JP3894601B2 - Hot processing method for metal materials - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、鋼材や合金材料を、スケ−ル生成が伴う温度に加熱して行う各種の熱間処理を、酸化による表面品質の劣化を僅少に留めて行う方法に関する。
【０００２】
【従来の技術】
上記熱間処理の代表的なものとして、鋼材などの熱処理とＮｉ基自溶性合金などの溶射層の再溶融処理を例示できる。しかして、後者については、表面改質手段である溶射の最終工程に当るものであることから、スケ−ル，粒界酸化，クラック，表層部の変質，表面硬度と云った溶射層の品質に及ぼす影響が大である。ついては、以下の説明を、溶射層の再溶融処理を例にとって行うこととするが、本発明方法は上記処理に限定されるものではない。
【０００３】
再溶融処理の対象となる溶射層の代表的なものは、Ｃｒ，Ｍｏ等を配合したＮｉ基あるいはＣｏ基の合金材料であり、通常は、再溶融処理のためのフラックス形成成分となるＢ及びＳｉを添加した自溶性合金材料が用いられる。
【０００４】
これらの合金の再溶融処理の温度は、多くは1000〜1100℃の範囲にあり、この加熱によってＣｒ等の酸化が激しく進む。前記自溶性合金にあっては、フラックス形成により、上記酸化は大巾に軽減されるが、金属光沢を保持するという高度の要請迄を満たすには至らない。よって、このような高度の要請に対しては雰囲気炉の利用あるいは、研摩精整を前提としたマ−ジンの設定を要することになる。
【０００５】
一方、熱間処理の際の酸化を軽減するために酸化防止剤を塗布する方法が知られており、酸化防止剤として、ホウ酸系，水ガラス系など各種のものが提唱されている。本願の発明者らも自溶性合金材料の再溶融処理を、処理後の除去の問題が少ないホウ酸系酸化防止剤であるホウ砂を塗布して行ってみたが顕著には改善されなかった。しかして、塗布した酸化防止剤は、溶融した形跡が認められるものの、その下に緑色のスケ−ルが薄く生成していた。
【０００６】
この原因としては次のような事情が考えられた。即ち、ホウ酸系酸化防止剤は基本成分として水和酸化ホウ素（ホウ酸）あるいはその塩類を含んでおり、これが溶融してガラス状の膜を形成し、酸素等を遮断して酸化防止機能を発現するものであるが、加熱途上の脱水反応によって融点が上昇して行くという性質がある。たとえば酸化ホウ素と水とが１：１のモル比で結合した水和酸化ホウ素であるメタホウ酸の融点は200℃強であるが、無水状態迄脱水された酸化ホウ素の融点は450℃強である。又、四ホウ酸ナトリウムの10モル水和物であるホウ砂の融点は75℃であるが、350℃以上の温度で無水物迄脱水されて、800℃前後の融点に落着く。
【０００７】
即ち、ホウ酸系の酸化防止剤を塗布した金属材料を加熱する場合に、ゆっくり昇温させると、系の温度が塗布剤の融点に到達して塗布剤が溶融するよりも先に、塗布剤の脱水反応が進んで融点の方が上昇して行き、この間、塗布剤の溶融は起りえない。しかして、このあと、無水物迄脱水されて融点が一定値に落着き、且つ、系がこの温度に到達してはじめて溶融が始まり、膜を形成できることになる。即ち、昇温速度が小であると、酸化防止機能が発現されない温度域が生じうる。しかるに、相当量のＣｒが配合されている自溶性合金材料は600℃前後から酸化が大となってスケ−ルが生成し始めるため、前述のように顕著な改善につながらなかったという事情である。このような事情は、200℃台でスケ−ルが生じ始める炭素鋼のような金属材料では、更に生じやすいことになる。
【０００８】
【発明が解決しようとする課題】
本発明は、金属材料の表面にホウ酸系の酸化防止剤を塗布して行う熱間処理を塗布剤の酸化防止機能が、金属光沢を保持するレベルで発現されるようにする手段の提供を課題として研究を進めた結果、上記事情が生じうるとの推定の下に、塗布した酸化防止剤を短時間の内に溶融状態に到達させるべきことを知得してなされたものである。
【０００９】
【課題を解決するための手段】
上記課題は、金属材料の表面にホウ酸系の酸化防止剤を塗布して行う、金属材料の熱間処理方法において、酸化防止剤として融点が200℃〜600℃のものを用いるとともに、少なくとも上記融点迄の昇温速度を10〜100℃/sとする加熱により所定の熱間処理温度に到達させて熱間処理を施すことを特徴とする本発明熱間処理方法によって解決される。
【００１０】
即ち、10℃/s以上の昇温速度により、系の温度は１min未満の短時間で600℃以上に達し、この間、酸化防止剤の融点を上昇させる前記脱水反応が生起するいとまがないことから、酸化防止剤が本来の融点である600℃以下の温度で溶融して、該融点以上の温度で酸化防止機能を発現する。しかして、汎用金属材料の金属光沢が損われるような酸化が始まる温度が、前記自溶性合金材料等も含めて600℃以下に分布するため、融点が600℃以下の酸化防止剤を用いることが要件となるものである。なお、上記融点を超える温度域での昇温速度については、限定を要しないが、同様の急速加熱を続けて所定の熱間処理温度に到達させるのが、作業が複雑化せず、又、作業時間も短かくて済むことから得策である。
【００１１】
酸化防止剤の融点は、低い方が酸化防止機能が発現する温度も低くなるが、融点を低くするにはホウ酸類の水和率を大とする必要があり、これは熱的に不経済な要因となる。しかして、通常用いられる金属材料について云えば、200℃未満では実質的にスケ−ルが生成しないので上記下限を設けたものである。
【００１２】
又、昇温速度は大なるほど酸化防止剤の溶融がより早期に起ることになるが、設備費が嵩んだ分だけの効果には通じないので、100℃/s以下の昇温速度に留めるのが得策となるものである。
【００１３】
【発明の実施の形態】
上述のような急速加熱を行うための好適手段は、対象物を取り囲むなどの形で配した誘導コイルに交流を通電して行う誘導加熱法である。就中、コイルを移動させながら一部分ずつ順次加熱して行く移動加熱方式が、加熱の均一性に優れ、又、設備コストも小さくて済むので特に推奨される。但し、急速加熱の手段が限定されるものではなく、たとえば、直接通電加熱、あるいはレ−ザ−や赤外線による照射も状況に応じて有利な手段となる。
【００１４】
上記酸化防止剤の溶融相形成に与る基本成分として水和酸化ホウ素あるいはその塩類を用いてよいが、１価アルコ−ルのホウ酸エステルやその塩類のような、早々に熱分解して水和酸化ホウ素やその塩類を生成する物質を用いてもよい。上記ホウ酸エステル等を用いれば、アルコ−ルベ−スの高濃度の塗布液が容易に調製できる。水和酸化ホウ素としては、水和度が３モル水和物（オルトホウ酸）以下のものが前記融点範囲の実現に適しており、又、ホウ砂等のホウ酸塩の配合により融点やＰＨの調整を行うことができる。又、１価アルコ−ルのホウ酸エステルでは、酸化ホウ素と１価アルコ−ル（メタノ−ル等）の１：１〜１：２モル比反応生成物が、熱分解による水分の生成が少なく、適正融点範囲の溶融相を形成させるための基本成分として特に推奨される。ケイ酸やその塩類など、他系統の成分の配合も、上記基本成分の溶融特性を損わない範囲で許容される。
【００１５】
本発明方法に用いる酸化防止剤としては、上記溶融相形成成分のみを、たとえばアルコ−ルベ−スの塗布液の形で使用してもよいが、高温での酸化防止に必要と見なされる100g/m2以上の膜厚を上記成分のみによって実現するためには複数回の塗布が必要になるなどの問題が生じる。よって、１回での塗布量を増すための展着成分として、樹脂を１〜10％程度配合するとよい。但し、これらの配合によって熱間処理後の外観を損う残渣が生じないよう燃焼ないし熱分解して消失しやすいニトロセルロ−ズ，ポリビニルピロリドンのような樹脂を用いるのがよい。
【００１６】
更には、前記溶融相に顔料ないしは骨材が混和されていても酸化防止機能は損われないので、カオリン，シャモット，タルク等を増量剤として50％程度迄の範囲で配合してもよい。
【００１７】
［実施例］
鋼管（JIS STBA 22，外径42.7mm×肉厚6.0mm）の外周面にガス粉末溶射法によりＮｉ基自溶性合金材料（JIS SFNｉ 4）を溶射して、1.8mm厚さの溶射層を形成させた。
次いで、上記溶射層の表面に下記組成の酸化防止剤(A)を塗布し、乾燥させて約150g/m2の塗布層を形成させた後、溶射層を緻密化させ且つ母材との密着性を生じさせるための再溶融処理に供した。
【００１８】
＜酸化防止剤(A)の組成＞
▲１▼B2O3とメタノ−ルの１：1.5モル比の反応生成物 100部
▲２▼Na2B4O7-10H2O 25部
▲３▼H3BO3 3部
▲４▼ニトロセルロ−ス 3部
上記▲１▼〜▲４▼の成分を150mlのメタノ−ルで稀釈した。この酸化防止剤(A)の不揮発分からの脱水が進む前の融点は300℃である。
【００１９】
＜再溶融処理条件＞
・移動式誘導加熱（２mm/s）
・２kHz，20〜25kWの通電による
・再溶融処理温度：1060℃
・昇温速度：５℃/sを比較例１とし、10℃/s，30℃/s，100℃/sの各昇温速度を、本発明例１〜３とした。
この他に融点が700℃の市販のホウ酸系酸化防止剤(B)を塗布して、昇温速度を５℃/s，10℃/sで再溶融処理した比較例２，３も併せて評価に供した。
【００２０】
再溶融処理後の溶射層の性状は表１の通りであった。即ち、本発明方法によって再溶融処理を施したものにあっては、金属光沢が保持されるレベルで酸化防止が奏効しており、又、副次的な問題も発生しないことが確認された。
【００２１】
【表１】
【発明の効果】
本発明熱間処理方法は、上述の通り、ホウ酸系の酸化防止剤を塗布して行う熱間処理を、酸化防止剤として融点が200〜600℃のものを用いるとともに、少なくとも上記融点迄の昇温速度を10〜100℃/sとする加熱によって所定の熱間処理温度に到達させて熱間処理を施す構成により、酸化防止剤が溶融する前の温度域でスケ−ルが生成するという従来の問題点を解消した。
【００２３】
即ち、Ｎｉ基等の合金溶射層の再溶融処理のような高度の表面品質要請を伴う熱間処理においても、雰囲気炉等の高価な設備を用いた非能率な作業によらずに、金属光沢を保持したレベルの製品が得られるという品質と生産性を共に改善する効果がもたらされたものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of performing various hot treatments performed by heating a steel material or an alloy material to a temperature accompanied with scale generation while minimizing deterioration of surface quality due to oxidation.
[0002]
[Prior art]
Typical examples of the hot treatment include heat treatment of steel and the like and remelting treatment of a sprayed layer such as a Ni-based self-fluxing alloy. Since the latter is the final step of thermal spraying, which is a means of surface modification, the quality of the thermal sprayed layer, such as scale, grain boundary oxidation, cracks, surface layer alteration, surface hardness, etc. The effect is great. Accordingly, the following description will be made by taking the remelting treatment of the sprayed layer as an example, but the method of the present invention is not limited to the above treatment.
[0003]
A typical sprayed layer to be remelted is a Ni-based or Co-based alloy material blended with Cr, Mo or the like, and normally B and B which are flux forming components for the remelting process A self-fluxing alloy material to which Si is added is used.
[0004]
The remelting temperatures of these alloys are mostly in the range of 1000 to 1100 ° C., and the oxidation of Cr and the like proceeds violently by this heating. In the self-fluxing alloy, the oxidation is greatly reduced by the formation of flux, but it does not satisfy the high demand for maintaining the metallic luster. Therefore, the use of an atmospheric furnace or the setting of a margin on the premise of polishing and refinement is required for such high demands.
[0005]
On the other hand, methods for applying an antioxidant to reduce oxidation during hot treatment are known, and various types of antioxidants such as boric acid and water glass are proposed. The inventors of the present application also tried re-melting the self-fluxing alloy material by applying borax, which is a boric acid-based antioxidant with little problem of removal after the treatment, but it was not remarkably improved. Thus, the applied antioxidant had a trace of melting, but a green scale was thinly formed below it.
[0006]
The cause of this was considered as follows. That is, boric acid-based antioxidant contains hydrated boron oxide (boric acid) or a salt thereof as a basic component, which melts to form a glassy film, blocking oxygen and the like to have an antioxidant function. Although expressed, it has the property that the melting point rises due to a dehydration reaction during heating. For example, the melting point of metaboric acid, which is hydrated boron oxide in which boron oxide and water are combined at a molar ratio of 1: 1, is slightly higher than 200 ° C, but the melting point of boron oxide dehydrated to an anhydrous state is slightly higher than 450 ° C. . Moreover, although the melting point of borax, which is a 10 mol hydrate of sodium tetraborate, is 75 ° C, it dehydrates to anhydride at a temperature of 350 ° C or higher and settles to a melting point of around 800 ° C.
[0007]
That is, when a metal material coated with a boric acid-based antioxidant is heated, if the temperature is raised slowly, the coating agent is melted before the temperature of the system reaches the melting point of the coating agent and the coating agent melts. As the dehydration reaction proceeds, the melting point increases, and during this time, the coating agent cannot melt. Then, after that, it is dehydrated to anhydride, the melting point settles down to a constant value, and the melting starts only when the system reaches this temperature, and a film can be formed. That is, if the rate of temperature increase is low, a temperature range in which the antioxidant function is not exhibited may occur. However, the self-fluxing alloy material in which a considerable amount of Cr is blended does not lead to a remarkable improvement as described above because oxidation starts to increase from around 600 ° C. and scale starts to form. . Such a situation is more likely to occur in a metal material such as carbon steel where scaling starts to occur at the 200 ° C. range.
[0008]
[Problems to be solved by the invention]
The present invention provides a means for performing the hot treatment performed by applying a boric acid-based antioxidant on the surface of a metal material so that the antioxidant function of the coating agent is expressed at a level that maintains the metallic luster. As a result of conducting research as a subject, the present inventors have learned that the applied antioxidant should reach a molten state within a short time under the assumption that the above situation may occur.
[0009]
[Means for Solving the Problems]
In the hot treatment method for a metal material, which is carried out by applying a boric acid-based antioxidant to the surface of the metal material, the above-mentioned problem uses at least the above-mentioned antioxidant having a melting point of 200 ° C. to 600 ° C. The present invention is solved by the hot processing method of the present invention, wherein the hot processing is performed by reaching a predetermined hot processing temperature by heating at a heating rate of 10 to 100 ° C./s up to the melting point.
[0010]
That is, the temperature of the system reaches 600 ° C. or higher in a short time of less than 1 min due to the temperature rising rate of 10 ° C./s or more, and during this time, the dehydration reaction that raises the melting point of the antioxidant has to occur. Therefore, the antioxidant melts at a temperature of 600 ° C. or lower, which is the original melting point, and exhibits an antioxidant function at a temperature higher than the melting point. Therefore, since the temperature at which the oxidation starts to impair the metallic luster of the general-purpose metal material is distributed to 600 ° C. or less including the self-fluxing alloy material, etc., an antioxidant having a melting point of 600 ° C. or less should be used. It is a requirement. Note that the rate of temperature rise in the temperature range exceeding the melting point is not limited, but it is not complicated to continue the same rapid heating to reach a predetermined hot processing temperature, This is a good idea because it requires less work time.
[0011]
The lower the melting point of the antioxidant, the lower the temperature at which the antioxidant function is exhibited. However, to lower the melting point, it is necessary to increase the hydration rate of boric acids, which is thermally uneconomical. It becomes a factor. Thus, with regard to the metal material that is usually used, the scale is not formed substantially below 200 ° C., so the above lower limit is provided.
[0012]
In addition, the higher the rate of temperature rise, the faster the antioxidant will melt, but the effect of the increase in equipment costs will not lead to the effect, so the rate of temperature rise is 100 ° C / s or less. It is a good idea to keep it.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
A suitable means for performing the rapid heating as described above is an induction heating method in which an alternating current is passed through an induction coil arranged to surround an object. In particular, a moving heating method in which the coil is heated one by one while moving the coil is particularly recommended because of excellent uniformity of heating and low equipment cost. However, the rapid heating means is not limited. For example, direct current heating or irradiation with a laser or infrared rays is an advantageous means depending on the situation.
[0014]
Hydrated boron oxide or a salt thereof may be used as a basic component for forming the melt phase of the antioxidant. However, water such as monovalent alcohol borate ester or a salt thereof is rapidly decomposed to water. You may use the substance which produces | generates a sum boron oxide and its salt. By using the borate ester or the like, a high concentration coating solution of alcohol base can be easily prepared. As the hydrated boron oxide, those having a hydration degree of 3 mol hydrate (orthoboric acid) or less are suitable for realizing the melting point range, and the melting point and pH of the boric oxide can be adjusted by blending borate such as borax. Adjustments can be made. Moreover, in the monovalent alcohol borate ester, a 1: 1 to 1: 2 molar ratio reaction product of boron oxide and a monovalent alcohol (such as methanol) generates less water due to thermal decomposition. It is particularly recommended as a basic component for forming a melt phase in the proper melting point range. Blending of other system components such as silicic acid and salts thereof is allowed within a range not impairing the melting characteristics of the basic component.
[0015]
As the antioxidant used in the method of the present invention, only the above-mentioned melt phase forming component may be used, for example, in the form of an alcohol-based coating solution, but is considered to be necessary for antioxidant at a high temperature. In order to realize a film thickness of m 2 or more with only the above components, there arises a problem that a plurality of coatings are required. Therefore, it is good to mix | blend resin about 1 to 10% as a spreading | diffusion component for increasing the coating amount at once. However, it is preferable to use a resin such as nitrocellulose or polyvinyl pyrrolidone, which is easily lost by combustion or thermal decomposition so that a residue that impairs the appearance after the hot treatment is not generated by these blends.
[0016]
Furthermore, since the antioxidant function is not impaired even if a pigment or aggregate is mixed in the molten phase, kaolin, chamotte, talc or the like may be added in an amount of up to about 50% using a bulking agent.
[0017]
[Example]
Thermal spray layer of Ni-based self-fluxing alloy material (JIS SFNi 4) is sprayed on the outer peripheral surface of steel pipe (JIS STBA 22, outer diameter 42.7mm x wall thickness 6.0mm) by gas powder spraying method to form a 1.8mm thick sprayed layer I let you.
Next, after applying an antioxidant (A) having the following composition on the surface of the sprayed layer and drying to form a coating layer of about 150 g / m 2 , the sprayed layer was densified and adhered to the base material. The sample was subjected to a remelting treatment for producing the property.
[0018]
<Composition of antioxidant (A)>
(1) 1: 1.5 molar ratio of reaction product of B 2 O 3 and methanol 100 parts (2) Na 2 B 4 O 7 -10H 2 O 25 parts (3) H 3 BO 3 3 parts (4) Nitrocellulose 3 parts The above components (1) to (4) were diluted with 150 ml of methanol. The melting point of the antioxidant (A) before dehydration from the nonvolatile content is 300 ° C.
[0019]
<Remelting treatment conditions>
・ Mobile induction heating (2mm / s)
・ By energizing 2kHz, 20-25kW ・ Remelting temperature: 1060 ℃
-Temperature rising rate: 5 degreeC / s was made into the comparative example 1, and each temperature rising rate of 10 degreeC / s, 30 degreeC / s, and 100 degreeC / s was made into Examples 1-3 of this invention.
In addition, Comparative Examples 2 and 3 in which a commercially available boric acid antioxidant (B) having a melting point of 700 ° C. was applied and remelted at a rate of temperature increase of 5 ° C./s or 10 ° C./s were also combined. It used for evaluation.
[0020]
Table 1 shows the properties of the sprayed layer after the remelting treatment. That is, it was confirmed that in the case where the remelting process was performed by the method of the present invention, the oxidation was effective at a level where the metallic luster was maintained, and no secondary problem occurred.
[0021]
[Table 1]
【The invention's effect】
The hot treatment method of the present invention, as described above, performs the hot treatment performed by applying a boric acid-based antioxidant, using an antioxidant having a melting point of 200 to 600 ° C., and at least up to the above melting point. The scale is generated in the temperature range before the antioxidant is melted by the structure in which the heat treatment is performed by reaching a predetermined hot treatment temperature by heating at a heating rate of 10 to 100 ° C./s. The conventional problem was solved.
[0023]
In other words, even in hot processing with high surface quality requirements such as remelting processing of Ni-based alloy sprayed layers, metallic luster can be used regardless of inefficient work using an expensive facility such as an atmospheric furnace. This has the effect of improving both the quality and productivity of obtaining a product with a level that maintains
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29316396A JP3894601B2 (en) | 1996-10-16 | 1996-10-16 | Hot processing method for metal materials |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP29316396A JP3894601B2 (en) | 1996-10-16 | 1996-10-16 | Hot processing method for metal materials |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10121126A JPH10121126A (en) | 1998-05-12 |
| JP3894601B2 true JP3894601B2 (en) | 2007-03-22 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP29316396A Expired - Fee Related JP3894601B2 (en) | 1996-10-16 | 1996-10-16 | Hot processing method for metal materials |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3894601B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3204637B2 (en) | 1998-01-29 | 2001-09-04 | トーカロ株式会社 | Manufacturing method of self-fluxing alloy spray-coated member |
| JP4862125B2 (en) * | 2005-12-06 | 2012-01-25 | 国立大学法人九州工業大学 | Method for reforming material with thermal spray coating |
| JP5482533B2 (en) * | 2010-07-16 | 2014-05-07 | 新日鐵住金株式会社 | Antioxidant, method for producing antioxidant, and method for producing metal material |
-
1996
- 1996-10-16 JP JP29316396A patent/JP3894601B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH10121126A (en) | 1998-05-12 |
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