JP2007064009A - Cylinder head for internal combustion engine and padding method of valve seat to cylinder head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a valve seat having sufficient abrasion resistance by segregating an Fe rich phase in an upper part of a padding layer without forming a fragilely hard Al-Fe-based intermetallic compound in the vicinity of an interface between a Cu rich phase and aluminum alloy of a lower part of the padding layer. <P>SOLUTION: Mixed powder comprises Fe, Cu and a two-phase separate alloy element, and is supplied to the opening end of an intake port and an exhaust port in a cylinder head for an internal combustion engine. The mixed powder is melted by irradiating to the mixed powder with a laser beam by using a semiconductor laser. The valve seat 16 is formed by performing laser padding of copper group alloy powder by solidifying the melted mixed powder. At this time, the mass ratio of the Fe, the Cu and the two-phase separate alloy element in the mixed powder is set so that the Fe is 15 to 85 mass%, and the two-phase separate alloy element is, for example, 0.02 to 2.0 mass% in C and a combination of one kind or two or more kinds among 4 to 30 mass% in Cr, and Cu is a residual part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cylinder head provided with a valve seat that seals an air-fuel mixture or combustion gas when an intake valve or an exhaust valve of an internal combustion engine is seated, and a method for overlaying the valve seat on the cylinder head.

  Conventionally, an aluminum alloy has been used for a cylinder head of an internal combustion engine from the viewpoint of weight reduction and formability. However, during operation of the internal combustion engine, the valve seat provided in the cylinder head is repeatedly seated with the intake valve and the exhaust valve, and is exposed to the heat generated by the explosion of the air-fuel mixture in the combustion chamber. . For this reason, it is practiced to build up another metal having durability in an aluminum alloy (for example, see Patent Document 1).

Specifically, a valve seat made of a clad sheet layer is formed on the cylinder head by overlaying by a laser clad method using a copper alloy having excellent heat resistance, wear resistance and corrosion resistance. The valve seat having this clad sheet layer is welded to the base material (aluminum alloy) of the cylinder head or alloyed with the base material, so that heat conduction from the valve seat to the cylinder head is good. Become. Therefore, it becomes possible to reduce the thermal load of the valve seat and the valve and improve the durability performance.
JP-A-2-196117

  In forming the clad sheet layer as described above, for example, a cladding material containing Fe and Cu alloy elements can be used. When such an alloy is used, an Al-Fe intermetallic compound that is brittle and hard near the interface between the Fe-rich phase and the aluminum alloy when the Fe-rich phase is at the bottom of the overlay layer and the Cu-rich phase is at the top of the overlay layer May cause cracks in the vicinity of this interface. Moreover, when the upper part of the build-up layer is a Cu rich phase, it is inferior to abrasion resistance compared with a Fe rich phase. In order to solve these problems, it is possible to adopt a technique in which a Cu alloy layer is formed on the aluminum alloy surface in advance, and then an Fe alloy layer is formed on the surface of the Cu alloy layer. However, according to such a method, the Cu alloy layer and the Fe alloy layer must be formed by separate processes, resulting in an increase in the manufacturing process of the product, which in turn increases the manufacturing cost. Become.

  For this reason, in order to form the cladding sheet layer as described above, a cladding material made of a mixed powder of various alloy elements constituting a copper base alloy is used, and the cladding material is laid by performing laser irradiation. It is effective to perform laser cladding. That is, a cladding material made of a mixed powder of various alloy elements constituting a copper base alloy is melted by laser irradiation, and the valve seat is built up with the molten copper base alloy powder.

  However, it has been confirmed that the following problems occur when building up by laser irradiation using a clad material made of a mixed powder of various alloy elements constituting such a copper-based alloy. FIG. 5 is a cross-sectional view of a built-up portion when laser cladding is performed using, for example, a powder in which Fe and Cu are mixed at a predetermined ratio as a copper-based alloy powder.

  As shown in FIG. 5, when laser cladding is performed using a powder in which Fe and Cu are mixed, the Fe rich phase J1 is segregated at the lower part of the overlay layer J3 when the powder is melted, and the Cu rich phase J2 segregates in the upper part of the built-up layer J3, and eventually a brittle Al—Fe intermetallic compound J5 is formed in the vicinity of the interface between the Fe rich phase J1 and the aluminum alloy J4, and wear resistance. It has been confirmed that the problem of worsening occurs.

  In view of the above, the present invention provides a cylinder head and a cylinder head provided with a valve seat having sufficient wear resistance without forming a brittle Al-Fe intermetallic compound near the interface between the Cu-rich phase and the aluminum alloy. An object of the present invention is to provide a method for overlaying a valve seat.

  In order to achieve the above object, the present inventors have intensively studied laser cladding using a mixed powder of Fe and Cu alloy elements. As a result, it came to a conclusion that the above phenomenon occurred because the structure of the mixed powder was melted and made into a liquid phase by the Marangoni effect depending on the mixing ratio of Fe and Cu.

  Specifically, the present inventors conducted an experiment of examining the structure when the mixed powder was melted to form a liquid phase. However, in order to realize a two-phase separation structure, it is important to add an alloy element (two-phase separation alloy element) that promotes two-phase separation. This two-phase separation alloy element forms an Fe alloy phase (Fe rich phase), and makes the Fe rich phase easy to be guided to the upper part of the built-up layer. For this reason, this experiment was performed by adding a two-phase separation alloy element such as Cr or C to a mixed powder of alloy elements such as Fe and Cu.

  FIGS. 6A to 6C are diagrams schematically illustrating the state at that time. In the example shown in FIG. 6A, an Fe-rich phase J1 is formed at the center, and the outer periphery is a Cu-rich phase J2 so as to surround the Fe-rich phase J1. In the example shown in FIG. 6 (b), contrary to FIG. 6 (a), a Cu rich phase J2 is formed at the center, and the outer peripheral portion is an Fe rich phase J1 so as to surround the Cu rich phase J2. Yes. In the example shown in FIG. 6C, a triple-structured powder particle in which the Fe-rich phase J1 is disposed around the Cu-rich phase J2 and the Cu-rich phase J2 is disposed so as to surround the Fe-rich phase J1. Yes.

  Each structure shown in these examples is determined by the mixing ratio of Fe and Cu as described above. In order to realize a two-phase separation structure in which the Fe-rich phase J1 is segregated at the upper part of the built-up layer and the Cu-rich phase J2 is segregated at the lower part of the built-up layer, the structure shown in FIG. It is necessary to select the mixing ratio of Fe and Cu so that the Fe rich phase J1 is formed in the center and the outer peripheral portion is the Cu rich phase J2 so as to surround the Fe rich phase J1.

  As a result of investigation, it was found that the structure shown in FIG. 6A is obtained if the mass ratio of each alloy element in the mixed powder of Fe, Cu and the two-phase separation alloy element is as follows.

  (1) Fe: 15 to 85 mass%, (2) Two-phase separation alloy element C: 0.02 to 2.0 mass%, Cr: 4 to 30 mass%, Mo: 2 to 20 mass%, Nb: 2 -20 mass%, V: 4-20 mass%, W: 2-20 mass%, Si: 4-20 mass%, B: 0.2-10 mass%, S: 0.2-10 mass%, Ta : 2 to 20% by mass, Bi: 1 to 20% by mass, Ag: 2 to 20% by mass, Sn: 2 to 20% by mass (however, the two-phase separation alloy element is one of a plurality of materials shown here) (1) or a combination of two or more) (3) Cu: remainder.

  However, when the ratio of the mass of Cu is too large, a tendency to increase blow holes (pores) is observed. Moreover, if the proportion of the mass of Cu is increased and the proportion of the mass of Fe is reduced, the Fe-rich phase J1 is likely to agglomerate at the upper part of the built-up layer when the mixed powder is melted, but the Fe-rich phase J1. In view of wear resistance, the amount of Cu-rich phase J2 surrounding the substrate increases, which is not preferable.

  Conversely, if the proportion of Fe is increased to reduce the proportion of Cu, the wear resistance can be improved, but if the proportion of Fe is too large, it segregates at the bottom of the overlay layer. There is a high possibility that brittle and hard Al—Fe-based intermetallic compound J5 is formed in the vicinity of the interface between the Fe-rich phase and the aluminum alloy.

  In addition, it is considered that it is not preferable that the content of the two-phase separated alloy element is too large in the mixed powder. For example, if the Cr content is too high, embrittlement at high temperatures is a concern, and if the C content is too high, hot cracking due to the austenite structure occurs.

  Therefore, as shown in the chart of FIG. 7 below, the present inventors used a sample in which the mixed mass ratio of each alloy element of the mixed powder composed of Fe, Cr, Cu, and C was changed, and Cu was used. The conditions under which the rich phase J2 can be segregated in the lower part of the built-up layer and the Fe rich phase J1 can be segregated in the upper part of the built-up layer were investigated.

  However, when a large amount of the aluminum alloy as a base material is melted, the brittle Al—Fe intermetallic compound J5 is easily formed. Therefore, laser cladding is performed under the minimum heat input condition capable of forming a bead. In the samples (1) to (3), the laser output P is 1 kW, the welding speed V is 15 mm / s, the heat input to the base material (P / V) is about 6.67 kj / cm, and the sample (4) In (8) to (8), the laser output P is 1.5 kW, the welding speed V is 20 mm / s, and the heat input to the base material (P / V) is 7.5 kj / cm.

  The sample used here is merely an example, and a two-phase separation structure can be obtained if the mass ratio of Fe, Cu, and the two-phase separation alloy element is as described above.

  As can be seen from the above chart, when Cr is 9% by mass, Fe is in the range of 30 to 45% by mass, and when Cr is 18% by mass, when Fe is in the range of 30 to 35% by mass. The Fe-rich phase J1 was segregated at the upper part of the overlay layer.

  Moreover, although the case where Cr was 9 mass% and the case where it was 18 mass% was investigated here, from these results, the more brittle and hard Al—Fe-based intermetallic compound J5 is formed. It turns out that the possibility becomes high. Therefore, in order to reduce the possibility, it is better to reduce Cr mass%, 9 mass% is better than 18 mass%, and if it is 9 mass% or less, Fe mass% is further increased. Even if it becomes, it can be said that the possibility that a brittle and hard Al—Fe intermetallic compound is formed in the vicinity of the interface is reduced.

  Furthermore, the defect rate (interface defect rate) in the vicinity of the interface between the copper alloy and the aluminum alloy was also examined for each sample. The result is shown in FIG.

  FIG. 8 (a) shows the interface defect rate when Cr is 9% by mass, and FIG. 8 (b) shows the interface defect rate when Cr is 18% by mass. In addition, although the interface vicinity defect has a crack and a hole, what added the crack rate and the hole rate is represented as a comprehensive interface defect rate.

  As shown in this figure, among the samples in which Cr was 9% by mass, sample (3) had the largest Fe mass among those in which brittle Al—Fe intermetallic compound J5 was not formed in the vicinity of the interface. %, And the interface defect rate was low. On the other hand, it can be seen that Sample (4) has a high interface defect rate due to the influence of a brittle and hard Al—Fe intermetallic compound in the vicinity of the interface. For this reason, since the total of the mass% of Fe and Cr shown in the sample (3) is 55 mass%, if it is below this value, a two-phase separation structure with a low interface defect rate can be obtained. I can say that.

  Further, as shown in this figure, the interface defect rate is lower when Cr is 9% by mass than when 18% by mass. Also from this result, it can be said that the case where Cr is 9 mass% is more preferable than the case where 18 mass%.

  Subsequently, in order to verify the wear resistance of the built-up layer having the two-phase separation structure formed as described above, a sample (Cu-35Fe-18Cr-0. 4 and Fe-30Cr-0.7C-40Cu), Al alloy itself (A5042), SUS material (SUS304), and practical Cu-based alloy powder (Cu-7.8Fe-19.6Ni-2.7Si-) The build-up layer of 1.3B) was examined for wear resistance and Vickers hardness. The result is shown in FIG.

  As shown in this result, when the two-layer separation structure as described above is configured, the Vickers hardness is low compared with the built-up layer of the Cu-based alloy powder that is practically used, but the specific wear amount is almost the same. Could get. The smaller the specific wear amount, the better the wear resistance. Moreover, although the hardness of the built-up layer having a two-phase separation structure (gradient function) is low, it is put into practical use by segregating on the upper part of the built-up layer of the hard Fe-rich phase {(Fe, Cr alloy phase)] It can be said that it is possible to obtain wear resistance equivalent to that of the Cu-based alloy powder.

  Based on the above, in the invention described in claim 1, the aluminum alloy is used as a base material, the intake port (3) and the exhaust port (4) are formed, and the intake port (3) and the exhaust port ( 4) A cylinder head for an internal combustion engine, in which a valve seat (16) with which an intake valve (5) and an exhaust valve (6) are brought into contact is formed at an opening end on the fuel chamber (2) side in 4). (16) is constituted by build-up of a copper-based alloy powder containing Fe, Cu and a two-phase separation alloy element, and a spherical Fe-rich phase (16a) is formed on the top of the build-up layer, A Cu rich phase (16b) is formed so as to surround the lower part of the overlay layer and the Fe rich phase (16a).

  Thus, when a two-phase separation structure is formed using a mixed powder containing Fe, Cu and a two-phase separation alloy element, a spherical Fe-rich phase (16a) is formed on the top of the built-up layer, and the built-up layer The Cu rich phase (16b) is formed so as to surround the lower portion of the metal and the Fe rich phase (16a). According to such a structure, it becomes possible to obtain good wear resistance by the Fe rich phase (16a) at the upper part of the built-up layer, and an aluminum alloy by the Cu rich phase (16a) at the lower part of the built-up layer. It becomes possible to join with. For this reason, the cylinder head for an internal combustion engine in which a valve seat that is wear resistant and has a good joint capable of suppressing a brittle Al—Fe intermetallic compound near the interface between the copper alloy and the aluminum alloy is formed. It can be.

  For example, as shown in claim 2, the mass ratio of Fe, Cu and the two-phase separation alloy element is 15 to 85 mass% for Fe, and C: 0.02 to 2.0 mass% for the two-phase separation alloy element. Cr: 4-30% by mass, Mo: 2-20% by mass, Nb: 2-20% by mass, V: 4-20% by mass, W: 2-20% by mass, Si: 4-20% by mass, B : 0.2-10 mass%, S: 0.2-10 mass%, Ta: 2-20 mass%, Bi: 1-20 mass%, Ag: 2-20 mass%, Sn: 2-20 mass% Of these, one or a combination of two or more, Cu may be the balance.

  In this case, as shown in claim 3, if the two-phase separation alloy element is Cr and the mass ratio of Cr + Fe is 55% by mass or less, the mass ratio of Fe can be increased as compared with other cases. More wear resistance can be obtained.

  The invention described in claims 4 to 7 relates to the manufacturing method of the invention described in claims 1 to 3.

  In the invention described in claim 4, the mixed powder containing Fe, Cu and the two-phase separation alloy element is supplied to the open ends of the intake port (3) and the exhaust port (4) in the cylinder head (1) for the internal combustion engine. A step of irradiating the mixed powder with laser light using a semiconductor laser (20), and melting the mixed powder; and solidifying the molten mixed powder to cause a laser of the copper-based alloy powder. And a step of forming a valve seat (16), and the mass ratio of the mixed powder is as shown in claim 2.

  In this way, when the mixed powder is melted into a liquid phase by the semiconductor laser with respect to the mixed powder having the mass ratio shown in claim 2, during solidification until the liquid powder changes to the solid phase, The Fe-rich phase (16a) is attracted by receiving a force (cohesive force) that tends to aggregate in the opposite direction to the temperature gradient, that is, in the center. Thereby, a built-up layer in which the Fe rich phase (16a) segregates in the upper part and the Cu rich phase (16b) segregates in the lower part is formed, and the valve seat (16) according to claim 1 can be configured. It becomes.

  The invention described in claim 7 is characterized in that the laser output (P) is 1 kW and the welding speed (V) is 15 mm / s.

  As a result, a large amount of the aluminum alloy serving as the base material can be prevented from being melted. For this reason, it can suppress that a brittle Al-Fe type intermetallic compound is formed in the interface vicinity.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a cylinder head 1 in a multi-cylinder (four-cylinder) internal combustion engine provided with a valve seat to which an embodiment of the present invention is applied. FIG. 2 is a partially enlarged view of the cylinder head 1 shown in FIG. Hereinafter, the configuration of the cylinder head 1 provided with the valve seat will be described with reference to these drawings.

  The cylinder head 1 is made of an aluminum alloy, and a number of combustion chambers 2 corresponding to the number of cylinders are formed below the cylinder head 1. The cylinder head 1 has two intake ports 3 and two exhaust ports 4 for each cylinder.

  The intake port 3 extends from one side surface (the right side surface in FIG. 1) of the cylinder head 1 toward the combustion chamber 2 and communicates with the combustion chamber 2. The intake port 3 is opened and closed by an intake valve 5 attached to the cylinder head 1.

  The exhaust port 4 extends from the other side surface (left side surface in FIG. 1) of the cylinder head 1 toward the combustion chamber 2 and communicates with the combustion chamber 2. The exhaust port 4 is opened and closed by an exhaust valve 6 attached to the cylinder head 1.

  Above the cylinder head 1, an intake side camshaft 7 and an exhaust side camshaft 8 are provided. Each of the intake side camshaft 7 and the exhaust side camshaft 8 extends in the direction perpendicular to the sheet of FIG. 1 as a longitudinal direction, and is configured to be rotatable. Both camshafts 7 and 8 are integrally formed with cams 7a and 8a that perform eccentric rotation. A guide hole 9 is provided directly below the cams 7a and 8a in the cylinder head 1, and a valve lifter 11 is slidably inserted therein.

  An adjusting shim 12 is fitted on the upper surface of the valve lifter 11, and the cams 7a, 8a are in contact with the upper surface thereof.

  An intake valve 5 and an exhaust valve 6 are slidably inserted into the cylinder head 1, and the upper ends of the valve stems 5 a and 6 a are in contact with the lower surface of the valve lifter 11. A retainer 14 is fitted on the upper ends of the valve stems 5a and 6a via a cotter 13.

  A coiled valve spring 15 is interposed between the lower surface of the retainer 14 and the inner bottom surface 1a of the cylinder head 1 in a compressed state. The valve spring 15 always urges the intake valve 5 and the exhaust valve 6 upward. This biasing direction is a direction in which the intake port 3 and the exhaust port 4 are closed. On the other hand, the upper ends of the valve stems 5 a and 6 a are in contact with the lower surface of the valve lifter 11. Therefore, when both camshafts 7 and 8 rotate and the cams 7a and 8a periodically depress the valve lifter 11 against the urging force of the valve spring 15, the valve lifter 11 presses the intake valve 5 and the exhaust valve 6 downward. To open and close.

  When the intake port 3 is opened by the downward movement of the intake valve 5, the air-fuel mixture composed of intake air and fuel is guided to the combustion chamber 2 through the intake port 3 as indicated by arrows. This air-fuel mixture is exploded and burned in the combustion chamber 2 to become combustion gas. The combustion gas is discharged from the exhaust port 4 to the outside when the exhaust valve 6 moves down and the exhaust port 4 is opened.

  In the cylinder head 1, a valve seat 16 is provided at the combustion chamber side opening end of the intake port 3 and the combustion chamber side opening end of the exhaust port 4. These valve seats 16 are provided to ensure sealing properties when the intake valve 5 closes the intake port 3 or when the exhaust valve 6 closes the exhaust port 4. In addition, the valve seat 16 has a function of releasing the heat of the intake valve 5 and the exhaust valve 6 and the heat of the wall surface of the combustion chamber 2 to the cooling water as the cooling liquid. As shown in FIG. 2, the valve seat 16 is formed on the entire outer periphery of the end portions of the intake port 3 and the exhaust port 4 so as to be in contact with the entire outer periphery of the intake valve 5 and the exhaust valve 6. .

  FIG. 3 is a cross-sectional view when a part of the valve seat 16 is cut along the longitudinal direction of the intake valve 5 or the exhaust valve 6.

  As shown in FIG. 3, the valve seat 16 has a height of the built-up layer of the copper-based alloy powder of about 1.5 mm. The copper-based alloy powder constituting the valve seat 16 includes Cu, Fe, Cr, and C, and has a composition ratio of Cu30Fe9Cr0.2C, for example. The valve seat 16 has a structure (two-phase separation structure) in which the two phases of the Fe-rich phase 16a and the Cu-rich phase 16b are separated. Specifically, the upper part of the built-up layer is mainly composed of the Fe-rich phase 16a, and the lower part of the built-up layer is mainly composed of the Cu-rich phase 16b, and the Fe-rich phase 16a becomes spherical and is surrounded by the Cu-rich phase 16b. It is in the state.

  In the valve seat 16 having such a structure, the wear resistance can be ensured by the Fe rich phase 16a segregated on the upper part of the built-up layer. Further, since the Cu rich phase 16b segregating at the lower part of the build-up layer is formed at the interface between the valve seat 16 and the aluminum alloy constituting the cylinder head 1, a brittle Al—Fe intermetallic compound is formed. Compared with the case where it did, it becomes a structure where a crack is hard to generate | occur | produce in the valve seat 16 at this interface.

  Next, a method for manufacturing the valve seat 16 in the cylinder head 1 configured as described above, that is, a method for overlaying the cylinder head 1 will be described. FIG. 4 shows a layout in which the cylinder head 1 is built using a build-up device, and this will be described with reference to this figure.

  As shown in FIG. 4, the build-up apparatus includes a semiconductor laser 20, a rotary table 21, a shield gas supply device 22, a mixed powder supply device 23, and a control device 24. A build-up apparatus using such a semiconductor laser 20 is used.

  First, the mixed powder supply apparatus 23 forms a mixed powder in which Fe, Cu, Cr, and C are mixed at a predetermined mass ratio. Specifically, mixed powder is formed by mixing each powder with the mixer 23a. At this time, regarding mass ratio of each alloy element which comprises mixed powder, Cr is 9 mass%, Fe is 30-45 mass%, C is 0.2-0.4 mass%, and the remainder is Cu.

  And the mixed powder produced | generated is supplied to the site | part which wants to build up as the valve seat 16, ie, the opening end by the side of the combustion chamber 2 of the intake port 3 and the exhaust port 4, through the powder supply nozzle 23b. For example, the supply nozzle 23b having a diameter of 2 mm is inclined 45 degrees with respect to the opening end of the intake port 3 and the exhaust port 4 on the combustion chamber 2 side, and the mixed powder is supplied in a state separated from the opening end by about 5 mm.

  Further, laser light is emitted from the semiconductor laser 20 through the lens 20a based on power supply from the control unit, and the laser light is irradiated to a place where the cylinder head 1 is desired to be built up. Shield gas is supplied to the irradiation area. As a result, the overlay metal is protected from the atmosphere by the shielding gas, and porosity and oxidation can be prevented.

  During the build-up, the composition ratio of the alloy elements constituting the mixed powder is as described above, so the Fe-rich phase 16a is opposite to the temperature gradient during solidification until it changes from the liquid phase to the solid phase. It is attracted in the direction, that is, the force (cohesive force) that tends to aggregate in the center. Although the details of this cohesive force are not clear, it is considered to be caused by the liquid movement phenomenon due to the Marangoni effect. As a result, as shown in FIG. 3, the Fe rich phase 16a is deposited on the upper portion, and the Cu rich phase 16b is formed. A build-up layer that deposits at the bottom is formed.

  Then, the rotary table 21 is rotated by the control unit, whereby the cylinder head 1 is centered on the end of the intake port 3 and the exhaust port 4 on the combustion chamber 2 side, that is, the center line of the portion forming the valve seat 16. To adjust the irradiation time of the laser beam at each location.

  As a result, a high quality built-up layer with low strain, low stress and low dilution rate is obtained, and the valve seat 16 is formed. At this time, for example, the output P of the semiconductor laser 20 is 1.5 kW, and the relative welding peripheral speed V of the semiconductor laser 20 by rotating the turntable 21 is a minimum heat input condition that forms a bead of 20 mm / s. If laser cladding is performed, a large amount of the aluminum alloy serving as a base material can be prevented from being melted. For this reason, it can suppress that a brittle Al-Fe type intermetallic compound is formed in the interface vicinity.

  As described above, when the valve seat 16 is formed using the overlay apparatus shown in FIG. 4, the cross-sectional structure thereof is as shown in FIG. 3, and the upper part of the overlay layer is Fe rich phase 16a and the lower part is Cu rich phase. The two-phase separation structure becomes 16b, and a brittle Al—Fe intermetallic compound is not formed in the vicinity of the interface.

  As a result, a brittle Al-Fe intermetallic compound is not formed in the vicinity of the interface of the build-up layer using the mixed powder containing the binary phase separation alloy element in the Fe, Cu binary alloy, and wear resistance is improved. Can be a sufficient valve seat.

(Other embodiments)
In the said embodiment, although the example of the mixed powder which made the Fe and Cu binary element contain the two-phase-separation alloy element was given, it should just be comprised with the thing of the composition of following (1)-(3). .

  (1) Fe: 15 to 85 mass%, (2) Two-phase separation alloy element C: 0.02 to 2.0 mass%, Cr: 4 to 30 mass%, Mo: 2 to 20 mass%, Nb: 2 -20 mass%, V: 4-20 mass%, W: 2-20 mass%, Si: 4-20 mass%, B: 0.2-10 mass%, S: 0.2-10 mass%, Ta : 2 to 20% by mass, Bi: 1 to 20% by mass, Ag: 2 to 20% by mass, Sn: 2 to 20% by mass (however, the two-phase separation alloy element is one of a plurality of types shown here) Or a combination of two or more) (3) Cu: remaining.

  In particular, it can be said that when the total mass% of Fe and Cr is 55 mass% or less, a two-phase separation structure with a low interface defect rate can be obtained.

Moreover, in the said embodiment, although Cr and C were contained in the mixed powder as a two-phase separation alloy element, it is also possible to add a flux such as CaF ₂ . As described above, when the valve seat 16 is built up on a base material made of an aluminum alloy, pores due to hydrogen are likely to be generated. However, when flux is added in this way, the build-up metal is formed by the following chemical reaction. Hydrogen in the inside can be removed, and generation of pores can be suppressed.

(Chemical formula 1)
CaF ₂ + 2H ⁺ + O ⁻ = CaO + 2HF ↑
In the above embodiment, as the copper-based alloy powder, the one containing mainly Fe with respect to Cu was mentioned, but the same applies to the one containing mainly Cr or Co. This problem can occur. For this reason, it is possible to apply this invention also when using these copper alloys.

  For example, when using a copper alloy mainly containing Cr with respect to a Cu-based alloy powder, the following compositions (1) to (3) are used as a mixed powder containing Cr and Cu containing a two-phase separation alloy element. It only has to be made up of things.

  (1) Cr: 15 to 85% by mass, (2) Two-phase separation alloy element C: 0.02 to 2.0% by mass, Fe: 4 to 20% by mass, Mo: 2 to 20% by mass, Nb: 2 -20 mass%, V: 4-20 mass%, W: 2-20 mass%, Si: 4-20 mass%, B: 0.2-10 mass%, S: 0.2-10 mass%, Ta : 2 to 20% by mass, Ag: 2 to 20% by mass, Sn: 2 to 20% by mass, Co: 2 to 20% by mass (however, the two-phase separation alloy element is one of a plurality of types shown here) Or a combination of two or more) (3) Cu: remaining.

  Further, when Co is mainly contained in the Cu-based alloy powder, it is composed of the following compositions (1) to (3) as a mixed powder in which Co and Cu contain a two-phase separation alloy element. It only has to be done.

  (1) Co: 15 to 85% by mass, (2) Two-phase separation alloy element C: 0.02 to 2.0% by mass, Fe: 4 to 20% by mass, Mo: 2 to 20% by mass, Nb: 2 -20 mass%, V: 4-20 mass%, W: 2-20 mass%, Si: 4-20 mass%, B: 0.2-10 mass%, S: 0.2-10 mass%, Ta : 2 to 20% by mass, Ag: 2 to 20% by mass, Sn: 2 to 20% by mass, Cr: 2 to 20% by mass (however, the two-phase separation alloy element is one of the plural types shown here) Or a combination of two or more) (3) Cu: remaining.

1 is a cross-sectional view of a cylinder head 1 of a multi-cylinder (four-cylinder) internal combustion engine provided with a valve seat in a first embodiment of the present invention. It is the elements on larger scale when it sees from the arrow A direction in the cylinder head 1 shown in FIG. FIG. 4 is a cross-sectional view when a part of the valve seat 16 is cut along the longitudinal direction of the intake valve 5 or the exhaust valve 6. It is the schematic diagram which showed a mode that the overlaying to the cylinder head 1 was performed using the overlaying apparatus. It is sectional drawing of the build-up part at the time of performing laser cladding using the powder which mixed Fe and Cu in the predetermined ratio as copper base alloy powder. It is sectional drawing of a built-up layer when a two-phase-separation alloy element, for example, Cr and C, is added to the mixed powder of Fe and Cu, and a built-up layer is formed. It is the table | surface which described the list of the sample which changed the mixing mass ratio of each alloy of the mixed powder comprised by Fe, Cr, Cu, and C. It is the figure which showed the defect rate (interface defect rate) in the interface vicinity of the overlaying to the aluminum alloy using copper base alloy powder. It is a graph which shows the result of having investigated abrasion resistance and Vickers hardness.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cylinder head, 1a ... Inner bottom surface, 2 ... Combustion chamber, 3 ... Intake port, 4 ... Exhaust port, 5 ... Intake valve, 16 ... Exhaust valve, 16 ... Valve seat, 16a ... Fe rich phase, 16b ... Cu rich Phase: 20 ... Semiconductor laser, 21 ... Rotary table, 22 ... Shielding gas supply device, 23 ... Mixed powder supply device, 24 ... Control device.

Claims (7)

An intake port (3) and an exhaust port (4) are formed using an aluminum alloy as a base material, and at the opening end of the intake port (3) and the exhaust port (4) on the fuel chamber (2) side. A cylinder head for an internal combustion engine in which a valve seat (16) with which an intake valve (5) and an exhaust valve (6) are in contact is formed,
The valve seat (16) is constituted by a build-up layer of copper-based alloy powder containing Fe, Cu and a two-phase separation alloy element, and a spherical Fe-rich phase (16a) is formed on the build-up layer. And an internal combustion layer characterized in that the Cu rich phase (16b) is a functionally graded layer formed by a single laser process so as to surround the lower part of the buildup layer and the Fe rich phase (16a). Cylinder head for engine. The mass ratio of the Fe, Cu and the two-phase separation alloy element is 15 to 85 mass% for the Fe, C: 0.02 to 2.0 mass% for the two-phase separation alloy element, and 4 to 30 mass% for Cr. , Mo: 2 to 20% by mass, Nb: 2 to 20% by mass, V: 4 to 20% by mass, W: 2 to 20% by mass, Si: 4 to 20% by mass, B: 0.2 to 10% by mass , S: 0.2 to 10% by mass, Ta: 2 to 20% by mass, Bi: 1 to 20% by mass, Ag: 2 to 20% by mass, Sn: 2 to 20% by mass or two types 2. The cylinder head for an internal combustion engine according to claim 1, wherein the remaining portion is Cu in combination. The cylinder head for an internal combustion engine according to claim 2, wherein the two-phase separation alloy element is Cr, and the mass ratio of Cr + Fe is 55 mass% or less. An intake port (3) and an exhaust port (4) are formed using an aluminum alloy as a base material, and at the opening end of the intake port (3) and the exhaust port (4) on the fuel chamber (2) side. A method for building up the valve seat (16) on a cylinder head (1) for an internal combustion engine in which a valve seat (16) against which an intake valve (5) and an exhaust valve (6) are in contact is formed,
Supplying an overlaying mixed powder containing Fe, Cu and a two-phase separation alloy element to the open ends of the intake port (3) and the exhaust port (4) in the cylinder head (1) for the internal combustion engine;
Melting the mixed powder by irradiating laser light while supplying the mixed powder using a semiconductor laser (20);
Forming the valve seat (16) by overlaying a copper-based alloy powder by solidifying the molten mixed powder,
The mixed powder has a mass ratio of 15 to 85 mass% for the Fe group, C: 0.02 to 2.0 mass% for the two-phase separation alloy element, 4 to 30 mass% for Cr, and 2 to 20 mass for Mo. % By mass, Nb: 2-20% by mass, V: 4-20% by mass, W: 2-20% by mass, Si: 4-20% by mass, B: 0.2-10% by mass, S: 0.2 10% by mass, Ta: 2-20% by mass, Bi: 1-20% by mass, Ag: 2-20% by mass, Sn: 2-20% by mass, or a combination of two or more, Cu A method for overlaying a valve seat on a cylinder head for an internal combustion engine, wherein the remaining portion is a remaining portion. 5. The method of building a valve seat on a cylinder head for an internal combustion engine according to claim 4, wherein Cr is used as the two-phase separation alloy element, and the mass ratio of Cr + Fe is 55% by weight or less. 6. The method of building a valve seat on a cylinder head for an internal combustion engine according to claim 5, wherein the Cr is a mass ratio of 9% by mass or less and the Fe group is a mass ratio of 45% by mass or less. The method of building a valve seat on a cylinder head for an internal combustion engine according to claim 6, wherein the laser output (P) is 1 kW and the welding speed (V) is 15 mm / s.

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