weld LS 5/8 Length of weld segments is 5 Length of pitch is 10 Flat contour Finished by machining Methods of welding mechanized 22

23 Fillet Weld Calculations To find the weight of an equal leg fillet weld we need to find the Cross Section Area CSA, the length of the weld and the density of the metal. If we take the drawing 1 as an example and we suppose it s a mild steel, flat face, the following steps is how to calculate the weight of the weld To find out the CSA for any triangle we have to know the length of the base and the height of the triangle and divided by two. The mathematical formula for the triangle CSA is. Fillet weld CSA =.5 X Base X Height 23

24 After calculating the CSA, we can calculate the volume of the weld by multiplying the CSA by the length of the weld. Fillet weld Volume = CSA X Length of weld Finally, to find the weight of the weld we should multiply the volume by the density that will give us the weight of the weld. Fillet weld weight = Volume X density of metal Example 1: Calculate the weight of the above fillet weld we will use the below welding symbol to help us find what essential information to calculate the weight like the leg size and the length of the weld, if we assume the material is a mild steel for example A36. As it shown in the symbol the leg size is 5/16 inch and it mention only one size that s mean the leg size is equal. Also the length of weld is 12 inch. The density of all steel is lbs/in³. So now we can start following the steps above. 24

25 Step 1 Fillet weld CSA =.5 X Base X Height Fillet weld CSA =.5 X.3125 X.3125 =.049 in² Step 2 Fillet weld Volume = CSA X Length of weld Fillet weld Volume = 0.49 X 12 =.59 in³ Step 3 Fillet weld weight = Volume X density of steel Fillet weld weight =.59 X.283 =.17 lb The weight of the fillet weld is 0.17 lb 25

26 Example 2 If we take example 1 and we add reinforcement as showing in the drawing. Then we need to calculate the reinforcement separately and then add the flat fillet to the reinforcement to get the total weld weight. To calculate the reinforcement we need to calculate the Face Dimension FD first, we can apply Pythagoras' Theorem law to get the FD and then we can calculate the reinforcement CSA. 26

27 As we calculated in the first example the weight of the flat fillet weld is 0.17lb. So we will pursue to calculate the reinforcement and add the total weight for the weld. Pythagoras' Theorem Face Dimension FD= ( ) ( ) FD= ( ) ( ) =.44 in CSA Convexity =.5 X FD X reinforcement CSA Convexity =.44 X.125 X.5 =.03 in² Volume of convexity = CSA X Length Volume of convexity =.03 X 12 =.36 in³ Weight of convexity = Volume X Density Weight of convexity =.36 X.283 =.1 lb Total weight of the weld = Weight of fillet weld + weight of reinforcement Total weight of the weld = = 0.27lbs 27

28 Groove weld: With thicker materials joint accessibility must be provided for welding to ensure weld soundness and strength Square-groove welds are the most economical to use, but are limited by thickness of the members. Welds for one side are normally limited to a 1/4 inch or less J-groove are more difficult to weld because of the one vertical side (except in horizontal) J-and U- are used when economic factors outweigh the cost of edge preparation Bevel- and J- groove welds are more difficult to weld than V- or U- groove welds. Bevel welds are easier in horizontal Flare -bevel and flare-v-groove welds are used in connection with flanged or rounded member Welds in using J- and U-grooves can be used to minimize weld metal. These welds are very useful in thicker sections 28

29 Groove Weld Calculations Example: To calculate the weld weight in a single bevel pipe we can divide the weld into three areas as showing in the third drawing. The root opening and the thickness of the material will be area 1, the bevels will be area 2, and the reinforcement will be area 3. First we calculate the Cross Sectional Area for all three areas. -CSA1 is basically rectangle where the area is the width by the height CSA1 = root opening X thickness CSA1 =.125 X.625 =.08 in² 29

30 -CSA2 is two triangles where the area is (.5 X the height X base). We can calculate the height by subtracting the thickness from the root face. To calculate the base which is the side opposite in the triangle we can use TAN the height or the side adjacent. CSA2 = thickness - root face X {(thickness root face) X tan ( )} X.5 X 2 CSA2 = X {( ) X tan 30} X.5 X 2 =.15 in² -CSA3 to calculate the reinforcement area we have to calculate the face dimension first and that by calculating the side opposite and multiply it by 2 and add the root opening to it. Face Dimension = (side opposite X number of bevel) + root opening Face Dimension = (.5 X tan 30 X 2) =.685 in CSA3 = Face Dimension X Reinforcement X.5 CSA3 =.685 X.125 X.5 =.04 in² 30

31 We add the CSAs to get the total area of the weld CSA = CSA1 +CSA2 + CSA3 = =.27 in² Finally to calculate the weight we need to calculate the length of the weld. Since it s a pipe we need to calculate the circumstance which (π X Diameter) then we multiplying it by the density of the steel which is.283 lbs/in³. Weight of the weld = CSA X (π X Diameter) X density Weight of the weld =.27 X (.3142 X 6 ) X.283 = 1.4 lbs 31

32 Example: Calculate the weight of the weld in double v groove basically solve for single V and then divided by two. Given: V groove weld both side plate thickness =.625 Total root face =.125, root opening =.067 Included angle = 75 degree, convex reinforcement =.067 Consumable density=.1 lbs/in³, weld length=14 32

33 Solution Total CSA of the weld CSA1 = Root Opening X thickness =.067 X.625 =.042 in FD= Tan (37.5) X (T/2 Root Face/2) =.767 X ( )=.192 CSA2 =.5 X.192 X.25 = 025 in² X 4 =.096 in² CSA3 =.5 X Face Dimension X Reinforcement CSA3 =.5 X ( ) X.067 =.015 in² X(2) =.03 in² Total volume of the weld V= CSA X Length =.168 X 14 = 2.35 in³ Total weld weight = Volume X Density Total weld weight =2.35 X.1 =.235 lbs 33