Spheriodiser Cored Wire

PURE MAGNESIUM & Mg-­FeSi CORED WIRE FOR IRON/STEEL TREATMENT WITH IMPROVED RECOVERY:

No ImageToday majority of ductile iron castings made throughout the world are produced using ladle metallurgy practices with Mg-­FeSi alloys and cored wire injection. It is estimated that Mg-­FeSi alloys ae used in 65 percent of all ductile iron produced worldwide. The supply of domestically produced Mg-­FeSi becomes important in assessing whether this important raw material will be available in sufficient quantities to sustain the forecasted growth.

High performing Mg-­FeSi alloys are to be manufactured to sustain the projected growth of ductile iron. Today the concern with automation, cost, consistency, improved recovery and reduced (fumes) environmental hazards in work space makes more and more cast-­house to adopt cored wire injection method for ladle inoculation/spheroidization treatment.

Minex has erected specialized plants to provide a consistent and quality service to the customers. Certified to ISO 9001, Minex-­Kalmeshwar dedicated plant is one of the major Pure Mg and MgFeSi cored wire production plants in the India. Minex’s consistency has seen the most quality oriented foundries in India and abroad turn to Minex as their preferred supplier. Further news and development may be found on our website www.minexindia.com

Product Introduction:

The valuable characteristics of magnesium addition to iron have been known for the purpose of nodule formation and improving the mechanical properties. Addition of magnesium promotes transformation of graphite flakes to nodules during solidification of iron melt due to increase in the surface tension.

Today, magnesium, pure or in a form of master alloy, is the most effective nodularizing agent used by the foundry industry to produce quality ductile iron castings. However, the usage of magnesium for treating of liquid iron has a number of difficulties caused by specific physical properties of magnesium. This includes low melting and boiling temperatures (1202F/650C and 2025F/1107C respectively), low density (1.738 g/cm3 vs. 7.0g/cm3 of liquid cast iron), and low solubility in liquid iron (about 0.001% wt at 650C). As a result, the introduction of magnesium or magnesium containing alloy into liquid iron is typically accompanied by significant flame and fume called 'pyro effect', which makes the magnesium treatment process highly violent and unsafe. The later caused
significant magnesium losses due to magnesium burning, and hence reduction of residual magnesium content in solidified castings. Certain magnesium losses are also incurred due to magnesium reaction with elements contained in liquid iron: first, with sulphur, and second with oxygen.

Cored wire in particular a magnesium or Mg-­FeSi core is surrounded by a steel sheath or jacket have found wide application in the treating of molten ferrous metal for inoculation, desulphurization and spheroidization. The pure magnesium and Mg-­FeSi cored wire is manufactured with special grade steel sheath so as to introduce magnesium into the steel bath at greatest possible depth so as to make use of the increased pressure from ferrostatic head and thus to prevent magnesium from evaporating.

Pure magnesium metal granules or Mg-­FeSi powder is filled in high grade quality cold rolled steel strip. The special encapsulating jacket (steel strip) of cored wire is first time introduced in said product for higher penetration depth of magnesium & improves recovery. Cored wire is injected with aid of wire injection system in iron melt. The Pure Magnesium and Mg-­FeSi cored wire specifications are as follows:

Mg-­FeSi Cored Wire Specifications:

Chemical composition of Mg-FeSi powder (%)
Grade Mg Si Al (Max) Ca Re Othr (Max) Fe
FeSiMg 20 18-­â20 45-­â46 0.5 1-­3 1-­3 1 Bal
FeSiMg 20 (WRe) 20-­â25 33-­â38 0.8 1-­3 1 max 1 Bal
FeSiMg 30 30-­â32 25-­â33 0.8 1-­3 0.5-3 1 Bal
FeSiMg 40 38-­â42 22-­â30 0.8 1-­2 0.5-3 1 Bal
FeSiMg 50 50-­â52 25-­â30 0.8 1-­3 1-3.5 1 Bal
FeSiMg 80 78-­â82 7-­â11 0.8 1-­3 1-3 1 Bal

 

Powder specification
Grade Density
(gm/cc)
Melting
Point
(°C)
Boiling
Point
(°C)
Size (mm)
FeSiMg 4.3–4.8 910-­1225   -­1.4+0.3
Fe 7.8 1540 2860 -0.6+0.045
Si 2.4 1412 3270 -1.4+0.016
Mg 1.74 650 1090 -1.4+0.212
Strip Specification
Grade Diameter
(0, mm)
Thickness (mm)
EDD IS – 513

9± 0.5

13±0.2

0.40±0.03

0.40±0.03

Wire Characteristics
Grade FeSiMg 20 FeSiMg 20 (WâRe) FeSiMg 30 FeSiMg 40 FeSiMg 50 FeSiMg 80
Diameter ( 0, mm) 9±0.5 9±0.5 9±0.5 9±0.5 9±0.5 9±0.5
Shape Round Round Round Round Round Round
Powder Fill (gm/mt) 120±10 115±10 110±10 100±10 95±10 70±10
Coil Specification (Flipping Coil – Horizontal & Vertical)
Details

9 mm 0

9 mm 0

9 mm 0 9 mm 0 9 mm 0 9 mm 0 Coil Identification

 

20% Alloy 20% W- Re Alloy 30% Alloy 40%
Alloy
50%
Alloy
20%
Alloy
Powder Weight
(MT)
0.500 0.500

0.500

0.500

0.500

0.500

All coils are color coded and fixed with a detailed sticker clearly displaying details such as coil no., powder content, strip weight, gross weight density & length. A fluorescent sticker displays the name of the product in bold letters on the outer diameter of the coil.

Handling

No metal sling, chain or rod is to be used across the ID of the coil for handling as it may damage the coil. Use only polyester, synthetic slings, fork lift/tractor to handle the coil. The pallet is an integral part of the coil and it is to be removed till the coil is consumed.

Shelf Life

Follow the shelf life period specified by MINEX








Strip Weight
(MT)
0.505 0.420 0.595 0.640 0.695 0.850
Net Weight
(MT)
1.005 0.920 1.095 1.140 1.195 1.350
Length (Mtrs) 4166 4385 4545 5000 5555 7142
Internal
Diameter (mm)
650 650 650 650 650 650
External
Diameter (mm)
1000 1050 1050 1050 1080 1200
Height (mm) 630 630 630 630 630 630

Pure Magnesium Cored Wire Specifications:

 

Chemical composition of pure Magnesium powder (%)
Grade Mg Other (Max)
Mg100 98 2.0

 

Powder specification
Grade Density (gm/cc) Melting
Point
(°C)
Boiling
Point
(°C)
Size (mm)
Mg 1.74 650 1090 â1.4+0.212
Strip Specification
Grade Diameter
(0, mm)
Thickness (mm)
EDD IS – 513 9±0.5 0.9±0.03
Wire Characteristics
Grade Diameter ( 0, mm) Shape Powder Fill (gm/mt)
Ca 9±0.5 Round 60±10
Coil Specification (Flipping Coil – Horizontal & Vertical)
Details

9 mm 0

Coil Identification

 

F8â04
Powder Weight
(MT)
0.400

All coils are color coded and fixed with a detailed sticker clearly displaying details such as coil no., powder content, strip weight, gross weight density & length. A fluorescent sticker displays the name of the product in bold letters on the outer diameter of the coil.

Handling

No metal sling, chain or rod is to be used across the ID of the coil for handling as it may damage the coil. Use only polyester, synthetic slings, fork lift/tractor to handle the coil. The pallet is an integral part of the coil and it is to be removed till the coil is consumed.

Shelf Life

Follow the shelf life period specified by MINEX








Strip Weight
(MT)
0.770
Net Weight
(MT)
1.170
Length (Mtrs) 6153
Internal
Diameter (mm)
650
External
Diameter (mm)
1140
Height (mm) 700

Over the last few years, cored wire has increases its popularity of spheroidization of ductile iron and manufacturing of compacted graphite (CG) iron. The current concern with automation, cost, consistency and large amount of fumes coming in work space from iron treatment ladle makes more and more cast shop adopt cored wire method. The treatment effects can be equal to or higher than other methods if it is applied adequately. Therefore there is no surprise that cored wire is adopted widely.No Image

Normally the Cored Wire is a steel tube filled with granular Magnesium or FeSiMg alloy or mixture of these. (as shown in fig.)

This cored wire is injected into the liquid iron with the help of wire feeding system. This consists of two sets of rolls which pulls the cored wire from the coil and injects into the melt through guide pipe. (wire injection layout as shown in fig. 2)No ImageNo Image

The sequence of operation in cored wire injection process for ductile and compacted graphite iron is nearly same. This sequence of operation consists of

  • Tapping of molten metal at predetermined of known composition into the treatment ladle.
  • Weighing of molten metal.
  • Set the length of the cored wire to be injected.
  • Set the wire speed.
  • Measure the temperature before wire injection.
  • Magnesium wire injection
  • De slagging
  • Pouring/ inoculation

But extra care should be taken in case of production of compacted graphite iron. The Mg injection in this case has to be decided over metallurgical requirement i.e. evaluated by thermal analysis to meet the metallurgical requirement of CG Iron (Nodule graphite should be controlled within 0-­ 20% and minimum 80% should be compactedgraphite).

CGI is stable over only range of 0.005% Mg and hence needed precisely maintained Mg in range of 0.005 to 0.015%. Thus the precise adjustment of Mg is only possible by cored wire injection technology.

Fig. 3: The stable CGI plateau exists over a range of approximately0.008% Mg

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Inoculation can be carried out by wire injection process in both ladle as well as stream/late inoculation with different choice of composition of inoculants. Inoculation is combined with Mg treatment, where appropriate, using a second injection machine feeding inoculating wire at the end of the Mg treatment. Usually inoculant cored wire are filled with FeSi (70-­75%) alloy based granular powder containing active elements like Ca, Ba, Zr, Sr etc as per desired composition. Ladle inoculation is carried out with 9/13mm diameter CW during/after Mg wire treatment and late inoculation is carried at pouring basin with 5-­9mm diameter CW.

  • Sulphur content of the Base Metal to be treated ( Sf )
  • Treatment Temperature
  • Wire feed rate and treatment time
  • Geometry of treatment ladle
  • Quantity of the Metal to be treated.
  • Composition of Mg cored wire
  • Desired percentage of Magnesium in the Metal
  • Free board of about 300mm
  • Geometry of the wire guide tubes
  • Design of treatment station

Sulphur content of the Base Metal

Mg Cored wire injection process is very flexible with Sulphur content, because it can treat base iron with higher S composition as combined desulphurization and Mg treatment of cupola iron with S range 0.05 to 0.15% (preferably S 0.08%) and base iron with low S composition as Mg treatment of electrically melted iron with S content < 0.03% (preferably S < 0.015%)

But always keep in mind, any point of increase of S in iron will result in high wire consumption, more cost and more slag. And if Sulphur is very low < 0.01% then special attention has to be paid in inoculation of the melt.

Treatment temperature

With all other Mg treatment processes, the cored wire process shows similar correlation between Mg recovery and treatment temperature.

The influence of different treatment temperature in cored wire injection process has been studied on Mg yield and desulphurizing ratio. It is found that Mg yield and desulphurizing ratio is dropping while temperature rising, and also temperature dropsare increasing while temperature is rising. Therefore temperature of iron melt should be as low as possible.

For example the influence of treatment temperature on Mg recovery, desulphurization and temperature drop at specific condition as shown

Wire feed rate and treatment time

Wire feeding speed is very important parameter in Mg wire injection process, as it greatly influences the desulphurization and spheroidization of iron melt. The optimum wire injection speed is such that it release the Mg/FeSiMg powder into a certain depth (near bottom of ladle) of iron melt, where Mg changes to vapor bubbles under sufficient ferrostatic head which raise slowly and reacts with iron melt from bottom to head.

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The release of Mg powder near the bottom can over come the weakness of Mg as low density, high vapor pressure, low boiling point, active chemical property etc;; and leads to higher Mg recovery. Too high or too low speed will reduce the effect of treatment, additonally the temperature drops are below 80 C.

At too low speed the wire is melted near the surface of the melt and Mg is lost near surface (as shown in fig. 6.b). And at too high speed there are two reasons for lower yield of magnesium;;

(a) the wire does not melt at the bottom and comes out near surface of melt. Hence release of Mg much above the level of bottom of the melt or (b) at higher speed the rate of release of Mg near bottom is very high. It leads to high vapor pressure of Mg bubbles which rise at high speed (as shown in fig.6.a). If the feeding speed and treatment temperature are not well controlled, the treatment effect will deteriorate seriously and sometimes explosion will happen dangerously in treatment ladle if the feeding speed is too high.

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Composition of Mg cored wire and selection of wire Different types of Mg cored wires are available as pure Mg cored wire, blended wires, alloy wires etc. The Mg content in the cored wire depends on the wire diameter and composition. Pure Mg cored wire is more reactive than the alloyed Mg (FeSiMg/FeSiMg-­RE etc) cored wire because virgin Mg is highly reactive, has low boiling point and high vapor pressure. The selection of types of Mg cored wire shall vary from foundry to foundry, depending on various parameters like quantity of metal treated, temperature, sulphur and oxygen content etc.

Desired percentage of Magnesium in the Metal and Treatment cost

The following formula shows the basic calculation method for wire length and Mg recovery. Initially certain assumptions has to be met, the effect of temperature is being ignored in order to calculate the wire requirement for new applications:

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For example:
Calculating quantity of cored wire to be injected and cost of treatment as practiced at one of the renowned SG iron foundry in India is as follows:

The existing parameters are:

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Although the cost comparison with other process as sandwich or other, is very difficult, because type/ grades of alloy, cost of alloy are used and recovery of Mg etc. Suppose using FeSiMg 7% Mg alloy is used to treat above metal and the Mg recovery is 45-­50% the alloy consumed can be calculated using the following empirical formula, for all parameters given above as change in sulphur S, final Mg in melt Mgf

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Thus the Mg treatment of iron with cored wire injection is cheaper than sandwich process. This is one of the examples, but the cost of treatment varies from foundry to foundry because it depends on various parameters. Cost of one foundry cannot be applied to another foundry, it has to be well experimented.

Various advantages of cored wire injection process are summarized below according to above discussion.

  • Improved Metallurgical results achieved by precise addition of Mg Cored Wire resulting in close control of the residual Mg in the iron.
  • Very flexible with any composition of iron, especially with Sulphur which is very difficult to treat with other process
  • Lower loss than alloy process.
  • Better efficiency.
  • Reliable and consistent process.
  • Ease of operations.
  • Less slag formation and ladle buildup
  • Less slag inclusions in the castings.
  • Favorable cost of treatment.
  • Desulphurization and Spheroidization can be done simultaneously.
  • Reduced labor requirements.
  • Less capital investment and treatment cost.
  • Harmless to the environment as emission can be controlled and drawn off easily.
  • Re treatment / Trimming addition.
  • Process supports futuristic alloy like CG Iron production.
  • Scope for Total Automation.