JP2010145164A - Quality control method of steel product - Google Patents
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- JP2010145164A JP2010145164A JP2008320871A JP2008320871A JP2010145164A JP 2010145164 A JP2010145164 A JP 2010145164A JP 2008320871 A JP2008320871 A JP 2008320871A JP 2008320871 A JP2008320871 A JP 2008320871A JP 2010145164 A JP2010145164 A JP 2010145164A
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- 239000010959 steel Substances 0.000 title claims abstract description 140
- 238000003908 quality control method Methods 0.000 title claims abstract description 39
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- 238000004458 analytical method Methods 0.000 claims abstract description 40
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 28
- 239000008151 electrolyte solution Substances 0.000 claims description 13
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 238000007689 inspection Methods 0.000 claims description 6
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- 239000000047 product Substances 0.000 abstract description 17
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- 238000005260 corrosion Methods 0.000 description 15
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 14
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 8
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/30—Computing systems specially adapted for manufacturing
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- Investigating And Analyzing Materials By Characteristic Methods (AREA)
- General Factory Administration (AREA)
- Heat Treatment Of Steel (AREA)
- Management, Administration, Business Operations System, And Electronic Commerce (AREA)
Abstract
Description
本発明は、自動車、造船、土木および建築などに用いられる鋼材を出荷するにあたり、顧客が必要な性能を有する最終製品を完成させるために適切な対策を実施することが可能となる品質管理情報を、顧客に提供する鋼材の品質管理方法に関するものである。 The present invention provides quality control information that enables customers to implement appropriate measures to complete a final product having the required performance when shipping steel materials used in automobiles, shipbuilding, civil engineering, and construction. The present invention relates to a quality control method for steel materials to be provided to customers.
自動車、造船、土木および建築などの材料として用いられる、薄鋼板、厚鋼板、棒鋼・線材等の鉄鋼一次製品（以降、鋼材と称することもする）を顧客に出荷するにあたっては、製品の一部もしくは全量について出荷検査を実施し、顧客の要望を満足する製品特性を保証するために、ミルシートに、製品素材の化学組成、機械特性等の必要事項を記載することが一般的に行なわれている。そして、顧客は前記ミルシートに記載された情報を基に、熱処理や加工等の次工程の処理条件を決定し、二次製品あるいは最終製品を完成させる。従って、出荷検査結果の情報を記載したミルシートは、供給側、顧客の双方にとって重要な性能保証の一種となる。
製品素材の化学組成は材料特性を大きく支配する重要情報であるが、化学組成のみでは材料特性は一義的に決まらない。そのため、材料強度や、伸び特性といった一般的な機械特性の情報も必要である。
しかしながら、供給側からは、顧客が出荷した製品に対しどのような二次処理をかけるか、また、どのような用途のどの部分に用いるか等を完全に把握することは難しい。そして、二次処理の方法や鋼材の使用部位によっては、化学組成や機械特性だけから把握する情報では鋼材が必要な性能を発揮できない可能性もある。
以上を鑑みると、現状では、例えば、顧客が鋼材を加工した時に発生する割れ等の問題に対して適切な対策を実施するための、出荷時の鋼材の情報は十分とはいえない。
When shipping primary steel products (hereinafter also referred to as steel materials) such as thin steel plates, thick steel plates, steel bars and wire rods used as materials for automobiles, shipbuilding, civil engineering, and construction, a part of the products Or, in order to guarantee the product characteristics that satisfy the customer's requirements by conducting a shipping inspection on the whole quantity, it is common practice to describe necessary items such as chemical composition and mechanical properties of the product material on the mill sheet. . And a customer determines the processing conditions of the next process, such as heat processing and a process, based on the information described in the said mill sheet, and completes a secondary product or a final product. Therefore, the mill sheet describing the information on the shipping inspection result is a kind of performance guarantee important for both the supply side and the customer.
The chemical composition of the product material is important information that largely controls the material properties, but the material properties are not uniquely determined only by the chemical composition. Therefore, information on general mechanical properties such as material strength and elongation properties is also necessary.
However, it is difficult for the supply side to completely understand what secondary processing is applied to the product shipped by the customer and what part of which application is used. And depending on the method of the secondary treatment and the site where the steel is used, there is a possibility that the steel cannot perform the required performance with information obtained from only the chemical composition and mechanical properties.
In view of the above, under the present circumstances, for example, information on steel materials at the time of shipping is not sufficient for implementing appropriate measures against problems such as cracks that occur when a customer processes steel materials.
本発明は、かかる事情に鑑みなされたもので、顧客が必要な性能を有する最終製品を完成させるために適切な対策を実施することが可能となる品質管理情報を、顧客に提供する鋼材の品質管理方法を提供することを目的とするものである。 The present invention has been made in view of such circumstances, and the quality of the steel material that provides the customer with quality control information that enables the customer to take appropriate measures to complete the final product having the required performance. The purpose is to provide a management method.
上記課題を解決するため、発明者らは、顧客側にとって有益な情報とはどんなものであるかについて検討した。
現状、簡易に提供できる情報は鋼材素材の化学組成情報や機械的特性である。しかし、鋼材中に含まれるA元素が鋼中にどのような形態で分布しているかは、化学組成情報のみでは分からないことが多い。例えば、製造工程における凝固偏析などの問題により、鋼材中に特定元素の極端な元素分布などが生じている場合、これらの鋼材は、顧客側での過酷な加工工程などで割れ等を生じる可能性が高い。さらには、鋼材の疲労特性や、耐水素割れ等に甚大なる影響を及ぼしかねない粗大な析出物および／または介材物の有無は、安全部材を製造する場合には非常に重要な情報となる。
In order to solve the above problems, the inventors have examined what information is useful for the customer side.
At present, information that can be provided simply is chemical composition information and mechanical properties of steel materials. However, it is often not known from the chemical composition information alone how the A element contained in the steel material is distributed in the steel. For example, if there is an extreme element distribution of a specific element in the steel due to problems such as solidification segregation in the manufacturing process, these steels may crack in severe processing steps on the customer side. Is expensive. Furthermore, the presence or absence of coarse precipitates and / or intervening materials that can have a profound effect on the fatigue properties of steel materials, hydrogen cracking resistance, etc. is very important information when manufacturing safety members. .
すなわち、鋼材を顧客に出荷する際に、顧客側に鋼材中の着目元素の固溶量（固溶状態での含有率）や析出物および／または介在物のサイズ別の情報（析出状態での含有率やサイズ情報等）等の詳細情報を提供することによって、必要な性能を得るための適切な対策を顧客がとることが可能となる。
しかしながら、従来の分析技術では、上記分析情報を迅速かつ高精度に、鉄鋼材料一次製品の品質管理情報として十分な程度の分析情報を容易に得ることはできなかった。
そこで、発明者らは、既に開発した迅速かつ高精度に把握することが可能な新しい分析法を、本発明の上記分析情報を得る分析法として用いることとした。そして、この分析法により得られた情報を品質管理情報として顧客に提供することによって、鋼材に重大な欠陥がなくなり、顧客が安心して使用することを保証することになる。本発明は、上記思想に基づき、完成するに至ったものである。
That is, when shipping steel products to customers, the amount of solid solution (content in solid solution) of the element of interest in the steel materials and information on the size of precipitates and / or inclusions (precipitation state) By providing detailed information such as content rate and size information, the customer can take appropriate measures to obtain the required performance.
However, with the conventional analysis technique, it has not been possible to easily obtain sufficient analysis information as the quality control information of the steel material primary product quickly and with high accuracy.
Therefore, the inventors decided to use the new analysis method that has been developed and can be grasped quickly and with high accuracy as the analysis method for obtaining the analysis information of the present invention. By providing the information obtained by this analysis method to the customer as quality control information, the steel material is free from serious defects and it is guaranteed that the customer can use it with peace of mind. The present invention has been completed based on the above idea.
本発明は、以上の知見に基づきなされたもので、その要旨は以下のとおりである。
［１］鋼材における、析出物および／または介在物の組成の情報、析出物および／または介在物のサイズの情報、着目する元素の固溶量の情報の一つ以上を得る分析ステップと、前記分析ステップにて得られた前記各情報に基づく分析結果のうちの少なくとも1つを、前記鋼材の品質管理情報として、前記鋼材を出荷する際に、または、前記鋼材の出荷と別途に、顧客へ提供する情報提供ステップとを有することを特徴とする鋼材の品質管理方法。
［２］前記［１］において、前記分析ステップは、鋼材を電解液中で電解し、前記鋼材に付着している析出物および／または介在物を分散性を有する溶液中に分離後、析出物および／または介在物の組成の情報、析出物および／または介在物のサイズの情報、着目する元素の固溶量の情報の一つ以上を得る分析をすることを特徴とする鋼材の品質管理方法。
［３］前記［２］において、前記分析ステップは、分離された析出物および／または介在物を含んだ分散性を有する溶液を一段以上ろ過することにより、前記析出物および／または介在物をサイズ別に分別することを特徴とする鋼材の品質管理方法。
［４］前記［３］において、前記分析ステップは、鋼材の素材中央部よりサンプリングした物を分析し、サイズが1μm以上の析出物および／または介在物の情報を得ることを特徴とするの鋼材の品質管理方法。
［５］前記［１］〜［４］のいずれかにおいて、前記分析ステップは、鋼材を電解した後の電解液を分析し、前記電解液中の着目元素の濃度と鉄の濃度との比を求め、求められた比に前記鋼材の鉄の全濃度を乗じることで、着目元素の固溶量を分析することを特徴とする鋼材の品質管理方法。
［６］前記［１］〜［５］のいずれかにおいて、前記情報提供ステップにおいて、前記品質管理情報は、顧客側での鋼材の使用用途の細分化を可能とするものであり、かつ、検査証明書に記載され提供されることを特徴とする鋼材の品質管理方法。
なお、本発明において、析出物及び／又は介在物を、まとめて析出物等と称することとする。
The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] An analysis step for obtaining one or more of information on the composition of precipitates and / or inclusions in the steel material, information on the size of the precipitates and / or inclusions, and information on the solid solution amount of the element of interest; At least one of the analysis results based on each information obtained in the analysis step is used as quality control information of the steel material, when shipping the steel material, or separately from the shipment of the steel material, to the customer A quality control method for steel material, comprising: an information providing step to provide.
[2] In the above [1], in the analysis step, the steel material is electrolyzed in an electrolytic solution, and precipitates and / or inclusions adhering to the steel material are separated into a solution having dispersibility, and then the precipitates are separated. And / or analysis of obtaining one or more of information on the composition of inclusions, information on the size of precipitates and / or inclusions, and information on the solid solution amount of the element of interest .
[3] In the above [2], in the analysis step, the precipitate and / or the inclusion is sized by filtering one or more stages of the dispersed solution containing the separated precipitate and / or the inclusion. A quality control method for steel materials, characterized by separate separation.
[4] The steel material according to [3], wherein the analysis step analyzes a material sampled from a central portion of the raw material of the steel material to obtain information on precipitates and / or inclusions having a size of 1 μm or more. Quality control method.
[5] In any one of [1] to [4], the analyzing step analyzes an electrolytic solution after electrolyzing the steel material, and calculates a ratio between the concentration of the element of interest and the concentration of iron in the electrolytic solution. A quality control method for a steel material, characterized in that the solid solution amount of the element of interest is analyzed by multiplying the obtained ratio and the total iron concentration of the steel material.
[6] In any one of the above [1] to [5], in the information providing step, the quality control information enables subdivision of usage of the steel material on the customer side, and inspection. A method for quality control of steel, which is described and provided in a certificate.
In the present invention, precipitates and / or inclusions are collectively referred to as precipitates.
本発明によれば、顧客が必要な性能を有する最終製品を完成させるために適切な対策を実施することが可能となる品質管理情報を、顧客に提供することができる。
そして、顧客における二次処理や使用用途などを考慮し、顧客側が使用の際に必要な性能が発揮できるよう情報提供することで、顧客との出荷製品の取り扱いにおいて、顧客からの信用と安心を獲得することができる。
ADVANTAGE OF THE INVENTION According to this invention, the quality control information which becomes possible to implement an appropriate measure in order to complete the final product which a customer has required performance can be provided to a customer.
In consideration of secondary processing and usage in the customer, and providing information so that the customer can demonstrate the required performance when using it, the trust and security from the customer in handling the products shipped with the customer. Can be earned.
以下、本発明について、詳細に説明する。
供給側および顧客側双方にとって、鋼組成は製品を保証する上での基本的情報である。しかしながら、前述したように鋼組成として含有されるA元素が鋼中に固溶状態で存在するのか、析出した状態で存在するのかは、化学組成情報のみでは分からない。例えば、これまでもAlなどに関しては、鋼中に含有される酸化物を含む全Al量としてTotal Alと、酸可溶性のAl量としてSoluble Alの併記を行う場合があった。こうした要求に対応するために、工程分析の分野においては、Soluble Al値を求めることが一般的に行なわれている。
本発明は、この考え方をさらに拡張したものであり、特に顧客において行われる後処理で鋼中での存在形態（固溶しているか析出しているか）が変化しうる着目すべき元素（以下、着目元素と称す）について、その存在形態の明確な情報を得、この情報を顧客に提供する。
さらに、本発明では、本発明者らが開発した着目元素の鋼中での固溶状態と析出状態の定量値および析出物等のサイズ別における析出物等中の定量値を迅速かつ正確に把握することが可能な新しい分析法を、検査に必要な情報を得るための分析法として用いることとする。
以上は本発明の特徴であり、重要な要件である。以下にその詳細について説明する。
図１は、本発明に係る品質管理工程の一実施態様を示す図である。
図１は顧客側で実施される5工程（破線）と製造側で実施される3工程（実線）から構成される。まず、顧客において、Step 1〜2で過去の知見に基づきながら用途に応じた仕様を決定し、Step 3で鋼材種と析出・固溶の好適範囲を指定した発注を行なう。この発注内容に基づき、製造側では、Step 4で顧客の析出・固溶要求をできるだけ満たせるよう鋼材を製造し、Step 5で着目元素の固溶量、析出物等の組成の情報、析出物等のサイズの情報のうち少なくとも1つについて分析する。なお、この分析ステップでは、後述する、迅速かつ高精度に情報を得ることが可能な新しい分析法を適用する。もし、この段階で、顧客の発注した好適範囲と分析結果が一致しない場合は、当該製造物を条件を満たす他の注文に割り振るか、もしくは製造条件等を再設定して顧客発注好適範囲を満足する鋼材を再製造する。次いで、顧客の発注した好適範囲と分析結果が一致して製造された鋼材を、Step 6で、分析した析出・固溶情報を添付し出荷する。特に、この時点で鋼材の疲労特性や、耐水素割れ等に甚大なる影響を及ぼしかねない１μｍ以上の粗大な介在物・析出物の有無を鋼材データとして提供する。次に、顧客が入荷した鋼材は、Step 7で前記析出・固溶情報を基に鋼材の用途を決定する。そして、場合によっては、ステップ３（析出状態・固溶の好適範囲）、ステップ７（析出・固溶情報にもとづく素材の用途決定）にフィードバックし、データベースを更新する。
Hereinafter, the present invention will be described in detail.
For both the supply side and the customer side, the steel composition is the basic information in guaranteeing the product. However, as described above, whether the element A contained as a steel composition exists in a solid solution state or a precipitated state in the steel is not known only by chemical composition information. For example, regarding Al and the like, there have been cases where Total Al is included as the total amount of Al including oxides contained in the steel and Soluble Al as the amount of acid-soluble Al. In order to meet these requirements, it is a common practice to obtain a Soluble Al value in the field of process analysis.
The present invention is a further extension of this concept. In particular, an element to be noted (hereinafter, referred to as “dissolved” or “precipitated”) in the steel can be changed in post-treatment performed by a customer. For the element of interest), clear information on its form is obtained and this information is provided to the customer.
Furthermore, in the present invention, the quantitative values of the solid solution state and the precipitation state of the element of interest developed by the present inventors in the steel and the quantitative values in the precipitates by size of the precipitates, etc. are quickly and accurately grasped. A new analysis method that can be used will be used as an analysis method for obtaining information necessary for inspection.
The above are features of the present invention and are important requirements. The details will be described below.
FIG. 1 is a diagram showing an embodiment of a quality control process according to the present invention.
FIG. 1 is composed of five steps (broken line) performed on the customer side and three steps (solid line) performed on the manufacturing side. First, the customer determines the specifications according to the application based on past knowledge in Steps 1 and 2, and in
次に、上記Step 5にて行われる、分析方法について説明する。
鋼材における、析出物等の組成の情報、析出物等のサイズの情報、着目する元素の固溶量の情報の一つ以上を得る分析ステップでは、本発明者らが開発した、高精度に、析出物等の組成、サイズおよび着目元素の固溶量を分析する方法を用いることとし、これについて以下に説明する。
Next, the analysis method performed in
In the analysis step of obtaining one or more of information on the composition of precipitates, information on the size of precipitates, etc., and information on the solid solution amount of the element of interest in the steel material, the inventors have developed with high accuracy, A method for analyzing the composition and size of the precipitates and the solid solution amount of the element of interest is used, and this will be described below.
鋼材試料を適切な条件で電解し、析出強化元素の固溶部分をマトリクスの鉄とともに電解液中に溶解させ、析出物等を試料表面に露出させる。このとき、露出した析出物等は電気的引力によって陽極である試料表面に付着するので、析出物等と電解液(固溶部分)とを分離できる。すなわち、析出物等の付着した試料を電解液から取り出すだけで、ほとんどすべての析出物等が電解液から取り出せることになる。そして、試料とともにポリ燐酸水溶液のような分散性を有する溶液に浸漬して超音波を付与し、試料に付着している析出物等を試料から剥離する。このとき、分離された析出物等は、ポリ燐酸塩から表面電荷が付与されて、互いに反発しあって分散性を有する溶液中に分散する。 The steel material sample is electrolyzed under appropriate conditions, and the solid solution portion of the precipitation strengthening element is dissolved in the electrolytic solution together with the iron of the matrix to expose the precipitate and the like on the sample surface. At this time, the exposed precipitates and the like adhere to the surface of the sample, which is the anode, by electric attraction, so that the precipitates and the electrolytic solution (solid solution portion) can be separated. That is, almost all the precipitates and the like can be taken out from the electrolytic solution only by taking out the sample to which the deposits and the like are attached from the electrolytic solution. Then, the sample is immersed in a dispersible solution such as an aqueous polyphosphoric acid solution to apply ultrasonic waves, and precipitates and the like attached to the sample are peeled off from the sample. At this time, the separated precipitates and the like are given surface charges from the polyphosphate, repel each other, and are dispersed in a solution having dispersibility.
先ず、析出物等をサイズ別に分けない場合には、析出物等を含んだ分散性を有する溶液を動的光散乱分光分析方法で分析し、全析出物等の平均粒径や粒径分布を求める。 First, when the precipitates are not classified by size, a solution having dispersibility containing the precipitates is analyzed by a dynamic light scattering spectroscopic analysis method, and the average particle size and particle size distribution of all the precipitates are determined. Ask.
次に、析出物等をサイズ別に分ける場合には、以下の手順による。析出物等の分散した分散性を有する溶液をフィルタ孔径YとZ(ただし、Y>Z)のフィルタを用いて順次ろ過する。このとき、孔径Yのフィルタ上の残渣がサイズY以上の析出物等であり、孔径Zのフィルタ上の残渣がサイズZ以上Y未満の析出物等であり、孔径Zのフィルタを透過したろ液にはサイズZ未満の析出物等が含まれる。次いで、ろ過後のフィルタ上の析出物等とろ液を、誘導結合プラズマ(ICP)発光分光分析法、ICP質量分析法および原子吸光分析法等により分析し、サイズY以上、サイズZ以上Y未満、サイズZ未満の析出物等中の着目元素の含有量を求める。または、ろ過後のろ液を動的光散乱分光分析方法で分析し、サイズZ未満の析出物等の平均粒径や粒径分布を求める。 Next, when the precipitates are separated by size, the following procedure is used. A solution having dispersibility in which precipitates are dispersed is sequentially filtered using a filter having filter pore sizes Y and Z (where Y> Z). At this time, the residue on the filter with a pore size Y is a precipitate of size Y or larger, the residue on the filter with a pore size Z is a precipitate of size Z or larger and less than Y, and the filtrate that has passed through the filter with a pore size Z Includes precipitates having a size less than Z. Next, the precipitate and the filtrate on the filter after filtration are analyzed by inductively coupled plasma (ICP) emission spectroscopy, ICP mass spectrometry, atomic absorption spectrometry, etc., size Y or more, size Z or more and less than Y, The content of the element of interest in precipitates and the like having a size less than Z is determined. Alternatively, the filtrate after filtration is analyzed by a dynamic light scattering spectroscopic analysis method, and the average particle size and particle size distribution of precipitates having a size less than Z are obtained.
このように、複数のフィルタ孔径のフィルタを用いてろ過することにより、析出物等をサイズ別に分別することが可能となる。なお、析出物等を含んだ分散性を有する溶液を所定のフィルタ孔径のフィルタでろ過すると、析出物等のサイズに応じてフィルタに捕集されるものとフィルタを通過するものとに分かれるが、このとき、比較的大きな析出物等によりフィルタ孔の閉塞が進行し、本来通過するべきサイズの析出物等がフィルタを通過せずに捕集されることがある。このような場合は、フィルタに捕集された析出物等の分析値は正しい値より高くなり、反対にろ液の分析値は正しい値より低くなる。しかし、フィルタとして、直孔でかつ4%以上の空隙率を有するフィルタを用いれば、フィルタ孔径より小さい析出物等が捕集されることなく、より正確な析出物等のサイズ別分析が可能となる。ここで、直孔とは、一定の開口形状で貫通しているフィルタ孔のことをいう。 In this way, by using a filter having a plurality of filter pore diameters, the precipitates and the like can be separated according to size. In addition, when a solution having dispersibility containing precipitates and the like is filtered with a filter having a predetermined filter pore size, it is divided into those collected by the filter according to the size of the precipitates and those passing through the filter. At this time, the filter pores are blocked by relatively large precipitates and the like, and precipitates having a size that should pass through may be collected without passing through the filter. In such a case, the analytical value of the precipitate collected in the filter becomes higher than the correct value, and conversely, the analytical value of the filtrate becomes lower than the correct value. However, if a filter that is a straight hole and has a porosity of 4% or more is used as a filter, it is possible to analyze precipitates by size more accurately without collecting precipitates smaller than the filter pore diameter. Become. Here, the straight hole refers to a filter hole penetrating with a certain opening shape.
着目元素の固溶量を求めるには、析出物等と分離された電解液中の着目元素の絶対量を測定して、鋼材試料の電解重量で除算する必要がある。しかしながら、一般的な電解液はメタノールを主体とした有機溶媒で揮発性が高いうえに数百ミリリットルもの液量となることから、着目元素の含有量を測定することは容易ではない。そこで、多量の電解液から1/10以下の適当量を採取して乾燥した後、適切な溶液で溶解して水溶液としてから着目元素と鉄をそれぞれ適切な溶液分析法で測定し、その濃度比(即ち、着目元素の測定濃度／鉄の測定濃度)に鋼材試料中の鉄の含有量を乗算することにより、着目元素の鋼中の固溶量を求めた。なお、水溶液を分析する方法としては、ICP発光分光分析法、ICP質量分析法および原子吸光分析法が適当である。また、鋼材試料中の鉄の含有量を求めるための方法としては、スパーク放電発光分光分析方法(JIS G1253)、蛍光Ｘ線分析方法(JIS G1256)、ICP発光分光分析法およびICP質量分析法等により得られた鉄以外の元素の合計値を100mass%から減算する方法が適当である。 In order to obtain the solid solution amount of the element of interest, it is necessary to measure the absolute amount of the element of interest in the electrolytic solution separated from precipitates and divide by the electrolytic weight of the steel material sample. However, a general electrolytic solution is an organic solvent mainly composed of methanol, and has a high volatility and a liquid amount of several hundred milliliters. Therefore, it is not easy to measure the content of the element of interest. Therefore, after collecting an appropriate amount of 1/10 or less from a large amount of electrolyte and drying it, dissolve it in an appropriate solution to make an aqueous solution, and then measure the element of interest and iron by an appropriate solution analysis method. By multiplying (ie, the measured concentration of the element of interest / the measured concentration of iron) by the iron content in the steel material sample, the solid solution amount of the element of interest in steel was determined. As a method for analyzing the aqueous solution, ICP emission spectroscopy, ICP mass spectrometry, and atomic absorption spectrometry are suitable. In addition, methods for determining the iron content in steel samples include spark discharge emission spectrometry (JIS G1253), X-ray fluorescence analysis (JIS G1256), ICP emission spectroscopy, ICP mass spectrometry, etc. A method of subtracting the total value of elements other than iron obtained by the method from 100 mass% is appropriate.
本発明の鋼材の品質管理方法においては、こうして得られた析出物等の組成、サイズおよび着目元素の固溶量のうち少なくとも一つの情報（分析結果）を、品質管理情報として顧客に提供する。
析出物等の組成の結果のみを用いる場合は、例えば、析出物を構成する着目元素の種類とその含有量製品の組成値全体を100mass%とした場合のmass％など、必要に応じた方法で提示可能である。また、析出物等のサイズの結果のみを用いる場合は、例えば、前述の動的光散乱分光分析方法で得られた平均粒径や粒径分布を提示できる。析出物等の組成とサイズの両方の結果を用いる場合は、例えば、析出物等のサイズ別における着目元素の析出物等中の含有量が提示できる。なお、着目元素の析出物等中の含有量とは、例えば、着目する元素に関して、その元素が析出物等としてどれくらい存在しているかを、(a)鋼材（製品）全体に対する含有率、(b)着目元素量全体に対する比、(c)着目元素の固溶量に対する比、等、必要に応じて提示できる。また他の例として、着目元素の析出量と析出物等の平均粒径や粒径分布を同時に提示することも可能である。
また、着目元素の固溶量は、例えば、着目する元素に関して、その元素が固溶した状態でどれくらい存在しているかを、(d)鋼材全体に対する含有率、(e)着目元素量全体に対する比、(f)析出物等中の着目元素の含有量に対する比、等、必要に応じて提示できる。
In the steel material quality control method of the present invention, at least one piece of information (analysis result) among the composition, size, and solid solution amount of the element of interest obtained in this way is provided to the customer as quality control information.
When using only the result of the composition of the precipitate, for example, the mass of the element of interest constituting the deposit and the mass content when the total composition value of the product is 100 mass%, etc. Can be presented. Further, when only the result of the size of the precipitate or the like is used, for example, the average particle size and the particle size distribution obtained by the above-described dynamic light scattering spectroscopic analysis method can be presented. When using the results of both the composition and the size of the precipitates, for example, the content in the precipitate of the element of interest by size of the precipitates can be presented. It should be noted that the content of precipitates of the element of interest is, for example, how much the element is present as precipitates, etc. with respect to the element of interest, The ratio to the total amount of the element of interest, (c) the ratio of the element of interest to the solid solution amount, etc. can be presented as necessary. As another example, the precipitation amount of the element of interest and the average particle size and particle size distribution of the precipitates can be presented simultaneously.
In addition, the solid solution amount of the element of interest is, for example, how much the element is present in the solid solution state in terms of (d) the content ratio with respect to the entire steel material, and (e) the ratio with respect to the total amount of element of interest. (F) The ratio to the content of the element of interest in the precipitate or the like can be presented as necessary.
提供する方法として、例えば、以下の方法があげられる。
（１）析出および／または固溶情報、すなわち析出物等の組成、析出物等のサイズ別の各析出量および着目する元素の固溶量の内少なくとも1つを、ミルシート（検査証明書）に記載する。
（２）鋼材出荷時に、出荷票（納品書等）に析出・固溶情報を記載したシート若しくは当該情報を記憶した電子媒体（磁気ディスク、ＣＤ、ＤＶＤなど）を添付する。
（３）出荷側（鋼材製造者、コイルセンタ、商社等）のＷｅｂサイト（インターネット）に、析出・固溶情報を掲載し、注文番号等を対応付けて顧客が当該情報をダウンロードできるようにする。
（４）電子メールやその他の電子的通信手段により析出・固溶情報を顧客に送付する。
Examples of the providing method include the following methods.
(1) Precipitation and / or solid solution information, that is, at least one of the composition of the precipitates, the amount of precipitation by size of the precipitates, and the amount of solid solution of the element of interest, in the mill sheet (inspection certificate) Describe.
(2) At the time of shipment of steel materials, a sheet on which precipitation / solid solution information is described or an electronic medium (magnetic disk, CD, DVD, etc.) storing the information is attached to a shipping slip (invoice, etc.).
(3) Precipitation / solid solution information is posted on the website (Internet) of the shipping side (steel material manufacturer, coil center, trading company, etc.), and the customer can download the information by associating the order number and the like. .
(4) Send precipitation / solid solution information to customers by e-mail or other electronic communication means.
例えば、優れた耐疲労強度を得る技術として、鋼組成および高周波焼き入れ条件の適正化によって焼き入れ層の旧オーステナイト粒径（表面組織）を微細化することは知られており、特性は添加されるMoの固溶・析出状態に依存することが定性的にわかっている。Moの添加または含有量が低い場合や、添加量または含有量は十分でも鋼材表面の有効固溶Moが確保できていない場合、表面の組織の微細化が不十分となり、目標の疲労強度が得られない場合がある。
これに対して、本発明の品質管理方法では、鋼材を出荷する際に、組成情報だけでなく、表層付近のMo固溶情報や析出情報を品質管理情報として提供する。本鋼材は、原則的に顧客側で部品形状に加工後、高周波熱処理されるため、出荷鋼材に関しては、組成情報だけでなく、表層付近のMo固溶情報や析出情報を添付することにより、顧客側で部品形状に加工後、高周波熱処理された後、疲労特性が確保されることになる。あるいは、情報によっては顧客側にて高周波熱処理条件の変更を行うことが可能になる。
For example, as a technique for obtaining excellent fatigue strength, it is known to refine the prior austenite grain size (surface structure) of the quenched layer by optimizing the steel composition and induction hardening conditions. It is qualitatively known to depend on the solid solution and precipitation state of Mo. If the addition or content of Mo is low, or if the addition or content is sufficient, but the effective solid solution of Mo on the steel surface cannot be secured, the surface microstructure will be insufficient and the target fatigue strength will be obtained. It may not be possible.
In contrast, the quality control method of the present invention provides not only the composition information but also Mo solid solution information and precipitation information in the vicinity of the surface layer as quality control information when shipping the steel material. In principle, this steel material is processed by the customer into a component shape and then subjected to high-frequency heat treatment. For shipped steel materials, not only the composition information but also Mo solid solution information and precipitation information in the vicinity of the surface layer are attached. After being processed into a part shape on the side and subjected to high-frequency heat treatment, fatigue characteristics are ensured. Alternatively, depending on the information, it becomes possible to change the high-frequency heat treatment conditions on the customer side.
例えば、粒界炭化物の有無が甚大な影響を及ぼしかねない高強度パイプ素材の情報提供例について示す。過酷な環境要因により発生する粒界応力腐食割れは、出荷された素材が施工現場で溶接された際、溶接熱影響部(以下HAZ部)におけるCr含有炭化物析出に伴って粒界近傍にCrの欠乏領域を形成することが一因と考えられている。従って、粒界応力腐食割れの抑制に対しては、HAZ部での粒界に沿ったCr含有炭化物析出を根本的に抑制する組成の調整や、形成したCrの欠乏領域を解消する後熱処理が必要である。しかし、後者は、施工現場での後熱処理を強いるものであり、コスト的に好まれない。ゆえに、粒界応力腐食割れの防止には、HAZ部での粒界に沿ったCr含有炭化物析出を根本的に抑制する組成に調整することが重要であり、素材提供の時点でHAZ部における炭化物形成の可能性が低い鋼組成であることを示すとともに、再現溶接熱サイクル試験によってCr系炭化物形成の情報を提供することが、顧客にとって極めて重要な意味を有することになる。 For example, an example of providing information on a high-strength pipe material in which the presence or absence of grain boundary carbides may have a profound effect will be described. Intergranular stress corrosion cracking, which occurs due to severe environmental factors, is caused by the presence of Cr in the vicinity of the grain boundary due to the precipitation of Cr-containing carbides in the weld heat affected zone (hereinafter referred to as HAZ) when the shipped material is welded at the construction site. The formation of a deficient region is considered to be a cause. Therefore, for the suppression of intergranular stress corrosion cracking, adjustment of the composition that fundamentally suppresses Cr-containing carbide precipitation along the grain boundary in the HAZ part and post-heat treatment to eliminate the Cr deficient region formed is necessary. However, the latter imposes post-heat treatment at the construction site and is not preferred in terms of cost. Therefore, in order to prevent intergranular stress corrosion cracking, it is important to adjust to a composition that fundamentally suppresses Cr-containing carbide precipitation along the grain boundaries at the HAZ part. Providing information on Cr-based carbide formation through reproducible welding thermal cycle testing will be extremely important to customers, indicating that the steel composition has a low formation potential.
例えば、ラインパイプ用高強度鋼の特性に甚大影響を及ぼす可能性の高い粗大な介在物・析出物に関する情報提供事例を示す。近年は、パイプライン環境におけるサワー性への対応が強く望まれている。その理由は、輸送流体中に高濃度のH2S等が含まれるためである。このため、素材設計上は耐HIC性（耐水素誘起割れ）および耐SSC性（耐硫化物腐食割れ）をいかに確保するかが重要である。耐SSCに関しては、極低S化とMnやCaによる適切な硫化物制御によって安定した回避が可能であるが、環境水素が関与する耐HIC性については、腐食、応力等の環境因子が複雑に関与しており、必ずしも要因を特定することは難しい。一般的にはマルテンサイト組織などの高強度鋼素材は、使用中に外部より原子状水素が浸入し、鋼組織中の転位等の構造欠陥に拡散性水素としてトラップされる。これらの拡散性水素は、例えば粗大な介在物や析出物と母相の界面に水素ガスとして集積し最終的に割れ発生起点となることが指摘されている。
このため、例えばH2Sガスなどの過酷なサワー環境下で使用されるラインパイプ素材は、安定な水素トラップサイトとなりやすい粗大な介在物の形成を出来るだけ軽減するように材料設計される。しかしながら、素材作製工程においてしばしば合金元素の中央偏析などにより、意図せずして粗大な介在物・析出物を内包することがある。
これに対して、本発明の鋼材の品質管理方法では、中央偏析が問題になる鋼材中央部よりサンプリングし、この鋼材中央部の析出物等の組成やサイズの情報を品質管理情報として顧客に提供する。これにより、顧客側でのパイプライン環境におけるサワー性が確保される。
For example, the information provision example about the coarse inclusion and the precipitate which has a high possibility of having a great influence on the characteristic of the high strength steel for line pipes is shown. In recent years, it has been strongly desired to cope with sourness in a pipeline environment. The reason is that the transport fluid contains a high concentration of H 2 S or the like. For this reason, how to ensure HIC resistance (hydrogen induced cracking resistance) and SSC resistance (sulfide corrosion cracking resistance) is important in material design. With regard to SSC resistance, stable avoidance is possible by extremely low S and appropriate sulfide control by Mn and Ca, but for HIC resistance involving environmental hydrogen, environmental factors such as corrosion and stress are complicated. Being involved, it is difficult to identify the factors. In general, high-strength steel materials such as martensite structure intrude atomic hydrogen from the outside during use, and are trapped as diffusible hydrogen in structural defects such as dislocations in the steel structure. It has been pointed out that these diffusible hydrogen accumulates as hydrogen gas at the interface between coarse inclusions and precipitates and the parent phase, and finally becomes a starting point of cracking.
For this reason, for example, a line pipe material used in a severe sour environment such as H 2 S gas is designed to reduce as much as possible the formation of coarse inclusions that are likely to become stable hydrogen trap sites. However, in the raw material production process, coarse inclusions and precipitates may be included unintentionally due to the central segregation of alloy elements.
On the other hand, in the quality control method for steel materials according to the present invention, sampling is performed from the central portion of the steel material where central segregation is a problem, and information on the composition and size of precipitates and the like in the central portion of the steel material is provided to customers as quality control information To do. Thereby, the sourness in the pipeline environment on the customer side is ensured.
実施例１は、顧客側にて部品形状に加工後、高周波熱処理される鋼材を出荷する場合であり、鋼材を出荷するに際し、組成情報だけでなく、表層付近のMo固溶情報や析出情報を品質管理情報として提供することにより、顧客側での高周波熱処理後の疲労特性を確保すること、あるいは高周波熱処理条件の変更等を可能にする例である。 Example 1 is a case of shipping steel material to be subjected to induction heat treatment after being processed into a part shape on the customer side. When shipping steel material, not only composition information but also Mo solid solution information and precipitation information in the vicinity of the surface layer. By providing as quality control information, it is an example that enables the customer to ensure fatigue characteristics after induction heat treatment or change the induction heat treatment conditions.
表1に示す鋼組成（Fe以外の主要組成のみ示す）からなる鋼素材を溶製転炉-連続鋳造プロセスにより溶製し、300×400mmの鋳片をブレークダウン工程（角型鋳片より棒鋼圧延用のビレットに成型する工程）を経て150mm角ビレットに粗圧延した鋼を、1050℃および1250℃で0.5h保持後、24mmφの棒鋼に熱間圧延した。熱間圧延時の仕上げ温度は900℃とし、0.5〜1℃/sの冷却速度で室温まで冷却した。
このようにして得られた２種の鋼材A、Bについて、表面1mm以内のMoの固溶量と析出量を調査した。さらに、中央偏析が問題になる鋼材中央部より無作為にサンプリングし、サイズ1μm以上の析出物等の有無を評価した。分析方法は以下の通りである。
A steel material consisting of the steel composition shown in Table 1 (only the main composition other than Fe is shown) is melted by a smelting converter-continuous casting process, and a 300 x 400 mm slab is broken down (from a square slab to a bar The steel roughly rolled into a 150 mm square billet through the step of forming into a billet for rolling was held at 1050 ° C. and 1250 ° C. for 0.5 h, and then hot rolled into a 24 mmφ bar steel. The finishing temperature at the time of hot rolling was 900 ° C., and it was cooled to room temperature at a cooling rate of 0.5 to 1 ° C./s.
With respect to the two types of steel materials A and B thus obtained, the solid solution amount and precipitation amount of Mo within 1 mm of the surface were investigated. Furthermore, random sampling was performed from the central part of the steel material where central segregation becomes a problem, and the presence or absence of precipitates having a size of 1 μm or more was evaluated. The analysis method is as follows.
上記鋼材A、Bから適当な大きさの試験片を切り出し、10%AA系電解液中（10%アセチルアセトン-1%塩化テトラメチルアンモニウム-メタノール）で電流密度20mA/cm2で0.2gだけ定電流電解後、表面に析出物等が付着している試験片を電解液から取り出して、ヘキサメタリン酸ナトリウム水溶液（以下SHMP水溶液）500mg/l中に浸漬し、超音波振動を付与して、析出物等を試験片から剥離しSHPM水溶液中に分離した。
次いで、この析出物等を含むSHMP水溶液に対してICP発光分光分析装置を用いて分析し、当該SHMP水溶液中のMoの絶対量を測定した。次いで、Moの絶対量を電解重量で除して、析出物等に含まれるMo量を得た。なお、電解重量は、析出物等剥離後の試料に対して重量を測定し、電解前の試料重量から差し引くことで求めた。
また、Moの固溶量の定量は以下のように実施した。上記電解後の電解液を分析溶液とし、ICP質量分析法を用いてMoおよび比較元素としてFeの液中濃度を測定した。得られた濃度を基に、Feに対するMoの濃度比をそれぞれ算出し、さらに、試料中のFeの含有量を乗じることで、Moの固溶量を求めた。なお、試料中のFeの含有量は、表1に示したFe以外の組成値の合計を100mass％から減算することで求めることができる。
これら析出物等に含まれるMo量とMoの固溶量は、試験鋼材の全組成を100mass%とした場合の値である。
また、サイズ１μm以上の析出物の有無の評価は以下のとおりである。
上記鋼材A、Bの鋼材中央部よりサンプリングした試料を適当な大きさの試験片を切り出し、10%AA系電解液中（10%アセチルアセトン-1%塩化テトラメチルアンモニウム-メタノール）で電流密度20mA/cm2で0.2gだけ定電流電解後、表面に析出物等が付着している試験片を電解液から取り出して、ヘキサメタリン酸ナトリウム水溶液（以下SHMP水溶液）500mg/l中に浸漬し、超音波振動を付与して、析出物等を試験片から剥離しSHPM水溶液中に分離した。
次いで、この析出物等を含むSHMP水溶液を、フィルタ孔径１μmのフィルタを用いてろ過し、ろ過後のフィルタ上の残渣に対してICP発光分光分析装置を用いて分析し、ろ過後のフィルタ上の残渣のMoの絶対量を測定した。次いで、Moの絶対量を電解重量で除して、サイズ1nm以上に分類された析出物等中に含まれるMoの含有量を求めた。なお、電解重量は、析出物等剥離後の試験片に対して重量を測定し、電解前の試験片重量から差し引くことで求めた。このMoの含有量は、試験鋼材の全組成を100mass%とした場合の値である。1μm以上の析出物中のMo量が0.2mass%以上では、顧客における熱処理後に、十分な固溶Mo量が確保できない。一方、1μm以上の析出物中のMo量が0.2mass%未満に抑制されていれば、熱処理後に、十分なねじり疲労強度を達成できる。
得られた結果を表1に鋼組成と併せて示す。
A test piece of an appropriate size was cut out from the steel materials A and B, and the current was constant at 0.2 g at a current density of 20 mA / cm 2 in 10% AA electrolyte (10% acetylacetone-1% tetramethylammonium chloride-methanol). After electrolysis, remove the test piece with deposits etc. on the surface from the electrolyte and immerse it in 500mg / l of sodium hexametaphosphate aqueous solution (hereinafter SHMP aqueous solution) to give ultrasonic vibrations. Was peeled from the test piece and separated into an aqueous SHPM solution.
Next, the SHMP aqueous solution containing the precipitates and the like was analyzed using an ICP emission spectroscopic analyzer, and the absolute amount of Mo in the SHMP aqueous solution was measured. Next, the absolute amount of Mo was divided by the electrolytic weight to obtain the amount of Mo contained in the precipitates. In addition, the electrolysis weight was calculated | required by measuring weight with respect to the sample after peeling, such as a deposit, and subtracting from the sample weight before electrolysis.
Further, the determination of the solid solution amount of Mo was carried out as follows. The electrolytic solution after the electrolysis was used as an analysis solution, and the concentrations of Mo and Fe as a comparative element were measured using ICP mass spectrometry. Based on the obtained concentration, the concentration ratio of Mo to Fe was calculated, and the solid solution amount of Mo was determined by multiplying the Fe content in the sample. Note that the Fe content in the sample can be obtained by subtracting the total of composition values other than Fe shown in Table 1 from 100 mass%.
The amount of Mo and the solid solution amount of Mo contained in these precipitates and the like are values when the total composition of the test steel is 100 mass%.
Moreover, the evaluation of the presence or absence of precipitates having a size of 1 μm or more is as follows.
Samples sampled from the central part of the steel materials A and B were cut out to a suitable size, and the current density was 20 mA / in 10% AA-based electrolyte (10% acetylacetone-1% tetramethylammonium chloride-methanol). After constant-current electrolysis of 0.2 g at cm 2 , remove the test piece with deposits etc. on the surface from the electrolyte and immerse it in 500 mg / l of sodium hexametaphosphate aqueous solution (hereinafter referred to as SHMP aqueous solution). And the precipitates were peeled off from the test piece and separated into an aqueous SHPM solution.
Next, the SHMP aqueous solution containing the precipitates and the like is filtered using a filter having a filter pore diameter of 1 μm, and the residue on the filtered filter is analyzed using an ICP emission spectroscopic analyzer. The absolute amount of Mo in the residue was measured. Next, the absolute amount of Mo was divided by the electrolytic weight, and the content of Mo contained in precipitates and the like classified into sizes of 1 nm or more was determined. The electrolytic weight was determined by measuring the weight of the test piece after separation of deposits and the like and subtracting it from the weight of the test piece before electrolysis. The Mo content is a value when the total composition of the test steel is 100 mass%. If the amount of Mo in the precipitate of 1 μm or more is 0.2 mass% or more, a sufficient amount of solute Mo cannot be secured after heat treatment by the customer. On the other hand, if the amount of Mo in the precipitate of 1 μm or more is suppressed to less than 0.2 mass%, sufficient torsional fatigue strength can be achieved after the heat treatment.
The obtained results are shown in Table 1 together with the steel composition.
表1は、鋼組成と、上記分析により得られた析出物等の情報を示しており、顧客に提供する部品形状に加工後、高周波熱処理される鋼材に対する品質管理情報である。
表1より、鋼種Ａ、Ｂは、鋼組成としてはほぼ同一にも関わらず、表面におけるMoの存在状態が変化している。鋼Aにおいては、表面におけるMoの固溶量が0.2mass%以下と低く、サイズが1μm以上の析出物が存在し、これらに含まれるMo量が0.2mass%を越えている。ビレット再加熱温度が低かったため、素材鋳造時のMo偏析が解消されなかったと考えられる。一方、鋼Bにおいては、スラブ加熱時にも固溶しない(Ti,Mo)(C,N)等の未固溶析出分はあるものの、0.3mass%以上の固溶量が確保されている。
Table 1 shows the steel composition and information such as precipitates obtained by the above analysis, and is quality control information for steel materials that are subjected to induction heat treatment after being processed into a part shape provided to the customer.
From Table 1, the steel types A and B have the same Mo composition on the surface, although the steel compositions are almost the same. In Steel A, the amount of solid solution of Mo on the surface is as low as 0.2 mass% or less, and precipitates having a size of 1 μm or more exist, and the amount of Mo contained in these exceeds 0.2 mass%. It is considered that Mo segregation during material casting was not resolved because the billet reheating temperature was low. On the other hand, in Steel B, a solid solution amount of 0.3 mass% or more is ensured although there are undissolved precipitates such as (Ti, Mo) (C, N) which do not dissolve during slab heating.
次いで、以下に記載の方法によりねじり疲労強度を測定し、上記品質管理情報の内容を確認した。
＜ねじり疲労強度＞
上記素材棒鋼から、平行部：20mmφ、応力集中係数α＝1.5の切欠きを有するねじり試験片を作成し、周波数：15kHzの高周波焼入れ装置を用いて、昇温速度600℃/s、到達温度900℃の1回の焼入れ処理を施し、170℃、30分の条件で焼き戻した後、ねじり疲労試験を実施した。この時のねじり疲労試験は、JIS Z 2273に準じて、最大トルク：4900 N・m(=500kgf・m)のねじり疲労試験機を用いて、両振りで応力条件を変えて行い、1×105回の寿命となる応力を疲労強度として評価した。得られた結果を表2に示す。
Next, the torsional fatigue strength was measured by the method described below, and the contents of the quality control information were confirmed.
<Torsional fatigue strength>
A torsion test piece having a notch with a parallel part: 20 mmφ and a stress concentration factor α = 1.5 was created from the above bar steel, and using a high-frequency quenching device with a frequency: 15 kHz, a heating rate of 600 ° C./s and an ultimate temperature of 900 A torsional fatigue test was conducted after tempering at 170 ° C. for 30 minutes after a single quenching treatment at ℃. The torsional fatigue test at this time was conducted in accordance with JIS Z 2273, using a torsional fatigue tester with a maximum torque of 4900 N · m (= 500 kgf · m), changing the stress conditions with both swings. The stress that resulted in the life of 5 times was evaluated as fatigue strength. The results obtained are shown in Table 2.
表2より、鋼種Ａではねじり疲労強度が劣っている。一方、鋼種Ｂでは、優れたねじり疲労特性が得られている。
以上の結果から、表面におけるMoの固溶量の大小に応じて、高周波熱処理後のねじり疲労特性が変化しており、表面におけるMoの固溶量が0.2mass%以下と低い鋼種Aにおいてはねじり疲労特性が明らかに劣位となっていることが確認された。
すなわち、本発明の品質管理方法により得られ、顧客へ提供されるMoの固溶情報は、顧客側にて部品形状に加工後、高周波熱処理される場合に非常に重要であることがわかる。
From Table 2, the torsional fatigue strength is inferior in steel type A. On the other hand, in steel type B, excellent torsional fatigue characteristics are obtained.
From the above results, the torsional fatigue characteristics after induction heat treatment change according to the amount of Mo solid solution on the surface, and in the case of steel type A where the solid solution amount of Mo on the surface is as low as 0.2 mass% or less It was confirmed that the fatigue characteristics were clearly inferior.
In other words, it can be seen that the solid solution information of Mo obtained by the quality control method of the present invention and provided to the customer is very important when the customer side performs high-frequency heat treatment after processing into a part shape.
素材提供の時点でHAZ部における炭化物形成の可能性が低い鋼組成であることを示すとともに、再現溶接熱サイクル試験によってCr系炭化物形成の情報を提供する例について説明する。 An example will be described in which the steel composition has a low possibility of carbide formation in the HAZ part at the time of material provision, and information on Cr-based carbide formation is provided by a reproducible welding thermal cycle test.
表３に示す鋼組成（Fe以外の主要組成のみ示す）からなる鋼素材を溶製転炉-連続鋳造プロセスにより溶製し、100kg鋼塊に鋳造してから熱間鍛造したのち、1250℃に加熱した後、モデルシームレス圧延機を用いた熱間加工により造管し、外径65mm×肉厚5.5mmの継目無鋼管とした。なお、造管後、空冷した。
このようにして得られた２種の鋼材Ｃ、Ｄについて、HAZ部（再現溶接熱サイクル試験材）と母材のCrの析出量を調査した。分析方法は以下の通りである。
A steel material consisting of the steel composition shown in Table 3 (only the main composition other than Fe is shown) is melted by a smelting converter-continuous casting process, cast into a 100 kg steel ingot, hot forged, and then heated to 1250 ° C. After heating, the pipe was formed by hot working using a model seamless rolling mill to obtain a seamless steel pipe having an outer diameter of 65 mm and a wall thickness of 5.5 mm. In addition, it air-cooled after pipe making.
For the two types of steel materials C and D thus obtained, the HAZ part (reproduced welding heat cycle test material) and the amount of Cr deposited on the base material were investigated. The analysis method is as follows.
上記鋼材Ｃ、Ｄから適当な大きさの試験片を切り出し、10%AA系電解液中（10%アセチルアセトン-1%塩化テトラメチルアンモニウム-メタノール）で電流密度20mA/cm2で0.2gだけ定電流電解後、表面に析出物等が付着している試験片を電解液から取り出して、ヘキサメタリン酸ナトリウム水溶液（以下SHMP水溶液）500mg/l中に浸漬し、超音波振動を付与して、析出物等を試験片から剥離しSHPM水溶液中に分離した。
次いで、この析出物等を含むSHMP水溶液に対してICP発光分光分析装置を用いて分析し、当該SHMP水溶液中のCrの絶対量を測定した。次いで、Crの絶対量を電解重量で除して、析出物等に含まれるCr量を得た。なお、電解重量は、析出物等剥離後の試料に対して重量を測定し、電解前の試料重量から差し引くことで求めた。これら析出物等に含まれるCr量は、試験鋼材の全組成を100mass%とした場合の値である。
得られた結果を表３に鋼組成と併せて示す。
A test piece of an appropriate size is cut out from the above steel materials C and D, and a constant current of 0.2 g at a current density of 20 mA / cm 2 in 10% AA electrolyte (10% acetylacetone-1% tetramethylammonium chloride-methanol). After electrolysis, remove the test piece with deposits etc. on the surface from the electrolyte and immerse it in 500mg / l of sodium hexametaphosphate aqueous solution (hereinafter SHMP aqueous solution) to give ultrasonic vibrations. Was peeled from the test piece and separated into an aqueous SHPM solution.
Next, the SHMP aqueous solution containing the precipitates and the like was analyzed using an ICP emission spectroscopic analyzer, and the absolute amount of Cr in the SHMP aqueous solution was measured. Next, the absolute amount of Cr was divided by the electrolytic weight to obtain the amount of Cr contained in the precipitates. In addition, the electrolysis weight was calculated | required by measuring weight with respect to the sample after peeling, such as a deposit, and subtracting from the sample weight before electrolysis. The amount of Cr contained in these precipitates and the like is a value when the total composition of the test steel is 100 mass%.
The obtained results are shown in Table 3 together with the steel composition.
表３は、鋼組成と、上記分析により得られた析出物等の情報を示しており、顧客に提供する鋼材の品質管理情報である。
表３より、鋼Cでは炭素レベルが高いのに加えて、強い炭化物形成元素を一切含有していない。この結果より、HAZ部においてCr炭化物が形成し、粒界応力腐食割れが予想される。一方、鋼Dにおいては、炭素レベルが抑制され、かつTiが添加されまたは含有しており、母材はもちろんのことHAZ部においてもCrの炭化物析出は確認されない。この結果より、粒界応力腐食割れは抑制されると予想される。
Table 3 shows the steel composition and information such as precipitates obtained by the above analysis, and is the quality control information of the steel material provided to the customer.
From Table 3, Steel C does not contain any strong carbide forming elements in addition to its high carbon level. From this result, Cr carbide is formed in the HAZ part, and intergranular stress corrosion cracking is expected. On the other hand, in Steel D, the carbon level is suppressed and Ti is added or contained, and precipitation of Cr carbide is not confirmed in the HAZ part as well as the base material. From this result, intergranular stress corrosion cracking is expected to be suppressed.
次いで、本実施例では、以下に記載の方法により再現溶接熱サイクル試験を行い、粒界応力腐食割れの有無を確認した。
＜再現溶接熱サイクル試験＞
再現溶接熱サイクル試験は、例えば1300℃、1s保持の後、800℃〜500℃の冷却時間を9sとし、その後450℃、180ｓの焼戻しを模擬する。このようにして得た素材より、厚み2mm,幅15mm長さ75mmの試験片を切り出し、U曲げ応力腐食割れ試験（JIS G 0576）に供した。U曲げ応力腐食割れ試験は、試験片を曲率8mmでU字型に曲げ、腐食環境中に168h暴露後、試験片断面について100倍の光学顕微鏡での割れの有無を評価した。なお、腐食環境は、液温100℃、CO2圧：0.1MPa, pH:2.0のNaCl液とした。
Next, in this example, a reproducible welding heat cycle test was performed by the method described below, and the presence or absence of intergranular stress corrosion cracking was confirmed.
<Reproduction welding thermal cycle test>
In the reproducible welding heat cycle test, for example, after holding at 1300 ° C. for 1 s, the cooling time from 800 ° C. to 500 ° C. is set to 9 s, and then tempering at 450 ° C. and 180 s is simulated. A test piece having a thickness of 2 mm, a width of 15 mm, and a length of 75 mm was cut out from the material thus obtained and subjected to a U bending stress corrosion cracking test (JIS G 0576). In the U-bending stress corrosion cracking test, the specimen was bent into a U shape with a curvature of 8 mm, exposed to 168 hours in a corrosive environment, and the cross section of the specimen was evaluated for cracking with a 100-fold optical microscope. The corrosive environment was a NaCl solution having a liquid temperature of 100 ° C., a CO 2 pressure of 0.1 MPa, and a pH of 2.0.
結果は、鋼種Ｃでは、粒界応力腐食割れが発生しているが、鋼種Ｄでは発生していなかった。
以上の結果から、鋼Cでは炭素レベルが高いのに加えて、強い炭化物形成元素を一切含有していない結果、HAZ部においてCr炭化物が形成し、結果的にU曲げ応力腐食割れ試験で割れが発生したと考えられる。一方、鋼Dにおいては、炭素レベルが抑制され、かつTiが添加されまたは含有しており、母材はもちろんのことHAZ部においてもCrの炭化物析出は確認されない結果、U曲げ応力腐食割れ試験で割れが発生しなかったと考えられる。
以上より、粒界応力腐食割れは、HAZ部と母材のCrの析出量に関係しており、本発明の品質方法により得られ、顧客に提供されるCrの析出量の情報は、出荷された素材が施工現場で溶接された際に粒界応力腐食割れ発生しないようにするための品質管理情報として非常に重要であることがわかる。
As a result, in the steel type C, intergranular stress corrosion cracking occurred, but in the steel type D, it did not occur.
From the above results, in addition to the high carbon level of steel C, steel carbide does not contain any strong carbide-forming elements. As a result, Cr carbide is formed in the HAZ part, resulting in cracks in the U bending stress corrosion cracking test. It is thought that it occurred. On the other hand, in Steel D, the carbon level is suppressed, and Ti is added or contained, and as a result of the precipitation of Cr carbide in the HAZ part as well as the base metal, it was confirmed in the U bending stress corrosion cracking test. It is thought that no cracks occurred.
From the above, intergranular stress corrosion cracking is related to the amount of Cr precipitation in the HAZ part and the base metal, and the information on the amount of Cr precipitation obtained by the quality method of the present invention and provided to the customer is shipped. It can be seen that this is very important as quality control information for preventing the occurrence of intergranular stress corrosion cracking when the material is welded at the construction site.
次に、ラインパイプ用高強度鋼の特性に甚大影響を及ぼす可能性の高い粗大な介在物・析出物に関する管理事例を示す。 Next, a management example of coarse inclusions / precipitates that are likely to have a great influence on the properties of high-strength steel for line pipes will be shown.
表４に示す鋼組成（Fe以外の主要組成のみ示す）からなる鋼素材を溶製転炉-連続鋳造プロセスにより溶製し、1250℃で0.5h保持後、熱間圧延し17.5mmの熱延鋼帯とした。このとき、熱間圧延時の仕上げ温度は820℃とし、冷却停止温度480℃までの冷却速度を15℃/sに制御した。
このようにして得られた２種の鋼材Ｅ、Ｆについて、鋼材板厚1/4と、中央偏析が問題になる鋼材板厚1/2より無作為に各々10箇所サンプリングし、サイズが1μm以上の析出物等に含有されるNb量を定量して、10箇所の平均値として示した。分析方法は以下の通りである。
A steel material composed of the steel composition shown in Table 4 (only the main composition other than Fe is shown) is melted by a melting converter-continuous casting process, held at 1250 ° C for 0.5 h, hot rolled, and hot rolled to 17.5 mm It was a steel strip. At this time, the finishing temperature during hot rolling was 820 ° C., and the cooling rate up to the cooling stop temperature of 480 ° C. was controlled to 15 ° C./s.
For the two types of steel materials E and F obtained in this way, 10 samples are randomly sampled from the steel plate thickness 1/4 and the steel plate thickness 1/2 where central segregation becomes a problem, and the size is 1 μm or more. The amount of Nb contained in the precipitates and the like was quantified and shown as an average value at 10 locations. The analysis method is as follows.
上記鋼材Ｅ、Ｆから適当な大きさの試験片を切り出し、10%AA系電解液中（10%アセチルアセトン-1%塩化テトラメチルアンモニウム-メタノール）で電流密度20mA/cm2で0.2gだけ定電流電解後、表面に析出物等が付着している試験片を電解液から取り出して、ヘキサメタリン酸ナトリウム水溶液（以下SHMP水溶液）500mg/l中に浸漬し、超音波振動を付与して、析出物等を試験片から剥離しSHPM水溶液中に分離した。
次いで、析出物等を含むSHMP水溶液を、孔径1μmのフィルタでろ過し、ろ過後のフィルタ上の残渣に対してICP発光分光分析装置を用いて分析し、フィルタ上の残渣中のNbの絶対量を測定した。次いで、Nbの絶対量を電解重量で除して、析出物等に含まれるNb量を得た。なお、電解重量は、析出物等剥離後の試料に対して重量を測定し、電解前の試料重量から差し引くことで求めた。これら析出物等に含まれるNb量は、試験鋼材の全組成を100mass%とした場合の値である。
得られた結果を表４に鋼組成と併せて示す。
A test piece of an appropriate size is cut out from the above steel materials E and F, and the current is constant at 0.2 g at a current density of 20 mA / cm 2 in 10% AA electrolyte (10% acetylacetone-1% tetramethylammonium chloride-methanol). After electrolysis, remove the test piece with deposits etc. on the surface from the electrolyte and immerse it in 500mg / l of sodium hexametaphosphate aqueous solution (hereinafter SHMP aqueous solution) to give ultrasonic vibrations. Was peeled from the test piece and separated into an aqueous SHPM solution.
Next, the SHMP aqueous solution containing precipitates and the like is filtered with a filter having a pore size of 1 μm, and the residue on the filter after filtration is analyzed using an ICP emission spectrometer. The absolute amount of Nb in the residue on the filter Was measured. Next, the absolute amount of Nb was divided by the electrolytic weight to obtain the amount of Nb contained in the precipitates. In addition, the electrolysis weight was calculated | required by measuring weight with respect to the sample after peeling, such as a deposit, and subtracting from the sample weight before electrolysis. The amount of Nb contained in these precipitates and the like is a value when the total composition of the test steel is 100 mass%.
The obtained results are shown in Table 4 together with the steel composition.
表4より、鋼Fにおいては、Nbの析出がわずかである。一方、鋼Eにおいては鋼組成の僅かなバランスの違いと素材加熱条件のずれによって中央偏析が回避できず、結果的に素材中央部においてNbの析出が確認された。このような素材はすぐさま水素誘起割れを起こすとは言えないものの、使用中に割れが発生し、大きな事故につながりかねない。製造側はこのような情報に基づき、出荷是非決定や再製造（用途変更）の実施をすることができる。 From Table 4, in the steel F, the precipitation of Nb is slight. On the other hand, in Steel E, central segregation could not be avoided due to a slight difference in the balance of the steel composition and a difference in raw material heating conditions, and as a result, precipitation of Nb was confirmed in the central part of the raw material. Although such materials cannot be said to cause hydrogen-induced cracking immediately, they can crack during use, leading to a major accident. Based on such information, the manufacturing side can decide whether to ship or remanufacture (use change).
以上説明したように、本発明による品質管理法は、信頼性の高い鋼材を顧客に提供する上で、標準的な情報提供方法となる可能性が大きく、自動車、造船、土木および建築などの材料として出荷する際に好適に用いることができる。 As described above, the quality control method according to the present invention is likely to be a standard information providing method in providing highly reliable steel materials to customers, and is used for materials such as automobiles, shipbuilding, civil engineering and construction. Can be suitably used when shipping.
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| RU2445607C1 (en) * | 2010-11-02 | 2012-03-20 | Учреждение Российской академии наук Институт высокотемпературной электрохимии Уральского отделения РАН | Method of inspecting multicomponent oxides for formation and stability of solid solutions with fluorite structure type |
| CN104260094A (en) * | 2014-09-16 | 2015-01-07 | 深圳市佳晨科技有限公司 | Robot fault processing system and robot fault processing method |
| CN114850465A (en) * | 2022-06-15 | 2022-08-05 | 北京科技大学 | Molten steel castability prediction system and method |
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