JP2005022010A - Vitrified grinding wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vitrified grinding wheel which realizes desirable surface properties in machining a cast iron material or the like by solving a problem of clogging of the vitrified grinding wheel used for honing or superfinishing using a water soluble oil. <P>SOLUTION: The porous vitrified grinding wheel with abrasive grains bonded with a calcinated ceramic bonding material is formed as a vitrified grinding wheel with pores containing organic wax formed of carnauba wax or the like with a fusing point of 75°C or higher, a hardness of 100-120 (Rockwell durometer, test load of 98.1 N, an indication numerical value of dial B (red characters)), a transverse rupture strength of 10-20 MPa and the bending modulus of elasticity of 300-500 kg/mm<SP>2</SP>, preferably for honing or superfinishing using the water soluble cutting oil. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４２】
有機質の天然ワックスは、植物系のカルナウバワックス、石油ワックスはパラフィンワックスまたはマイクロクリスタリンワックスの２種類（日本精蝋社製）とし、合成ワックスは日本精蝋社製のパラフィンワックス、またはクラリアント社製アミド系ワックスまたはポリエチレンワックスの３種類である。無機質ワックスは、いおう（硫黄）を採用した。
【００４３】
表１に示した各種有機質ワックスまたは無機質ワックスの融点は、ホーニングや超仕上げの砥石研削面の温度が約８０〜９５℃になる場合があることから、７５℃以上、より好ましくは８０℃以上のものを選択することが好ましい。
【００４４】
表１に示したいおうの抗折力値が小さい理由は、冷却過経で結晶系が単斜晶から常温の斜方晶に変化し、緻密な固溶体とならないからである。また、有機質ワックスのうち、天然ワックスすなわちカルナウバワックス（カルナウバロウとも呼ばれる）が、無機質いおうの特性値に類似していて好ましい。
【００４５】
石油ワックスは、硬度も軟らかく粘稠性に富み、処理砥石として実削したところ切削性が阻害され、実用化は困難であった。
【００４６】
合成ワックスは、硬くて機械的強度も大きく、融液は高粘度で砥石気孔への充填が容易でなく、さらに処理砥石として実削したところ目詰まり気味で好ましくなかった。
【００４７】
ここで、この発明に用いる天然の有機質ワックスのうち植物系天然ワックスとしては、キャンデリラワックス、カルナウバワックス、木ろう、ライスワックス、パームワックス、オウリキュリーワックス等が挙げられる。
【００４８】
動物系で天然の有機質ワックスとしては、蜜蝋、鯨ろう等が挙げられる。なかでもカルナウバワックスは、融点８０℃以上で動植物ろうの中で最も融点が高く、硬さ、強靭性、微結晶性などで最も優れている。
【００４９】
またワックスは、室温と融点の間にある転移温度で結晶系が変化し、冷却速度によっても変り方が異なるため、砥石処理方法を一定にすることが肝要である。
【００５０】
砥石気孔に充填されたカルナウバワックスの物性値は、抗折力１０〜２０ＭＰａ好ましくは１３〜１５ＭＰａ、曲げ破壊弾性率３００〜５００ｋｇ／ｍｍ^２にあることが必要であり、参考値としては、この発明での測定基準による硬度は、１００〜１２０（ロックウェル硬度計）の範囲にあることが好ましい。
【００５１】
すなわち抗折力で１０ＭＰａ未満、曲げ破壊弾性率３００ｋｇ／ｍｍ^２未満、および硬度１００未満では、ワックスは固体状態で粘調性を増し、切削砥粒の刃先への溶着現象が予想される。
【００５２】
また抗折力２０ＭＰａ、曲げ破壊弾性率５００ｋｇ／ｍｍ^２、硬度１２０をそれぞれ超える値では、砥石作用面に目詰まり現象を誘発することが危惧されるからである。
【００５３】
カルナウバワックスは、脂肪酸エステルからなる、いわゆる油性向上剤であり、砥石作用面での潤滑作用を期待できるものである。
カルナウバワックスの処理方法は、砥石気孔への充填量が最も大きくて安定している条件、すなわち粘性が最小になる１５０℃付近の融液中に２時間以上２５０℃に加熱された砥石を浸し、ワックスを含浸させた後、取出して一定条件で空冷する。
【００５４】
この発明では、ホーニングおよび超仕上げにおいて、カルナウバワックス処理砥石を用い、研摩面に水溶性油を供給しながら研削加工することが適当である。
カルナウバワックス含浸処理砥石と、研摩時の水溶性加工油剤を供給するという組合せにより、砥石は目詰まりすることなく優れた切削性を発揮し、仕上げ比の大きい経済的なホーニング、超仕上げが容易となり、かつクリーンカットにより理想的な表面性状の実現が可能となる。
【００５５】
特にシンセティック水溶性油剤は、油分を乳化させる成分は殆んどなく、カルナウバワックスを乳化させることはない。そのため砥石作用面では、ろう分の撥水作用によりカルナウバワックスの潤滑性能が充分に発揮される。
【００５６】
すなわち、シンセティック水溶性油剤は、鉱物油など油脂分を乳化させる成分を含有せず、水に容易に可溶性の成分から構成されていることが好ましく、例えば構成成分として、脂肪酸石鹸、有機防錆剤、無機防錆剤、潤滑剤および水から成り、起泡性が少なく消泡性、潤滑性、防腐性、防黴性、防錆性に優れ、鉱物油、脂肪油および硫黄・塩素・燐化合物などの極圧添加剤またはシリコンおよび重金属、フェノール類、亜硝酸塩などの含有または添加がなされていないソリューション形シンセティックタイプ水溶性油剤などを挙げることができる。
【００５７】
鋳鉄材料のホーニング面は、材料中のグラファイトが摘出されて表面を覆った状態であり、または摘出後に表面に開孔した状態、圧搾された状態、または圧搾後に摘出され開孔となった状態、または表面に移動して盛上りとなって残存した状態、さらにまた表面のグラファイト部に金属が折り重なっている状態、そして切屑が押込まれた状態や切屑の除去痕などを有する状態である。
【００５８】
理想的なホーニング表面状態は、グラファイトが仕上げ面に顕出もしくは押圧され、または摘出による開孔のない状態、または金属の折り重なりや表面の損傷のない鮮明なクロスハッチパターンの創成された状態である。
【００５９】
このような表面状態の観察は、ホーニング面の転写膜による複写、または加工物を切断によって製作した試料のホーニンク表面を顕微鏡写真によって判断することによる。
【００６０】
次に、この発明に用いる砥粒の種類は、酸化アルミニウム（ＷＡ，Ａ）、炭化けい素（ＧＣ，Ｃ）など、または立方晶窒化ほう素（ＣＢＮ）、ダイヤモンド（ＳＤ）などの超硬砥粒の単種または２種以上からなる。
他方、この発明に用いるカルナウバワックスは、加工油剤である鉱油溶剤に対する溶解性が、いおうよりも少なく安定しているものである。
【００６１】
そして、この発明においてビトリファイド砥石を、水溶性切削油を用いるホーニングまたは超仕上げ加工用のビトリファイド砥石とする場合は、たとえばダイヤモンド砥粒８０／１００メッシュ砥石による粗ホーニング後、また、さらに１７０／２００メッシュ砥石で中仕上げホーニングした表面を、カルナウバワックスを砥石気孔に充填したＧＣ処理砥石でシンセティック水溶性油剤を使用して鋳鉄材料の内面をホーニング加工する。
【００６２】
この結果、有機質ワックスの優れた潤滑性能により、ＧＣ砥石の切削性能はより高められ、水溶性油の使用でも目詰まりや目つぶれをすることなく、低いホーニング抵抗でクリアーなクロスハッチパターンからなるダメージのない理想的な表面仕上げが可能なビトリファイド砥石となる。
【００６３】
また、焼成された砥石に対するワックス処理に伴う切削砥粒の補強効果、および砥石硬度の上昇は、砥石寿命を向上させて、経済的なホーニング加工を達成する。
【００６４】
【実施例および比較例】
ビトリファイド砥石の硬度別に結合剤率、すなわち砥石組織は、実施例と対応する比較対象とする比較例とで一定とし、また気孔率、砥粒率、結合剤率などの体積比が一定となるように、有機質ワックスの含浸処理前のＨＲＨ硬度（ロックウェル硬度計、Ｈスケール）を一定にする条件で実施例および比較例で試験に供する砥石を製造した。
【００６５】
すなわち、緑色炭化けい素（ＧＣ）で粒度は３２０メッシュ（砥粒径４０μｍ、ＪＩＳＲ６００１、電気抵抗試験法）および６００メッシュ（２０μｍ）の砥粒を用い、種々の配合で調製された所定の砥石硬度（Ｊ、Ｌ、Ｍ、Ｎ）の砥石（角形で幅２．５ｍｍ、高さ３ｍｍ、長さ４０ｍｍ）を、溶融したワックスに含浸処理し、その前後のＨＲＨ硬度を測定することにより、砥石結合度の増加の程度を調べ、この結果を表２、３に示した。
【００６６】
製造条件の詳細は、各砥石とも人工気孔剤の大粒子〔平均粒子径５５μｍ〕を単位砥粒量に対し０．０８の一定割合で添加して多孔性とし、小粒子（平均粒子径１２μｍ）を０．０４±０．００５範囲の割合で添加し、成型圧力とともに砥石結合度の微調整を行った。
【００６７】
ビトリファイド結合剤は、化学式で４．６６ＳｉＯ_２、０．５８Ａｌ_２Ｏ_３、１．６８Ｂ_２Ｏ_３、０．１１ＣａＯ、０．１７ＭｇＯ、０．１９Ｋ_２Ｏ、０．５３Ｎａ_２Ｏである。
【００６８】
ＨＲＨ硬度の測定は、ロックウェル硬度計Ｈスケールとし、鋼球圧子３．１７５ｍｍで、試験荷重５８８Ｎ、ダイヤルＢ（赤字）の指示数値とした。
【００６９】
砥石は砥粒、結合剤、気孔剤それに生強度付与剤としての一時的結合剤などを加え均質混合した後、所定の各金型にチャージ成型する。次いで金型から取出し乾燥後、昇温速度３０℃／時、最高温度８７５℃、保持時間３．５時間で焼成後、自然冷却した。そして、角形焼成ブロックから、ホーニング砥石寸法を切り出し整形した。次いで砥石をワックスに含浸処理した。
【００７０】
使用した有機質ワックスは、有機質にカルナウバワックス、無機質としては、いおうを用いた。
有機質ワックスの融液温度は、いおうでは液体状態で粘度が最も小さくなる約１４０℃付近とし、カルナウバワックスでは、充填量が最も大きく安定している条件として、融液の粘性が最小になる１５０℃付近で、それぞれ予熱しておいた砥石をゆっくりと浸漬してゆき、気孔中の空気を追い出しながら有機質ワックスと置換するという自然充填法をとった。その後、液から取り出し空冷した。砥石は処理の前後に、結合度を測定した。
【００７１】
【表２】

【００７２】
【表３】

【００７３】
表２、３の結果からも明らかなように、ＧＣ３２０メッシュ、ビトリフアイドボンド砥石のＨＲＨ硬度は、カルナウバワックスの充填処理後の実施例の砥石は、ＨＲＨ１００未満であるのに対し、いおうを充填処理した同じ硬度の比較例の砥石はＨＲＨ１０３〜１１０の範囲であり、高い結合度上昇率を示した。
【００７４】
なお、単位砥粒量に対する結合剤率は、各砥石硬度別に一定とした。実施例５、６は実施例２、３に比べて摩耗を減少させるため、ＨＲＨ結合度は同じとして結合剤率を高めて砥石臨界圧力を向上させ、同一硬度ながら砥石臨界圧力を大きくした場合の砥石作用をみるようにした。
【００７５】
〔ホーニング実削試験〕
上述のようにして得られた実施例および比較例の砥石を使用し、浜野鉄工製、精密ホーニング盤により、鋳鉄シリンダー内面をホーニング加工し、その性能を調べた。
【００７６】
研削対象は、ＦＣ２５０（ＪＩＳ）、硬さＨＢ２００／２１０、寸法は内径４０ｍｍ、加工長１２０ｍｍとし、その前加工粗さは、ダイヤモンド１８０メッシュメタルボンド砥石により、略１０μｍＲｚに揃えた。取付具型式はリジッド、クランプ圧力１．３２ＭＰａ、アダプター形式はフローティングで砥石拡張方式は、定速切込みとした。
【００７７】
なお、試験には砥石を１セット４本として用い、ホーニング条件は、主軸回転数４８０回／分、ストローク数１４０回／分、切込み速度は直径０．１８ｍｍ／分で総切込み量、直径０．０６４ｍｍ（６４μｍ）とした。なお、交差角（２α）は、２６．３°とした。
【００７８】
ホーニング加工に使用した加工油剤は、不水溶性油剤では、主成分が精製鉱物油、硫黄系極圧添加剤、油性向上剤から成り、代表的性状は粘度（ｃＳｔ，４０℃）５．２、引火点（ＣＯＣ）１５２℃、硫黄分０．５％、油脂分５．０％の低粘度不活性硫化型油剤とした。
【００７９】
水溶性油剤は、主成分として特殊潤滑剤、脂肪酸石鹸、有機防錆剤、無機防錆剤から成り、希釈倍率３０倍で使用した。
【００８０】
代表的性状は、３０倍希釈でＰＨ８．５、表面張力（１０^−３Ｎ／ｍ）３５．５、防錆性（ＦＣ−２０、室温×２４ｈ ｒ）マッチ法（×２０）、チップ法（×３０）ともに変化なし、その他シェル高速四球試験（×３０）（１５０ｋｇ／ｃｍ^２×６００ｒｐｍ×１０ｍｉｍ）摩耗痕径０．７９ｍｍなどである。
【００８１】
表４または表５に、ホーニング実削試験結果を示した。なお、測定項目は、砥石摩耗量（Ｗ）、切削量（Ｔ）、切削除去率（Ｔ％）、ホーニング比（Ｔ／Ｗ）、面粗度（Ｒｚ）およびホーニング抵抗（Ｗａｔｔ）とした。
【００８２】
ホーニング抵抗は、主軸電流計で負荷状況（平均消費電力Ｗａｔｔ）の表示によるものとした。面性状は、ホーニング加工面の顕微鏡観察により、砥石作用面についても、目詰まり状態を調査した。
【００８３】
【表４】

【００８４】
【表５】

【００８５】
表４、５の結果からも明らかなように、水溶性油を使用した実施例の有機質処理砥石は、比較例の無機質処理砥石に比較して、切削性に優れており、Ｔ（％）も大きく設定切込量に対して切残し量が少なかった。特にホーニング抵抗が小さいのが特徴的であった。
【００８６】
この結果、比較例の無機質いおう処理砥石が激しく目詰まりするのに対し、実施例の有機質処理砥石は、カルナウバワックスの潤滑機能が存分に発揮され、またろう分の撥水作用によりクリーンな砥石作用面の持続と無理のない卓越した切削作用により、ダメージの少ない理想的な面性状を得て、鮮明なクロスハッチパターンの形成が可能となった。
【００８７】
また、比較例のいおう処理砥石に比較して、実施例の処理砥石の結合度は軟らかく、砥石摩耗量は多いものの、切削量は約１．５〜２．０倍という優れた切削性能によりホーニング比（Ｔ／Ｗ）もより大きな値となり経済的であった。
【００８８】
その他にも、結合剤率を多くして砥石臨界圧力を高めた実施例５および６は、標準の２および３に比較して、Ｗが少なくなり、Ｔの減少変化も僅かであり、従ってＴ／Ｗは大きな値となり高砥石寿命とすることができた。
【００８９】
また、不水溶性油での実削結果は、有機質処理砥石が無機質処理砥石に比較して、やはり切削性において優れているものの、切削量に対応して面粗度が粗くホーニング抵抗も若干高かった。このため実施例の砥石は、目詰まりはないものの、研削対象の面粗度、面性状は今一つ満足されるものではなく、前述の結果と総合すると、水溶性油により適しているものと認められた。
【００９０】
このように水溶性油を使用して、鋳鉄材料の内面ホーニングを行うと、従来の無機質いおう処理砥石に比較して、確実に１．５〜２．０倍以上の高切削量を得られ、ホーニング比の減少変化もなく経済的であり、かつ約２０％以上も低いホーニング抵抗により、不水溶性油使用よりも細かい面粗度を得て、目詰まりもなくダメージの少ない鮮明なクロスハッチを有する面性状が可能となる。
【００９１】
【発明の効果】
この発明は、以上説明したように、焼成されたセラミック質の結合材でＧＣ砥粒を結合した有気孔ビトリファイド砥石の気孔内に所定の有機質ワックスを保持させたビトリファイド砥石としたので、切屑が気孔へ侵入しにくくなり、目詰まり防止効果、処理剤の特徴を生かした潤滑効果などが奏され、特に水溶性油を使用したホーニング、超仕上げ加工に用いるビトリファイド砥石の目詰まりの問題が解決され、また鋳鉄材料などの加工時に好ましい表面性状を実現可能なビトリファイド砥石になるという利点がある。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vitrified grindstone, and more particularly to a vitrified grindstone applied to honing or superfinishing using a water-soluble oil.
[0002]
[Prior art]
In general, a vitrified grinding wheel is used when a cast iron cylinder such as an automobile part and other parts are subjected to extremely precise polishing such as honing or superfinishing.
[0003]
Vitrified grinding stones are made by mixing general abrasive grains such as alumina and silicon carbide, or abrasives such as super hard diamond and cubic boron nitride with a ceramic binder, and then firing the compression molded body further. is there.
[0004]
When the surface of a ground surface that has been honed with a vitrified grindstone is viewed microscopically, an overlap of the raised edges of the cutting streaks is created, where it acts on the workpiece and acts on the surface by adhesion. It can be observed that a rough surface is created due to the presence of the debris of the fixed work material.
[0005]
In other words, in the honing process of cast iron material, abrasive grains act on the workpiece surface to produce chips, but these chips do not disappear directly or immediately from the processed surface, but on the processed surface. Many of the chips cause residual phenomena such as interference, heavy covering, adhesion, sticking, and deformation, and need to be discharged quickly.
[0006]
The problem of metal residue or folding phenomenon in cast iron cylinder bores has become a primary problem in the manufacture of automobile engines worldwide. This is because, in relation to oil consumption and engine life, the surface structure affects the operating capacity of the cylinder bore and piston ring.
[0007]
Therefore, in order to improve engine life, reliability, and economy, honing of cylinder bores is a surface treatment that has a clear surface appearance and no damage, that is, a clear cross-hatch pattern. Inspected to have a surface that is free of defects such as heavy, damaged, and crushing.
[0008]
Usually, the typical grain size of the diamond wheel used for roughing is 80/100 mesh, but in order to solve the problem after honing due to this wheel, the diamond wheel or silicon carbide particularly excellent in machinability. (GC) A ceramic bond honing stone using fine abrasive grains is used or brush honing is performed, but it is not yet satisfied.
[0009]
By the way, grinding oil (processing oil) is used for grinding together with vitrified grinding stones, and water-insoluble oil and water-soluble oil are known as types of such grinding oil (processing oil).
[0010]
Water-insoluble oils have disadvantages such as poor cooling and easy fire, but due to the uniform adhesion of multi-layer oil film on the chip surface, there is an advantage that chips do not adhere to each other or adhere to the grindstone surface. Dispersion and discharge from the grinding surface are facilitated. In particular, in honing and superfinishing, water-insoluble oils excellent in lubricity, detergency and stability have been used.
[0011]
A water-insoluble oil is a mixed oil that contains a low-viscosity mineral oil as a base oil and a fatty oil (animal and vegetable oil) to improve oiliness and improve the surface finish. An extreme pressure oil containing a sulfur chloride-based extreme pressure additive by effect is selected and blended as a standard, aiming at a stable lubricating effect with respect to various processing conditions.
[0012]
On the other hand, the surface tension (10 ^-3 N / m) is small. When the surface tension is low, the workpiece is wet and the chips are easily separated, so that the grindstone is not easily clogged.
[0013]
However, recently, in addition to streamlining, automation, and unmanned production lines, the type of grinding oil (processing oil) is water-soluble to water-insoluble oil so as to eliminate problems such as grinding environment, global environment or factory fire. There is a growing demand for conversion to natural oils.
[0014]
Water-soluble oils include emulsion type (main components are mineral oil, oily agent, surfactant, inhibitor), soluble type (surfactant, oily agent, inhibitor), solution type / synthetic type (synthetic lubricating oil, interface) Active agents, inhibitors). The surface tension of commercially available water-soluble oils is 30 to 40 (10 ^-3 N / m), and if it is less than 10%, it increases rapidly and becomes a large value.
[0015]
In addition, a porous vitrified grindstone that has been exposed to water-soluble grinding oil (processing oil) for a long time has a problem in that the strength deteriorates. To solve this problem, the inner circumference of the pore is covered with a phenol resin. Means are disclosed (see Patent Document 1).
[0016]
[Patent Document 1]
JP-A-8-276365 (paragraph 0005)
[0017]
[Problems to be solved by the invention]
However, water-soluble oils used for grinding oils (processing oils) with vitrified grinding stones have weak oil film forming ability, and therefore form intermittent, inhomogeneous and insufficient films, resulting in poor permeability and lubricity functions. It is inferior to the case of using water-soluble oil, and in the honing or superfinishing process, the working surface of the grindstone may cause severe clogging.
[0018]
In particular, if a part of the surfactant contained in the water-soluble oil becomes a water-insoluble adhesive and adheres to the surface of the grindstone, the grindstone becomes clogged severely. At this time, the grindstone and the workpiece are generated by surface contact. There is a problem that it becomes difficult to discharge chips.
[0019]
The tendency for chip discharge to be difficult in this way is that the chip to be ground is like a cast iron or ceramic material, but the generated chips are powdery and long flow-type chips are generated like steel materials rather than fine ones. Is more remarkable. Similar clogging is also likely to occur when the pre-processed surface roughness is fine or when the machining allowance is too large.
[0020]
When clogging occurs in the grindstone in this way, the amount of wear on the grindstone will be reduced and the cutting amount will be negligible. As the machining progresses, damage to the work surface due to the growth of the clogged part, or abnormalities due to clogged parts falling off Wear may occur.
[0021]
Accordingly, an object of the present invention is to solve the above-mentioned problems and to solve the problem of clogging during grinding of the vitrified grindstone, and in particular, clogging of the polished surface such as cast iron material using water-soluble oil. A vitrified grindstone that does not cause rusting, and a vitrified grindstone that can realize desirable surface properties by efficient honing and superfinishing.
[0022]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, in a porous vitrified grindstone in which abrasive grains are bonded with a sintered ceramic binder, a hardness of 100 to 120 (with a melting point of 75 ° C. or more in the pores of the grindstone) This is a vitrified grinding wheel characterized by holding an organic wax having a Rockwell hardness tester and a test load of 98.1 N).
[0023]
The organic wax having a melting point of 75 ° C. or higher and a hardness of 100 to 120 (Rockwell hardness tester, test load 98.1 N) held in the pores of the vitrified grindstone of the present invention has a wax (wax) content at the point of action of the cutting abrasive grains. Is gradually supplied from the pores and exhibits water repellency, and exhibits its lubricating performance.
[0024]
As an organic wax having such an action, a bending strength of 10 to 20 MPa and a flexural modulus of 300 to 500 kg / mm are used. ² It is preferable to employ an organic wax, more preferably carnauba wax.
[0025]
By impregnating the dissolved organic wax with the grindstone to fill the grindstone pores with the organic wax, the degree of bond of the grindstone increases and the strength increases. As a result, the critical pressure of the grindstone is increased, and the life of the grindstone is improved by the reinforcing effect of the cutting abrasive grains.
In addition, this treatment makes it difficult for chips to enter the pores, and the grinding efficiency is improved by a clogging prevention effect, a lubrication effect utilizing the characteristics of the treatment agent, and the like.
[0026]
The organic wax has a high melting point with a melting point of 75 ° C. or more, and has an effect of reinforcing the cutting abrasive grains and an appropriate clogging prevention effect unless it is in a molten state during cutting.
[0027]
For this purpose, the type of wax may be selected so that the melting point of the organic wax is 75 ° C. or higher in accordance with the required grinding wheel finishing performance. This is because if the organic wax is melted on the grinding surface of the grindstone as described above, the reinforcing effect of the cutting abrasive grains is completely lost, and only the lubrication effect and the clogging prevention effect are undesirable. Further, the reinforcing effect of the cutting abrasive grains is particularly important in honing which is a heavy cutting action as compared with super finishing.
[0028]
In this way, the grinding wheel exhibits a grinding function without clogging, thereby enabling creation of a cross-hatch pattern that does not damage the work surface.
[0029]
Further, when water-soluble oil is supplied to the grinding surface of the vitrified grinding wheel of the present invention, a high machinability without clogging of the grinding stone becomes possible due to a synergistic action with the excellent lubricating performance of the organic wax.
[0030]
In particular, in honing of cast iron materials, a clean cross hatch pattern and finished surface roughness are obtained by clean-cutting the ridges of the cutting streaks or residual chips on the machined surface caused by rough or semi-finished honing with a diamond wheel. And a more ideal required oil sump surface texture is formed.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
The organic wax in the present invention is a high-melting wax having a melting point of 75 ° C. or higher that does not melt during grinding, and is solid at room temperature and has a hardness of 100 to 120 (Rockwell hardness tester, test load 98.1 N), and a bending strength of 10 ~ 20MPa, flexural modulus 300 ~ 500kg / mm ² It has appropriate hardness and toughness.
[0032]
Incidentally, in order to estimate the temperature near the cutting abrasive grains on the grinding surface of the cutting abrasive grains, grinding is performed using a processing grindstone filled with organic waxes having various melting points, and the degree of reinforcement of organic waxes due to changes in the finishing performance That is, the organic wax melted state is estimated.
[0033]
Various kinds of organic waxes having different melting points used for estimating the grinding temperature in honing and superfinishing are sulfur (melting point: about 119 ° C.), chlorinated paraffin (about 94 ° C.), carnauba wax (about 85 ° C.). ), 130 paraffin (about 55 ° C.), and the like.
[0034]
For example, the amount of wear of a grindstone impregnated with sulfur (melting point 119 ° C.) in super finishing using water-insoluble oil is reduced from about 1/2 to 1/5 compared to a non-treated grindstone. . On the other hand, in the grindstone impregnated with 130 paraffin (melting point 55 ° C.), there is almost no difference in performance with the untreated grindstone, so it is estimated that 130 paraffin will be in the molten state in the ground state.
[0035]
The carnauba wax (melting point 85 ° C.) treated grindstone has a grindstone wear amount of about 1/2 to 1/3 as compared to the untreated grindstone, so it can be estimated that it is probably not in a molten state. As a result, it can be estimated that the grinding temperature in the vicinity of the cutting abrasive grains is between 85 ° C. and 55 ° C. in the superfinishing. In the case of honing, the vicinity of about 90 ° C. can be estimated by the same method.
[0036]
On the other hand, as a problem in manufacturing, in order to fill the grindstone pores with organic wax relatively easily, an organic substance that becomes a low-viscosity liquid when heated at room temperature is a condition, as in the case of inorganic sulfur.
[0037]
Organic waxes that satisfy these various conditions are roughly classified into natural waxes and synthetic waxes. Natural waxes include animal and plant waxes, mineral waxes and petroleum waxes. There are many types of synthetic waxes such as polyethylene and amide.
[0038]
Table 1 shows the characteristic values of various organic waxes. The characteristic value was measured from 3 to 4 samples for one type. The sample used was heated to the melt temperature when impregnating the grindstone pores with organic wax, and naturally cooled to solidify. For example, in the case of an inorganic material, the viscosity becomes the smallest in the state of λ, which is a liquid, and solidifies from a 140 ° C. melt by natural cooling.
[0039]
The hardness is well known by the petroleum wax penetration test method (JIS K2235), but in this invention it was measured with a Rockwell hardness meter.
It should be noted that the sample was too soft to measure on the H scale (indenter 3.175 mm, reference load 98.1 N, test load 588 N) of Rockwell hardness tester with the hardness symbol HRH of a normal fine grinding stone. .175mm steel balls were used, and the indicated value on dial B (in red) was the hardness only with a reference load of 98.1N. When the sample was soft, when the long hand passed the set point of 30 and stopped after passing 0, it was set to a negative (−) value.
[0040]
The bending strength shown in Table 1 is a measured value when the distance between the fulcrums is 30 mm by a two-point support one-point load tester manufactured by Shimadzu Corporation. The flexural fracture modulus was determined by measuring the amount of deflection at the load point when measuring the bending strength.
[0041]
[Table 1]

[0042]
There are two types of organic natural wax: plant-based carnauba wax, petroleum wax: paraffin wax or microcrystalline wax (manufactured by Nippon Seiwa Co., Ltd.), and synthetic wax: paraffin wax manufactured by Nippon Seiwa Co., Ltd. or Clariant There are three types of amide wax or polyethylene wax. As the inorganic wax, sulfur (sulfur) was used.
[0043]
The melting point of various organic waxes or inorganic waxes shown in Table 1 is 75 ° C. or higher, more preferably 80 ° C. or higher because the temperature of the honing or superfinished grinding wheel grinding surface may be about 80-95 ° C. It is preferable to select one.
[0044]
The reason why the bending strength value shown in Table 1 is small is that the crystal system changes from a monoclinic crystal to an orthorhombic crystal at room temperature by cooling, and does not become a dense solid solution. Among organic waxes, natural wax, that is, carnauba wax (also called carnauba wax) is preferable because it is similar to the characteristic value of inorganic sulfur.
[0045]
Petroleum wax is soft and rich in viscosity, and when it was actually cut as a processing grindstone, cutting ability was hindered and practical application was difficult.
[0046]
The synthetic wax is hard and has high mechanical strength, the melt is high in viscosity, and it is not easy to fill the pores of the grindstone.
[0047]
Here, among the natural organic waxes used in the present invention, examples of plant-based natural waxes include candelilla wax, carnauba wax, wax, rice wax, palm wax, and cucumber wax.
[0048]
Examples of natural organic waxes in animal systems include beeswax and whale wax. Among them, carnauba wax has a melting point of 80 ° C. or higher and the highest melting point among animal and plant waxes, and is most excellent in hardness, toughness, microcrystallinity and the like.
[0049]
In addition, since the crystal system of the wax changes at a transition temperature between room temperature and the melting point, and the method of change varies depending on the cooling rate, it is important to make the grinding stone treatment method constant.
[0050]
The physical properties of carnauba wax filled in the pores of the grindstone are a bending strength of 10 to 20 MPa, preferably 13 to 15 MPa, and a bending fracture modulus of 300 to 500 kg / mm. ² As a reference value, the hardness according to the measurement standard in the present invention is preferably in the range of 100 to 120 (Rockwell hardness meter).
[0051]
That is, the bending strength is less than 10 MPa, the bending fracture elastic modulus is 300 kg / mm. ² If the hardness is less than 100 and the hardness is less than 100, the wax increases the viscosity in a solid state, and a welding phenomenon of cutting abrasive grains to the cutting edge is expected.
[0052]
Also, bending strength 20MPa, flexural fracture elastic modulus 500kg / mm ² This is because at values exceeding hardness 120, it is feared that the clogging phenomenon is induced on the grindstone working surface.
[0053]
Carnauba wax is a so-called oiliness improver made of a fatty acid ester and can be expected to have a lubricating action on the grindstone working surface.
The treatment method of carnauba wax is to immerse a grindstone heated to 250 ° C for 2 hours or more in a melt near 150 ° C where the filling amount of the grindstone pores is the largest and stable, that is, the viscosity is minimized. After impregnating with wax, it is taken out and air-cooled under certain conditions.
[0054]
In the present invention, in the honing and superfinishing, it is appropriate to use a carnauba wax-treated grindstone and perform grinding while supplying water-soluble oil to the polished surface.
Combining a carnauba wax impregnated grinding wheel with a water-soluble processing oil during polishing provides excellent cutting performance without clogging, and easy economic honing and super-finishing with a large finish ratio In addition, an ideal surface texture can be realized by clean cutting.
[0055]
In particular, synthetic water-soluble oils have few components that emulsify oil and do not emulsify carnauba wax. Therefore, on the grindstone working surface, the lubrication performance of carnauba wax is sufficiently exhibited by the water repellent effect of the wax.
[0056]
That is, the synthetic water-soluble oil agent does not contain a component for emulsifying fats and oils such as mineral oil, and is preferably composed of a component that is easily soluble in water. For example, as a component, fatty acid soap, organic rust preventive agent , Inorganic rust preventive agent, lubricant and water, low foaming, antifoaming, lubricating, antiseptic, antifungal and antirust properties, mineral oil, fatty oil and sulfur / chlorine / phosphorus compounds Examples include extreme pressure additives such as solution-type synthetic type water-soluble oils which are not contained or added with silicon and heavy metals, phenols, nitrites and the like.
[0057]
The honing surface of the cast iron material is a state in which the graphite in the material is extracted and covers the surface, or a state in which the surface is opened after being extracted, a state in which the surface is squeezed, or a state in which it has been extracted after being squeezed and becomes an open hole, Alternatively, it is in a state where it has moved to the surface and remained swelled, a state in which metal is folded on the graphite portion on the surface, a state in which chips are pushed in, a state in which chips are removed, and the like.
[0058]
The ideal honing surface condition is that the graphite is exposed or pressed on the finished surface, or there is no opening due to extraction, or the creation of a clear cross-hatch pattern without metal folding or surface damage. is there.
[0059]
Observation of such a surface state is based on judging the honking surface of a sample produced by copying a honing surface with a transfer film or cutting a workpiece by a micrograph.
[0060]
Next, the types of abrasive grains used in the present invention are aluminum oxide (WA, A), silicon carbide (GC, C), etc., cemented carbide abrasives such as cubic boron nitride (CBN), diamond (SD), etc. It consists of one kind or two or more kinds of grains.
On the other hand, the carnauba wax used in the present invention is less stable and less soluble than the mineral oil solvent that is a processing oil.
[0061]
In the present invention, when the vitrified grindstone is a honing using a water-soluble cutting oil or a vitrified grindstone for superfinishing, for example, after rough honing with a diamond abrasive 80/100 mesh grindstone, and further 170/200 mesh The inner surface of the cast iron material is honed using a synthetic water-soluble oil with a GC-treated grinding wheel filled with carnauba wax in the grinding stone pores.
[0062]
As a result, the cutting performance of the GC grindstone is further enhanced by the excellent lubrication performance of the organic wax, and the damage consisting of a clear crosshatch pattern with low honing resistance without clogging or clogging even with the use of water-soluble oil. This is a vitrified grinding wheel that can be finished with an ideal surface.
[0063]
Further, the reinforcing effect of the cutting abrasive grains accompanying the wax treatment on the fired grindstone and the increase in the grindstone hardness improve the grindstone life and achieve an economical honing process.
[0064]
Examples and Comparative Examples
The binder ratio according to the hardness of the vitrified grindstone, that is, the grindstone structure, is constant in the comparative example corresponding to the example and the volume ratio such as the porosity, the abrasive grain ratio, the binder ratio is constant. In addition, grindstones used for the tests in the examples and comparative examples were manufactured under the condition that the HRH hardness (Rockwell hardness meter, H scale) before the impregnation treatment with the organic wax was constant.
[0065]
That is, a predetermined grindstone hardness prepared with various compositions using green silicon carbide (GC) with a grain size of 320 mesh (abrasive grain size 40 μm, JIS R6001, electrical resistance test method) and 600 mesh (20 μm). (J, L, M, N) grindstone (square, width 2.5 mm, height 3 mm, length 40 mm) impregnated with molten wax, and measured the HRH hardness before and after that, The degree of increase was examined, and the results are shown in Tables 2 and 3.
[0066]
Details of the production conditions are as follows. For each grindstone, large particles of the artificial pore agent [average particle diameter 55 μm] are added at a constant ratio of 0.08 to the unit abrasive grain amount to make it porous and small particles (average particle diameter 12 μm) Was added at a ratio in the range of 0.04 ± 0.005, and fine adjustment of the bonding degree of the grindstone was performed together with the molding pressure.
[0067]
Vitrified binder has a chemical formula of 4.66SiO. ₂ 0.58Al ₂ O ₃ 1.68B ₂ O ₃ , 0.11CaO, 0.17MgO, 0.19K ₂ O, 0.53Na ₂ O.
[0068]
The HRH hardness was measured using a Rockwell hardness meter H scale, a steel ball indenter of 3.175 mm, a test load of 588 N, and an indicated value of the dial B (red).
[0069]
The grindstone is mixed with abrasive grains, a binder, a pore agent, a temporary binder as a green strength imparting agent, and the like, and then homogeneously mixed, and then charged into predetermined molds. Next, after taking out from the mold and drying, it was fired at a heating rate of 30 ° C./hour, a maximum temperature of 875 ° C. and a holding time of 3.5 hours, and then naturally cooled. And the honing grindstone dimension was cut out and shaped from the square baking block. The grindstone was then impregnated with wax.
[0070]
As the organic wax used, carnauba wax was used as the organic substance, and sulfur was used as the inorganic substance.
The melt temperature of the organic wax is about 140 ° C. where the viscosity is the smallest in the liquid state, and the carnauba wax is the condition where the filling amount is the largest and stable. A natural filling method was adopted in which each preheated grindstone was slowly immersed at around 0 ° C., and organic wax was replaced while expelling air in the pores. Then, it removed from the liquid and air-cooled. The grindstone was measured for bond strength before and after treatment.
[0071]
[Table 2]

[0072]
[Table 3]

[0073]
As is clear from the results in Tables 2 and 3, the HRH hardness of the GC320 mesh, vitrifide bond grindstone is less than HRH100 in the grindstone of the example after the carnauba wax filling treatment. The grindstone of the comparative example of the same hardness which carried out the filling process was the range of HRH103-110, and showed the high increase rate of the bond degree.
[0074]
In addition, the binder ratio with respect to the unit abrasive grain amount was constant for each grindstone hardness. Since Examples 5 and 6 reduce wear compared to Examples 2 and 3, the HRH bond degree is the same, the binder ratio is increased to improve the critical stone pressure, and the critical stone pressure is increased while maintaining the same hardness. The grindstone action was seen.
[0075]
[Honing cutting test]
Using the grindstones of Examples and Comparative Examples obtained as described above, the inner surface of the cast iron cylinder was honed with a precision honing machine manufactured by Hamano Tekko, and the performance was examined.
[0076]
The object to be ground was FC250 (JIS), hardness HB200 / 210, the dimensions were 40 mm inner diameter, the processing length was 120 mm, and the preprocessing roughness was approximately 10 μm Rz with a diamond 180 mesh metal bond grindstone. The fixture type was rigid, the clamping pressure was 1.32 MPa, the adapter type was floating, and the grinding wheel expansion method was constant speed cutting.
[0077]
In the test, four sets of grindstones were used, honing conditions were spindle rotation speed of 480 times / minute, stroke speed of 140 times / minute, cutting speed of 0.18 mm / minute in diameter, total cutting amount, diameter 0. The thickness was 064 mm (64 μm). The crossing angle (2α) was 26.3 °.
[0078]
The processing oil used in the honing process is a water-insoluble oil, and the main components are a refined mineral oil, a sulfur-based extreme pressure additive, and an oil improver, and the typical properties are a viscosity (cSt, 40 ° C.) of 5.2, A low-viscosity inert sulfurized oil having a flash point (COC) of 152 ° C., a sulfur content of 0.5% and an oil and fat content of 5.0% was obtained.
[0079]
The water-soluble oil agent is composed of a special lubricant, a fatty acid soap, an organic rust preventive agent, and an inorganic rust preventive agent as main components, and used at a dilution ratio of 30 times.
[0080]
Typical properties are: pH 8.5 at 30-fold dilution, surface tension (10 ^-3 N / m) 35.5, rust resistance (FC-20, room temperature × 24 hr), match method (× 20), chip method (× 30), no change, other shell high-speed four-ball test (× 30) (150 kg / cm ² × 600 rpm × 10 mim) Wear scar diameter of 0.79 mm.
[0081]
Table 4 or Table 5 shows the results of the honing actual cutting test. The measurement items were grinding wheel wear amount (W), cutting amount (T), cutting removal rate (T%), honing ratio (T / W), surface roughness (Rz), and honing resistance (Watt).
[0082]
The honing resistance was determined by displaying the load status (average power consumption Watt) on the spindle ammeter. As for surface properties, the clogged state of the grindstone working surface was also examined by microscopic observation of the honing surface.
[0083]
[Table 4]

[0084]
[Table 5]

[0085]
As is clear from the results of Tables 4 and 5, the organically treated grindstones of the examples using the water-soluble oil are superior in machinability compared to the inorganic treated grindstones of the comparative examples, and T (%) is also The amount of uncut portion was small relative to the set cutting amount. Particularly, the honing resistance is small.
[0086]
As a result, the inorganic sulfur processing grindstone of the comparative example is clogged violently, whereas the organic processing grindstone of the example exhibits the lubrication function of carnauba wax to a full extent and is clean due to the water repellency of the wax. Due to the continuous grinding wheel surface and the unsurpassed cutting action, ideal surface properties with little damage were obtained, and a clear cross-hatch pattern could be formed.
[0087]
In addition, compared with the sulfur processing grindstone of the comparative example, the degree of bonding of the processing grindstone of the example is soft and the wear amount of the grindstone is large, but the cutting amount is honing due to excellent cutting performance of about 1.5 to 2.0 times. The ratio (T / W) was also large and economical.
[0088]
In addition, Examples 5 and 6 in which the binder ratio was increased and the wheel critical pressure was increased, compared to the standard 2 and 3, the W was smaller and the decrease in T was slight. / W was a large value, and a long grinding wheel life could be achieved.
[0089]
In addition, the results of actual cutting with water-insoluble oil indicate that organically treated grindstones are superior in machinability compared to inorganic treated grindstones, but the surface roughness is rough and the honing resistance is slightly higher corresponding to the amount of cutting. It was. For this reason, although the grindstones of the examples are not clogged, the surface roughness and surface properties of the object to be ground are not yet satisfied, and when combined with the above results, it is recognized that they are more suitable for water-soluble oils. It was.
[0090]
Thus, when water-soluble oil is used and the inner surface honing of the cast iron material is performed, a high cutting amount of 1.5 to 2.0 times or more can be surely obtained as compared with the conventional inorganic sulfur processing grindstone, It is economical with no change in the honing ratio, and it has a surface roughness that is finer than that of water-insoluble oil. It is possible to have surface properties.
[0091]
【The invention's effect】
As described above, the present invention provides a vitrified grindstone in which a predetermined organic wax is held in pores of a porous vitrified grindstone in which GC abrasive grains are bonded with a sintered ceramic binder, so that chips are pores. It prevents the clogging of the vitrified grindstone used for honing and super-finishing processing using water-soluble oil. Further, there is an advantage that a vitrified grindstone capable of realizing a preferable surface property at the time of processing a cast iron material or the like is obtained.

Claims (4)

An organic wax having a porosity of 75 ° C. or higher and a hardness of 100 to 120 (Rockwell hardness tester, test load 98.1 N) in the pores of the grindstone in which the abrasive grains are bonded with a sintered ceramic binder. Vitrified grinding wheel characterized by holding Organic waxes, transverse rupture strength 10 to 20 MPa, flexural vitrified abrasive according to claim 1 which is organic wax modulus 300~500kg / mm ^2. The vitrified grindstone according to claim 1 or 2, wherein the organic wax is carnauba wax. The vitrified grindstone according to any one of claims 1 to 3, wherein the vitrified grindstone is a honing or superfinishing vitrified grindstone using a water-soluble cutting oil.