GB2148941A - Improvements in and relating to steel castings - Google Patents
Improvements in and relating to steel castings Download PDFInfo
- Publication number
- GB2148941A GB2148941A GB08423493A GB8423493A GB2148941A GB 2148941 A GB2148941 A GB 2148941A GB 08423493 A GB08423493 A GB 08423493A GB 8423493 A GB8423493 A GB 8423493A GB 2148941 A GB2148941 A GB 2148941A
- Authority
- GB
- United Kingdom
- Prior art keywords
- casting
- steel
- titanium
- furnace
- nitrided
- 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.)
- Granted
Links
- 238000005266 casting Methods 0.000 title claims abstract description 37
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 27
- 239000010959 steel Substances 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 13
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 8
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052751 metal Inorganic materials 0.000 claims abstract description 8
- 239000002184 metal Substances 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- 239000010936 titanium Substances 0.000 claims abstract description 8
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 8
- 239000011261 inert gas Substances 0.000 claims abstract description 6
- 239000006185 dispersion Substances 0.000 claims abstract description 5
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000004411 aluminium Substances 0.000 claims abstract description 4
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 4
- 238000001816 cooling Methods 0.000 claims abstract description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 4
- 239000011733 molybdenum Substances 0.000 claims abstract description 4
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 4
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen(.) Chemical compound [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 claims abstract description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 3
- 238000005422 blasting Methods 0.000 claims description 3
- 238000004845 hydriding Methods 0.000 claims description 3
- 238000005121 nitriding Methods 0.000 claims description 3
- 239000007789 gas Substances 0.000 claims description 2
- 230000000717 retained effect Effects 0.000 claims description 2
- NRTOMJZYCJJWKI-UHFFFAOYSA-N Titanium nitride Chemical compound [Ti]#N NRTOMJZYCJJWKI-UHFFFAOYSA-N 0.000 abstract description 4
- 239000000463 material Substances 0.000 description 5
- 229910001200 Ferrotitanium Inorganic materials 0.000 description 4
- 229910000684 Cobalt-chrome Inorganic materials 0.000 description 3
- 239000010952 cobalt-chrome Substances 0.000 description 3
- 229910001208 Crucible steel Inorganic materials 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 238000003780 insertion Methods 0.000 description 2
- 230000037431 insertion Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910000619 316 stainless steel Inorganic materials 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 238000010297 mechanical methods and process Methods 0.000 description 1
- 230000005226 mechanical processes and functions Effects 0.000 description 1
- 238000005058 metal casting Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000009972 noncorrosive effect Effects 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/10—Alloys containing non-metals
- C22C1/1036—Alloys containing non-metals starting from a melt
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
Abstract
A titanium nitride steel particularly suitable for use as a partial denture mounting is formed by casting steel stock and then producing a dispersion of nitrided or hydrided titanium. For this process the steel stock with the titanium dispersed therein is melted in a furnace in an atmosphere of an inert gas and the molten metal is introduced into a mould to form a casting having portions of thin section. The casting is removed from the mould after cooling, and the titanium is then nitrided or hydrided by passing nitrogen or hydrogen gas over the casting at high temperature within a furnace. Other reactive elements namely molybdenum, aluminium or zirconium may be used instead of the titanium. The nitrided titanium thin section portions of the steel present a high elastic limit and good toughness which is particularly suitable for parts of a denture mounting which may be subjected to regular flexing.
Description
SPECIFICATION
Improvements in and relating to steel castings
This invention relates to the manufacture of a steel to give a high elastic limit and an extensive plastic strain to high values of ultimate tensile strength so that the steel will be suitable especially for use in the formation of partial dentures.
If a partial denture is to be made from metal then the metal must be non-corrosive and should have an adequate rigidity factor.
Gold is used for partial dentures but this is an expensive material and has other drawbacks.
More recently cobalt chrome has been used but has the disadvantage that thin portions which form clasps which have to be sprung out to fit over existing teeth are very brittle and hence liable to fracture immediately on insertion or after a period of use. Conventional 316 stainless steel has been used but this is too soft and ductile with the result that parts forming clasps to fit over existing teeth tend to stay apart when prised open so that the denture becomes loose in the mouth.
It is an object of this invention to provide a metal casting which is suitable for prolonged use as a partial denture.
Accordingly this invention provides a method of forming a casting of a steel incorporating a dispersion of a nitrided or hydrided reactive element chosen from titanium, molybdenum, aluminium or zirconium wherein steel stock with the reactive element dispersed therein is melted in a furnace in an atmosphere of an inert gas and the molten metal is introduced into a mould to form portions of thin section, the casting is removed from the mould after cooling, and the reactive element is nitrided or hydrided by passing nitrogen or hydrogen gas over the casting at high temperature within a furnace.
The improvement in properties achieved in the steels of this invention are of value in the application of the alloy to partial dentures but the complexity of shape of these structures preclude their manufacture by straightfoward mechanical processes. Furthermore there are problems in casting this material as it is very prone to oxidation during the casting process.
The casting formed by the invention has portions of sufficiently thin section (which will form the clasps) that subsequent high-temperature nitridation or hydridation can be effected. Naturally it is essential that the casting technique retains sufficient of the reactive element in solid solution within the steel to produce a worthwhile improvement in strength during the subsequent heat treatment. The reactive elements employed react rapidly with components of air (oxygen, nitrogen, carbon) at casting temperatures but this process can be limited by blanketing the melted steel and casting in an inert atmosphere. This procedure allows retention of the reactive element in solid solution within the cast steel and permits the development of a reactive element nitride or hydride dispersion during subsequent nitridation or hydridation.
It is this dispersion which contributes mainly to the overall characteristics of the steel which make it suitable for use as a partial denture.
Whilst other gases may be used a preferred inert gas is argon. The inert gas is ideally sprayed onto the surface of the reactive element steel within a crucible in the furnace.
It is expected that a certain amount of oxidation will occur on the surface of the cast steel but thin coatings can readily be removed or substantially reduced by cleaning the surface before the nitriding or hydriding step.
This cleaning could be effected by shot blasting or some other abrasive cleaning operation.
After the reactive element within the steel has been nitrided it is preferred that the casting should be retained in the furnace at a high temperature in a hydrogen atmosphere so as to ensure that extraneous nitrogen which has not reacted with the material is removed.
The invention also extends to a steel casting with portions of thin section as formed by the method of this invention as herein before defined. This casting may be in the form of a partial denture mounting.
The invention may be performed in various ways and a preferred embodiment thereof will now be described in the following example and with reference to the accompanying drawing which illustrates a plan view of a partial dentue constructed from a titanium nitride steel in accordance with the invention.
EXAMPLE.
A titanium steel comprising 25% nickel, 20% chromium, 3% titanium and 52% iron (or other suitable titanium-steel stock of different base composition) in block form is heated in a crucible in a furnace to its molten state.
During heating argon is sprayed onto the surface of the metal within the crucible. When the metal is in the molten state it is centrifuged into an investment and is then allowed to cool. The casting is then broken out from the mould and will be in the form of a partial denture mounting 1 as shown in the drawing.
The mounting will incorporate a number of clasps 2, 3 4 defined by thin metallic strips or arms.
The casting is then subjected to cleaning by shot blasting to remove any coating of titanium oxide or other impurity which has formed on the surface of the casting. The cleaned casting is then placed in a furnace within a silica tube and an atmosphere of dry clean nitrogen and hydrogen (in the ratio of 95% nitrogen to 5% of hydrogen) is passed continuously over the surface of the casing for about four to six hours at a temperature of 11 50 C.
Hydrogen gas is then passed over the casting for a further two to three hours at the same temperature to effect removal of extraneous nitrogen which has not reacted with the metal.
After cooling the nitrided titanium steel casting is removed from the furnace and synthetic teeth and gum material is moulded onto the casting. As shown in the drawing the casting has three teeth 5 moulded thereon together with a portion of material 6 imitating a portion of gum.
The nitrided titanium steel presents a high elastic limit and good toughness. Furthermore the thinner parts of the casting forming the clasp portions 2, 3, 4 are nitrided to the greatest extent thus ensuring that these parts are particularly strong. The casting therefore provides a very secure partial denture whose clasps 2, 3, 4 tend to retain their shape so that the denture is held securely within the mouth during the necessary repeated removals and insertions. Not only is a partial dentures constructed from titanium nitride steel more effective in use than one made from cobalt chrome but it can be manufactured at a cost which is likely to be about half that of a cobalt chrome partial denture.
Similar advantages to those achieved with a titanium nitride steel are likely for a steel incorporating other non-toxic reactive elements such as molybdenum, aluminium and zirconium. Furthermore the reactive element could be hydrided rather than nitrided if desired.
Claims (10)
1. A method of forming a casting of a steel incorporating a dispersion of a nitrided or hydrided reactive element chosen from titanium, molybdenum, aluminium or zirconium wherein steel stock with the reactive element dispersed therein is melted in a furnace in an atmosphere of an inert gas and the molten metal is introduced into a mould to form portions of thin section, the casting is removed from the mould after cooling, and the reactive element is nitrided or hydrided by passing nitrogen or hydrogen gas over the casting at high temperature within a furnace.
2. A method according to claim 1, wherein the insert gas is argon.
3. A method according to claim 1 or claim 2, wherein the inert gas is sprayed onto the surface of the reactive element steel within a crucible in the furnace.
4. A method according to any one of claims 1 to 3, wherein the surface of the cooled casting is cleaned before the nitriding or hydriding step.
5. A method according to claim 4, wherein cleaning is effected by shot blasting or some other abrasive cleaning operation.
6. A method according to any one of claims 1 to 5, wherein the casting is retained in the furnace at a high temperature in a hydrogen atmosphere for some hours are the nitriding or hydriding step.
7. A method of forming a steel casting with portions of thin section substantially as described herein.
8. A steel casting formed by a method as claimed in any one of claims 1 to 7.
9. A casting as claimed in claim 8 in the form of a partial denture mounting.
10. A partial denture mounting formed as a casting in steel as claimed in claim 9 and substantially as herein described.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB838324745A GB8324745D0 (en) | 1983-09-15 | 1983-09-15 | Steel castings |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8423493D0 GB8423493D0 (en) | 1984-10-24 |
| GB2148941A true GB2148941A (en) | 1985-06-05 |
| GB2148941B GB2148941B (en) | 1986-12-10 |
Family
ID=10548843
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838324745A Pending GB8324745D0 (en) | 1983-09-15 | 1983-09-15 | Steel castings |
| GB08423493A Expired GB2148941B (en) | 1983-09-15 | 1984-09-17 | Improvements in and relating to steel castings |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB838324745A Pending GB8324745D0 (en) | 1983-09-15 | 1983-09-15 | Steel castings |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8324745D0 (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB359423A (en) * | 1930-06-10 | 1931-10-12 | Sheepbridge Stokes Centrifugal | Improvements in the production of alloy steel castings |
| GB398834A (en) * | 1931-03-14 | 1933-09-14 | Commentry Fourchambault Et Dec | Improvements in and relating to the nitrogenisation of ferrous austenitic alloys |
| GB851346A (en) * | 1958-07-22 | 1960-10-12 | Bofors Ab | Process of nitriding hardenable steel |
| GB1250934A (en) * | 1968-06-07 | 1971-10-27 | ||
| GB1464217A (en) * | 1974-06-12 | 1977-02-09 | Allegheny Ludlum Ind Inc | Process for producing austenitic ferrous alloys |
| EP0008228A2 (en) * | 1978-08-14 | 1980-02-20 | The Garrett Corporation | Internally nitrided ferritic stainless steels, and methods of producing such steels |
| GB1562903A (en) * | 1975-07-30 | 1980-03-19 | Uss Eng & Consult | Nitride reaction strenghtening of low carbon ferrous metal stock |
-
1983
- 1983-09-15 GB GB838324745A patent/GB8324745D0/en active Pending
-
1984
- 1984-09-17 GB GB08423493A patent/GB2148941B/en not_active Expired
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB359423A (en) * | 1930-06-10 | 1931-10-12 | Sheepbridge Stokes Centrifugal | Improvements in the production of alloy steel castings |
| GB398834A (en) * | 1931-03-14 | 1933-09-14 | Commentry Fourchambault Et Dec | Improvements in and relating to the nitrogenisation of ferrous austenitic alloys |
| GB851346A (en) * | 1958-07-22 | 1960-10-12 | Bofors Ab | Process of nitriding hardenable steel |
| GB1250934A (en) * | 1968-06-07 | 1971-10-27 | ||
| GB1464217A (en) * | 1974-06-12 | 1977-02-09 | Allegheny Ludlum Ind Inc | Process for producing austenitic ferrous alloys |
| GB1562903A (en) * | 1975-07-30 | 1980-03-19 | Uss Eng & Consult | Nitride reaction strenghtening of low carbon ferrous metal stock |
| EP0008228A2 (en) * | 1978-08-14 | 1980-02-20 | The Garrett Corporation | Internally nitrided ferritic stainless steels, and methods of producing such steels |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8324745D0 (en) | 1983-10-19 |
| GB2148941B (en) | 1986-12-10 |
| GB8423493D0 (en) | 1984-10-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 746 | Register noted 'licences of right' (sect. 46/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930917 |