【発明の詳細な説明】[Detailed description of the invention]
＜産業上の利用分野＞
本発明は耐摩耗性、耐食性に優れた連続鋳造用
クーリンググリツドに関するものである。
＜従来の技術＞
連続鋳造設備に於いて、鋳型を過通した直後の
鋳片を支持する方式として、ロール支持方式の他
にクーリングプレートやクーリンググリツドを用
いる方式がある。これは近年の鋳造スピードの高
速化に伴ない出現しブレークアウト防止、冷却効
率向上を意図したものである。この中でクーリン
グプレートは内部に冷却機構を有する為に銅ある
いは銅合金等熱伝導性が良い素材から成り、ロー
ル支持方式やクーリンググリツド方式と比べると
最も緩やかな冷却であり鋳片の表面欠陥をなくす
る作用がある。又クーリンググリツドは格子状
や、小判状突起を多数配設した形状をし、それに
開けられた数個の窓あるいは小判状突起の間から
冷却水を放出はするものの内部に冷却機構を持つ
事はなく従来からその素材は球状黒鉛鋳鉄が主で
あつた。即ち球状黒鉛鋳鉄中の黒鉛により熱間す
べり性を出すと共に耐焼付性を持たせようと意図
したものであり、使用につれ少しづつ摩耗して減
つて行くのは仕方がないとされていた。
＜発明が解決しようとする問題点＞
上記クーリングプレートは、使用と共に摩耗、
腐食による損耗を防ぐ為に耐久性に富む金属板を
グラツドしたり、セラミツク板をボルト止めした
りする対策が採られ、又ロールに対してはその母
材の素材の改良と共に表面に自溶性合金溶射被覆
層を施したり、肉盛溶接層を施す等の対策が採ら
れている。しかしクーリンググリツドは従来から
一種の消耗品という考え方が定着し、それ自体に
耐久性を持たせようとする様な事はなかつた。
上記球状黒鉛製のクーリンググリツドは、耐焼
付性に優れてはいるものの、使用につれ摩減して
いく為にその都度位置合わせをしなければならな
い、通常その取替周期が300〜400chと非常に短
く、しかも300chを越える頃になれば鋳片と当接
する部所は脱炭作用によりフエライト化してしま
い硬さが、Hv＜200まで低下（層厚は最大15mm）
する、更には素材が靭性に乏しいが為にクラツク
が生起し易い等種々の問題があつた。
本発明ではこの様な従来のクーリンググリツド
が有する諸問題を解決し、長期に渡つて安定して
用いる事が出来る連続鋳造用クーリンググリツド
を提供する事を目的とするものである。
＜問題点を解決する為の手段＞
上記本発明の目的を達成する為の手段は、次の
如くである、即ち一般構造用鋼から成るクーリン
ググリツド本体の少なくとも鋳片と当接する部所
に、Cr12〜16重量％、C0.5〜0.7重量％を含有す
るNi−Cr系自溶性合金溶射被覆層を施したこと
を特徴とする連続鋳造用クーリンググリツドであ
る。
なお本発明で用いるNi−Cr系自溶性合金の特
に好ましい組成は次の如くである。即ち、
<Industrial Application Field> The present invention relates to a cooling grid for continuous casting that has excellent wear resistance and corrosion resistance. <Prior Art> In continuous casting equipment, as a method for supporting a slab immediately after passing through a mold, there is a method using a cooling plate or a cooling grid in addition to a roll support method. This has emerged as casting speeds have increased in recent years, and is intended to prevent breakouts and improve cooling efficiency. Among these, the cooling plate has an internal cooling mechanism, so it is made of a material with good thermal conductivity such as copper or copper alloy, and compared to the roll support method or cooling grid method, cooling is the most gradual, and there are no surface defects on the slab. It has the effect of eliminating Also, the cooling grid has a grid-like shape or a shape with many oval-shaped protrusions, and although cooling water is released from several windows opened in it or between the oval-shaped protrusions, it does not have a cooling mechanism inside. Traditionally, the main material used was spheroidal graphite cast iron. That is, the graphite in the spheroidal graphite cast iron was intended to provide hot slip properties and seizure resistance, and it was thought that it would be unavoidable that it would gradually wear out and wear out as it was used. <Problems to be solved by the invention> The above-mentioned cooling plate wears out with use.
To prevent wear and tear due to corrosion, measures have been taken such as grading highly durable metal plates and bolting ceramic plates, and improving the base material of rolls and adding self-fusing alloys to the surface. Countermeasures such as applying a thermal spray coating layer or applying a welded overlay layer are being taken. However, the idea that cooling grids were a kind of consumable item had been established for a long time, and there was no attempt to make them durable. Although the above-mentioned cooling grid made of spherical graphite has excellent seizure resistance, it wears out as it is used, so it must be repositioned each time, and the replacement cycle is usually 300 to 400 channels, which is very long. Moreover, when the number of channels exceeds 300, the part that comes into contact with the slab becomes ferrite due to decarburization, and the hardness decreases to Hv<200 (maximum layer thickness is 15 mm).
Furthermore, there were various problems such as the fact that the material was poor in toughness, making it easy for cracks to occur. It is an object of the present invention to solve the problems of conventional cooling grids and to provide a cooling grid for continuous casting that can be used stably over a long period of time. <Means for Solving the Problems> The means for achieving the above-mentioned object of the present invention are as follows. Namely, the cooling grid body made of general structural steel is provided with at least the portion that comes into contact with the slab. , 12 to 16% by weight of Cr, and 0.5 to 0.7% by weight of C. The cooling grid for continuous casting is characterized by being coated with a sprayed coating layer of a Ni-Cr self-fluxing alloy containing 12 to 16% by weight of Cr and 0.5 to 0.7% by weight of C. A particularly preferred composition of the Ni-Cr self-fluxing alloy used in the present invention is as follows. That is,
【表】
である。これは実際の試験より求めたものであ
り、特にCrとＣの含有量が重要で、Crについて
は、CrはＣとの間で炭化物を形成し、該炭化物
が耐摩耗性向上の要因である硬さを高め、本発明
の様なクーリンググリツドの表面硬さは少なくと
もHv500以上が必要でその為には12重量％以上の
Crが必要である、一方Cr量が16重量％を越える
と得られる溶射層が脆くなりすぎるのでCrの上
限は16重量％とする。またＣが0.5重量％未満で
は耐摩耗性が不足し耐久性に乏しく、又Ｃが0.7
重量％を越えると溶射層が脆くなり剥落の原因と
なるからである。この様な組成に上記表の如く
Ｂ，Siの適量を添加した自溶性合金は、その融点
が約100℃位で、その後の熱処理に適した温度で
ある。
又このNi−Cr系自溶性合金の溶射層の厚みは、
0.2〜0.8mm位が好ましい。0.2mm未満では寿命延長
の効果が少なく、0.8mmを越える程厚くなれば、
該溶射層内に内部応力が蓄積し製造時や使用中に
剥離し易くなるからである。
＜実施例＞
以下本発明の実施例を比較例と共に示す。
この実施例は、SS41製のクーリンググリツド
本体の鋳片との当接部となる面を、シヨツトブラ
ストにて表面粗さが30μｍ程度となる様に粗面加
工し、その上に上表で示した如き組成のNi−Cr
系自溶性合金を溶射層の厚みが0.5mmとなるべく
溶射し、次いで900〜1000℃に加熱処理を施した。
この様にして得られた表面被覆層の硬さは
Hv550〜600であり、従来からの球状黒鉛鋳鉄製
のクーリンググリツドが300〜400chの使用で摩
耗量が大きく、かつクラツクの発生も激しく廃棄
せざるを得なかつたのに対し、本実施例の物は同
条件下での使用で1000〜1200chの使用に耐え、
しかも腐食やクラツク発生のいずれも見られなか
つた。
なお上記実施例と比較する為に、上記実施例と
同様に粗面処理をしたSS41製クーリンググリツ
ド本体に対し、サーメツト溶射及びセラミツク溶
射をした結果、サーメツト（Cr−Al2O3系）溶射
は密着力が５〜10Kg／mm2と小さく熱衝撃に対して
弱く、又セラミツク（Al2O3系）溶射は密着力が
２〜５Kg／mm2で極端に小さく熱衝撃に対しても非
常に弱くて使いものにならなかつた。
又SS41製クーリンググリツド本体に対するメ
ツキによる表面処理実験もしてみた結果、Niメ
ツキではある程度の厚さまでメツキが可能である
が、それ自体の耐摩耗性が不足する為にクーリン
ググリツドとしては不向きで、Ni−ＰやNi−Ｗ
等の高硬度メツキは高々250μｍ位までの厚みに
しかメツキ出来ず膜厚が不十分であつた。
以上の実施列及び比較例を総合的に判断した場
合、本発明のNi−Cr系自溶性合金溶射被覆層が
優れている事を確認した。
なお上記実施例に於ける溶射後の加熱処理につ
いてだが、溶射層同志あるいは溶射層と母材間で
十分な拡散結合をなし、緻密な溶射層を高い密着
力で結合させる為には、少なくとも850℃以上は
必要であり、上限は1200℃位までが望ましい。な
ぜならば1200℃を越えると母材の結晶粒が粗大化
し母材が脆弱化するからである。この様な意味か
ら1200℃以下、好ましくは900〜1200℃の範囲で
十分に緻密で高密着力を有する溶射層が得られる
上記組成のNi−Cr系自溶性合金を選んだのであ
り、自溶性合金やそれ自体としてはCo−Cr系の
方が耐摩耗性や耐食性では優れるが、その熱処理
温度を1200℃以上に高くしなければならない為
に、この場合には不向きである。
＜発明の効果＞
以上述べて来た如く、本発明によれば、クーリ
ンググリツド本体に靭性が大なる一般構造用鋼を
用いた事で強度を向上させる事が出来、しかもそ
の上面には耐食性、耐摩耗性に優れたNi−Cr系
自溶性合金溶射被覆層がある為に高温多湿下でも
耐食性、耐摩耗性に富むと共に該溶射層に含有さ
れる炭化物が高温に於ける潤滑剤としての働きを
なし鋳片の流れをスムーズとなし、総合して長期
に渡り安定して用いる事が出来るものである。
又クーリンググリツド本体に一般構造用鋼を用
いているので、例えば熱伝導性が良い鋼や析出炭
素を持つ球状黒鉛鋳鉄にあつてはまず下地層とし
て金属（合金を含む）層を施してでなければ、
Ni−Cr自溶性合金溶射被覆層を強固に密着出来
ないのと比べ、何の下地層も無く直接このNi−
Cr系自溶性合金溶射被覆層を形成する事が出来
るという利点もある。
従つて本発明によれば、材料及び製作両面で従
来のクーリンググリツドよりも安価であり、かつ
長期に渡つて使用可能という事で操業をしばしば
中断する事もなく操業効率を大きく向上させる事
が可能となる。[Table] This was determined from actual tests, and the content of Cr and C is particularly important. Regarding Cr, Cr forms carbides with C, and these carbides are a factor in improving wear resistance. In order to increase the hardness, the surface hardness of the cooling grid of the present invention must be at least Hv500 or higher, and for that purpose, the cooling grid must have a surface hardness of at least 12% by weight.
Cr is necessary, but if the amount of Cr exceeds 16% by weight, the sprayed layer obtained will become too brittle, so the upper limit of Cr is set at 16% by weight. Furthermore, if C is less than 0.5% by weight, wear resistance is insufficient and durability is poor;
This is because if the amount exceeds % by weight, the sprayed layer becomes brittle and causes peeling. A self-fusing alloy having such a composition and adding appropriate amounts of B and Si as shown in the table above has a melting point of about 100° C., which is a temperature suitable for subsequent heat treatment. Also, the thickness of the sprayed layer of this Ni-Cr self-fluxing alloy is:
It is preferably about 0.2 to 0.8 mm. If it is less than 0.2mm, the effect of extending the lifespan will be small, and if it becomes thicker than 0.8mm,
This is because internal stress accumulates within the sprayed layer, making it easy to peel off during manufacturing or use. <Examples> Examples of the present invention will be shown below together with comparative examples. In this example, the surface of the cooling grid body made of SS41 that will come into contact with the slab is roughened by shot blasting to a surface roughness of approximately 30 μm, and then Ni-Cr with the composition shown in
The self-fluxing alloy was sprayed to a sprayed layer thickness of 0.5 mm, and then heat treated at 900 to 1000°C. The hardness of the surface coating layer obtained in this way is
Hv550 to 600, and conventional cooling grids made of spheroidal graphite cast iron suffer from large amounts of wear and cracks when used for 300 to 400 channels, and have to be discarded due to the occurrence of cracks. The product can withstand 1000 to 1200 channels under the same conditions.
Moreover, neither corrosion nor cracking was observed. For comparison with the above example, cermet spraying and ceramic spraying were performed on the SS41 cooling grid body, which had been roughened in the same manner as in the above example. has a small adhesion force of 5 to 10 kg/mm 2 and is weak against thermal shock, and ceramic (Al 2 O 3 based) thermal spraying has an extremely small adhesion force of 2 to 5 kg/mm 2 and is extremely resistant to thermal shock. It was weak and useless. We also conducted a surface treatment experiment by plating the main body of a cooling grid made of SS41, and found that Ni plating can be plated up to a certain thickness, but it is not suitable for use as a cooling grid due to its own lack of wear resistance. , Ni-P and Ni-W
High-hardness platings such as the above could only be plated to a thickness of about 250 μm at most, and the film thickness was insufficient. When the above examples and comparative examples were comprehensively judged, it was confirmed that the Ni-Cr self-fluxing alloy thermal spray coating layer of the present invention is excellent. Regarding the heat treatment after thermal spraying in the above example, in order to achieve sufficient diffusion bonding between the thermally sprayed layers or between the thermally sprayed layers and the base material, and to bond the dense thermally sprayed layers with high adhesion, a heat treatment of at least 850 ℃ or higher is necessary, and the upper limit is preferably around 1200℃. This is because when the temperature exceeds 1200°C, the crystal grains of the base material become coarse and the base material becomes brittle. In this sense, we selected a Ni-Cr based self-fluxing alloy with the above composition, which can provide a thermally sprayed layer with sufficient density and high adhesion at temperatures below 1200°C, preferably in the range of 900 to 1200°C. Although the Co-Cr system itself has better wear resistance and corrosion resistance, it is not suitable in this case because the heat treatment temperature must be raised to 1200°C or higher. <Effects of the Invention> As described above, according to the present invention, the strength can be improved by using general structural steel with high toughness for the main body of the cooling grid, and the upper surface has corrosion resistance, Because it has a Ni-Cr self-fluxing alloy thermal spray coating layer with excellent wear resistance, it has excellent corrosion and abrasion resistance even under high temperature and high humidity conditions, and the carbide contained in the thermal spray layer acts as a lubricant at high temperatures. This allows the slab to flow smoothly and can be used stably for a long period of time. In addition, since general structural steel is used for the cooling grid body, for example, in the case of steel with good thermal conductivity or spheroidal graphite cast iron with precipitated carbon, a metal (including alloy) layer is first applied as a base layer. If not,
Compared to the Ni-Cr self-fusing alloy thermal spray coating layer, which cannot be firmly adhered, this Ni-Cr self-fluxing alloy can be directly attached without any base layer
Another advantage is that a Cr-based self-fluxing alloy thermal spray coating layer can be formed. Therefore, according to the present invention, the cooling grid is cheaper than conventional cooling grids in terms of both materials and manufacturing, and can be used for a long period of time, so operation efficiency can be greatly improved without frequent interruptions in operation. It becomes possible.