EP0191008B1 - Shell or tubular object and method to manufacture the same - Google Patents
Shell or tubular object and method to manufacture the same Download PDFInfo
- Publication number
- EP0191008B1 EP0191008B1 EP19860850030 EP86850030A EP0191008B1 EP 0191008 B1 EP0191008 B1 EP 0191008B1 EP 19860850030 EP19860850030 EP 19860850030 EP 86850030 A EP86850030 A EP 86850030A EP 0191008 B1 EP0191008 B1 EP 0191008B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- additional
- core body
- spraying
- metal alloy
- 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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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D23/00—Casting processes not provided for in groups B22D1/00 - B22D21/00
- B22D23/003—Moulding by spraying metal on a surface
Definitions
- the invention relates to a method to manufacture a shell or tubular object to be incorporated in a heat and corrosion resistant part of a combustion engine, as defined in the first part of claim 1.
- the background of the invention is a desire to make it possible to operate internal combustion engines at a higherworking temperature, whereby an increased efficiency and a more complete combustion can be achieved.
- it is a well-known problem to accomplish temperature and corrosion resistance of the materials, especially in combustion chambers and exhaust channels, in case the working temperature is to be raised above what is normal in today's engines.
- ceramic materials are high-temperature and corrosion resistant, but it is complicated and expensive to combine ceramics with other, metallic construction materials, such as iron and nickel alloys. Tensions are caused by different temperature coefficients. Certain ceramics will also be subjected to phase transformations in temperature intervals within or very close to the working temperatures in question. Moreover, the subsequent treatment, e. g. the boring of holes, becomes more difficult, if ceramics are used.
- the published Swedish Patent Application SE-A-8 300 603-1 discloses a method of manufacturing a machine part, including a heat insulated inlet gas channel, by thermally spraying a very thin first layer, having a thickness of 0.1-0.2 mm, of a soft metal material, such as zinc, tin, lead, copper or aluminium, onto a sand core.
- a second layer, having a thickness of 0.5-2.5 mm, of a metal material, such as carbon steel, is thermally sprayed onto the first layer, and thereafter a third layer, serving as a heat barrier and consisting of a ceramic material is applied, e. g. by thermal spraying.
- the sand core with the three layers applied thereon is placed in a mold for molding the machine part in a conventional manner. Upon molding, the sand core is removed, so that the three layers form an internal surface of a channel in the machine part.
- the innermost layer, forming the internal surface layer of the machine part is not corrosion resistant and is not suitable e. g. for exhaust channels.
- the melting point of the soft metal material is far too low to permit the use in an exhaust channel of a combustion engine.
- a typical temperature of the exhaust gases is about 850 °C, whereas the melting point of Zn is about 420 °C.
- the object of the invention is to eliminate the disadvantages and restrictions of the known methods and to enable a simple manufacture of shell or tubular objects, even with a complicated geometry, by thermal spraying of a heat and corrosion resistant metal alloy so as to form a dense, first surface layer and an additional layer serving as a heat barrier, without any risk of cracking during the spraying process.
- a further object is to enable the molding of such an object into a molded body having one or several channels or cavities constituted by the molded shell or tubular object according to the invention.
- the main object is achieved by a method as defined in the characterizing clause of claim 1.
- the invention also relates to a shell or tubular object to be incorporated in a machine part of a combustion engine, as defined in claim 6.
- Other suitable features are stated in the claims 2-5 and 7, respectively.
- the core body, onto which a first layer is sprayed will be removed before additional material is applied by spraying. It is particularly suitable to make the core body of molding sand which can loose its form stability and be discharged from the tube or shell, e. g. upon heating. Without risk of cracking due to tensions, which would unavoidably arise if the core body were to remain, continuous spraying may thereafter be effected up to a desired thickness.
- the thermal spraying of the additional layer should be controlled in such a way that the second or third layer contains more oxides and/or pores than the first layer, whereby the desired qualities, especially a lower thermal conductivity, are obtained in the second or third layer.
- a relatively thin layer either as a second layer between a first and a third layer or as a third layer sprayed onto the second layer.
- such a relatively thin layer may e. g. be used as a diffusion barrier for carbon or nickel. Also, it can be used to increase the mechanical qualities at higher temperatures.
- a core body 1 is made of molding sand and a phenol resin as a binding agent.
- the core body 1 has an external configuration of the tubular object and, in addition thereto, holding portions 1a, 1b at each end for holding the core body.
- the desired object comprises an exhaust channel in a cylinder head of a combustion engine.
- a relatively thin and essentially pore-free layer 2 of a metal alloy containing about 5 % Al, 22 % Cr and the rest mainly Fe (the contents are by weight) is sprayed onto the core body 1.
- Porosity if any, must consist of closed pores.
- the spraying operation is interrupted, whereupon the sand core 1 is removed in that the sand core and the layer sprayed thereon is heated in a furnace at about 600 °C for 2-3 hours, and thereafter the sand is discharged from the tubular metal alloy layer 2.
- a second layer 3 is sprayed onto the first, self-supporting layer 2.
- the first layer is permitted to expand and shrink freely due to variations of temperature, without any risk of tensions and accompanying cracking.
- the thickness of the second layer may be at least 1 mm. The spraying process can be performed without interruption for cooling.
- the first, relatively thin layer 2 is sprayed by means of a wire-fed flame sprayer so as to form a dense layer.
- the layer may be applied by plasma spraying.
- the second layer 3 may preferably be applied by means of a powder-fed flame sprayer in order to obtain a suitable quantity of pores and oxides. In this case, a quantity of 5-25 %, preferably about 15 %, pores and oxides is desired.
- the second layer 3 does not have to be of the same material composition as the first layer 2, but may e. g. consist of another metal alloy of high heat resistance.
- the layer consists of the same material and differs only in porosity and oxide contents.
- a thin third layer may be applied either between or on top of the two above-mentioned layers.
- the third layer may i. a. function as an adhesive layer or diffusion barrier.
- the object and the manufacturing method according to the invention have several advantages.
- the geometric shape as well as the materials and the thickness thereof can be chosen at will.
- very thick layers (the second layer 3) may be applied after the removal of the core body.
- the manufacturing method is relatively quick (metal can be sprayed onto a red hot substrate) and the handling rather simple.
- the cassation is very low because of the eliminated risk of cracking. Even the subsequent operations, e. g. molding, are facilitated and can therefore be performed with great accuracy.
- the recircling of scrap is made easier.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Coating By Spraying Or Casting (AREA)
Description
- The invention relates to a method to manufacture a shell or tubular object to be incorporated in a heat and corrosion resistant part of a combustion engine, as defined in the first part of
claim 1. - The background of the invention is a desire to make it possible to operate internal combustion engines at a higherworking temperature, whereby an increased efficiency and a more complete combustion can be achieved. Thus, it is a well-known problem to accomplish temperature and corrosion resistance of the materials, especially in combustion chambers and exhaust channels, in case the working temperature is to be raised above what is normal in today's engines.
- In fact, ceramic materials are high-temperature and corrosion resistant, but it is complicated and expensive to combine ceramics with other, metallic construction materials, such as iron and nickel alloys. Tensions are caused by different temperature coefficients. Certain ceramics will also be subjected to phase transformations in temperature intervals within or very close to the working temperatures in question. Moreover, the subsequent treatment, e. g. the boring of holes, becomes more difficult, if ceramics are used.
- Furthermore, experiments have been made to coat especially exposed motor parts with plates or surface layers of some kind of heat and corrosion resistant metal alloy, e. g. of a FeCrAI- type, which however causes problems in case inside cavities, in particular of a complicated geometry, are to be coated.
- It has also been suggested (FR-A-2 431 335) to manufacture tubular surface bodies, which have been thermally sprayed in advance, with a remaining mandrel or core. In using this known method, however, only very simple, especially cylindrical or conical tube forms can be used, since it must be possible to take out the mandrel or core after molding.
- Furthermore, the published Swedish Patent Application SE-A-8 300 603-1 discloses a method of manufacturing a machine part, including a heat insulated inlet gas channel, by thermally spraying a very thin first layer, having a thickness of 0.1-0.2 mm, of a soft metal material, such as zinc, tin, lead, copper or aluminium, onto a sand core. A second layer, having a thickness of 0.5-2.5 mm, of a metal material, such as carbon steel, is thermally sprayed onto the first layer, and thereafter a third layer, serving as a heat barrier and consisting of a ceramic material is applied, e. g. by thermal spraying. Then, the sand core with the three layers applied thereon is placed in a mold for molding the machine part in a conventional manner. Upon molding, the sand core is removed, so that the three layers form an internal surface of a channel in the machine part.
- However, in this known methods, there might be a risk of cracking when thermally spraying the various layers having different expansion characteristics. Futhermore in the method disclosed by SE-A-8 300 603-1, the innermost layer, forming the internal surface layer of the machine part, is not corrosion resistant and is not suitable e. g. for exhaust channels. Also, the melting point of the soft metal material is far too low to permit the use in an exhaust channel of a combustion engine. Thus, a typical temperature of the exhaust gases is about 850 °C, whereas the melting point of Zn is about 420 °C.
- The object of the invention is to eliminate the disadvantages and restrictions of the known methods and to enable a simple manufacture of shell or tubular objects, even with a complicated geometry, by thermal spraying of a heat and corrosion resistant metal alloy so as to form a dense, first surface layer and an additional layer serving as a heat barrier, without any risk of cracking during the spraying process. A further object is to enable the molding of such an object into a molded body having one or several channels or cavities constituted by the molded shell or tubular object according to the invention.
- The main object is achieved by a method as defined in the characterizing clause of
claim 1. The invention also relates to a shell or tubular object to be incorporated in a machine part of a combustion engine, as defined in claim 6. Other suitable features are stated in the claims 2-5 and 7, respectively. - Thus, when manufacturing such an object it is essential that the core body, onto which a first layer is sprayed, will be removed before additional material is applied by spraying. It is particularly suitable to make the core body of molding sand which can loose its form stability and be discharged from the tube or shell, e. g. upon heating. Without risk of cracking due to tensions, which would unavoidably arise if the core body were to remain, continuous spraying may thereafter be effected up to a desired thickness.
- The thermal spraying of the additional layer should be controlled in such a way that the second or third layer contains more oxides and/or pores than the first layer, whereby the desired qualities, especially a lower thermal conductivity, are obtained in the second or third layer. Naturally, it is also possible to apply a relatively thin layer, either as a second layer between a first and a third layer or as a third layer sprayed onto the second layer. Preferably, such a relatively thin layer may e. g. be used as a diffusion barrier for carbon or nickel. Also, it can be used to increase the mechanical qualities at higher temperatures.
- The invention will be explained further below with reference to the appended drawings illustrating an embodiment.
- Fig. 1 shows schematically a sand core ;
- Fig. 2 shows said sand core with a first layer sprayed thereupon ;
- Fig. shows the desired tubular object after removing the sand core and spraying a relatively thick second layer onto the first layer.
- Thus, in a way known per se, a
core body 1 is made of molding sand and a phenol resin as a binding agent. As shown in Fig. 1, thecore body 1 has an external configuration of the tubular object and, in addition thereto, holding portions 1a, 1b at each end for holding the core body. In the embodiment, the desired object comprises an exhaust channel in a cylinder head of a combustion engine. - In accordance with Fig. 2, a relatively thin and essentially pore-
free layer 2 of a metal alloy containing about 5 % Al, 22 % Cr and the rest mainly Fe (the contents are by weight) is sprayed onto thecore body 1. Porosity, if any, must consist of closed pores. When the layer thickness is at least 0.5 mm, preferably about 1 mm, the spraying operation is interrupted, whereupon thesand core 1 is removed in that the sand core and the layer sprayed thereon is heated in a furnace at about 600 °C for 2-3 hours, and thereafter the sand is discharged from the tubularmetal alloy layer 2. - Thereafter, a
second layer 3 is sprayed onto the first, self-supportinglayer 2. In absence of a core body, the first layer is permitted to expand and shrink freely due to variations of temperature, without any risk of tensions and accompanying cracking. The thickness of the second layer may be at least 1 mm. The spraying process can be performed without interruption for cooling. - Different methods of spraying are possible. Preferably, the first, relatively
thin layer 2 is sprayed by means of a wire-fed flame sprayer so as to form a dense layer. In case a surface layer of great purity is desired (small quantities of oxides and pores), the layer may be applied by plasma spraying. Thesecond layer 3 may preferably be applied by means of a powder-fed flame sprayer in order to obtain a suitable quantity of pores and oxides. In this case, a quantity of 5-25 %, preferably about 15 %, pores and oxides is desired. However, thesecond layer 3 does not have to be of the same material composition as thefirst layer 2, but may e. g. consist of another metal alloy of high heat resistance. - With regard to the heat tensions which may appear in the material, it is certainly an advantage if the layer consists of the same material and differs only in porosity and oxide contents. Moreover, a thin third layer may be applied either between or on top of the two above-mentioned layers. The third layer may i. a. function as an adhesive layer or diffusion barrier.
- The object and the manufacturing method according to the invention have several advantages. The geometric shape as well as the materials and the thickness thereof can be chosen at will. Thus, very thick layers (the second layer 3) may be applied after the removal of the core body. Moreover, the manufacturing method is relatively quick (metal can be sprayed onto a red hot substrate) and the handling rather simple. The cassation is very low because of the eliminated risk of cracking. Even the subsequent operations, e. g. molding, are facilitated and can therefore be performed with great accuracy. Moreover, by avoiding ceramic materials, the recircling of scrap is made easier.
Claims (7)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE8500473 | 1985-02-01 | ||
SE8500473A SE452859B (en) | 1985-02-01 | 1985-02-01 | SHALL OR ROD-FORMED FORM, IN PARTICULAR WITH COMPLIED FORM, WHICH FORMULA IS PROVIDED FOR NOT TO BE IN A MACHINE, EXCEPT A COMBUSTION ENGINE, AND SET TO MAKE THE FORMAL |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0191008A1 EP0191008A1 (en) | 1986-08-13 |
EP0191008B1 true EP0191008B1 (en) | 1989-03-15 |
Family
ID=20358978
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19860850030 Expired EP0191008B1 (en) | 1985-02-01 | 1986-01-31 | Shell or tubular object and method to manufacture the same |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0191008B1 (en) |
DE (1) | DE3662340D1 (en) |
SE (1) | SE452859B (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20240091849A1 (en) * | 2022-09-21 | 2024-03-21 | The Boeing Company | Additively manufactured channels for mold die castings |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB9210763D0 (en) * | 1992-05-20 | 1992-07-08 | Lucas Ind Plc | Improvements in and relating to thixoformable layered materials and articles made from them |
US6250362B1 (en) | 1998-03-02 | 2001-06-26 | Alcoa Inc. | Method and apparatus for producing a porous metal via spray casting |
AUPP939099A0 (en) * | 1999-03-23 | 1999-04-15 | Cast Centre Pty Ltd | Die coatings for gravity and low pressure diecasting |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2431335A1 (en) * | 1978-07-21 | 1980-02-15 | Peugeot | Coating of internal cavities in castings - esp. to provide thermal insulation preventing the cooling of exhaust gas in cylinder heads on IC engines |
-
1985
- 1985-02-01 SE SE8500473A patent/SE452859B/en not_active IP Right Cessation
-
1986
- 1986-01-31 DE DE8686850030T patent/DE3662340D1/en not_active Expired
- 1986-01-31 EP EP19860850030 patent/EP0191008B1/en not_active Expired
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20240091849A1 (en) * | 2022-09-21 | 2024-03-21 | The Boeing Company | Additively manufactured channels for mold die castings |
Also Published As
Publication number | Publication date |
---|---|
SE8500473D0 (en) | 1985-02-01 |
DE3662340D1 (en) | 1989-04-20 |
SE8500473L (en) | 1986-08-02 |
SE452859B (en) | 1987-12-21 |
EP0191008A1 (en) | 1986-08-13 |
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