CA1070119A - Steelmaking process - Google Patents
Steelmaking processInfo
- Publication number
- CA1070119A CA1070119A CA239,336A CA239336A CA1070119A CA 1070119 A CA1070119 A CA 1070119A CA 239336 A CA239336 A CA 239336A CA 1070119 A CA1070119 A CA 1070119A
- Authority
- CA
- Canada
- Prior art keywords
- charge
- steel
- melting
- scrap
- vessel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Manufacture And Refinement Of Metals (AREA)
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Process for producing heats of molten steel directly from solid materials without the need of separate refining steps or time periods. More specifically, there is disclosed a continuous process for producing steel, which comprises: providing in an oxy-fuel fired melting vessel a charge of solid steel of preselected composition containing the principal elements and in proportions corresponding substantially to those of the desired steel end product, and melting said charge and converting the resultant liquid metal to a solid form in the absence of a refining step and a slag removal step. In a preferred form, the metal is tapped at a temperature of at least 2800°F.
Process for producing heats of molten steel directly from solid materials without the need of separate refining steps or time periods. More specifically, there is disclosed a continuous process for producing steel, which comprises: providing in an oxy-fuel fired melting vessel a charge of solid steel of preselected composition containing the principal elements and in proportions corresponding substantially to those of the desired steel end product, and melting said charge and converting the resultant liquid metal to a solid form in the absence of a refining step and a slag removal step. In a preferred form, the metal is tapped at a temperature of at least 2800°F.
Description
7~
BACKGROUND OF THE INVENTION
There is known method and means for melting solid ma-terials bearing iron, such as scrap metal, with heat produced by the combustion of a fuel and essentially pure oxygen. It is also known to add reagents to the melt stream or the melt receiving vessel for controlling the steel melt composition and/or refining the steel.
It is always a desideratum in the steel industry to reduce the cost of producing steel. Considerable effort is and has been made toward the development of techniques for direct - melting of steel on a continuous basis and toward eliminating any processinc, steps.
It is known in the electric furnace steelmaking art to segregate steel scrap and to select the grades of scrap which together contain the constituents necessary to make the desired heat. In the electric furnace pra~tice there are involved the melt-down and/or oxidizing period and the refining period.
The electrodes in the basi~ electric furnace melt the charge portion directly beneath the electrodes and eventually a pool of collected molten metal is formed on the furnace hearth.
~he pool provides a source of radiant heat for assisting in melting the remainder of the charge. During the melting process, a slag is formed on the surface of the pool.
In a single slag process, the slag is first oxidized and then rendered reducing by adding the required materials during the refining period; in a double slag process, the initially formed slag is removed through the charging door and then a second . . .
slag is formed by adding materlals.
.' ~
. ........................................................................ . .
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It will be apparent that both the single slag and the double slag processes are batch or intermittent type operations as opposed to continuous melting operations wherein raw materials are being continuously fed to and discharged from the meltîng vessel.
OBJRCTS AND SUMMARY OF THE I~VENTION
__.
It is an object oE this invention to provide a method Eor the production of steel which obviates the need for refining the molten metal after melting.
It is another object of this invention to provide an - 10 improved method for the continuous melting of iron bearing material in solid form and directly producing a steel having the desired end chemistry.
In one particular aspect the present invention provides a continuous process for producing steel, which comprises providing in an oxy-fuel fired melting vessel a charge of solid steel of ; - preselected composition containing the principal elements and in proportions corresponding substantially to those of the desired steel end product, and melting and tapping said charge at a temper-ature of at least 2800F, and converting the resultant liquid metal
BACKGROUND OF THE INVENTION
There is known method and means for melting solid ma-terials bearing iron, such as scrap metal, with heat produced by the combustion of a fuel and essentially pure oxygen. It is also known to add reagents to the melt stream or the melt receiving vessel for controlling the steel melt composition and/or refining the steel.
It is always a desideratum in the steel industry to reduce the cost of producing steel. Considerable effort is and has been made toward the development of techniques for direct - melting of steel on a continuous basis and toward eliminating any processinc, steps.
It is known in the electric furnace steelmaking art to segregate steel scrap and to select the grades of scrap which together contain the constituents necessary to make the desired heat. In the electric furnace pra~tice there are involved the melt-down and/or oxidizing period and the refining period.
The electrodes in the basi~ electric furnace melt the charge portion directly beneath the electrodes and eventually a pool of collected molten metal is formed on the furnace hearth.
~he pool provides a source of radiant heat for assisting in melting the remainder of the charge. During the melting process, a slag is formed on the surface of the pool.
In a single slag process, the slag is first oxidized and then rendered reducing by adding the required materials during the refining period; in a double slag process, the initially formed slag is removed through the charging door and then a second . . .
slag is formed by adding materlals.
.' ~
. ........................................................................ . .
ca/~
- .
' ' , .
' .
~7~
It will be apparent that both the single slag and the double slag processes are batch or intermittent type operations as opposed to continuous melting operations wherein raw materials are being continuously fed to and discharged from the meltîng vessel.
OBJRCTS AND SUMMARY OF THE I~VENTION
__.
It is an object oE this invention to provide a method Eor the production of steel which obviates the need for refining the molten metal after melting.
It is another object of this invention to provide an - 10 improved method for the continuous melting of iron bearing material in solid form and directly producing a steel having the desired end chemistry.
In one particular aspect the present invention provides a continuous process for producing steel, which comprises providing in an oxy-fuel fired melting vessel a charge of solid steel of ; - preselected composition containing the principal elements and in proportions corresponding substantially to those of the desired steel end product, and melting and tapping said charge at a temper-ature of at least 2800F, and converting the resultant liquid metal
2-0 to a solid form in the absence of a refining step and a slag removal step.
~dditions from a separate or auxiliary melter may be ; added to make up for any chemical ingredient deficiencies in the melt as received from the primary melter. This invention also contemplates a tap temperature from the melting vessel of at least 2800F in order to deter "skulling" in the ~ollection vessel.
Auxiliary heating means may be provided to achieve this or greater temperatures, if necessary, to maintain such temperatures and may be in the form of supplemental burners.
:.
~ ~ ~1/ -2-~C~7~
DESCRIPTION OF PREFERRED EMBODIMENT
This invention contemplates the melting of iron bearing materials in solid form on a continuous basis, which is contra-distinct to intermittent or batch type operations. The iron bearing material is preferably in the form of selected scrap steel, i.e., steel which has been previously refined. The end product chemical speciflcations will dictate the type of scrap which will be employed, e.g., if the desired end product con-templates low sulfur and low phosphorus contents, the scrap charge should comprise material having correspondingly low sulfur and phosphorus. Contingent upon such specifications, the scrap metal selection may be made from one or from a combination of types or grades.
If it is desired to produce alloy steels from (or make allo~ additions to) carbon steel scrap charges, non-consumable additions are made directly in the melting furnace as part of the charge. Such additions may be in the form of alloy scrap containing the desired alloying elements. In order to obtain better control of the dispersion of the desired alloying element, it is preferred that alloy additions be made in the form of ferro-alloys. Some of the common alloy addition agents include molyb-denum, copper, nickel,chromium. ~ agents which are easily susceptible to oxldatlon, and thus may be termed "consumable"
a~e not usuall~ added during the melting operatlon but lnstead are added as required in the recelving vessel.
In an exemplary embodiment for pxoduclng automotive quality steel, the scrap charge may comprlse a No. l bundle* class ~f scrap, whlch one would expect to have the chemical composition *Designations of the Institute of Scrap Iron and Steel, Inc.
as shown in its yearboo~ publication "Facts", copyright 1970 ca/l~ 3 . F
.
~C3 7~
as shown in the included table.
In another exemplary embodiment for producing steel having higher permissible sulfur, phosphorus, and other residual contents, a lower quality steel scrap charge, such as No. 2 bundles* may be used. The end product steel might be used in the production of seamless pipe, electric weld pipe, plates, bars, etc.
In other embodiments, such as in the production of re~
sulfurized steels, the scrap charge may be comprised of scrap turnings. The expected chemical composition is shown in the table.
Expected maximum %, (by weight) Chemical Ingredients No. 1 No. 2 Turnings (in addition to iron-FE) Bundle Bundle __ Carbon (C) .15 .60 .60*
Sulfur (S) .03 .10 .20 Copper (Cu) .04 .70 .20 Nickel (Ni) .02 .15 .40 Chromium (C-) .02 .20 O40 Molybdenum (Mo) .01 .10 .20 Tin (Sn) ,009 .10 .025 Phosphorus (P) .010 .05 .04 Lead (Pb) nil .lO .05 * Contingentupon source, some turnings may contain as high as 2.0% C.
These compositions are to be considered general in nature and any deyiations ~rom actual scrap used do not necessarily re-strict ~heir use, as other grades of scrap are available and usable in the process.
.
. .
` ca/\~ 4-.. - , ~
70~'19 In other embodiments two or more classes of scrap may be melted, preferably each in a separate furnace, and the melts collected in a common ladle, or receiving vessel. Alloy addi-tions may be made by melting alloy scrap in a separate or auxili-ary melting furnace and adding the resultant melt to the melt of the primary grade of scrap, or by melting the alloy constitu-- ents directly with the basic charge material in the primary melt-ing vessel.
The process of the present invention contemplates the feeding of a charge which is primarily scrap metal, i.e., metal which has heen previously refined, into an oxy~fuel fired melting vessel. The high temperature ~lame is directed toward,the bottom of the feed stack and the exhausting products of combustion ascend through the stack to preheat the metal before it reaches the flame'target area. As the charge is rendered molten at the bottom of the feed stack, the feed column descends to provide a substan-tially continuous target of solid metal charge for the flame.
Preferably, the melt is immediately discharged through one or more tap holes at the bottom of the melting vessel.
2~ The preselected scrap is charged on a continuous basis, continuously melted, and immediately tapped so as not to accumu-late on the hearth of the melting vessel. Thus, there is no re-servoir of molten metal in the melting vessel, and a transition from a non-alloy heat to an alloy composition can occur immedi-ately by incorporating the desired alloy additions in the charge.
One of the advantages of the present invention is the ability to s~itch from one end product composition to another without a loss in melted materials because of the transition.
' .
- ca/k~ 5-: . ~ .. ,.
, .
In prior art continuous melting practices the metal accumulates as a bath to which alloy additions may be made. In the event of an end product composition change, there is a transition stage during which the volume of the bath is "flushed out" before the desired composition of the subsequent product composition is reached. Alternatively, if the entire bath is not flushed before - the desired subsequent composition is attained, the alloying a~ents must be added to the receiving vessel. Such practice re-quires the provision of excess temperatures and hence additional heat, or else limits the type of end product chemical compositions that can be produced, e.g., it would be difficult if not impos-sible to produce high manganese content steel. In contrast, the present invention provides a process which eliminates the txansi-tion stage. It can be established, by trial, the transit period of the feed, i.e., the time it takes for solid material, iNtro-duced at the top of the charge column in the melting vessel, to reach the tap hole or discharge port. Thus, in switching from . , ~
one product to another, one determines the start of the change in feed charge chemistry at the top o~ the feed column and as the established transit period-elapses, the melt is transferred to another collection vessel.
Xn some cases, dependent upon the charge composition and/or flame conditions, it may be necessary to supplement the carbon constituent of the charge in order to produce a liquid product having at least 0.01~ ~arbon. It is felt that such carbon level is necessary to minimize the degree of iron oxidation that might occur due to the severe oxidizing flame produced by oxy-fuel burners. The carbon level may be maintained or supplemented through ca~ 6-., . . q., . ~7iD~1~
the addition of materials which have a relatively high carbon content, e.g., pig iron, cast iron, coke, coal, etc.
It will become apparent from a reading of the foregoing disclosure that the present invention eliminates the need for the refining step of the ordinary steelmaking processes; the liquid melt may be converted to a solid form in the absence of a re-- fining step; that there is no transitory stage between melting of the charge and the formation of the desired end chemistry metal;
the chemistry change occurs in the melting vessel; and that no slag removal steps in the melting vessel are required.
C~/~L~ 7 .
~dditions from a separate or auxiliary melter may be ; added to make up for any chemical ingredient deficiencies in the melt as received from the primary melter. This invention also contemplates a tap temperature from the melting vessel of at least 2800F in order to deter "skulling" in the ~ollection vessel.
Auxiliary heating means may be provided to achieve this or greater temperatures, if necessary, to maintain such temperatures and may be in the form of supplemental burners.
:.
~ ~ ~1/ -2-~C~7~
DESCRIPTION OF PREFERRED EMBODIMENT
This invention contemplates the melting of iron bearing materials in solid form on a continuous basis, which is contra-distinct to intermittent or batch type operations. The iron bearing material is preferably in the form of selected scrap steel, i.e., steel which has been previously refined. The end product chemical speciflcations will dictate the type of scrap which will be employed, e.g., if the desired end product con-templates low sulfur and low phosphorus contents, the scrap charge should comprise material having correspondingly low sulfur and phosphorus. Contingent upon such specifications, the scrap metal selection may be made from one or from a combination of types or grades.
If it is desired to produce alloy steels from (or make allo~ additions to) carbon steel scrap charges, non-consumable additions are made directly in the melting furnace as part of the charge. Such additions may be in the form of alloy scrap containing the desired alloying elements. In order to obtain better control of the dispersion of the desired alloying element, it is preferred that alloy additions be made in the form of ferro-alloys. Some of the common alloy addition agents include molyb-denum, copper, nickel,chromium. ~ agents which are easily susceptible to oxldatlon, and thus may be termed "consumable"
a~e not usuall~ added during the melting operatlon but lnstead are added as required in the recelving vessel.
In an exemplary embodiment for pxoduclng automotive quality steel, the scrap charge may comprlse a No. l bundle* class ~f scrap, whlch one would expect to have the chemical composition *Designations of the Institute of Scrap Iron and Steel, Inc.
as shown in its yearboo~ publication "Facts", copyright 1970 ca/l~ 3 . F
.
~C3 7~
as shown in the included table.
In another exemplary embodiment for producing steel having higher permissible sulfur, phosphorus, and other residual contents, a lower quality steel scrap charge, such as No. 2 bundles* may be used. The end product steel might be used in the production of seamless pipe, electric weld pipe, plates, bars, etc.
In other embodiments, such as in the production of re~
sulfurized steels, the scrap charge may be comprised of scrap turnings. The expected chemical composition is shown in the table.
Expected maximum %, (by weight) Chemical Ingredients No. 1 No. 2 Turnings (in addition to iron-FE) Bundle Bundle __ Carbon (C) .15 .60 .60*
Sulfur (S) .03 .10 .20 Copper (Cu) .04 .70 .20 Nickel (Ni) .02 .15 .40 Chromium (C-) .02 .20 O40 Molybdenum (Mo) .01 .10 .20 Tin (Sn) ,009 .10 .025 Phosphorus (P) .010 .05 .04 Lead (Pb) nil .lO .05 * Contingentupon source, some turnings may contain as high as 2.0% C.
These compositions are to be considered general in nature and any deyiations ~rom actual scrap used do not necessarily re-strict ~heir use, as other grades of scrap are available and usable in the process.
.
. .
` ca/\~ 4-.. - , ~
70~'19 In other embodiments two or more classes of scrap may be melted, preferably each in a separate furnace, and the melts collected in a common ladle, or receiving vessel. Alloy addi-tions may be made by melting alloy scrap in a separate or auxili-ary melting furnace and adding the resultant melt to the melt of the primary grade of scrap, or by melting the alloy constitu-- ents directly with the basic charge material in the primary melt-ing vessel.
The process of the present invention contemplates the feeding of a charge which is primarily scrap metal, i.e., metal which has heen previously refined, into an oxy~fuel fired melting vessel. The high temperature ~lame is directed toward,the bottom of the feed stack and the exhausting products of combustion ascend through the stack to preheat the metal before it reaches the flame'target area. As the charge is rendered molten at the bottom of the feed stack, the feed column descends to provide a substan-tially continuous target of solid metal charge for the flame.
Preferably, the melt is immediately discharged through one or more tap holes at the bottom of the melting vessel.
2~ The preselected scrap is charged on a continuous basis, continuously melted, and immediately tapped so as not to accumu-late on the hearth of the melting vessel. Thus, there is no re-servoir of molten metal in the melting vessel, and a transition from a non-alloy heat to an alloy composition can occur immedi-ately by incorporating the desired alloy additions in the charge.
One of the advantages of the present invention is the ability to s~itch from one end product composition to another without a loss in melted materials because of the transition.
' .
- ca/k~ 5-: . ~ .. ,.
, .
In prior art continuous melting practices the metal accumulates as a bath to which alloy additions may be made. In the event of an end product composition change, there is a transition stage during which the volume of the bath is "flushed out" before the desired composition of the subsequent product composition is reached. Alternatively, if the entire bath is not flushed before - the desired subsequent composition is attained, the alloying a~ents must be added to the receiving vessel. Such practice re-quires the provision of excess temperatures and hence additional heat, or else limits the type of end product chemical compositions that can be produced, e.g., it would be difficult if not impos-sible to produce high manganese content steel. In contrast, the present invention provides a process which eliminates the txansi-tion stage. It can be established, by trial, the transit period of the feed, i.e., the time it takes for solid material, iNtro-duced at the top of the charge column in the melting vessel, to reach the tap hole or discharge port. Thus, in switching from . , ~
one product to another, one determines the start of the change in feed charge chemistry at the top o~ the feed column and as the established transit period-elapses, the melt is transferred to another collection vessel.
Xn some cases, dependent upon the charge composition and/or flame conditions, it may be necessary to supplement the carbon constituent of the charge in order to produce a liquid product having at least 0.01~ ~arbon. It is felt that such carbon level is necessary to minimize the degree of iron oxidation that might occur due to the severe oxidizing flame produced by oxy-fuel burners. The carbon level may be maintained or supplemented through ca~ 6-., . . q., . ~7iD~1~
the addition of materials which have a relatively high carbon content, e.g., pig iron, cast iron, coke, coal, etc.
It will become apparent from a reading of the foregoing disclosure that the present invention eliminates the need for the refining step of the ordinary steelmaking processes; the liquid melt may be converted to a solid form in the absence of a re-- fining step; that there is no transitory stage between melting of the charge and the formation of the desired end chemistry metal;
the chemistry change occurs in the melting vessel; and that no slag removal steps in the melting vessel are required.
C~/~L~ 7 .
Claims (8)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A continuous process for producing steel, which comprises:
providing in an oxy-fuel fired melting vessel a charge of solid steel of preselected composition containing the principal elements and in proportions corresponding substantially to those of the desired steel end product, and melting said charge and converting the resultant liquid metal to a solid form in the absence of a refining step and a slag removal step.
providing in an oxy-fuel fired melting vessel a charge of solid steel of preselected composition containing the principal elements and in proportions corresponding substantially to those of the desired steel end product, and melting said charge and converting the resultant liquid metal to a solid form in the absence of a refining step and a slag removal step.
2. The process as described in Claim 1, wherein the composition of the charge of solid steel is deficient in some aspects as compared to the desired end composition, and which further comprises:
adding an agent to the melting vessel to compensate for any deficiency.
adding an agent to the melting vessel to compensate for any deficiency.
3. The process as described in Claim 2 wherein said agents are in the form of non-consumable alloying elements.
4. The process as described in Claim 1 wherein the pre-dominant portion of said charge is in the form of No. 1 bundles of steel scrap.
5. The process as described in Claim 1, wherein the predominant portion of said charge is in the form of No. 2 bundles of steel scrap.
6. The process as described in Claim 1, wherein the molten charge is tapped at a temperature of at least 2800°F.
7. The process as described in Claim 1, wherein said melting vessel is fed with a charge which is primarily scrap metal containing iron, a portion of said charge is continuously rendered molten and immediately discharged from the melting vessel to a receiving vessel, and the charge in the melting vessel is con-tinously replenished as the molten portion is being discharged.
8. The process as described in Claim 6 or 7, wherein a change is made from one desired end product composition to another without interruption in the melting procedure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA239,336A CA1070119A (en) | 1975-11-10 | 1975-11-10 | Steelmaking process |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA239,336A CA1070119A (en) | 1975-11-10 | 1975-11-10 | Steelmaking process |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070119A true CA1070119A (en) | 1980-01-22 |
Family
ID=4104483
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA239,336A Expired CA1070119A (en) | 1975-11-10 | 1975-11-10 | Steelmaking process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1070119A (en) |
-
1975
- 1975-11-10 CA CA239,336A patent/CA1070119A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |