GB2078785A - Adding Volatile Refining Agents to Molten Steel - Google Patents

Abstract

A method for adding lighter-than- steel, low solubility, volatile, active refining agents into molten steel that is safe, reduces or eliminates the smoke that accompanies known methods of adding such agents and which comprises submerging a consumable solid body of a pressed mixture of materials comprising the refining agent and an inactive material or materials, the composition of the solid body being predetermined to allow a controlled release of refining agent into the steel as the solid body dissolves at a rate at which the refining agent can be made available to the molten steel is that which will (1) on a continuing basis replace the refining agent that is being consumed by the impurities in the steel; whilst at the same time (2) not allow the concentration of the refining agent in the steel to exceed or substantially exceed its solubility limit at any time.

Description

SPECIFICATION Method for Adding Refining Agents to Molten Steel This invention relates to a method for adding lighter-than-steel, low solubility, volatile, active refining agents, hereinafter referred to as of the type described, into molten steel.

Impurities such as sulphur, oxygen, phosphorous, oxides of silicon, manganese and carbon are known to affect the processing as well as the mechanical and physical properties of steel, nickel and cobalt alloys.

For example, sulphur causes hot shortness; oxygen causes edge cracking; while sulphur and oxygen cause surface imperfections; all of which affect the yield and costs of steel manufacture.

In addition, sulphur and oxygen are known to reduce ductility and toughness; sulphur, oxygen and phospherous are known to lower the ductile-brittle transition temperatures and forming characteristics; while sulphur, oxygen, phosphorous and carbon are known to detract from soft magnetic characteristics of steels and alloys.

Because of the increasing awareness for the need to control and eliminate these impurities in steel, a great deal of activity has been focused on developing systems or techniques that fill this need.

Calcium and magnesium are both excellent deoxidizers and desulphurisers and as such some of the work has focused on these elements and has resulted in patented calcium and magnesium alloy additives; pneumatic injection systems, and submersion techniques for adding calcium, magnesium and their alloys.

Both magnesium and calcium are lighter than steel, have limited solubility and boil at temperatures lower than molten steel. A possible way to add lighter-than-steel material is via some sort of submersion technique. However, because these elements boil at low temperatures and have limited solubility, rapid vapourization occurs as they are added to liquid steel, and that which is not immediately consumed by the steel rushes to the surface of the steel causing metal eruptions and/or violet explosions, flare and smoke. Thus, something other than simple submersion techniques are required to avoid these problems.

Prior art teaches a variety of submersion techniques which include pneumatic injection systems for adding calcium and magnesium in fine grain particulate form, U.S. Patent 3,998,625 and U.S.

Patent 4,123,258, as well as the use of containers, U.S. Patent 2,915,386, for protecting such additions from contact with the molten ferrous metal until some time after the container with the treating agent is submerged, or covered, by the molten steel. In one case, a cylinder containing the treating agent is submerged, U.S. Patent 2,595,282, into the ladle after it is filled with the molten metal, while in other cases the container filled with the treating agent is placed and attached to, U.S.

Patent 3,934,862, or near, U.S. Patent 3,942,775, the ladle bottom prior to the filling of the ladle.

In these cases, once the container melts, or disintegrates, the addition agent is exposed to the liquid steel, and if the addition agent is lighter-than-steel, it quickly rises to the slag, and if the addition agent is calcium or magnesium, flaring, metal eruption and smoke result with a large portion of the calcium or magnesium being wasted to the slag and the atmosphere.

Experience teaches that 'solid' shapes or pure magnesium or calcium can be submerged into high nickel alloys without these problems occurring, and small amounts of calcium can be submerged into iron with little difficulty. However, submersion of solid shapes of these elements into steel results in violet explosions when magnesium is added, and severe metal eruptions and flaring when calcium is added. The difference noted in the activity of these elements in different steels and alloys is considered to be related to solubility difference with their solubility in steel being the least.

For example, in the case of calcium, Sponseller, D.L., Trans Net Society AIME, Vol. 230, June 1964, shows its solubility to be very low in steel but increases substantially as the nickel or carbon content is increased as such high nickel and high carbon content alloys react less violently to calcium additions.

Immediately upon calcium dissolving, it reacts with the impurities in the steel, which results in compounds that float to the surface of the steel, thus removing the impurities from the molten steel.

Various methods have been used in molten iton to reduce this violent activity by slowly introducing magnesium metal into the iron under rigidly controlled systems. One of these methods for reducing the violence is to impregnate porous bodies with magnesium metal and to introduce these magnesium impregnated porous bodies into the molten ferrous metal. Under these conditions, the impregnated magnesium metal is released at a slow enough rate that the violence is held to a minimum.

Among the known porous bodies which have been used with some success for this purpose are porous coke, U.S. Patent 3,321,304, carbon, graphite and ceramic bodies, U.S. Patent 4,083,71 6, such as quicklime, lump limestone or dolomite and the like.

In addition, magnesium has been infiltrated into porous iron bodies, U.S. Patent 3,902,892.

Among these iron bodies is sponge iron in which the iron particles are very small and are sintered together to form a porous structure.

Another method mentioned as prior art in U.S. Patent 3,902,892 is iron briquettes containing magnesium produced by dry pressing together iron particles and magnesium particles, both of which preferably are from 4-60 mesh i.e. approximately 1/4" to 1/6ore.

These methods, basically designed for magnesium inoculation, or desulphurisation of iron, are comparable to calcium treatment of iron. However, in all cases they are not suitable for use in stell for a number of reasons that include: the possibility of carbon pick-up from the coke; or the pick-up of exogenous inclusions from the ceramic bodies; or hydrogen pick-up from the binders used in the castable ceramic bodies, etc., steel being more sensitive to these impurities than iron.

In addition, there are limitations as to the chemical makeup of those products made with porous bodies since the amount of magnesium (or calcium) that these bodies can hold depends upon the amount of porosity available in the bodies, or in case of the ceramic bodies is limited to the amount of magnesium that the ceramic mix can hold and still be a castable ceramic. The specific chemical makeup is also limited to single elements or alloys, since the porous bodies must be submerged into a liquid bath of the element or alloy in order to fill the pores of the body. Mixtures of immiscible elements, therefore, cannot be used to fill the pores.

In addition, in the case of castable ceramics, elements that react with moisture, or with the binder such as calcium, cannot be used because they would react with the moisture or the binder to destroy the strength of the cast shape, while the calcium would be partially or wholly consumed by the reaction.

In the case of pressed together briquettes of iron and magnesium (caicium), when these are added to liquid steel via normal tap stream addition methods, large quantities of smoke and flare develop with most of the magnesium (calcium) reacting with the slag or the atmosphere. When such material is packed into a sealed steel cylinder and the cylinder containing the briquettes is submerged into a filled ladle of steel, the cylinder melts exposing the briquettes all at one time. The briquettes, being lighter than the steel, quickly float to the surface causing flaring and smoke as they reach the surface of the steel, resulting in most of the magnesium (calcium) being wasted to the slag and atmosphere.

An object of the invention is to provide a new and improved method for adding a refining agent of the type described that is safe and reduces or eliminates the smoke that accompanies known methods of adding a refining agent of the type described. A secondary object is to provide a more effective, efficient and cost effective method without the need for capital equipment for the user.

According to the present invention I provide a method of adding a refining agent of the type described to molten steel comprising the steps of submerging and maintaining submerged a consumable solid body of a pressed together mixture of materials comprising the refining agent and an inactive material or materials, the composition and surface area of the solid body being predetermined to allow a controlled release of a predetermined amount of the refining agent into the steel as the solid body dissolves at a predetermined rate that does not allow the refining agent to exceed or substantially to exceed the solubility limit in the steel.

This method is not restricted by the disadvantages mentioned above and thus the invention provides a more flexible, efficient, smoke eliminating method for adding a refining agent of the type described to molten steel that reduces or prevents air pollution.

It is to be noted that this invention is characterised by: the submersion of a solid body containing an active refining agent, not a refining agent in fine grain particulate form, into molten steel; being a mixture, not an alloy, of at least two pressed together materials and as such can be made up of any conceivable composition, with the composition being easily controlled so as to prevent the addition of undesirable elements into the steel; bodies much larger than briquettes such as to provide the means of properly holding the additive submerged while it is being dissolved in the steel at a reduced melting rate necessary for optimum release of the agent into the steel.

The controlled release may be such that the maximum rate at which the refining agent can be made available to the molten steel is that which will (1) on a continuing basis replace the refining agent that is being consumed by the impurities of the steel; while at the same time (2) does not allow the concentration of refining agent in the steel to exceed or substantially exceed it solubility limit at any time.

Preferably the refining agent is calcium, magnesium or a rare earth.

The inactive material may be selected from one or more of the following, iron, aluminium, elements which will alloy with the steel and/or oxides thereof.

The solid body may contain for steel alloying or deoxidation purposes one or several of the following: Al, Ba, Mn, Si, alloys or mixtures thereof.

The body may contain between 1% and 99% of the refining agent and preferably comprises 20% refining agent and 80% iron or iron and usual incidentals such as to comprise, for example, steel.

The body may be at least partly encapsulated, for example, with steel, aluminium or copper for the purpose of providing a longer shelf life.

When the steel to be treated is a carbon, low alloy or stainless steel and the refining agent is calcium, the calcium content of the body may be related to the surface area thereof by the following relationship: Cas Ca=or less than X t where: Ca is the weight of calcium in the body in pounds.

X is the melting time of the body= kW S.A.

Cas is the solubility of calcium in the particular steel t is the minimum time required for the calcium consumption by the steel k=27.36+ 10% (for carbon, low alloy or stainless steel) W is the weight of the body in pounds S.A. is the surface area of the body in square inches.

The body may be of cylindrical form and have an axial opening therein and the solid body may be placed on the end of a refractory covered vertical rod which is used to submerge and hold submerged the body and the rod may be the stopper rod that is used in teeming the steel and as such the body is placed in the ladle prior to tapping the furnace.

The steel which is dealt with herein is usually low carbon steel, containing carbon from .03% to .20%, medium carbon steel containing .20% to .50%, or high carbon steel containing .50% and higher carbon. In some cases the steel may contain chromium from 0 to 65% and in some cases may contain nickel and/or cobalt up to 55%. It is found that refining which is the subject of this invention is most useful in the carbon steels or other steels above enumerated. In high nickel alloys the solubility of the refining agent is much greater and therefore addition problems are non-existent and as such this method is not as important in these types of alloys.

The invention will now be described in more detaii by way of example.

As outlined above, additives to steel such as calcium and its alloys or mixtures when added to molten steel by normal means cause intense heat, flaring and large volumes of smoke such that at times the whole melt shop can be filled with irritating smoke. The blinding flare and smoke is due to the greater percentage of the calcium reacting with the oxygen in the atmosphere rather than with the impurities in the steel, resulting in very poor utilisation of the calcium.

If these additions are made by a simple submersion technique, dangerous molten metal eruptions occur with flaring and smoke.

I have found that an active refining agent such as calcium can be more effectively, safely, efficiently added with little or no flare and smoke via a submersion method if the agent is added no faster than a maximum amount that does not exceed its solubility linit in the molten steel, and that as the calcium. is consumed, it is replaced at no more than the maximum RATE that does not exceed its CONSUMPTION RATE and SOLUBILITY LIMIT.

I have found that this RATE can be controlled by mixing the refining agent, which is an active element and by definition is an additive that would normally cause the liquid steel to churn, boil and erupt if submerged into molten steel, with at least one other inactive material which does not cause activity in the molten steel, in the proper formulation, and pressing this mixture into a solid body of pressed together material of the appropriate surface area dimensions, such that upon submersion of said solid material into molten steel and holding near the bottom of the molten bath until dissolved, the desired amount of refining agent is released into the steel in the required minimum time span, which is dependent upon the dissolution time of the solid material, necessary to ensure complete consumption of the refining agent by the steel.The optimum time frame can be calculated using known solubility limits and consumption rates for the scavenger.

By controlling the rate at which the refining agent is released into the molten steel so that the solubility limit is never exceeded or substantially exceeded, excess refining agent is not available to vapourise in the steel to cause explosions or to rise to the metal surface to react with the slag or air to cause flaring and air pollution. Thus, the explosions, flareups or air pollution indicative of other adding mehods are reduced and eliminated with this method.

This controlled release of the refining agent into the steel results in more efficient utilisation of the refining agent since none of it floats to the slag to be wasted by the slag or by the oxygen in the air.

Although the invention is applicable to calcium, magnesium and possibly rare earths which are the active agents for reducing impurities in steel, the invention hereinafter will be described with reference to calcium due to its particular importance in steel making today.

Adding calcium to steel in the normal way, i.e. via tap stream additions, as shown by Example 1, results in flaring and voluminous smoke.

Example 1 Heat size: 40 ton of carbon steel Addition: 5 Ibs. calcium per ton of steel.

Addition Method: Total addition added to the tap stream in five cloth bags.

Result: Blinding and intensely hot flaring, and voluminous smoke that filled the melt shop for 3 to 5 minutes before it all rose to the melt shop roof, and out through the louvres to be carried away by the wind to the surrounding community.

Benefit: Man hours required to remove defects from the surface of the 5x5 billets were reduced by 40%.

During my past experience, I have learned that submersion of calcium and calcium alloys provides one of the best ways of adding calcium to steel. However, surprisingly, I have learned that while using simple submersion techniques, calcium activity ranges from near explosive, Example 2, to calm, depending upon the steel or alloy being treated.

Example 2 Heat Size: 40 ton of carbon steel.

Addition: 1-1/4 Ib. calcium per ton of steel.

Addition Method: One piece, weighing 50 Ibs. by 12" dia.x 12" high was mounted on a steel pole and subsequently submerged into the ladle of steel.

Result: 1-1/2 minutes after the solid piece of calcium was submerged into the ladle, a flare extending the full diameter of the ladle and twice as high suddenly developed with spurts of metal eruptions as high as two feet and over the sides of the ladel wall.

Fortunately, I have also learned that when the desired amount of calcium is added in several submersion increments, instead of in one submersion addition, the activity is reduced substantially, and the near explosive conditions are reduced to tolerable metal splashing while at the same time the effectiveness of the calcium is increased and the amount of smoke evolved is somewhat reduced.

However, adding several submersion additions to large ladles of tonnage stel is impractical from an operations point of view.

In this invention I have learned that a single submersion addition, Example 3, can replace several small submersion additions of calcium, to have the same or better end-effect providing (1) the calcium is mixed with iron and then formed into a solid pressed together material, and (2) the calcium percentage of the resultant additive is carefully selected and balanced with the melting or dissolution time of the solid additive itself in such a manner that there is sufficient time for the calcium to be totally absorbed and consumed by the steel as the additive dissolves, so that virtually none of the calcium is available to vapourise and rush to the surface of the molten steel to cause metal splashing and to react with the air to cause smoke and air pollution.

Example 3 (The Invention) Heat Size: 40 ton of carbon steel Addition: 1-1/4 Ib of calcium per ton of steel as contained in CaFe billet with 20% calcium.

Addition Method: 1 piece of CaFe billet weighing approximately 250 Ibs.x9" dia.x30 inches was submerged into the ladle of molten steel.

Result: No flaring, metal eruption, or smoke was observed.

Benefit: Man hours saved in surface conditioning of 5x5" billets was comparable to a 5 Ib. calcium per ton tap stream addition.

Example 1 illustrates the problems associated with adding calcium and calcium additives to the tapping stream. Because of the smoke accompanying such additions, EPA and OSHA restrictions tend to limit and in some cases stop calcium additions entirely causing the steel maker to lose the cost and quality benefits of calcium additives.

Example 2 shows that simple submersion techniques are not applicable to calcium aditions to steel and indeed can be unsafe.

Example 3 illustrates that a properly formulated solid mixture can be submerged safely in molten steel without the problem of flaring, metal eruption and smoke, and that such an addition can be more efficient since a 1-1/4 Ib calcium/ton addition via a CaFe billet produces comparable effects upon the steel as tap stream additions using 5 Ibs. of calcium/ton of steel.

The product of this invention is characterised by a consumable body of pressed together material consisting of calcium and at least one other material. The shape and composition of the pressed together material is balanced so as to provide a controlled release of calcium as the shape dissolves into the molten steel. The time for dissolution of the shape being dependent upon the surface area or dimension of the shape selected. To illustrate this effect more fully, I have listed in seven columns of Table I relevant data of different cylindrical shapes of CaFe pressed together material showing how melting time is affected by dimensional changes.

Table I Relationship Between Billet Dimensions, Surface Area and Melting Time for 25% Calcium Billet D1 D2 h Wt. Surface Melt time (") '') (") (Ib.) Area S.A./Wt. (mien) 8.5 1.75 30.75 230 923 3.9 7.0 12 2.75 20 304 968 3.2 8.59 10 2.75 29.5 304 1,072 3.5 7.76 8 2.75 48.5 304 1,308 4.3 6.36 6 2.75 96.0 304 1,854 6.1 4.49 4 2.75 323.0 304 4.072 13.4 2.04 3 2.75 1900.0 304 17,909 58.9 0.47 D, is the outside diameter of the cylinder in inches.

D2 is the inside diameter of the hole in the cylinder in inches.

h is the height of the cylinder in inches.

Column 4 is the weight of the billet in pounds.

Column 5 is the surface area.

Column 6 is the surface area/billet weight.

Column 7 is the melting time in minutes, Thus, when one wishes to add a certain percentage of calcium to a ladle of steel, a composition and billet size is selected that will provide the deisred amount of calcium for the dissolution or melting time required to ensure complete consumption by the steel.

The data for the above Table was developed using the fact that for a given mass, the melting rate is inversely related to the Surface Area that is exposed to the molten steel, and this can be represented by a simple equation: X=k Y X=melting time for cylinder k=a constant Y=Surface Area/Weight.

k is determined using the empirical data derived from the 8-1/2 inch diameter billet, i.e. 27.36.

This addition method, being an improvement over the technique of submersing a desired calcium addition via several independent submersions, is more practical for use in large ladles of tonnage steels. The rate of calcium released into the steel is controlled to that rate at which the calcium can be consumed by the steel. This rate can be estimated using the following formula: Ca Solubility Limit in Particular Steel Rate of calcium release= 1 80 Sec (time required for Ca to dissolve and react) The body of pressed together material is made by pressing together small particles of non-active material such as iron powder and active metal particles, such as Ca, at pressures up to 60,000 psi into a solid form that is 75% to 100% theoretical density. A currently preferred density range is between 87 and 93% theoretical.Although the particle size is not critical, a range of 100 to 8 mesh is preferred due to the better availability of such particle sizes. The form chosen to be most practical for manufacture and use is a cylinder of 9 or 12 inch diameter with a 2 to 8 inch axial hole extending the full length of the cylinder. The hole is used to position the cylinder on one end of a refractory covered stopper rod.

The other end of the rod being firmly attached to a 'counter weight' of sufficient magnitude to keep the light cylinder near the bottom of the filled ladle. Using the stopper rod assembly that is properly counter weighted, the cylinder is submerged into a ladle of molten steel so that the cylinder comes to rest at a position close to the ladle bottom. Positioning the assembly before tap is also feasible. As the molten steel comes into contact with the cylinder, the cylinder is heated up to its melting point, and it begins to dissolve into the molten steel releasing the calcium at a controlled rate depending upon the melting time of the cylinder itself.

As the calcium dissolves into the molten steel, a reaction takes place with the impurities combining therewith and the resultant products of reaction being lighter than the steel float to the surface of the molten steel and into the slag. The total time necessary for the 'dissolved' calcium to react and the resultant products of reaction to rise to the slag is estimated by Wahlster; Radex Rundschau, 1969, pp 478--494, at approximately 180 seconds.By using (1) a properly selected calcium percentage for the make-up of the cylinder to provide the desired amount of calcium addition, and (2) the proper cylindrical dimensions to provide the surface area to control the 'time' for dissolution of the cylinder and, thus, the simultaneous release of the calcium during this time frame; the RATE of calcium released into the steel is thereby carefully controlled. By adjusting the calcium percentage in a given size billet to obtain the maximum desired RATE, as determined by Equation 1, the calcium made available per minute is thereby controlled to (1) provide a continuing basis sufficient calcium to replace that which is being consumed by its reaction with the impurities in the steel, and at the same time (2) limit the concentration of calcium in the steel so that any given moment it does not exceed its solubility limit.Thus, all the calcium added is either in solution or is consumed in the refining reaction, with none available to rise to the slag to cause explosions, flareups or air pollution (smoke).

While the body of the pressed together material may be in many various shapes, it is more convenient to provide a solid cylindrical form of the mixture with an axial hole through it for ease of implementation.

Iron is primarily used as the other ingredient of the composition for the cylindrical shape, but in some cases the cylindrical form may be made up of active calcium and other inactive material so as to better control the release of the calcium into the molten steel or to effect better deoxidation. These inactive material may include Fe, Al, steel alloying elements, their oxides, CaO, CaC2,CaF, Calcium Cyanamide and mixtures thereof. The calcium content itself can range from 1% to 99%, as can any of the other ingredients.These are pressed together with the calcium under such pressure that they are substantially bonded therewith and may be introduced into the molten steel either by (1) submersion and suspension of the cylinder into the steel, or (2) the cylinder being ridigly suspended and the ladle or molten steel raised about the cylinder, or (3) the slow immersion of the product into a shallow bath such as into a tundish.

The scavenging material which I use is primarily calcium metal, but commercially available calcium alloys, such as CaSi, CaMnSi, CaSiBaAl, CaC2, CaAI, and the like can be used in part or wholly as the calcium source for the cylinder.

Submersion of calcium and calcium additives via the described invention not only provides a way of reducing and eliminating the blinding flare and the poiluting smoke that accompanies its normal tap stream addition, but it provides a cheaper way for treating steel with calcium via substantially increasing the efficiency of the calcium addition.

For example, the normal tap stream additions of calcium result in a 3 to 5% recovery with most of the calcium reacting with the air. This invention forces all the calcium to react with the steel and thereby prevents its reaction with the air and, as such, can increase calcium's efficiency as much as 20 fold. Therefore, even though the forming of this product into the desired shape produces a more expensive product, the cost benefits due to increased efficiency overshadows the product cost to provide a cheaper way of treating steel with calcium.

In addition, the invention only requires a counter weight to hold the cylinder deep in the molten steel and perhaps a couple of 'I' beams placed in a horizontal position to the stopper rod assembly in order to rest the assembly on the ladle side walls and, as such, no captial investment is required to use this invention.

The scavenging material as stated above may be of various shapes but more conveniently cylindrical and for greater shelf life may be encapsulated either fully or partly with steel, aluminium, iron, steel, copper or other metals for this purpose.

Claims (20)

Claims

1. A method of adding a refining agent of the type described to molten steel comprising the steps of submerging and maintaining submerged a consumable solid body of a pressed together mixture of materials comprising the refining agent and an inactive material or materials, the composition and surface area of the solid body being predetermined to allow a controlled release of a predetermined amount of the refining agent into the steel as the solid body dissolves at a predetermined rate that does not allow the refining agent to exceed or substantially to exceed the solubility limit in the steel.

2. A method according to Claim 1 wherein said controlled release is such that the maximum rate at which the refining agent can be made available to the molten steel is that which will (1) on a continuing basis replace the refining agent that is being consumed by the impurities of the steel; while at the same time (2) does not allow the concentration of refining agent in the steel to exceed or substantially exceed its solubility limit at any time.

3. A method according to any one of the preceding claims wherein the refining agent is calcium, magnesium or a rare earth.

4. A method according to any one of the preceding claims wherein the inactive material is selected from one or more of the following, iron, aluminium, elements which will alloy with the steel and/or oxides thereof.

5. A method according to Claim 4 wherein when the refining agent is calcium, the inactive material consists of one or more of the following: Al, Fe, their oxides, CaO, CaF, calcium cyanamide, steel alloying elements and mixtures thereof.

6. A method according to Claim 4 or Claim 5 wherein the solid body contains, for steel alloying or deoxidation purposes, one or several of the following: Al, Ba, Mn, Si, alloys or mixures thereof.

7. A method according to any preceding claim wherein the solid body contains between 1% and 99% of the refining agent.

8. A method according to Claim 7 wherein the body comprises 20% refining agent and 80% iron or iron and usual incidentals.

9. A method according to any one of the preceding claims wherein the solid body has a theoretical density of 75 to 100%.

10. A method according to Claim 9 wherein the solid body has a theoretical density of 87 to 93%.

11. A method according to any one of the preceding claims wherein the body is at least partly encapsulated.

1 2. A method according to Claim 11 wherein the body is at least partly encapsulated with stell, al, or Cu.

1 3. A method according to any one of the preceding claims wherein the steel to be treated is a carbon, low alloy or stainless steel, the refining agent is calcium and the calcium content of the body is related to the surface area thereof by the following relationship: Ca5 Ca=or less than X t where: Ca is the weight of calcium in the body in pounds.

X is the melting time of the body kW S.A.

Cas is the solubility of calcium in the particular steel t is the minimum time required for the calcium consumption by the steel k=27.36+ 0% (for carbon, low alloy or stainless steel) W is the weight of the body in pounds S.A. is the surface area of the body in square inches.

14. A method according to any one of the preceding claims wherein the body is of cylindrical form.

1 5. A method according to Claim 1 5 wherein the body has an axial opening therein.

1 6. A method according to any one of the preceding claims wherein the solid body is placed on the end of a refractory covered vertical rod which is used to submerge and hold submerged the body.

1 7. A method according to Claim 1 6 wherein the refractory covered rod is the stopper rod that is normally used to teem the steel and as such is placed in the ladle prior to tapping the furnace.

1 8. A method according to any one of the preceding claims wherein the method is performed in a ladle.

1 9. A method substantially as hereinbefore described.

20. Steel when produced by a method as claimed in any one of the preceding claims.