Tools/forge/induction

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Some of the tools at the Hackspace are potentially hazardous to use, for these tools members are required to have an induction before they can use them. Inductions provide the most basic information on how to safely and effectively use the simpler functions of the tools, we appreciate that some members may have professional experience on some of these tools and in this case please tell your induction provider and the induction may be very reduced and just cover any risks or procedures specific to rLab. Some tools have multiple levels of induction in order to cover more advanced uses of that tool without making the basic induction take too long, higher induction levels will introduce some of the more advanced features of the tools but as with all inductions are only intended to provide basic information on the capabilities of the tools and how to use them safely. Some members of rLab may be willing to offer more detailed tuition beyond basic induction level or offer guided practice sessions in exchange for beer money or assistance on their own projects.

For all tools you are only required to take level-1 induction before use, after that you may perform any task that you feel confident you can do safely, higher levels of induction may be useful to you in performing more advanced operations but are not required before doing tasks covered in them so long as you're confident of your ability to handle those tasks without risk to yourself, others, or the tool.

PLEASE NOTE : All induction providers are volunteers who are providing inductions to the best of their ability but are NOT qualified instructors. Inductions are provided on a best-effort basis but you and you alone are responsible for your safety while using the tools and for satisfying yourself that you can operate the tools safely. There are professional training courses available from various providers in Reading and the surrounding area if you feel they are appropriate for the level of work you intend to undertake. Reading these notes is NOT a substitute for an in-person induction.

Note for wiki editors : Please do not edit induction pages unless you are one of of the people that gives that induction

The forge gets up to a maximum of 1350 ºC, uses flammable gas, has the risk of igniting metals and many other hazards, for that reason an induction is compulsory before using the forge. Induction normally takes about 2 hours, and another 2 hours for the forge to cool down afterwards before it can be put safely away. The forge has a useage charge of £3/hr so you can expect to pay in the region of £10 to cover 2 hours of forge time and materials to use for practice.

Safety

Topic Detailed Contents Rationale
Suitable Clothing
  • Old Clothes, they're going to get burn spots
  • Overalls are best
  • Avoid synthetic fabrics, they burn and melt
  • Heavy, Steel Toecap boots are a very good idea, but at least stout shoes, no sandals, no open-toed shoes
Suitable clothing is essential for safety
PPE Required
  • Goggles are required AT ALL TIMES WHILE FORGE IS LIT - the forge WILL shoot out flakes of red-hot scale
  • Welding gloves or heat-tolerant work gloves - dop rods will get hot!
  • Anti-vibration gloves if you're doing a lot of forging
  • Ear protection while hammering
Good PPE to protect from specific hazards
Workshop hazards and mitigation
  • Good air circulation needed - doors open but only slightly, monoxide hazard and detectors - immediate shut-down and evacuate if they go off
  • Heat buildup in the laser room
  • Slip hazard from quenching oil
  • Hazards of metals high in nickel, chrome, cadmium etc, and protection needed
  • Arc-eye hazards of welding
Hazards other than fire that could impact the rest of the workshop
Fire risks

Fire and burns are the single largest hazard in forging.

  • Clearing the area around the forge of all flammable materials, especially sawdust and the bins
  • Be aware of hazards of flammable vapours and solvents, keep well away from the forge
  • Back of the forge gets hot too, so be aware of what you're backed up against
Things that can cause fire
Dealing with Fire
  • In case of fire, TURN GAS OFF!
  • What types of extinguisher to use on what sort of fire
  • Using fire extinguishers
    • Calling for help, alerting people
    • Consider if the fire is small enough to fight
    • What types are suitable for what fires
    • We cannot extinguish metal fires, use the vermiculite to smother or place on a safe surface
    • NEVER use an extinguisher on the forge it's self, it has nothing flammable anyway and risks an explosion
    • Fire hazard from quench oil
    • How to use an extinguisher
Have to be ready to deal with a fire if it happens
Burn treatment
  • Evaluating the seriousness of burns
  • Basic burn first-aid
Shouldn't happen, but it's always a risk and people need to know how to deal with that

Theory of steel forging

[Draw the iron-carbon phase diagram on the board covering 0-1.5% carbon and 0-1500 ºC]

Topic Detailed Contents Rationale
States of steel and their properties
  • Ferrite - Soft, workable
  • Cementite - Hard, Brittle
  • Pearlite - Soft layered structure, normal resting state for most steels
  • Austentite - High temperature structure, soft, malleable, workable, dynamic structure
  • Martensite - Not a natural structure, formed by heat treatment, very hard, very strong quite brittle
  • Spheralite and Banite - Useful industrially but we can't make them here
Need to know the basics of how steels respond to heat in order to know how to work
Critical Temperature
  • Is at least 727ºC and can be more depending on %age carbon
  • Steels are generally magnetic below critical and non-magnetic above it.
  • Steel is formed above critical temperature and plannished below it.
  • Magnet can test for critical but learn to use colours
  • Other alloys can have different critical temperatures
    • Bronze is much lower
    • Stainless steel is higher
    • Damascus steel is much higher
Vital concept for forging
Hot hardness Is a measure of how easy to forge the material is, small changes in composition can cause large changes in hot-hardness Key concept in working with different steels.
Heat treatment processes
  • Annealing
    • Heat slowly to above critical temperature
    • Soak till even temperature
    • Cool as slowly as possible, either in vermiculite or in the furnace
    • Results in a soft steel that's cold-workable
  • Normalizing
    • Heat slowly to above critical temperature
    • Hold it there for some time, time depends on thickness and your patience
    • Cool reasonably slowly
    • Relieves stress and lowers risk of cracking subsequent treatments
    • Not all steels can or should be normalised
  • Hardening
    • Heat to specified hardening temperature
    • Quench in air, oil, water or brine according to specification sheet
    • Leaves steel very hard and very brittle
    • Too slow cooling leaves metal soft, too fast will crack it
  • Tempering
    • Heat to temperature and time specified in datasheet
    • Reduces brittleness in hardened steels to make them useable
Basic ways to change the properties of steels
Heating Errors
  • Working a steel too cold - Very hard work and risk of cracking
  • Working a steel too hot - Hard to control and risk of crumbling from hot-shortness
  • Overly oxidising flames - Lots of scale and risk of decarburization
  • Overly reducing flames - Poor heat, Carbon monoxide risk, case-hardening, but unlikely to ever happen in our furnace
Knowing the serious errors and how to avoid them


Practical Forging

Welding onto the dop rods

 Emphasise use a LOT of weld material
Need to normalize the welds
They are GOING to break, what to do when they do
 Watch for starting of cracks
 DO NOT TRY TO CATCH THE HOT METAL
 Pick it up IMMEDIATELY with grips, place onto hot-safe surface



Lighting the forge

Describe the forge and it's parts
       How the tunnel can be opened longer for bigger objects
Never use brick choke and rear door at the same time
Check it over for damage
Vacuum out tunnel – clean before use, not after
Plug it in!
Checking the gas & air valve positions are closed
Start the blower
Let a little air into the forge
Cover the dramatic differences in gas and air settings
Turning on gas at the bottle and burners
Opening the main gas valve and using the lighter to get it lit
Adjusting the gas and air valves to get a flame the right size and slightly reducing
Demonstrate high/low, oxidizing/reducing, show what they look like
       Large flames are more stable, small flames may result in burner over-heat, check this often
       Demonstrate high/low flames
Starting up the second burner if you have a need to for a long object


Normalizing

Why we need to normalize
What it does
Proper procedure
What happens if we're not hot enough, or too hot!


Flattening out the rod

Heating to a suitable colour, testing with magnet if you need to
 Just getting the feel of beating on the metal, try both hammers, see what it's like
Don't touch metal to anvil till you're ready to strike
Correct any error immediately, don't let them grow
Consider the shape we're working towards
The need to come to both dimensions at once and not over-work in one direction
We can't fix over-thinning
REMEMBER TO CORRECT ERRORS AT ONCE
Looking at the metal as it cools, seeing what needs to change
Drawing out using small hammers, large hammer on step, large hammer on side, edge of large hammer
Cycling draw out and flatten
Keep thinning, flattening, drawing out till target shape
Try to get the surface nice, so we can do less grinding

Normalizing

Repeat the normalization cycle
Furnace cooling as an option for normalization but not annealing

Shut down the forge

Air off – Gas off – Air on
Leaving the air running to cool the forge if needed
The forge may stay hot enough to start fires for up to 2 hours
Marking out the area of "hot things" when leaving

Normalize and Anneal

This is the last chance to smooth out any gross surface defects or geometry errors
Using a little less heat than before as we're not trying to cause bulk movements
Planishing using the smaller hammers to smooth things as best we can
Normalize for at least 2 cycles and maybe more
Fix geometry before cycles
Using the vermiculite to slow down cooling to achieve maximum softening or furnace cool


Shutdown and clean up

Shutting down the forge

As before for shut-down
Letting the forge cool down enough before putting it away
Hand-in-tunnel test
Don’t try to clean inside the tunnel, put it away dirty
Watching out for condensation dripping off the gas bottle
Getting the blades out of the vermiculite and cleaning up.