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welding pit

Discussion in 'General Electronics Discussion' started by tnnelectro, May 27, 2020.

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  1. tnnelectro


    Apr 5, 2012

    I want to make a welding pit, dimensions 22cm X 11cm X 3cm in stainless steel

    As a heating element I have this resistance of Kanthal, to be wrapped around the welding pit ... while as insulation using glass wool or ceramic fiber.

    If I use 30mt of 1.2mm thickness resistance with 1.19Ω / m I get about 1480Watt of power ... can it be enough to bring the pond to 400/450 ° C ???

  2. duke37


    Jan 9, 2011
    Do you mean a soldering bath? Welding means that the components are melted at the join. See stick, Mig, Tig.
    The resistance wire must be electricaly insulated from the pot. How will you do this? Perhps a cooker element under the pot would work.
  3. Alec_t


    Jul 7, 2015
    I think a soldering bath is intended. Most solders, even high temperature ones, melt below 300°C, so why do you want the bath at 450°C?
  4. tnnelectro


    Apr 5, 2012
    welding crucible
  5. duke37


    Jan 9, 2011
    I have bought items from China, described as welded when they mean soldered.
    Welding involves melting the two parts, with the possidility of a filler of similar material.
    Soldering involves adding a low temperature alloy to join the pieces. The workpiece is not melted but it may be slightly dissolved if not done quickly. Copper and silver are soldered with an alloy of tin and lead, sometimes lead free.
    Brass can be soldered with lead based solder but for higher strength usully uses silver solder.

    So, you do NOT mean welding.
    What country do you come from which uses 'welding' incorrectly?
  6. bertus

    bertus Moderator

    Nov 8, 2019
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    To solder in Italian is afaik "brazare", the online dictionaries give "braze" as the corresponding translation.
    400 ... 450 °C are good for melting solder, few metals will melt at or below this temperature:
    • Phosphorus
    • Tin
    • Bismuth
    • Cadmium
    • Lead
    • Zinc

    Most (all?) others will require temperatures above 600 °C.

    On the other hand: 22cm X 11cm X 3cm is rather big for a solder bath.

    What do you want to do?
  8. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    What!? Are you kidding? They NEVER tell us what they want to DO without at least twenty or fifty posts, none of which are relevant to what the OP is trying to DO. It's like they have been sworn to secrecy, or are afraid someone will steal their "Big Idea" before they can make big bux making and selling it with our (unpaid) help.

    So, welding crucible or solder pot or piss pot... who gives a fig when all of these are readily available? Perhaps the OP should learn how to make Google their best friend to help find whatever they need to DO whatever it is they need DONE.

    BTW, check out the Google results link that @bertus gave in post #6. Fascinating results ranging from artful welding to welding railroad tracks and lots of "stuff" in between, including a few electrically heated solder pots.

    My grandfather used to melt lead to pour into molds containing fish hooks. After the lead cooled, he would open the mold and remove the lead-embedded fish hooks, to which he would then attach, with thin nylon string, all manner of lures that (he hoped) would entice fish to take a bite. To finish the lures off, he would paint them (the lead part) with whatever colors suited his fancy and seal everything with clear fingernail polish.

    NO ELECTRICITY was involved in melting the lead. Instead, he had a gasoline-fueled blow-torch with an attached hand-pump that he would fire up to directly heat and melt the lead in a steel ladle supported on a piece of fire-brick. It took several minutes for the blow-torch to "get up to speed" and today we would probably use propane or MAPP gas instead of gasoline, but grandfather was very "old school," like nineteenth century old school.

    Martaine2005 likes this.
  9. davenn

    davenn Moderator

    Sep 5, 2009
    brazing is a different process to soldering in that it isn't used for electronics and it uses high temp. and focussed gas flame and uses different filler materials
    Have done lots of that in years go by for repairs on cars
  10. Martaine2005


    May 12, 2015
    Google translate says “soldare”.
    Sal-da- re
  11. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    I'm aware of this, but asking costs (next to) nothing.
  12. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Yes, of course you are right. And if we DON'T ask, it could be they won't tell us... ever.

    A few years ago the surface engineering laboratory in which I worked was applying a micrometer-thin film of a proprietary coating to the core pins of injection molding dies used to manufacture automobile engine aluminum cylinder heads... the big metal thingy on the top of an internal combustion engine that seals the tops of the piston cylinders and contains the spark-plug and intake and exhaust valves. Cylinder heads were traditionally made of cast steel, but aluminum has its advantages, being lighter and having better heat transfer characteristics than steel, among other things. Core pins are used to create small cylindrical holes in the cylinder heads, holes that are typically used to pass bolts through when the head is assembled to the engine block. The core pins are made of a highly polished steel alloy and pass through both halves of the die to create the holes that will appear in the injection-molded aluminum.

    Problem is, steel and aluminum don't play well together. The aluminum tends to dissolve and adhere to the surface of the steel. This can cause a big problem when it is time to separate the molding die into its two component parts. If the core pin is coated with aluminum after the mold cools enough to be opened, it can prevent the molding die from separating. This shuts down the production line until the stuck die pin can be removed from the die and replaced. The proprietary coating is designed to prevent the molten aluminum from adhering to the steel core pin. Naturally, the customer didn't want to just take our word for it that our (moderately) expensive proprietary coating would increase the up-time of their aluminum injection molding process and literally pay for itself. Their "bean counters" wanted some experimental evidence, and our surface engineering laboratory wanted to know how well certain variations of our proprietary coating lasted. So... I was tasked with the design and construction of a machine to perform a test.

    A sample steel rod of the same general diameter and exactly the same alloy and polished surface finish as a real core pin was inserted into a collet mounted to a vertical linear slide, which in turn was mounted to a longer horizontal linear slide. Both slides were connected to pneumatically actuated pistons. At one end of the horizontal slide was an electrically heated oven with a crucible of molten aluminum. At the other end of the horizontal slide was a large open container of water. The vertical slide was used to dip the sample steel rod into the molten aluminum for a certain period of time and then withdraw the rod. The horizontal slide then positioned the sample steel rod over the container of water. The vertical slide was then used to dip the now hot sample steel rod into the container of water for another certain period of time, to quickly cool it, and then to withdraw the rod. The horizontal slide then positioned the sample steel rod over the aluminum crucible and the process just described was repeated.

    All of the parts for this test apparatus were "commercial off-the-shelf" (COTS) components. I designed and built a cylindrical furnace to heat the crucible that held the molten aluminum. I tried using a steel crucible initially, but the molten aluminum dissolved the bottom out of it, creating somewhat of a mess. So I switched to a ceramic crucible and everything worked fine after that. The pneumatically actuated linear slides used Hall-effect sensors to detect the limit positions, left/right and up/down. An inexpensive, French, programmable logic controller (PLC) implemented the test algorithm, and a PC tied it all together by acting as the data acquisition system and programming device for the PLC. I built a "spiffy" control panel with a COTS temperature controller for the oven and manual switches to allow the linear slides to be tested. The switches didn't actually control any hardware: they served as binary inputs to the PLC whose program decided how to respond to switch actuation.

    I didn't have any experience building electrically heated furnaces, but I did know two things: the furnace needed to be well-insulated if there was to be any hope of reaching molten aluminum temperatures, and the outside of the furnace needed to be cool to the touch for safe operation. To solve the insulation problem I ordered a high-temperature insulating material that could be cut and shaped with a saw. We made annular rings and stacked them up around the outside of the oven heating elements. Then I made a coaxial cylinder around the outside of these rings, attached to the aluminum plate bottom of the apparatus. Slots machined in the bottom plate allowed air to flow into a plenum mounted below the bottom plate, exhausted by a squirrel-cage fan. Thus cool air would flow into the top of the coaxial cylinder (which formed the outer wall of the furnace) and be drawn into the plenum by the fan and exhausted underneath the apparatus to the room. All the furnace components, including the Type K thermocouple and temperature controller, were COTS items available from Omega Engineering. Not exactly cheap, but readily available and reliable.

    So here's hoping that @tnnelectro has as much success and fun building their stainless steel "welding pit" or "welding crucible" or whatever it is he or she is trying to do as I did building my little molten aluminum test rig. As for how much power is needed to reach any given temperature... that depends on how much power is wasted in radiation, conductive, and convective heat losses. It would be a good idea to learn some thermodynamics, or as @(*steve*) says: it's not just a good idea, it's the law!
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