JP2018051583A - Hot-forging die and method for producing forged product using the same - Google Patents

Hot-forging die and method for producing forged product using the same Download PDF

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JP2018051583A
JP2018051583A JP2016189485A JP2016189485A JP2018051583A JP 2018051583 A JP2018051583 A JP 2018051583A JP 2016189485 A JP2016189485 A JP 2016189485A JP 2016189485 A JP2016189485 A JP 2016189485A JP 2018051583 A JP2018051583 A JP 2018051583A
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coating layer
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JP6784954B2 (en
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翔悟 鈴木
Shogo Suzuki
翔悟 鈴木
友典 上野
Tomonori Ueno
友典 上野
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Proterial Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a hot-forging die that is made of an Ni-based superalloy and resists corrosion caused by a glass lubricant and a method for producing a forged product using the same.SOLUTION: A hot-forging die has a base material having a composition composed of an Ni-based superalloy containing, in mass%, W: 10.3-11.0%, Mo: 9.0-11.0%, and Al: 5.8-6.8%, with the balance being Ni and inevitable impurities. On at least one of a mold face and a side face of the hot-forging die, provided is an oxide coating layer predominantly composed of Si, and between the base material and the oxide coating layer, provided is an aluminum oxide layer of 1.0-5.0 μm in thickness.SELECTED DRAWING: Figure 8

Description

本発明は、優れた耐酸化性を有する熱間鍛造用金型及びそれを用いた鍛造製品の製造方法に関するものである。   The present invention relates to a hot forging die having excellent oxidation resistance and a method for producing a forged product using the same.

耐熱合金からなる製品の鍛造において、鍛造素材は変形抵抗を低くするため加熱される。しかしながら、耐熱合金は高温でも高い強度を有するため、その鍛造に用いる熱間鍛造用金型には高温での高い機械的強度が必要である。
また、熱間鍛造において熱間鍛造用金型の温度が鍛造素材に比べて低い場合、抜熱により鍛造素材の加工性が低下するため、例えばAlloy718やTi合金等の難加工性材からなる製品は、素材とともに熱間鍛造用金型(以下、単に金型と言うことがある)を加熱して鍛造することにより行われる。従って、熱間鍛造用金型は、鍛造素材と同じかもしくはそれに近い高温で、高い機械的強度を有したものでなければならない。この要求を満たす熱間鍛造用金型として、大気中での金型温度1000℃以上の熱間鍛造に使用できるNi基超耐熱合金が提案されている(例えば、特許文献1〜3参照)。
なお、本発明で言う熱間鍛造とは、熱間鍛造用金型の温度を鍛造素材の温度まで近づけるホットダイ鍛造と、鍛造素材と同じ温度にする恒温鍛造を含むものである。
In forging a product made of a heat-resistant alloy, the forging material is heated to reduce deformation resistance. However, since heat-resistant alloys have high strength even at high temperatures, hot forging dies used for forging require high mechanical strength at high temperatures.
Further, in hot forging, when the temperature of the hot forging die is lower than that of the forging material, the workability of the forging material is reduced due to heat removal. Is performed by heating and forging a die for hot forging (hereinafter sometimes simply referred to as a die) together with the material. Therefore, the hot forging die must have a high mechanical strength at a high temperature similar to or close to that of the forging material. As a hot forging die that satisfies this requirement, Ni-based superalloys that can be used for hot forging at a die temperature of 1000 ° C. or higher in the atmosphere have been proposed (see, for example, Patent Documents 1 to 3).
The hot forging referred to in the present invention includes hot die forging in which the temperature of the hot forging die is brought close to the temperature of the forging material and isothermal forging in which the temperature is the same as that of the forging material.

特開昭62−50429号公報JP 62-50429 A 特公昭63−21737号公報Japanese Patent Publication No. 63-21737 米国特許第4740354号明細書U.S. Pat. No. 4,740,354

上述したNi基超耐熱合金は、高温圧縮強度が高いという点では有利である。ところで、前記の難加工性材を熱間鍛造する場合、難加工性材の表面をガラス潤滑剤で被覆して鍛造荷重を低減したり、鍛造素材の温度低下を防止することが行われることがある。ところが、このガラス潤滑剤で上述のNi基超耐熱合金製の熱間鍛造用金型が腐食を起こすと言う問題が判明した。ガラス潤滑によって、熱間鍛造用金型が腐食してしまうと、熱間鍛造用金型の作業面に形成された型彫形状が変化するおそれがあり、このガラス潤滑による腐食を防止することが望まれた。
本発明の目的は、上述したNi基超耐熱合金製の熱間鍛造用金型において、ガラス潤滑剤による腐食を防止した熱間鍛造用金型及びそれを用いた鍛造製品の製造方法を提供することである。
The Ni-base superalloy described above is advantageous in that it has high high temperature compressive strength. By the way, when hot forging the difficult-to-work material, the surface of the difficult-to-work material is coated with a glass lubricant to reduce the forging load or prevent the temperature of the forged material from being lowered. is there. However, it has been found that this glass lubricant causes corrosion of the above-mentioned Ni-based superalloy alloy hot forging die. If the die for hot forging corrodes due to glass lubrication, the engraved shape formed on the work surface of the hot forging die may change, and corrosion due to this glass lubrication can be prevented. Wanted.
An object of the present invention is to provide a hot forging die in which corrosion due to a glass lubricant is prevented and a method for producing a forged product using the same in the above-described Ni-based super heat-resistant alloy die for hot forging. That is.

本発明は上述した課題に鑑みてなされたものである。
すなわち本発明は、質量%で、W:10.3〜11.0%、Mo:9.0〜11.0%、Al:5.8〜6.8%であり、且つ、残部がNi及び不可避的不純物であるNi基超耐熱合金からなる組成を有する基材を備える熱間鍛造用金型であって、
前記熱間鍛造用金型の成形面、側面の少なくとも一方にSiを主成分とする酸化物被覆層を有し、
前記基材と前記酸化物被覆層の間に、厚さ1.0〜5.0μmのアルミ酸化物層を有する熱間鍛造用金型である。
また本発明は、加熱された鍛造素材を上型および下型によって熱間鍛造する鍛造製品の製造方法であって、前記上型及び下型として、前記の熱間鍛造用金型を用いる鍛造製品の製造方法である。
The present invention has been made in view of the above-described problems.
That is, the present invention is mass%, W: 10.3-11.0%, Mo: 9.0-11.0%, Al: 5.8-6.8%, and the balance is Ni and A hot forging die provided with a base material having a composition made of a Ni-based superalloy that is an inevitable impurity,
At least one of the molding surface and the side surface of the hot forging die has an oxide coating layer mainly composed of Si,
A hot forging die having an aluminum oxide layer having a thickness of 1.0 to 5.0 μm between the base material and the oxide coating layer.
The present invention also relates to a method for producing a forged product in which a heated forging material is hot forged with an upper die and a lower die, wherein the forged product uses the hot forging die as the upper die and the lower die. It is a manufacturing method.

本発明の熱間鍛造用金型は、ガラス潤滑剤による腐食を防止することができ、より確実に大気中で難加工性材の熱間鍛造を可能とすることができる。   The hot forging die of the present invention can prevent corrosion due to a glass lubricant, and can more reliably enable hot forging of difficult-to-work materials in the atmosphere.

酸化とそれに伴うスケール飛散を防止する効果を示した外観写真である。It is the external appearance photograph which showed the effect which prevents oxidation and the scale scattering accompanying it. 加熱と冷却の繰り返しに対する耐酸化性の低下の抑制を示した外観写真である。It is the external appearance photograph which showed suppression of the oxidation-resistant fall with respect to repetition of a heating and cooling. 本発明の自己酸化被膜によるアルミ酸化物層を示す電子顕微鏡の反射電子像とAlの元素マップとO(酸素)の元素マップを示す断面写真である。It is a cross-sectional photograph which shows the reflection electron image of the electron microscope which shows the aluminum oxide layer by the self-oxidation film of this invention, the elemental map of Al, and the elemental map of O (oxygen). ガラス潤滑剤による母材の腐食現象を示した外観写真である。It is the external appearance photograph which showed the corrosion phenomenon of the base material by a glass lubricant. 被覆層による腐食の抑制を示した外観写真であるIt is an appearance photograph showing the suppression of corrosion by the coating layer 比較例の反射電子像とAlの元素マップとO(酸素)の元素マップを示す断面写真である。It is a cross-sectional photograph which shows the reflected-electron image of a comparative example, the element map of Al, and the element map of O (oxygen). 本発明例の電子顕微鏡の反射電子像とAlの元素マップとO(酸素)の元素マップを示す断面写真である。It is a cross-sectional photograph which shows the reflected electron image of the electron microscope of the example of this invention, the elemental map of Al, and the elemental map of O (oxygen). 成形面を被覆層で被覆した熱間鍛造用金型の恒温鍛造前後の外観写真である。It is the external appearance photograph before and after the constant temperature forging of the metal mold | die for hot forging which coat | covered the molding surface with the coating layer.

先ず、本発明の熱間鍛造用金型の化学組成について説明する。本発明で規定する下記の合金組成を有するNi基超耐熱合金は、高温圧縮強度が、他の熱間鍛造用金型材料に比べて優れており、大気中で恒温鍛造やホットダイ鍛造等の熱間鍛造が行える。単位は質量%である。
<W:10.3〜11.0%>
Wは、オーステナイトマトリックスに固溶するとともに、析出強化相であるNiAlを基本型とするガンマプライム相にも固溶して合金の高温強度を高める。また、Wは、粒界にWとMoの固溶体からなる体心立方晶のα−(Mo、W)相を晶出し、合金の粒界強度を高めると同時に、合金の被削性を高める作用がある。一方、Wは、耐酸化性を低下させる作用も有し、且つ、11.0%を超えて添加すると割れが発生し易くなる。高温強度を高め、耐酸化性の低下を抑制し、且つ、割れの発生をより抑制する観点から、本発明におけるNi基超耐熱合金中のWの含有量は10.3〜11.0%とする。Wの効果をより確実に得るための好ましい下限は10.4%であり、好ましいWの上限は10.7%である。
First, the chemical composition of the hot forging die of the present invention will be described. The Ni-base superalloy having the following alloy composition defined in the present invention has a high-temperature compressive strength superior to other mold materials for hot forging, and heat such as isothermal forging and hot die forging in the atmosphere. Inter-forging can be performed. The unit is mass%.
<W: 10.3-11.0%>
W forms a solid solution in the austenite matrix and also forms a solid solution in the gamma prime phase based on Ni 3 Al as a precipitation strengthening phase, thereby increasing the high temperature strength of the alloy. In addition, W crystallizes a body-centered cubic α- (Mo, W) phase consisting of a solid solution of W and Mo at the grain boundary, thereby enhancing the grain boundary strength of the alloy and at the same time enhancing the machinability of the alloy. There is. On the other hand, W also has an effect of lowering the oxidation resistance, and if it is added in excess of 11.0%, cracking is likely to occur. The content of W in the Ni-base superalloy in the present invention is 10.3 to 11.0% from the viewpoint of increasing the high temperature strength, suppressing the decrease in oxidation resistance, and further suppressing the occurrence of cracks. To do. The preferable lower limit for obtaining the effect of W more reliably is 10.4%, and the preferable upper limit of W is 10.7%.

<Mo:9.0〜11.0%>
Moは、オーステナイトマトリックスに固溶するとともに、析出強化相であるNiAlを基本型とするガンマプライム相にも固溶して合金の高温強度を高める。一方、Moは、耐酸化性を低下させる作用を有する。高温強度を高め、且つ、耐酸化性の低下をより抑制する観点から、本発明におけるNi基超耐熱合金中のMoの含有量は9.0〜11.0%とする。Moの効果をより確実に得るための好ましい下限は9.5%であり、更に好ましくは9.8%である。また、好ましいMoの上限は10.5%であり、更に好ましくは、10.2%である。
<Mo: 9.0 to 11.0%>
Mo dissolves in the austenite matrix and also dissolves in the gamma prime phase based on Ni 3 Al, which is a precipitation strengthening phase, to increase the high temperature strength of the alloy. On the other hand, Mo has the effect | action which reduces oxidation resistance. From the viewpoint of increasing the high temperature strength and further suppressing the decrease in oxidation resistance, the content of Mo in the Ni-base superalloy according to the present invention is set to 9.0 to 11.0%. A preferable lower limit for obtaining the effect of Mo more reliably is 9.5%, and more preferably 9.8%. Moreover, the upper limit of preferable Mo is 10.5%, More preferably, it is 10.2%.

<Al:5.8〜6.8%>
Alは、Niと結合してNiAlからなるガンマプライム相を析出し、合金の高温強度を高め、合金の表面にアルミナの被覆を生成し、合金に耐酸化性を付与する作用がある。一方、Alの含有量が多過ぎると、共晶ガンマプライム相を過度に生成し、合金の高温強度を低める作用もある。耐酸化性及び高温強度を高める観点から、本発明におけるNi基超耐熱合金中のAlの含有量は5.8〜6.8質量%とする。Alの効果をより確実に得るための好ましい下限は6.0%であり、更に好ましくは6.1%である。また、好ましいAlの上限は6.6%であり、更に好ましくは6.4%である。
<Al: 5.8 to 6.8%>
Al binds to Ni and precipitates a gamma prime phase composed of Ni 3 Al, thereby increasing the high temperature strength of the alloy, forming an alumina coating on the surface of the alloy, and imparting oxidation resistance to the alloy. On the other hand, when the content of Al is too large, an eutectic gamma prime phase is excessively generated, and the high temperature strength of the alloy is lowered. From the viewpoint of enhancing the oxidation resistance and the high temperature strength, the Al content in the Ni-base superalloy according to the present invention is set to 5.8 to 6.8% by mass. A preferable lower limit for obtaining the effect of Al more surely is 6.0%, and more preferably 6.1%. Moreover, the upper limit of preferable Al is 6.6%, More preferably, it is 6.4%.

合金は、基本的に、必須成分であるAl、W、Moと、さらに不可避的不純物を除く残部がNiで構成される。本発明におけるNi基超耐熱合金においてNiはガンマ相を構成する主要元素であるとともに、Al、Mo、Wとともにガンマプライム相を構成する。
本発明におけるNi基超耐熱合金は、不可避的不純物として、Ni、Mo、W、Al以外の成分を含むことができる。
The alloy is basically composed of Al, W, and Mo, which are essential components, and Ni with the remainder excluding inevitable impurities. In the Ni-base superalloy according to the present invention, Ni is a main element constituting a gamma phase and constitutes a gamma prime phase together with Al, Mo and W.
The Ni-base superalloy according to the present invention can contain components other than Ni, Mo, W, and Al as inevitable impurities.

<酸化物被覆層>
本発明では、上記の合金組成を有する熱間鍛造用金型の基材にSiを主成分とする酸化物被覆層を形成する。
上記の合金組成を有する熱間鍛造用金型にSiを主成分とする酸化物被覆層を形成する目的は、スケールの剥離を防止するものである。上述したNi基超耐熱合金は、高温圧縮強度が高いという点では有利であるものの、耐酸化性の点では大気中で加熱した後の冷却時に金型表面から酸化ニッケルの細かなスケールが飛散するため作業環境の劣化及び形状劣化の恐れがあるという問題があった。金型表面の酸化とそれに伴うスケールの飛散の問題は、大気中で使用できるという効果を最大限に生かす上で大きな問題となる。
そこで、熱間鍛造用金型の表面を緻密な保護被膜(被覆層)で覆うことで高温での大気中の酸素と金型母材との直接的な接触を遮断させ、金型表面の酸化を防止するものである。そのため、本発明では、Siを主成分とする酸化物を層状に被覆して酸化物被覆層とし、熱間鍛造用金型の酸化を防止する。
<Oxide coating layer>
In this invention, the oxide coating layer which has Si as a main component is formed in the base material of the metal mold | die for hot forging which has said alloy composition.
The purpose of forming an oxide coating layer containing Si as a main component on a hot forging die having the above alloy composition is to prevent peeling of the scale. The Ni-based superalloy described above is advantageous in that it has a high high temperature compressive strength, but in terms of oxidation resistance, a fine scale of nickel oxide scatters from the mold surface during cooling after heating in the atmosphere. Therefore, there is a problem that there is a risk of deterioration of the working environment and shape. The problem of oxidation of the mold surface and the accompanying scattering of the scale is a big problem in maximizing the effect that it can be used in the atmosphere.
Therefore, by covering the surface of the hot forging die with a dense protective coating (coating layer), direct contact between oxygen in the atmosphere at high temperatures and the die base material is blocked, and the die surface is oxidized. Is to prevent. Therefore, in this invention, the oxide which has Si as a main component is coat | covered in layer shape, and it is set as an oxide coating layer, and prevents the oxidation of the metal for hot forging.

本発明においては、前記酸化物被覆層がSiを主成分とする。この理由は、特に金型表面の酸化を防止する効果が優れているからである。なお、本発明で言うSiを主成分とする酸化物被覆層とは、自己酸化被膜のように、熱間鍛造前の加熱や熱間鍛造中に熱間鍛造用金型の最表面に自然に形成される酸化被膜ではなく、塗布、噴霧、蒸着等により形成されるものを言う。前記の「Si酸化物を主成分とする酸化物被覆層」とは、熱間鍛造工程中に自然に形成される自己酸化被膜以外のものである。なお、前記酸化物被覆層には、所謂ガラス潤滑は含まない。ガラス潤滑剤のような、1回の熱間鍛造でその効果がほぼ損なわれるものは本発明の「酸化物被覆層」には含まない。
また、「主成分」とは、酸化物被覆層を、例えば、エネルギー分散型エックス線分析装置(以下、EDXと記す)にて面分析による定量分析を行ったとき、検出される元素のうち、酸素や窒素などのガス成分を除いた成分の中でSiの割合が最も多いことを言う。ガス成分を除いた定量分析の結果では、おおよそ30質量%以上である。好ましくは50質量%以上である。
なお、Siを主成分とする酸化物被覆層の被覆方法として、例えば蒸着、噴霧、塗布等の方法がある。このうち、塗布や噴霧は、コストの面で有利であり、広範囲にわたってSiを主成分とする酸化物被覆層の形成が可能であることから、好ましい被覆方法である。
In the present invention, the oxide coating layer contains Si as a main component. This is because the effect of preventing oxidation of the mold surface is particularly excellent. In the present invention, the Si-based oxide coating layer is naturally formed on the outermost surface of the hot forging die during heating or hot forging, such as a self-oxidizing film. It refers to what is formed by coating, spraying, vapor deposition, etc., not an oxide film to be formed. The above-mentioned “oxide coating layer containing Si oxide as a main component” is other than the auto-oxidized film naturally formed during the hot forging process. The oxide coating layer does not include so-called glass lubrication. The “oxide coating layer” of the present invention does not include a glass lubricant whose effect is substantially impaired by one hot forging.
In addition, the “main component” refers to an oxygen covering layer that is detected when an oxide coating layer is subjected to quantitative analysis by surface analysis using, for example, an energy dispersive X-ray analyzer (hereinafter referred to as EDX). It means that the ratio of Si is the largest among components excluding gas components such as nitrogen and nitrogen. The result of quantitative analysis excluding gas components is approximately 30% by mass or more. Preferably it is 50 mass% or more.
In addition, as a coating method of the oxide coating layer containing Si as a main component, there are methods such as vapor deposition, spraying, and coating. Among these, coating and spraying are advantageous in terms of cost, and are preferable coating methods because an oxide coating layer mainly composed of Si can be formed over a wide range.

本発明で成形面または側面の何れかまたは両方の表面に無機材料の被覆層を形成するのは、通常、この2つの面が高温の大気雰囲気に曝されるからである。本発明では、成形面と側面の何れかまたは両方に無機材料の被覆層を形成するが、スケール剥離の効果をより確実にするには、成形面と側面の両方に無機材料の被覆層を形成することが良い。なお、本発明で言う「成形面」とは、被鍛造材を熱間鍛造するために被鍛造材を押圧する面を言い、例えば、所謂金敷のようにその表面形状が平坦であっても良いし、型彫り面が形成されていても良い。
本発明において、スケール剥離の効果を更に確実なものとするには、熱間鍛造用金型の全ての面(成形面、側面、底面)に無機材料の被覆層を形成することが好ましい。これにより、高温での大気中の酸素と金型の母材の接触による金型表面の酸化とそれに伴うスケール飛散をより確実に防止し、作業環境の劣化及び形状劣化を防止できる。
The reason why the coating layer of the inorganic material is formed on either or both of the molding surface and the side surface in the present invention is that these two surfaces are usually exposed to a high-temperature atmosphere. In the present invention, an inorganic material coating layer is formed on either or both of the molding surface and the side surface. However, in order to ensure the effect of scale peeling, an inorganic material coating layer is formed on both the molding surface and the side surface. Good to do. The “molding surface” in the present invention refers to a surface that presses the forged material in order to hot forge the material to be forged. For example, the surface shape may be flat like a so-called anvil. However, a mold-sculpted surface may be formed.
In the present invention, in order to further ensure the effect of scale peeling, it is preferable to form a coating layer of an inorganic material on all surfaces (molding surface, side surface, bottom surface) of the hot forging die. Thereby, oxidation of the mold surface due to contact between oxygen in the atmosphere at high temperature and the mold base material and scale scattering associated therewith can be more reliably prevented, and deterioration of the working environment and shape deterioration can be prevented.

<アルミ酸化物層>
本発明では、基材と前記酸化物被覆層の間に、厚さ0.5〜5.0μmのアルミ酸化物層を形成する。前述の酸化物被覆層は、例えば塗布や噴霧によって形成するものであるが、アルミ酸化物層は前記組成を有する金型基材(母材)が含有するAlの自己酸化被膜である。この自己酸化被膜によるアルミ酸化物層を生成させることで、ガラス潤滑剤による金型の腐食を防止する。なお、このアルミ酸化物層は、アルミ酸化物層の欠落部が部分的に存在するような不連続な状態は好ましくなく、連続的に形成されていることが好ましい。
つまり、例えば、鍛造素材にガラス潤滑剤を被覆したときに、前記ガラス潤滑剤によって前記の酸化物被覆層または酸化物被覆層と母材が腐食される現象を生じる場合があるが、その時にAlの自己酸化被膜が母材との界面に存在するとガラス潤滑剤の腐食の進行を妨げるバリア層として機能する。なお、自己酸化被膜の形成には、金型表面に酸化物被覆層を形成した後に予備酸化処理を行うことで形成させることができる。
なお、前記のAlの自己酸化被膜は、例えば、900〜1100℃で3〜5時間の予備酸化を行うことで形成することができる。この予備酸化の条件が熱間鍛造前に行う熱間鍛造用金型の予備加熱の条件と異なる場合は、自己酸化被膜を形成するために特別に予備酸化を行う必要がある。
<Aluminum oxide layer>
In the present invention, an aluminum oxide layer having a thickness of 0.5 to 5.0 μm is formed between the base material and the oxide coating layer. The aforementioned oxide coating layer is formed, for example, by coating or spraying, and the aluminum oxide layer is an Al self-oxidation coating contained in the mold base material (base material) having the above composition. By forming the aluminum oxide layer by this self-oxidized film, the mold is prevented from being corroded by the glass lubricant. The aluminum oxide layer is not preferably in a discontinuous state in which a missing portion of the aluminum oxide layer partially exists, and is preferably formed continuously.
In other words, for example, when a forged material is coated with a glass lubricant, the glass lubricant may cause a phenomenon that the oxide coating layer or the oxide coating layer and the base material are corroded. When the self-oxidized film is present at the interface with the base material, it functions as a barrier layer that hinders the progress of corrosion of the glass lubricant. The self-oxidized film can be formed by performing a preliminary oxidation treatment after forming an oxide coating layer on the mold surface.
The Al self-oxidation film can be formed, for example, by performing preliminary oxidation at 900 to 1100 ° C. for 3 to 5 hours. When the pre-oxidation conditions are different from the pre-heating conditions of the hot forging die performed before hot forging, it is necessary to perform special pre-oxidation in order to form a self-oxidized film.

また、前記のアルミ酸化物層の厚さは、1.0〜5.0μmとする。これは、アルミ酸化物層の厚さが1.0μm未満であるとガラス潤滑剤による腐食の進行を妨げるバリア層として十分な効果が得られない。また、部分的にバリア層としての効果のあるアルミ酸化物層が形成されていない不連続な状態となりやすくなる。不連続なアルミ酸化物層では、ガラス潤滑剤による腐食の進行を妨げるバリア層として十分な効果が得られない。一方、アルミ酸化物層の厚さが5.0μmを超える厚さとしても、バリア層としての効果が飽和し、自己酸化被膜形成に時間がかかるだけである。そのため、アルミ酸化物層の厚さは、1.0〜5.0μmとする。
以上、説明する本発明の熱間鍛造用金型を上型および下型に用いて熱間鍛造すると、例えば、大気中の恒温鍛造であっても、金型表面の酸化とそれに伴うスケールの飛散の問題とガラス潤滑剤による腐食の進行を抑制することが可能である。
Moreover, the thickness of the said aluminum oxide layer shall be 1.0-5.0 micrometers. If the thickness of the aluminum oxide layer is less than 1.0 μm, a sufficient effect as a barrier layer that prevents the progress of corrosion by the glass lubricant cannot be obtained. Moreover, it becomes easy to be in a discontinuous state in which an aluminum oxide layer that is partially effective as a barrier layer is not formed. The discontinuous aluminum oxide layer cannot provide a sufficient effect as a barrier layer that prevents the progress of corrosion by the glass lubricant. On the other hand, even if the thickness of the aluminum oxide layer exceeds 5.0 μm, the effect as a barrier layer is saturated and it takes only a long time to form the self-oxidized film. Therefore, the thickness of the aluminum oxide layer is 1.0 to 5.0 μm.
As described above, when hot forging is performed using the hot forging die of the present invention described above as an upper die and a lower die, for example, even in the constant temperature forging in the atmosphere, oxidation of the die surface and accompanying scale scattering It is possible to suppress the above problem and the progress of corrosion by the glass lubricant.

(実施例1)
以下の実施例で本発明をさらに詳しく説明する。真空溶解にて表1に示すNi基超耐熱合金のインゴットを製造した。なお、作製したインゴットの組成を有する合金は表2に示すような優れた高温圧縮強度の特性を有するものであり、熱間鍛造用金型として十分な特性を有するものである。なお、高温圧縮強度(圧縮耐力)は1100℃で行ったものである。
Example 1
The following examples further illustrate the present invention. Ingots of Ni-base superalloys shown in Table 1 were produced by vacuum melting. The alloy having the composition of the produced ingot has excellent high temperature compressive strength characteristics as shown in Table 2, and has sufficient characteristics as a hot forging die. The high temperature compressive strength (compression strength) was performed at 1100 ° C.

上記のインゴットから直径50mm、高さ10mmの円盤状の試験片を切出し、その試験片の円状の表面の片方を500番相当に研磨した後、研磨面に表3に示すSiを主成分とする酸化物被覆層(以下、酸化物被覆層という)を塗布によって100〜150μm程度形成して試験片を作製した。この試験片を用いて、被覆層の形成による金型の表面の酸化及びスケール飛散の防止効果の評価を行った。今回作製した試験片は、熱間鍛造用金型の応力の加わらない表面を模擬したものである。また、被覆層は円状の表面の片面のみに形成した。なお、エネルギー分散型エックス線分析装置(EDX)にて、酸化物層表面を定量分析した結果、ガス成分を除いた成分の中でSiが50質量%を超えるSiを主成分とする酸化物層であることを確認した。   A disk-shaped test piece having a diameter of 50 mm and a height of 10 mm was cut out from the above ingot, and one of the circular surfaces of the test piece was polished to the equivalent of No. 500, and then the Si shown in Table 3 was mainly contained on the polished surface. A test piece was prepared by forming an oxide coating layer (hereinafter referred to as an oxide coating layer) of about 100 to 150 μm by coating. Using this test piece, the effect of preventing the oxidation of the mold surface and the scattering of the scale due to the formation of the coating layer was evaluated. The test piece produced this time simulates the surface of a hot forging die that is not subjected to stress. Moreover, the coating layer was formed only on one side of the circular surface. As a result of quantitative analysis of the surface of the oxide layer with an energy dispersive X-ray analyzer (EDX), an oxide layer mainly composed of Si with Si exceeding 50% by mass in the components excluding the gas component was obtained. I confirmed that there was.

上記の酸化物被覆層を形成した試験片及び酸化物被覆層を形成しない比較材を用いて、1100℃に加熱された炉に投入し、1100℃にて3時間保持した後炉から取り出して空冷させる加熱試験を行った。加熱試験は、繰り返しの使用による耐酸化性の低下を評価するため、冷却した後再投入することで繰り返し行った。被覆層が完全に剥離した時点でその試験片については試験を中止することとし、最大10回まで繰り返した。なお、用いた比較材は、上記酸化物被覆層を形成した試験片と同形状で、同じ研磨を施したものである。
図1に1回加熱後の試験結果の外観写真を示す。酸化物被覆層を形成しない試験片の表面に黒く写っているのは剥離した細かなスケールである。このことから、酸化物被覆層を形成しない試験片では表面の酸化とそれに伴うスケールの飛散が生じていることがわかる。一方、酸化物被覆層を形成した試験片では、被覆層により表面の酸化が抑制され、評価面における金型の母材の酸化とそれに伴うスケールの飛散が防止されていることがわかる。
図2に加熱試験10回目後の外観写真を示す。酸化物被覆層を形成した試験片では、加熱−冷却を10回繰り返してもスケールの剥離は確認されなかった。一方、酸化物被覆層を形成しない試験片では、1乃至10回目まで、表面の酸化とそれに伴うスケールの飛散が同様に見られた。
図3(a)に酸化物被覆層を形成した試験片の加熱試験10回目後の断面方向から観察したFE−EPMA反射電子像、(b)にAlの元素マップ、(c)にOの元素マップを示す。元素マップ画像における濃淡は測定対象元素の濃度に対応しており、白い程濃度が高い。図3から、母材の被覆層側表面にAlとOが濃化しており、ここにアルミ酸化物層が形成されていることが分かる。このアルミ酸化物層は表3に示す組成の塗料を塗布後1100℃にて3時間の保持中に形成された厚さが1.0〜2.5μmのAlの自己酸化被膜の層である。本発明で規定する層構造となった試験片は優れた耐酸化性を有することが確認された。
Using the test piece having the oxide coating layer and the comparative material not forming the oxide coating layer, the sample was put into a furnace heated to 1100 ° C., held at 1100 ° C. for 3 hours, then taken out of the furnace and air-cooled. A heating test was performed. The heating test was repeated by cooling and re-charging in order to evaluate the decrease in oxidation resistance due to repeated use. When the coating layer was completely peeled off, the test was stopped for the test piece and repeated up to 10 times. In addition, the used comparative material is the same shape as the test piece in which the said oxide coating layer was formed, and gave the same grinding | polishing.
FIG. 1 shows a photograph of the appearance of the test result after heating once. The black scale on the surface of the test piece on which the oxide coating layer is not formed is a peeled fine scale. From this, it can be seen that in the test piece in which the oxide coating layer is not formed, surface oxidation and accompanying scale scattering occur. On the other hand, in the test piece in which the oxide coating layer is formed, it can be seen that the coating layer suppresses the oxidation of the surface and prevents the oxidation of the mold base material on the evaluation surface and the accompanying scattering of the scale.
FIG. 2 shows an appearance photograph after the 10th heating test. In the test piece on which the oxide coating layer was formed, no peeling of the scale was confirmed even when heating and cooling were repeated 10 times. On the other hand, in the test piece in which the oxide coating layer was not formed, the oxidation of the surface and the accompanying scattering of the scale were similarly observed from the 1st to the 10th time.
FIG. 3A shows an FE-EPMA reflected electron image observed from the cross-sectional direction after the 10th heating test of the test piece on which the oxide coating layer is formed, FIG. 3B shows an Al element map, and FIG. 3C shows an O element. Show the map. The shading in the element map image corresponds to the concentration of the element to be measured, and the whiter the concentration is. FIG. 3 shows that Al and O are concentrated on the surface of the base material on the coating layer side, and an aluminum oxide layer is formed here. This aluminum oxide layer is a layer of an Al self-oxidation film having a thickness of 1.0 to 2.5 μm formed during application for 3 hours at 1100 ° C. after applying a paint having the composition shown in Table 3. It was confirmed that the test piece having the layer structure defined in the present invention has excellent oxidation resistance.

(実施例2)
次にガラス潤滑剤による母材の腐食を確認実験した。
酸化物被覆層を形成させた熱間鍛造金型を用いてガラス潤滑剤を被覆した被鍛造材を鍛造するとき、前記ガラス潤滑剤によって酸化物被覆層または酸化物被覆層と母材が腐食される現象を生じる場合がある。
まず、ガラス潤滑剤により母材が腐食される現象を評価するため、前記比較材と同様に加工した試料上の中心付近に400〜500mgのガラス潤滑剤を塗布した試験片を3個作製した。作製した試験片を加熱された炉に投入し、3時間保持した後炉から取り出して空冷させる加熱試験を、実機において想定される温度である900、1000、1100℃に対して各1回行った。なお、加熱試験における雰囲気は大気とし、本試験以降の試験の雰囲気も全て大気である。表4に使用したガラス潤滑剤の組成を示す。
図4(a)に900℃加熱試験前、(d)に900℃加熱試験後の試料の写真を示す。また、図4(b)に1000℃加熱試験前、(e)に1000℃加熱試験後、(c)に1100℃加熱試験前、(f)に1100℃加熱試験後の試料の写真を示す。900、1000、1100℃全てにおいて前記ガラス潤滑剤による母材の腐食が起こっており、温度の上昇に伴い反応が激しくなっていることが分かる。
(Example 2)
Next, an experiment was conducted to confirm the corrosion of the base material by the glass lubricant.
When forging a forged material coated with a glass lubricant using a hot forging die formed with an oxide coating layer, the glass coating agent corrodes the oxide coating layer or the oxide coating layer and the base material. May occur.
First, in order to evaluate the phenomenon that the base material is corroded by the glass lubricant, three test pieces were prepared in which 400 to 500 mg of glass lubricant was applied in the vicinity of the center on the sample processed in the same manner as the comparative material. The prepared test piece was put into a heated furnace, held for 3 hours, and then taken out from the furnace and air-cooled, and a heating test was performed once for 900, 1000, and 1100 ° C., which are temperatures assumed in an actual machine. . Note that the atmosphere in the heating test is air, and all the atmospheres in the tests after this test are also air. Table 4 shows the composition of the glass lubricant used.
FIG. 4A shows a photograph of the sample before the 900 ° C. heating test, and FIG. 4D shows the sample after the 900 ° C. heating test. FIG. 4B shows a photograph of the sample before the 1000 ° C. heat test, (e) after the 1000 ° C. heat test, (c) before the 1100 ° C. heat test, and (f) after the 1100 ° C. heat test. It can be seen that the base metal is corroded by the glass lubricant at 900, 1000 and 1100 ° C., and the reaction becomes more intense as the temperature rises.

次に、本発明で規定する層構造を有する熱間鍛造金型における前記腐食現象を評価するために、前記実施例1の試験片と同様に準備した試験片に予備酸化処理を施した後、被覆層上の試験片の中心付近に表4に示す組成を有するガラス潤滑剤を400〜500mg塗布した試験片を作製した。この試験片は、本発明で規定する層構造を有する熱間鍛造金型を用いて熱間鍛造する場合に、ガラス潤滑剤が金型の作業面(型彫り面)に残存した状態を模擬したものである。この試験片を用いて、最もガラス潤滑による腐食が激しかった1100℃に加熱された炉に投入し、1100℃にて3時間保持した後炉から取り出して空冷させる加熱試験を1回行った。表5に前記試験片の予備酸化処理の熱処理条件と酸化物被覆層の膜厚を示す。   Next, in order to evaluate the corrosion phenomenon in the hot forging die having the layer structure defined in the present invention, after subjecting the test piece prepared in the same manner as the test piece of Example 1 to pre-oxidation treatment, A test piece was prepared by applying 400 to 500 mg of a glass lubricant having the composition shown in Table 4 near the center of the test piece on the coating layer. This test piece simulated the state in which the glass lubricant remained on the working surface (die-sculpture surface) of the die when hot forging using a hot forging die having a layer structure defined in the present invention. Is. Using this test piece, a heating test was performed once in which it was put into a furnace heated to 1100 ° C. where corrosion due to glass lubrication was most intense, held at 1100 ° C. for 3 hours, and then taken out from the furnace and air-cooled. Table 5 shows the heat treatment conditions for the preliminary oxidation treatment of the test piece and the film thickness of the oxide coating layer.

図5(a)にNo.Aの加熱試験前、(c)に加熱試験後の写真を示す。また、図5(b)にNo.Bの加熱試験前、図5(d)に加熱試験後の写真を示す。No.Aでは前記ガラス潤滑剤による被覆層と母材の腐食が生じている一方、No.Bの試験片では腐食が完全に抑制されていることが分かる。
図6(a)にNo.Aの予備酸化後の被覆層と母材を樹脂に埋め込んで鏡面研磨した後、断面方向から観察したFE−EPMA反射電子像、(b)にAlの元素マップ、(c)にOの元素マップを示す。また、図7(a)〜(c)に、同様に観察したNo.Bの観察結果を示す。
No.Aではアルミ酸化物層の厚さが0.5μm程度と薄く、ガラス潤滑剤の腐食バリア層としては不十分であった。一方、No.Bでは厚さが1.0〜2.5μmのAlの自己酸化被膜によるアルミ酸化物層が形成されて本発明で規定する層構造となっていることが分かる。No.Bの試験片はガラス潤滑剤による腐食を防止可能なことが確認された。
In FIG. Before the heating test of A, (c) shows a photograph after the heating test. Further, in FIG. A photograph after the heating test is shown in FIG. No. In A, the coating layer and the base material were corroded by the glass lubricant. It can be seen that the corrosion test is completely suppressed in the test piece of B.
In FIG. FE-EPMA reflected electron image observed from the cross-sectional direction after embedding the coating layer and base material after pre-oxidation of A in a resin and mirror polishing, (b) element map of Al, (c) element map of O Indicates. In addition, in FIGS. The observation result of B is shown.
No. In A, the thickness of the aluminum oxide layer was as thin as about 0.5 μm, which was insufficient as a corrosion barrier layer for the glass lubricant. On the other hand, no. In B, it can be seen that an aluminum oxide layer made of Al self-oxidized film having a thickness of 1.0 to 2.5 μm is formed to have a layer structure defined in the present invention. No. It was confirmed that the test piece B could prevent corrosion by the glass lubricant.

(実施例3)
基材として、表6に示す組成を有し、表3に示す酸化物被覆層を、成形面(作業面)に形成し直径300mm、高さ100mmの金型を用いて、酸化物被覆層の酸化及びスケール飛散の防止効果と前記ガラス潤滑剤による腐食抑制効果の評価を行った。
(Example 3)
As a base material, it has the composition shown in Table 6, and the oxide coating layer shown in Table 3 is formed on the molding surface (working surface) and a mold having a diameter of 300 mm and a height of 100 mm is used. The prevention effect of oxidation and scale scattering and the corrosion inhibition effect by the glass lubricant were evaluated.

評価は、金型と鍛造素材を共に980℃に加熱した恒温鍛造とした。鍛造素材にはNi基合金を、潤滑剤には表4に示すガラス潤滑剤を用い、金型の成形面に最大約150MPaの応力が加わる恒温鍛造を2回行った。鍛造前の予備酸化は、900℃1時間保持後、更に980℃1時間保持である。
図8(a)に酸化物被覆層となるSiを主成分とする酸化物の塗料を塗布後の金型の成形面の写真を、図8(b)に前記恒温鍛造後の金型の成形面の写真を示す。金型の成形面に形成した酸化物被覆層は、前記恒温鍛造により型彫り面内にわずかな剥離部分が確認されたものの、十分に被覆層が維持されていることがわかる。また、成形面のほぼ全てにおいて金型母材の酸化とそれに伴うスケールの飛散が防止されるとともに、前記ガラス潤滑剤による腐食が抑制されていることがわかる。
The evaluation was constant temperature forging in which both the mold and the forging material were heated to 980 ° C. A Ni-based alloy was used as the forging material, and a glass lubricant shown in Table 4 was used as the lubricant, and isothermal forging in which a stress of about 150 MPa at the maximum was applied to the molding surface of the mold was performed twice. The pre-oxidation before forging is held at 980 ° C. for 1 hour after holding at 900 ° C. for 1 hour.
Fig. 8 (a) shows a photograph of the molding surface of the mold after the application of an oxide paint mainly composed of Si as an oxide coating layer, and Fig. 8 (b) shows the molding of the mold after the isothermal forging. A photograph of the surface is shown. It can be seen that the oxide coating layer formed on the molding surface of the mold was sufficiently maintained even though a slight peeling portion was confirmed in the mold carved surface by the constant temperature forging. Further, it can be seen that oxidation of the mold base material and the accompanying scattering of the scale are prevented on almost all the molding surfaces, and corrosion by the glass lubricant is suppressed.

以上の結果から、本発明の層構造を有する熱間鍛造用金型は、加熱と冷却とを繰返しても耐酸化性が高く金型表面の酸化とそれに伴うスケールの飛散を防止でき、更に、ガラス潤滑剤による金型の腐食を防止可能なことが確認された。
このことから、ガラス潤滑を必要とする難加工性材の熱間(恒温)鍛造において、より確実に大気中での熱間鍛造を可能とすることができる。
From the above results, the hot forging die having the layer structure of the present invention has high oxidation resistance even when heating and cooling are repeated, and can prevent oxidation of the die surface and accompanying scale scattering. It was confirmed that the mold could be prevented from being corroded by the glass lubricant.
From this, in the hot (constant temperature) forging of difficult-to-work materials that require glass lubrication, it is possible to more reliably perform hot forging in the atmosphere.

Claims (2)

質量%で、W:10.3〜11.0%、Mo:9.0〜11.0%、Al:5.8〜6.8%であり、且つ、残部がNi及び不可避的不純物であるNi基超耐熱合金からなる組成を有する基材を備える熱間鍛造用金型であって、
前記熱間鍛造用金型の成形面、側面の少なくとも一方にSiを主成分とする酸化物被覆層を有し、
前記基材と前記酸化物被覆層の間に、厚さ1.0〜5.0μmのアルミ酸化物層を有することを特徴とする熱間鍛造用金型。
In mass%, W: 10.3-11.0%, Mo: 9.0-11.0%, Al: 5.8-6.8%, and the balance is Ni and inevitable impurities A hot forging die including a base material having a composition made of a Ni-base superalloy,
At least one of the molding surface and the side surface of the hot forging die has an oxide coating layer mainly composed of Si,
A hot forging die having an aluminum oxide layer having a thickness of 1.0 to 5.0 μm between the base material and the oxide coating layer.
加熱された鍛造素材を上型および下型によって熱間鍛造する鍛造製品の製造方法であって、前記上型及び下型として、請求項1に記載の熱間鍛造用金型を用いる鍛造製品の製造方法。

A forged product manufacturing method for hot forging a heated forging material with an upper die and a lower die, wherein the forged product uses the hot forging die according to claim 1 as the upper die and the lower die. Production method.

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