JP2003096546A - Low thermal expansion alloy for thin casting, and method of producing casting obtained by suing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy for a low thermal expansion casting which has a low thermal expansion coefficient and high dimensional precision, further, has excellent hot cracking properties, and gives a thin casting having high reliability of quality, and to provide a casting method using the alloy. SOLUTION: The low thermal expansion alloy for casting consists of a ferrous alloy containing, by mass, <=0.1% C, 30 to 34% Ni, and 4 to 6% Co, containing 0.0005 to 0.010% Ca and/or Mg, has a low thermal expansion coefficient and high dimensional precision, further, has excellent hot cracking resistance, and gives a thin casting having no cracking defects. In the method, a thin casting having no cracking defects is produced by using the alloy.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【発明の属する技術分野】本発明は、薄肉鋳物用低熱膨
張合金及びこれを用いた薄肉鋳物の製法に関し、殊に、
熱膨張率が小さくて優れた耐熱間割れ性を有し、複雑形
状の薄肉鋳物の製造に好適な低熱膨張合金と、該合金を
用いて寸法精度が高く割れ欠陥のない薄肉鋳物を製造す
る方法に関するものである。TECHNICAL FIELD The present invention relates to a low thermal expansion alloy for thin wall castings and a method for manufacturing thin wall castings using the same, and in particular,
A low thermal expansion alloy having a small thermal expansion coefficient and excellent heat resistance cracking resistance, which is suitable for the production of a thin-walled cast having a complicated shape, and a method for producing a thin-walled cast having high dimensional accuracy and no crack defects using the alloy. It is about.

【０００２】[0002]

【従来の技術】低熱膨張性が要求される用途に用いられ
る代表的な鋳物用合金として、インバーやスーパーイン
バー合金が知られている。これらの鋳物用合金において
は、鋳造後の切削加工を考慮して鋳造時に素材中に球状
黒鉛を生成させ、これにより快削性を与えている。その
ためこの種の合金では、適量の球状黒鉛を生成させるこ
との必要上、合金中に多量のＣ（炭素）を含有させなけ
ればならない。ところがＣを多量に含有させると、マト
リックス内の固溶Ｃ量が増大して熱膨張係数が高まり、
低熱膨張合金としての要求特性を満たし得なくなる。そ
こで、熱膨張係数を下げるための手段として高価なＣｏ
を多量含有させている。2. Description of the Related Art Invar and super Invar alloys are known as typical casting alloys used for applications requiring low thermal expansion. In these casting alloys, spheroidal graphite is generated in the material during casting in consideration of the cutting process after casting, thereby giving free-cutting property. Therefore, in this type of alloy, a large amount of C (carbon) must be contained in the alloy in order to generate an appropriate amount of spheroidal graphite. However, when a large amount of C is contained, the amount of solid solution C in the matrix increases and the thermal expansion coefficient increases,
It becomes impossible to satisfy the required properties as a low thermal expansion alloy. Therefore, expensive Co is used as a means for reducing the coefficient of thermal expansion.
Contains a large amount.

【０００３】しかも、球状黒鉛を含む合金で１．０×１
０‐⁶／℃以下といった低レベルの線膨張係数を確保す
るには、該合金を一旦６００〜９５０℃程度の高温に加
熱することによって、マトリックス内に過飽和に固溶し
ているＣを微細黒鉛として析出させ、しかも、マトリッ
クス中の固溶Ｃ濃度を低下させるために急冷しなければ
ならない。ところが、一般に部品部位によって大きな肉
厚差を有する薄肉鋳物を上記の如く高温に加熱してから
急冷することは、変形を助長して鋳物の寸法精度を低下
させる。Moreover, the alloy containing spheroidal graphite is 1.0 × 1.
0- ⁶ / ° C. such to ensure linear expansion coefficients of the low-level or less, by heating to a high temperature of about once 600 to 950 ° C. The alloy, fine graphite C are dissolved in supersaturation in the matrix And must be quenched to reduce the concentration of solute C in the matrix. However, in general, heating a thin casting having a large difference in wall thickness depending on the parts to a high temperature as described above and then rapidly cooling it promotes deformation and reduces the dimensional accuracy of the casting.

【０００４】加えて、上記の如くＣｏを多量に添加する
と、マルテンサイト変態開始点（Ｍｓ点）が室温近傍に
まで上昇し、寒冷地での輸送時にマルテンサイト変態が
進行してインバー効果を発現し得なくなるので、使用可
能な環境温度が制限され汎用性を欠くものとなる。In addition, when a large amount of Co is added as described above, the martensitic transformation starting point (Ms point) rises to near room temperature, and martensitic transformation progresses during transportation in cold regions to develop the Invar effect. Therefore, the usable environmental temperature is limited and the versatility is lacking.

【０００５】この様に、球状黒鉛を生成させて快削性を
高める従来の鋳物用合金では、Ｃ添加量の増大による線
膨張係数の増大や寸法精度の低下が避けられず、快削性
と低膨張係数の２つの要求特性を同時に満たすことは容
易でない。As described above, in the conventional casting alloys that generate spheroidal graphite to enhance free-cutting property, an increase in the linear expansion coefficient and a decrease in dimensional accuracy due to an increase in the amount of C added are unavoidable. It is not easy to simultaneously satisfy the two required properties of low expansion coefficient.

【０００６】[0006]

【発明が解決しようとする課題】本発明者らは上記の様
な状況の下で、優れた被削性を有すると共に、熱膨張係
数が小さくて寸法精度の高い鋳物を与える快削性低熱膨
張鋳物用合金の開発を期して研究を進めており、先に、 Ｃ：０．１％（特記しない限り質量％を意味する、以
下同じ）以下、Ｎｉ：３０〜３４％、Ｃｏ：４〜６％を
含む鉄基合金に適量のＭｎとＳを含有せしめ、体積分率
で０．０７〜０．２％のＭｎＳを生成させると、優れた
被削性と低熱膨張性を兼ね備えた鋳物が得られること、 該鋳物合金中に他の元素としてＳｉ：０．３〜１．０
％を含有させると鋳造時の湯流れ性が向上し、湯流れ不
良による鋳造欠陥をより効果的に抑えることができるの
で、複雑形状の大型鋳物製造用として好適なものになる
こと、 更に他の元素としてＭｇ，Ｃａ，Ｚｒよりなる群から
選択される少なくとも1種の元素を適量含有させると、
鋳造時の熱間脆化が抑制され、特に薄肉大型鋳物を鋳造
する際の熱間割れがより効果的に抑えられること、を知
り、こうした知見を基に先に特許出願を済ませた。Under the circumstances as described above, the inventors of the present invention have excellent machinability and, at the same time, provide free-cutting, low thermal expansion which gives a casting having a small coefficient of thermal expansion and high dimensional accuracy. Research is proceeding with the development of casting alloys in mind. First, C: 0.1% (meaning mass% unless otherwise specified, the same applies below), Ni: 30 to 34%, Co: 4 to 6 % Of Mn and S to produce an MnS of 0.07 to 0.2% in volume fraction, a cast product having both excellent machinability and low thermal expansion is obtained. That is, Si: 0.3 to 1.0 as another element in the casting alloy.
%, It is possible to improve the flowability of the molten metal during casting and to more effectively suppress the casting defects due to defective molten metal flow, which makes it suitable for the production of large castings of complicated shape. When an appropriate amount of at least one element selected from the group consisting of Mg, Ca and Zr is contained as an element,
We found that hot embrittlement at the time of casting is suppressed, and especially hot cracking at the time of casting a large-sized thin-walled casting can be suppressed more effectively, and based on these findings, we have already filed a patent application.

【０００７】本発明者らはその後も、前述したインバー
やスーパーインバー合金の如き低熱膨張性鋳物用合金の
改質を期して研究を進めており、今回は、特にこれらの
鋳物用合金を用いて薄肉鋳物を鋳造する際にしばしば経
験される熱間割れ防止に主眼を置いて研究を重ねてき
た。従って本発明の目的は、低炭素で且つＮｉとＣｏを
含む鋳物用の低熱膨張鉄基合金を対象とし、特に薄肉鋳
物を鋳造する際にも、肉厚交差部などで熱間割れ等を生
じることのない薄肉鋳物用低熱膨張合金を提供し、併せ
て、該合金を用いて割れ欠陥などのない薄肉鋳物を製造
する方法を提供することにある。[0007] The inventors of the present invention have continued their research with a view to reforming alloys for low thermal expansion castings such as the above-mentioned Invar and Super Invar alloys, and this time, in particular, by using these casting alloys. Research has been focused on preventing hot cracking, which is often experienced when casting thin wall castings. Therefore, an object of the present invention is to target a low thermal expansion iron-based alloy for castings that is low carbon and contains Ni and Co, and particularly when casting a thin casting, causes hot cracking at a wall thickness intersection or the like. It is an object of the present invention to provide a low-thermal-expansion alloy for thin-walled castings that does not have such a problem, and at the same time, to provide a method for producing a thin-walled casting that does not have crack defects using the alloy.

【０００８】[0008]

【課題を解決するための手段】上記課題を解決すること
のできた本発明に係る薄肉鋳物用低熱膨張合金とは、質
量％で、Ｃ：０．１％以下、Ｎｉ：３０〜３４％、Ｃ
ｏ：４〜６％を含む鉄基合金からなり、Ｃａ及び／又は
Ｍｇを合計で０．０００５〜０．０１０％含有するとこ
ろに要旨を有している。The low thermal expansion alloy for thin castings according to the present invention, which has been able to solve the above-mentioned problems, is a mass% of C: 0.1% or less, Ni: 30 to 34%, C:
It consists of an iron-based alloy containing o: 4 to 6%, and has the gist of containing 0.0005 to 0.010% of Ca and / or Mg in total.

【０００９】本発明にかかる該薄肉鋳物用低熱膨張合金
においては、他の元素としてＭｎ：０．５％以下および
Ｓ：０．０２％以下を含有させると、適量のＭｎＳの生
成によって、線膨張係数の増大や熱間脆性の劣化を生じ
ることなく被削性を更に高めることができ、また、更に
他の元素としてＳｉ：０．３〜０．７％を含有させる
と、鋳造時の湯流れ性が向上し、湯流れ不良による鋳造
欠陥をより効果的に抑えることができるので、複雑形状
の薄肉鋳物用として一層好適なものとなる。In the low thermal expansion alloy for thin wall castings according to the present invention, when Mn: 0.5% or less and S: 0.02% or less are contained as other elements, an appropriate amount of MnS is generated to cause linear expansion. Machinability can be further enhanced without increasing the coefficient and deterioration of hot brittleness, and if Si: 0.3 to 0.7% is further contained as another element, the flow of molten metal during casting Since the property is improved and the casting defects due to the poor flow of the molten metal can be suppressed more effectively, it becomes more suitable for thin-walled castings with complicated shapes.

【００１０】また本発明に係る薄肉鋳物の製法とは、上
記化学成分を満たす鋳物用合金を用いて薄肉鋳物を鋳造
する際に、鋳型内の肉厚交差部に冷金を配置して鋳造す
るところに要旨を有している。そしてこの製法を活用す
れば、肉厚交差部における冷却速度の遅延が抑制され
て、非交差部との間の冷却速度差に起因する内部歪みの
発生が防止され、割れの発生が一層確実に防止されると
共に鋳物の寸法精度を一段と高めることが可能となる。Further, the method for producing a thin-walled casting according to the present invention means that when a thin-walled casting is cast using an alloy for casting which satisfies the above chemical composition, cold gold is placed at the crossing portion of the wall thickness in the casting mold. However, it has a gist. If this manufacturing method is utilized, the delay of the cooling rate at the thick crossing portion is suppressed, the internal strain caused by the difference in the cooling rate between the non-crossing portion is prevented from occurring, and the occurrence of cracking is further ensured. In addition to being prevented, it becomes possible to further improve the dimensional accuracy of the casting.

【００１１】[0011]

【発明の実施の形態】本発明者らは前述した様な従来技
術の下で、被削性の向上に球状黒鉛の析出を利用する従
来の快削性低熱膨張鋳物用合金に指摘される問題、殊
に、球状黒鉛を生成するためのＣ量の増大とそれに伴う
マトリックス中のＣ固溶量の増大による熱膨張係数の増
大や寸法精度の低下などを解消し、熱膨張係数が低くて
且つ被削性に優れた鋳物用合金の開発を期して鋭意研究
を進めてきた。BEST MODE FOR CARRYING OUT THE INVENTION The problems pointed out in the conventional free-cutting low thermal expansion casting alloys which utilize the precipitation of spheroidal graphite for improving the machinability under the conventional techniques as described above. In particular, the increase in the amount of C for forming spheroidal graphite and the accompanying increase in the amount of solid solution of C in the matrix eliminates an increase in the coefficient of thermal expansion and a decrease in dimensional accuracy. We have been diligently researching in anticipation of the development of casting alloys with excellent machinability.

【００１２】その結果、インバー合金やスーパーインバ
ー合金に代表されるＮｉやＣｏを含む従来の低熱膨張性
鋳造用合金における、上記熱膨張係数や寸法精度の阻害
要因となるＣ量を低減する一方、球状黒鉛に代わる被削
性改善成分として少量のＭｎとＳを積極的に含有させて
適量のＭｎＳを存在させれば、被削性と低熱膨張という
２つの要求特性を同時に満たす鋳物用合金が得られるこ
とを知り、こうした知見を基に前述した先願発明を完成
した。As a result, in the conventional low thermal expansion casting alloys containing Ni and Co typified by Invar alloys and Super Invar alloys, the amount of C, which is a factor that hinders the above thermal expansion coefficient and dimensional accuracy, is reduced. If a small amount of Mn and S are positively added as a machinability improving component instead of spheroidal graphite and an appropriate amount of MnS is present, a casting alloy that simultaneously satisfies the two requirements of machinability and low thermal expansion can be obtained. Based on such knowledge, the above-mentioned prior invention was completed.

【００１３】他方、前述の如く低炭素で且つＮｉとＣｏ
を含む鋳物用低熱膨張合金を用いて薄肉鋳物を鋳造する
際には、鋳物の薄肉部は溶湯量が少ないため冷却速度が
速くて急冷されるが、肉厚交差部では相対的に溶湯量が
多いため冷却速度は相対的に遅くなる。その結果、肉厚
交差部と非交差部との境界部では該冷却速度差に起因し
て熱歪が生じ易くなり、熱間割れが発生し易くなる。こ
うした傾向は、肉厚非交差部の肉厚が薄くなるほど顕著
に表われてくる。On the other hand, as described above, it has a low carbon content and Ni and Co.
When casting a thin-walled casting using a low thermal expansion alloy for castings containing, the thin-walled portion of the casting has a small amount of molten metal and is rapidly cooled at a high cooling rate. Since there are many, the cooling rate becomes relatively slow. As a result, thermal strain is likely to occur at the boundary between the thick crossing portion and the non-crossing portion due to the cooling rate difference, and hot cracking is likely to occur. Such a tendency becomes more prominent as the thickness of the non-intersecting portion becomes thinner.

【００１４】こうした肉厚交差部と非交差部の境界部に
観察される熱間割れの傾向は、前述した低炭素量で且つ
ＮｉとＣｏを含む低熱膨張鋳物用合金についても同様に
観察される。The tendency of hot cracking observed at the boundary between the thick crossing portion and the non-crossing portion is similarly observed in the low thermal expansion casting alloy having a low carbon content and containing Ni and Co. .

【００１５】そこで、上記低炭素量でＮｉとＣｏを含む
低熱膨張鋳物用合金を対象とし、薄肉鋳物を鋳造する際
に見られる特に熱間割れの改善に主眼を置いて研究を進
めてきた。その結果、低Ｃ量で且つ特定量のＮｉとＣｏ
を含む低熱膨張性の鉄基合金中に少量のＣａ及び／又は
Ｍｇを含有させてやれば、薄肉鋳物を鋳造する際に生じ
がちな熱間割れを可及的に阻止できることを知り、上記
本発明に想到したものである。Therefore, research has been conducted on the alloy for low thermal expansion castings containing Ni and Co in the low carbon content, focusing particularly on the improvement of hot cracking observed when casting a thin casting. As a result, a low C amount and a specific amount of Ni and Co
It was found that if a small amount of Ca and / or Mg is contained in a low thermal expansion iron-based alloy containing, it is possible to prevent hot cracking that tends to occur during casting of a thin casting as much as possible. It was the invention.

【００１６】なお本発明において鋳造対象となる薄肉鋳
物の『薄肉』とは、最小肉厚部の厚さで１０ｍｍ程度以
下、より代表的には８ｍｍ程度以下のものを意図してい
る。最小肉厚の下限値は用途や大きさ等によっても変わ
ってくるので特に制限されないが、実用鋳物として最低
限の強度特性を確保する上では５ｍｍ程度以上とするこ
とが望ましい。In the present invention, the "thin wall" of the thin wall casting to be cast is intended to have a minimum wall thickness of about 10 mm or less, more typically about 8 mm or less. The lower limit of the minimum wall thickness is not particularly limited because it depends on the application, size, etc., but it is preferably about 5 mm or more in order to secure the minimum strength characteristics as a practical casting.

【００１７】以下、本発明において鋳物用合金の化学成
分などを規定した理由を具体的に説明していく。The reasons for defining the chemical composition of the casting alloy in the present invention will be specifically described below.

【００１８】Ｃ：０．１％以下 本発明では、Ｃ量を極力少なく抑えることによって固溶
炭素に起因する線膨張係数の増大を防止すると共に、基
本組成以上にＣｏ量を増加することを回避し、更には、
固溶炭素の析出に要する高温加熱と急冷といった熱処理
を不要とするもので、こうした特徴を活かすにはＣ量を
０．１％以下に抑えなければならず、より好ましくは
０．０５％以下、更に好ましくは０．０２％以下とする
のがよい。ちなみに、Ｃ量が０．１％を超えると、マト
リックス中への固溶炭素量の増大による線膨張係数の増
大が軽視できなくなり、Ｃｏ量を基本組成以上に増大し
なければならなくなって本発明の目的にそぐわなくな
る。C: 0.1% or less In the present invention, the amount of C is kept as small as possible to prevent the linear expansion coefficient from increasing due to the solute carbon, and to avoid increasing the amount of Co beyond the basic composition. And moreover,
It does not require heat treatment such as high temperature heating and rapid cooling required for precipitation of solute carbon, and in order to utilize these characteristics, the C content must be suppressed to 0.1% or less, more preferably 0.05% or less, More preferably, it should be 0.02% or less. By the way, when the amount of C exceeds 0.1%, the increase in the coefficient of linear expansion due to the increase in the amount of solute carbon in the matrix cannot be neglected, and the amount of Co must be increased beyond the basic composition. Will not meet the purpose of.

【００１９】Ｎｉ：３０〜３４％およびＣｏ：４〜６％ Ｎｉは、インバーやスーパーインバーとして開発された
低熱膨張鋳物用合金の熱膨張係数αに最も影響を与える
元素であって、熱膨張係数αで１．０×１０^-6／℃以下
といったレベルの低熱膨張特性を確保するには、Ｎｉ含
量を３０％以上、３４％以下、より好ましくは３１％以
上、３３％以下に設定することが重要であり、この範囲
未満でも又この範囲を超えても、熱膨張率αは著しく増
大してくる。またＣｏ含量は、上記Ｎｉ含量３０〜３４
％との組み合わせにおいて低熱膨張率を確保するため４
％以上、６％以下に設定しなければならず、４％未満も
しくは６％超では、適正Ｎｉ含量の範囲内においても満
足のいく低熱膨張率を確保できなくなる。Ｃｏのより好
ましい含有量は４．５％以上、５．５％以下である。Ni: 30 to 34% and Co: 4 to 6% Ni is an element that most affects the thermal expansion coefficient α of the alloy for low thermal expansion castings developed as Invar or Super Invar, and the thermal expansion coefficient is In order to secure a low thermal expansion property of α of 1.0 × 10 ⁻⁶ / ° C. or less, it is necessary to set the Ni content to 30% or more and 34% or less, more preferably 31% or more and 33% or less. This is important, and the coefficient of thermal expansion α increases remarkably both below this range and above this range. Further, the Co content is the above Ni content of 30 to 34.
% To ensure a low coefficient of thermal expansion in combination with
% Or more and 6% or less. If it is less than 4% or more than 6%, a satisfactory low coefficient of thermal expansion cannot be ensured even within the proper Ni content range. The more preferable content of Co is 4.5% or more and 5.5% or less.

【００２０】Ｃａ及び／又はＭｇ：合計で０．０００５
〜０．０１０％ ＭｇおよびＣａは、薄物鋳物を製造する際の熱間脆性を
高め鋳造時の高温割れを防止する上で欠くことのできな
い元素であり、その効果は極少量、具体的にはＣａ，Ｍ
ｇの一方もしくは双方を総和で０．０００５％以上含有
させることによって有効に発揮され、特に薄肉大型の鋳
物の製造に用いる場合は、総和で０．００１０％以上含
有させることが望ましい。しかし含有量が多くなり過ぎ
ると、合金の線膨張係数が増大傾向を示し寸法精度を低
下させる原因になるので、総和で０．０１０％以下に抑
えねばならない。本発明においては、上記好適含有率を
満たす範囲でＣａとＭｇを併用することが特に好まし
い。Ca and / or Mg: 0.0005 in total
~ 0.010% Mg and Ca are elements indispensable for increasing hot brittleness during production of thin castings and preventing hot cracking during casting, and the effect thereof is extremely small, specifically, Ca, M
When one or both of g is contained in an amount of 0.0005% or more in total, it is effectively exhibited. Particularly when it is used for manufacturing a thin and large-sized casting, it is preferable to add 0.0010% or more in total. However, if the content is too large, the linear expansion coefficient of the alloy tends to increase and the dimensional accuracy is reduced, so the total amount must be kept to 0.010% or less. In the present invention, it is particularly preferable to use Ca and Mg together in a range satisfying the preferable content ratio.

【００２１】本発明に係る薄肉鋳物用低熱膨張合金の必
須構成元素は上記の通りであり、残部成分は実質的にＦ
ｅと不可避不純物であるが、必要によっては、鋳物用合
金として更なる付加的特性を与えるため、下記の元素を
適量含有させることも有効である。The essential constituent elements of the low thermal expansion alloy for thin castings according to the present invention are as described above, and the balance component is substantially F.
Although e is an unavoidable impurity, it is also effective to contain appropriate amounts of the following elements in order to provide further additional properties as a casting alloy, if necessary.

【００２２】Ｍｎ：０．５％以下およびＳ：０．０２％
以下 従来のインバーやスーパーインバーにおいて、Ｍｎは偏
析を生じ易く、しかも熱膨張係数を増大させ、またＳは
偏析して脆化を起こす有害元素として、何れもその含有
は嫌われており、極力少なく抑えることが望ましいとさ
れている。これに対し本発明では、ＭｎとＳを過剰量と
ならない範囲で適量を積極的に含有させ、マトリックス
中に生成するＭｎＳを球状黒鉛に代わる被削性改善成分
として有効に活用することも有効である。こうしたＭｎ
Ｓによる被削性改善効果を実用合金として有効に発揮さ
せるには、Ｍｎを０．２％程度以上、Ｓを０．０１％程
度以上含有させることが望ましい。しかし、Ｍｎ含量が
０．５％を超えると線膨張係数が増大傾向を示す様にな
り、またＳ含量が０．０２％を超えると熱間で脆化し易
くなり、鋳造時に鋳物が高温割れを起こす原因になるの
で、それぞれ上記含量以下に抑えねばならない。Mn: 0.5% or less and S: 0.02%
In the following conventional Invar and Super Invar, Mn tends to cause segregation and further increases the coefficient of thermal expansion, and S is a harmful element which segregates and causes embrittlement. It is said that it is desirable to suppress it. On the other hand, in the present invention, it is also effective to positively contain an appropriate amount of Mn and S in a range that does not result in an excess amount, and effectively utilize MnS generated in the matrix as a machinability improving component instead of spheroidal graphite. is there. Such Mn
In order to effectively exert the machinability improving effect of S as a practical alloy, it is desirable to contain Mn in an amount of about 0.2% or more and S in an amount of about 0.01% or more. However, when the Mn content exceeds 0.5%, the coefficient of linear expansion tends to increase, and when the S content exceeds 0.02%, brittleness tends to occur during hot work, and the casting is subject to high temperature cracking during casting. Each of these must cause the content to fall below the above values.

【００２３】この際、鉄基合金中に含有させるＭｎは、
Ｓ含量に対し当量比で等量以上、即ち質量比で「（Ｍｎ
／54.94）＞（Ｓ／32.06）」を満たす様に両元素の含有
量を制御するのがよい。即ち、Ｓの実質的に全てをＭｎ
Ｓとして固定することにより固溶Ｓ量を極力少なく、好
ましくは実質的にゼロとすることが望ましい。ちなみ
に、ＳがＭｎと結合することなくマトリックス中に固溶
状態で存在すると、熱間での脆化が著しくなり、鋳造時
に熱間割れを起こす原因になるからである。尚、Ｓに対
しＭｎをかなり多めに含有させても固溶Ｓを完全にゼロ
にすることは困難であるので、熱間割れに実質的な悪影
響を及ぼさない限りごく微量の固溶Ｓの存在は許容され
る。At this time, the Mn contained in the iron-based alloy is
Equivalent or more in equivalent ratio with respect to S content, that is, “(Mn
/54.94)>(S/32.06) ”, the contents of both elements should be controlled. That is, substantially all of S is Mn
By fixing as S, it is desirable that the amount of solid solution S be as small as possible, preferably substantially zero. By the way, if S exists in a solid solution state in the matrix without binding to Mn, brittleness during hot becomes remarkable, which causes hot cracking during casting. Since it is difficult to completely eliminate the dissolved S from zero even if Mn is contained in a relatively large amount relative to S, the presence of a very small amount of dissolved S does not substantially affect the hot cracking. Is acceptable.

【００２４】Ｓｉ：０．３〜０．７％ Ｓｉは、鋳造用合金として鋳造時の湯流れ性を高める上
で有効に作用する元素で、特に薄肉且つ複雑で大型の鋳
物製品を鋳造する際の湯流れ不良による鋳造欠陥をなく
すのに有益な元素であり、湯流れ性改善作用を有効に発
揮させるには、Ｓｉ含量を０．３％以上、より好ましく
は０．４％以上含有させることが望ましい。しかし、Ｓ
ｉ含量が多過ぎると、線膨張係数が増大して満足な寸法
精度が得られ難くなるので、多くとも０．７％以下、よ
り好ましくは０．６％以下に抑えるべきである。Si: 0.3 to 0.7% Si is an element which effectively acts as a casting alloy for enhancing the flowability of molten metal during casting, and is particularly useful for casting thin, complex and large casting products. Is an element useful for eliminating casting defects due to poor molten metal flow, and in order to effectively exert the effect of improving molten metal flowability, the Si content should be 0.3% or more, and more preferably 0.4% or more. Is desirable. But S
If the i content is too large, the linear expansion coefficient increases and it becomes difficult to obtain satisfactory dimensional accuracy. Therefore, the content should be 0.7% or less at the most, more preferably 0.6% or less.

【００２５】本発明においては、上記元素以外にも必要
に応じて析出強化作用を有するＡｌ，Ｎｂ，Ｖ，Ｔｉ，
Ｔａなどを、鋳物に求められる要求特性に応じて適量含
有させることができる。In the present invention, in addition to the above elements, if necessary, Al, Nb, V, Ti, which has a precipitation strengthening action,
Ta or the like can be contained in an appropriate amount according to the required characteristics required for casting.

【００２６】また該合金中に不可避的に含まれている元
素のうち、Ｐは微量でも鋳造時の湯流れ性向上に有効に
作用するが、多過ぎると熱間脆性を劣化させて鋳造時に
高温割れを起こす原因になるので、０．１％以下、より
好ましくは０．０２％以下に抑えるべきである。またＰ
以外に混入し得る不可避不純物としてＣｒ，Ｍｏ，Ｃｕ
などが挙げられるが、これらは何れも線膨張係数を高め
る原因になるので、何れもできるだけ少なく抑えること
が望ましい。Of the elements inevitably contained in the alloy, even if a small amount of P is effective for improving the flowability of molten metal during casting, if too much P is added, hot brittleness is deteriorated and high temperature is reached during casting. Since it causes cracking, it should be suppressed to 0.1% or less, more preferably 0.02% or less. Also P
Cr, Mo, Cu as unavoidable impurities that can be mixed in
However, since all of them cause the linear expansion coefficient to be increased, it is desirable to suppress them as much as possible.

【００２７】本発明に係る上記鋳造用合金を溶製するの
に格別特殊な技術は要求されず、常法に従って前記成分
組成を満たす様に配合原料を調整し、高周波溶解炉や電
気炉など任意の溶解炉を用いて加熱溶融すればよいが、
特に基金属となる鉄については、その中に含まれるＣや
Ｍｎ、Ｓ等の量を正確に把握しておき、全溶製原料とし
てのＣ，Ｍｎ，Ｓの各含有量が前述した好適範囲に納ま
る様にコントロールすべきである。また、鉄原料中に不
可避的に含まれていることの多いＳｉやＰについても同
様である。そしてこれら鉄源中に含まれている上記元素
量も踏まえて、これに適量のＮｉやＣｏおよびＣａ，Ｍ
ｇなどを添加すると共に、必要に応じてＭｎやＳなどを
追加し、前述した組成範囲となる様に成分調整すればよ
い。No special special technique is required for melting the above casting alloy according to the present invention, and the blending raw materials are adjusted according to a conventional method so as to satisfy the above component composition, and any high frequency melting furnace or electric furnace may be used. It may be heated and melted using the melting furnace of
Especially for iron as a base metal, the amounts of C, Mn, S, etc. contained therein should be accurately grasped, and the respective contents of C, Mn, S as total melting raw materials should be within the above-mentioned preferred ranges. Should be controlled to fit in. The same applies to Si and P, which are often unavoidably contained in iron raw materials. Then, taking into consideration the above-mentioned amount of elements contained in these iron sources, appropriate amounts of Ni, Co, Ca, and M are added.
In addition to adding g and the like, Mn, S and the like may be added as necessary to adjust the components so that the composition range described above is achieved.

【００２８】また、該鋳造合金を用いて鋳物を製造する
際の鋳造条件も特に限定されないが、好ましくは合金の
液相線温度＋２０℃以上の鋳込み温度で砂型を用いて鋳
造される。この際、本発明の鋳造用合金は前述の如く低
熱膨張性で寸法変化量が少なく熱間脆性の優れたもので
あるから、薄肉で複雑な形状構造を有する大型鋳物であ
っても、鋳造時の冷却凝固過程で熱間割れなどを起こす
ことがなく、また適量のＳｉを含有させたものは湯流れ
性も良好であるから、鋳込み不良による鋳造欠陥を起こ
すこともない。The casting conditions for producing a casting using the casting alloy are not particularly limited, but the casting is preferably performed using a sand mold at a casting temperature of the liquidus temperature of the alloy + 20 ° C. or higher. At this time, since the casting alloy of the present invention has a low thermal expansion property, a small dimensional change amount, and an excellent hot brittleness as described above, even if it is a large casting having a thin wall and a complicated shape structure, No hot cracking occurs in the cooling and solidifying process, and the one containing an appropriate amount of Si has good molten metal flowability, and therefore does not cause casting defects due to defective casting.

【００２９】なお本発明の鋳造用合金は、上記の様に薄
肉鋳物の製造に好ましく使用され、従来合金に比べると
熱間割れを可及的に防止できる。他方、鋳物における肉
厚交差部では肉厚非交差部に比べて溶湯量が多いため、
肉厚非交差部に比べて冷却速度が少なからず遅くなると
共に凝固収縮量は多くなり、肉厚交差部と肉厚非交差部
との境界部で凝固割れを起こす懸念がある。こうした傾
向は、肉厚非交差部の肉厚が薄くて冷却速度の速い薄肉
鋳物ほど顕著に現われる。The casting alloy of the present invention is preferably used for the production of a thin casting as described above, and can prevent hot cracking as much as possible compared with the conventional alloy. On the other hand, since the amount of molten metal at the thick crossing portion in the casting is larger than that at the non-thickness crossing portion,
The cooling rate is not less than that of the non-thickness crossing portion, and the solidification shrinkage amount is large and solidification cracking may occur at the boundary between the thickness crossing portion and the non-thickness crossing portion. Such a tendency is more remarkable in the thin-walled casting having a thinner wall thickness non-intersection portion and a higher cooling rate.

【００３０】本発明の鋳造用合金では、前述した特性か
ら薄肉鋳物の鋳造に適用した場合でも、従来合金に比べ
ると熱間割れ（即ち凝固割れ）を可及的に抑制できる。
しかし、複雑形状の薄肉鋳物を鋳造する場合や鋳造条件
（鋳込み温度のバラツキなど）によっては、前記肉厚交
差部と肉厚非交差部の境界部に生じる凝固速度や凝固収
縮量の差に起因する微細な熱間割れを完全に防止できる
とは限らない。In the casting alloy of the present invention, hot cracking (that is, solidification cracking) can be suppressed as much as possible compared with the conventional alloy even when it is applied to the casting of a thin casting due to the above-mentioned characteristics.
However, when casting a thin-walled casting with a complicated shape or depending on the casting conditions (variation of casting temperature, etc.), it is caused by the difference in solidification rate or solidification shrinkage amount that occurs at the boundary between the thickness intersection and the thickness non-intersection. It is not always possible to completely prevent such fine hot cracking.

【００３１】そこで、上記肉厚交差部と肉厚非交差部の
境界部に生じ得る微細な熱間割れをも完全に防止すべく
更に研究を重ねたところ、鋳型の上記肉厚交差部に冷金
を外部金型として配置して該肉厚交差部の冷却速度を高
めてやれば、該肉厚交差部の冷却速度を肉厚非交差部の
冷却速度に近づけることができ、凝固割れをより確実に
阻止できることが確認された。Therefore, further research was conducted to completely prevent even minute hot cracks that may occur at the boundary between the thick crossing portion and the non-thickness crossing portion. By arranging a metal as an external mold and increasing the cooling rate of the thickness intersection, the cooling rate of the thickness intersection can be made close to the cooling rate of the non-thickness intersection, and solidification cracks It was confirmed that it could be reliably blocked.

【００３２】ここで用いられる冷金の種類は特に制限さ
れないが、コストや割れ防止効果などを総合的に考慮し
て最も実用的なのは炭素鋼である。その形状や寸法、配
置位置なども肉厚交差部の形状や厚さに応じて任意に決
めればよいが、代表的には、例えば図１Ａ〜Ｃに示す如
くキャビティーの肉厚交差部１の一部に接して（好まし
くは肉厚交差部１を取り囲むように）適度の寸法の冷金
２を配置して冷却促進を図ればよい。The type of cold gold used here is not particularly limited, but carbon steel is most practical in view of cost, crack prevention effect and the like. The shape, size, arrangement position and the like may be arbitrarily determined according to the shape and thickness of the thickness intersection, but typically, for example, as shown in FIGS. Cooling gold 2 having an appropriate size may be arranged in contact with a portion (preferably so as to surround the thickness intersection 1) to promote cooling.

【００３３】得られる鋳物は、常法に従って鋳型から脱
型した後、バリ取りや寸法調整のための切削加工や研磨
加工の後、タップやドリルを用いた研削や穿孔、フライ
ス加工などにより最終製品形状に加工されるが、この合
金、中でも適量のＭｎとＳを含有せしめたものは被削性
が良好で切屑処理性にも優れたものであるから、それら
の加工を容易且つ精度良く行なうことができ、自動穿孔
加工装置などを用いて連続加工を行なった場合でも、被
加工部に切屑が溜まって連続加工を阻害したり加工精度
を損なうといった問題を生じることもなく、ロボットな
どを用いた全自動加工にも容易に適用できる。The cast product obtained is removed from the mold according to a conventional method, and then subjected to cutting and polishing for deburring and dimensional adjustment, followed by grinding with a tap or a drill, drilling, milling, etc. Although it is processed into a shape, this alloy, especially those containing appropriate amounts of Mn and S, has good machinability and excellent chip disposability, so it is necessary to easily and accurately process them. Even when performing continuous machining using an automatic drilling machine, etc., a robot etc. was used without causing problems such as chips accumulating on the part to be machined that hinder continuous machining or impair machining accuracy. It can be easily applied to fully automatic processing.

【００３４】本発明の鋳造用合金は上記の様な特性を有
しているので、例えば半導体製造装置用部品や精密機械
加工用部品などの如く、中空部を有する薄肉で複雑形状
の大型鋳物であっても、熱間割れ、特に肉厚交差部と肉
厚非交差部との境界部で微細な凝固割れなどの欠陥を生
じることなく、信頼性の高い薄肉鋳物を製造できる。Since the casting alloy of the present invention has the above-mentioned characteristics, it can be used for thin and complex large-sized castings having a hollow portion, such as parts for semiconductor manufacturing equipment and parts for precision machining. Even if there is any, it is possible to manufacture a highly reliable thin casting without causing hot cracking, particularly defects such as fine solidification cracking at the boundary between the thick crossing portion and the non-thickness crossing portion.

【００３５】[0035]

【実施例】次に実験例を挙げて本発明をより具体的に説
明するが、本発明はもとより下記実験例によって制限を
受けるものではなく、前・後記の趣旨に適合し得る範囲
で適当に変更を加えて実施することも可能であり、それ
らはいずれも本発明の技術的範囲に包含される。EXAMPLES Next, the present invention will be described in more detail with reference to experimental examples. However, the present invention is not limited by the following experimental examples, and may be appropriately applied within a range compatible with the gist of the preceding and the following. Modifications can be made and implemented, and all of them are included in the technical scope of the present invention.

【００３６】実験例 高周波溶解炉を用いて、Ａｒガス雰囲気下で表１に示す
化学成分の鋳物用合金を溶製し、各合金溶湯を用いて、
全体構造が断面Ｌ字状で最小板厚８ｍｍ（図２参照）、
または全体構造がロ字状（図３参照）の薄肉鋳物の鋳造
実験を行なった。得られた各鋳物について、下記の方法
で割れ状況を観察した。結果を表２に示す。Experimental Example Using a high-frequency melting furnace, casting alloys having the chemical components shown in Table 1 were melted under an Ar gas atmosphere, and the molten alloys were used to melt the alloys.
The overall structure is L-shaped in cross section and the minimum plate thickness is 8 mm (see Fig. 2).
Alternatively, a casting experiment of a thin casting having an overall structure of a square shape (see FIG. 3) was conducted. The cracking condition of each of the obtained castings was observed by the following method. The results are shown in Table 2.

【００３７】［割れ率の算出］図４に略示する如く、得
られた鋳物における全肉厚交差部の長さの総和をＨ、肉
厚交差部に生じた全ての亀裂の長さの総和をＣとして求
め、割れ率＝（Ｃ／Ｈ）×１００（％）として算出し
た。ここで肉厚交差部とは、肉厚がＴ字状、Ｌ字状およ
び十字状となっている全ての部分を意味する。[Calculation of cracking ratio] As schematically shown in FIG. 4, the sum of the lengths of all the thickness intersections in the obtained casting is H, and the sum of the lengths of all cracks generated at the thickness intersections. Was calculated as C, and the cracking rate was calculated as (C / H) × 100 (%). Here, the wall thickness intersecting portion means all portions having a wall thickness of T-shape, L-shape and cross shape.

【００３８】[0038]

【表１】 [Table 1]

【００３９】[0039]

【表２】 [Table 2]

【００４０】上記表２に示した符号１，２およびＡ〜Ｇ
で得た各鋳物について、下記の方法で線膨張率を測定し
たところ、符号１，２の鋳物の線膨張率は１．５〜１．
７×１０^-6／℃であったのに対し、符号Ａ〜Ｇの鋳物の
線膨張率は０．７〜０．９×１０^-6／℃であった。Reference numerals 1 and 2 and A to G shown in Table 2 above
The linear expansion coefficient of each of the castings obtained in 1. was measured by the following method.
While it was 7 × 10 ⁻⁶ / ° C., the linear expansion coefficient of the castings with the symbols A to G was 0.7 to 0.9 × 10 ⁻⁶ / ° C.

【００４１】［線膨張率］鋳造した各鋳物を８００℃に
昇温した後１．５時間保持してから水冷し、室温まで十
分に冷却した後、更に３１５℃に昇温して３時間保持
し、その後放冷する。この鋳物から、直径５ｍｍ×長さ
１２ｍｍの円柱の両端面に半径６ｍｍの球面加工を施し
た試験片を切り出し、アルバック理工社製のレーザー熱
膨張計「ＬＩＸ-１」を用いて、Ｈｅガス中で０〜１０
０℃の間を２℃／分の速度で昇温することにより、試験
片１２ｍｍの長手方向に生じる伸び量を測定し、２０℃
から１００℃までの平均線膨張率を算出する。[Linear expansion coefficient] Each of the cast castings was heated to 800 ° C. and held for 1.5 hours, then water-cooled, sufficiently cooled to room temperature, further heated to 315 ° C. and held for 3 hours. And then allow to cool. From this casting, a test piece in which both end surfaces of a cylinder having a diameter of 5 mm and a length of 12 mm were subjected to spherical surface processing with a radius of 6 mm was cut out, and a laser thermal dilatometer "LIX-1" manufactured by ULVAC-RIKO Co., Ltd. was used in He gas. 0-10
By elevating the temperature between 0 ° C at a rate of 2 ° C / min, the elongation amount generated in the longitudinal direction of the test piece 12 mm is measured and is 20 ° C.
The average linear expansion coefficient from 1 to 100 ° C. is calculated.

【００４２】また、上記表１，２に示した符号１，Ｆ，
Ｇの３種の鋳物について、下記の方法で被削性を調べた
ところ、図５〜７に示す結果が得られた。これらの図か
らも明らかな如く、Ｓを多量に含む対照鋳物（符号１：
図５）は優れた被削性を有している。これに対し、符号
Ｇの鋳物はＳ含量が極端に少ないため、図７に示す如く
被削性はかなり劣り、切り子の分断性がよくない。しか
し符号Ｆの鋳物は、少ないながらもやや大目のＳが含ま
れているため、図６に示す如く許容レベルの切り子分断
性が得られており、被削性についても一応満足できる。Further, reference numerals 1, F, and
When the machinability of the three G castings was examined by the following method, the results shown in FIGS. 5 to 7 were obtained. As is clear from these figures, the control casting containing a large amount of S (reference numeral 1:
5) has excellent machinability. On the other hand, since the casting with the code G has an extremely low S content, as shown in FIG. 7, the machinability is considerably poor and the cuttability of the facets is not good. However, since the casting of the code F contains a small amount of slightly large S, as shown in FIG. 6, an acceptable level of facet cutting performance is obtained, and machinability is tentatively satisfied.

【００４３】［被削性］厚さ８ｍｍの平板状試験片の表
面から板の垂直方向に直径４ｍｍのドリルを用いて９８
０回転／ｍｉｎ、刃先送り速度０．０５ｍｍ／回転の条
件で連続１０個の貫通孔を穿ち、その切り粉を採取す
る。そして、該切り粉に認められる毟れ具合と切り粉の
長さで被削性を評価する。毟れ具合が少なく切り粉の長
さの短いものほど被削性良好と判断する。[Machinability] 98 from a surface of a flat plate-shaped test piece having a thickness of 8 mm in a direction perpendicular to the plate by using a drill having a diameter of 4 mm.
10 through-holes are continuously drilled under the conditions of 0 revolutions / min and the blade feed rate of 0.05 mm / revolution, and the chips are collected. Then, the machinability is evaluated based on the degree of damage observed in the cutting powder and the length of the cutting powder. The less machinable and the shorter the length of the cutting chips, the better the machinability.

【００４４】[0044]

【発明の効果】本発明は以上の様に構成されており、低
炭素でかつ適量のＮｉとＣｏを含む低熱膨張鋳物合金に
対し、微量のＣａとＭｇを含有させることによって、薄
肉で複雑な形状・構造の鋳物を製造する際にも、割れ欠
陥がなくて信頼性が高くしかも寸法精度の高い鋳物製品
を与える低熱膨張鋳物用合金を提供すると共に、該合金
を使用し冷金を用いた鋳造法を採用することにより、得
られる薄物鋳物の品質及びその信頼性を一段と高め得る
ことになった。EFFECTS OF THE INVENTION The present invention is configured as described above, and by adding a trace amount of Ca and Mg to a low carbon expansion casting alloy having a low carbon content and containing appropriate amounts of Ni and Co, a thin and complicated structure can be obtained. A low-thermal-expansion casting alloy that does not have cracking defects and is highly reliable and has high dimensional accuracy even when manufacturing a casting of a shape and structure, and using the alloy, cold gold was used. By adopting the casting method, it has become possible to further improve the quality and reliability of the obtained thin casting.

【図面の簡単な説明】[Brief description of drawings]

【図１】冷金の配置例を示す説明図である。FIG. 1 is an explanatory diagram showing an arrangement example of cold gold.

【図２】実験例で得た薄肉鋳物を示す説明図である。FIG. 2 is an explanatory view showing a thin cast product obtained in an experimental example.

【図３】実験例で得た他の薄肉鋳物を示す説明図であ
る。FIG. 3 is an explanatory diagram showing another thin-walled casting obtained in an experimental example.

【図４】肉厚交差部に生じる割れ率の算出法を示す説明
図である。FIG. 4 is an explanatory diagram showing a method of calculating a crack rate that occurs at a thickness intersection.

【図５】実験で得た符号１に係る鋳物の切削性試験で得
た切り子を示す写真である。FIG. 5 is a photograph showing a facet obtained in a machinability test of a casting according to reference numeral 1 obtained in an experiment.

【図６】実験で得た符号Ｆに係る鋳物の切削性試験で得
た切り子を示す写真である。FIG. 6 is a photograph showing a facet obtained in a machinability test of a casting according to the code F obtained in the experiment.

【図７】実験で得た符号Ｇに係る鋳物の切削性試験で得
た切り子を示す写真である。FIG. 7 is a photograph showing a facet obtained in a machinability test of a casting according to code G obtained in an experiment.

Claims (4)

【特許請求の範囲】[Claims] 【請求項１】 質量％で、Ｃ：０．１％以下、Ｎｉ：３
０〜３４％、Ｃｏ：４〜６％を含む鉄基合金からなり、
Ｃａ及び／又はＭｇを合計で０．０００５〜０．０１０
％含有することを特徴とする薄肉鋳物用低熱膨張合金。1. C: 0.1% or less by mass%, Ni: 3
Consisting of an iron-based alloy containing 0 to 34% and Co: 4 to 6%,
0.0005 to 0.010 in total of Ca and / or Mg
%, A low thermal expansion alloy for thin wall castings. 【請求項２】 鉄基合金が、他の元素としてＭｎ：０．
５％以下およびＳ：０．０２％以下を含むものである請
求項１に記載の薄肉鋳物用低熱膨張合金。2. The iron-based alloy contains Mn: 0.
The low thermal expansion alloy for thin wall castings according to claim 1, which contains 5% or less and S: 0.02% or less. 【請求項３】 鉄基合金が、更に他の元素としてＳｉ：
０．３〜０．７％を含むものである請求項１または２に
記載の薄肉鋳物用低熱膨張合金。3. The iron-based alloy further comprises Si:
The low thermal expansion alloy for thin wall castings according to claim 1 or 2, which contains 0.3 to 0.7%. 【請求項４】 請求項１〜３のいずれかに記載の化学成
分を満たす低熱膨張合金を用いて薄肉鋳物を鋳造するに
際し、鋳型内の肉厚交差部に冷金を配置して鋳造するこ
とを特徴とする薄肉鋳物の製法。4. When casting a thin casting using the low thermal expansion alloy satisfying the chemical composition according to any one of claims 1 to 3, arranging cold gold at a crossing portion in the mold for casting. A method for manufacturing thin wall castings.