GB1570454A

GB1570454A - Method of and vessel for adding treatment agent to molten metal

Info

Publication number: GB1570454A
Application number: GB19319/77A
Authority: GB
Original assignee: Yoshida Iron Works Co Ltd
Current assignee: Yoshida Iron Works Co Ltd
Priority date: 1976-07-15
Filing date: 1977-05-09
Publication date: 1980-07-02
Also published as: DE2726059C3; CA1092835A; FR2392126A1; DE2726059A1; DE2726059B2; CH633044A5

Abstract

The mixing of a treatment agent with molten metal is carried out by inserting a vessel which contains the treatment agent (1) and consists of a material which does not harm the molten metal into the molten metal. The treatment agent and the molten metal are stirred after the material of the vessel has been brought into contact with the molten metal. The vessel has a paper tube (2) which consists of kraft paper wound in layers. The vessel furthermore has covers (3, 4), of which the upper cover (3) can be provided with an apparatus for immersing the vessel in the melt. In such a process, treatment agents can be introduced deep into the melt without the substances already floating on the surface of the melt, such as, for example, sulphur, being reintroduced into the melt. <IMAGE>

Description

(54) METHOD OF AND VESSEL FOR ADDING TREATMENT AGENT TO MOLTEN METAL (71) We, YOSHIDA IRON WORKS COMPANY LIMITED, a Company organised and existing under the laws of Japan, of 19-8, 4-chome, Higashinaniwa-cho, Amagasaki-shi, Hyogo-ken, Japan, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to a method of and a vessel for adding a treating agent to a molten metal mass during, for example, a desulphurization or deoxidation, or component adjusting process.

In the case of desulphurization, for example, recently, the requirements for limitation on sulphur content (hereinafter referred to as S content) have become very severe, and depending on applications a so-called lowsulphur steel with an S content of less than 50 ppm is demanded. Therefore, with he present day steel making method using a blast furnace converter system, and theoretically, it is necessary to carry out sufficient desulphurization in the converter, that is, on the stage prior to steel making, so as to prepare a molten metal with an S content below the limit which allows refining in the steel making process. On the other hand, the circumstances of materials in the blast furnace are assuming an aspect which does not warrant optimism, making it difficult to obtain a molten metal with an S content below the refinable limit as described above.

It is the outside furnace desulphurization of molten iron that has made its advent as the most effective method of pre-treatment of or low-sulphur steel making from a molten metal which has a high S content due to such circumstances of the blast furnace. At present, various outside-the-furnace desulphurization systems have been invented and put to use. For example, the addition and agitation method, or the blowing-in method, are usually employed.

The addition and agitation method uses a plunging member to plunge a desulphurizing agent and auxiliary agent packed in a drum, can or the like into molten steel taken out into a ladle and agitate the same. With this, however, the initial cost is high owing to the installation of the drive unit, and on top of this, the plunging member has to be frequently replaced since it can be easily damaged in the belt, thus involving high running cost. Further, the sulphur which has once floated up to the surface of the melt as a slag tends to return to the molten steel or some of the desulphurizing agent and auxiliary agent burn out before they reach suitable positions in the molten steel, so that more amounts of desulphurizing agent and auxiliary agent than is necessary are consumed.

According to the blowing-in method, after a desulphurizing agent and auxiliary agent are charged into molten steel by a plunging member or the like, desulphurization is carried out by blowing N2 gas into the molten steel with the ladle sealed. In this case also, drawbacks similar to those described above in connection with the addition and agitation method remain unsolved.

In brief, in the conventional methods, the yield of a desulphurizing agent and its auxiliary agent (hereinafter referred to as treating agent) is generally low and the treating operation requires a long residence time (20-25 minutes), involving a loss of the thermal energy of the molten steel. Further, what should be particularly noted is that while recent researches have developed various types of desulphurizing agents, no decisive method of use, or addition, of such agents has been established. As a result, the costs of expensive installation and replaceable members such as plunging members and the useless consumption of more than necessary amount of treating agent have considerably raised the initial cost and the running cost.

Further, since a large amount of treating agent is charged into molten steel at a single pace therein, the resulting chemical reaction is violent, involving danger and producing smoke and dust in large amounts, incurring the possibility of causing environmental pollution, such as air pollution. On top of this, the treating effect is good only at the charged place and agitation for a prolonged period of time is required in order to uniformly distribute the treating effect throughout the molten metal in the ladle.

Further, referring to the outside-thefurnace deoxidizing of molten steel, among the most general methods of adding a deoxidizing agent is one in which it is formed into a lump which is then charged into molten steel and another in which it is fornied into a shell which is then shot into molten steel.

With these conventional methods, since the deoxidizing agent tends to burn or stay on the surface of the melt prior to produce a predetermined chemical reaction in the melt, lowering or dispersion of yield of the deoxidizing agent is inevitable. Thus, in the conventional methods, a stabilized deoxidation yield cannot be obtained despite the use of a large amount of treating agent.

An object of the present invention is to remedy or eliminate the aforesaid disadvantages heretofore involved in adding treating agents to molten metal.

According to the present invention, there is provided a method for the addition of a treating agent to a molten metal mass, which comprises adding the treating agent when contained within a vessel formed of paper cylindrically wound in layers with an air layer formed between adjacent paper layers, the paper being harmless to molten metal, and on combustion on contact with the molten metal causing the metal to be agitated and convected and distributing the treating agent homogeneously throughout the mass.

In a preferred method according to the invention a plurality of treating agents are added to the molten metal mass each agent being separately contained within a vessel formed of paper cylindrically wound in layers with an air layer formed between adjacent paper layers. This may be done once or several times, thereby uniforming the addition of the treating agent and cutting down the treating time and hence minimizing the loss of the thermal energy of the molten metal.

According to a feature of the invention there is provided a vessel for adding a treating agent to a molten metal mass which comprises a tube formed of paper wound in layers with an air layer formed between adjacent paper layers, a lid tightly closing opposite ends of said paper tube, and a treating agent packed in said paper tube.

This arrangement protects the treating agent packed in the interior from preburning and denaturing and improves the yield of treating agent. Further, it enables the efficient addition of the treating agent by adjusting the burning intiation time and burning time by adjusting the weight of said weight and the thickness of said paper tube.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which; Figures 1, 3 and 4 are longitudinal sections of treating agent adding vessels according to the present invention; Figure 2 is a front view of the vessel shown in Figure 1; Figures 5 and 6 show how to treat molten metal by using the vessels shown in Figures 1 to 4; Figure 7 is a longitudinal section of a further treating agent adding vessel according to the invention; Figure 8 shows a manner of treatment using the vessel shown in Figure 7; Figure 9 is a longitudinal section of another treating agent adding vessel accordin to the invention; Figure 10 is a front view of the vessel shown in Figure 9; Figure 11 shows a manner of treatment using the vessel shown in Figure 9;; Figures 12 and 13 are longitudinal sections showing modifications whereby the vessel shown in Figure 9 is improved; Figure 14 is a longitudinal section of another treating agent adding vessel according to the invention; Figures 15 and 16 show a modification whereby the vessel shown in Figure 14 is improved, in which Figure 15 is a longitudinal section and Figure 16 is a front view; Figure 17 is a longitudinal section of another treating agent adding vessel according to the invention; and Figures 18 and 19 show another vessel for adding a treating agent for molten metal according to the invention.

In Figures 1 and 2 showing a first treating agent adding vessel according to the invention, a treating agent is designated at 1 and 2 designates a paper tube containing the treating agent 1, with its opposite ends tightly closed by a lid 3 and a weight 4.

The paper tube 2 is formed of a combustible material, for example, kraft paper cylindrically wound in layers. An air layer is formed between adjacent paper layers, and it takes some time for combustion to proceed from the outermost to the innermost paper layer, whereby the self-burning oxidation, that is, the loss of the treating agent 1 packed in the interior is prevented from occurring before the treating agent reaches a suitable position in molten metal. The combustion time of the paper tube 2 varies with its wall thickness. According to experience with a converter, in the case of a wall thickness of 3mm, the paper tube travelled for 10 seconds while receiving radiant heat in the furnace and combustion in molten steel at 1600-17000C was completed in about 3 seconds.The material of which the lid 3 and weight 4 are made should be such that it will not adversely effect the components of molten metal to be treated, and the weight 4 has its front end shell-shaped so that it is capable of breaking through molten metal surface when it enters the molten metal.

In Figure 5 showing the manner of treatment in this case, the treating agent adding vessel, that is, capsule of the above construction is designated at A. When the capsule A is dropped into molten metal B taken into a ladle C, the treating agent 1 reaches a suitable reaction start position in the molten metal B without self-burning and oxidizing in advance. Such reaction start position can be suitably determined by adjusting the weight of the weight 4 or the wall thickness of the paper tube 2 according to calculations of the specific gravities of the capsule A and molten metal B. The self-burning of the paper tube 2 and the resulting emission of combustion gas at a suitable position in the molten metal B induce the agitation and convection of the molten metal and enhance the addition of the treating agent.

In order to make more effective the agitation and convection of the molten metal, as shown in Figure 3, the paper tube may be arranged in multiple construction (double construction in the illustrated example) including a central paper tube 2b having a hollow space 2c, with the treating agent 1 packed in a hollow space defined by the outer paper tube 2a. The outer paper tube 2a functions to prevent the loss of the treating agent 1 until it reaches the reaction start position, while the inner paper tube 2b enhances the blowing of the treating agent 1 by its combustion and by the concomitant emission of the air in the hollow space 2c and hence it enhances the agitation of molten metal. Further, in order to make the addition of the treating agent uniform, several capsules each packed with a suitable amount of treating agent may be charged into molten metal as suitable positions.

In the past, when the amount of molten metal to be treated was increased, the treating equipment became larger in size and more complicated and the treatment took a longer time. According to the present invention, however, no complicated apparatus is required and the operating time can be cut down.

The embodiment shown in Figure 6 utilizes an improvement in a conventional device, wherein D designates a plunging member and A designates said capsule packed with a treating agent. When the capsule A is plunged into the molten metal B by the plunging member D, the self-burning and eruptive actions of the paper tube 2 cause the agitation and convection of the molten metal B, so that there is no need for the plunging member D to execute agitating motion and hence the surface of the melt can be kept undisturbed. Therefore, there is no possibility that the sulphur which has formed into slag b will return to the molten metal.Further, if the front end portion of the plunging member D is covered with a special heat-resistant paper tube D', the plunging member D will not be damaged by the melt and it is only necessary to replace the inexpensive special paper tube D' and hence the running cost can be reduced.

In the embodiment shown in Figure 4, designated at 5 are sealing members for preventing the spontaneous combustion due to secular change or weathering of the treating agent contained in the paper tube 2 so as to protect the quality of the treating agent.

The sealing members are made of a material which, when melted, is harmless to the molten metal and they are, for example, in the form of tubes of thin metal foil or asbestos paper which cover the inner and outer peripheral surfaces of the paper tube 2 or which are wrapped around together with the kraft paper when the latter is wound. Thus, the sealing members keep the treating agent 1 in the capsule A out of contact with the outside air to protect it from denaturing and enable it to be used in the most effective condition.

In Figure 7 showing another embodiment, a treating agent adding vessel 1 0A comprises a capsule 12 made of a material the products of combustion of when, when melted, is harmless to molten metal and having a treating agent 11 enclosed therein, and an auxiliary member 6 projecting from the upper end of the capsule 12 for contact with the holder D of a plunging device. The auxiliary member 6 is cylindrically formed by winding kraft paper in layers. However, it is not limited thereto and it may be formed by similarly shaping asbestos paper or by boring wood so long at it is made of a selfburnable and self-eruptive material.

As for the manner of treatment in this case, as shown in Figure 8, the adding vessels 10A are suspended from the holder D of the plunging device and plunged into molten metal B in a ladle C, the capsules 12 burn to allow the treating agent 11 to be dispersed in the molten metal B, while some of the treating agent which tends to float up to the surface of the melt before it reacts with the molten metal is caused to stay in the molten metal by the self-burning of the auxiliary member 6 and by the fact that the concomitant emission of combustion gas causes bubbling. At the same time, the agitation and convection of the molten metal B are induced and the treating agent 11 reacts and is added.

Figures 9 and 10 show another treating agent adding vessel according to the invention, wherein 22 designates a tubular body; 23, a weight; and 26 designates a connecting tube for connection to the holder of a plunging device or agitating device. The tubular body 22 and connecting tube 26 are cylindrically formed by winding a combustible material, for example, kraft paper in layers as in the case of the paper tube 2 described above. However, no treating agent is packed therein. Therefore, as shown in Figure 12, the lower end of the tubular body 22' may be left open without providing a lid.

As for the manner of treatment in this case, as shown in Figure 11, the treating agent adding vessels 20A of the above construction are suspended from the holder D of a plunging device and they are plunged into molten metal B taken out into a ladle C as soon as a treating agent is charged thereinto in the conventional manner. Then, the self-burning of the tubular bodies 22 in the molten metal B and the concomitant emission of gas induce bubbling, causing the agitation and convection of the molten metal B whereby the molten metal and the treating agent are agitated. In addition, if the plunging device is rotated, the effect of addition of the treating agent is further enhanced.

In order to effectively carry out the agitation described above, it is necessary to adjust the combustion time by adjusting the wall thickness of the tubular body 22. For example, if the combustion time of the tubular body 22 is made substantially equal to the time necessary to complete a chemical reaction between the treating agent and molten iron, this is most effective and the loss of the thermal energy of the molten iron can be minimized.

Further, depending upon the volume of the molten metal B, not less than two vessels 20A may be installed, and according to this arrangement, even if the plunging device is to be rotated, there is no possibility of the driving device, having to be made larger in size at the sacrifice of the increase of the initial cost, since the resistance encountered during agitation is small as compared with that for a conventional iron vane even if the volume of the molten iron is large. Further, as shown in Figure 13, it is desirable to provide a number of small holes at two places on the tubular body 22", for example, one place immersed in molten metal and the other above the surface L of the melt. The absence of such small holes would involve the danger of the tubular body 22" being disengaged from the holder D by the expansion of the air in the hollow space of the tubular body 22".When the inside air is expanded, it is the small holes 7a in the upper region that allow the air to escape, while the small holes 7b existing in the molten metal B serve to increase the combustion area. It is preferable that a band 8 made of a refractory material or the like be provided on the tubular body 22" between the molten metal B and the outside air to prevent the holder from being damaged by the creeping up of the molten metal.

In Figure 14 showing a further embodiment of the invention, an adding vessel 30A comprises tubular bodies 32, a lid 33 and a connecting tube 36, with a suitable amount of treating agent 31 packed therein. The tubular bodies 32 and connecting tube 36 are cylindrically formed by winding a material which, when melted, has no adverse influences on the components of the molten metal, for example, kraft paper in layers.

The connecting tube 36 is used for connection to the holder of a plunging device.

The manner of treatment in this case is similar to that described in connection with Figure 11. Thus, a suitable number of treating agent adding vessels 30A of the above construction are each packed with a suitable amount of treating agent 31 and they are suspended from the holder D of a plunging device and plunged into molten metal B taken out into a ladle C. The vessels 30A carry the treating agent 31 contained therein to suitable positions in the molten metal B and then the self-burning of the tubular bodies 32 in the molten metal B and the concomitant emission of combustion gas produce bubbling which, in turn, induces the agitation and convection of the molten metal, whereby the molten metal B and treating agent are agitated and react with each other. Thereafter, the plunging operation described above is repeated several times.

In addition, in the illustrated example, two treating agent adding vessels are used, but when the amount of molten metal is relatively small, a single vessel may be repeatedly plunged. Further, when the amount of molten metal is large, not less than two members may be disposed at several places and plunged simultaneously or successively one by one, two by two and so on.

By the operation described above, the addition of a treating agent can be made relatively simple and effectively carried out.

In practice, the vessel is arranged as shown in Figures 15 and 16. More particularly, the resistance of the molten metal B during agitation is concentrated on a region of the connecting tube 46 near the surface L of the melt and said region is accompanied by a splash phenomenon. If the connecting pipe 46 its broken thereby, the agitation effect would be decreased. Therefore, it is necessary to reinforce the same from the standpoint of strength and in view of splash.

To this end, the region of the connecting tube 46 near the surface L of the melt is covered with a metal barrel or a refractory material 48.

With the combustion of the tubular bodies 42 and the emission of gas, the treating agent 11 is spouted into the molten metal, but some of the treating agent tends to float up to the surface of the melt before it reacts with the molten metal. In order to prevent this and improve the efficiency of addition, small holes 47b are formed in the connecting tube 46 below the surface of the melt. Then, combustion gas is emitted vigorously particularly around said small holes 47b, whereby the treating agent which tends to float up to the surface of the melt can be retained in the molten metal.

As the combustion of the tubular body 42 advances, the agitating action causes the molten metal B to fill the connecting tube 46 and the metal can easily stick to the front end d of the holder. In order to prevent this, small holes 47a are formed in the connecting tube 46 below the front end d of the holder. These small holes 47a allow the air filling the connecting pipe 46 to escape therethrough to the outside of the connecting tube 46. The fact that the molten metal B enters the connecting tube 46 means that the combustion of the tubular bodies 42 has advanced and hence the treating agent 41 has been spouted into the molten metal and its reaction with the latter has advanced. At this point of time, therefore, even if the connecting tube 46 is broken at the region of said small holes 47a or 47b, this does not cause any trouble.Further, since addition is accelerated in two ways, i.e., by agitation due to the entire treating agent adding vessel 40A and by the agitation and convection of the molten metal due to the self-burning and eruptive action of the tubular bodies 42, not only is the improvement of the treating effect achieved but also the loss of the energy of the molten metal is minimized by reduced operating time.

Figure 17 shows a treating agent adding vessel 50A according to the invention used for deoxidation. Tubular bodies 52 and a connecting member 56 are cylindrically formed by winding in layers a material which, when melted, is harmless to the components of molten metal, for example, kraft paper together with a deoxidizing material formed into a thin sheet or wire, for example, an aluminum foil 52b. Therefore, in a treating process, the self-burning of the tubular bodies 52 in the molten metal and the concomitant emission of combustion gas produce bubbling which, in turn, induces the agitation and convection of the molten metal, whereby the melt consisting of the molten metal and the treating agents, namely, the deoxidizing agent 51 and aluminum foil 52b is agitated.In this case, addition is accelerated in two ways, i.e., by the synergistic effect of the deoxidizing material included in the tubular bodies 52 and the deoxidizing agent enclosed in the interior and by the agitation and convection of the molten metal brought about by the self-burning and eruption of the tubular bodies 52.

In the embodiment shown in Figures 18 and 19, a treating agent adding member is designated at 60A and 62a designates a tubular body and 66 designates a connecting tube, these being arranged in multiple construction (double construction in the illustrated example of Figure 18) wherein a plurality (four in the illustrated example of Figure 19) of containers 62b each containing a suitable amount of treating agent 61 are received in a hollow space 9 defined between the tubular body 62a and the connecting tube 66.The tubular body 62a and connecting tube 66 are cylindrically formed by winding, for example, kraft paper in layers, while the containers 62a are in the form of barrels of different materials (for example, a paper barrel made of a selfburnable and self-eruptive material similar to that for said tubular body 62a and connecting tube 66, a barrel of thin metal, a barrel of refractory material and a barrel of asbestos paper) or barrels of the same material with different wall thicknesses. Such materials should, of course, be harmless to molten metal when melted.

According to this arrangement, the containers 62a are successively melted in the order of decreasing melting rate to allow the treating agent 61 in each container to be spouted and the molten metal and treating agent are agitated and react with each other.

In brief, there is a time lag in chemical reaction of the treating agent due to differences in the melting rate of the containers 62b in molten metal, whereby a diffusion effect is obtained, improving the treating effect and saving the operating time.

Whilst there have been described herein what are at present considered preferred embodiments of the several features of the invention, it will be obvious to those skilled in the art that modifications and changes may be made without departing from the essence of the invention.

WHAT WE CLAIM IS: 1. A method for the addition of a treating agent to a molten metal mass, which comprises adding the treating agent when contained within a vessel formed of paper

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of the melt and said region is accompanied by a splash phenomenon. If the connecting pipe 46 its broken thereby, the agitation effect would be decreased. Therefore, it is necessary to reinforce the same from the standpoint of strength and in view of splash. To this end, the region of the connecting tube 46 near the surface L of the melt is covered with a metal barrel or a refractory material 48. With the combustion of the tubular bodies 42 and the emission of gas, the treating agent 11 is spouted into the molten metal, but some of the treating agent tends to float up to the surface of the melt before it reacts with the molten metal. In order to prevent this and improve the efficiency of addition, small holes 47b are formed in the connecting tube 46 below the surface of the melt. Then, combustion gas is emitted vigorously particularly around said small holes 47b, whereby the treating agent which tends to float up to the surface of the melt can be retained in the molten metal. As the combustion of the tubular body 42 advances, the agitating action causes the molten metal B to fill the connecting tube 46 and the metal can easily stick to the front end d of the holder. In order to prevent this, small holes 47a are formed in the connecting tube 46 below the front end d of the holder. These small holes 47a allow the air filling the connecting pipe 46 to escape therethrough to the outside of the connecting tube 46. The fact that the molten metal B enters the connecting tube 46 means that the combustion of the tubular bodies 42 has advanced and hence the treating agent 41 has been spouted into the molten metal and its reaction with the latter has advanced. At this point of time, therefore, even if the connecting tube 46 is broken at the region of said small holes 47a or 47b, this does not cause any trouble.Further, since addition is accelerated in two ways, i.e., by agitation due to the entire treating agent adding vessel 40A and by the agitation and convection of the molten metal due to the self-burning and eruptive action of the tubular bodies 42, not only is the improvement of the treating effect achieved but also the loss of the energy of the molten metal is minimized by reduced operating time. Figure 17 shows a treating agent adding vessel 50A according to the invention used for deoxidation. Tubular bodies 52 and a connecting member 56 are cylindrically formed by winding in layers a material which, when melted, is harmless to the components of molten metal, for example, kraft paper together with a deoxidizing material formed into a thin sheet or wire, for example, an aluminum foil 52b. Therefore, in a treating process, the self-burning of the tubular bodies 52 in the molten metal and the concomitant emission of combustion gas produce bubbling which, in turn, induces the agitation and convection of the molten metal, whereby the melt consisting of the molten metal and the treating agents, namely, the deoxidizing agent 51 and aluminum foil 52b is agitated.In this case, addition is accelerated in two ways, i.e., by the synergistic effect of the deoxidizing material included in the tubular bodies 52 and the deoxidizing agent enclosed in the interior and by the agitation and convection of the molten metal brought about by the self-burning and eruption of the tubular bodies 52. In the embodiment shown in Figures 18 and 19, a treating agent adding member is designated at 60A and 62a designates a tubular body and 66 designates a connecting tube, these being arranged in multiple construction (double construction in the illustrated example of Figure 18) wherein a plurality (four in the illustrated example of Figure 19) of containers 62b each containing a suitable amount of treating agent 61 are received in a hollow space 9 defined between the tubular body 62a and the connecting tube 66.The tubular body 62a and connecting tube 66 are cylindrically formed by winding, for example, kraft paper in layers, while the containers 62a are in the form of barrels of different materials (for example, a paper barrel made of a selfburnable and self-eruptive material similar to that for said tubular body 62a and connecting tube 66, a barrel of thin metal, a barrel of refractory material and a barrel of asbestos paper) or barrels of the same material with different wall thicknesses. Such materials should, of course, be harmless to molten metal when melted. According to this arrangement, the containers 62a are successively melted in the order of decreasing melting rate to allow the treating agent 61 in each container to be spouted and the molten metal and treating agent are agitated and react with each other. In brief, there is a time lag in chemical reaction of the treating agent due to differences in the melting rate of the containers 62b in molten metal, whereby a diffusion effect is obtained, improving the treating effect and saving the operating time. Whilst there have been described herein what are at present considered preferred embodiments of the several features of the invention, it will be obvious to those skilled in the art that modifications and changes may be made without departing from the essence of the invention. WHAT WE CLAIM IS:

1. A method for the addition of a treating agent to a molten metal mass, which comprises adding the treating agent when contained within a vessel formed of paper

cylindrically wound in layers with an air layer formed between adjacent paper layers, the paper being harmless to molten metal, and on combustion on contact with the molten metal causing the metal to be agitated and convected and distributing the treating agent homogeneously throughout the mass.

2. A method as claimed in claim 1, wherein a plurality of treating agents are added to a molten metal mass, each agent being separately contained within a vessel formed of paper cylindrically wound in layers with an air layer formed between adjacent paper layers.

3. A vessel for adding a treating agent to a molten metal mass according to the method of claim 1 or 2, comprising a paper tube formed of paper wound in layers with an air layer formed between adjacent paper layers, a lid tightly closing an end of said paper tube, and a treating agent packed in said paper tube.

4. A vessel as claimed in claim 3, wherein the paper tube is of multiple construction wherein an innermost paper tube has its hollow space left vacant while the hollow space defined by an outer paper tube is packed with a treating agent.

5. A vessel as claimed in claim 3, wherein the inner and outer peripheral surfaces of the paper tube are treated to make such surfaces airtight.

6. A vessel as claimed in claim 3, wherein an airtight membrane is wound in a layer interleaved with the layers of paper.

7. A vessel according to any of claims 3 to 6 wherein a weight tightly closes the opposite end of the paper tube.

8. A vessel as claimed in an one of claims 3 to 6 wherein the paper tu e is provided with means whereby the tube may be suspended from a plunging device by means of which the tube is introduced into the molten metal mass.

9. A vessel as claimed in claim 8 wherein means for suspending the paper tube from the plunging device comprises a connecting tube having a plurality of holes connecting with the interior thereof.

10. A vessel as claimed in any one of the preceding claims 3 to 9 wherein a deoxidizing material formed into a thin sheet or wire is interlaced with the tubular body.

11. A vessel as claimed in any one of the preceding claims 3 to 10 wherein the paper tube comprises several containers each containing an amount of the same kind of treating agent.

12. A vessel as claimed in any one of the preceding claims 3 to 10 wherein the paper tube comprises several containers each containing a different kind of treating agent.

13. A vessel as claimed in any of claims 3 to 12 wherein the paper is kraft paper.

14. A vessel as claimed in any one of the preceding claims 3 to 13 substantially as hereinbefore described with reference to the drawings.