JP3616463B2 - Rapid discrimination method for inclusions in steel - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、連続鋳造鋳型内の溶鋼中へのモールドフラックスの巻き込み量を評価するための、鋼中介在物の迅速判別法に関する。
【０００２】
【従来の技術】
近年、鋼の連続鋳造においては、鋳型内の溶鋼の流動を制御する技術、例えばモールド内電磁撹拌、電磁ブレーキによる浸漬ノズルの吐出流制御等の手段が多用されるようになってきたが、メニスカス近傍の流れの乱れあるいはノズル閉塞にともなう偏流の発生により、モールドフラックス（以下、「パウダー」という）が溶鋼中に巻き込まれる機会が多くなっている。
【０００３】
一方、鋼材の品質に対する要求が厳しくなり、タンディッシュからモールドへ供給される溶鋼の清浄度が高くなっているため、上記のようなパウダーの巻き込みに起因する介在物の製品欠陥に対する影響度がきわめて大きくなっている。
【０００４】
とくに、パウダー系の介在物は圧延時に延伸されるため製品欠陥の原因となり易く、強加工が施される製缶用素材あるいは自動車用鋼板の欠陥の原因の一つとなっている。したがって、連続鋳造の操業において、前述のようなパウダーの巻き込みを極力防止する必要があり、そのためには、鋳型内の溶鋼又は鋳片内のパウダー系介在物の量を簡便かつ迅速に評価して、連続鋳造の操業条件にフィードバックすることが必要になっている。
【０００５】
連続鋳造鋳片の介在物は、大別してスラグ系の介在物（脱酸生成物を含む）とパウダー系の介在物に分けられるが、従来この両者を識別するには、ＥＰＭＡその他の手段で介在物の組成を分析することが必要であった。
【０００６】
すなわち、連続鋳造鋳片の切断試料又は鋳型内溶鋼の汲み上げ試料から試験片を調製して、ＥＰＭＡ等により介在物組成の分析を行うものであるが、研磨等の試験片の調製と組成分析に多大の手間と時間を要し、パウダー系介在物の量に関する情報を迅速にフィードバックして、連続鋳造の操業条件に反映させることが困難であった。
【０００７】
【発明が解決しようとする課題】
上記のような従来技術の問題点に鑑み、本発明は介在物の組成分析を行うことなく、パウダー系介在物かスラグ系介在物かの判定を可能とする、迅速かつ簡便な判別法を提供することを目的とする。
【０００８】
また、これにより、パウダーの巻き込みの有無、巻き込み量の多少に関する情報をできるだけ短時間で得て、パウダー巻き込みのない連続鋳造の操業方法の確立に資することを目的とする。
【０００９】
【課題を解決するための手段】
連続鋳造のモールドフラックス（パウダー）は、ＣａＯ，ＳｉＯ２，Ｎａ２Ｏ，Ｆ等の成分を含み、その融点Ｔｍは通常低炭素鋼用で１１００〜１１５０℃である。溶鋼中に巻き込まれたパウダーは、一部溶鋼成分と反応し又は他の介在物と合体して組成が変化することがあるが、その融点の変化は比較的小さい。そこで、本発明の発明者らは、パウダー系介在物とスラグ系介在物の融点の差に着目し、試料を熱間で圧延することにより、この両者を識別する可能性があることを着想した。
【００１０】
なお、特開平１−３９５４７号公報には、「金属の純度等級を判定するために使用される試験片を作る方法」として、介在物を調査するための試料を圧延する方法が提案されている。しかし、これは同公報の第１図に見られるように、例えば丸棒材からその長手方向に直角に円板状の試料を切出して、これを圧延することにより介在物の集積帯を拡大・顕在化させて、介在物の検査を容易にしようとするものであって、上記のようなパウダー系介在物の迅速な判別を目的とするものではない。
【００１１】
本発明者らが種々検討した結果、パウダー系介在物の融点は元のパウダーの融点Ｔｍより０〜２００℃高い範囲内であること、したがってパウダー系介在物を含む鋳造材を上記の温度範囲で圧延すれば、パウダー系介在物はほぼ母材と同じように延伸変形されることを見出した。
【００１２】
一方、スラグ系介在物や耐火物起因の介在物の融点はおおむね溶鋼の融点近傍又はそれ以上であって、上記の温度範囲で圧延してもこれらの介在物はあまり変形されないことを知見した。
【００１３】
本発明は上記の知見に基いてなされたものであって、その要旨は、
（１）連続鋳造鋳型内の溶鋼から採取した試料に、当該鋳造時に使用したモールドフラックスの融点以上融点＋２００℃以下の温度で圧減比５０％以上の圧延加工を施し、圧延後の試料中の介在物のうち長径／短径比が次式となる範囲をパウダー系介在物と判別する鋼中介在物の迅速判別法である。
【００１４】
【数２】
ここで、Ｌ１：圧延後の試料中の介在物の長径
Ｌ２：圧延後の試料中の介在物の短径
Ｒｄ：圧減比（％）
である。
【００１６】
（２）また、前記連続鋳造鋳型内の溶鋼から採取した試料に替えて、連続鋳造鋳片から採取した試料を採用することを特徴とする前記（１）に記載の鋼中介在物の迅速判別法である。
【００１７】
（３）さらに、超音波探傷法を用いて、前記圧延後の試料中の介在物の長径及び短径を測定することを特徴とする前項（１）又は（２）に記載の鋼中介在物の迅速判別法である。
【００１８】
【発明の実施の形態】
本発明の鋼中介在物の迅速判別法は、連続鋳造鋳型内の溶鋼から採取し凝固させた試料又は連続鋳造鋳片の切断試料に、当該鋳造時に使用したパウダーの融点Ｔｍより０〜２００℃高い温度範囲で、圧減比５０％以上の圧延加工を施すことを特徴とする。
【００１９】
圧延加工を施すに際して、試料の形状は厚みがほぼ一様の板状であることが好ましいが、溶鋼から採取した円筒形のいわゆるタコツボ試料を板状に切断してもよく、或いは汲み上げた溶鋼を金型等で板状に固めてもよい。
【００２０】
試料の大きさにはとくに制限はなく、通常の介在物の検査に用いる試料と同程度の大きさであればよい。また、連続鋳造鋳片から板状の切断試料を切り出す場合は、その採取の位置や試料の大きさは検査の目的に応じて適宜定めればよい。
【００２１】
圧延加工に用いる圧延機は、圧延時の試験片の温度の制御が可能であればとくに制約はなく、例えば試験片製作用の小型圧延機を用いればよい。
【００２２】
本発明において、圧延時の試験片の温度を連続鋳造時に使用したパウダーの融点Ｔｍより０〜２００℃高い範囲内とするのは、後の実施例に示すように、Ｔｍ未満ではパウダー系介在物の変形量が小さく判別が困難になるためであり、Ｔｍ＋２００℃を超えると、パウダー系以外の介在物の内比較的融点の低いもの、例えばＣａＯ−Ａｌ２Ｏ３系介在物まで延伸されるおそれがあるためである。
【００２３】
また、本発明において、試験片の圧減比Ｒｄを５０％以上とするのは、介在物は常に完全な球形で凝固するとは限らず、Ｒｄ５０％以下では延伸された介在物か当初から楕円状の介在物かの判別が困難なこと、及び球状介在物でも低圧減比下でパウダー系介在物とその他の介在物との判別の精度が十分でないことによる。
【００２４】
なお、圧減比Ｒｄは、圧延前の試料の板厚をｔ１、圧延後の板厚をｔ２として、Ｒｄ＝（ｔ１−ｔ２）／ｔ１×１００（％）で定義される。
圧延された材料が圧延方向のみに一様に伸びた場合、母材の延伸比Ｅは下式で表わされる。
【００２５】
Ｅ＝１００／（１００−Ｒｄ）
しかし、被圧延材中の介在物の伸びはその変形抵抗によって異なり、延伸比は上記のＥより小さくなる。
【００２６】
本発明者らが実験的に検討した結果、パウダー系介在物をその融点Ｔｍより０〜２００℃高い温度範囲で圧延した時の延伸比は、Ｅの０．８〜１．０倍になることが確かめられた。一方、スラグ系の介在物の融点は上記の温度範囲より高いため、多くの場合程んど伸びずに破砕される。スラグ系介在物のうち比較的低融点のものでも、その延伸比は上記Ｅの０．７倍以下である。
【００２７】
したがって、本発明においては、圧延後の試料中の介在物のうち、長径／短径比が次式の範囲内の介在物をパウダー系介在物と判別する。
【００２８】
【数３】
ここで、Ｌ１，Ｌ２は圧延後の試料中の介在物の長径及び短径、Ｒｄは圧減比（％）である。
【００３０】
このように判別基準とする長径／短径比Ｌ０を母材の延伸比Ｅの０．８倍とすることによって、後の実施例に示すように、ほぼ確実にパウダー系介在物とその他の介在物とを判別することが可能になった。
【００３１】
本発明において、介在物の長径及び短径の測定を行うには、被検査材を研磨して光学顕微鏡で測定してもよい。しかし、測定を迅速に行うという観点からは超音波探傷法、中でも高周波超音波法を用いることが望ましい。
【００３２】
一般に、高周波の超音波により、鋼材中の介在物の大きさや数を検査するには、水浸垂直超音波探傷法が用いられる。これは表面を研削した被検査材を水中に静置し、超音波探触子を研削面に並行に走査して、各測定点でパルス状の超音波を被検査材表面に垂直に入射し、介在物部からの反射波を検出するものである。
【００３３】
垂直超音波探傷法により介在物の長径及び短径を測定するには、例えば、入射超音波を走査し、一定ピッチ（２０〜５０μｍ程度）の格子点で介在物部からの反射波の有無を判定し、コンピューターによる画像処理等の方法で、介在物の存在位置とその形状を表示することができる。また、同時にコンピューターでデータ処理して、（２）式を用いて個々の介在物がパウダー系かそれ以外かを判別することもできる。
【００３４】
本発明において問題となるパウダー系の介在物は、通常１００μｍ若しくはそれ以上の比較的大型のものであるから、１０ＭＨｚ程度以上の高周波超音波探傷装置を用いて、上述したような方法で比較的容易に個々の介在物の長径／短径比を測定することができる。
【００３５】
このように、超音波を用いて介在物の測定を行う場合、試料の調整や介在物の測定の時間が大幅に短縮される。鋳型内の溶鋼を汲み上げた試料を圧延して超音波検査する際に、試料の採取から超音波測定までを１〜２時間以内で行うことが可能である。したがって連々鋳操業の場合には、パウダー系介在物の量に関する情報をフィードバックして、連続鋳造の操業条件に反映させることも可能である。
【００３６】
【実施例】
連続鋳造鋳型内の溶鋼から採取した試料に試験圧延機で圧延加工を施し、本発明の方法による介在物の判別結果と従来法であるＥＰＭＡによる判別結果を比較した。鋳造鋼種は極低炭素のＡｌキルド鋼で、使用したパウダーはＣａＯ，ＳｉＯ２等を主成分とするもので、その融点は１１４０℃であった。
【００３７】
実施例は試料を１２００℃及び１３００℃に加熱し、圧減比（Ｒｄ）が５０％と８０％の２水準で圧延した場合で、比較例は同じ圧減比で１１００℃に試料を加熱して圧延した場合である。いずれも圧延後の試料を研磨して、特定の介在物に番号を付し、その介在物の長径／短径比（Ｌ１／Ｌ２）を顕微鏡で測定するとともに、ＥＰＭＡでその組成分析を行った。
【００３８】
表１に実施例及び比較例での圧延条件、介在物番号、Ｌ１／Ｌ２の測定値、本発明の方法による判定結果及びＥＰＭＡによる判定結果を示す。また、表２に各介在物のＥＰＭＡによる組成分析結果を示す。表１でＬ１／Ｌ２が（２）式で定められるＬ０より大きいものをパウダー系介在物と判定した。
【００３９】
表２において、Ｎａ２Ｏを含む介在物（１，４，５，７，８，９，１１，１３，１４番）はいずれもＳｉＯ２が２０〜４０％含まれており、パウダー系介在物と判断される。これに対して、その他のものはＮａ２Ｏが検出されずＳｉＯ２もおよそ５％以下である。その他の介在物は、ＣａＯ，Ａｌ２Ｏ３を主成分とし、少量のＭｇＯ，ＦｅＯ等を含むスラグ系の介在物と推定される。
【００４０】
表１に見られるように、試料加熱温度が本発明の条件内である実施例では、パウダー系とその他の介在物のＬ１／Ｌ２の値には明らかな差があり、全ての介在物について本発明の方法による判定とＥＰＭＡによる判定が一致した。一方、試料加熱温度がパウダーの融点より低い比較例では、パウダー系とその他の介在物のＬ１／Ｌ２は１．３以下でほとんど差がなく、本発明の方法による判別は困難であった。
【００４１】
【表１】
【表２】
【発明の効果】
本発明により、連続鋳造の鋳型内の溶鋼又は鋳片中の介在物がパウダー系のものかその他のものかを、介在物の組成分析を行うことなく簡便かつ迅速に判別することが可能になった。これにより、連続鋳造の操業中にパウダーの巻き込みに関する情報を得て、操業条件の修正を図ることができ、製品欠陥を低減するための手段として本発明の工業的意義は大きい。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rapid discrimination method for inclusions in steel for evaluating the amount of mold flux entrained in molten steel in a continuous casting mold.
[0002]
[Prior art]
In recent years, in continuous casting of steel, techniques for controlling the flow of molten steel in a mold, such as electromagnetic stirring in a mold and discharge flow control of an immersion nozzle by an electromagnetic brake, have been frequently used. Occurrence of uneven flow due to turbulence in the vicinity or nozzle blockage increases the chance of mold flux (hereinafter referred to as “powder”) being caught in molten steel.
[0003]
On the other hand, since the requirements for the quality of steel materials are becoming stricter and the cleanliness of the molten steel supplied from the tundish to the mold is high, the influence of inclusions on product defects due to the entrainment of powder as described above is extremely high. It is getting bigger.
[0004]
In particular, powder-type inclusions tend to cause product defects because they are stretched during rolling, and are one of the causes of defects in can-making materials or automobile steel plates that are subjected to strong processing. Therefore, in the continuous casting operation, it is necessary to prevent the entrainment of the powder as described above as much as possible. For that purpose, the amount of the molten steel in the mold or the powder-based inclusions in the slab is evaluated easily and quickly. It is necessary to provide feedback on the operating conditions of continuous casting.
[0005]
Inclusions in continuous cast slabs are broadly divided into slag inclusions (including deoxidation products) and powder inclusions. Conventionally, in order to distinguish between these, EPMA or other means are used. It was necessary to analyze the composition of the product.
[0006]
In other words, a test piece is prepared from a cut sample of a continuous cast slab or a pumped sample of molten steel in a mold, and the inclusion composition is analyzed by EPMA or the like. It took a lot of time and effort, and it was difficult to quickly feed back information on the amount of powder inclusions and reflect it in the operating conditions of continuous casting.
[0007]
[Problems to be solved by the invention]
In view of the above-described problems of the prior art, the present invention provides a quick and simple discrimination method that enables determination of powder inclusions or slag inclusions without analyzing the composition of inclusions. The purpose is to do.
[0008]
It is another object of the present invention to obtain information on the presence / absence of entrainment of powder and the amount of entrainment in as short a time as possible, and to contribute to the establishment of an operation method for continuous casting without entrainment of powder.
[0009]
[Means for Solving the Problems]
The continuous casting mold flux (powder) contains components such as CaO, SiO 2 , Na 2 O and F, and its melting point T m is usually 1100 to 1150 ° C. for low carbon steel. The powder entrained in the molten steel may partly react with the molten steel components or coalesce with other inclusions to change the composition, but its melting point change is relatively small. Therefore, the inventors of the present invention have focused on the difference in melting point between the powder inclusions and the slag inclusions, and have conceived that there is a possibility of discriminating between the two by rolling the sample hot. .
[0010]
JP-A-1-39547 proposes a method of rolling a sample for investigating inclusions as a “method of making a test piece used for determining a metal purity grade”. . However, as shown in FIG. 1 of the same publication, for example, a disc-shaped sample is cut out from a round bar at a right angle to its longitudinal direction, and rolled to expand the inclusion accumulation zone. It is intended to facilitate the inspection of inclusions by revealing it, and is not intended to promptly discriminate such powder inclusions.
[0011]
As a result of various studies by the present inventors, the melting point of the powder-based inclusions is in the range of 0 to 200 ° C. higher than the melting point T m of the original powder. It was found that the powder inclusions are stretched and deformed in the same manner as the base material.
[0012]
On the other hand, the melting point of inclusions derived from slag inclusions and refractories is generally near or higher than the melting point of molten steel, and it has been found that these inclusions are not significantly deformed even when rolled in the above temperature range.
[0013]
The present invention has been made on the basis of the above findings, and the gist thereof is as follows:
(1) A sample collected from molten steel in a continuous casting mold is subjected to rolling with a reduction ratio of 50% or more at a temperature not lower than the melting point of the mold flux used at the time of casting and not higher than 200 ° C. This is a rapid discrimination method for inclusions in steel, in which the range in which the major axis / minor axis ratio is the following formula among inclusions is discriminated from powder inclusions.
[0014]
[Expression 2]
Here, L 1 : major axis of inclusions in the sample after rolling L 2 : minor axis of inclusions in the sample after rolling R d : reduction ratio (%)
It is.
[0016]
(2) Moreover, it replaces with the sample extract | collected from the molten steel in the said continuous casting mold, The sample extract | collected from the continuous cast slab is employ | adopted, The rapid discrimination | determination of the inclusion in steel as described in said (1) characterized by the above-mentioned Is the law.
[0017]
(3) The inclusion in steel as described in (1) or (2) above, wherein the major axis and minor axis of the inclusion in the sample after rolling are measured using an ultrasonic flaw detection method. This is a rapid discrimination method.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The rapid discriminating method for inclusions in steel according to the present invention is based on a sample collected from molten steel in a continuous casting mold and solidified or a cut sample of a continuous cast slab from 0 to 200 from the melting point T m of the powder used at the time of casting. It is characterized by rolling at a reduction ratio of 50% or more in a high temperature range.
[0019]
When performing the rolling process, the shape of the sample is preferably a plate having a substantially uniform thickness, but a cylindrical so-called takotsubo sample taken from the molten steel may be cut into a plate shape, or the pumped molten steel It may be hardened into a plate shape with a mold or the like.
[0020]
There is no restriction | limiting in particular in the magnitude | size of a sample, What is necessary is just a magnitude | size comparable to the sample used for the test | inspection of a normal inclusion. Further, when a plate-like cut sample is cut out from the continuous cast slab, the sampling position and the size of the sample may be appropriately determined according to the purpose of the inspection.
[0021]
The rolling mill used for the rolling process is not particularly limited as long as the temperature of the test piece at the time of rolling can be controlled. For example, a small rolling mill for producing a test piece may be used.
[0022]
In the present invention, to a 0 to 200 ° C. higher range than the melting point T m of a powder using the temperature of the rolled upon the test piece at the time of continuous casting, as shown in the examples below, the powder system is less than T m This is because the amount of deformation of the inclusion is small and it is difficult to discriminate. When T m + 200 ° C. is exceeded, inclusions other than powder-based inclusions having a relatively low melting point, such as CaO—Al 2 O 3 -based inclusions. It is because there exists a possibility that it may be extended.
[0023]
Further, in the present invention, the to 50% or more圧減ratio R d of the test piece, the inclusions not always to be solidified in a complete sphere, R d initially or inclusions which are oriented at less than 50% Therefore, it is difficult to discriminate whether the inclusion is elliptical, and even the spherical inclusion is not sufficiently accurate to discriminate between powder inclusions and other inclusions under a low pressure reduction ratio.
[0024]
The reduction ratio R d is defined as R d = (t 1 −t 2 ) / t 1 × 100 (%), where t 1 is the thickness of the sample before rolling and t 2 is the thickness after rolling. Is done.
When the rolled material extends uniformly only in the rolling direction, the stretch ratio E of the base material is expressed by the following equation.
[0025]
E = 100 / (100−R d )
However, the elongation of inclusions in the material to be rolled varies depending on the deformation resistance, and the stretch ratio is smaller than E.
[0026]
The present inventors have studied experimentally, draw ratio upon rolling powder inclusions at 0 to 200 ° C. temperature range higher than its melting point T m is made to 0.8 to 1.0 times the E It was confirmed. On the other hand, since the melting point of the slag inclusions is higher than the above temperature range, in many cases, the slag inclusions are crushed without substantially extending. Even if the slag inclusions have a relatively low melting point, the stretch ratio is 0.7 times or less of E.
[0027]
Therefore, in the present invention, among the inclusions in the sample after rolling, inclusions whose major axis / minor axis ratio is within the range of the following formula are determined as powder inclusions.
[0028]
[Equation 3]
Here, L 1 and L 2 are the major and minor diameters of inclusions in the sample after rolling, and R d is the reduction ratio (%).
[0030]
In this way, by setting the major axis / minor axis ratio L 0 as a discrimination criterion to be 0.8 times the base material stretch ratio E, as shown in the following examples, the powder inclusions and the other It became possible to distinguish between inclusions.
[0031]
In the present invention, in order to measure the major axis and minor axis of inclusions, the material to be inspected may be polished and measured with an optical microscope. However, it is desirable to use an ultrasonic flaw detection method, particularly a high-frequency ultrasonic method, from the viewpoint of performing measurement quickly.
[0032]
In general, a water immersion vertical ultrasonic flaw detection method is used to inspect the size and number of inclusions in a steel material by high-frequency ultrasonic waves. In this method, the test material whose surface is ground is left in water, the ultrasonic probe is scanned in parallel with the grinding surface, and pulsed ultrasonic waves are incident on the test material surface perpendicularly at each measurement point. The reflected wave from the inclusion part is detected.
[0033]
In order to measure the major axis and minor axis of the inclusion by the vertical ultrasonic flaw detection method, for example, the incident ultrasonic wave is scanned, and the presence or absence of the reflected wave from the inclusion part is determined at a lattice point with a constant pitch (about 20 to 50 μm). The presence position of the inclusion and its shape can be displayed by a method such as image processing by a computer. At the same time, data processing can be performed by a computer, and it is also possible to determine whether the individual inclusions are powder-based or otherwise by using the formula (2).
[0034]
Since the powder-type inclusions which are a problem in the present invention are usually relatively large in size of 100 μm or more, using a high-frequency ultrasonic flaw detector of about 10 MHz or more, it is relatively easy by the method described above. The major axis / minor axis ratio of each inclusion can be measured.
[0035]
In this way, when measuring inclusions using ultrasonic waves, the time for sample preparation and inclusion measurement is greatly reduced. When rolling a sample from which molten steel in the mold is pumped and ultrasonically inspecting, it is possible to perform the sample collection to ultrasonic measurement within 1 to 2 hours. Therefore, in the case of continuous casting operation, it is also possible to feed back information on the amount of powder inclusions and reflect it in the operating conditions of continuous casting.
[0036]
【Example】
The sample taken from the molten steel in the continuous casting mold was rolled with a test rolling mill, and the discrimination result of inclusions by the method of the present invention was compared with the discrimination result by EPMA which is a conventional method. The cast steel was an ultra-low carbon Al killed steel, and the powder used was mainly composed of CaO, SiO 2, etc., and its melting point was 1140 ° C.
[0037]
In the examples, the sample was heated to 1200 ° C. and 1300 ° C., and the reduction ratio (R d ) was rolled at two levels of 50% and 80%. In the comparative example, the sample was heated to 1100 ° C. at the same reduction ratio. And rolling. In both cases, the rolled sample is polished, a specific inclusion is numbered, and the major axis / minor axis ratio (L 1 / L 2 ) of the inclusion is measured with a microscope, and the composition analysis is performed with EPMA. went.
[0038]
Table 1 shows rolling conditions, inclusion numbers, measured values of L 1 / L 2 , determination results by the method of the present invention, and determination results by EPMA in Examples and Comparative Examples. Table 2 shows the composition analysis results of each inclusion by EPMA. In Table 1, L 1 / L 2 to be greater than L 0 defined by the equation (2) determines that the powder type inclusions.
[0039]
In Table 2, inclusions containing Na 2 O (Nos. 1, 4, 5, 7, 8, 9, 11, 13, 14) all contain 20 to 40% SiO 2 , and powder inclusions It is judged. On the other hand, Na 2 O is not detected and SiO 2 is about 5% or less. Other inclusions are presumed to be slag inclusions containing CaO and Al 2 O 3 as main components and containing a small amount of MgO, FeO and the like.
[0040]
As can be seen in Table 1, in the examples where the sample heating temperature is within the conditions of the present invention, there is a clear difference between the L 1 / L 2 values of the powder system and other inclusions, and all inclusions The determination by the method of the present invention was consistent with the determination by EPMA. On the other hand, in the comparative example in which the sample heating temperature is lower than the melting point of the powder, L 1 / L 2 of the powder system and other inclusions is 1.3 or less, and there is almost no difference, and discrimination by the method of the present invention is difficult. .
[0041]
[Table 1]
[Table 2]
【The invention's effect】
According to the present invention, it is possible to easily and quickly discriminate whether the inclusions in the molten steel or slab in a continuous casting mold are powder-based or other inclusions without analyzing the composition of the inclusions. It was. Thereby, the information regarding the entrainment of the powder can be obtained during the operation of continuous casting, the operation conditions can be corrected, and the industrial significance of the present invention is great as a means for reducing product defects.
Claims (3)
Ｌ２：圧延後の試料中の介在物の短径
Ｒｄ：圧減比（％）The sample collected from the molten steel in the continuous casting mold is subjected to a rolling process at a reduction ratio of 50% or more at a temperature not lower than the melting point of the mold flux used at the time of casting and not higher than 200 ° C., and the inclusions in the sample after rolling are subjected to rolling. A method for quickly discriminating inclusions in steel in which the range in which the ratio of major axis / minor axis is expressed by the following equation is discriminated from powder inclusions.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21701396A JP3616463B2 (en) | 1996-08-19 | 1996-08-19 | Rapid discrimination method for inclusions in steel |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21701396A JP3616463B2 (en) | 1996-08-19 | 1996-08-19 | Rapid discrimination method for inclusions in steel |
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| JP3616463B2 true JP3616463B2 (en) | 2005-02-02 |
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| CN111829808A (en) * | 2020-06-15 | 2020-10-27 | 包头钢铁（集团）有限责任公司 | Sampling method for analyzing content of rare earth inclusions in steel casting blank |
| CN112284971A (en) * | 2020-09-01 | 2021-01-29 | 包头钢铁（集团）有限责任公司 | Method for judging physical and chemical property stability of casting powder in casting process |
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