GB2045285A - Masking Ferrous Surfaces with Flame-sprayed Aluminium during Carburising Nitriding or Boriding - Google Patents
Masking Ferrous Surfaces with Flame-sprayed Aluminium during Carburising Nitriding or Boriding Download PDFInfo
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- GB2045285A GB2045285A GB7943105A GB7943105A GB2045285A GB 2045285 A GB2045285 A GB 2045285A GB 7943105 A GB7943105 A GB 7943105A GB 7943105 A GB7943105 A GB 7943105A GB 2045285 A GB2045285 A GB 2045285A
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- Prior art keywords
- process according
- aluminium
- spray
- layer
- heat treatment
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Links
- 239000004411 aluminium Substances 0.000 title claims abstract description 36
- 229910052782 aluminium Inorganic materials 0.000 title claims abstract description 36
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 title claims abstract description 36
- 238000005121 nitriding Methods 0.000 title claims abstract description 6
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 title 1
- 230000000873 masking effect Effects 0.000 title 1
- 238000010438 heat treatment Methods 0.000 claims abstract description 31
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 24
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 20
- 239000010959 steel Substances 0.000 claims abstract description 20
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052742 iron Inorganic materials 0.000 claims abstract description 12
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 8
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910052796 boron Inorganic materials 0.000 claims abstract description 7
- 239000007787 solid Substances 0.000 claims abstract description 7
- 238000010285 flame spraying Methods 0.000 claims abstract description 4
- 239000010410 layer Substances 0.000 claims description 40
- 238000000034 method Methods 0.000 claims description 33
- 230000008569 process Effects 0.000 claims description 33
- 239000007921 spray Substances 0.000 claims description 18
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 239000003795 chemical substances by application Substances 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 4
- 239000011241 protective layer Substances 0.000 claims description 4
- 238000005507 spraying Methods 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 3
- 238000010276 construction Methods 0.000 claims description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims 2
- 239000000446 fuel Substances 0.000 claims 2
- 229910000838 Al alloy Inorganic materials 0.000 claims 1
- 239000001273 butane Substances 0.000 claims 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims 1
- 239000001294 propane Substances 0.000 claims 1
- 238000011282 treatment Methods 0.000 abstract description 17
- 239000000463 material Substances 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 8
- 229910052802 copper Inorganic materials 0.000 description 8
- 239000010949 copper Substances 0.000 description 8
- 230000001681 protective effect Effects 0.000 description 7
- 238000000576 coating method Methods 0.000 description 6
- 238000009792 diffusion process Methods 0.000 description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 229910052684 Cerium Inorganic materials 0.000 description 4
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 238000010791 quenching Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 239000000243 solution Substances 0.000 description 4
- 238000007792 addition Methods 0.000 description 3
- 238000005422 blasting Methods 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 230000007812 deficiency Effects 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000011814 protection agent Substances 0.000 description 2
- 239000003223 protective agent Substances 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- WATWJIUSRGPENY-UHFFFAOYSA-N antimony atom Chemical compound [Sb] WATWJIUSRGPENY-UHFFFAOYSA-N 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001784 detoxification Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000002500 effect on skin Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000007730 finishing process Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000010310 metallurgical process Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000009972 noncorrosive effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 235000019353 potassium silicate Nutrition 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000007788 roughening Methods 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
- 229910000859 α-Fe Inorganic materials 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
- C23C8/04—Treatment of selected surface areas, e.g. using masks
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/68—Temporary coatings or embedding materials applied before or during heat treatment
- C21D1/72—Temporary coatings or embedding materials applied before or during heat treatment during chemical change of surfaces
-
- 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
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/06—Metallic material
- C23C4/08—Metallic material containing only metal elements
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Plasma & Fusion (AREA)
- Coating By Spraying Or Casting (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
The surface of iron and steel is locally protected against the take up of carbon, nitrogen and boron during treatment in carburising, nitriding and boriding gaseous and solid media at temperatures of up to 1100 DEG C., by prior to the heat treatment, flame spraying with an aluminium or aluminium layer having a thickness of 10 to 100 mu m.
Description
SPECIFICATION
Process for the Local Protection of the
Surfaces of Iron and Steel Parts During Heat
Treatment
The present invention is concerned with a process for the local protection of the surfaces of iron and steel objects against the take up of carbon, nitrogen or boron in the case of heal treating in gaseous and solid media at temperatures of up to 1 000C.
In the case of the thermochemical heat treatment of iron and steel, it is often necessary locally to protect selected parts of the surface of the workpiece against the action of carbon, nitrogen or boron, whereas the other parts are to be subjected as completely as possible to the action of these media. in this way, for example, in the case of subsequent quenching, substantially localised differences in hardness of the workpiece can be achieved. The softer parts which, for example, contain less carbon can then subsequently be more easily mechanically worked, whereas the unprotected parts have achieved the high required hardness.
Furthermore, depending upon the nature of the stressing of the workpiece, the differing strength values of the workpiece are also of importance.
A large number of processes is known by
which such a local protection can be achieved.
Thus, the parts of the workpiece to be
protected can be covered with steel parts which
then, however, suffer from considerable wear. It is
also known to cover with agents based on boric
acid, waterglass and glass powder, most of which
are mixed with metal oxides and enriched with
organic solvents and filling materials.
Furthermore, it is known that, for this purpose,
various metal layers can be applied. However,
when a very good protective effect is required,
only copper has proved to be useful, this being
galvanically deposited on the parts of the
workpiece to be protected.
It is also known that oxide-forming components in
steel generally inhibit the passage of carbon and
nitrogen through the surface of the iron work
material. A necessary prerequisite for the action
of these elements is that, in spite of their dilution
in the steel, even in the case of a smaller oxygen
potential than iron, these are oxidised and an
appropriately oxidising atmosphere is present
during the heat treatment process. Of course,
such a general statement cannot provide a basis
for a process for a local surface protection in the
course of thermochemical treatments which
comprises applying any desired, easily oxidised
metal layers since, especially with regard to the
adhesive strength and the porosity of such layers,
no general prediction is possible.
On the other hand, a large number of technical
solutions to the problem are known which utilise
the action of easily oxidisable metals for scale and
corrosion protection, including the application of
canthal and aluminium, optionally with the
addition of magnesium and zinc, as well as of some highly alloyed steels, by the thermochemical and spray-metallurgical process and by dipping processess. It is known that aluminium with a layer thickness of 200yam.
provides protection against scaling up to a temperature of 6000C. An inhibition of scaling can also be achieved up to a temperature of $500C. by aluminium when the layer thickness is about 300cm. However, for this purpose, a preheating of the workpiece (alitising) of several hours at a temperature below the melting point of aluminium is necessary in order, due to a solid body reaction, completely to react with the surface areas of the steel but dripping off not only in the course of the alitising but also when using the higher temperatures cannot be excluded. The wide compound and diffusion zone resulting from the preheating prevents scaling of the base work material.
It is also known that such thick aluminium layers provide a protection against the decarbonisation of high carbon steels in the course of heat treatment and of heating forming treatment (see published Federal Republic of
Germany Patent Application No. 23 1 9 673).
Recently, it has been suggested in published
Federal Republic of Germany Patent Application
No. 23 19 678 to mix aluminium with cerium and other lanthanides and, by means of a dipping process and a subsequent high temperature treatment in the air, apparently for the purpose of forming an especially thick cerium/aluminium mixed oxide layer, to utilise this as a protection against scaling and also to prevent the take up of carbon during pyrolysis processes. A technical solution using aluminium for local surface protection in the case of the thermochemical treatment of workpieces is not known.
Furthermore, it is suggested in German
Democratic Republic Patent Specification
No.117,893 that, before the heat treatment, to the parts of the surface of iron or steel parts to be protected, there is applied a layer of a metal tending to surface segration, especially antimony or a compound thereof.
A disadvantage of the above-described processes is their suceptibility to trouble. With the exception of the use of galvanically deposited copper coatings, the processes also only provide a limited protective action. In the case of copper coatings, quality deficiencies occur when the galvanic deposition does not provide a pore-free coating. The process is also generally uneconomic. A further disadvantage of this process is the endangering of the environment due to the use of cyanide-containing baths and the necessity of having to provide expensive detoxification or neutralising plant for waste water. Furthermore, copper coatings have, in typical cases of application, the unintended side effect that, even after the thermochemical treatments, they still adhere firmly to the workpiece and even remain in the case of subsequent finishing processes.Subsequent heat treatment, for example for the purpose of removing quenching stresses, are, inter alia, also carried out by heating with medium frequency but because of the high electrical conductivity of the copper and as a result of the skin effect, an insufficient cross-sectional heating is obtained.
Other metal coatings apart from copper, for example nickel coatings, do not have a sufficient protective action or are uneconomic, as in the case of tinning.
Technical solutions which utilise the action of strongly oxidising metals as local protection agents in the case of thermochemical treatments are unknown. Aluminium layers of the usual type which are not post-heat treated are unsuitable.
Alitising layers such as are used as a protection against corrosion at temperatures of up to 9500C.
cannot be employed for local protection in the case of thermochemical treatments since steels are, above 9000 C., generally alloyed to quite considerable depths. In order to utilise the known alitising layers, comparatively large amounts would be needed, which involve a high material loss and a considerable expenditure of labour for subsequent working off. In particular, however, the protective action is incomplete, especially against enrichment with carbon. Parts which have been experimentally protected by alitising were too hard on the surface after quenching. The preheat treatment necessary in the case of thick layers would certainly also not be an economic solution to the problem. Obviously these are the reasons why aluminium is not used as a local protection agent in the case of thermochemical heat treatments.Furthermore, the limitation to a temperature of 9500C. is to be regarded as being a deficiency since some treatments, for example boriding, need temperatures of up to 11 000C.
The reason for the too high carbon contents in layers near the edge, which occur in the case of the usual alitising layers, is recognised. They are to be explained using, as an example, a carburising steel containing 0.2% by weight of carbon, which is coated with a 300m. thick layer of aluminium.
During the preheating stage of the alitising process below the melting point of aluminium, the known alitising layer is formed with its diffusion zone which, in the case of the subsequent thermochemical treatment, spreads further. The diffusion zone consists proponderantly of aluminium-containing ferritic material in which, however, only an insignificantly small amount of carbon dissolves. Therefore, this is transferred, simultaneously with the formation and the growth of the diffusion zone, into the deeper zones of the steel, which are austenitic at the heat treatment temperature, the carbon content at the phase boundary between the edge layer ferrite and the steel thereby increasing to about 0.4% by weight.
However, this increase in concentration is already sufficient to bring about, after the quenching, unsuitably high hardness values. The high edge carbon content, which occurs in the case of the experimental use of alitising layers, is not due to an insufficient protective action of aluminium against neighbouring media but rather in the above-described displacement effect.
The use of additions of cerium to aluminium and the high temperature treatment thereby involved cannot be carried out at least in the case of high-quality carburising steels. Apart from the necessity of having to provide a heat-treatment device and of using cerium, which would make such a process uneconomic, in the case of carburising steels, a grain increase takes place during the high temperature treatment and, as a result thereof, a decrease of the strength and of the plasticity of the workpiece occurs. It is also to be expected that the edge carbon content, due to the same reasons as in the case of the conventional alitising layers, would be too high for use as a local protective agent in the case of thermochemical treatments.It is an object of the present invention to avoid the use of copper as a local protective agent in the case of thermochemical heat treatments of iron and steel, thereby overcoming the environmental dangers caused by the process, and to provide a way of bringing about a local protection in a cheaper and simpler manner.
A further object of the present invention is to provide a process for local protection against the take-up of carbon, nitrogen and boron in the case of thermochemical treatments at temperatures of up to 11 000C. which provides the same protective action as galvanically deposited copper layers but is less susceptible to trouble.
Furthermore, the process is to be such that it can be carried out without extensive pre-treatment and intermediate treatments and is to be substantially more economic than galvanic coppering.
The process according to the present invention is to be especially suitable for use in large-scale production and to provide the possibility of being automated.
Thus, according to the present invention, there is provided a process for the local protection of the surface of iron and steel objects against the take up of carbon, nitrogen and boron in the case of heat treatment in carburising, nitriding or boriding gaseous and solid media at temperatures of up to 11 000C., wherein, prior to the heat treatment, the part of the surface of the object to be protected is flame sprayed with an aluminium
layer with a thickness of 10 to 100cm. and preferably of 10 to 30,um., the construction of the
preferably mechanised flame spraying device, the
parameters of the spray pistol used, the distance of the spray pistol from the object, which is
preferably about 1 5 to 25 cm., the period of time
of the spraying and the intensity of the spray jet
being so co-ordinated with one another that the thickness of the applied layer of aluminium is within the given range.
The said small layer thickness makes it
possible to omit a pre-heating for the production of an alitising layer since the layer, even in the
case of a temperature above the melting point of
aluminium, remains, as a result of the surface tension, until the formation of the alloying and diffusion zone is concluded at the temperature of the thermochemical heat treatment, even without pre-heating. If thicker layers were used, without a comparatively long pre-heating at a temperature in the region of 6000C., there is danger of the aluminium dripping off. Furthermore, with increasing layer thicknesses, those deficiencies arise which also make the use of atilising layers impossible.Just as unfavourable as too great a layer thickness is one of less than 10cm. In this case, the intermetallic FexAly phases dissolve completely in the course of a thermochemical heat treatment above 9000C, and the aluminiumcontaining ferritic phase which generally remains no longer displays a satisfactory protective action in the case of the relative low oxygen potential of the surrounding carburising, nitriding and boriding media.
It has a favourable effect that aluminium is liquid at the temperatures of most thermochemical heat treatments so that nonuniformities in a microscopic sense, i.e. pores and the like, and rapidly compensated, even during heating up. The process also does not fail when the spray-metallurgical layer displays visible hoies under the microscope through which the base work material can still be observed.
It is known that modern spray processes admittedly quickly apply thick layers but when they are used for providing-thin layers and thus
are only used for short spray times,
microscopically observable non-uniformities arise, for which reasons these spray processes are
unsuitable in the present case.
It is preferable to use aluminium wire for the
spraying. No particular requirements are
demanded of the quality of the aluminium: thus,
for example, aluminium with additions of
magnesium can be used. For melting the material
to be sprayed, it has proved to be advantageous
to use a fuel-oxygen mixture and especially a
propane-oxygen or a butane-oxygen mixture.
Furthermore, it is preferable to cover with metal
sheets or the like and/or to wet with separating
agents those regions of the surface of the
workpiece which are not to be covered with a
protective layer, as well as endangered parts of
the spray device.
Because of its adhesion, the sprayed-on
aluminium layer permits the workpiece provided
with a protective layer to be mechanically worked
before the thermochemical heat treatment.
The thermochemical treatment of the
workpiece can be carried out at temperatures of
up to 1 1000C. in solid or gaseous media, for
example, in carburising powders, in ends gas or
drop gas and in ammonia or ammonia
containing gases, in the case of nitriding and carbonising, and also in solid
boriding compounds, an effective local
protection against the take up of
carbon, nitrogen and boron thereby
being achieved. In general, after hardening the workpiece, it is usual to carry out a cleaning, for example, by mechanical blasting, which completely removes the brittle FexAiv phases. A removal of the firmly-adhering ferritic phase present is not necessary when the workpiece is to be used under noncorrosive or not very corrosive conditions, for example in motors or gears.In other cases, it is necessary to ascertain whether the relatively soft ferritic layer, which, in the case of the use of aluminium layers of from 10 to 30 ym. thickness, amounts, after the heat treatment, to about 100 mum., must also be removed by comparatively long blasting.
Medium frequency heating of protected workpieces which may be necessary can be carried out immediately after the hardening, without removal of the protective layers, since the characteristic electrical values of the diffusion zone are close to those of the base work material.
The following Example is given for the purpose of illustrating the present invention:
Example
In the case of connecting rods for carburetor engines made of the work material 16 MnCr 5, the connecting rod eyes must be carburised. The thermochemical heat treatment takes place in a regulated gas atmosphere at 9300 C. with a carbon potential of 0.9%.
The carburised hardness depth is 1.2 mm. The shaft must not only have a sufficient strength but also an increased plasticity. Therefore, it is necessary completely to protect the shaft against carburisation. The protection is thereby ensured in that the connecting rods, after cleaning and roughening of the surface by mechanical blasting, are provided with a layer of aluminium of 10 to 30 Mm. thickness. The aluminium, in the form of wire, is applied by means of flame sprayers, using a propane-oxygen mixture, the distance between the spray nozzle and the connecting rod being 20 cm.
The aluminium is sprayed on to the shaft of the connecting rod in a mechanised plant. This plant consists essentally of two staggered transport bands arranged one behind the other on which the connecting rods are passed by the spray nozzles. The alignment of the connecting rods is accomplished by means of sheet metal guides. The connecting rods are also rolled over between the transport bands by means of sheet metal guides.
Endangered parts of the spray plant are coated with separating agents and the connecting rod eyes are covered. The further machining of the connecting rods takes place after the flame spraying.
After the carburising of the unprotected parts and the hardening, the connecting rods are again mechanically blasted, brittle parts of the aluminium layer thereby being removed. The shaft is then subjected to medium frequency heating in order to achieve the required high degree of plasticity.
Claims (11)
1. Process for the local protection of the surface of iron and steel objects against the take up of carbon, nitrogen and boron in the case of heat treatment in carburising, nitriding and boriding gaseous and solid media at temperatures of up to 11 000C., wherein, prior to the heat treatment, the part of the surface of the object to be protected is flame sprayed with an aluminium layer with a thickness of 10 to 100 yam., the construction of the flame spraying device used, the parameters of the spray pistol used, the distance of the spray pistol from the object, the period of time of spraying and the intensity of the spray jet being so co-ordinated with one another that the thickness of the applied layer of aluminium is within the given range.
2. Process according to claim 1, wherein the distance of the spray piston from the object is about 15 to 25 cm.
3. Process according to claim 1 or 2, wherein the layer of aluminium applied has a thickness of
10to30m.
4. Process according to any of the preceding claims, wherein a mechanical spray device is used.
5. Process according to any of the preceding claims, wherein an aluminium or aluminium alloy is used for the spraying.
6. Process according to any of the preceding claims, wherein the spray device is operated with a mixture of fuel and oxygen.
7. Process according to claim 6, wherein the fuel used is propane or butane.
8. Process according to any of the preceding claims, wherein parts of the object which are not to be spray coated and endangered parts of the spray device are covered and/or coated with a separating agent.
9. Process according to any of the preceding claims, wherein the object provided with the protective layer is worked prior to a thermochemical heat treatment.
10. Process according to claim 1 for the local protection of the surface of iron and steel objects, substantially as hereinbefore described and exemplified.
11. Iron and steel objects, a part of the surface of which has been protected by the process according to any of claims 1 to 1 0.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DD20995878A DD140761B1 (en) | 1978-12-20 | 1978-12-20 | PROCESS FOR THE LOCAL PROTECTION OF IRON AND STEEL PARTS FOR HEAT TREATMENTS |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2045285A true GB2045285A (en) | 1980-10-29 |
| GB2045285B GB2045285B (en) | 1983-04-20 |
Family
ID=5515984
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7943105A Expired GB2045285B (en) | 1978-12-20 | 1979-12-14 | Masking ferrous surfaces with flamesprayed aluminium during carburising nitriding or boriding |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5594435A (en) |
| DD (1) | DD140761B1 (en) |
| DE (1) | DE2947799A1 (en) |
| FR (1) | FR2444724A1 (en) |
| GB (1) | GB2045285B (en) |
| HU (1) | HU184051B (en) |
| IT (1) | IT7928184A0 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5085713A (en) * | 1988-07-22 | 1992-02-04 | Mitsubishi Denki Kabushiki Kaisha | Method of forming a partially carburized starter output shaft |
| EP0860516A2 (en) * | 1997-02-04 | 1998-08-26 | Fuji Kihan Co., Ltd. | Method for forming metallic coat |
| US6291012B1 (en) | 1997-02-04 | 2001-09-18 | Fuji Kihan Co., Ltd. | Method for forming a metallic coat by impacting metallic particles on a workpiece |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR638322A (en) * | 1927-05-10 | 1928-05-22 | Aubert Et Duval Freres Soc | Process for protecting certain parts of a part intended to be hardened by nitriding against the hardening action of nitrogen |
-
1978
- 1978-12-20 DD DD20995878A patent/DD140761B1/en not_active IP Right Cessation
-
1979
- 1979-11-28 DE DE19792947799 patent/DE2947799A1/en not_active Withdrawn
- 1979-12-07 HU HU79BA3900A patent/HU184051B/en unknown
- 1979-12-12 FR FR7930434A patent/FR2444724A1/en active Granted
- 1979-12-14 GB GB7943105A patent/GB2045285B/en not_active Expired
- 1979-12-19 IT IT7928184A patent/IT7928184A0/en unknown
- 1979-12-19 JP JP16416079A patent/JPS5594435A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5085713A (en) * | 1988-07-22 | 1992-02-04 | Mitsubishi Denki Kabushiki Kaisha | Method of forming a partially carburized starter output shaft |
| EP0860516A2 (en) * | 1997-02-04 | 1998-08-26 | Fuji Kihan Co., Ltd. | Method for forming metallic coat |
| EP0860516A3 (en) * | 1997-02-04 | 1999-05-19 | Fuji Kihan Co., Ltd. | Method for forming metallic coat |
| US6291012B1 (en) | 1997-02-04 | 2001-09-18 | Fuji Kihan Co., Ltd. | Method for forming a metallic coat by impacting metallic particles on a workpiece |
Also Published As
| Publication number | Publication date |
|---|---|
| DD140761B1 (en) | 1981-02-25 |
| FR2444724B1 (en) | 1983-11-10 |
| DD140761A1 (en) | 1980-03-26 |
| JPS5594435A (en) | 1980-07-17 |
| GB2045285B (en) | 1983-04-20 |
| DE2947799A1 (en) | 1980-07-03 |
| HU184051B (en) | 1984-06-28 |
| IT7928184A0 (en) | 1979-12-19 |
| FR2444724A1 (en) | 1980-07-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |