73
edits
Tools/mig/induction: Difference between revisions
m
1 revision imported
imported>Stever |
m (1 revision imported) |
||
| (28 intermediate revisions by 2 users not shown) | |||
Line 2:
<div id="level1"></div>
== MIG Welder induction - Level 1 ==
Level 1 induction in intended to cover the basics of how to use the [[Tools/EMP235ic|MIG welder]]. It should cover basic safety information and how to use the welder effectively on mild steel in positions 1G and 2G/F. People undertaking MIG induction need to have overalls or other non-flammable clothing that covers all exposed skin except for head and hands, clothes are likely to get burn spots on them. Wear stout shoes or boots, no open shoes allowed. If you have any metal you'd like to practice on then please bring it with you so long as it's plain steel with no galvanised coating or paint but if you don't have any then we usually have suitable scrap around to practice on. There's no charge specifically for the induction but normal welder usage charges apply, you should expect it to cost around £
Before the induction the inductor should prepare coupons consisting of 4 sheets of 2mm mild steel sized 200mm x 50mm and one of which has been drilled with 6 x 10mm holes. All edges cleaned and deburred but mill-scale left on the sheet. One additional bit of steel, thickness >1.5mm and size > 150mm x 150mm will be required for stringer bead practice and faults demonstration.
{| class="wikitable"
Line 20 ⟶ 22:
* Machine strikes an arc between the work and a consumable wire electrode, melting a pool of metal
** Welding isn't like soldering, welding melts the pieces of metal and allows them to flow together and mix with the filler material. When it re-solidifies it's one continuous piece of metal
* Wire dips in and out, adding metal to the pool
* Gas shields the hot metal from the air
Line 32 ⟶ 35:
* Arc-eye hazard to you and people around you
** Using an auto-darkening welding mask
** Checking masks with a strong light source
** Suitable settings on mask (9-11, 12 maybe - start at 10 and adjust)
** Shouting "Eyes" if there are other people around
Line 43 ⟶ 47:
** The voltage is low, but you still don't want to touch it
** Mind what you point the torch at
** Power on this welder cuts off as soon as the trigger is released, which is not the case for all welders.
** NO RINGS, NO WATCHES!!
** Users with implanted medical devices should seek doctor's approval before welding, it's not usually a problem, but please do check
** The welder plugs into
*** Use only suitably rated industrial extension leads, they're in the desk drawer B1B
*** Extension leads are a trip hazard, warn people
** If something does go wrong, shut off power before anything else
|| Using the equipment without harming self or others
Line 67 ⟶ 70:
* Clean up weld area - be aware of burning paint
* Clean area for earth clamp
*
** No bevel on thin materials
** Regular 2/3rds bevel most of the time
**
** Multipass and double sided welding are options
|| Proper preparation is necessary for good welds, cover bevel patterns for other weld types later
|-
Line 117 ⟶ 121:
** Resting your other hand on something to use as a guide
* How the pool forms (Only cover dip transfer)
* The pool wants to move, you need to just keep pace with it
* Keeping the wire aimed at the nose of the pool
** Further towards the tip of the pool = fast move, thinner bead, less penetration
Line 139 ⟶ 143:
* Arc won't strike - Ground clamp not connected
* Weld moves around erratically - too much gas or influence from holding magnets
||
|-
|
|-
| Butt joints ||
Line 191 ⟶ 195:
** Flap discs will tidy up welds that are good to start with
** Grinding discs will remove messy welds quickly
* Shutting off the gas
*
* Sweeping up and putting everything back where it belongs
* Working out your total weld length and paying for it
* Checking how much gas is left and making a post on the group if it's below about 10%
* Discuss any projects the inductee is working on to provide pointers
|| Clean up after yourself and pay what you owe!
Line 200 ⟶ 205:
| Final thoughts ||
* This has only been an extremely brief over-view of MIG welding
* Do not expect your joints to be structurally sound or pretty until you have
* The sMIG feature is providing you a LOT of help on this welder, if you switch to a welder without sMIG you may find things a lot harder
* If you want to weld aluminium or magnesium alloys, Stainless Steel, Brazing or other techniques then you can look at [[Tools/TIG/induction#level2|TIG level 2]] or [[tools/mig/induction#level2|MIG level-2]] inductions although it's not compulsory to do level-2 inductions if you've already done the relevant level-1 inductions and if you think you can manage these techniques without further help
Line 206 ⟶ 211:
|| Closing comments
|}
<div id="level2"></div>
== MIG Welder induction - Level 2 ==
Level 2 induction should cover more advanced uses
=== Main level 2 induction ===
* Going into Manual mode on the welder and suitable settings to use
** How to select manual mode
** Selecting the proper material in use on the menu
** Adjusting wire feed rate and voltage, simpler welders may use an arbitrary scale for voltage, or may not be constant voltage at all and use an inductor to control things. In that case you'll just have to feel you way through finding the right settings. Especially be aware of shitty £100 welders that may have very erratic wire feed rates.
** You don't set current, that's controlled by the interaction of voltage and wire feed rate
** Manual mode is useful for learning, especially if you expect to have to use fully manual welders elsewhere, but sMIG will almost always give better results when available.
* Other welding modes - Globular and Spray transfer and the requirements for them
** Describe conventional (dip) transfer, globular transfer and spray transfer
** Globular transfer is normally undesirable as it's hard to control but it can achieve a deep penetration at the cost of severe splatter and difficult control
** Globular has a weird sound, a quiet hiss that's broken by a sharp crack a couple of times per second
** Spray transfer is a very high powered welding technique used for deeply penetrated welds on thick material
** The EMP235ic can just barely achieve spray transfer when loaded with 0.6mm wire and with a low-CO2 argon blend gas
** Spray transfer is very quiet in use, just a quiet whisper. It also produces a LOT of UV light so you'll need a darker shade than normal
** Both globular and spray transfer modes are only suitable for use on horizontal welds, they cannot be used vertically or overhead
* Problems
** Set up and demonstrate each of these
Line 242 ⟶ 241:
*** blowing holes in material - MUCH too much voltage
*** Lots of sparks and brown/porous weld - not enough gas or too far away
* Using tip-dip
** The dip is to keep the tip clean, it tends to prevent spatter from sticking to the nozzle
** The dip is waxy and has to be applied while the tip is hot so you do a bit of welding first, then dunk the tip into the dip and shake off excess
** Only a thin coating is needed and you don't have to reapply too often, every 10-20 minutes of arc time is fine
** Spatter can just be rubbed off with a gloves finger as the spatter will not stick
* Using anti-spatter spray
** The spray is to protect your work if it needs to be very clean and you can't easily clean it other ways
** The spray is applied to the work before you start and prevents the spatter from sticking to it.
** You can weld through the sprayed on coating so long as you don't apply it too heavily
** But if your welds are structural or otherwise sensitive to contamination, don't use it
* Controlling weld distortion
** Metal pulls towards the heat source when it cools and so it pulls towards the weld and in the direction of travel
** You CANNOT prevent distortion, but you can control it.
** Extensive tacking and clamping will help reduce it a bit.
*** Tack a lot, correcting distortion as you go
** Pre-compensation can help
** Bridge blocks on the back of a weld can restrict it a lot
** Order of welds within a joint can be used to help cancel out distortion.
*** Consider the directions of travel, that can provide a degree of compensation.
*** Subsequent welds on the same joint have diminishing effects on distortion because the other welds restrain it
*** Standard sequence for T-joint (alternating directions on opposite sides) and mitered corners. (outside, sides from inside to outside, inside in opposite direction)
* Working with thin (1mm) and thick (5mm) materials
** For thinner materials heat control is vital, it's easy to heat the work up enough to cause massive distortion
*** As with all welding good tacking technique can limit this
*** Welding only in very short bursts
*** Building welds up entirely from tacks (on both sides when possible) is an effective option
*** Very high risk of blow-through if you try to seam weld something
*** Changing to a thinner wire will help, if your wire is thinner than your material it's easier to control
*** sMIG helps enormously here, far easier than manual, but make sure you train it properly first
** For thicker materials the challenge is usually getting enough heat into the material
*** For materials up to 5mm or so then single-pass welding is possible but relatively high power levels will be needed
*** The difficult part is getting enough heat into the work to allow the bead to penetrate fully, without dropping out the bottom
*** Thicker wire will help here by allowing you to add more material to the weld pool at a higher rate
*** A wide weave will be needed in order to make sure the puddle melts into both sides correctly without causing under-cut
**** Undercuts are normally caused by too long an arc, too much power, or failing to pause at the edges of the weave
*** An ideal weld will fill the gap and protrude from the surface by 0-3mm, without any sunken areas or under-cuts
** Multi-pass welding
*** For very thick materials (6mm+) is is likely that this welder will struggle to achieve an acceptable single-pass weld, so multiple passes will be needed
*** Multi-pass welding can be done from one or both sides depending on access. Distortion control will be very much easier if it can be done from both sides
*** Bridge blocks are normally used on multi-pass welds
*** The first pass (called the root) focuses on fully closing the gap at the bottom of the weld with complete penetration, and without causing too much distortion
*** Welds must be cleaned (normally with wire wheel) in between passes
*** Subsequent passes (called fill) are made with a normal welding technique to fill up the grove to just below surface. Alternating sides and directions will help reduce distortion
*** Final pass(s) (called the cap) are made with a much wider than normal weave to finish off the surface and to leave it protruding 0-3mm as for other welds.
** Very thick materials (8mm+)
*** Standard short-circuit transfer MIG is not recommended on materials >8mm thick
*** It will be very hard to get enough heat into the work to achieve full fusion
*** Spray transfer is recommended, although globular transfer might help
* Lap joints of dissimilar thickness and dealing with burn-back issues
* Welding hardening steels
** Attempting to weld hardened or heat-hardenable steels by conventional approaches will usually result in cracking
** Consider what wire material you want to use, given the strength of joint you need.
*** Aluminium is the very softest wire, but can only be used on aluminium or titanium
*** Bronze is the still quite soft and the most compliant wire usable on steel, it's very unlikely to result in cracking
*** Stainless steel is harder and stronger but does carry more risk of cracks and needs more care
*** Using a hardenable wire gives the strongest result but has the highest risk of cracking
** Differential heating and fast cooling causes the trouble
*** If the steel is hardenable then it WILL harden along the edges of the weld
*** Hardening steels normally contract and pull away from the weld resulting in high tensile and sheer stresses
*** Hardened steels are brittle and easily cracked by tensile stress
*** Most of the trouble occurs because the heat-affected zone around the weld is small and cools very rapidly while the bulk of the material remains unaffected.
** Heat control and management will be needed to prevent cracking
*** Parts can (and usually should) be pre-heated because having the bulk material hot will mean the weld bead cools more slowly
*** Pre-heat temperature is a difficult balance, you'll need to research the metal you're welding and work out if there are any temperature bands that shouldn't be used. If you can't get detailed guidance then temperatures in the range of 250C-400C are normally good. Higher temperatures make the metal harder to handle and increase oxidization but reduce thermal stresses.
*** Work out your clamping arrangements and how you're going to have to move the work around before you start pre-heating, you cannot use clamping magnets because at these temperatures the magnets will be permanently degraded.
*** For small work the [[Tools/oven|materials oven]] may help, for larger workpieces then the blowtorches can be used.
*** Post-heating is used to try to prevent the weld bead from becoming over-hardened
*** This can take the form of simply wrapping the work in insulation to slow it's cooling, or using the blowtorch or oven.
*** Cooling times will vary with weld size, for large welds several hours may be needed
** Post-annealing can help if it's done very soon after welding, before the metal has cooled to room temperature
*** Heating the metal up to annealing point and cooling very slowly can be very effective in relieving stresses in the metal
*** But be aware it may change the bulk properties of the workpeice
** Weld peening can help in difficult situations
* Welding mild steel in position 3
* Changing the gas bottle
* Changing wire, torches and liners, proper setting of wire feed and tension
Line 252 ⟶ 321:
Optional modules that can be included in level 2 induction at additional cost to inductee owing to expensive materials needed
* Welding with Aluminium, using suitable gasses. Costs £
* Welding Stainless Steel, using suitable gasses. Costs £
* MIG brazing, which allows joining materials with less heat and distortion, and also works on some materials that can't easily be welded like cast iron and tool steels. Costs £30 extra
*
<div id="mma"></div>
== MMA (Stick welding) Induction ==
This induction in intended to cover the basics of how to use the MIG welder in MMA (stick welding) mode, it covers basic safety information and how to use the welder effectively on mild steel in positions 1G and 2G/F. It is strongly recommended that people undertake MIG induction and practice it thoroughly before attempting stick welding, that said you can start welding straight away with stick but it's likely to take considerably longer to develop the required skill to use it effectively. People undertaking stick welding induction need to have overalls or other non-flammable clothing that covers all exposed skin except for head and hands. Wear stout shoes or boots, no open shoes allowed. If you have any metal you'd like to practice on then please bring it with you so long as it's plain steel with no galvanized coating or paint but if you don't have any then we usually have suitable scrap around to practice on. There is a charge of £10 for the induction to cover materials and a bit more if you spend some time practicing afterwards which is strongly recommended. The needed materials are usually kept in stock but if we've run out it will take several days to get more. This induction is estimated to take 1-2 hours.
Line 320 ⟶ 390:
** Make sure the electrode size is suitable for the work
** Rods must be kept dry, all rods are moisture sensitive but some more so than others
*** Damp rods will form shitty welds and tend to result in slag entrapment and worm holes
** Baking rods if they're not brand new
** Keeping them in a rod oven if you get serious about MMA welding.
Line 348 ⟶ 419:
** Navigating the menus and selecting MMA mode
** Setting suitable current for the electrode size
*** Check online for calculators for current, but absent other guidance, 75-90A for a 2.4mm electrode, 100-140A for a 3.2mm.
** Changing over the leads and connecting the stinger
* Proper position of self and electrode, direction of motion
Line 364 ⟶ 436:
* Moving the pool along
* Keeping the electrode at the nose of the pool
* Dragging the puddle along behind the rod
* Using the arc force to keep the slag out of the weld
* Moving patterns, circles, arc, steady
* You may need to adjust the shade of your mask to get a clear view
Line 377 ⟶ 448:
| Problems ||
[Deliberately set up and demonstrate each of these faults]
* Arc too Long - Large arc visible and moving, puddle wide and flat, lots of spatter, undercut risk
* Angle wrong - Poor visibility, lots of slag trapped in the weld "Worm holes"
* Too Hot - Weld sounds very different, hissing not "frying bacon"; puddle overly large, concave and spattery; Deep v-pattern; Surrounding material cooked & distorted; Burn-back and undercut issues
* Too Cold - Globs of metal or a very small bead, weld mounded up convex; not a continuous weld; Weak arc, hard to keep it lit; worm-holes
* Too Fast - Poor penetration; very narrow; might be discontinuous
* Too Slow - Overly penetrated; bead rather wide; surrounding metal cooked; worm-holes; might blow right through the work
|| Recognising faults and knowing how to fix them
|-
|
|-
| Butt joints ||
Line 422 ⟶ 498:
** Grinding discs will remove messy welds quickly
* When you're done shut off the power to the welder and putting the leads away
* You may need to check the table and/or vice for stuck on spatter and remove it with a file or angle grinder flap disc
* Sweeping up and putting everything back where it belongs
* Discuss any projects the inductee is working on to provide pointers
| |||