JP2006272359A - Bore pin for casting cylinder block - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bore pin for casting a cylinder block with which the formation positional accuracy of the cylinder bore can be held under excellent state and the durable service life is longer in comparison with the conventional material by improving the wear resistance on the surface of the bore pin. <P>SOLUTION: This bore pin is used for inserting into a liner when the cylinder block is cast, and formed with a coating layer composed of a high-speed steel base alloy at the portion in contact with at least the liner in a base material composed of a metal material. The above coating layer is composed of an Fe-base alloy containing by mass of 1.0-3.0% C, 0.1-2.0% Si, 0.1-2.0% Mn, 0-4.5% Ni, 3.0-10.0% Cr, 0-9.0% Mo, 0-10.0% W and 1.0-10.0% V. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bore pin used when casting a cylinder block of an automobile engine or the like.

  A cylinder block of an automobile engine is formed by casting a light alloy material such as an aluminum alloy by a die casting method or the like in order to reduce the weight. In the cylinder block, cylinder bores, which are parts where the piston slides, are formed according to the number of cylinders. However, when the cylinder bore is formed of a single light alloy material such as an aluminum alloy, sufficient wear resistance against sliding of the piston cannot be obtained. For this reason, a cylindrical liner (also referred to as a sleeve) made of a wear-resistant material is placed in the cylinder bore portion in the mold during cylinder block molding, and the cylinder bore is formed by casting the liner with a light alloy. Has been made.

  As a liner having excellent wear resistance provided on the inner surface of a cylinder bore, FC materials (grey cast iron), composite materials in which reinforcing materials such as silicon carbide particles and reinforcing fibers are dispersed in an aluminum alloy, and the like are used.

  When molding a cylinder block with this type of liner, a bore pin (also referred to as a nesting) protrudes into the cavity of the mold, and the liner is fitted into the bore pin and held in the aluminum. Fill with molten metal such as alloy. Examples of prior art relating to such a cylinder block casting bore pin include the following.

  In Patent Document 1, a bore pin for mounting a sleeve is disposed at a position where a cylinder bore in a cylinder block casting mold is to be formed, and the bore pin is moved from the proximal end side to the distal end side along the axial direction thereof. In the cooling structure of the bore pin in which the cooling chamber is formed and the cooling pipe is inserted and disposed on the base end side of the bore pin with the opening end facing the cooling chamber, the position of the opening end of the cooling pipe is A cooling structure of a cylinder block casting bore pin at the position of the mold head cylinder joint joint forming surface or the inner position of the mold near this position when the mold is disposed is described.

  In Patent Document 2, a cylindrical cylinder liner that forms a bore portion is inserted into a casting mold having a bore mold pin that becomes a nest for forming a cylinder bore, and the bore mold pin is inserted. A cylinder block casting method including a step of pouring a molten aluminum alloy into a casting mold, and solidifying by casting. A bore mold pin is formed in a cylinder liner after casting. A cylinder block casting method is described in which the inner surface of the cylinder liner is deformed by the residual stress after casting so that the outer surface is a perfect circle.

  In Patent Document 3, a step of pouring molten aluminum or molten aluminum alloy into a mold having an insert and a flow path of the melt formed by the insert and the inner surface of the mold are rapidly narrowed. The step of flowing through the narrowed narrow passage portion, the step of filling and holding the molten metal in the cavity between the mold and the insert after flowing through the narrow passage portion, and the molten metal filled and held in the cavity are solidified. A step of providing a recess in the end face of the nest adjacent to the niche part and delaying solidification of the melt in the niche part by flowing the melt into the recess. Has been.

JP-A-6-71405 JP 2002-153967 A JP 2002-178133 A

  When molding a cylinder block with a liner as described above, a bore pin is projected into the mold cavity, and the liner is fitted into the bore pin, and the cavity is filled with a molten metal such as an aluminum alloy. To do. Then, after the molten metal in the mold is solidified, the cylinder block in which the liner is cast is taken out from the mold, and the liner is pulled out from the bore pin.

  Therefore, the bore pin is required to have sufficient heat resistance since it is pulled out from the liner made of the wear-resistant material together with sufficient heat resistance. As a conventional bore pin, a hot tool steel equivalent to JIS SKD61, or one that has been subjected to heat treatment such as quenching and tempering and then subjected to soft nitriding treatment to impart heat resistance and wear resistance, etc. is used. Yes.

  On the other hand, since the cylinder bore of the cylinder block is required to have a high precision in the formation position, the bore pin and the liner are closely fitted to each other. In addition, a small amount of molten metal may be inserted into the gap between the bore pin and the liner at the time of casting. Further, the bore pin is heated and expands under the influence of the heat of the molten metal or the mold that is repeatedly used.

  In such a state, when the bore pin and the liner are attached and detached, both become easy to bite. For this reason, in the conventional bore pin, there is a problem that the wear on the surface of the bore pin becomes remarkable, the accuracy of the formation position of the cylinder bore cannot be maintained well, and the service life is shortened due to damage.

  In view of this problem, the present invention provides a bore block for casting a cylinder block that can maintain the accuracy of the formation position of the cylinder bore by improving the wear resistance of the surface of the bore pin, and has a longer service life than conventional materials. With the goal.

  A bore pin for casting a cylinder block according to the present invention is a bore pin that is used by being fitted into a liner when casting a cylinder block, and at least a portion of a base material made of a metal material that comes into contact with the liner is coated with a high-speed alloy. A layer is formed.

  In the present invention, the coating layer is mass%, C: 1.0 to 3.0%, Si: 0.1 to 2.0%, Mn: 0.1 to 2.0%, Ni: 0 to Fe-based alloy containing 4.5%, Cr: 3.0 to 10.0%, Mo: 0 to 9.0%, W: 0 to 10.0%, V: 1.0 to 10.0% It is characterized by comprising. Further, the coating layer is characterized by containing at least one of Co: 10.0% or less and Nb: 10.0% or less in mass%. Moreover, it is desirable to form the coating layer by casting.

  The bore block for cylinder block casting of the present invention has a coating layer made of a high-speed alloy formed on the outer periphery (at least a portion in contact with the liner) of a base material made of a metal material such as a steel-based material or an iron-based material having excellent toughness. Therefore, the wear resistance can be remarkably improved as compared with the conventional hot work tool steel.

  As a means for forming the coating layer of the present invention, the cast-in method is preferable because the manufacturing cost can be kept low. Since the coating layer is metallically joined to the outer periphery of the bore pin base material made of a metal material by casting, the cooling by the cooling chamber provided inside the base material can be sufficiently transmitted to the coating layer.

The high-speed alloy that forms the coating layer of the present invention is a high alloy material containing a large amount of V and Cr as compared with SKD61 steel, and since the carbide is finely dispersed, sufficient wear resistance is obtained. In the coating layer made of a high-speed alloy, any of MC carbide, M ₂ C carbide, M ₆ C carbide, M ₇ C ₃ carbide, M ₄ C ₃ carbide and M ₂₃ C ₆ carbide Since one or more types are contained in a relatively large amount, the wear resistance can be remarkably improved. The sum of the area ratios of these carbides is preferably 25% or less, and if it exceeds this, the coating layer becomes brittle, which is not preferable.

Furthermore, in order to ensure hardness, the sum of the area ratios of particularly hard MC-based carbides and M ₂ C-based carbides is preferably 10% or more. Further, if the amount of eutectic carbides in the form of needles or networks is excessive, necessary mechanical properties, particularly toughness, cannot be ensured. However, by properly crystallizing MC carbides, M ₂ C carbides, M ₇ It is possible to cut the C ₃ carbide network to ensure toughness.

  The chemical component (mass%) of the coating layer relating to the bore block for cylinder block casting of the present invention is preferably in the following range.

C: 1.0 to 3.0%
C is necessary for the formation of carbide for improving the wear resistance and the improvement of the hardness of the base during quenching and tempering by solid solution in the base. C produces MC, M ₂ C, M ₆ C, M ₇ C ₃ , M ₄ C ₃ , and M ₂₃ C ₆ -based carbides that contribute to improved wear resistance. When C is less than 1.0%, there is little crystallization of carbide effective for improving the wear resistance, and there is not enough C dissolved in the matrix, and sufficient matrix hardness cannot be obtained even by quenching. On the other hand, if it exceeds 3.0%, the carbides become coarse and the amount of crystallization becomes excessive, and the toughness tends to deteriorate.

Si: 0.1 to 2.0%
The Si content is preferably 0.1 to 2.0%. Since Si acts as a deoxidizer and is contained in M ₆ C-based carbide as a solid solution by substituting elements such as W and Mo, it is intended to save expensive elements such as W and Mo. It is effective for. If Si is less than 0.1%, the deoxidation effect is insufficient and casting defects are likely to occur. Moreover, when it exceeds 2.0%, embrittlement tends to occur.

Mn: 0.1 to 2.0%
The Mn content is preferably 0.1 to 2.0%. Mn has a deoxidizing action like Si. Moreover, there exists an effect | action which fixes S which is an impurity as MnS. When Mn is less than 0.1%, deacidification is poor. On the other hand, if it exceeds 2.0%, retained austenite tends to be generated, and sufficient hardness cannot be maintained stably.

Ni: 0 to 4.5%
Ni does not necessarily need to be added, but when added, it has the effect of improving hardenability and increasing hardness. If the Ni content exceeds 4.5%, the retained austenite becomes excessive and high hardness cannot be obtained. A more preferable Ni content is 0 to 2.0%.

Cr: 3.0 to 10.0%
Cr combines with C to crystallize and generate carbides, and also dissolves in the matrix to increase the hardness of the matrix, thereby improving wear resistance. If Cr is less than 3.0%, the effect cannot be secured sufficiently. On the other hand, if it exceeds 10.0%, the retained austenite at room temperature increases, so that the number of tempering increases and this is not economical. Further, Cr forms M ₇ C ₃ and M ₂₃ C ₆ carbides having relatively low hardness, and if added in a large amount, these carbides become excessive and wear resistance deteriorates.

Mo: 0 to 9.0%
Mo does not necessarily need to be added, but when added, it combines with C like Cr and produces hard M ₂ C and M ₆ C carbides. Moreover, when tempering at high temperature, it is an element which contributes strongly to the secondary hardening. When the Mo content exceeds 9.0%, in the balance of C, V, and Mo, a large amount of M ₂ C and M ₆ C carbides are crystallized, and the toughness decreases. A more preferable Mo content is 1.0 to 8.0%.

W: 0 to 10.0%
W does not necessarily need to be added, but when added, it enhances the hardenability of the matrix and combines with C to produce hard M ₂ C and M ₆ C carbides. Further, W produces hard carbides like Cr and Mo, and can be substituted for these elements and added. If the W content exceeds 10.0%, the M ₆ C carbide is coarsened and the brittleness deteriorates, which is not preferable.

V: 1.0-10.0%
V forms a hard MC-based carbide, M ₄ C ₃ -based carbide, which contributes most to the improvement of wear resistance. When V is less than 1.0%, the generation of carbide is small and the wear resistance is insufficient. When V exceeds 10.0%, austenite, MC, or M ₄ C ₃ carbides are crystallized as primary crystals due to the balance with the C content. If austenite crystallizes in the primary crystal, the hardness becomes insufficient. Further, if MC and M ₄ C ₃ type carbides are crystallized as primary crystals, it is not preferable since they cause segregation during aggregation and cause brittle deterioration. A more preferable content of V is 2.0 to 8.0%.

  The balance is Fe and impurity elements. Furthermore, in addition to the above, any one or more of Co and Nb can be contained.

Co: 10.0% or less Co is dissolved in the base irrespective of the formation of carbides, and has the effect of increasing toughness and improving high-temperature hardness and wear resistance. If Co exceeds 10.0%, the effect is saturated and expensive, so this was made the upper limit.

Nb: 10.0% or less Nb, like V, forms a hard MC-based carbide, M ₄ C ₃ -based carbide, which contributes most to the improvement of wear resistance. When Nb exceeds 10.0%, toughness is reduced, and austenite, MC, or M ₄ C ₃ carbide is crystallized as the primary crystal due to the balance with the C content. If austenite crystallizes in the primary crystal, the hardness becomes insufficient. Further, if MC and M ₄ C ₃ are crystallized as primary crystals, they are aggregated and segregated during solidification to cause brittle deterioration. Moreover, Nb can be substituted with V, and the more preferable total content of Nb and V is (Nb + V): 2.0 to 8.0%.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing a bore pin according to an embodiment of the present invention. In FIG. 1, a bore pin 1 is formed by metal-bonding a coating layer 3 made of a high-speed alloy on the outer periphery of a base material 2 made of a steel material having a diameter of 70 mm and a length of 200 mm by a cast-in method.

  As the coating layer 3, the chemical components in mass% are C: 1.9%, Si: 0.8%, Mn: 0.4%, Cr: 4.7%, Mo: 5.7%, V: 6. An ingot of 5%, Fe: the remaining high-speed alloy material was melted at 1450 ° C., and this molten high-speed alloy was cast on the outer periphery of the base material 2 which was heated upright inside the mold, and casted. Thus, the coating layer 3 was formed in the outer periphery of the base material 2 with the cast-in method.

Further, in the coating layer 3 made of a high-speed alloy, MC carbide, M ₂ C carbide, M ₆ C carbide, M ₇ C ₃ carbide, M ₄ C ₃ carbide and M ₂₃ C ₆ carbide are included. The total of the area ratios of any one or more of was 19%. The carbides in the coating layer 3 were mainly 13% MC-based carbides and 5% M ₂ C-based carbides.

  Further, a hollow cooling chamber 4 is provided inside the bore pin 1, a cooling liquid such as water is poured into the cooling chamber 4, the bore pin 1 is cooled to suppress thermal expansion of the bore pin 1, and the liner 7 fitted therein. Makes it easy to pull out. Reference numeral 8 denotes a mold, and the base of the bore pin 1 is fixed by a bolt or the like.

  When this bore pin is used for die casting of a cylinder block of an automobile engine, the wear resistance of the bore pin surface provided with the coating layer of the present invention can be remarkably improved, and the formation accuracy of the cylinder bore can be maintained well over a long period of time. It was confirmed that the service life was extended compared with the conventional material.

  According to the cylinder block casting bore pin of the present invention, the wear resistance of the bore pin surface can be remarkably improved in the casting of the cylinder block, the formation accuracy of the cylinder bore can be maintained well, and the service life is longer than that of the conventional material. Therefore, high quality cylinder blocks can be manufactured stably.

It is a schematic sectional drawing which shows the bore pin of the Example of this invention.

Explanation of symbols

1 bore pin, 2 base material, 3 coating layer, 4 cooling chamber,
7 liners, 8 molds

Claims (4)

A bore pin that is used by being fitted into a liner when casting a cylinder block, wherein a coating layer made of a high-speed alloy is formed on at least a portion of a base material made of a metal material that comes into contact with the liner. Bore pin for block casting. The coating layer is mass%, C: 1.0-3.0%, Si: 0.1-2.0%, Mn: 0.1-2.0%, Ni: 0-4.5%, It is made of an Fe-based alloy containing Cr: 3.0 to 10.0%, Mo: 0 to 9.0%, W: 0 to 10.0%, and V: 1.0 to 10.0%. The bore pin for cylinder block casting according to claim 1. The bore pin for cylinder block casting according to claim 2, wherein the coating layer further contains at least one of Co: 10.0% or less and Nb: 10.0% or less in terms of mass%. The bore block for cylinder block casting according to any one of claims 1 to 3, wherein the coating layer is formed by casting.

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