JP5147025B2 - Iron-based preform and journal structure for forming metal matrix composites - Google Patents

Description

  The present invention relates to an iron-based preform and journal for forming a metal-based composite material, which is excellent in castability with an aluminum-based alloy used for forming a metal matrix composite (hereinafter referred to as MMC). Regarding the part structure.

Conventionally, for example, in a vehicle engine, a cylinder block in which an aluminum alloy is cast is widely used in order to reduce weight. In such an engine, a journal part is formed in a cylinder block made of an aluminum-based alloy (thermal expansion coefficient: about 21.0 × 10 ⁻⁶ / ° C.), and a bearing metal is interposed in the journal part to make an iron-based material. If the crankshaft (coefficient of thermal expansion: 9 × 10 ^{−6 to} 12 × 10 ⁻⁶ / ° C.) is supported, the heat generated by the combustion of the air-fuel mixture in the cylinder is transmitted to the journal when the engine is operating. The clearance between the bearing surface of the journal part where the bearing metal intervenes and the crankshaft is excessive due to the difference in the thermal expansion coefficient between the crankshaft made of iron-based material and the base material made of aluminum-based alloy due to the rise in the temperature of the part As a result, vibration and noise are generated when the vehicle travels.

  Therefore, for example, in a journal portion that supports a crankshaft of a horizontally opposed four-cylinder engine, a journal having a bearing surface in which a central portion is recessed in a semicircular arc shape on each of left and right cylinder blocks made of an aluminum alloy. To change the aluminum alloy of the cylinder block that becomes the base material by casting the iron preform made of iron-based powder sintered body into the part and casting the iron-based preform into MMC. The thermal expansion coefficient necessary for the journal portion is obtained.

  However, when part or all of the base material of the aluminum-based alloy is made into MMC, generally a casting method, particularly a high-speed / high-pressure casting method (High Pressure Die Casting: hereinafter referred to as HPDC) is used. Thus, it is extremely difficult to ensure the adhesion strength at the interface and to ensure stable adhesion by easily infiltrating the aluminum-based alloy into the preform made of the iron-based powder sintered body. It is also known that when a preform made of an iron-based powder sintered body is cast with an aluminum-based alloy, the infiltration state of the molten aluminum-based alloy after casting is greatly affected by mechanical and physical properties. In many cases, the casting conditions are limited to reduce such influence.

  On the other hand, the preform structure made of the iron-based powder sintered body is made into a structure in which the free Cu phase is dispersed in the base, and further subjected to shot blast treatment or further steam treatment, and the surface roughness of the preform is within a specific roughness range. As a result, the wettability between the preform made of the iron-based powder sintered body and the molten aluminum alloy is improved, and the castability of the aluminum-based alloy is improved. It is known that the bonding strength with the preform is improved (see, for example, Patent Document 1).

JP 2004-204298 A

  According to Patent Document 1, Cu is dissolved to increase the strength of a preform made of an iron-based powder sintered material, and is precipitated in a matrix as a free Cu phase, and the preform is cast with an aluminum-based alloy. At this time, the bonding strength at the interface can be increased by reacting with the aluminum-based alloy.

  However, when casting with an aluminum alloy, the aluminum alloy melt that casts the preform before the interface between the preform and the base metal reaches a certain bonding strength due to the shape and specifications of the preform. When stress generated during solidification and shrinkage is applied, adhesion at the interface becomes unstable, and there is a concern that a gap is generated at the interface and bonding strength becomes unstable. Phenomena such as instability of bonding strength at these interfaces and generation of gaps are remarkable when rapid solidification is involved as in HPDC.

  If there is a gap at the interface between the preform made of an aluminum-based alloy and the preform in the journal part, the heat conduction efficiency between the preform and the preform will decrease, and the thermal conductivity will vary in the circumferential direction of the journal part. Occur. Due to this variation, the journal portion does not expand evenly, the support of the bearing metal by the bearing surface of the journal portion becomes unstable, and the coefficient of friction between the crankshaft and the bearing metal increases. Due to the increase in the friction coefficient, that is, the increase in frictional resistance, the wear of the bearing metal becomes intense, which causes a decrease in engine fuel consumption, performance, durability, and the like.

  Furthermore, if there is a gap at the interface between the preform and the base material in the journal part, when the bearing surface of the journal part is machined, the thin part is elastically deformed by the load during processing and the journal part The machining accuracy is reduced.

  Also, if there is a gap at the interface, stress concentration due to high load occurs due to the difference in residual stress and thermal expansion that occurs during solidification and shrinkage of the molten aluminum alloy that casts the preform made of iron-based powder sintered body, and aluminum A system alloy part, ie, a base material, may be damaged.

  Accordingly, a first object of the present invention made in view of such points is to provide an iron-based preform for forming a metal matrix composite that is excellent in castability by an aluminum-based alloy and can ensure stable interfacial bonding strength and adhesion. There is. A second object is to provide a journal structure having this iron-based preform.

  The invention of the iron-based preform for forming a metal matrix composite material according to claim 1, which achieves the first object, is an aluminum having a concave surface continuously formed along a central axis extending direction and having a semicircular cross section. A metal base comprising a preform body casted with a base alloy base material and having a semicircular arc or U-shaped cross section along the concave surface and having an inner circumferential surface and an outer circumferential surface continuous along the central axis extending direction In the iron-based preform for forming a composite material, the preform body has a through-hole communicating with the inner peripheral surface and the outer peripheral surface, and a surface area enlargement process is performed on the inner surface of the through-hole. Features.

  According to the invention of claim 1, in the casting process, by forming a through-hole that communicates the inner peripheral surface and the outer peripheral surface in the preform main body and subjecting the inner surface of the through-hole to a surface area expansion process, The molten aluminum alloy poured on the outer surface of the iron-based preform penetrates the inner surface along the surface of the iron-based preform, and is supplied from the outer surface to the inner surface via a through hole. As a result, good hot water circulation is obtained. Also, contraction stress acts along the inner peripheral surface during solidification and contraction of the molten aluminum alloy poured between the semicircular arc-shaped concave surface and the inner peripheral surface of the iron-based preform, and on the outer peripheral surface side. Aluminum-based alloy that penetrated into the inner surface by increasing the inner surface area of the through-hole by surface area expansion treatment when shrinkage stress was applied along the outer peripheral surface due to solidification and shrinkage of the poured aluminum-based alloy molten metal The drag due to shrinkage stress due to solidification and shrinkage of the molten metal is increased and the shrinkage stress along the inner and outer peripheral surfaces is dispersed and received, and the movement of the molten aluminum alloy is suppressed and the inner and outer peripheral surfaces are in close contact with each other. Thus, the residual stress generated in the base material after shrinkage is relieved.

  Furthermore, with the suppression of the movement of the molten aluminum alloy during solidification and shrinkage of the molten aluminum alloy, it is possible to prevent the formation of a gap at the interface between the base metal and the iron-based preform, and to ensure stable interfacial bonding strength and adhesion. it can.

  According to a second aspect of the present invention, in the iron-based preform for forming a metal matrix composite according to the first aspect, a bottomed hole that opens to the inner peripheral surface and / or the outer peripheral surface of the preform body is formed. It is characterized by that.

  According to the invention of claim 2, the shrinkage stress due to the solidification and shrinkage of the molten aluminum alloy infiltrated into the bottomed hole by drilling the bottomed hole opened in the inner peripheral surface and / or outer peripheral surface of the preform body. Due to the drag force, the shrinkage stress acting along the inner and outer peripheral surfaces is dispersed and received, and the movement of the aluminum alloy molten metal is suppressed and adheres to the inner and outer peripheral surfaces. The resulting residual stress is alleviated. The bottomed hole has less restrictions on the drilling than the through hole, and the bottomed hole can be drilled even at a site where the drilling of the through hole is restricted.

  According to a third aspect of the present invention, in the iron-based preform for forming a metal matrix composite according to the second aspect, a surface area enlargement process is performed on the inner surface of the bottomed hole.

  According to the third aspect of the present invention, the inner surface of the bottomed hole is increased in surface area by a surface area expansion process, and due to the shrinkage stress caused by the solidification and shrinkage of the molten aluminum-based alloy that has entered the bottomed hole. Drag increases.

  The invention of the iron-based preform for forming a metal matrix composite according to claim 4 is casted with an aluminum-based alloy base material having a semicircular cross section and having a concave surface continuously formed along the direction in which the central axis extends. An iron-based preform for forming a metal matrix composite comprising a preform body having a semicircular arc or a U-shaped cross section along the concave surface and having an inner peripheral surface and an outer peripheral surface that are continuous along the extending direction of the central axis. The preform body is characterized in that a bottomed hole that opens to the inner peripheral surface and / or the outer peripheral surface is formed, and a surface area enlargement process is performed on the inner surface of the bottomed hole.

  According to the fourth aspect of the present invention, the shrinkage stress due to solidification and shrinkage of the molten aluminum-based alloy that has been subjected to surface area expansion treatment on the inner peripheral surface and / or the inner surface opened to the outer peripheral surface of the preform body and entered the bottomed hole. The drag due to the solidification and shrinkage of the molten aluminum alloy is dispersed and received by the drag caused by the aluminum alloy melt, and the movement along the inner and outer circumferential surfaces of the molten aluminum alloy is suppressed. In addition, it is in close contact with the inner and outer peripheral surfaces, and the residual stress generated in the base material after solidification and shrinkage is relieved. Furthermore, with the suppression of the movement of the molten aluminum alloy during solidification and shrinkage of the molten aluminum alloy, it is possible to prevent the formation of gaps at the interface between the base material and the iron-based preform, and excellent in castability and stable interface bonding. Strength and adhesion can be secured.

  According to a fifth aspect of the present invention, in the iron-based preform for forming a metal matrix composite according to the fourth aspect, the preform body has a through-hole communicating the inner peripheral surface and the outer peripheral surface. It is characterized by that.

  According to the invention of claim 5, the preform body was poured into the outer peripheral surface side of the iron-based preform in the casting step by drilling a through hole that communicates the inner peripheral surface and the outer peripheral surface. The molten aluminum alloy penetrates into the inner peripheral surface side along the surface of the iron-based preform, and is supplied from the outer peripheral surface side to the inner peripheral surface side through the through hole, so that good hot-rollability is obtained. Also, contraction stress acts along the inner peripheral surface during solidification and contraction of the molten aluminum alloy poured between the semicircular arc-shaped concave surface and the inner peripheral surface of the iron-based preform, and on the outer peripheral surface side. When the shrinkage stress acts along the outer peripheral surface due to the solidification and shrinkage of the molten aluminum alloy molten metal, the inner peripheral surface increases due to the drag due to the shrinkage stress due to the solidification and shrinkage of the molten aluminum alloy that has entered the through hole. In addition, the shrinkage stress along the outer peripheral surface is dispersed and received, the movement of the molten aluminum alloy is suppressed, and the residual stress generated in the base material after the shrinkage is relieved by being in close contact with the inner peripheral surface and the outer peripheral surface.

  The invention of the journal part structure according to claim 6, which achieves the second object, is characterized in that the iron-based preform for forming a metal matrix composite according to any one of claims 1 to 5 is replaced with the preform. It is characterized by being cast with an aluminum alloy base material having a semi-circular cross section along the inner peripheral surface of the main body and having a concave bearing surface continuously formed along the direction in which the central axis extends.

  According to claim 6, the iron-based preform is cast with a base material made of an aluminum-based alloy having a concave bearing surface continuously formed in a semicircular cross section along the inner peripheral surface of the iron-based preform. The formed journal part has a smaller difference in thermal expansion coefficient from the shaft of ferrous material, and even if the temperature of the journal part rises, the clearance between the shaft and the bearing surface can be kept within an allowable range. Generation of vibration and noise during rotation can be prevented.

  Furthermore, the occurrence of gaps at the interface on the inner peripheral surface of the iron-based preform is prevented, the heat conduction efficiency between the base material and the iron-based preform is improved, and the thermal conductivity becomes uniform in the circumferential direction of the journal part, The bearing surface side of the journal portion is evenly expanded to ensure roundness. As a result, an increase in the coefficient of friction with the shaft is suppressed, and the fuel consumption, performance, durability, and the like of the engine can be ensured as the frictional resistance decreases.

  According to the iron-based preform for forming a metal matrix composite according to the present invention, the preform body is formed by punching a through hole having a surface area expansion treatment on the inner surface communicating the inner peripheral surface and the outer peripheral surface. In the process, the molten aluminum alloy poured on the outer peripheral surface side of the iron-based preform enters the inner peripheral surface side along the surface of the iron-based preform, and also passes through the through hole from the outer peripheral surface side to the inner peripheral surface. It is supplied to the side to obtain good hot water circulation. Also, contraction stress acts along the inner peripheral surface during solidification and contraction of the molten aluminum alloy poured between the semicircular arc-shaped concave surface and the inner peripheral surface of the iron-based preform, and on the outer peripheral surface side. When shrinkage stress is applied along the outer peripheral surface due to solidification and shrinkage of the molten aluminum alloy molten metal, the inner peripheral surface and outer periphery are affected by the drag due to the shrinkage stress due to solidification and shrinkage of the molten aluminum alloy that has penetrated the through hole. The shrinkage stress along the surface is dispersed and received, and the movement of the molten aluminum-based alloy is suppressed and is closely adhered to the inner peripheral surface and the outer peripheral surface, and the residual stress generated in the base material after contraction is relieved.

  In addition, according to the iron-based preform for forming a metal matrix composite of the present invention, an aluminum-based alloy that has been subjected to surface area expansion treatment on the inner peripheral surface and / or inner surface opened to the outer peripheral surface of the preform body and has entered the bottomed hole The shrinkage stress acting along the inner and outer peripheral surfaces due to the solidification and shrinkage of the aluminum alloy melt is dispersed and received by the drag due to the shrinkage stress due to the solidification and shrinkage of the molten metal, and the inner peripheral surface of the aluminum alloy melt and The movement along the outer peripheral surface is suppressed and the inner surface and the outer peripheral surface are in close contact with each other, and the residual stress generated in the base material after solidification and contraction is relieved. Furthermore, with the suppression of the movement of the molten aluminum alloy during solidification and shrinkage of the molten aluminum alloy, it is possible to prevent the formation of gaps at the interface between the base material and the iron-based preform, and excellent in castability and stable interface bonding. Strength and adhesion can be secured.

  According to the journal part structure of the present invention, an iron-based preform is cast with a base material made of an aluminum-based alloy having a concave bearing surface continuously formed in a semicircular arc shape along the inner peripheral surface of the iron-based preform. The enveloped journal part has a smaller difference in thermal expansion coefficient from the shaft made of ferrous material, and the clearance between the shaft and the bearing surface can be kept within an allowable range even when the temperature of the journal part rises. Generation of vibration and noise during rotation of the shaft can be prevented.

  Furthermore, the occurrence of gaps at the interface on the inner peripheral surface of the iron-based preform is prevented, the heat conduction efficiency between the base material and the iron-based preform is improved, and the thermal conductivity becomes uniform in the circumferential direction of the journal part, The bearing surface side of the journal portion is evenly expanded to ensure roundness. As a result, an increase in the coefficient of friction with the shaft is suppressed, and the fuel consumption, performance, durability, and the like of the engine can be ensured as the frictional resistance decreases.

It is a perspective view which shows the outline | summary of the iron-type preform which concerns on 1st Embodiment. It is the II sectional view taken on the line of FIG. It is a longitudinal cross-sectional view of the direction orthogonal to the crankshaft of a cylinder block. FIG. 4 is a view taken in the direction of arrow II in FIG. 3. It is explanatory drawing of a journal part. It is a figure which shows another through-hole, (a) is sectional drawing, (b) is a III arrow directional view of (a). It is a figure which shows another through-hole, (a) is sectional drawing, (b) is IV arrow line view of (a). It is sectional drawing of another iron-type preform. It is sectional drawing of the iron-type preform which concerns on 2nd Embodiment. It is explanatory drawing of a journal part. It is a figure which shows another bottomed hole, (a) is sectional drawing, (b) is a V arrow directional view of (a). It is a figure which shows another bottomed hole, (a) is sectional drawing, (b) is VI arrow directional view of (a).

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an iron-based preform for forming a metal matrix composite and a journal structure having an iron-based preform according to the present invention will be described below. A crank journal portion of a horizontally opposed four-cylinder engine and an iron-based material disposed in the journal portion A preform will be described as an example with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing an outline of an iron-based preform according to the first embodiment, and FIG. 2 is a cross-sectional view taken along the line II of FIG.

An iron-based preform for forming a metal matrix composite (hereinafter referred to as “iron-based preform”) 1 according to the present embodiment includes, for example, iron-based powder, copper powder, graphite powder, lubricant powder, or further After mixing with fine particle powder for improving machinability to make a mixed powder, this mixed powder is charged into a mold and press-molded using a press or the like, and sintered at 1100 to 1250 ° C. It is formed by a powder sintered body. In addition, as for sintering conditions, it is preferable to adjust temperature and time so that the thermal expansion coefficient of the iron-based powder sintered body is 13.5 × 10 ⁻⁶ / ° C. or less.

  As shown in FIGS. 1 and 2, the iron-based preform 1 includes a semicircular arc shape or a U-shaped inner peripheral surface 11 and an outer peripheral surface 12 extending along the central axis L direction, and opposed end surfaces 13. , 14, and flange portions 15, 16 extending in the radial direction are integrally formed at both ends of the preform body 10, respectively, and each flange portion 15, 16 has a communication hole 15 a, 16a is drilled.

  An inner peripheral surface 11 of the preform main body 10 is a substantially semicircular arc shape, a first inner peripheral surface 11a extending along the central axis L direction, and a plane continuously formed at one end of the first inner peripheral surface 11a. A planar third inner peripheral surface 11c and fourth inner peripheral surface 11d that are continuous with the other ends of the second inner peripheral surface 11b, the second inner peripheral surface 11b, and the first inner peripheral surface 11a and that face each other. Have. On the other hand, the outer peripheral surface 12 is a substantially semicircular arc-shaped first outer peripheral surface 12a extending along the central axis L direction, and a planar second outer peripheral surface continuously formed at one end of the first outer peripheral surface 12a. 12b, the second outer peripheral surface 12b, and the first outer peripheral surface 12a, respectively, have a planar third outer peripheral surface 12c and a fourth outer peripheral surface 12d that are continuous with each other and face each other.

  A plurality of through holes that communicate the outer peripheral surface 12 and the inner peripheral surface 11 of the preform body 10 are formed. In the present embodiment, the first through hole 21A having a reference line La orthogonal to the central axis L and communicating between the first inner peripheral surface 11a and the first outer peripheral surface 12a, a reference line parallel to the reference line La. Lb has a second through hole 21B communicating between the second inner peripheral surface 11b and the second outer peripheral surface 12b, a reference line Lc orthogonal to the reference line La, and the third inner peripheral surface 11c and the third The third through hole 21C that communicates between the outer peripheral surfaces 12c and the reference line Ld that is orthogonal to the reference line La, and between the vicinity of the fourth inner peripheral surface 11d of the first inner peripheral surface 11a and the fourth outer peripheral surface 12d. Each through-hole of the 4th through-hole 21D which connects is drilled.

  By forming the first to fourth through holes 21A to 21D, when the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 1 communicate with each other and are cast with an aluminum-based alloy, the hot water circulation is improved. At the same time, the surface area of the iron-based preform 1 is increased to improve the adhesion and bonding strength with the molten aluminum alloy, and the molten aluminum alloy can be easily and stably adhered, and infiltrated in some cases. Thus, the MMC of the iron-based preform 1 can be obtained. These first to fourth through holes 21A to 21D are formed at the time of pressure molding by a mold or at the time of processing a sintered body. Preferably, the molding is performed at the same time as the pressure molding with the mold, so that the production efficiency can be improved and the production cost can be suppressed.

  The first through hole 21A has a cylindrical inner surface that is circular in cross section and continuous in the direction of the reference line La. The inner end 22Aa has an inner end 22Aa that opens to the first inner peripheral surface 11a, and the through hole main body 22A. A tapered hole portion 23A that is continuously formed at the outer end 22Ab and opens to the first outer peripheral surface 12a, and whose inner diameter gradually increases as it moves from the outer end 22Ab side of the through-hole body 22A to the first outer peripheral surface 11a side. have.

  The second through-hole 21B has a cylindrical inner surface that is circular in cross section and continuous in the direction of the reference line Lb, and has a through-hole main body 22B having an inner end 22Ba open to the second inner peripheral surface 11b, and the through-hole main body 22B. A tapered hole portion 23B that is continuously formed at the outer end 22Bb, opens to the second outer peripheral surface 12b, and has an inner diameter that gradually increases from the outer end 22Bb side to the second outer peripheral surface 12b side of the through-hole body 22B. have.

  The third through hole 21C has a cylindrical inner surface that is circular in cross section and continuous in the direction of the reference line Lc, and has an inner end 22Ca that opens to the third inner peripheral surface 11c, and a through hole main body 22C. A tapered hole portion 23C that is continuously formed at the outer end 22Cb, opens to the third outer peripheral surface 12c, and has an inner diameter that gradually increases from the outer end 22Cb side of the through-hole body 22C to the third outer peripheral surface 12c side. have.

  The fourth through hole 21D has a cylindrical inner surface that is circular in cross section and continues in the direction of the reference line Ld, and has an inner end 22Da that opens to the first inner peripheral surface 11a, and a through hole main body 22D. A tapered hole portion 23D that is continuously formed at the outer end 22Db, opens to the fourth outer peripheral surface 12d, and whose inner diameter gradually increases as it moves from the outer end 22Db side of the through-hole body 22D to the fourth outer peripheral surface 12d side. have.

  The shape of each of the through holes 21A to 21D varies depending on the specifications such as the shape of the product to be converted into an MMC. The inner diameter A of each of the through hole bodies 22A to 22D is the thickness of the preform body 10, that is, from the inner peripheral surface 11 to the outer peripheral surface 12. When the thickness of the thin wall portions 38 and 39 (see FIG. 5), which will be described later, formed on the inner peripheral surface 11 side by casting with an aluminum alloy is 0.5 to 9.5 mm ~ 19 mm is preferable (1 mm ≦ A ≦ 19 mm). Further, the interval B between the adjacent through holes 21, that is, the inner end 22Aa of the through hole body 22A of the first through hole 21A on the inner peripheral surface 11 side and the inner end 22Ba of the through hole body 22B of the second through hole 21B. A gap B between the opening centers, an interval B between the opening centers of the inner end 22Ba of the through hole body 22B of the second through hole 21B and the inner end 22Ca of the through hole body 22C of the third through hole 21C, the first through hole The distance B between the opening center of the inner end 22Aa of the through hole body 22A of 21A and the inner end 22Da of the through hole body 22D of the fourth through hole 21D is 1.5 times the inner diameter A of the through hole bodies 22A to 22D. It is formed in a range of 5 to 5 times (1.5A ≦ B ≦ 5A).

  The continuous portions between the inner ends 22Aa to 22Da of the through-hole bodies 22A to 22D opened to the inner peripheral surface 11 and the inner peripheral surface 11 are formed into a smoothly curved surface, so-called R shape or chamfered shape.

  Further, the depth C of the first to fourth through holes 21A to 21D is preferably 0.5 to 5 times (0.5A ≦ C ≦ 5A) the inner diameter A of the through hole bodies 22A to 22D.

  The inner diameter A of the through-hole bodies 22A to 22D of the through-holes 21A to 21D, the intervals B between the adjacent first to fourth through-holes 21A to 21D, and the depths of the first to fourth through-holes 21A to 21D. C and the curved surface shape of the continuous portion between the inner ends 22Aa to 22Da of the through-hole bodies 22A to 22D and the inner peripheral surface 12 are experimentally set in advance in order to optimally set according to specifications such as the product shape to be converted to MMC. It is preferable to determine by the state of adhesion of the interface in the product and the occurrence of cracks on the base material side by simulation.

  This iron-based preform 1 is subjected to shot blasting as necessary, and the surface roughness is 10 to 100 μm in Rz. By performing this shot blast treatment, the oxide film formed on the surface is removed to clean the surface, and the free Cu phase dispersed in the matrix is exposed to the surface. As a result, the wettability of the aluminum-based alloy with the molten metal is improved and the castability of the aluminum-based alloy is improved.

  When the iron-based preform 1 formed in this way is set in a mold and cast with a molten aluminum-based alloy, the aluminum-based alloy is easily and stably adhered to the iron-based preform 1. So that the iron-based preform 1 becomes MMC.

  3 and 4 show an embodiment of a journal portion in which the iron-based preform 1 is used. This embodiment shows a shaft of a horizontally opposed four-cylinder engine, for example, a crank journal portion that supports a crankshaft, and FIG. 3 is a longitudinal sectional view in a direction perpendicular to the crankshaft of the cylinder block. FIG. 4 is a view taken in the direction of arrow II in FIG. 3.

  3 and 4, the left and right cylinder blocks 31 and 32 are separately cast and formed of an aluminum alloy, and the left cylinder block 31 has a bearing surface that is a concave surface formed in a semicircular arc shape at the center. A plurality of left journal portions 33 having 34 are formed, and a plurality of right journal portions 35 having similar bearing surfaces 36 are also formed on the right cylinder block 32.

  The crankshaft 41 is disposed by being sandwiched between the bearing surfaces 34 and 36 of the left and right journal portions 33 and 35 with the halved bearing metals 40a and 40b interposed therebetween, and the journal portions 33 and 35 have a semicircular arc shape. The bearing surfaces 34 and 36 are pivotally supported with bearing metals 40a and 40b interposed therebetween. The crankshaft 41 is made of an iron-based material, and rotates when the reciprocating motion of the piston caused by combustion of the air-fuel mixture in the cylinder is transmitted through the connecting rod. During the rotation, the journal portions 33 and 35 are rotated. A large impact load is always applied, and thermal expansion occurs due to heat propagation due to combustion of the air-fuel mixture.

  In the present embodiment, the iron-based preform 1 having the structure shown in FIGS. 1 and 2 is provided in the left and right journal portions 33 and 35 as MMC. Each of the iron-based preforms 1 is disposed at the position of forming the journal part of the casting mold and formed into an MMC in the casting step when the cylinder blocks 31 and 32 are cast.

  In this casting process, the molten aluminum alloy poured on the outer peripheral surface 12 side of the iron-based preform 1 enters the inner peripheral surface 11 side of the iron-based preform 1 along the surface of the iron-based preform 1. At the same time, even through each of the through holes 21A to 21D, it is supplied to the inner peripheral surface 11 side, and good hot-rollability of the molten aluminum alloy is obtained. Specifically, as shown in FIG. 5, this is about 2-3 mm formed between the semicircular bearing surfaces 34, 36 formed in the journal portions 33, 34 and the inner peripheral surface 11 of the iron-based preform 1. Even in the extremely thin thin portions 38 and 39, good hot water circulation is obtained.

  The inner peripheral surface 11 during solidification and contraction of the molten aluminum alloy poured into the thin wall portions 38 and 39 between the bearing surfaces 34 and 36 of the journal portions 33 and 35 and the inner peripheral surface 11 of the iron-based preform 1. The shrinkage stress σ1 acts in the circumferential direction along the outer circumferential surface 12 and the shrinkage stress σ2 acts along the outer circumferential surface 12 also in the circumferential direction due to solidification and shrinkage of the aluminum alloy poured on the outer circumferential surface 12 side. On the other hand, the shrinkage stresses σ3, σ4, σ5, and σ6 act along the through holes 21A to 21D by the solidification and shrinkage of the molten aluminum alloy that has entered the through holes 21A to 21D of the iron-based preform 1, respectively. .

  Aluminum poured into the thin-walled portions 38 and 39 by the drag due to the shrinkage stresses σ3, σ4, σ5, and σ6 due to solidification and shrinkage of the molten aluminum alloy that has entered the through holes 21A to 21D of the iron-based preform 1 The shrinkage stress σ1 acting in the circumferential direction along the inner peripheral surface 11 during solidification and shrinkage of the molten alloy is dispersed and received. As a result, the movement of the molten aluminum alloy along the inner peripheral surface 11 is suppressed and the aluminum alloy is in close contact with the inner peripheral surface 11, and the residual stress generated in the thin-walled portions 38 and 39 due to the aluminum alloy after shrinkage is reduced and evenly distributed. It is possible to relieve the residual stress of the thin-walled portions 38 and 39 and prevent cracking of the portions.

  Similarly, the outer peripheral surface 12 of the iron-based preform 1 is caused by the drag due to the shrinkage stresses σ3, σ4, σ5, and σ6 due to the solidification and shrinkage of the molten aluminum alloy that has entered the through holes 21A to 21D of the iron-based preform 1. The shrinkage stress σ2 acting along the outer peripheral surface 12 is dispersed and received by the solidification and contraction of the molten aluminum alloy poured on the side, and the movement along the outer peripheral surface 12 of the molten aluminum alloy is suppressed and the outer periphery It is possible to reduce and evenly disperse the residual stress generated in the portion that is in close contact with the surface 12 and contracted.

  Furthermore, with the suppression and close contact of the circumferential movement along the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 1 of the molten aluminum-based alloy during solidification and shrinkage of the molten aluminum alloy, Generation of a gap at the interface with the base material due to the aluminum-based alloy can be prevented, and the interface strength between the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 1 and the base material including the thin portions 38 and 39 can be secured.

  Here, since the iron-based preform 1 is made of an iron-based powder sintered body, the iron-based preform 1 has pores, and the molten aluminum-based alloy is easily and stably adhered to the iron-based preform 1 during casting, and may melt depending on the case. Since the difference between the thermal expansion coefficient of the iron preform 1 soaked into MMC and converted into MMC and the crankshaft 41 made of iron-based material is reduced, the temperature of the journal portions 33 and 35 increases. However, the clearance between the crankshaft 41 and the bearing surfaces 34 and 36 can be within an allowable range, and vibration and noise during rotation of the crankshaft 41 can be prevented.

  Furthermore, by preventing the generation of a gap at the interface between the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 1, and ensuring the interface bonding strength between the inner peripheral surface 11 and the outer peripheral surface 12, the base material and the iron The thermal conductivity efficiency with the system preform 1 is improved, the thermal conductivity becomes uniform in the circumferential direction of the journal portions 33, 35, and the bearing surfaces 34, 36 side of the journal portions 33, 35 are evenly expanded so that the journal Since the support of the bearing metals 40a and 40b by the portions 33 and 35 is stabilized and the increase in the friction coefficient between the crankshaft 41 and the bearing metals 40a and 40b is suppressed, the fuel consumption of the engine is reduced as the frictional resistance is reduced. Performance, durability, etc. can be secured.

  Further, there is no gap in the interface between the thin wall portions 38, 39 and the iron-based preform 1 in the journal portions 33, 35, and the thin wall formed when the bearing surfaces 34, 36 of the journal portions 33, 35 are machined. The deformation of the portions 38 and 39 due to a load during processing is suppressed, and the processing accuracy of the journal portions 33 and 35 is improved.

  Here, when the shrinkage stresses σ3, σ4, σ5, and σ6 in the first to fourth through holes 21A to 21D are too small, the stress σ1 of the thin portions 38 and 39 accompanying the solidification and shrinkage of the molten aluminum-based alloy. As a result, the constraining force against the surface becomes too small, and a continuous gap is formed at the interface between the inner peripheral surface 11 and the base material, and the interface strength becomes unstable. Therefore, in the present embodiment, the through hole bodies 22A to 22D of the first to fourth through holes 21A to 21D perforated in the iron-based preform 1 have a cylindrical inner surface that is continuous in a circular shape with an inner diameter of 1 to 19 mm. However, if the through holes 21A to 21D are formed as tapered holes, it is advantageous for close contact with the interface, but processing of the iron-based preform becomes difficult, resulting in an increase in manufacturing cost and the through holes and the inner peripheral surface. The undercut part is formed in the continuous part and the restraining force against the shrinkage stress σ1 becomes excessive, stress concentration occurs during condensation and shrinkage, and the base material, particularly the thin parts 38 and 39, breaks and cracks occur. Probability increases.

  Further, if the inner diameter A of the through holes 21A to 21D is smaller than 1 mm, the restraining force against the stress σ1 of the thin portions 38 and 39 accompanying the solidification and shrinkage of the molten aluminum alloy becomes insufficient, and the effect of improving the adhesion at the interface. In addition, when shot blasting is performed, it is difficult to spray shots on the inner surface of the through hole well, and the effect of shot blasting cannot be expected.

  On the other hand, if the inner diameter A of the through holes 21A to 21D is larger than 19 mm, there is a concern that the volume of the iron-based preform 1 is reduced and the original functional effect of the preform is reduced, and the first to fourth through holes 21A. The effect of shrinkage due to the solidification of the aluminum-based alloy melt is large in ˜21D, the adhesion to the base material in the first to fourth through holes 21 </ b> A to 21 </ b> D is reduced, and the stress σ <b> 1 of the thin wall portions 38 and 39 is counteracted The restraining force to be used becomes too small, and the interface strength between the inner peripheral surface 11 and the base material becomes unstable.

  The distance B between adjacent through holes 21, that is, the opening center of the inner end 22Aa of the through hole body 22A of the first through hole 21A and the inner end 22Ba of the through hole body 22B of the second through hole 21B on the inner peripheral surface 11 side. The interval B between the opening centers of the inner end 22Ba of the through-hole body 22B of the second through-hole 21B and the inner end 22Ca of the through-hole main body 22C of the third through-hole 21C, and the first through-hole 21A. When the distance B between the opening centers of the inner end 22Aa of the through hole body 22A and the inner end 22Da of the through hole body 22D of the fourth through hole 21D is smaller than 1.5 times the inner diameter A, the iron-based preform 1 is removed. It becomes difficult to press-mold with a mold, and additional machining of each of the first to fourth through holes 21A to 21D by machining or the like causes a significant increase in manufacturing cost and the volume of the iron-based preform 1 is increased. Decrease preform original function Result there is a concern that to decrease. On the other hand, if the interval B between the adjacent through holes 21 exceeds five times the inner diameter A, the possibility that a gap is generated in the portion between the through holes is increased.

  Furthermore, the curved surface of the continuous part of the inner peripheral surface 11 and the inner ends 22Aa to 22Da of the through hole bodies 22A to 22D opened to the inner peripheral surface 11 of the first to fourth through holes 21A to 21D. Alternatively, if the radius of curvature of the chamfered shape is excessive, the interfacial strength and adhesion deteriorate, whereas if it is too small, it becomes difficult to produce the iron-based preform 1 and stress concentration occurs during condensation and contraction of the molten aluminum-based alloy. It generates and breaks and cracks occur in the base material, particularly the thin wall portions 38 and 39.

  Further, when the depth C of the first to fourth through holes 21A to 21D is smaller than 0.5 times the inner diameter A, the molten aluminum alloy in the first to fourth through holes 21A to 21D at the time of casting. However, if it exceeds 5 times the inner diameter A, it becomes difficult to press-mold with the metal mold of the iron-based preform 1, and the first to fourth through holes 21A to 21D are additionally processed by machining or the like. Therefore, it becomes a factor that causes a significant increase in manufacturing cost.

  In addition, the inner surface of the through-hole main bodies 22A to 22D of the first to fourth through-holes 21A to 21D of the iron-based preform 1 is shown in a cross-section in FIG. As shown in FIG. 7, a spiral groove 22c is formed on the inner surface of the through-hole bodies 22A to 22D, or a cross-section is shown in FIG. 7 (a), and the IV arrow view is shown in FIG. By forming a plurality of ribs 22d on the inner surfaces of the hole bodies 22A to 22D, or by forming surface areas on the inner surfaces of the through holes by forming slits or the like, the areas of the inner surfaces of the through hole bodies 22A to 22D are increased. Thus, the drag due to the shrinkage stresses σ3, σ4, σ5, and σ6 due to solidification and shrinkage of the molten aluminum alloy that has entered the through holes 21A to 21D is increased. Thereby, the shrinkage stress σ1 acting along the inner circumferential surface 11 and the shrinkage stress σ2 acting along the outer circumferential surface 12 are more reliably received, and the movement of the molten aluminum alloy along the inner circumferential surface 11 and the outer circumferential surface 12 is performed. It can suppress and improve the contact | adherence effect of the inner peripheral surface 11 and the outer peripheral surface 12, and a base material, and can reduce the residual stress which arises in the base material after shrinkage | contraction.

  8 shows a cross section of the iron-based preform 1 corresponding to FIG. 2, and has a reference line La orthogonal to the central axis L, and between the first inner peripheral surface 11a and the first outer peripheral surface 12a. The first through hole 21A that communicates with the reference line La and the second through hole 21B that communicates between the second inner peripheral surface 11b and the second outer peripheral surface 12b with a reference line Lb parallel to the reference line La, and orthogonal to the reference line La A pair of relatively small-diameter fifth through-holes 21E, sixth through-holes 21F, and reference lines La that have reference lines Le and Lf that communicate with each other between the third inner peripheral surface 11c and the third outer peripheral surface 12c. A relatively small-diameter seventh through-hole 21G that communicates between the vicinity of the fourth inner peripheral surface 11d of the first inner peripheral surface 11a and the fourth outer peripheral surface 12d, and a reference parallel to the reference line Lg. A relatively small eighth through-hole 21H having a line Lh and communicating between the fourth inner peripheral surface 11d and the fourth outer peripheral surface 12d. And a ninth reference line Lj that obliquely intersects the central axis L between the first through hole 21A and the eighth through hole 21H and communicates between the first inner peripheral surface 11a and the first outer peripheral surface 12a. The number, arrangement, size, and the like of the through holes that connect the inner peripheral surface 11 and the outer peripheral surface 12 can be optimally set according to specifications such as the product shape to be converted to MMC, such as through holes 21J. The number, arrangement, size, and the like of these through holes are preferably determined in advance by experiments and simulations based on the state of adhesion of the interface in the product and the occurrence of cracks on the base material side.

(Second Embodiment)
FIG. 9 shows an outline of the iron-based preform 51 according to the second embodiment, and is a cross-sectional view corresponding to FIG. 2 corresponding to those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The iron-based preform 51 according to the present embodiment is formed of the same iron-based powder sintered body as that of the iron-based preform 1.

  As shown in FIG. 9, this iron-based preform 51 is similar to the iron-based preform 1 in that the first inner peripheral surface 11a, the second inner peripheral surface 11b, the third inner peripheral surface 11c, and the fourth inner peripheral surface 11d. A semicircular or U-shaped inner peripheral surface 11 having a cross section and a first outer peripheral surface 12a, a second outer peripheral surface 12b, a third outer peripheral surface 12c, and a fourth outer peripheral surface 12d having a semicircular arc or U-shaped cross section. A preform body 10 having an outer peripheral surface 12 is provided, and flange portions 15 and 16 are integrally formed at both ends of the preform body 10.

  A plurality of through holes communicating with the outer peripheral surface 12 and the inner peripheral surface 11 of the preform main body 10 and a plurality of bottomed holes opening in the outer peripheral surface 12 are formed. These bottomed holes are less restrictive to drilling than through holes, and can be drilled even at sites where drilling of through holes is restricted. In the present embodiment, a first bottomed hole 61A having a reference line La orthogonal to the central axis L and opening in the first outer peripheral surface 12, and a reference line Lb parallel to the reference line La is second. A through hole 65 communicating between the inner peripheral surface 11b and the second outer peripheral surface 12b, a second bottomed hole 61B having a reference line Lc perpendicular to the reference line La and opening to the third outer peripheral surface 12c, a reference line La A third bottomed hole 61C that has a reference line Ld orthogonal to each other and opens in the fourth outer peripheral surface 12d is formed.

  By forming the through-hole 65, when the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 51 communicate with each other through the through-hole 65 and are cast with an aluminum-based alloy, the hot water circulation is improved. By forming the first to third bottomed holes 61 </ b> A to 61 </ b> C, the surface area of the iron-based preform 51 is increased to improve the adhesion and bonding strength with the molten aluminum alloy, and the molten aluminum alloy In some cases, the steel preform 51 is made into MMC by infiltration. These first to third bottomed holes 61A to 61C and the through hole 65 are formed at the time of pressure molding by a mold or at the time of processing a sintered body. Preferably, the molding is performed at the same time as the pressure molding with the mold, so that the production efficiency can be improved and the production cost can be suppressed.

  The through-hole 65 has a cylindrical inner surface that has a circular cross section and continues in the direction of the reference line Lb, and an inner end 66a that opens to the second inner peripheral surface 11b, and an outer side of the through-hole main body 66. It has a tapered hole portion 67 which is continuously formed at the end 66b and opens to the second outer peripheral surface 12b, and whose inner diameter gradually increases as it moves from the outer end 66b side of the through-hole body 66 to the second outer peripheral surface 12b side. doing. Like the through holes 21A to 21G of the first embodiment, the inner diameter A of the through hole body 66 is preferably 1 to 19 mm (1 mm.ltoreq.A.ltoreq.19 mm). The continuous portion of the side end 66a and the inner peripheral surface 11 is formed into a smoothly curved surface, so-called R shape or chamfered shape, and the depth C of the through hole 65 is 0.5 times or more the inner diameter A of the through hole body 66. Or less than 5 times (0.5 A ≦ C ≦ 5 A) is preferable.

  The first bottomed hole 61A has a cylindrical inner surface that is circular in cross section and continuous in the direction of the reference line La, and has a bottomed hole main body 62A having a bottom 62Ac at the inner end 62Aa, and an outer side of the bottomed hole main body 62A. A tapered hole portion 63A that is continuously formed at the end 62Ab, opens to the first outer peripheral surface 12a, and whose inner diameter gradually increases as it moves from the outer end 62Ab side of the bottomed hole body 62A to the first outer peripheral surface 12a side. Have.

  The second bottomed hole 61B has a cylindrical inner surface that is circular in cross section and continuous in the direction of the reference line Lc, and has a bottomed hole body 62B having a bottom 62Bc at the inner end 62Ba, and an outer side of the bottomed hole body 62B. A tapered hole portion 63B that is continuously formed at the end 62Bb, opens to the third outer peripheral surface 12c, and has an inner diameter that gradually increases from the outer end 62Bb side to the third outer peripheral surface 12c side of the bottomed hole body 62B. Have.

  The third bottomed hole 61C has a cylindrical inner surface that is circular in cross section and continuous in the direction of the reference line Ld, and has a bottomed hole main body 62C having a bottom 62Cc at the inner end 62Ca, and an outer side of the bottomed hole main body 62C. A tapered hole portion 63C that is continuously formed at the end 62Cb, opens to the fourth outer peripheral surface 12d, and whose inner diameter gradually increases as it moves from the outer end 62Cb side of the bottomed hole body 62C to the fourth outer peripheral surface 12d side. Have.

  The shapes of the first to third bottomed holes 61A to 61C and the through-hole 65 vary depending on the specifications such as the shape of the product to be converted into an MMC, but the bottomed hole bodies 62A to 62C of the first to third bottomed holes 61A to 61C The inner diameter a is preferably 1 to 19 mm (1 mm ≦ a ≦ 19 mm). Further, the depth c of the first to third bottomed holes 61A to 61C is preferably 0.5 to 5 times (0.5a ≦ c ≦ 5a) the inner diameter a of the bottomed hole main bodies 62A to 62C.

  In order to optimally set the inner diameter a of the bottomed hole main bodies 62A to 62C of each of the bottomed holes 61A to 61C and the depth c of the bottomed holes 61A to 61C according to the specifications such as the product shape to be converted to MMC, It is preferably determined in advance by experiments and simulations based on the adhesion state of the interface in the product and the occurrence state of cracks on the base material side.

  This iron-based preform 51 is subjected to shot blasting as necessary. By performing the shot blasting process, the oxide film formed on the surface is removed to clean the surface, and the free Cu phase dispersed in the matrix is exposed to the surface, thereby improving the castability by the aluminum-based alloy. .

  FIG. 10 shows an embodiment of a journal part in which this iron-based preform 51 is used, and the iron-based preform 51 is arranged at the journal part forming position of the casting mold when casting each cylinder block. Then, it is provided as MMC in the casting process.

  In this casting process, molten aluminum alloy poured on the outer peripheral surface 12 side of the iron-based preform 51 enters the inner peripheral surface 11 side of the iron-based preform 51 along the surface of the iron-based preform 51. In addition, even through the through-hole 65, it is supplied to the inner peripheral surface 11 side, and good hot-rollability of the molten aluminum alloy is obtained.

  The inner peripheral surface 11 during solidification and shrinkage of the molten aluminum alloy poured into the thin wall portions 38 and 39 between the bearing surfaces 34 and 36 of the journal portions 33 and 35 and the inner peripheral surface 11 of the iron-based preform 51. The shrinkage stress σ1 acts in the circumferential direction along the outer circumferential surface 12, and the shrinkage stress σ2 acts along the outer circumferential surface 12 in the circumferential direction also by solidification and shrinkage of the molten aluminum alloy poured on the outer circumferential surface 12 side. On the other hand, the first bottomed hole 61A, the through hole 65, the second bottomed hole 61B, and the third bottomed hole 61C of the iron-based preform 51 are solidified and contracted by the molten aluminum alloy that has entered the first bottomed hole 61C. The contraction stresses σ3, σ4, σ5, and σ6 act along 61A, the through hole 65, the second bottomed hole 61B, and the third bottomed hole 61C, respectively.

  The inner circumference of the molten aluminum alloy poured into the thin portions 38 and 39 is solidified and contracted by the drag due to the contraction stress σ4 due to the solidification and contraction of the molten aluminum alloy that has entered the through hole 65 of the iron preform 51. The shrinkage stress σ1 acting in the circumferential direction along the surface 11 is dispersed and received, the movement of the molten aluminum alloy along the inner peripheral surface 11 is suppressed, and the thin-walled portion after the shrinkage is in close contact with the inner peripheral surface 11 Residual stress generated in 38 and 39 can be reduced and evenly distributed, and the residual stress in the thin-walled portions 38 and 39 can be relaxed to prevent cracking of the portions.

  Similarly, the shrinkage stress σ3 due to solidification and shrinkage of the molten aluminum alloy that has entered the first bottomed hole 61A, the through hole 65, the second bottomed hole 61B, and the third bottomed hole 61C of the iron-based preform 51, Due to the drag by σ4, σ5, and σ6, the shrinkage stress σ2 acting along the outer peripheral surface 12 by the solidification and shrinkage of the molten aluminum alloy poured on the outer peripheral surface 12 side of the iron-based preform 51 is dispersed and received. Further, the movement of the molten aluminum alloy along the outer peripheral surface 12 is suppressed, and the aluminum alloy molten metal is brought into close contact with the outer peripheral surface 12, and the residual stress generated in the portion after shrinkage can be reduced and evenly dispersed.

  Furthermore, the iron-based preform 51 and the iron-based preform 51 are restrained and closely adhered along the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 51 of the aluminum-based alloy melt during solidification and shrinkage of the molten aluminum alloy. Generation of a gap at the interface with the base material due to the aluminum-based alloy can be prevented, and the interface bonding strength between the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 51 and the base material including the thin portions 38 and 39 can be secured.

  Here, since the iron-based preform 51 is made of an iron-based powder sintered body, the iron-based preform 51 has pores, and the molten aluminum-based alloy easily and stably adheres to the iron-based preform 51 during casting, and sometimes melts. Since the difference between the thermal expansion coefficient of the iron-based preform 51 soaked into MMC and the MMC-converted iron-based preform 51 and the crankshaft 41 made of iron-based material is reduced, the temperature of the journal portions 33 and 35 increases. However, the clearance between the crankshaft 41 and the bearing surfaces 34 and 36 can be within an allowable range, and vibration and noise during rotation of the crankshaft 41 can be prevented.

  Further, the formation of a gap at the interface between the inner peripheral surface 11 and the outer peripheral surface 12 of the iron-based preform 51 is prevented, and the interface strength between the inner peripheral surface 11 and the outer peripheral surface 12 is ensured, thereby forming an aluminum-based alloy. The heat conduction efficiency between the base material and the iron-based preform 51 is improved, the heat conductivity becomes uniform in the circumferential direction of the journal portions 33, 35, and the bearing surfaces 34, 36 side of the journal portions 33, 35 are evenly distributed. The support of the bearing metal by the journal portions 33 and 35 is stably expanded, and the increase in the friction coefficient between the crankshaft and the bearing metal is suppressed, and the fuel consumption, performance, durability, etc. of the engine are reduced as the frictional resistance decreases. Can be secured.

  Further, there is no gap at the interface between the thin wall portions 38, 39 and the iron-based preform 51 in the journal portions 33, 35, and the thin wall formed when the bearing surfaces 34, 36 of the journal portions 33, 35 are machined. The deformation of the portions 38 and 39 due to a load during processing is suppressed, and the processing accuracy of the journal portions 33 and 35 is improved.

  Here, when the shrinkage stress applied to the inner peripheral surface 11 side of the through-hole 65 is too small, the restraining force against the stress σ1 of the thin portions 38 and 39 accompanying the solidification and shrinkage of the molten aluminum alloy becomes too small. A continuous gap is formed at the interface between the inner peripheral surface 11 and the base material, and the interface strength becomes unstable. Therefore, in the present embodiment, the through hole body 66 of the through hole 65 formed in the iron-based preform 51 is formed in a cylindrical shape with a continuous inner surface having a circular shape with an inner diameter of 1 to 19 mm. If the inner diameter A is smaller than 1 mm, the restraining force against the stress σ1 of the thin wall portions 38 and 39 accompanying solidification and shrinkage of the molten aluminum alloy becomes too small, and the effect of improving the adhesion at the interface becomes extremely small. On the other hand, if the inner diameter A of the through-hole 65 is larger than 19 mm, there is a concern that the volume of the iron-based preform 51 is reduced and the original functional effect of the preform is reduced. The influence of shrinkage due to solidification is large, the adhesion with the base material in the through hole 65 is lowered, the restraining force against the stress σ1 of the thin wall portions 38 and 39 becomes too small, and the inner peripheral surface 11 and the base material Interfacial strength becomes unstable.

  If the drag due to the shrinkage stress σ3, σ5, σ6, σ4 due to solidification and shrinkage of the molten aluminum alloy that has entered the first to third bottomed holes 61A to 61C and the through hole 65 is too small, the aluminum-based alloy The restraining force against the stress σ2 of the base material on the outer peripheral surface 12 side due to solidification and shrinkage of the molten alloy becomes insufficient, and a continuous gap is formed at the interface between the outer peripheral surface 12 and the base material, and the interface strength becomes unstable. . Therefore, in the present embodiment, the inner diameter A of the through-hole 65 formed in the iron-based preform 51 and the inner diameter a of the first to third bottomed holes 61A to 61C are continuous with a circular cross section of 1 to 19 mm. Although formed into a cylindrical shape, if the inner diameter A of the through hole 65 and the inner diameter a of each of the bottomed holes 61A to 61C are smaller than 1 mm, the stress caused by the base material on the outer peripheral surface 12 side due to solidification and shrinkage of the molten aluminum alloy The restraining force against σ2 becomes too small, and the effect of improving the adhesion at the interface is extremely small. In addition, when shot blasting is performed, shots are well sprayed on the inner surfaces of the through hole body 66 and the bottomed hole bodies 62A to 62C. It is difficult to expect the effect of shot blasting.

  On the other hand, if the inner diameter A of the through-hole 65 and the inner diameter a of each of the bottomed holes 61A to 61C are larger than 19 mm, there is a concern that the volume of the iron-based preform 51 is reduced and the original functional effect is reduced. And the influence of the shrinkage | contraction accompanying solidification of aluminum alloy molten metal is large in the through-hole main body 66 and the bottomed hole main bodies 62A-62C, and the adhesiveness with the base material in the through-hole main body 66 and the bottomed hole main bodies 62A-62C is. As a result, the restraining force that counteracts the stress σ2 of the outer peripheral surface 12 and the base material becomes insufficient, and the interface strength between the outer peripheral surface 12 and the base material becomes unstable.

  Further, if the depth C of the through hole 65 and the depth c of the first to third bottomed holes 61A to 61C are smaller than 0.5 times the inner diameter A and the inner diameter a, respectively, the through hole 65 is cast at the time of casting. In addition, it becomes difficult for the molten aluminum-based alloy to enter the first to third bottomed holes 61A to 61C, and when the inner diameter A exceeds five times the inner diameter a, the iron-based preform 51 is pressed by a mold. It becomes difficult to cause additional machining of the through hole 65 and the first to third bottomed holes 61A to 61C by machining or the like, which causes a significant increase in manufacturing cost.

  In addition, the inner surface of the bottomed hole main bodies 62A to 62C of the first to third bottomed holes 61A to 61C of the iron-based preform 51 is shown in cross section in FIG. 11 (a), and the V arrow view is shown in FIG. A spiral groove 62c is formed on the inner surfaces of the bottomed hole main bodies 62A to 62C as shown in FIG. 12, a cross section is shown in FIG. 12 (a), and a bottom view as shown in FIG. By forming a plurality of ribs 62d on the inner surfaces of the hole bodies 62A to 62C, or by forming surface areas on the inner surfaces of the bottomed hole bodies 62A to 62C by forming slits or the like, the bottomed hole bodies 62A to 62C are formed. By increasing the area of the inner surface, it is possible to increase the shrinkage stresses σ3, σ5, and σ6 due to solidification and shrinkage of the molten aluminum alloy that has entered the first to third bottomed holes 61A to 61C. Thereby, the shrinkage stress σ2 acting in the circumferential direction along the outer peripheral surface 12 is more reliably received, and the movement along the outer peripheral surface 12 of the molten aluminum alloy is suppressed, and the adhesion effect between the outer peripheral surface 12 and the base material is achieved. While improving, the residual stress which arises in the base material after shrinkage | contraction can be reduced.

  Further, in the present embodiment, the first bottomed holes 61 </ b> A to 61 </ b> C that open to the outer peripheral surface 12 are drilled, but the bottomed holes that open to the inner peripheral surface 11 can also be arranged. Furthermore, the number, arrangement, size, and the like of the through holes and the bottomed holes can be optimally set according to specifications such as a product shape to be converted into an MMC. The number, arrangement, size, and the like of these through holes are preferably determined in advance by experiments and simulations based on the state of close contact of the interface and the occurrence of cracks on the base material side.

DESCRIPTION OF SYMBOLS 1 Iron-type preform 10 for metal matrix composite formation Preform main body 11 Inner peripheral surface 12 Outer peripheral surface 21A-21H The 1st-8th through-hole (through-hole)
22c Spiral groove (surface area expansion treatment)
22d rib (surface area expansion treatment)
33, 35 Journal part 34, 36 Bearing surface (concave surface)
38, 39 Thin-walled portion 51 Iron-based preforms 61A to 61C First to third bottomed holes 62c Spiral groove (surface area enlargement process)
62d rib (surface area expansion treatment)
65 Through-hole A Through-hole inner diameter B Through-hole spacing C Through-hole depth a Inner diameter of bottomed hole c Bottomed hole depth

Claims (6)

It is cast with an aluminum-based alloy base material having a concave surface continuously formed along the direction in which the central axis extends in a semicircular cross section, and the central axis extends in a semicircular arc or U shape in cross section along the concave surface. In an iron-based preform for forming a metal matrix composite comprising a preform body having an inner peripheral surface and an outer peripheral surface continuous along a direction,
The preform body has a through-hole that communicates the inner peripheral surface and the outer peripheral surface, and an inner surface of the through-hole is subjected to a surface area enlargement process. System preform.   The iron-based preform for forming a metal matrix composite according to claim 1, wherein a bottomed hole is formed in the inner peripheral surface and / or outer peripheral surface of the preform body.   The iron-based preform for forming a metal matrix composite according to claim 2, wherein the inner surface of the bottomed hole is subjected to a surface area enlargement process. It is cast with an aluminum-based alloy base material having a concave surface continuously formed along the direction in which the central axis extends in a semicircular cross section, and the central axis extends in a semicircular arc or U shape in cross section along the concave surface. In an iron-based preform for forming a metal matrix composite comprising a preform body having an inner peripheral surface and an outer peripheral surface continuous along a direction,
The preform body is formed with a bottomed hole that opens to an inner peripheral surface and / or an outer peripheral surface, and a surface area enlargement process is performed on the inner surface of the bottomed hole. Iron-based preform.   5. The metal-based composite material-forming iron-based preform according to claim 4, wherein the preform body has a through-hole that communicates the inner peripheral surface with the outer peripheral surface.   The metal-based composite material-forming iron-based preform according to any one of claims 1 to 5 is formed in a semicircular cross section along the inner peripheral surface of the preform main body along the central axis extending direction. A journal part structure characterized by being cast with an aluminum alloy base material having a concave bearing surface formed continuously.

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