【発明の詳細な説明】[Detailed description of the invention]
この発明は焼入れ性向上のため溶鋼中へ添加す
るボロン処理鋼用添加剤の改良に関する。
従来焼入れ性を向上すべく溶鋼中へ添加するボ
ロンは、脱窒、脱酸用のFe―Tiや、金属AlとFe
―ＢまたはFe―Ti―Ｂなどとともに取鍋中へ予
め投入し、これに溶鋼を注入して混合していた。
しかしこの方法では溶鋼中に均一にボロンを添加
できないと共に、取鍋中のスラグにも一部が接触
反応されるため、ボロンの歩留りが悪い欠点があ
つた。
この発明はかかる欠点を除去する目的でなされ
たもので、適宜形状のアルミニウムブロツクに、
B19〜23％、C0.1％以下、Si2.0％以下、Al12％以
下、残部Feよりなるボロン合金金鉄の粒状物を
上記アルミニウムブロツクの重量比1.0に対して
0.2〜0.3の割合で混合したボロン処理鋼用添加剤
を提供して、添加剤の歩留りの向上とアルミニウ
ム残留量のバラツキ低減を図ろうとするものであ
る。
以下この発明の一実施例を図面を参照して詳述
する。
成分範囲がB19〜23％，C0.1％以下、Si2.0％以
下、Al12％以下、残部Feよりなる粒径が５〜30
mmのボロン合金鉄粒子１を、第１図ａに示す砲弾
型、または第１図ｂに示す楔型もしくは第１図ｃ
に示す十字楔型に形成したアルミニウムブロツク
２内に、アルミニウムブロツク２の重量比1.0に
対してボロン合金鉄の重量が0.2〜0.3となる配合
比でほぼ均一に混入し、これを添加装置３のプラ
ンジヤ４に第２図に示すように取付けて、アーク
炉で溶製し、かつ取鍋５に収容した溶鋼中へ投入
添加する。このときの溶鋼の温度は1600〜1650
℃、また添加剤は溶鋼中で上下左右に移動させな
がら20〜40秒間保持した後引き上げた。
上記のようにして添加剤を添加した溶鋼中のア
ルミニウム及びボロン量の変動は次の表―１の通
りであつた。なお比較のため、取鍋中に予め添加
剤を投入し、これに溶鋼を注入する従来法による
アルミニウム・ボロン量の変動も同時に記載し
た。
〓〓〓〓
This invention relates to improvements in additives for boron-treated steel that are added to molten steel to improve hardenability. Traditionally, boron, which is added to molten steel to improve hardenability, is used for denitrification and deoxidation, Fe-Ti, metal Al and Fe.
-B or Fe-Ti-B, etc. were placed in a ladle in advance, and molten steel was poured into the ladle and mixed.
However, this method has the drawback that boron cannot be uniformly added to the molten steel and a portion of the slag in the ladle is also reacted by contact, resulting in a poor yield of boron. This invention was made for the purpose of eliminating such drawbacks, and it is possible to make an aluminum block of an appropriate shape.
Particles of boron alloy gold iron consisting of 19 to 23% B, 0.1% or less of C, 2.0% or less of Si, 12% or less of Al, and the balance Fe are added to the weight ratio of 1.0 of the above aluminum block.
The objective is to provide an additive for boron-treated steel mixed at a ratio of 0.2 to 0.3 in order to improve the yield of the additive and reduce the variation in the residual amount of aluminum. An embodiment of the present invention will be described in detail below with reference to the drawings. The composition range is B19-23%, C0.1% or less, Si2.0% or less, Al12% or less, the balance is Fe, and the particle size is 5-30.
mm boron alloy iron particles 1 are shaped into a bullet shape as shown in FIG. 1a, or a wedge shape as shown in FIG. 1b, or as shown in FIG.
Boron alloy iron is mixed almost uniformly into the cross-wedge-shaped aluminum block 2 shown in FIG. It is attached to the plunger 4 as shown in FIG. 2, and added to molten steel melted in an arc furnace and stored in a ladle 5. The temperature of the molten steel at this time is 1600 to 1650
℃, and the additive was held for 20 to 40 seconds while moving up and down and left and right in the molten steel, and then pulled out. The fluctuations in the amounts of aluminum and boron in the molten steel to which the additives were added as described above were as shown in Table 1 below. For comparison, changes in the amount of aluminum and boron due to the conventional method of adding additives to a ladle and pouring molten steel into the ladle are also shown. 〓〓〓〓
【表】
上記表―１で明らかなように、焼入性の安定化
に有効なAl，Ｂの添加歩留りと、Al，Ｂ残留量
のバラツキが従来法に比べて大きく改善され、そ
の結果この発明の添加剤を添加した鋳鋼の焼入れ
性は第３図ａの従来法に比べ第３図ｂに示すよう
にバラツキが少なくなり、また焼入れ性自体も高
く安定するようになつた。なお第３図ａ，ｂに示
す鋳鋼の成分範囲はともに、
C0.12〜0.18，Si0.30〜0.60，Mn0.80〜1.40，
Cr0.10〜0.70，Mo0.30以下であつた。
この発明は以上詳述したように、アルミニウム
ブロツク内にボロン合金鉄の粒状物を混入した状
態で溶鋼中に添加することから、溶鋼中でまずア
ルミニウムが溶融して脱窒、脱酸を十分行つた後
ボロン合金鉄が溶鋼中に溶け込むため、スラグと
ボロンが接触反応することもなく、これによつて
ボロンの添加歩留りが向上すると同時に、ボロン
添加量のバラツキも小さくできるため、焼入れ性
に有効な適正ボロン量を安定して得ることができ
るようになる。[Table] As is clear from Table 1 above, the addition yield of Al and B, which are effective in stabilizing hardenability, and the variation in residual amounts of Al and B have been greatly improved compared to the conventional method. The hardenability of the cast steel to which the additive of the invention was added had less variation as shown in FIG. 3b, compared to the conventional method shown in FIG. 3a, and the hardenability itself became high and stable. The composition ranges of the cast steel shown in Figure 3 a and b are as follows: C0.12~0.18, Si0.30~0.60, Mn0.80~1.40,
Cr was 0.10 to 0.70 and Mo was 0.30 or less. As described in detail above, this invention involves adding boron alloy iron particles mixed in an aluminum block to molten steel, so that the aluminum first melts in the molten steel and is sufficiently denitrified and deoxidized. Since the boron alloy iron melts into the molten steel after the molten steel is heated, there is no contact reaction between the slag and boron, which improves the boron addition yield and reduces the variation in the amount of boron added, which is effective for hardenability. This makes it possible to stably obtain an appropriate amount of boron.
【図面の簡単な説明】[Brief explanation of the drawing]
図面はこの発明の一実施例を示し、第１図ａ，
ｂ及びｃは添加剤の形状を示す斜視図、第２図は
添加状態を示す説明図、第３図ａは従来法の焼入
れ性を示す線図、第３図ｂはこの発明の添加剤を
投入した鋳鋼の焼入れ性を示す線図である。
〓〓〓〓
The drawings show an embodiment of the invention, and FIGS.
b and c are perspective views showing the shape of the additive, Fig. 2 is an explanatory drawing showing the state of addition, Fig. 3a is a diagram showing the hardenability of the conventional method, and Fig. 3b is a diagram showing the additive of the present invention. FIG. 2 is a diagram showing the hardenability of cast steel. 〓〓〓〓