CA1130707A - Method of processing and inspecting steel billets - Google Patents
Method of processing and inspecting steel billetsInfo
- Publication number
- CA1130707A CA1130707A CA355,858A CA355858A CA1130707A CA 1130707 A CA1130707 A CA 1130707A CA 355858 A CA355858 A CA 355858A CA 1130707 A CA1130707 A CA 1130707A
- Authority
- CA
- Canada
- Prior art keywords
- particles
- magnetizable
- workpiece
- dry powder
- magnetizable particles
- 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
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- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
ABSTRACT
A method and composition for testing a magnetizable workpiece for flaws, the method consisting of magnetizing the workpiece and contemporaneously applying to the work-piece a dry dispersion of magnetizable particles in a light, fluffy, inert dry powder vehicle, and inspecting the work-piece for magnetic particles which become lodged in the flaws. The invention is also directed to the improved composition for use in the method.
A method and composition for testing a magnetizable workpiece for flaws, the method consisting of magnetizing the workpiece and contemporaneously applying to the work-piece a dry dispersion of magnetizable particles in a light, fluffy, inert dry powder vehicle, and inspecting the work-piece for magnetic particles which become lodged in the flaws. The invention is also directed to the improved composition for use in the method.
Description
1~3~707 SPECIFICATION
The present invention is in the field of nondestructive testing using magnetic particles wherein a magnetized workpiece is treated with a dry dispersion of magnetizable particles in a light, fluffy inert dry powder vehicle which prevents agglomeration of the magnetic particles, but is readily removable from the surface once the magnetic par-ticles have become deposited along flaws in the surface of the workpiece.
Techniques employing magnetic particles have been used for flaw detection for considerable periods of time. Such non-destructive testing methods basically include the step of supporting a magnetizable workpiece and passing a direct or alternating current therethrough in order to magnetize the same and then contemporaneously applying magnetic particles either dry or in suspension in water or oil. The stray magnetic fields produced at any surface flaws serve to attract the magnetic particles so that they are readily visible upon inspection. More recently, the magnetic particles have been combined with fluorescent particles either in the form of a water or oil suspension so that the workpiece was inspected under filtered ultra-violet or blac~ light to observe any concentration pattern of fluorescent particles caused by a surface discontinuity.
Prior art patents referring to this type of inspection include Switzer Patent No. 2,267,999 and Kazenas Patent No. 2,936,287.
These patents relate, respectively, to lacquer bonded and resin bonded fluorescent magnetic particles for use in this type of inspection process.
One of the more important areas in which magnetic particle inspection is used is that of inspecting steel ~ r il ~3~707 billets in a continuous manner. Normally, the billet i5 inspected for longitudinal seams and, in the case of fluorescent particles, the inspection takes place under black light in a darkened inspection area.
One of the difficulties with the conventional method of magnetic particle inspection whereinthe particles are applied dry is the fact that the particles tend to agglom-erate and are difficult to maintain in discrete form. The wet method of application whether using water or a hydro-carbon oil has its own drawbacks. For one, there is the problem of freezing of the suspending liquid, or at least an increase in viscosity of the liquid, during periods of cold temperatures. Consequently, it has been common practice to add antifreeze solutions to the bath. Secondly, it is not an easy task to remove the excess liquid from the surface ofthe piece to avoid unwanted background. In addition, there is the problem, particularly with a water suspension, of the particles settling out in pipelines and the like resulting in clogging and loss of magnetic particles. In addition to this, it is not possible to process hot billets with dispersions containing magnetizable particles in conventional liquid suspending media.
The present invention pro~ides an improved suspending medium for magnetic particles to be used in magnetic particle inspection methods, whether such particles are used as such or they are adhered to or coated with a fluorescent material.
In accordance withthe new method, we apply suspensions or dispersions of magnetic material in fluffy, extremely light, relativel~ inert and dry powder vehicles. Typical among such -vehicles are the very finely divided aluminum oxides produced by flame hydrolysis of anhydrous aluminum chloride.
113~7~7 More specifically, the magnetizable particles constitute from about 0.5 to 25% by weight of the dispersion and preferably about 2 to 20% by weig~ n a preferred form of the invention, the dry powder vehicle consists pre-dominantly of particles less than 1 micron in maximum dimen-sion.
In the present invention, magnetic particles which may be of the fluorescent type or not are combined with a fluffy and light powder by agitating the two mechanically or by means of air currents to effect uniform distribution of the magnetic material through the dispersion. The light, fluffy and non-sticking powders used in accordance with the present invention exhibit practically no "scraping" action with respect to the indications being formed by the magnetic particles.
Since the powders do not stick to the surface of the billet, excess powders merely fall of the surface during processing or they can be blown off with a gentle stream of air. It has been further found that processing and handling of the fluffy suspensions can be simpler than involved with the less bulky and heavier products.
The method of the present invention is particularly applicable to the use of the type of improved fluorescent magnetic powders described in Borrows Canadian Serial No.
351,690 and assigned to the same assignee as the present application. In the aforementioned copending application there is described a composition for nondestructive testing of magnetizable workpieces employing discrete magnetic particles having a ferromagnetic particle core, fluorescent pigment particles attached to the core, and a cascading opacifier associated with the core, the fluorescent pigment ~3~707 particles being at least 2 microns in maximum dimension.
In the preferred form of the invention, the cascading opac-ifier is fluoranthene, and t~e core particles have a maximum dimension of from 25 to 150 microns. The core particles ~nd daylight fluorescent pigment particles are held together by means of encapsulation with a filmforming resin which also serves as the carrier for the opacifier.
The preferred fluffy vehicle is a finely divided alum-inum oxide produced by flame hydrolysis of anhydrous aluminum oxide. One such material is available commercially as ~Aluminum Oxide C" marketed by Degussa, Inc. This material is said to ha~e a very large specific surface area. Crystallo-graphic analysis indicates that the material s primarily a gamma aluminum oxide having a slight delta structure. The improved aluminum oxide has a strong tendency to acquire a positive charge which may account for its lack of adherence to the test surfaces.
The magnetizable particles constitute from about 0.5 to 25% by weight of the composition, and preferably from 2 to 20% by weight. The dispersion can be made up by mech-anically agitating the two materials together or by using a suitable current of air. The application of the particles is substantially the same as the present technique for apply-ing magnetizable particles in dry form, namely, suspending the dispersion in air and carrying the same to the surface of the part. The suspension should be applied in such a way that the powders reach the magnetized surface in a uniform cloud with a minimum of motion. Under these conditions, the particles come under the influence of the leakage fields while suspended in air, and have three-dimensional mobility.
1~3~707 This condition can be best achi~ved when the magnetized surface is vertical or overhead. Since the fluffy, dry particles do not adhere to the surface, it is usually not necessary to use outside forces to re ve excess particles from the surface, although a gentle stream of air can be used if desired. The workpiece is then inspected either under ordinary light or under ultraviolet radiation for clusters of the magnetizable particles. Where magnetizable particles of the type described in the aforementioned Borrows applica-tion are used, the inspection can proceed simultaneously in white light and in ultraviolet light.
The use of the improved composition of the present invention in the magnetic particle inspection method has several distinct advantages. For one, the problems associ-ated with low temperatures are avoided inasmuch as no anti-freeze additions are necessary. The relatively hydrophobic fluffy powders are also superior to other materials in that they do not absorb moisture from the air. Furthermore, it is easier to fix the formed indications on dry billets than it is on wet ones. It i9 also possible to process hot billets with the improved composition of the present invention, since the carrier powders will not melt or decompose up to a temperature of at least 300F.
It should be evident that various modifications can be made tothe described embodiments without departing from the scope of the present invention.
_5_
The present invention is in the field of nondestructive testing using magnetic particles wherein a magnetized workpiece is treated with a dry dispersion of magnetizable particles in a light, fluffy inert dry powder vehicle which prevents agglomeration of the magnetic particles, but is readily removable from the surface once the magnetic par-ticles have become deposited along flaws in the surface of the workpiece.
Techniques employing magnetic particles have been used for flaw detection for considerable periods of time. Such non-destructive testing methods basically include the step of supporting a magnetizable workpiece and passing a direct or alternating current therethrough in order to magnetize the same and then contemporaneously applying magnetic particles either dry or in suspension in water or oil. The stray magnetic fields produced at any surface flaws serve to attract the magnetic particles so that they are readily visible upon inspection. More recently, the magnetic particles have been combined with fluorescent particles either in the form of a water or oil suspension so that the workpiece was inspected under filtered ultra-violet or blac~ light to observe any concentration pattern of fluorescent particles caused by a surface discontinuity.
Prior art patents referring to this type of inspection include Switzer Patent No. 2,267,999 and Kazenas Patent No. 2,936,287.
These patents relate, respectively, to lacquer bonded and resin bonded fluorescent magnetic particles for use in this type of inspection process.
One of the more important areas in which magnetic particle inspection is used is that of inspecting steel ~ r il ~3~707 billets in a continuous manner. Normally, the billet i5 inspected for longitudinal seams and, in the case of fluorescent particles, the inspection takes place under black light in a darkened inspection area.
One of the difficulties with the conventional method of magnetic particle inspection whereinthe particles are applied dry is the fact that the particles tend to agglom-erate and are difficult to maintain in discrete form. The wet method of application whether using water or a hydro-carbon oil has its own drawbacks. For one, there is the problem of freezing of the suspending liquid, or at least an increase in viscosity of the liquid, during periods of cold temperatures. Consequently, it has been common practice to add antifreeze solutions to the bath. Secondly, it is not an easy task to remove the excess liquid from the surface ofthe piece to avoid unwanted background. In addition, there is the problem, particularly with a water suspension, of the particles settling out in pipelines and the like resulting in clogging and loss of magnetic particles. In addition to this, it is not possible to process hot billets with dispersions containing magnetizable particles in conventional liquid suspending media.
The present invention pro~ides an improved suspending medium for magnetic particles to be used in magnetic particle inspection methods, whether such particles are used as such or they are adhered to or coated with a fluorescent material.
In accordance withthe new method, we apply suspensions or dispersions of magnetic material in fluffy, extremely light, relativel~ inert and dry powder vehicles. Typical among such -vehicles are the very finely divided aluminum oxides produced by flame hydrolysis of anhydrous aluminum chloride.
113~7~7 More specifically, the magnetizable particles constitute from about 0.5 to 25% by weight of the dispersion and preferably about 2 to 20% by weig~ n a preferred form of the invention, the dry powder vehicle consists pre-dominantly of particles less than 1 micron in maximum dimen-sion.
In the present invention, magnetic particles which may be of the fluorescent type or not are combined with a fluffy and light powder by agitating the two mechanically or by means of air currents to effect uniform distribution of the magnetic material through the dispersion. The light, fluffy and non-sticking powders used in accordance with the present invention exhibit practically no "scraping" action with respect to the indications being formed by the magnetic particles.
Since the powders do not stick to the surface of the billet, excess powders merely fall of the surface during processing or they can be blown off with a gentle stream of air. It has been further found that processing and handling of the fluffy suspensions can be simpler than involved with the less bulky and heavier products.
The method of the present invention is particularly applicable to the use of the type of improved fluorescent magnetic powders described in Borrows Canadian Serial No.
351,690 and assigned to the same assignee as the present application. In the aforementioned copending application there is described a composition for nondestructive testing of magnetizable workpieces employing discrete magnetic particles having a ferromagnetic particle core, fluorescent pigment particles attached to the core, and a cascading opacifier associated with the core, the fluorescent pigment ~3~707 particles being at least 2 microns in maximum dimension.
In the preferred form of the invention, the cascading opac-ifier is fluoranthene, and t~e core particles have a maximum dimension of from 25 to 150 microns. The core particles ~nd daylight fluorescent pigment particles are held together by means of encapsulation with a filmforming resin which also serves as the carrier for the opacifier.
The preferred fluffy vehicle is a finely divided alum-inum oxide produced by flame hydrolysis of anhydrous aluminum oxide. One such material is available commercially as ~Aluminum Oxide C" marketed by Degussa, Inc. This material is said to ha~e a very large specific surface area. Crystallo-graphic analysis indicates that the material s primarily a gamma aluminum oxide having a slight delta structure. The improved aluminum oxide has a strong tendency to acquire a positive charge which may account for its lack of adherence to the test surfaces.
The magnetizable particles constitute from about 0.5 to 25% by weight of the composition, and preferably from 2 to 20% by weight. The dispersion can be made up by mech-anically agitating the two materials together or by using a suitable current of air. The application of the particles is substantially the same as the present technique for apply-ing magnetizable particles in dry form, namely, suspending the dispersion in air and carrying the same to the surface of the part. The suspension should be applied in such a way that the powders reach the magnetized surface in a uniform cloud with a minimum of motion. Under these conditions, the particles come under the influence of the leakage fields while suspended in air, and have three-dimensional mobility.
1~3~707 This condition can be best achi~ved when the magnetized surface is vertical or overhead. Since the fluffy, dry particles do not adhere to the surface, it is usually not necessary to use outside forces to re ve excess particles from the surface, although a gentle stream of air can be used if desired. The workpiece is then inspected either under ordinary light or under ultraviolet radiation for clusters of the magnetizable particles. Where magnetizable particles of the type described in the aforementioned Borrows applica-tion are used, the inspection can proceed simultaneously in white light and in ultraviolet light.
The use of the improved composition of the present invention in the magnetic particle inspection method has several distinct advantages. For one, the problems associ-ated with low temperatures are avoided inasmuch as no anti-freeze additions are necessary. The relatively hydrophobic fluffy powders are also superior to other materials in that they do not absorb moisture from the air. Furthermore, it is easier to fix the formed indications on dry billets than it is on wet ones. It i9 also possible to process hot billets with the improved composition of the present invention, since the carrier powders will not melt or decompose up to a temperature of at least 300F.
It should be evident that various modifications can be made tothe described embodiments without departing from the scope of the present invention.
_5_
Claims (12)
1. The method of testing a magnetizable workpiece for flaws which comprises: magnetizing said workpiece, apply-ing to said workpiece a dry dispersion of magnetizable particles in a light, fluffy, inert dry powder vehicle, and inspecting said workpiece for magnetic particles which become lodged in said flaws.
2. The method of claim 1 in which: said workpiece in a steel billet.
3. The method of claim 1 in which: said magnetizable particles are capable of fluorescing under ultraviolet light.
4. The method of claim 1 in which: said dry powder vehicle is a finely divided aluminum oxide produced by flame hydrolysis of anhydrous aluminum chloride.
5. The method of claim 1 in which: said magnetizable particles constitute from 0.5 to 25% by weight of said dis-persion.
6. The method of claim 1 in which: said magnetizable particles constitute from 2 to 20% by weight of said dis-persion.
7. The method of claim 1 in which: said dry powder vehicle consists predominantly of particles less than 1 micron in maximum dimension.
8. A composition suitable for use in the nondestruc-tive testing of magnetizable workpieces comprising: a combination of dry magnetizable particles admixed with a light, fluffy, inert dry powder.
9. A composition according to claim 8 in which: said magnetizable particles have the property of fluorescing when subjected to ultraviolet radiation.
10. A composition according to claim 8 in which:
said powder is a finely divided aluminum oxide produced by flame hydrolysis of anhydrous aluminum chloride.
said powder is a finely divided aluminum oxide produced by flame hydrolysis of anhydrous aluminum chloride.
11. A composition according to claim 8 in which:
said magnetizable particles constitute from 0.5 to 25%
by weight of said composition.
said magnetizable particles constitute from 0.5 to 25%
by weight of said composition.
12. A composition according to claim 8 in which:
said dry powder consists predominantly of particles less than 1 micron in maximum dimension.
said dry powder consists predominantly of particles less than 1 micron in maximum dimension.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12968580A | 1980-03-12 | 1980-03-12 | |
| US129,685 | 1980-03-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1130707A true CA1130707A (en) | 1982-08-31 |
Family
ID=22441121
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA355,858A Expired CA1130707A (en) | 1980-03-12 | 1980-07-10 | Method of processing and inspecting steel billets |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1130707A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111426747A (en) * | 2020-04-30 | 2020-07-17 | 国电锅炉压力容器检验有限公司 | Water-based magnetic suspension for low-temperature environment and preparation method thereof |
-
1980
- 1980-07-10 CA CA355,858A patent/CA1130707A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111426747A (en) * | 2020-04-30 | 2020-07-17 | 国电锅炉压力容器检验有限公司 | Water-based magnetic suspension for low-temperature environment and preparation method thereof |
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| Date | Code | Title | Description |
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| MKEX | Expiry |