US1840562A - Method of heat-treating aluminum and articles thereby - Google Patents
Method of heat-treating aluminum and articles thereby Download PDFInfo
- Publication number
- US1840562A US1840562A US517317A US51731731A US1840562A US 1840562 A US1840562 A US 1840562A US 517317 A US517317 A US 517317A US 51731731 A US51731731 A US 51731731A US 1840562 A US1840562 A US 1840562A
- Authority
- US
- United States
- Prior art keywords
- heat
- aluminum
- corrosion
- treating
- nitrate
- 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
- 229910052782 aluminium Inorganic materials 0.000 title description 25
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title description 25
- 238000000034 method Methods 0.000 title description 12
- 235000010210 aluminium Nutrition 0.000 description 24
- 230000007797 corrosion Effects 0.000 description 20
- 238000005260 corrosion Methods 0.000 description 20
- 150000003839 salts Chemical class 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 13
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 12
- 229910002651 NO3 Inorganic materials 0.000 description 11
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 11
- 229910052751 metal Inorganic materials 0.000 description 10
- 239000002184 metal Substances 0.000 description 10
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 10
- 238000007792 addition Methods 0.000 description 7
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 6
- 229910052804 chromium Inorganic materials 0.000 description 6
- 239000011651 chromium Substances 0.000 description 6
- 150000002927 oxygen compounds Chemical class 0.000 description 5
- 235000010344 sodium nitrate Nutrition 0.000 description 5
- 239000004317 sodium nitrate Substances 0.000 description 5
- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 4
- 229910001963 alkali metal nitrate Inorganic materials 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 239000002585 base Substances 0.000 description 3
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Chemical class O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 3
- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 3
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 3
- 230000002401 inhibitory effect Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000010791 quenching Methods 0.000 description 3
- 230000000171 quenching effect Effects 0.000 description 3
- 238000010186 staining Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 230000001464 adherent effect Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical class [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 2
- CMMUKUYEPRGBFB-UHFFFAOYSA-L dichromic acid Chemical compound O[Cr](=O)(=O)O[Cr](O)(=O)=O CMMUKUYEPRGBFB-UHFFFAOYSA-L 0.000 description 2
- 230000004927 fusion Effects 0.000 description 2
- 235000010333 potassium nitrate Nutrition 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 208000031261 Acute myeloid leukaemia Diseases 0.000 description 1
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 208000033776 Myeloid Acute Leukemia Diseases 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- ICIWUVCWSCSTAQ-UHFFFAOYSA-N iodic acid Chemical class OI(=O)=O ICIWUVCWSCSTAQ-UHFFFAOYSA-N 0.000 description 1
- 229910001960 metal nitrate Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 239000004323 potassium nitrate Substances 0.000 description 1
- 239000011833 salt mixture Substances 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
Definitions
- mun w. names, or rnnnroar, rmmvuu, Assmuon r summon coll- PAIN'Y'.
- the invention relates to the heat treatment of aluminum and aluminum base alloys in fused salt baths, and to aluminum and aluminum base articles resulting therefrom, both as aluminum and-such alloys being hereinafter designated as aluminum.
- a serious disadvantage of heat treating aluminum-in fused salt baths is the corrosion which may take place on the surface of the metal during or after quenching in water.
- the .fused salt used is an alkali metal nitrate, such as SOdlllIIl nitrate, which is commonly used for such purposes.
- alkali metal nitrate such as SOdlllIIl nitrate
- twin, and alkali metal nitrates regardless of initial alkalinity, become more alkaline when held ina state of fusion.
- An object of this invention is to provide a method of heat treating aluminum in a fused salt bath, which method obviates the foregoing dilficulties, and which not only substantially eliminates corrosive staining of the sheet or article being treated, but also forms a surface on it which is resistant to corrosion in the use of the article,
- Another object is to provide aluminum articles free, or substantially so, from heattreating corrosion stains, and having surfaces which are resistant to corrosion.
- the invention ispredicated upon my discovery that by heat treating aluminum in a fused salt bath containing an oxygen compound of chromium the surface of the alumi num is not merely free, or substantially free, from corrosive staining, but is rendered resistant to subsequent corrosion.
- the oxygen compound of chromium may be added'as a chromic or dichromic acid, or as a salt or salts thereof, either singly or in combination, and
- Thefused salt bath now in general use for heat treating aluminum consists of alkah metal nitrates, such as sodium nitrate, potassium nitrate, or a mixture of the two, but I prefer to use sodium nitrate chiefly because. of the commercial consideration of cost.
- the effects of the addition of an oxygen compound of chromium are to inhibit corrosion throughout the heat treating cycle, including the quenching step, and to render the surfaces of the heat treated articles resistant to corrosion.
- a chromic acid salt when added to a fusedznitrate bath it serves the dual function of neutralizing the bath'and inhibiting the tendency of the nitrate to become alkaline when held in a state of fusion. It is not necessary that, prior to making the addi tion, the bath be completely neutralized, because the addition of small amounts has been found to exert some inhibitive action upon corrosion even before the bath has been completely neutralized, but I prefer to use an able to add a mixture of chromates and dichromates, with or ithout the addition of chromic or dichromic acid, in all cases corrosion of the surface of the metal is efi'ectively prevented. If a chromate be added, it is usually necessary to use a much greater quantity in order to secure the desired inhibiting effect than where a dichromate is used, although this depends on the grade of nitrate which is used for the bath.
- chromic acid salt required to neutralize the alkalinity of the nitrate and inhibit subsequent corrosion of the metal treated therein may be determined by titrating the fused salt according to well known analytical procedure.
- this procedure to determine the proper quantity of npotassium dichromate to be added to a ta containing 30,000 pounds of nitrate to be v used for the heat treatment of strong aluminum base alloy sheet, samples of nitrate of a given weight were fused with varying quantities of potassium dichromate, the alkalinity of water solutions of these samples being determined. It was noted that with.
- the amount of an oxygen compound of chromium required depends on various factors, such as the particular com ound or compounds used, the alkalinity an grade of the nitrate, extent of the heat treating'cycle, temperature of the bath, and the character and composition of the metal being treated, but in every case a simple experiment, such as that just explained, maybe used to determine theamount required. Thereafter, the heat treating is conducted in the usual way by immersing the aluminum in the fused bath heated to the desired temperature.
- Still further advantages of the invention are that it makes possible the use of inferior grades of nitrate otherwise impracticable for use as fused baths for the heat treatment of aluminum, and that it reduces the usual care required in washing sheet aluminum after its heat treatment. While the practice of my invention is particularly advantageous where inferior grades of alkali metal nitrates are used as fused heat treating baths, it is also advantageous where the grades of nitrates used are approximately neutral, it having been found that the use of such grades frequently causes severe corrosion.
- the method of heat-treating aluminum comprising heating it in a fused salt bath containing a chromium acid salt in an amount s'ufiicient to substantially inhibit heat-treating. corrosion.
- the method of heat-treating aluminum comprising heating it in a fused bath of sodium nitrate containing potassium dichromate in an amount suflicient to substantially inhibit heat-treating corrosion.
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- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemical Treatment Of Metals (AREA)
Description
Patented 12, 1932 UNITED STATES PATENT: OFFICE i.
mun w. names, or rnnnroar, rmmvuu, Assmuon r summon coll- PAIN'Y'. OF AMERICA, OF PITTSBURGH, SYLV'ANLL PENNSYLVANIA, A CORPORATION OF ramp 1 METHOD or near-Tammie nm'nmimr m Annex-rs N 0 Drawing.
The invention relates to the heat treatment of aluminum and aluminum base alloys in fused salt baths, and to aluminum and aluminum base articles resulting therefrom, both as aluminum and-such alloys being hereinafter designated as aluminum.
The solution or other thermal treatment of aluminum alloys often requires, for satisfactory results, heated to the heat treatment temperature, at which it is held for a period of time and then rapidly cooled as by quenching in water. It 1s common practice to use as a heating me dium a fused salt bath which mayreadily be maintained at the temperature-desired.
A serious disadvantage of heat treating aluminum-in fused salt baths is the corrosion which may take place on the surface of the metal during or after quenching in water.
This is particularly marked where the .fused salt used is an alkali metal nitrate, such as SOdlllIIl nitrate, which is commonly used for such purposes. The exact nature of the corrosive action a matter about which there may besome question, but the known result is the formation of a white powder (probably composed of oxides) on the surface of the metal. This powder is produced in a loosely adherent form on the surface of the article thus treated, constituting a destructible coating capable of being rubbed off.
The corrosive action just described, commonly referred to in the art as staining, is objectionable, particularly in lthe' case of ly worked, as by rolling, in which case the foreign matter formed on the surface of the metal'injures its surface Numerous attempts have been made to overcome difiiculty, but none have-been attendediwith any appreciable degree of success. Forexample, recognizing that the alkalinity of a' that the article be quickly aluminum articles which are to be subsequentsuch purity are expensive and difiicult to ob- Application filed February 80, 1881. Serial No. 617,817.
twin, and alkali metal nitrates, regardless of initial alkalinity, become more alkaline when held ina state of fusion.
An object of this invention is to provide a method of heat treating aluminum in a fused salt bath, which method obviates the foregoing dilficulties, and which not only substantially eliminates corrosive staining of the sheet or article being treated, but also forms a surface on it which is resistant to corrosion in the use of the article,
Another object is to provide aluminum articles free, or substantially so, from heattreating corrosion stains, and having surfaces which are resistant to corrosion.
The invention ispredicated upon my discovery that by heat treating aluminum in a fused salt bath containing an oxygen compound of chromium the surface of the alumi num is not merely free, or substantially free, from corrosive staining, but is rendered resistant to subsequent corrosion. The oxygen compound of chromium may be added'as a chromic or dichromic acid, or as a salt or salts thereof, either singly or in combination, and
the thus modified used bath used for the heat treatment of aluminum in the same manner as other fused baths have been used. Thefused salt bath now in general use for heat treating aluminum consists of alkah metal nitrates, such as sodium nitrate, potassium nitrate, or a mixture of the two, but I prefer to use sodium nitrate chiefly because. of the commercial consideration of cost. The effects of the addition of an oxygen compound of chromium are to inhibit corrosion throughout the heat treating cycle, including the quenching step, and to render the surfaces of the heat treated articles resistant to corrosion.
ill have found that when a chromic acid salt is added to a fusedznitrate bath it serves the dual function of neutralizing the bath'and inhibiting the tendency of the nitrate to become alkaline when held in a state of fusion. It is not necessary that, prior to making the addi tion, the bath be completely neutralized, because the addition of small amounts has been found to exert some inhibitive action upon corrosion even before the bath has been completely neutralized, but I prefer to use an able to add a mixture of chromates and dichromates, with or ithout the addition of chromic or dichromic acid, in all cases corrosion of the surface of the metal is efi'ectively prevented. If a chromate be added, it is usually necessary to use a much greater quantity in order to secure the desired inhibiting effect than where a dichromate is used, although this depends on the grade of nitrate which is used for the bath.
When, in the practice of this invention, it is desired to utilize a fused heat treating bath comprising a nitrate made from Chilean saltpeter containing small amounts of impurities such as chlorides, sulfates, iodates, etc.,' vand being slightly basic in character, the
amount of, chromic acid salt required to neutralize the alkalinity of the nitrate and inhibit subsequent corrosion of the metal treated therein may be determined by titrating the fused salt according to well known analytical procedure. As an example of the use of. this procedure to determine the proper quantity of npotassium dichromate to be added to a ta containing 30,000 pounds of nitrate to be v used for the heat treatment of strong aluminum base alloy sheet, samples of nitrate of a given weight were fused with varying quantities of potassium dichromate, the alkalinity of water solutions of these samples being determined. It was noted that with. the addition of one-half of one per cent of potassium dichromate the aqueous solution of the fused salt mixture was acid in reaction, and it was further determined that with the addition of one-half of one per cent of potassium dichromate there was no visible corrosion. On the basis of this test it was determined that 150 pounds of potassium dichromate should be added to the 30,000-pound tank of molten nitrate. The addition may be, and from the standpoint of safety preferably is, made to the nitrate before it is fused. V
The amount of an oxygen compound of chromium required depends on various factors, such as the particular com ound or compounds used, the alkalinity an grade of the nitrate, extent of the heat treating'cycle, temperature of the bath, and the character and composition of the metal being treated, but in every case a simple experiment, such as that just explained, maybe used to determine theamount required. Thereafter, the heat treating is conducted in the usual way by immersing the aluminum in the fused bath heated to the desired temperature.
The practice of my improved method of heat treating aluminum in a modified fused salt eliminates, or reduces within small and practical limits, the corrosion and pitting of the surface of the metal and the formation of loosely adherent oxides thereon, and, in addition to this, renders the surface of the metal resistant to corrosion. There is also an important attending advantage in the improvement in the appearance of the metal treated, and, in the case of sheet which is to be subjected to a subsequent rolling operation, a substantial advantage incident to the elimination of foreign matter which becomes trapped between the rolls and the metal and mars the surface of the sheet. Still further advantages of the invention are that it makes possible the use of inferior grades of nitrate otherwise impracticable for use as fused baths for the heat treatment of aluminum, and that it reduces the usual care required in washing sheet aluminum after its heat treatment. While the practice of my invention is particularly advantageous where inferior grades of alkali metal nitrates are used as fused heat treating baths, it is also advantageous where the grades of nitrates used are approximately neutral, it having been found that the use of such grades frequently causes severe corrosion.
According to theprovisions of the patentstatutes, I have explained the principle and mode of operation of my invention, and have specifically described how it may be practiced. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
' I claim as my invention:
1. The method of heat-treating aluminum,
comprising heating it in a fused salt bath containing an oxygen compound of chromium in an amount suflicient to substantially inhibit heat-treating corrosion.
2. The method of heat-treating aluminum, comprising heating it in a fused salt bath containing a chromium acid salt in an amount s'ufiicient to substantially inhibit heat-treating. corrosion.
3. The method of heat-treating aluminum, comprising heating it in a fused salt bath containing a dichromate in an amount sufficient to substantially inhibit heat-treating corrosion.
4. The method of heat-treating aluminum,
comprising heating it in a fusedbath of sodium nitrate containing a chromic acid saltin an amountsuflicient to substantially inhibit heat-treating corrosion.
5. The method of heat-treating aluminum, comprising heating it in a fused bath of sodium nitrate containing potassium dichromate in an amount suflicient to substantially inhibit heat-treating corrosion.
' 6. The method of heat-treating aluminum,
comprising heating it in a fused bath of sodium nitrate containing about one-half of one per cent of potassium dichromate in an amount suflicient to substantially inhibit heat-treating corrosion.
In testimony whereof, I si my name.
- RALPH V BRlIDGEs.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US517317A US1840562A (en) | 1931-02-20 | 1931-02-20 | Method of heat-treating aluminum and articles thereby |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US517317A US1840562A (en) | 1931-02-20 | 1931-02-20 | Method of heat-treating aluminum and articles thereby |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US1840562A true US1840562A (en) | 1932-01-12 |
Family
ID=24059305
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US517317A Expired - Lifetime US1840562A (en) | 1931-02-20 | 1931-02-20 | Method of heat-treating aluminum and articles thereby |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US1840562A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE752422C (en) * | 1936-12-31 | 1952-11-04 | Degussa | Process for the treatment of light metals in nitrates or nitrate-nitrite mixtures and fused baths containing bichromate |
| US3540942A (en) * | 1968-02-05 | 1970-11-17 | Nasa | Process for applying black coating to metals |
| US4534794A (en) * | 1981-05-14 | 1985-08-13 | Rockwell International Corporation | Salt corrosion inhibitors |
| US5219617A (en) * | 1989-09-19 | 1993-06-15 | Michigan Chrome And Chemical Company | Corrosion resistant coated articles and process for making same |
-
1931
- 1931-02-20 US US517317A patent/US1840562A/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE752422C (en) * | 1936-12-31 | 1952-11-04 | Degussa | Process for the treatment of light metals in nitrates or nitrate-nitrite mixtures and fused baths containing bichromate |
| US3540942A (en) * | 1968-02-05 | 1970-11-17 | Nasa | Process for applying black coating to metals |
| US4534794A (en) * | 1981-05-14 | 1985-08-13 | Rockwell International Corporation | Salt corrosion inhibitors |
| US5219617A (en) * | 1989-09-19 | 1993-06-15 | Michigan Chrome And Chemical Company | Corrosion resistant coated articles and process for making same |
| US5492766A (en) * | 1989-09-19 | 1996-02-20 | Michigan Chrome And Chemical Company | Corrosion resistant coated articles and process for making same |
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