What is Welding: Definition and 67 Discussions

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature metal-joining techniques such as brazing and soldering, which do not melt the base metal.
In addition to melting the base metal, a filler material is typically added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that, based on weld configuration (butt, full penetration, fillet, etc.), can be stronger than the base material (parent metal). Pressure may also be used in conjunction with heat or by itself to produce a weld. Welding also requires a form of shield to protect the filler metals or melted metals from being contaminated or oxidized.
Many different energy sources can be used for welding, including a gas flame (chemical), an electric arc (electrical), a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding may be performed in many different environments, including in open air, under water, and in outer space. Welding is a hazardous undertaking and precautions are required to avoid burns, electric shock, vision damage, inhalation of poisonous gases and fumes, and exposure to intense ultraviolet radiation.
Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for millennia to join iron and steel by heating and hammering. Arc welding and oxy-fuel welding were among the first processes to develop late in the century, and electric resistance welding followed soon after. Welding technology advanced quickly during the early 20th century as world wars drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like shielded metal arc welding, now one of the most popular welding methods, as well as semi-automatic and automatic processes such as gas metal arc welding, submerged arc welding, flux-cored arc welding and electroslag welding. Developments continued with the invention of laser beam welding, electron beam welding, magnetic pulse welding, and friction stir welding in the latter half of the century. Today, as the science continues to advance, robot welding is commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality.

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  1. T

    From South Warrandyte Victoria Australia

    No Idea what I am expected to disclose here????
  2. Juanda

    Trying to understand welding recommendations

    Recently I found these notes with recommendations for welded joints and something is not sitting right with me. It's in Spanish but I'll translate it as close to technical English as I can. I have checked a few sources on the internet and they all say basically the same thing. I couldn't find...
  3. J

    Box Beam stress problem with welding

    Hello All, I'm trying to figure out how to strengthen a box beam that's been welded to another box beam. In the photo on the left is 2 beams welded to each other, they are 2x1" Aluminum 6061-T6, with a 1/8" wall thickness. The yellow lines indicate the location of the weld. A force of 216 lbs is...
  4. S

    I How Do We Measure and Differentiate Wringability and Cold Welding?

    What are standard quantitative measurements of wringability? What is the quantitative limit between wringing and cold welding? What are the basic reasons of weakness at wringing/cold welding fault?
  5. N

    Welding Machine Increases Power: Physically Impossible?

    How is it possible for a welding machine to end up creating more power than what it started with if that is physically impossible? For ex; 200 amp @ 28vdc welding machine. starts out with main voltage being 120v @ 20amps = 2400 watts then converts it to 200 amps at 28vdc which = 5,600 watts of...
  6. S

    Producing other metals with thermite reactions

    Hello all, I am curious as to whether it is possible to create aluminium from a thermite reaction. Thermite, as standard, uses aluminium and iron oxide, which react together when burnt to create a blob of molten iron. I would like to achieve a similar result, but with a blob of molten...
  7. V

    Ht12e/d input output logic question

    Good day. I'm currently in the soldering phase of an RF circuit designed to operate an L293D motor chip. On the breadboard I managed to get it to work, but after soldering (and checking for shorts) I am not getting proper high/low signals sent through the encoder/decoder from 2 2p2t switches to...
  8. D

    I Exploring the Effects of Cold Welding in Space

    I've read that when two pieces of the same kind of metal touch in space, they will fuse because there is no way for the electrons to "know" that they are in different pieces of metal. What would happen if two different metals were to touch in space? Would electrons still flow freely between...
  9. Neel_2910

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  10. Overflowing

    Ultrasonic Welding Help - PC Troubleshooting

    I'm exploring Ultrasonic Welding as an alternative to solvent welding of some polycarbonate parts...looking for someone with some knowledge in this arena. I'm very familiar with solvent welding acrylic, but PC is giving me troubles. Anyone willing to help me out?
  11. Polar Bear

    Welding shear and normal stress calculations

    Hello, Does anybody know how to compute shear and normal stresses which take place due to applied load? My case is a simply supported beam (120x120x6.5 length: 4.2m) reinforced by a plate (20x120 length: 2m). Plate is welded on a top of a beam and external force (F=15 kN) is applied to the...
  12. Shadow-Shocker

    Any natural, non-flammable, alternative to acrylic cement?

    I am doing a project that relates to welding acrylic. I got the bottle today, and I can't use it because its flammable and has chemicals known by the state of California to cause cancer (makes you wonder why the hell they would market this crap). Are there any clean, non-flammable, and...
  13. D

    Fillet Welding: T-Joints with 10mm Plates

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  14. R

    Micro laser welding, the picture is a crack?

    Hi guys, My name is Rogelio H. Aguirre, a grad student from the University of Waterloo working on MEMS sensors. Currently, I am working with micro laser welding suppliers to fabricate the packaging of a pressure and a temperature sensor. I have some experience on weldings, but not in micro...
  15. Vinodh Reddy

    What are the Applications of Electroslag Welding ?

    What are the applications and advantages of Electroslag welding (ESW) process ?
  16. R

    Bending and welding Aluminium 2mm sections

    Hi I am planning to make a light weight camera mount for my RC multicopter (drone). Issue is due to irregular shape of the camera, need for the mount to be light weight, and setting up a small angle of inclination (5-10 degrees) the only solution I have come up with is to use light weight thin...
  17. R

    Joining Titanium tubes to teflon tubesheet.

    What would be the possible options to join Titanium Heat Exchanger tubes to a PTFE / Teflon tubesheet? These are 38 mm tubes, 2 mm thick. 6 m total length. Seamless tubes. Is this a reasonable design decision? Full titanium tubesheet would be excessively expensive & isn't needed since only...
  18. D

    Find the Oxygen Mass in a Welding Tank

    Homework Statement A welder using a tank of volume 7.40×10−2m3 fills it with oxygen (with a molar mass of 32.0g/mol ) at a gauge pressure of 3.20×105Pa and temperature of 38.7∘C. The tank has a small leak, and in time some of the oxygen leaks out. On a day when the temperature is 22.9∘C, the...
  19. M

    British welding Standard for pipes and fittings

    I am looking all over and can't find the standard for the welding pipe with fittings into '4-'12 pipe array, by standard i mean the welding type, pipe\fitting preparation and any other Info\tips that can help.
  20. V

    How to Simulate Residual Stress induced by Friction Stir Welding

    Hello all, I am M.Tech student and doing my dissertation on friction stir welding stimulation in ANSYS Mechanical APDL. I need to simulate residual stresses induced during welding using ANSYS. How can I do the same, please reply. I am a beginner in ANSYS. I don't have much knowledge of ANSYS
  21. C

    Understanding the Process of Cold Welding

    Can someone explain the process?
  22. D

    Structural Weld Analysis Techniques for Aluminum Welding - Ask Here!

    Hey folks great forum here! Anyone here have a good reference for structural weld analysis technique? I am not looking for code requirements but a general techniques and knockdown factors for aluminum welding. thanks Dan
  23. F

    Friction stir welding in plastics?

    I'm familiar with the process of friction stir welding, which has been used with great success for assembling the fuel tanks for satellite launchers like the Delta IV and the Atlas V. However, I was wondering if, from a theoretical aspect, it would be possible to friction stir weld together...
  24. O

    Pinch valve, chance of cold welding silicone tube

    Hi everyone, In a current project, I'm curious about the risk of silicone tube cold welding when used with a solenoid pinch valve, such as = http://cfnewsads.thomasnet.com/images/large/454/454667.jpg What is the likelihood silicone tube will cold weld at the pinch point, if the pressure is...
  25. H

    Material Engineering - Metal Forming & Welding

    Homework Statement Lightweight bicycle had been fabricated from aluminium alloy tubing, with joints made by adhesive bonding. When the frame fractured near one of the joints, the owner requested that a repair be made using conventional gas tungsten arc welding. Shortly thereafter, the frame...
  26. L

    Why fire doesn't burn back to gas tank (stove and welding)

    Hi, Why the fire doesn't burn back to gas tank as there is a continuous stream of fuel from the fire to fuel tank? Thanks
  27. F

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    I have a small Lexan 141 dome I snap into a large piece of polycarbonate-ABS: I'd prefer to adhere with some other method, are any of you materials guys familiar in welding technologies? Would something like ultrasonic or vibration welding be a possibility for me?
  28. Femme_physics

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    http://img560.imageshack.us/img560/2662/nobending.jpg This exercise is from machine parts. In order to find the width of the weld, I calculate the shear force and bending moment for this exercise. However, according to my teacher, there is no bending here and I calculate this exercise for...
  29. Femme_physics

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  30. P

    Why is electric shock more dangerous with wet hands in welding operations?

    in welding operation , you never hit by electric shock,why?
  31. S

    Residual stress - Ansys welding simulation

    Hello, first of all I apologize if there is already a topic with this solution but this is my first time here, and I'm a little lost :frown: I'm developing a work which consists in the determination of residual stresses due to TIG welding. I have developed the model and ran a successful...
  32. A

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  33. L

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  34. C

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    I am looking to make a training equipment where the legs and the bases could be assembled and disassembled easily Using bolts is one option, but I am looking for a quicker option where the user just slides the base into the foot and start using the equipment. having the foot and base...
  35. Z

    Cold Pressure Welding: Tips for Success

    Hi guys. As a mechanical engineering final year student, I was assigned to design and build a cold welding prototype to weld just two sheets of metal together by lap joint. Before I actually start the designing process, I tried to cold weld the two sheet metals together by using simple methods...
  36. L

    Weld Strength: 6061-T6 Aluminum Forklift Pocket Weld

    Hello again PF I am trying to find the failure load for a 6061-T6 Aluminum forklift pocket weld with 4043 filler. Can I simply multiply the cumulative throat area by the ultimate yield strength of the filler for this value? I never had any formal education on welds, wasn't sure if I'm missing...
  37. G

    Welding Thoughts (Relationship of Current and Arc Temperature)

    Common Temperature ranges from a welding arc can range from 3000-8000 Degrees Celsius. I would like to know the direct relationship of a resultant arc temperature based on the amount of current (amps) flowing. Let's say common steel for the base metal (Electrical Resistivity: 1.74e-005...
  38. L

    Cold Welding: Can Asteroids Fuse?

    "Cold welding" question My husband posed an interesting question to me that I can't rightly answer, not being any kind of expert, when I told him about the fact that metals fuse if they come into contact with one another in space. If an asteroid collides with another asteroid, will the two...
  39. B

    Can Electromagnetic Welding Tables Improve Welding Accuracy and Efficiency?

    Is it possible to turn my 20 square foot welding table into an elctromagnet? I weld steel cut nails into artwork. The nails lay flat on the steel table, but the welding process sometimes "shifts" the nail out of position during the spot weld. This error causes the process to be shut down, and...
  40. S

    Welding and some of the terms which i

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  41. F

    Electrical Can I Build a DIY Welding Transformer From Scratch?

    I built a welder using Microwave oven transformers, but I keep melting the secondary coil, and they are a pain to rewrap. So I was thinking about building a transformer from scratch using available materials. My first obstacle is the core material, I know laminated core material is...
  42. D

    Stargazing Welding glasses safe to view eclipse with?

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  43. P

    Calculating Weld Sizes for Staircase Attachments

    Hi all, I'm trying to learn to do some basic calculations for welding, and I've been given the task in regards to finding out the weld sizes required for the loads being applied. I've got a 1.2m wide staircase, with 6 stairs, attaching to two angular beams on the outside. They will be...
  44. A

    Laser Welding Hastelloy and the problems associated with it

    Hello. I am am trying to find out why Hastelloy cracks during laser welding. What techniques are used to lessen the cracks etc. The main focus is to learn as much as I can about laser welding this material and what laser setting to start with . A simple google search has gotten me no where and...
  45. B

    Welding & Metallurgy: Possessed Steel & Luder Lines

    I have to ask this...I work at the seashore trolley museum in kennebunkport Maine as a restoration welder/fabricator. I work with old trolleys and old steel from 1907 to the 1950's and they all tell a story. I don't know how to put this to words but let me give it a try. What happens when you...
  46. A

    Effect of welding heat on hot rolled steel

    Hey guys this might be a question better suited for the Materials Engineering section but I'm not sure how much they deal with welding. Anyway I am trying to figure out how much the heat from a typical welding process would effect a steel's yield strength. I understand that on a cold worked...
  47. B

    Steel wire rope - welding or pressing

    Hello, I'm a complete laymen as far as any material science goes (engineering too), but i need Your help please. I have w steel wire rope, 2mm in diameter. i need to know two things: 1) i need to make make a "wire mesh", the simplest plain weave. however, i must make it in such a way...
  48. L

    How to welding thin SS foil (0.002 )?

    how to welding thin SS foil (0.002")? Hi all, currently I'm working on a project that require to weld two thin SS foil (0.002" thick) together. and the weld needs to be vacuum tight. What's the best way to do this? Are there companies out there that could do this for me? Thanks a lot!
  49. C

    Welding Fasteners: Effects & Properties Changes

    What are the effects when welding takes place on a fastener. If the head of a bolt or nut is welded to a plate how does it change the properties of the hardware?
  50. M

    Welding Magnets: Does Like Poles Repel?

    let me have the honour of posting this dumb question: does a magnet lose its property if two like magnetic poles are welded together?since like poles are supposed to repel!