Tips to Weld Cast Iron

Types of Cast Iron in Industry

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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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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