This document summarizes the furnace process used to heat treat and coat wire or rod. It describes three main processes: patenting, galvanizing, and phosphating. The patenting process involves heating the wire to austenitizing temperatures then quenching in lead bath to increase strength and ductility. The galvanizing process uses molten zinc to apply a protective zinc coating. The phosphating process creates a phosphate coating on the surface to prevent corrosion through a phosphate bath. The overall furnace process involves paying off the wire, heating, quenching or coating processes, rinsing, and taking off the finished wire.

1. Prepared By – Kuldeep Chauhan

2. BASIC ABOUT FURNACE PROCESS – As the name is stating FURNACE, so
it is stating that some heat treatment in this process. A furnace is a piece of equipment that
provides direct electric or fired heat for industrial processes that require higher range of
temperatures. We are using Patenting Heat Treatment furnace.
In furnace we are doing 3 processes as per our product requirement –
1. Patenting. - Heat treatment to increase strength & ductility of material.
2. Galvanizing - Zinc coating to avoid corrosion to the material.
3. Phosphating - Phosphate & Borax coating to avoid corrosion & better drawability.

3. PAY OFF (INPUT)
HEATING
ZONES
LEAD
BATH
HCL BATHS
WATER
RINSE
PHOSPHATE
COATING
SAND
WIPING
WATER
COOLING
WATER
RINSE
DRYER
BORAX
COATING
TAKE OFF (OUTPUT)
FLUX BATH
DRYER
ZINC BATH
CHARCOAL
WIPING
WATER
COOLING
PATENTING PROCESS
GALVANIZING
PROCESS
PHOSPHATING
PROCESS
BASIC PROCESS FLOW OF FURNACE-

4. 1. PATENTING PROCESS -
Basic about Patenting – Patenting is basically a “Isothermal Phase Transformation Process”. It
involves the rapid cooling of a metal to adjust the mechanical properties of its original state. To
perform the patenting process, wire or rod is heated to a temperature (Austenite Temperature) greater
than that of normal conditions, typically somewhere above its recrystallization temperature but below
its melting temperature and then sudden cool it at a appropriate temperature (As per product
requirement).
Need of Patenting – When wire or rod drawn, it deformed to plasticity form and it takes new shape,
new dimension and new grain structure. But additionally they get hardened. Which means UTS and
hardness goes up and ductility goes down. This is where the “Patenting or heat treatment” comes in the
picture. Patenting increase the ductility & strength of patented wire or rod by phase transformation
process for further drawing purpose.
Basic Process of Patenting – It is a unique process and depends upon time & temperature. So for
proper phase transformation time is very important and sufficient time has to be given at a constant
temperature. Since the phase transformation take place at constant temperature, it is known as
“Isothermal Phase Transformation Process”.

5. Basic Components of Patenting – Good quality patented wire can be obtained by good
patenting process.
a. Pay Off (Inlet)– Pay off is inlet feeding to furnace. We are using vertical Payoff that
equipped with rotating table with brake cord to control the speed of wire or rod.
b. Heating Zones – Heating zones use to heat the wire or rod upto austenitizing temperature
(850°C to 950°C). Basically heating zones designed in three steps to achieve uniform
austenitizing temperature –
• Preheating Zone – are initial zones to preheat the wire or rod.
• Heating Zone – are mid zones to heat the wire or rod at high temperature.
• Soaking Zone – is last zone to achieve uniform austenitizing temperature on the wire or rod.
Heating zones are design as per running average size and speed to achieve austenitizing
temperature at wire/rod in soaking zone during exit of wire/rod. Zones are equipped with
number of burners as per temperature requirement. Fire generates in in the burner with the firing
of fuel(LNG/LPG) & air mixture. Diaphragm are in use to control the air & fuel mixture.

6. c. Lead Bath – Just after heating zones, there is a lead bath. Lead is being used for patenting
(Quenching) process. As a principle of quenching process, “Rapid cooling of a work piece in
water, oil, polymer, air or other fluid to obtain certain material properties.” In high carbon
wire/rod patenting process, lead is being used for patenting process. Lead bath temperature is
545°C for good mechanical properties of patented wire/rod.
Wire/Rod comes from austenitizing temperature (850 - 950°C) and dip in lead bath at 545°C
temperature to obtain good mechanical properties as well as good strength & ductility.
d. Sand Wiping – Sand is use to wipe the molten lead from the surface of wire or rod.
e. Water Cooling – Water cooling is use to normalize the temperature of wire or rod before
entering in HCL baths.
f. HCL Baths – Two HCL baths are being used in furnace with different HCL concentration
(First bath with Low & second bath with High conc.). After heat treatment there is scale
formation on the surface of wire/rod due to oxidation. So to remove the scale from the
surface of the wire/rod it pass through the HCL baths.

7. It is known as Inline Pickling Process. Surface cleaning is must for the further Phosphate &
Zinc coating process.
g. Rinse Water – After HCL bath, rinse water baths use for cleaning of HCL from the surface
of wire/rod for further coating processes. Rinse water pH maintained between 5-7 for better
surface cleaning.
2. GALVANIZING PROCESS –
Basic about galvanizing – Galvanizing is a process of applying a protective zinc coating to
steel or iron, to prevent rusting. In this process 99.99% pure zinc plates use for coating.
Basic component of Galvanizing Process – Below are the basic components of galvanizing
process –
a. Flux – Flux is use before zinc coating to prepare surface for the metallurgical phase by
applying a saline layer that facilitates Iron-Zinc bonding. Galvanizing flux consists mainly two
chemical components Amonium Chloride & Zinc Chloride. It mix with the water at a specified
gravity and temperature range.

8. b. Zinc Bath – Zinc plates melt with the help of burner in zinc bath for zinc coating process.
Molten zinc temperature keeps 455°C for proper zinc coating. Flux clean wire/rods dip in
the molten zinc for zinc coating at different dipping lengths as per coating thickness
requirement. Coating process conduct at a high temperature so it is also called “Hot dipped
Galvanizing Process”.
c. Charcoal Wiping – It is a process to wipe the excess zinc to get the smooth surface of
wire/rod. In this process dry charcoal powder mix with the oil and spread at the exit of the
wire/rod from zinc bath.
d. Water Cooling – At final galvanizing process water is use to cool the wire/rod and also to
clean the surface of wire for any charcoal stain.
e. Take Off – Take Off are the final output of furnace. In takeoff, wire/rod are collected in
bobbins or farma with the help of winding process.

9. 3. PHOSPHATING PROCESS –
Basic about phosphating - Phosphating is a chemical method of surface treatment in which
a metallic surface reacts with an aqueous phosphate solution.
This creates a hardly soluble conversion layer made of metal phosphates. For this purpose,
the material is first cleaned with acid and then the phosphate layer is formed. Phosphate
coating is use to prevent the wire/rod from corrosion.
Basic component of Phosphate Process – Below are the basic components of Phosphating
process –
a. Phosphate Bath – It is use for doing phosphate coating process. It consists phosphate
solution at specified TA & temperature range. Phosphate basically a solution of
Phosphoric Acid that reacts with wire/rod surface to make a protective layer.

10. b. Rinse Water – After Phosphate bath there is water bath use for cleaning of wire surface for
further coating process. For better surface cleaning, water pH keeps between 5-7.
c. Borax Bath – It is use for borax coating on wire/rod surface. Borax coating is used to
neutralize any acid residues on the wire and improve the pick-up of the dry drawing
lubricant in further drawing process.
d. Dryer – Dryer is use to dry the borax coated wire/rod to avoid any moisture content.
e. Take Off – Take Off are the final output of furnace. In takeoff, wire/rod are collected in
bobbins or farma with the help of winding process.
Three types of wires produced in furnace process –
Phosphate Coated Wire – PWLC (Patented Wire Lead Cooled).
Zinc Coated Wire – LCG & DWG (Lead Cooled Galvanized Wire & Drawn Wire Galvanizing).