JP2006015383A - Tool for treating inner wall surface of prepared hole for screw in casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tool for treating the inner wall surface of a prepared hole for screw in a casting with which blow hole as the peculiarity to the casting is cut in pieces and eliminated by treating the inner wall surface of the hole formed in the casting at high speed so as not to become over-heat, and the metal structure is improved so as not to leak liquid from the blow hole formed in the casting. <P>SOLUTION: The tool for treating the inner wall surface has the cross sectional round-shaped bar structure, and is provided with an inserting part for inserting into a hole as cast in the casting and a base end part for supporting the above inserting part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tool for treating an inner wall surface of a hole having a circular cross section formed in a casting.

  Conventional casting products have coarse metal crystal grains, and when a fluid such as gas or liquid is sealed in a casting hole, fluid leakage may occur between the holes formed in the casting. For example, when a case rocker of an engine part having an oil passage that constitutes a hydraulic circuit is manufactured by aluminum die casting and a plurality of screw holes are formed in the vicinity of the oil passage, oil flowing through the oil passage is formed between metal structures. There is a problem that oil permeates through a cast hole and the oil leaks from the oil passage into the screw hole.

As a method for solving such a problem, for example, a method of partially impregnating a screw hole with resin, water glass or the like (organic impregnation or inorganic impregnation) to prevent oil from oozing into the screw hole is known. It has been. In addition, there are known methods such as press-fitting another tubular member into the screw hole, or embedding a part in which a screw thread is previously formed at a desired position.
JP-A-5-237726 JP 2000-31980 A

  However, the conventional leakage prevention method represented by Patent Document 1 has a drawback in that it requires a resin impregnation step separately from a machining step by an NC machine tool or the like, which deteriorates the machining efficiency. The same applies to the case where a method of modifying the metal structure with an electron beam or a laser is employed, and there is a problem that blisters and the like are generated particularly in die casting.

  In addition, when a method of embedding another member in the screw hole is adopted, there is a problem that a process of separating parts is required when processing or recycling a defective product, and the efficiency of the recycling process is deteriorated.

  In the method of reforming the cylindrical inner surface of a metal member described in Patent Document 2, the bottom surface of the machining hole is flat, the tool tip is also flat, and the outer diameter is larger than the diameter of the cylindrical (hole) surface. By inserting a large tool, the difference between the inner diameter of the hole and the outer diameter of the tool is scraped off, and the metal inner surface of the hole is modified by the cutting heat and frictional heat generated at this time. With a tool having a flat tip, the feed force is excessive and high speed feed (for example, 100 mm / min) is impossible. In addition, a tool with a flat tip has a frictional heat of excessively 410 to 470 degrees, which is a problem that causes thermal distortion in the product and a phenomenon in which metal is scraped off. There is a problem that the flow is rather reduced and the improvement of pressure leakage becomes ineffective.

  In addition, when the cast is a non-ferrous metal such as aluminum, if the change in thickness is large, the solidified structure becomes uneven particularly in the thick portion, and casting defects such as pinholes and shrinkage cavities are likely to occur.

  The present invention has been made under the circumstances described above, and the object of the present invention is to provide a casting by treating the inner wall surface of a hole formed in a non-ferrous metal casting at a high speed and without overheating. It is a tool for inner wall surface treatment used for inner wall surface treatment of a hole in a casting to modify a metal structure so that fluid is not leaked from the casting hole formed in the casting by dividing and disappearing a specific casting hole, An object of the present invention is to provide an inner wall surface processing tool that is excellent in toughness, bending strength and impact resistance that can withstand severe conditions in inner wall surface processing.

  The present invention relates to an inner wall surface processing tool, and the object of the present invention is a rod-like structure having a circular cross section, and includes an insertion portion for insertion into a casting hole of a casting, and a base end portion that supports the insertion portion. This is achieved by providing.

  Further, the material of the inner wall surface processing tool of the present invention is more effective by being a cemented carbide for hot forging, by being an ultra-fine grain cemented carbide, or by being a coarse WC raw material. Is achieved.

  According to the present invention, it is possible to form a modified layer made of a dense metal structure around the hole formed in the casting, and it is possible to suppress or prevent fluid leakage into the hole. By setting the cross sectional area of the tool tip to 1.05 to 1.30 times the cross sectional area, the modified layer can be generated more efficiently. Further, the reformed layer can be efficiently formed by setting the rotational speed of the rod-shaped tool in the range of 1600 to 8000 rpm, and the modified layer can be efficiently formed by setting the feed speed of the rod-shaped tool in the high speed range of 100 to 500 mm / min. Can be formed.

  In addition, the tool material is made of cemented carbide for hot forging, ultra-fine grained cemented carbide or coarse grained WC (tungsten carbide) raw material, for inner wall treatment with excellent toughness, bending strength and impact resistance. Tools can now be provided.

  The modified layer is a layer in which the metal structure of the casting is modified, and has a dense metal structure as compared with the metal structure of other portions. FIG. 10 (A) is a structure diagram of a casting in a thread valley portion for performing the process of the present invention, FIG. 10 (B) is a structure diagram of a normal base material of the casting, and FIGS. 11 and 12 are the details thereof. Organization chart. As shown in FIG. 12, the cast structure of the die casting (as cast structure) is an α dendrite (a dendritic crystal in which Si, Cu, Mg, etc. are dissolved in Al) and a eutectic (mainly Si is crystallized simultaneously, These are mixed). On the other hand, as shown in FIG. 11, when the structure subjected to the treatment of the present invention is subjected to plastic flow by forming, the as cast structure is divided into α crystal and eutectic, and as a result, the cast hole and gas porosity are divided. It can be seen that most of them disappeared by being divided and filled with metal.

  The present invention occurs when a tool having a diameter of a screw hole is inserted into a die-casting member, a sand casting member, a die casting member, a low-pressure casting member, or the like at a high speed rotation and high speed feed into a processing hole. Softens the material by frictional heat, causes plastic flow, causes metal filling in the casting cavity and breaks the casting cavity, and as a result, breaks the casting cavity circuit that causes pressure leakage to prevent pressure leakage. It is what I did. If the temperature of the frictional heat is 350 ° C. or higher, there is a greater possibility of problems such as deformation and blistering in the material. Therefore, in the present invention, the temperature is set to 230 to 320 ° C.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a hole (cast hole) 2 formed in a casting 1 made of aluminum die-casting, and has a shape (taper) in which the cross-sectional area gradually decreases toward the bottom 21, and the bottom 21 of the hole 2 is It has a hemispherical concave surface. The inner wall surface processing tool 3 of the present invention for processing the inner wall surface 22 of the hole 2 has a structure shown in FIG. The inner wall treatment tool 3 is a cemented carbide for hot forging with excellent toughness, an ultra-fine grained cemented carbide with a refined carbide phase compared to a cemented carbide for warm forging with excellent bending strength, or An insertion portion 32 made of a coarse WC raw material, having a circular cross-sectional shape, having a diameter (slightly large) corresponding to the diameter of the hole 2 and processing the inner wall surface 22, and the insertion portion 32 And a base end portion 31 that supports the insertion portion 32 and has a hemispherical convex portion and a cross-sectional area toward the distal end portion. It has a taper that gradually decreases. The taper angle is formed to be the same as or larger than the angle of inclination of the inner peripheral surface of the hole 2. The length L of the insertion portion 32 is the same as or slightly longer than the depth of the hole 2, and the base end portion 31 at the boundary between the insertion portion 32 and the base end portion 31 is rounded (R) or chamfered. The inclined shape 35 is formed.

  FIG. 3 shows the detailed structure of the inner wall surface processing tool 3, and the taper of the insertion portion 32 is in the range of 0 to 60 degrees depending on the taper of the hole 2. Further, the chamfering of the base end portion 31 may be in the range of 0 to 180 degrees.

  With respect to the hole 2 formed in the casting 1 as described above, the inner wall surface processing tool 3 is arranged on the axis of the hole 2 as shown in FIG. 4 and is rotated (1600 to 8000 rpm) into the hole 2. Insert (feed speed is 100 to 500 mm / min). Since the outer diameter of the insertion portion 32 of the inner wall surface processing tool 3 is formed to be slightly larger than the inner diameter of the hole 2, the outer peripheral surface 34 of the inner wall surface processing tool 3 and the inner wall (inner peripheral surface) 22 of the hole 2 are formed. In a pressed state and relatively (in this example, the inner wall surface processing tool 3 rotates), high frictional heat is generated between both surfaces, and the inner wall of the hole 2 is generated by the generated frictional heat. The surface metallographic structure is plastically deformed. Since the insertion portion 32 of the inner wall surface processing tool 3 has a taper corresponding to the taper of the hole 2, the outer peripheral surface 34 of the inner wall surface processing tool 3 efficiently presses the inner wall 22 of the hole 2 without a gap. be able to. Moreover, since the front end portion 33 of the inner wall surface processing tool 3 has a hemispherical convex shape, the force of pressing the casting 1 at the front end portion 33 by the rotation and feed movement of the inner wall surface processing tool 3 is more exerted. Friction occurs, frictional heat is generated on the inner wall 22 of the hole 2, a dense metal structure can be formed, the cast hole in the inner wall portion is divided and disappeared, and the metal structure is divided.

  When the inner wall surface processing tool 3 is fully inserted into the hole 2, the inclined shape 35 of the base end portion 31 comes into contact with the upper portion of the inner wall 22 of the hole 2, so that even when a burr or the like generated by friction protrudes from the hole 2. , Can be surely solved.

  Further, by pulling out the inner wall surface processing tool 3 from the hole 2 while rotating, the base of the casting 1 absorbs heat, and the heated portion is rapidly cooled. The extraction of the inner wall surface processing tool 3 is performed at a rotational speed of 1600 to 8000 rpm as in the insertion, but this rotation may be performed relatively. This is a necessary condition to reduce the adhesion of the material metal to the inner wall surface processing tool 3 and to obtain a smooth finished surface. By continuing to rotate, the frictional heat is continuously supplied to the periphery. A smooth surface can be obtained by reducing the restraining force of the inner wall surface processing tool 3 due to shrinkage and reducing the rotational resistance. Thus, a modified layer 22A is formed at a depth of about 0.5 to 3.0 mm from the inner wall surface of the heated hole 2 as shown in FIG. The modified layer 22A is a layer in which the metal structure of the casting 1 is modified, and has a finer metal structure than the metal structure of other portions. Since the inner wall surface processing tool 3 of the present invention has the inclined shape 35 at the outer lower portion of the base end portion 31, the inner wall processing tool 3 comes into contact with the inner wall upper portion of the hole 2 to eliminate burrs and the like, and thus becomes smooth and flat. ing.

  In order to efficiently generate such a modified layer 22A, for example, the rotational speed of the inner wall surface processing tool 3 is preferably set in a range of 1600 to 8000 rpm. If it is smaller than this range, sufficient heat generation cannot be obtained, and if it is larger, useless power is used. Further, the feed speed of the inner wall surface processing tool 3 is preferably in the range of 100 to 500 mm / min. If it is smaller than this range, the processing efficiency will deteriorate, and if it is faster, the modified layer 22A will not be sufficiently formed. FIG. 6 shows an actual measurement diagram of the correlation between the tool rotational speed (rpm) and the feed speed (mm / min). From FIG. 6, the rotational speed of the inner wall surface processing tool 3 is set to a range of 1600 to 8000 rpm, The feed speed of the inner wall surface processing tool 3 is in the range of 100 to 500 mm / min. When the inner wall surface treatment is performed under these conditions, adhesion of the cast metal to the inner wall surface processing tool 3 is reduced, and a smooth finished surface can be formed.

  The relationship among the tool diameter, area ratio, rotational speed, feed rate, and temperature is actually as shown in Table 1 below, and it was confirmed that the friction temperature was 230 to 320 ° C. From Table 1, it is impossible to insert a tool at a rotational speed of 1500 rpm and a feed speed of 100 to 300 mm / min, and no heat is transferred to the back boss at a rotational speed of 6000 to 8000 rpm and a feed speed of 500 to 800 mm / min. It turns out that a crack occurs in the back boss. Further, when pulled out from the hole at a rotational speed of 0, the aluminum weld attached to the inner wall surface processing tool 3 causes a vertical burr at the entrance of the hole 2.

また、表２はネジ下穴径に対する横断面面積比の関係を示しており、本発明の内壁面処理用工具３では横断面面積比１．０５〜１．３０倍（直径で１．０２〜１．１４倍）を使用するようになっている。この表２からも分かるように、断面積比１．０５倍以下では十分な摩擦熱が発生せず、１．３０倍以上では摩擦熱を過剰に発生して、素材温度が上昇して変形が生じる。断面積比が１．３０倍以上では、摩擦熱を発生するには１００ｍｍ／ｍｉｎ以下の送り速度で成形する必要があり、生産性に問題が生じるし、同様に送り速度を下げると発生熱温度が上昇し、製品に変形が生じる問題がある。通常のダイカスト鋳物部材では、工具断面積比が１．３０倍以下であれば盛り上がりバリのないネジ下穴の成形が可能である。通常のダイカスト鋳物は高速射出で鋳造するため、鋳巣及びガスポロシティがかなり多く存在するため、その部分に金属が充填されるため盛り上がらない。

Table 2 shows the relationship of the cross-sectional area ratio to the screw pilot hole diameter. In the inner wall surface processing tool 3 of the present invention, the cross-sectional area ratio is 1.05 to 1.30 times (1.02 in diameter). 1.14 times). As can be seen from Table 2, sufficient frictional heat is not generated when the cross-sectional area ratio is 1.05 times or less, and excessive frictional heat is generated when the cross-sectional area ratio is 1.30 times or more. Arise. If the cross-sectional area ratio is 1.30 times or more, it is necessary to mold at a feed rate of 100 mm / min or less in order to generate frictional heat, which causes a problem in productivity. Similarly, if the feed rate is lowered, the generated heat temperature As a result, there is a problem that the product is deformed. In a normal die-cast casting member, if the tool cross-sectional area ratio is 1.30 times or less, it is possible to form a screw pilot hole without a raised burr. Since ordinary die castings are cast by high-speed injection, there are quite a large amount of voids and gas porosity.

なお、内壁面処理用工具３は、ＮＣ工作機械やラジアルボール盤等の工作機械による機械加工ライン内で使用することができる。

The inner wall surface processing tool 3 can be used in a machining line by a machine tool such as an NC machine tool or a radial drilling machine.

  In the hole 2 in which the modified layer 22A is generated as described above, a female screw 23 is formed by a tapping device, for example, as shown in FIG. When oil leaks from the oil passage 5 formed in the vicinity, the oil leakage into the hole 2 is suppressed or prevented by the modified layer 22A.

  In the above description, the tip 33 of the inner wall surface processing tool 3 is a hemispherical convex portion. However, as shown in FIG. 8, it may have a rounded (R) shape 35, as shown in FIG. Thus, the shape 36 with chamfered corners may be used. When the hole 2 does not have a taper, the insertion portion 32 of the inner wall surface processing tool 3 may not have a taper.

  The casting 1 includes die casting, die casting, sand casting, low pressure casting and the like, and is not limited to manufacturing means. As a non-ferrous metal, the casting material may be magnesium or a magnesium alloy in addition to aluminum or an aluminum alloy. Further, the casting includes a zinc alloy casting and a copper alloy casting.

  In the present embodiment, the hole 2 is a cast hole, but it may be a drill hole or a processed hole formed by a drill or the like. The method for forming the pilot hole is not particularly limited. In the case of a punched hole, it is particularly preferable in that a step for forming a hole is not necessary and that no chips are generated by a drill. Moreover, when forming a hole with a drill etc., it is preferable at the point which does not need to change the shape of a casting_mold | template and a design change is easy. A drilled hole corresponding to a cast hole can be used in a place where the cast hole does not exist, for example, when a cast pin cannot be installed due to the structure of the mold or when the cast hole is too small. In this case, the drilled hole dimensions are the same as the punched holes.

  In the inner wall surface treatment, since an excessive bending stress is applied to the inner wall surface treatment tool 3, it is preferable to select a material that can withstand it. The material of the inner wall surface processing tool 3 is, for example, a cemented carbide that has high toughness, such as a cemented carbide for warm forging (for example, WF-56 manufactured by Sumitomo Electric) and a carbide layer that is further refined compared to cemented carbide. Super ultrafine cemented carbide with excellent strength (for example, AF-1 manufactured by Sumitomo Electric, NM-08, NM-15 manufactured by Hitachi Tool, etc.), WC (tungsten carbide) raw material (for example, NC-16 manufactured by Daidget Industries, etc.) ). By using such an alloy, it has both toughness, bending strength and impact resistance that can withstand severe conditions. Further, carburizing, nitriding, and ceramic coating surface hardening treatment may be performed to prevent aluminum adhesion. Furthermore, the shape of the inner wall surface processing tool 3 may be configured such that a screw is formed on the outer peripheral surface. In this case, after the tip of the inner wall surface processing tool 3 reaches the bottom of the hole 2, the inner wall surface processing tool 3 is rotated in the direction in which the screw comes out, and the inner wall surface processing tool 3 is adjusted in accordance with the pitch of the screw. By pulling out, a screw can be formed simultaneously with the generation of the modified 22A.

  By using the inner wall surface processing tool of the present invention, it is possible to produce a hydraulic equipment part having a hydraulic path inside, a casting of a gas equipment part provided with a gas path, and the like. For example, as engine parts, rocker cover, case rocker, case bracket, cylinder head, cylinder block, crankcase, oil pan, front cover, case front, retainer front, inlet manifold, case oil cooler, case oil filter, case rear, Examples include a housing flywheel. In addition to engine parts, drive units, hydraulic equipment, gas equipment cases, bodies, covers, and the like. Moreover, as a drive component, it is applicable also to a housing clutch, a case transmission, a gear box, a quartz box, a rear cover, and a housing extension.

  As mentioned above, although embodiment of this invention was described, the content mentioned above is one Embodiment of this invention, and is not a thing of the meaning that this invention is limited to this. As shown in FIG. 13, the method according to the present invention can also be used for the inner wall surface of a hole having no bottom.

  Hereinafter, although an Example is described in detail, this invention is not limited to these.

  About the inner wall surface processing tool 3 of the present invention, the inner wall surface processing tool 3 with different materials is manufactured, and how much it can withstand the severe conditions in the inner wall surface processing (how much toughness, bending strength and (Is it shock resistant?) A test was conducted.

  As shown in FIG. 4, the inner wall surface processing tool 3 having a slightly larger prepared hole diameter of the core hole was inserted at 7000 rpm and a feed rate of 200 mm / min to perform inner wall surface processing. It was tested whether the inner wall surface processing tool 3 had toughness, bending strength and impact resistance depending on how much this inner wall surface treatment could be repeated.

  The material of the inner wall surface processing tool 3 is WF-56 manufactured by Sumitomo Electric (a cemented carbide for high-temperature forging with high toughness), AF-1 manufactured by Sumitomo Electric (an ultra-fine grained cemented carbide with excellent bending strength), In the case of NC-16 (coarse WC (tungsten carbide) raw material) manufactured by Daijet Kogyo, the inner wall surface treatment tool 3 was not damaged even when the inner wall surface treatment was repeated 1000 times or more.

  As a comparative example, the inner wall treatment tool 3 is made of an inner wall treatment tool made of high-speed tool steel (SKH), alloy tool steel (SKS, SKD, SKT), and stainless steel (SUS). However, it was found that the inner wall surface processing tool was damaged in 100 times or less, and the durability was inferior to the inner wall surface processing tool 3 of the present invention.

  From this result, it was found that the inner wall surface processing tool 3 of the present invention is excellent in toughness, bending strength and impact resistance.

It is sectional drawing which shows the example of the shape of the hole formed in the casting. It is a figure which shows an example of the processing tool used by this invention. It is a figure which shows the detailed structure of a tool. It is a figure which shows the state which inserted the tool in the hole (cast hole). It is sectional drawing of the hole which shows the modification of the metal structure | tissue which processed the present invention. It is a correlation diagram which shows the relationship between a tool rotation speed and a feed rate. It is sectional drawing which shows the positional relationship with the oil path at the time of processing a screw to a casting. It is a figure which shows the other example of a tool. It is a figure which shows the other example of a tool. It is a metal structure figure (photograph) which shows the effect of this invention. It is a metal structure figure (photograph) which shows the effect of this invention. It is a metal structure figure (photograph) of a die-cast base material. It is a figure which shows the state which inserted the tool in the hole which does not have a bottom part.

Explanation of symbols

1 Casting 2 Hole (Cast hole)
3 Inner wall surface processing tool 21 Bottom 22 Inner wall 22A Modified layer 5 Oil passage

Claims (8)

  An inner wall surface processing tool characterized by having a rod-like structure with a circular cross section and having an insertion portion for insertion into a casting hole of a casting and a base end portion for supporting the insertion portion.   The inner wall surface processing tool according to claim 1, wherein a material of the insertion portion is a cemented carbide for hot forging.   The inner wall surface processing tool according to claim 1, wherein a material of the insertion portion is an ultra-superfine cemented carbide.   The inner wall surface processing tool according to claim 1, wherein the material of the insertion portion is a coarse WC raw material.   The inner wall surface processing tool according to claim 1, wherein the insertion portion has a taper in which a cross-sectional area gradually decreases toward a tip portion.   The inner wall surface processing tool according to claim 1, wherein the tip portion is hemispherical.   The inner wall surface processing tool according to claim 1, wherein the tip end portion is rounded.   The inner wall surface processing tool according to claim 1, wherein the tip portion has a chamfered shape.

Images