Tips for Welding Austenitic Stainless Steel

Tips for Stainless Steel

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Tips for Welding Austenitic Stainless Steel

Stainless steel is the type of high alloy steel with at least 11.5% Chromium. Iron content exceeds that of any other element. Carbon is generally less than 1.5%.

Properties of Stainless Steel:

    • Mechanical Properties: Compared to other materials, stainless steel has strong mechanical properties at ambient temperatures, In particular, it combines ductility, elasticity, and hardness, In addition, it offers good mechanical behavior at both low and high temperatures. So widely used in all Industries.
    • Oxidation Resistance: Stainless steel has the best resistance of all metallic materials when used in structural applications, having a critical temperature above 800°C. Grades of Stainless steel can be used for Sub-zero temperatures.
    • Corrosion Resistance: With a minimum chromium content of 10.5%, stainless steel is continuously protected by a passive chromium oxide layer, This special feature gives stainless steel its resistance to corrosion.
    • Versatility: Stainless steel has a wide variety of finishes, from matte to bright, including brushed and engraved. It is widely used by architects for building envelopes, interior design, and street furniture.
    • Easy Maintenance: Stainless steel objects are easy to clean, and common cleaning agents.
    • Environment friendly: Stainless steel is the “green material” and is infinitely recyclable. It is environmentally neutral and inert when in contact with elements like water, and it does not release compounds that could change their composition.

Types of Stainless Steel Used in Industry:

  • Austenitic  Non-Magnetic & work Hardening 
  • Ferritic Soft & Magnetic 
  • Martensitic  Magnetic & Hard
  • Duplex Magnetic & Wok Hardening 
  • Precipitation Hardening

Problems in Welding Austenitic SS:

  • Carbide Precipitation or IGC 
  • Heat of Welding 
  • Porosity
  • Contamination

Carbide Precipitation or Inter Granular Corrosion:

The major problem encountered in welding austenitic stainless steel is intergranular corrosion or carbide precipitation.

  • When welding Austenitic SS  between 420 to 880 deg. C base metal temperature also known as “Sensitisation Temperature”  a large volume of Cr is picked  in the grain Boundaries of the HAZ area
  • This forms Chromium Carbide which precipitates and forms at grain boundaries –the area adjacent to the HAZ area
  • So on working condition or in service, the HAZ area starts corroding at a faster rate as this area cannot form Cr2O3 due to Cr depletion 
  • This phenomenon is called Inter Granular Corrosion or Carbide Precipitation

Remedies:

  • Controlling the carbon content (0.03% or below)
  • Addition of Carbide stabilizers like Ti, Nb.
  • Heat Treatment (Solution annealing).
  • Controlled welding below 450 Degrees 

The heat of welding:

  • Cracking from the HAZ area
  • Loss of Corrosion Resistance 
  • Warping or Distortion of Material 
  • Loss of Mechanical Properties 

Porosity :

  • This is caused by Dirt, Grease & marking material 
  • Poor Quality of Flux coating 

Contamination:

  • Contaminants in SS like Sulphur, Carbon, Iron, Copper & lead is the root Couse of failure of welded joints and also poor corrosion resistance 

 Remedies: Do’s for Welding Austenitic Stainless Steel: 

  • Rigid Fixturing with more tack welds
  • Sequence welding to control heat 
  • Baking of electrode 200 deg –one hour before welding.
  • Proper Cleaning of weld area before starting the job 
  • Use short arc & low heat Input Welding Electrodes 
  • Use Correct or optimum diameter electrode during welding 
  • Clean slag after every pass / between passes.

Hence with these simple strategies, we can weld all applications of austenitic stainless steel.

We at Ador Fontech have designed & developed this exclusive range of LH- Low heat Input Welding Electrodes, TIG & MIG wires for welding of all types of stainless including austenitic stainless steels.

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Tips to Weld Cast Iron

 Cast iron can be described as a wide variety of iron-based materials containing Carbon of 1.7%-4.5%

types of weldable cast ironIt also contains Silicon- 0.5%-3%, Manganese-0.2%-1.3%, Phosphorous-0.8% max & Sulphur -0.2%max. The major distinguishing feature between steels is carbon content, it has maximum influence on the property of CI. A low percentage promotes the formation of hard white cast iron & higher percentage promotes the formation of grey cast iron.

Properties of Cast Iron:

  • Hardness: Cast iron is hard and it can be hardened by heating and sudden cooling. This makes it quite durable.
  • Melting Point: Cast iron has a lower melting point (1200 deg. C) as compared to the melting point of mild steel which lies in the range of 1300 deg. C and 1400 deg. C.
  • Castability: Cast iron is easier to cast when it comes to casting shapes out of the material. Due to the extra carbon & silicon present in cast iron, its molten form is more fluid and this makes it easier to cast the material into complex shapes.
  • Machinability: Cast iron is almost elastic up to ultimate tensile strength and produces discontinuous chips which break away from the sample easily. This helps to improve the cutting ability. Due to this, cast iron is the preferred material when it comes to high machinability and strength.
  • Highly porous hence it can be used in machine bases etc. as it provides good self-lubrication properties as oil & grease remain in the porous mass of cast iron.
  • It’s Porous and sponge-like structure means it can be used in machine bases as it has good damping properties 

Types of Cast Iron Used in Industry:

  • Grey Cast Iron
  • White Cast Iron
  • Chilled Cast Iron
  • Nodular Cast Iron
  • Malleable Cast Iron
  • Alloyed Cast Iron

Depending on carbon content and the procedure it is manufactured and these are common grades used in industry.

Problems in Welding Cast Iron:

  • CI is Brittle, so it tends to crack easily 
  • Porous & Contaminated so cleaning is very tough 
  • Too much Carbon tends to crack during welding 
  • Lesser Heat Conductivity, so heat dissipation is fast 
  • Carbon Pick up in the weld metal will be there leading to cracks in the HAZ.

Techniques to Weld Cast Iron.

Considering the above problems in cast iron, there are two methods or techniques to weld cast iron.

  • Hot Technique
  • Cold Technique

Hot Technique:

  1. Preheat the cast iron component to 350 deg. C – 400 deg. C
  2. Do the welding at the same temperature, ensure the temperature is maintained above 350 deg. C during the entire process of welding
  1. Slow cool the welded component by gradually cooling the component, if the job was done with heating cold reduce 50 deg. C per hour for per inch thickness of the job, If done in a furnace switch off & allow it to cool.

Cold Technique

Limit heat input in the cast iron welding  job by adopting the following methods :

  • Low current: Use low heat input welding electrodes & use lower diameter and lower amperages.
  • Stringer bead: Strictly no weaving during welding use only stringer beads
  • Short arc: Use arc length less than the diameter of electrode, preferable touch & weld type LH products 
  • Short bead length: Weld not more than 25 -30mm bead length only, always weld with a job on hand heat 
  • Peening: Hot peening with the ball-peen hammer is recommended for removing any residual stress in welding.

For welding of all weld-able grade cast iron, Nickel-based electrodes either pure nickel or Ferro-nickel type electrodes are used depending on the application requirements.

ador fontech

We at Ador Fontech have designed & developed this exclusive Range of LH Low heat Input Welding Electrodes for welding cast iron using both welding techniques required for cast iron welding  

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Steel : Types of Steel and its Weldability

One of our most important manufactured products used in all industries has many applications & uses. Steel can be molded, pressed, machined, welded & woven to suit different purposes.

Steel making:  It’s a three-step process.

Types Ador

  1. Iron Making: Iron ore, coke & a flux (limestone) are combined in a blast furnace to produce molten iron containing about 4% carbon.
  2. Steel Making: Excess carbon is removed in a basic oxygen steel making vessel and the required alloy is added. The molten steel is then cast into billets, blooms, or slabs.
  3. Shaping: Steel is rolled to various sizes and shapes in a rolling mill.

Steels are basically a wide range of iron-based alloys with carbon up to 1 .7 %.

  • In plain carbon steels other elements are silicon (up to 0.6%), manganese(up to 1.65%), sulphur (up to 0.35%) & phosphorous (up to 0.13%).

      1. Elements in Steel: 

  • Carbon 
    • Up to 1.7 %
    • Promotes formation of carbides (cementite, pearlite & martensite)
  • Manganese
    • Deoxidizes the metal and facilitates hot working
    • Neutralizes sulfur by forming manganese sulfide which increases strength
    • Provides work-hardening property
  • Silicon
    • Deoxidizes steel
    • Increases resistance to scaling
  • Phosphorous
    • An impurity
    • Decreases ductility and toughness
  • Sulfur
    • An impurity
    • Decreases strength and impact resistance
    • Improves machinability

     2. Types of Steel :

  • Low Carbon Steels
    • Carbon up to 0.3 %
    • Good ductility & weldability
    • Comparatively low strength & not easily heat treatabletypes of steel

Welding: Have very good weldability.

No special precautions required

  • Medium Carbon steels
    • Carbon 0.3 to 0.6 %
    • Better strength & hardness than low carbon steel

Welding: Slight preheat around 200-250 deg. C and slow cooling.

 Use a low hydrogen type electrode

  • High Carbon Steels
    • Carbon : 0.6 % to 1.71 %
    • Easily heat treatable to high hardness

Welding: Poor weldability.

                                      Tendency to crack

                                       High preheat around 300 deg. C and very slow cooling

                                       Maintain high interpass temperature-300 deg. C

                       Post weld heat treatment and stresses relieving desirable

  • Alloy Steels

Contain alloying elements other than silicon, manganese, sulfur & phosphorous

  • High Alloy Steels

Alloying elements more than 10 % ( Ni, Mn, Cr)

Welding: High carbon equivalent hence form martensite.

                 Preheat around 300 deg. C and maintain interpass

                 Cool slowly

  • Low Alloy Steels

Alloying elements less than 10 %

           Welding:  Preheat requirements minimum.

                 

Types of High Alloy Steels :

  • Austenitic Manganese steels: 

More than 10 % manganese & high carbon

    • Known as Hadfield Steels
    • Work harden in service

Welding: Forms hard Carbides at temperatures above 175 deg. C.

                 No, preheat and fast cooling

  • Stainless Steels :
    • Chromium minimum 11.5 %
    • Excellent corrosion resistance
    • The addition of nickel gives good toughness & strength at sub-zero and elevated temperatures

Welding: Loose corrosion resistance on exposure over 500 deg. C

                                      No, preheat and fast cooling

                                      Low current & stringer beads

  • Tool Steels:
    • Used as Cutting Tools, Shear Blades, Dies, etc. 
    • Contain high carbon
    • Have a high amount of tungsten, molybdenum, chromium, cobalt, etc., and withstand temperatures up to 550 deg.

Welding: Difficult to weld.

                  High preheat around 350 deg. C & cool slowly

Hence, we at Ador Fontech have designed & developed this exclusive range of LH low heat input welding electrodes, TIG rods & MIG wires to weld all types of steel used in industry, resolving all problems as the unique solution provider for maintenance & repair welding.

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A Complete Guide to Welding

Welding Metals – An Introduction

To join ferrous with non-ferrous metals, various methods can be adopted.

  • Mechanical methods: Fasteners, rivets, etc.
  • Adhesive bonding method: Brazing and Soldering (a.k.a. welding)
  • Base metal does not fuse: Molten filler gets drawn into close-fit joints through capillary action (surface tension forces).
  • Brazing filler melts at >450⁰C, soldering at <450⁰C

Welding is the most commonly used process of all.

Welding – A Definition 

Welding can be described as a process of joining two or more pieces /edges of metal by producing a localized union through heat (fusion) with or without pressure to create a homogenous joint.

Types of Welding by Metal:

Autogenous: In this process, similar materials are joined without filler wire or electrode
Heterogeneous: Process of joining dissimilar materials, using a filler wire or welding electrode

Types of Welding by Method:

1. Fusion Welding (Electrical Energy):

  • Manual Metal Arc welding / Flux Cored Arc welding / Shielded Metal Arc Welding
  • TIG –Tungsten Inert Gas welding
  • Metal Inert Gas welding or Metal Active Gas welding
  • SAW – Submerged Arc Welding

2. Solid-State and other Non-electric Fusion Welding: Examples of non-fusion, non-electric process welding are:-

  • Thermit welding
  • Ultrasonic welding
  • Diffusion welding
  • Deformation welding.

Welding Processes

  • Fusion welding: Welding in the liquid state with no pressure, Union is by molten metal bridging
  • Solid State welding: Carried out below the melting point of the metal without filler additions, Pressure is often used,
    Union is often by plastic flow.

Solid State welding:

DEFORMATION WELDING: Two Surfaces in contact are brought into very close contact by applying high pressure, which deforms them. E.g., – Forge welding, Roll welding, Extrusion welding. (Not at very high temperatures)

 

deformation welding

DIFFUSION WELDING: Joining takes place by atomic diffusion of 2 surfaces in contact. Surfaces are usually heated to high temperatures (below the melting point) & pressure may be employed. E.g., Brazing, Braze welding & Soldering. Soldering is an oxy-fuel process of joining metals. The process temperature does not exceed 450⁰. Brazing is also an Oxy-Fuel joining process. The process temperature is between 450⁰ Degrees – 750⁰ degrees. Braze welding is similar to Brazing; the process temperature is above 750⁰ Degrees but below the melting point of the base metal.

Non-Fusion Process: Thermit welding is the most common process used in joining of railway tracks. In this process iron powders and Al binders are kept in Vat or a conical container above the joining rails. When they are fired due to chemical reaction and exothermic reaction, the iron powder melts and forms a joint between rails.

non fusion process

Introduction to Arc Welding: Basic welding processes used in Industry are

  • MMAW – Manual Metal Arc Welding or Shielded Metal Arc welding
  • GMAW – Gas Metal Arc Welding/ Flux Cored Arc Welding (MIG, MAG)
  • GTAW – Gas Tungsten Arc Welding (TIG)
  • SAW – Submerged Arc Welding

MMAW or SMAW- Shielded Metal Arc process: In the Shielded Metal Arc process or Manual metal Arc welding process the arc is established between Parent Metal and a flux coated welding electrode using electrical energy to melt and deposit weld metal. This is the most commonly used process in the world.

Basic Requirements for the SMAW process:

Heat source: Welding Equipment Current Range 30-400 A –depending on size of the electrode in general, even though there are welding machines used up to 600 Amps AC or DC welding machines can be used in SMAW Operation.

Welding Consumable: Flux coated welding electrode (1.6- 8 mm diameter)
A trained welder is required to operate the process, So SMAW or MMAW is the most commonly used process in the world.

SMAW Process advantages:

  • This is the simplest of all welding process.
  • Equipment Portable
  • Economical Cost of Equipment
  • Variety of application & wide availability of electrodes
  • Range of metals & their alloys can be welded
  • Welding in all Positions
  • Welding in Indoor & Outdoors
  • Extended welding cable to long distances in comparison to another process

Limitations of SMAW process:

  • Low productivity as in a 10-minute cycle welding happens only for 6 minutes
  • Process also involves a frequent changes of welding electrode
  • Moisture from flux coatings can create weld-related problems
  • Safety problems like arc strike, Stray current & electric shock risks
  • Absolutely Manual process – hence called Manual metal arc welding

GMAW & FCAW processes: 

  • A continuous solid wire, small diameter

                               GMAW uses solid wire, no flux

                               FCAW use flux-filled wire

  • Wire feed through the gun to the arc by wire feeder.
  • Weld pool may be protected from oxidation by shielding gas.
  • High productivity 3 kg/h or more
  • Direct current (DCEP mostly).

Process Requirement:

  • Welding power source
  • Wire feeder mechanism- In-built/separate
  • Gun with gas supply & trigger switch
    1. Manual/semi-automatic guns
    2. Automatic torches available
    3. Can be fitted to automation etc.

Advantages in GMAW:

  • Faster as compared to TIG & SMAW.
  • Can produce joints with deep penetration.
  • Thick & thin, jobs can be welded effectively.
  • Can be used for fabrication and maintenance repair job.
  • Can be mechanized easily
  • Reduced distortion.

Limitation in GMAW: 

More Complex due to

  • Electrode stick-out
  • Torch angle
  • Welding parameters
  • Type and size of electrode
  • Welding torch manipulation
  • Not suitable for outdoor welding applications

GTAW or TIG welding: GTAW or Tungsten Inert gas welding uses a consumable Tungsten electrode as the heat source.
This consists of the below.
Heat source – welding power source to create an arc between a tungsten tip and the parent metal
30-400A, AC or DC welding machine and 0-20V
Inert gas shielding is used in the process.
Consumable: filler rod can be used between 1 to 4mm diameter
Process Features:

  • Excellent control
    1. Stable arc at low power (80A at 11V)
    2. Independently added filler
    3. Ideal for intricate welds eg root runs in the pipe or thin sheet
    4. Low productivity 0.5kg/h manual
  • High quality
    1. Clean process, no slag
    2. Low oxygen and nitrogen weld metal
    3. Defect-free, excellent profile even for single-sided welds

Advantages in GTAW/TIG Process:

  • No slag inclusion
  • Clear visibility of arc and job
  • All position weldability
  • Suitable for high quality welding of thin material
  • Root run of thick materials
  • Ideal for Aluminum, Stainless steel & Titanium

Limitations in GTAW:

  • Slow as compared to SMAW/MIG/MAG & SAW welding
  • Possibility of tungsten inclusion in the weld deposit which is hard & brittle
  • Not suitable for outdoor welding

Submerged Arc welding process (SAW Process): In the Saw Process, as the name signifies, welding happens submerged beneath the flux. SAW process also employs welding consumables usually a wire & arc is established between the welding wire and base metal and welding happens underneath the metal powder of flux, shielding the arc from the atmosphere and its gases.

saw process

Heat source: Arc between a wire and base metal
Current Range: 200 Amps -1200 Amps
DC operation
Power Consumption

  • 35-56 KVA
  • Power source
  • Welding head and control box
  • Welding head travel
  • Flux recovery system (optional)
  • Positioners and Fixtures

Hence the basic difference between the two processes is that in the SMAW process, the flux-coated electrode provides the shielding from the atmosphere & in SAW process an external flux is delivered at the arcing area to act as a shield, so welding happens underneath the powder flux fed by a delivery system.

SMAW Process – Advantages:

  • Simplest of all Arc welding process
  • Equipment is portable
  • Economical cost of equipment
  • Variety of application & wide availability of electrodes
  • Range of metals & their alloys can be welded
  • Welding in all Positions
  • Welding in Indoor & Outdoors
  • Extended welding cable to long distances when compared to other processes

SAW Process advantages:

  • High productivity up to 2 to 10 kg per hour
  • Speed almost up to 2m/ min
  • Can be easily automated for even higher productivity

Limitations of the SAW process:

  • Bulky, expensive, and heavy equipment
  • Flat and horizontal positions only
  • Thicker sections (6mm and above)
  • Mostly ferrous materials (also Ni alloys)

Conclusion: A wide variety of processes are available for joining or hard surfacing ferrous and non-ferrous materials. Each of these processes provides different mechanical properties and works in specific conditions, with a welding power source. There are several factors to consider in welding rod selection:

  • Base metal properties
  • Tensile strength required
  • Welding current
  • Base metal thickness, shape and joint fit-up
  • Welding position
  • Specification and service conditions
  • No. of similar jobs – Scope for automation
  • Environmental job conditions

These methods are all commonly used by Industry. Before we select any particular method for welding, we need to analyze each of the factors listed above.

ADFL serves the industry with the manufacture and supply of all types of consumables for MMAW, MIG /Mag, TIG, SAW & non-fusion processes like soldering, brazing, and braze welding. This is why Ador Fontech’s name is synonymous with total solutions for any maintenance & repair problem, ensuring the Life Enhancement of Industrial components, to the complete satisfaction of customers.

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Welding Equipment in Industry

In fabrication, welding helps to join materials using heat to melt the parts together. Useful with metals and thermoplastics, this process typically uses a filler material to the weld pool of molten material, helping to make the joint stronger than the base material. Pressure is used in the process along with heat in welding, while a shield protects the metals from being oxidized in the process.

The most heat sources for joining material using a fusion welding process are listed below:

Fusion welding sources

We have five types of Arc welding Equipment/power sources. These are AC transformer; DC rectifier; AC/DC transformer rectifier, DC generator, and inverter.

MMAW / Arc Welding Equipment – Features

  • Portable & Versatile equipment
  • Requires practiced skills
  • Applicable to a wide range of materials, joints, positions
  • About 1kg per hour of weld deposited
  • Properties can be excellent
  • Benchmark process

MMAW / Arc Welding Equipment – Advantages

  • This is the simplest of all Arc welding processes.
  • Equipment is portable
  • Economical Cost of Equipment
  • Variety of applications & wide availability of electrodes
  • The range of metals & their alloys can be welded
  • Welding in all Positions
  • Welding can be Indoors or Outdoors 
  • Welding cable can be extended to long distances when compared to other processes

Types of Arc Welding Equipment / Power Sources:

Arc welding power sources

A welding transformer is basically a step-down transformer that brings down the source voltage to weldable voltage. This is simple Arc welding Equipment.

Motor Generator 

Motor Generator is also an Arc welding Equipment, which utilizes input power to rotate the generator through an induction motor. This kinetic energy is converted to electrical energy by carbon brushes fitted in the commuter, generating DC current is generated supplying constant power to the process.

In a Diesel Generator, diesel is used as fuel to run the motor to generate electricity; this is widely used in on-site jobs for Arc welding applications 

Welding Rectifier

Welding rectifiers are essentially transformers with an electrical device as a rectifier which changes AC to DC. Rectifier basically consists of Silicon diodes, which ensure the flow of current in one direction giving DC output. This is most commonly used with Arc welding equipment.

Welding Inverter

This latest technology power source is the most popular Arc Welding equipment today. A welding inverter is a power block, controlled by software, which offers the required static and dynamic characteristics needed for a specific welding process. It takes AC input and converts it into DC after step-down & then converts it further into high-frequency AC & then again converts it to DC – finally offering a DC output. When using an inverter power source, a user gains all the advantages of thyristor control. Additionally, they get superior efficiency, power savings, better performance, and quality of welding.

We at Ador Fontech offer the best “Make in India” solutions with Fontech Tornado brand Welding Power sources. We offer both robust Thyristor-controlled machines as well as Power saving Inverter machines for all welding processes like Manual Metal Arc welding, TIG, MIG/MAG, and SAW. Once again, we reiterate our total commitment to total solutions in welding with this range of equipment, catering to the complete requirements of customers. 

Reclaim. Do not Replace.

 

Also read:- Hypertherm Life Expectancy of Consumables

Key Differences Between SMAW and SAW Welding

The basic difference between the two processes, SMAW and SAW welding, is this. In the SMAW process, the flux-coated electrode helps to shield the welding process from any interaction with the atmosphere. In the SAW process, an external flux delivered at the arcing area acts as a shield. So, the welding happens underneath the powder flux fed by a delivery system. This is the primary difference between SAW & SMAW processes. Let us get introduced to both processes.

Pic SAW SMAW

An Introduction to Shielded Metal Arc Welding (SMAW) process

In SMAW or MMAW (Manual Metal Arc Welding), the arc is established between Parent Metal shielded (flux-coated) welding electrodes using electrical energy to deposit weld metal. 

Heat source: Arc between metal and a flux-coated electrode (1.6- 8 mm diameter)   

Energy Consumption: 30 – 400 Amps –depending on the size of the electrode in general, even though there are welding machines that use up to 600 Amps. AC or DC SMAW Operation Power consumption 1-12 KW

An Introduction to Submerged Arc Welding (SAW) process

 In the SAW Process, as the name signifies, the welding happens submerged beneath the flux. SAW process also employs a welding consumable, usually a wire. An arc is established between the welding wire and base metal and welding happens underneath the metal powder of flux, which shields the arc from the atmosphere.

image

Heat source: Arc between a wire and base metal 

Current Range: 200 Amps -1200 Amps

DC operation                       

Power Consumption-35-56 KVA

  • Power source
  • Welding head and control box
  • Welding head travel
  • Flux recovery system (optional)

Let us take a look at the process advantages & limitations of both SMAW and SAW processes.

Advantages with the SMAW Process:

  • This is the simplest of all Arc welding processes.
  • Equipment is portable
  • Cost of equipment is economical
  • Variety of applications & wide range of electrodes available
  • A range of metals & their alloys can be welded
  • Welding can be done in all positions
  • Welding can happen indoors & outdoors 
  • Welding cable can be extended to long distances in comparison to the SAW process

Limitations of the SMAW process:

  • Low productivity as in a 10-minute span, welding happens only for 6 minutes 
  • The process also involves the frequent change of welding electrode
  • Moisture from flux coatings can create weld-related problems
  • Safety problems like arc strike, stray current & electric shock risks
  • Absolutely manual process – hence called Manual Metal Arc Welding 

Advantages with the SAW Process:

  • High productivity up to 2 to 10 kg per hour.
  • Speed almost up to 2m/min
  • Can be easily automated for even higher productivity.

Limitations of the SAW process:

  • Bulky, expensive, and heavy equipment
  • Flat and horizontal positions only
  • Thicker sections (6mm and above)
  • Mostly ferrous materials (also Ni alloys)

Given these essential differences between MMAW/SMAW and SAW processes and their respective advantages and limitations, a considered choice can be made between these processes.

image

 We, at Ador Fontech, offer the best “Make in India” solutions with Fontech Tornado brand welding machines for both SMAW and SAW processes. Once again, we reiterate our commitment to total solutions in welding to the complete satisfaction of customers, with this range of equipment.  

 

Also read:- Resolve Wear Factors

Non-Fusion Welding with Brazing & Soldering

Brazing and soldering

Soldering and Brazing form a part of non-fusion welding processes, where only the filler rod is melted in the process.

The three common processes used in non-fusion welding are :

  • Soldering
  • Brazing 
  • Braze welding

Advantages & Disadvantages with Non-fusion welding

Let’s take a look at the advantages and disadvantages of this type of welding.

Advantages

  • Lower temperature
  • Easy assembly
  • Welds dissimilar metals
  • Allows disassembly/realignment
  • Joins metals of different thicknesses
  • Joins different types of metal

Disadvantages

  • Results in lower tensile strength
  • Not an efficient method for thick metal 
  • Not an efficient method for large parts 

Depending on the specific application, this welding is also an accepted method.

Four Requirements of Brazing and Soldering Process

  • Clean metal
  • Appropriate filler rod
  • Correct flux
  • Heat

Clean Metal:

This process needs the metal being welded to be clean, for the following reasons.

  • For Soldering and brazing processes bond metal by adhesion, which is the molecular attraction exerted between bodies in contact.
  • Molecular bonding requires a clean surface – not a polished surface.

Filler Rod 

Suitable filler rods are an essential part of the process. Such filler rods are available for many soldering and brazing processes.  

  • Brazing: A brazing rod is available as a bare rod or a flux-coated rod.
  • Soldering: 
    • Solder can be a solid or flux core/paste
    • Can be made of tin, silver, or zinc alloy.

 Flux:

Flux must be used with all soldering and brazing processes.

  • Three purposes of flux.
    • Chemically clean the metal
    • Shield from oxidation and atmospheric contamination
    • Promote wetting
  • Flux must be appropriate for the metal and filler material.
  • Flux is available in three (3) forms.
    • Paste
    • Powder
    • Liquid

Heat Source:

  • Heat is measured in British Thermal Units and must be sufficient in measure to raise the base metal temperature above the melting point of the filler rod to make soldering or brazing joint
  • Several heat sources can be used.
    • Oxyacetylene
    • Air acetylene
    • Air propane (LPG)
    • Oxy propane
    • Electric soldering iron
    • Electric soldering gun

Importance of Controlling Heat in Soldering & brazing:

  • Metals are excellent conductors of heat
    • Heat applied to the joint moves away from the joint.
    • The greater the mass of metal that must be heated–the greater the heat requirement.
  • Excessive heat will cause the flux to burn.
    • Contaminates the joint.
    • Joint must be re-cleaned
  • Manipulation of the heat source may be necessary to heat both pieces evenly.

Let’s understand Brazing and Soldering:

Soldering:

Soldering is a process that uses a metal alloy that melts below 450oC and may or may not use capillary action. Capillary action (wicking) occurs when a substance is able to draw another substance into it, like a wick draws oil in.

Solders are divided into two categories:

    • Soft
    • Hard
  • Soft soldering
    • Lead or lead replacement solder
    • Lower tensile strength
    • Copper pipe and sheet metal
    • Stained glass
  • Hard soldering
    • Silver-based solders
    • Jewelry

Brazing:

The brazing process uses a metal alloy that melts above 450oC but has a lower melting point in comparison to the base metal. The melted filler metal gets drawn into the joint or kept in the joint through capillary action, and the brazing process relies on this. The capillary effect requires very minute gaps between metal surfaces, clean surfaces, and flux, and is a function of the ability of a liquid to wet a particular material. This is why the basic difference between soldering and brazing is the temperature of the process.

ADFL is one of the few companies in India manufacturing Brazing Alloys and Soldering alloys with the required flux. This product range of Ador Fontech limited signifies our concept of Life Enhancement of Industrial components to the complete satisfaction of customers.  

Reclaim. Do not Replace.

 

Also read:- Corrosion and Cracks in Kiln Shells

Hypertherm: Life Expectancy of Consumables

It’s hard to offer an exact (or even an in-exact) estimate of the number of factors that impact the life expectancy of a plasma cutter consumable —operator experience, type and age of the torch, material type and thickness, air quality, etc. However, when the operator understands good piercing and edge-starting techniques which keep molten metal from blowing back onto the torch nozzle (or tip if it is a non-Hypertherm system) then the life of the consumable can be extremely long. Hence, Hypertherm plasma cutter consumables have an edge over conventional plasma cutting machines.

Hypertherm Life Expectancy of Consumables

Cutting Scenarios:

The biggest problem with most plasma cutter torches occurs when hand cutting with exposed (unshielded) nozzle-torch consumables. Ideally, you need to hold a standoff, with an unshielded setup at all amperages greater than 30 amps or so. If the nozzle touches the plate during a cut, it creates an electric current path between the negative electrode, nozzle, and positive plate. This causes a double arc between the electrode and nozzle, and the nozzle and plate, which damages the nozzle’s orifice. When the orifice gets a little damaged, poor angularity is the first thing you’ll notice, followed by more double arcs and more damage. Eventually, you’ll notice slower cut speeds and heavy dross, at which point you’ll likely change your nozzle.

Secondly, some people use a standoff device to hold the torch up off the metal. Unfortunately, molten metal can still blowback during piercing, once again passing electricity from the nozzle to the plate and leading to double arcing. If you have used a handheld torch with an exposed nozzle at more than 30 amps while drag cutting, you’ve likely felt the torch “sticking” to the plate. This is a result of double arcing.

Hypertherm Patented Solutions for Longer Life:

One way around this problem is through the use of shielded torch technology, invented and patented by Hypertherm in the ’80s. The shield works to electrically isolate the nozzle from the plate to totally eliminate double arcing. Hypertherm plasma shielded torches drag cut at up to 200 amps with no friction or double arcing for a dramatic improvement in a plasma cutter consumable’s life and cut quality.

In the last 30 or so years since Hypertherm introduced shielded torch technology, engineers have made enormous strides in extending the life of these consumables. For example, our Duramax torches of Hypertherm plasma systems come with the new standard consumables with nearly all new Powermax systems and as a retrofit torch for older Hypertherm systems and use the shield for just nozzle isolation. The shield and nozzle for these torches use a patented technology called Conical Flow to inject greater airflow around the perimeter of the arc. This increases the energy density of the arc and provides better cooling to the nozzle. This results in no sticking, no double arcing, offering faster-cut speeds, thicker piercing capability, and dramatically longer nozzle life.

So, assuming you are using a Hypertherm plasma Duramax torch with the latest consumable technology, then I would expect you to cut hundreds of feet of metal. In addition, you should be able to make between 600 and 1,200 pieces, after which you would need to replace only your electrode. All your remaining Hypertherm consumables would likely continue to work just fine. Put another way, you should be able to get between 2 and 4 full days of actual arc-on time before needing to replace any of your consumables.

This is why Ador Fontech Limited, the name synonymous with total solutions for any Maintenance & Repair solutions, recommends Hypertherm plasma with Duramax Torch and consumables as a robust cutting solution to all our customers. “Using Spurious/Counterfeit consumables is nothing but a shortcut to machine breakdown & loss of warranty.”

Corrosion and Cracks in Kiln Shells – Repair Solutions from ADFL

Cement Industry uses Rotary Kiln for Pyro-processing the raw mixture of finely crushed limestone (calcium carbonate + silica-bearing minerals) to manufacture cement. Kiln or kiln shell is at the heart of the cement-making process; its capacity, usually defines the capacity of the cement plant.

The Rotary Kiln consists of a tube made up of structural rolled steel material and lined with firebrick (or) castables. This kiln shell/tube slopes (1⁰to 4⁰) from one end to another, and slowly rotates on its axis at between 30 & 250 revolutions per hour depending on the plant. Raw mix is fed in the upper end and the rotation of the kiln causes the mix to move gradually to the other end of the kiln shell. At the other end to the lower part of the kiln, the burner pipe system provides a concentric flame. The raw mix moves under the flame and reaches its peak temperature before it drops out of the kiln into the cooler. In principle, the air drawn through the cooler flows into the kiln causing combustion of the fuel fed through burner pipe ensuring intense heat right across the kiln shell taking the temperature close to 1450⁰ C turning the raw mix into fully calcinated clinker.

Corrosion and Cracks in Kiln Shells

This Kiln shell made of structural rolled steel has a tensile strength between 50,000 to 80,000 PSI at room temperature but once it goes beyond 200 degrees. The tensile strength drops rapidly and at around 430 degrees, studies have noted a strength loss of close to 50% from its original strength.  Because of its continuous working condition at this high temperature along with corrosion caused by castables (which also cause thickness reduction in Rotary kiln or Kiln shell). After a period, fatigue develops in the kiln shell lining and with any small damage to the firebrick or castable it has a temperature attack or thermal shock in the kiln shell causing hot spots and red spots leading to cracks.

Hot Spot & Red Spot

Hot spot is an isolated area in the Rotary kiln where the Kiln shell temperature is close to 550 deg. It is not visible to to the naked eye but can be deducted by Shell scanner, also known as portable Infra-red pyrometer. Red spot is an area visible at night, indicating that the temperature is above 550 degrees. In layman’s terms, hot spot is like a warning sign that action is needed but red spot means immediate action with stoppage of Rotary kiln. Every hot spot eventually becomes a red spot-causing cracks in kiln shell. With today’s improved technology the shell temperature is monitored continuously with computer-aided sensors.  At times kiln is stopped on deduction of a hot spot on further inspection cracks are noticed in the Kiln shell for immediate action

Generally, cracks that are perpendicular to rotary kiln and not of significant lengths and depth are repaired by welding. If the cracks are circumferential in nature, the particular portion is cut and removed & a new shell of the same length is inserted, aligned & welded. Also, kiln shell replacement is the preferred method in most cases of the red spot.

ADFL holds pre-eminence in both these types of repair – kiln shell repairs & kiln shell replacement. Further, we also offer a wear protection solution for high-temperature corrosion

  • We offer customized solutions for the repair of rotary kiln shell cracks with a combination of our LH 1105 & LH 521 alloys. We have credentials in attending a number of these kinds of breakdowns shutdowns
  • We are the only solution provider to offer automated kiln shell joining using the SAW process for kiln shell replacement jobs. By using an automated SAW process, we can complete a single joint in 24-36 hours – offering the highest productivity with X-ray quality welding
  • We also supply kiln shells & cowl shells of the required dimensions. This is a fabricated shell with single SAW joints, making it a value proposition to the industry.
  • We also have a Wear Protection solution for Rotary Kilns against high-temperature corrosion, Zircoat-M, a high-temperature coating, can be applied to a kiln shell’s inside portion before fixing castables to totally eliminate corrosion problems in kilns.

With such customized solutions for cement plant maintenance, repair, and refurbishment requirements, Ador Fontech Limited remains the first name to recall for customers across India, as we stay true to our motto of Life Enhancement of industrial components in every sphere possible.

Reclaim, Do not Replace

Resolve the Challenges in M&R Welding with Unique Electrodes

To understand the types of Welding Electrodes, more commonly known as welding rods in welders parlance, it is essential to understand the particular type of application it is used for a specific industry. Welding is, primarily needed to fabricate new parts or components. Secondly, it is used to repair broken/cracked components or to hard-face and build up a worn-out component to prolong its life. Hence it is essential to classify welding by these two types of applications.

  • Electrodes for Fabrication Welding
  • Electrodes for Maintenance & Repair Welding

M&R Welding with Unique Electrodes

What is the Difference?

Specifications of welding electrodes (or) rods used in the production or fabrication of components are largely confined to meeting the minimum requirements of a particular class. Basically, conventional electrodes are designed essentially for production welding. In other words, they are expected to meet the specifications and design parameters of a specific component. Based on such an evaluation, a welding engineer chooses a particular electrode, only when it meets his requirements.

But in the case of Maintenance & Repair (M&R) welding, these specifications are too broad to realistically meet the precise & varied requirements of a repair application. Hence M&R products are basically Low Heat (LH) input welding rods or electrodes. They are designed to weld specific components to give them extended life or improve their performance. In most cases of M&R, we use a welding electrode to repair a broken component or worn-out component. In the process, we always go beyond the original design parameters to ensure that the refurbished component has the best properties & optimal performance.

M&R Welding

Key Differences to Consider:

  • Composition of Base Material – In the case of fabrication welding, the job is carried out on new & known components, so all parameters are known. We can choose the welding material exactly, knowing the composition of the base material. This makes it easy to select the right welding electrode for the job. But in the case of Maintenance & Repair, the welding job is done without knowing the exact base material. This makes it necessary for us to have access to versatile products, which can be welded onto different types of base materials, like steel, cast iron etc.
  • State of Welding Component: In the case of fabrication welding, the job is done using pristine new plates. So, there are no special requirements while in the case of M&R welding, most of the welding needs to be done with fatigued, old, and contaminated components. Such welding jobs call for welding electrodes with richer chemistry & properties to match this specific requirement.
  • Preparation of Joint: In fabrication welding, all welding parameters are clear, so welders just need to adhere to them to complete a job properly. In the case of M&R welding, the job is many times conducted in-situ or at the site. This requirement complicates the task, as we will not be in a position to make any provision to prepare the area to be welded, like a V groove, which is ideal to ensure a proper job. Under such circumstances, the rich alloying elements of the welding electrode need to offer additional strength to the joint.
  • Type of Welding: Usually, any fabrication facility or workshop insists on executing a welding job using a flat or down-hand welding position only, as this is considered to be the best position to achieve ideal welding standards. But ensuring a down-hand welding position is not always possible with M&R welding because the work is mostly done on-site, and we may not always have the choice of position. This is why all M&R electrodes of Ador Fontech make are designed to enable welding from any position, making them unique.
  • Extended Work-Life: Extending the work-life of the original component is very important, in both types of welding as customers are more worried about the reliability and life extension offered by a repair. This is understandable as no plant can accept stoppages or breakdowns, especially after undertaking extensive repairs to fix all issues. M&R Electrodes/Rods offer an ideal solution in cases where we want to design products or components with extended life.
  • Special Re-Enforcement: When we are fabricating a component, it is always done as per a product’s design & drawing, so no special re-enforcement will be required. But in the case of M&R welding, we will be required to apply special re-enforcement techniques to ensure a long life for the repaired component.
  • Deadline for Completion: In fabrication welding, there is always a deadline set for completion, but it is always under control as this will be a planned activity. But most M&R welding jobs happen when there is a breakdown or stoppage. So, we need special products which can weld without pre or post-weld heat treatment so the job gets completed faster with the highest level of reliability.

Focusing on all the above considerations, Ador Fontech has designed & developed an exclusive Range of LH –Low heat Input Welding Electrodes/rods(Alloys) to resolve the specific problems in Maintenance & Repair welding.

Reclaim, Do not Replace