US2492803A - Carburizing steel articles - Google Patents
Carburizing steel articles Download PDFInfo
- Publication number
- US2492803A US2492803A US656765A US65676546A US2492803A US 2492803 A US2492803 A US 2492803A US 656765 A US656765 A US 656765A US 65676546 A US65676546 A US 65676546A US 2492803 A US2492803 A US 2492803A
- Authority
- US
- United States
- Prior art keywords
- bath
- carbon
- carburizing
- steel articles
- weight
- 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 - Lifetime
Links
- 229910000831 Steel Inorganic materials 0.000 title description 16
- 239000010959 steel Substances 0.000 title description 16
- 238000005255 carburizing Methods 0.000 title description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 21
- 229910052799 carbon Inorganic materials 0.000 description 18
- JKWMSGQKBLHBQQ-UHFFFAOYSA-N diboron trioxide Chemical group O=BOB=O JKWMSGQKBLHBQQ-UHFFFAOYSA-N 0.000 description 9
- 238000000034 method Methods 0.000 description 8
- 229910052810 boron oxide Inorganic materials 0.000 description 7
- 150000003839 salts Chemical class 0.000 description 7
- 150000002927 oxygen compounds Chemical class 0.000 description 6
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- 229910000288 alkali metal carbonate Inorganic materials 0.000 description 4
- 150000008041 alkali metal carbonates Chemical class 0.000 description 4
- 239000004615 ingredient Substances 0.000 description 4
- 238000005121 nitriding Methods 0.000 description 4
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 3
- 230000003213 activating effect Effects 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 229910001514 alkali metal chloride Inorganic materials 0.000 description 2
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 2
- 239000004327 boric acid Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000001103 potassium chloride Substances 0.000 description 2
- 235000011164 potassium chloride Nutrition 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical class [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 description 1
- 229910052910 alkali metal silicate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910021538 borax Inorganic materials 0.000 description 1
- 150000001639 boron compounds Chemical class 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- UQGFMSUEHSUPRD-UHFFFAOYSA-N disodium;3,7-dioxido-2,4,6,8,9-pentaoxa-1,3,5,7-tetraborabicyclo[3.3.1]nonane Chemical compound [Na+].[Na+].O1B([O-])OB2OB([O-])OB1O2 UQGFMSUEHSUPRD-UHFFFAOYSA-N 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910017464 nitrogen compound Inorganic materials 0.000 description 1
- 150000002830 nitrogen compounds Chemical class 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 239000004328 sodium tetraborate Substances 0.000 description 1
- 235000010339 sodium tetraborate Nutrition 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
- C23C8/42—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions only one element being applied
- C23C8/44—Carburising
- C23C8/46—Carburising of ferrous surfaces
Definitions
- This invention relates to carburizing steel articles and more particularly to treating steel articlesin a molten salt-bath so as-to form-a carburized case, thereon,
- An object of the present invention is to provide an improved carburizing process utilizing a molten salt bath free from nitrogenous carburizing ingredients. Another object is an improved carburizing bath and process utilizing carbon as the carburizing ingredient and operable at conventional bath carburizing temperatures. Another object is to increase the carburizing activity of carbon in a molten salt bath. Still other objects will be apparent from the ensuing description of the invention.
- the aforesaid objects are attained in accordance with the present invention by treating steel articles to be carburized in a molten salt bath containing one or more alkali metal carbonates, at least 2% by weight of finely divided carbon dispersed in the bath and from 1 to about by weight of an oxygen compound of boron or silicon which is soluble in the bath, at a temperature of about 1500 to 1800 F.
- the preferred addition agent is boron oxide (B203).
- boron oxide B203
- other oxygen compounds of boron and silicon which are more acidic than sodium carbonate, may be employed as the activating agent.
- Sodium tetraborate, boric acid, silica and alkali metal silicates are typical examples.
- the quantity of the activating agent required will vary depending upon the conditions employed, but generally will lie-in the range of 1% and.2 %,.by weight.
- the amount, of-carbonatepresent. is not critical, as long as an excess of .at,least about:5% above that required tQ-reactwiththe.addedboron oxide or other activating; a gent, iswmaintained, i. e., about 5% in excess-over ⁇ one :molar equivalent.
- the amount of carbon dispersed inv thebatn will depend on the nature. of thecarbon employed, its-state of subdiyision, ,andthebathcomposition. Generally, the. bath. should contain about 2 to 15% by weight of dispersed carbon. It is preferable to employ an amount of carbon in excess of that which can be dispersed, by adding suflicient to form a floating layer of carbon on the surface of the bath.
- the various known kinds of carbon can be used, c. g., graphite, charcoal, activated carbon and the like.
- the steel articles to be carburized are treated by immersion in the bath for a time dependent on the desired depth of case, e. g., for from 10 minutes to 48 hours.
- Example A 50% sodium carbonate-50% potassium chloride bath containing excess carbon was operated at 1600 F.
- An SAE X1020 steel bar treated therein for 1 hour showed surface decarburization (loss of carbon) to a depth of about 0.014".
- Five per cent of the bath weight of boric acid anhydride (B203) was added and a second SAE X1020 steel bar was treated in the bath for 1 hour. With this short time a nitrogen-free carburized case 0012-0016 in depth was obtained.
- B203 boric acid anhydride
- the process which comprises immersing steel articles in a molten salt bath consisting of at least one alkali metal chloride, together with about 2 to 15% by weight of finely divided carbon dispersed in the bath, from 1 to 20% by weight of an oxygen compound more acidic than alkali metal carbonate selected from the group consisting of the oxygen-containing compounds of boron and silicon which are soluble in said bath and an amount of alkali metal carbonate not less than about 5% more than one molar equivalent of said oxygen compound, at a temperature of 1500 to 1800 F.
- the process which comprises immersing steel articles in a molten salt bath consisting of a mixture of alkali metal carbonate and alkali metal chloride containing about 2 to 15% by weight of finely divided carbon dispersed in the bath and 1 to 20% by weight of boron oxide, the amount of said carbonate being not less than 5% more than one molar equivalent of the boron oxide present and not more than about of the combined weights of said carbonate and said chloride.
Description
Patented Dec. 27, 1949 CARBURIZING STEEL ARTICLES.
'Banl-;M.. Leininger, Grand Island, N. Y.,;assjgno r to E. I. du Pont de Nemours & Cmpany,.Wil- ,mington, :Del., ,a. corporation of Delaware No Drawing. Application March-23,1946,
Serial No. 656,765
Claims. 1 This invention relates to carburizing steel articles and more particularly to treating steel articlesin a molten salt-bath so as-to form-a carburized case, thereon,
In e har nin pe ations-mol en. sal ba containing cyanide have been utilized to car.- burize steel articles, "but such baths invariably introduce notv only carbon into the steel, butalso more or less nitrogen. For some purposes, the introduction of nitrogen is objectionable and many attempts have been made to develop oommercially suitable molten salt baths which will carburize with little or no nitriding. The most successful of such baths contain cyanide or other carbon-nitrogen compounds plus other ingredients which accelerate carburizing or repress nitriding, but such baths are never entirely devoid of nitriding action.
Attempts also have been made to develop carburizing baths which contain no nitrogen compounds, so that nitriding is completely prevented. For this purpose, because of its relative cheapness, uncombined carbon is the preferred carburizing ingredient and several proposals for carbon-containing carburizing baths have been made. However, such baths usually have required undesirably high operating temperatures or have had undesirably low carburizing activity.
An object of the present invention is to provide an improved carburizing process utilizing a molten salt bath free from nitrogenous carburizing ingredients. Another object is an improved carburizing bath and process utilizing carbon as the carburizing ingredient and operable at conventional bath carburizing temperatures. Another object is to increase the carburizing activity of carbon in a molten salt bath. Still other objects will be apparent from the ensuing description of the invention.
The aforesaid objects are attained in accordance with the present invention by treating steel articles to be carburized in a molten salt bath containing one or more alkali metal carbonates, at least 2% by weight of finely divided carbon dispersed in the bath and from 1 to about by weight of an oxygen compound of boron or silicon which is soluble in the bath, at a temperature of about 1500 to 1800 F. The preferred addition agent is boron oxide (B203).
In place of boron oxide (B203), other oxygen compounds of boron and silicon which are more acidic than sodium carbonate, may be employed as the activating agent. Sodium tetraborate, boric acid, silica and alkali metal silicates are typical examples. The quantity of the activating agent required will vary depending upon the conditions employed, but generally will lie-in the range of 1% and.2 %,.by weight.
The amount, of-carbonatepresent.is not critical, as long as an excess of .at,least about:5% above that required tQ-reactwiththe.addedboron oxide or other activating; a gent, iswmaintained, i. e., about 5% in excess-over {one :molar equivalent.
The amount of carbon dispersed inv thebatn will depend on the nature. of thecarbon employed, its-state of subdiyision, ,andthebathcomposition. Generally, the. bath. should contain about 2 to 15% by weight of dispersed carbon. It is preferable to employ an amount of carbon in excess of that which can be dispersed, by adding suflicient to form a floating layer of carbon on the surface of the bath. The various known kinds of carbon can be used, c. g., graphite, charcoal, activated carbon and the like.
The steel articles to be carburized are treated by immersion in the bath for a time dependent on the desired depth of case, e. g., for from 10 minutes to 48 hours.
Since the carburizing action falls off gradually following the addition of the boric acid, it will be necessary in those cases where continuous operation is desirable to replenish the bath periodically with fresh carbonate and boron oxide or its equivalent, while maintaining a sufficient excess of carbon in the melt.
Following is a specific example of the process:
Example A 50% sodium carbonate-50% potassium chloride bath containing excess carbon was operated at 1600 F. An SAE X1020 steel bar treated therein for 1 hour showed surface decarburization (loss of carbon) to a depth of about 0.014". Five per cent of the bath weight of boric acid anhydride (B203) was added and a second SAE X1020 steel bar was treated in the bath for 1 hour. With this short time a nitrogen-free carburized case 0012-0016 in depth was obtained. Following are the analyses of gradient cuts removed from the surface of the steel test bars employed. Each cut was 0.004" on radius.
Per Cent 0 Per Cent 0 Out No. Before Add- After Add- 0. 08 0. 42 0. l6 0. 36 0. l8 0. 28 0. 20 O. 24 1 0. 22 0. 22
3 The specifications of SAE X1020 steel are:
0.15-0.25% carbon 0.70-1.00% manganese 0.045% phosphorus maximum 0.055% sulfur maximum I claim:
1. The process which comprises immersing steel articles in a molten salt bath consisting of at least one alkali metal chloride, together with about 2 to 15% by weight of finely divided carbon dispersed in the bath, from 1 to 20% by weight of an oxygen compound more acidic than alkali metal carbonate selected from the group consisting of the oxygen-containing compounds of boron and silicon which are soluble in said bath and an amount of alkali metal carbonate not less than about 5% more than one molar equivalent of said oxygen compound, at a temperature of 1500 to 1800 F.
2. The process of claim 1 in which said oxygen compound is a boron compound.
3. The process of claim 1 in which said oxygen compound is boron oxide.
4. The process which comprises immersing steel articles in a molten salt bath consisting of approximately equal parts by weight of sodium carbonate and potassium chloride, together with about 2 to of finely divided carbon dispersed in the bath and 1 to by weight of boron oxide, at a temperature of 1500 to 1800 F.
5. The process which comprises immersing steel articles in a molten salt bath consisting of a mixture of alkali metal carbonate and alkali metal chloride containing about 2 to 15% by weight of finely divided carbon dispersed in the bath and 1 to 20% by weight of boron oxide, the amount of said carbonate being not less than 5% more than one molar equivalent of the boron oxide present and not more than about of the combined weights of said carbonate and said chloride.
PAUL M. LEININGER.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,796,248 Freudenberg Mar. 10, 1931 2,063,079 Beck Dec. 8, 1936 2,095,188 Hanusch Oct. 5, 1937 2,364,292 Holt Dec. 5, 1944 OTHER REFERENCES Steel and its Heat Treatment, Bullens, vol. 1, 4th edition, 1938, John Wiley & Sons Inc., N. Y., page 344.
The Iron Age," November 10, 1932, page 16, and December 8, 1932, page 882.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US656765A US2492803A (en) | 1946-03-23 | 1946-03-23 | Carburizing steel articles |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US656765A US2492803A (en) | 1946-03-23 | 1946-03-23 | Carburizing steel articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2492803A true US2492803A (en) | 1949-12-27 |
Family
ID=24634456
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US656765A Expired - Lifetime US2492803A (en) | 1946-03-23 | 1946-03-23 | Carburizing steel articles |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2492803A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0147011A2 (en) * | 1983-12-28 | 1985-07-03 | Heatbath Corporation | A non-cyanide salt bath and process for carburization of ferrous metals and alloys |
| US4533403A (en) * | 1983-10-31 | 1985-08-06 | Dresser Industries, Inc. | Pack composition for borocarburizing ferrous substrates |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1796248A (en) * | 1929-01-12 | 1931-03-10 | Roessler & Hasslacher Chemical | Process for the cementation of iron and steel |
| US2063079A (en) * | 1932-08-13 | 1936-12-08 | Beck Walter | Process for maintaining or regulating the efficacy of cyanide melts |
| US2095188A (en) * | 1934-03-12 | 1937-10-05 | Houghton Fabrik G M B H Deutsc | Iron and steel cementing bath composition |
| US2364292A (en) * | 1943-10-18 | 1944-12-05 | Du Pont | Casehardening |
-
1946
- 1946-03-23 US US656765A patent/US2492803A/en not_active Expired - Lifetime
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1796248A (en) * | 1929-01-12 | 1931-03-10 | Roessler & Hasslacher Chemical | Process for the cementation of iron and steel |
| US2063079A (en) * | 1932-08-13 | 1936-12-08 | Beck Walter | Process for maintaining or regulating the efficacy of cyanide melts |
| US2095188A (en) * | 1934-03-12 | 1937-10-05 | Houghton Fabrik G M B H Deutsc | Iron and steel cementing bath composition |
| US2364292A (en) * | 1943-10-18 | 1944-12-05 | Du Pont | Casehardening |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4533403A (en) * | 1983-10-31 | 1985-08-06 | Dresser Industries, Inc. | Pack composition for borocarburizing ferrous substrates |
| EP0147011A2 (en) * | 1983-12-28 | 1985-07-03 | Heatbath Corporation | A non-cyanide salt bath and process for carburization of ferrous metals and alloys |
| EP0147011A3 (en) * | 1983-12-28 | 1986-03-26 | Heatbath Corporation | A non-cyanide salt bath and process for carburization of ferrous metals and alloys |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| GB1034270A (en) | Case-hardening processes | |
| US3870572A (en) | Process for nitriding unalloyed or low-alloy steel | |
| ES437450A1 (en) | Method of maintaining at very low values the content of cyanide in salt baths containing cyanates | |
| US2492803A (en) | Carburizing steel articles | |
| US2339223A (en) | Method of case hardening | |
| US2231009A (en) | Heat treating process | |
| US2248732A (en) | Process for the hardening of steel | |
| US1804454A (en) | Process for hardening articles made of iron or steel | |
| US2231010A (en) | Heat treating process | |
| SE7602838L (en) | SALT BATH FOR BIG COOLING OF BATH-NITRATED CONSTRUCTION ELEMENTS | |
| US2042527A (en) | Process for nitriding | |
| US2492804A (en) | Casehardening steel | |
| US1993204A (en) | Method of case hardening articles | |
| US2254296A (en) | Casehardening salt bath | |
| US3117038A (en) | Fused salt baths-composition and method for carburising | |
| US1736921A (en) | Case nitrification of steel | |
| US1996269A (en) | Method of case-hardening iron articles | |
| US2492805A (en) | Casehardening composition | |
| US1736920A (en) | Case hardening | |
| US2264431A (en) | Hardening of steel articles | |
| US1235901A (en) | Cementation process. | |
| US2016321A (en) | Heating bath for hardening of steel, especially tool steel | |
| US1808355A (en) | Method of nitrification | |
| US1962091A (en) | Case hardening | |
| US1374038A (en) | Process for producing zirconium steel |