THE BRAVE NEW WORLD OF WELDING…

When we hear the word welding we usually think of sparking and a dude wearing a pair goggle. but hey,, let me  blow your misconceptions by introducing you to the brave new world of welding..  here are some new welding process

  1.   ULTRASONIC WELDING:  It is the method where ultrasonic frequencies (higher than 20 kHz)  are applied on the metal so that oscillation shear stress result in a smooth  weld. The vibrations and pressure cause movement of the metal molecules breaking up the surface oxide thus the two surface diffuse into each other . IT TAKE LESS THAN A SECOND TO WELD.  (!!HOW COOL IS THAT)

     ULTRASONIC WELDING

    ULTRASONIC WELDING

  2. FRICTION WELDING:  This type of welding process where coalescence is produce  by rubbing the metal on each other. here how it is work ; the two metal piece to be weld are taken and one is hold in a fix jaw while the other is rotated at a high Rpm and when the moving metal touch the fixed metal due to friction between their faces result a high temperature zone thus welding take place.

    FRICTION WELDING

    FRICTION WELDING

  3. EXPLOSIVE WELDING:  IT IS ALSO CALLED PIRATE WELDING….as it is produced by using explosive powder. first of all the the powder is spread on the surface of the metal piece then below this piece another piece is placed to which this piece meant to be weld. a single detonation cap can be used to detonate the explosive , this type of welding used in bimetallic disc breaks , piston faces etc. where other process are impossible to conduct.

    EXPLOSIVE WELDING

    EXPLOSIVE WELDING

  4. COLD WELDING : It is define as welding process where coalescence is produce by mechanical force alone . since it is carried at room temperature the bonding of molecules may not be very strong.

    AT ISS ASTRONAUT USE COLD WELDING

    AT ISS ASTRONAUT USE COLD WELDING

  5. ELECTRON BEAM WELDING  : As the name suggest this type of welding uses high energy electron beam to weld the piece , the high speed electron collide with the metal to give away their energy into heat thus melting a specific spot (UP TO 2200*C) it can weld from 1 meter away from the workpiece.

    SCHEMATIC DIAGRAM OF EBM

    SCHEMATIC DIAGRAM OF EBM

  6. LASER BEAM WELDING: many people confuses it from the electron beam welding but its is different from that it has a greater accuracy and uses a entirely different principal and setup of working. it uses ruby LASER and xenon or krypton gas to operate. It is uses for thin material where  micro clear welding is required.

    LASER BEAM WELDING

    LASER BEAM WELDING

  7. NUCLEAR WELDING : This welding is uses  to weld plastics like polyethylene, crystal like quartz etc. the work piece are irradiated with  stream of neutrons    the surface to be weld are bombarded with these elements and nuclear reaction take place.
  8. INFRA RED WELDING : In this type of welding the heat is supplied by a source  infra red light, such as a sylite glower, a chrome steel is carried out on a black plate of formed plastic, sponge rubber or thick rubberized fabric. This process is used to join polyethylene films.
    INFRA RED WELDING SETUP

    INFRA RED WELDING SETUP

    SO FRIENDS.. this is the end…. for any queries ask me in the comment section . I write blogs every week..follow me for more info..LATER 🙂

What are cupola furnaces????

Hi THERE I am here again for your help  to your high school, college   assignments. Today we going to learn about the oldest furnace technology used in

Today we going to learn about the oldest furnace technology used in foundry.

THE CUPOLA

SCHEMATIC DIAGRAM OF CUPOLA

SCHEMATIC DIAGRAM OF CUPOLA

  • The most widely used furnace in the foundry for melting ferrous and non-ferrous metal and alloys. a cross section of a cupola is shown .
  •   A cupola is a shaft furnace of cylindrical shape erected on legs and columns . The     cupola shell is made of steel plate 8 or 10mm thick.
  • The interior is lined  with refractory bricks to protect the shell from overheating.the charge consist of fuel(coke as anthracite) fluxes(limestone used for decontamination of charge) and material (pig iron,scrap etc.)
  • Charging is mechanised by drop bottom buckets.
  • Air for combustion deliver through blowers. and enter into a chamber called wired box.
  • At the top of cupola there is there is a spark arrester to catch the incandescent dust and gases.

TUYERS are important part in cupola , they are the openings which extend through steel shells and refractory wall to the combustion zone.

    • A tap hole is provided to take out the molten metal.

A VIDEO FOR BETTER UNDERSTANDING 

DIMENSION OF CUPOLA

Cross section area of cupola is equal to:

A=   π *d^2 /4 =Q/Q1

d=clear diameter of cupola

Q=designed cupola output (in tonnes per hour)

Q1= specific output of the cupola (in tonnes per sq-m per hour)

As a rule = Q1=6 to 8

The cupola height is 3-5 times the diameter.

Height affects the melting rate , fuel consumption, and quality of molten metal

if too much height then coal is crushed under self weight.

if too small then molten metal is not heated properly thus reducing the output also.

Common dimensions are

OUTER diameter : 900-2700mm

INSIDE diameter :  500-2100 mm

HEIGHT : 12 m

FOR various  purpose design charts is shown

DESIGN SPECIFICATION OF CUPOLA

DESIGN SPECIFICATION OF CUPOLA

Various heat zone in cupola

  • COMBUSTION zone   :      The highest temperature developed in cupola furnace is in    this zone.                                                                                                                 1600-1700*C the reaction is exothermic :    C + O2 ———-> CO2  + HEAT
  • REDUCING zone: it’s above combustion zone up to height of initial coke bed.

The CO2 flowing upward reacts with  the hot coke  and reaction is  endothermic.

This zone application is to protect the metallic charge from oxidation due to its reducing

nature,    CO2 +   Coke —————> 2 CO(reducing agent)   – heat.

  • MELTING zone: This zone includes the first layer of iron above  the coke bed.

In this zone the charge starts to melt.

Also iron carbide formation take place.

3Fe   + 2 CO ————–>    Fe3C  +   CO2

  • PREHEATING ZONE: In this zone moisture,volatile materials are evaporated and the layers of charge are heated by outgoing gases and temperature here is about 1090*C.
A MICRO CUPOLA

A MICRO CUPOLA

IF YOU HAVE SOME QUESTION ASK ME IN COMMENT SECTION BELOW.

I AM ALWAYS HERE AS YOUR ASSIGNMENTS BUDDY……;)

Powder metallurgy: Atomization and chemical reduction

1.  Manufacture of Metal Powders
Atomization is the process used commercially to produce the largest tonnage of metal powders.  In water and gas atomization (Figures 2-1 and 2-2, respectively) the raw material is melted then the liquid metal is broken into individual particles.  To accomplish this, the melt stock, in the form of elemental, multi-element metallic alloys, and/or high quality scrap, is melted in an induction, arc, or other type of furnace.  After the bath is molten and homogenous, it is transferred to a tundish which is a reservoir used to supply a constant, controlled flow of metal into the atomizing chamber.  As the metal stream exits the tundish, it is struck by a high velocity stream of the atomizing medium (water, air, or an inert gas).  The molten metal stream is disintegrated into fine droplets which solidify during their fall through the atomizing tank.  Particles are collected at the bottom of the tank.  Alternatively, centrifugal force can be used to break up the liquid as it is removed from the periphery of a rotating electrode or spinning disk/cup (Figure 2-3).

Figure 2-3         Figure 2-3

Here is a video link for better understanding:

Additional alloying can be performed in the liquid metal bath after the original charge has become molten.  Also, the bath can be protected from oxidation by maintaining an inert gas atmosphere as a cover over the liquid metal.  Alternatively, the top of the furnace can be enclosed in a vacuum chamber.  The furnace type and degree of protection are determined by the chemical composition of the bath and the tendency of the metal to oxidize.
These manufacturing techniques result in powders with different characteristics and appearance, for use in specific applications (Figure 5).  Water atomization usually produces irregularly shaped particles free of internal porosity, whereas the shape of gas atomized particles is spherical, also without internal porosity.  Metal powders produced by oxide reduction are irregular in shape, have a large surface area, and usually contain a substantial amount of internal porosity.  Particles fabricated by milling or other mechanical methods exhibit a spectrum of shapes, depending on the relative ductility or brittleness of the feed material.  Ductile powders are generally flat with a high aspect ratio whereas brittle particles can be angular and regularly shaped.  The milling of agglomerated particles can cause the agglomerates to break up, sometimes with little effect on the shape of the individual particles.  Powder particles produced chemically can have shapes ranging from spherical to angular.  Electrolytic powders are of high purity with a dendrite morphology.

ATOMIZER

Figure 5: Representative Metal Powders: (a) Chemical; Sponge Iron-Reduced Ore; (b) Electolytic: Copper; (c) Mechanical: Milled Aluminum Powder Containing Disperoids (17); (d) Water Atomization : Iron; (e) Gas Atomization: Nickel-Base

Figure 5: Representative Metal Powders: (a) Chemical; Sponge Iron-Reduced Ore; (b) Electrolytic: Copper; (c) Mechanical: Milled Aluminum Powder Containing Disperoids (17); (d) Water Atomization : Iron; (e) Gas Atomization: Nickel-Base

Chemical reduction.

  • It involves chemical reaction generally a halide or oxide. This may be carried out
  • SOLID STATE: Reduction of iron oxide with carbon and tungsten oxide with hydrogen.
  • THE FORMATION OF SPONGE IRON
    By Hoganas process:
  • The batch does not move in the process .
  • Quite pure iron ore (fe304) used with carbon and limestone.
  • Contain in cylindrical ceramic container(silicon carbide).
  • Total reduction time is 24 hours and 1200 *C .
  • Limestone used to uncontaminated the sulphur from iron ore. so that pure iron can be obtain.

TUNGESTON POWDER

  • The ore of tungsten is wolfermite(FeWO4) and scheelite(CaWO4)
  • The ore is mixed in Hcl to form tungestic acid.
  • Tungestic acid is mixed in ammonia to form APT (ammonium paratungastate)
  • APT calcined to give blue oxide.
  • Blue oxide and caustic soda are mixed to give tungsten ppt as Wo3.
  • At 850*c reduction take place and the hydrogen used should be 99.4% pure to give high quality powder.


chemical reduction chamber

chemical reduction chamber

Picture4