JPH0356618A - Production of free cutting steel - Google Patents
Production of free cutting steelInfo
- Publication number
- JPH0356618A JPH0356618A JP18886389A JP18886389A JPH0356618A JP H0356618 A JPH0356618 A JP H0356618A JP 18886389 A JP18886389 A JP 18886389A JP 18886389 A JP18886389 A JP 18886389A JP H0356618 A JPH0356618 A JP H0356618A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- hot
- free
- cutting steel
- cutting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229910000915 Free machining steel Inorganic materials 0.000 title claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 62
- 239000010959 steel Substances 0.000 claims abstract description 61
- 238000001816 cooling Methods 0.000 claims abstract description 26
- 238000010438 heat treatment Methods 0.000 claims abstract description 26
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 19
- 229910052711 selenium Inorganic materials 0.000 claims abstract description 16
- 238000005096 rolling process Methods 0.000 claims abstract description 12
- 239000002344 surface layer Substances 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims description 7
- 238000005520 cutting process Methods 0.000 claims description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims description 5
- 229910000746 Structural steel Inorganic materials 0.000 claims description 3
- 229910052791 calcium Inorganic materials 0.000 claims description 3
- 229910001105 martensitic stainless steel Inorganic materials 0.000 claims description 3
- 238000001556 precipitation Methods 0.000 abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 7
- 238000007670 refining Methods 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 12
- 238000005098 hot rolling Methods 0.000 description 9
- 238000005336 cracking Methods 0.000 description 4
- 230000007547 defect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 229910052745 lead Inorganic materials 0.000 description 3
- 229910052748 manganese Inorganic materials 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000005266 casting Methods 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 238000005303 weighing Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013467 fragmentation Methods 0.000 description 1
- 238000006062 fragmentation reaction Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000010587 phase diagram Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000009875 water degumming Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
（産業上の利用分野）
本発明は、被削性向上元素としてＳおよびＳｅのうちか
ら遺ばれる少な〈とも１種を必須で含有する快削鋼にお
いて、その熱間圧延時におけるコーナー割れの発生を防
止するのに利用される快削鋼の製造方法に関するもので
ある．
（従来の技術）
従来，被削性向上元素としてＳおよびＳｅのうちから選
ばれる少なくとも１種を必須で含有し、Ｐｂ，Ｔｅ，Ｂ
ｉ，Ｐ，Ｃａなどｃ））Ｓ，Ｓｅ以外の被削性向上元素
の１種以上を任意で含有している快削鋼、例えばＳＵＳ
４１６系の快削マルテンサイト系ステンレス鋼を製造す
るにあたっては、鋳型より取り出した前記快削鋼の熱塊
を１３００〜１３４０℃程度に加熱したのち、熱間圧延
（分塊圧延）を行うようにしていた．
（発明が解決しようとする！［）
しかしながら、このような従来の快削鋼の製造方法にあ
っては，熱間圧延時にコーナー割れを発生しやすいもの
となっていた．
そのため，コーナー割れの発生した部分を除去する必要
があることから，鋼片の減摩量が大幅に増加するのは避
けられないという課題があった．
（発明の目的）
本発明は，上述した従来の課題にかんがみてなされたも
ので、例えばＰＪ型より取り出したＳおよびＳｅのうち
から選ばれる少なくとも１種を含有する快削鋼からなる
熱塊（インゴット造塊による場合）または熱片（連続鋳
造による場合）を加熱し次いで圧延（例えば，分塊圧延
）することにより鋼片を得る工程において、前記鋼片に
コーナー割れが発生するのをできるだけ防止することが
可能であって、鋼片の減摩量を低減することが可能であ
り、鋼片の表聞手入れ作業をより一層効率良〈行うこと
ができるようになる快削鋼の製造方法を提供することを
ｎ的としている．(Industrial Application Field) The present invention is directed to the occurrence of corner cracks during hot rolling in free-cutting steel that essentially contains at least one of S and Se as machinability-improving elements. This relates to a manufacturing method for free-cutting steel used to prevent (Prior art) Conventionally, at least one element selected from S and Se is essential as a machinability improving element, and Pb, Te, B
i, P, Ca, etc.c)) Free-cutting steel that optionally contains one or more machinability-improving elements other than S and Se, such as SUS
In manufacturing 416 series free-cutting martensitic stainless steel, the hot lump of free-cutting steel taken out from the mold is heated to about 1300 to 1340°C, and then hot rolled (blushing rolling) is performed. It was. (This is what the invention attempts to solve!) However, with this conventional manufacturing method for free-cutting steel, corner cracks tend to occur during hot rolling. Therefore, since it was necessary to remove the areas where corner cracks had occurred, there was an unavoidable problem that the amount of friction reduction of the steel billet would increase significantly. (Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems. In the process of obtaining a steel billet by heating and then rolling (e.g., blooming) a hot billet (in the case of ingot ingot making) or a hot billet (in the case of continuous casting), prevent corner cracks from occurring in the billet as much as possible. A method for manufacturing free-cutting steel that can reduce the amount of friction of the steel billet and enables surface care work of the steel billet to be carried out even more efficiently. The aim is to provide the following information.
（課題を解決するための手段）
本発明は、造塊鋳型または連続鋳造鋳型などの＃ｆｔ５
等より取り出したＳおよびＳｅのうちから選ばれる少な
〈とも１種を含有する快削鋼からなる熟塊（前者のイン
ゴッ１・造塊による鋼塊の場合）または熱片（後者の連
続＃４造による鋳片の場合）を加熱し次いで圧延して鋼
片とする工程において，加熱前に前記熱塊または熱片を
冷却して少なくとも表Ｍ部分のｌｌｉ織を微細化したの
ち，前−記熱塊または熱片を加熱し次いで圧延して鋼片
とする構戊としたことを特徴としており、このような快
削鋼の製造方法の構成を前述した従来の課題を解決する
ための手段としている．
本発明に係わる快削鋼の製造方法は．被削性向上元素と
してＳおよびＳｅのうちから選ばれる少なくとも１種を
必須で含有し、Ｐｂ，Ｔｅ，Ｂｉ，Ｐ，ＣａなどのＳ，
Ｓｅ以外の被削性向上元素の１種以上を任意で含有して
いる快削鋼に適用される．
このような快削鋼としては、熱間圧延温度約１３００℃
において状態図的にα＋γの状態となっているものに適
用することがとくに望ましく、例えば、Ｃ含有量が０．
０８〜０．４０重量％、Ｃｒ含有量が１０〜１８重量％
の快削マルテンサイト系ステンレス鋼よりなるものが適
用され、より具体的には、重量％で、例えば，Ｃ：０．
０８〜０．１５％、Ｓｉ：１．００％以下、Ｍｎ：１．
２５％以下、Ｐ：０．０６０％以下，Ｓ：０．１０−０
．３５％、 Ｃｕ：０．５０％以下、Ｎｉ：０．５０％
以下、Ｃｒ：ｌ２．０〜１４．０％、Ｍ ｏ ： ０
． ６ ０％以下、Ｎ：０．０３０％以下、必要に応じ
てＰｂ：０．１０〜０．３０％、同じく必要に応じてＳ
ｅ：０．１０−０．２０％、同じく必要に応じテＴｅ：
０．０２〜０．０６％、同じく必要に応じてＢ：０．０
０４ 〜０．００７％、残部実質的にＦｅよりなるＳＵ
３４１６系のものや、Ｃ：０．２８〜０．３５％．Ｓｉ
：０．１０−１．００％、Ｍ ｎ ： ０ ． ８ ０
Ｎ１ ． ２ ５％．Ｐ：０．０４０％以下、Ｓ：０
．０８ 〜０．３０％、Ｃｕ：０．５０％以下、Ｎｉ：
０．６０％以下、Ｃｒ：１２．０〜１４．０％、Ｍｏ：
０．６０％以下，Ｎ：０．０４％以下，残部実賀的にＦ
ｅよりなるＳＵＳ４２０系のものなどがあり，また構造
用鋼としては、Ｃ含有量が０．０８〜Ｏ、５５重量％の
快削ＪＪｂａ用鋼よりなるものが適用され、より共体的
には，例えば、Ｃ ： ０ ． １ ｊ％以下、Ｓｉ：
０．３０％以下、Ｍｎ：０．７５ 〜１．３５％、 Ｐ
：０．０４０〜０．０９０％、 Ｓ：０．１０−０．３
５％、必要に応じてＰｂ：
０．０４〜０．３０％、同じく必要に応じてＳｅ：０．
１０−０．２０％、同じく必要に応じてＴｅ：０．１０
〜０．２０％，同じく必要に応じてＣａ ： ０ ．
０００５ 〜０ ．００５％，歿部実賀的にＦｅよりな
る快削構造用鋼などがあるが、当然のことながらここに
例示したもののみに限定はされないことはいうまでもな
い．
そして、本発明に係わる快削鋼の製造方法では、上述し
たごとく例示した快削鋼からなる熱塊または熟片を加熱
し、次いで圧延して鋼片とする工程において、加熱前に
前記熱塊または熱片を冷却して少なくとも表層部分にお
ける組織形態をコントロールして組織を微細化したのち
、前記熱塊または熟片を加熱し次いで圧延して鋼片とし
、熱間圧延の際に前記鋼片にコーナー割れが生じないよ
うにしているが、この場合の熱塊または熱片に対する冷
却手段としては水冷を採用することが簡便であって経済
的にも好ましく、水スプレーやミストによる玲却を採用
することも可能である．また、水玲にあたっては、少な
くとも熱塊または熱片の表層部がα＋γ十Ｋ＋ （カ
ーバイド）の状態からα＋Ｋ１変態点を通過する温度ま
で冷却されるようにすることが望まし〈、例えば少なく
とも表面部分が５００℃以下の温度となるような急冷を
施すことが望ましい．ただし、冷却の温度があまりにも
低すぎたり、また鋼片のコーナー割れを防止するのに有
効である以上の深さまで冷却を行ったりすると、その後
の加熱量や加熱時間が多〈なって熟経済的でなくなるこ
ともないとはいえないことから、熱間圧延時に鋼片にコ
ーナー割れが生じない程度の冷却例えば表面部分が３０
０〜５００℃の温度となる冷却を施すようになすことも
必要に応じて望ましい．そして、このような加熱前の冷
却を施すことによって少なくとも表層部分の組織的形態
がコントロールされて微細な組織となり、δ一Ｆｅの平
均径および面積率も太き〈なり、さらにはδ一Ｆｅの形
恩も変化しているものとなるので、冷却後の加熱および
熱間圧延によって得られた鋼片にはコーナー割れが発生
しがたいものとすることができる．
この場合、上記したように、加熱前の冷却を施すことに
よって少なくとも表層部分の組織的形態がコントロール
されることにより、δ一Ｆｅのｆ均経および面積率が増
加して粒界へのＳ．Ｓｅの低減が実現されて熱間加工性
の向上に寄与するが、この場合の表層部分（表面から２
〜３ｍｍ程度の部分）におけるδ一Ｆｅの平均粒径は６
〜ｌｏｇｍ．δ一Ｆｅの面積率は５〜１０％程度となる
ようにすることがとくに望ましい．
（発明の作用）
本発明に係わる快削鋼の製造方法では、例えば鋳型より
取り出したＳおよびＳｅのうちから選ばれる少なくとも
１種を含有する快削鋼からなる熱塊または熱片を加熱し
次いで圧延して鋼片とする工程において、加熱前に前記
熱塊または熟片を冷却して少なくとも表層部分の組織を
微細化したのち，前記熱塊または熱片を加熱し次いで圧
延して鋼片とするようにしているので、加熱前に実施さ
れる冷却によって熱塊または熱片の少なくとも表層部分
における組織的形態がコントロールされたものとなり、
加熱前に冷却しない熱塊のままとする場合に比べいった
ん冷却して熱塊水冷とした場合には表層部分におけるδ
−Ｆｅの平均径が大きなものとなりかつまたその面積率
が増加したものとなることによって粒界へのＳ，Ｓｅの
析出を低減することができると共に、δ−Ｆｅの形態も
変化し、加熱前に冷却しない熱塊のままとする場合には
柱状品の残存とみられる粗い組織を有していてδ−Ｆｅ
が網状に広がっているのに対して，加熱前に冷却して熱
塊水冷とした場合にはδ一Ｆｅの形態が変化していて加
熱前に冷却しない場合の，窮状形態のδ一Ｆｅが冷却に
より分断されて丸味を帯びたものとなることにより割れ
感受性が低下したものとなり、さらには冷却によって少
な〈とも表屑部分の組織が微細化されて粒界へのＳ．Ｓ
ｅの析出量および析出密度の低減がもたらされるように
なることから、熱間加工性が著し〈向上したものとなり
、それゆえ熱間圧延時において鋼片にコーナー割れが生
じがたいようになるという作用がもたらされる．
（実施例）
第１表に示す化学或分の鋼を溶製しそして鋳造すること
によって重ｉ４０ｋｇ，大きさ１２０ｍｍ角のテストイ
ンゴットよりなる熱塊を得たのち、前記熱塊に対し水冷
を１５秒間行うことによって表面部分を第１図の実施例
に示す温度変化パターンで急冷し、表面部分の温度が４
００℃となるように冷却した．
続いて、このようにして熱塊水冷した鋼塊を１３００℃
に加熱して９０分間保持したのち同じく第１図の実施例
に示す温度変化パターンで急冷し，そのミクロ組織を観
察した．
ここで観察したミクロ組織およびδ−Ｆｅ形態を第２図
の実施例（熱塊水冷）の欄に示す．比較のために，前記
実施例と同じく第１表に示す化学成分の鋼を溶製しそし
て鋳造して重量４０ｋｇ，大きさ１２０ｍｍ角のテスト
インゴットよりなる熱塊を得たのち、この熱塊を水冷す
ることな〈第１図の比較例に示した温度変化パターンで
１３００℃に加熱して９０分間保持したのち急冷し，そ
のミクロ組織を観察した．
ここで観察したミクロ組織およびδ一Ｆｅ形恩を第２図
の比較例（熱塊）の欄に示す．次に、前述した重ｉ４０
ｋｇ．大きさ１２０ｍｍ角のパイロットインゴー２トを
第３図の実施例に示す温度変化パターンとなるように、
表而温度が４００℃となる冷却を行い，次いで１３００
℃に加熱した．そして．１３００℃に加熱したインゴッ
トを圧延して鋼片とした．
ここで得られた鋼片の疵取りによる減耗量を調べたとこ
ろ第２表の実施例の欄に示す結果であった．
また、比較のために，前述した重量４０ｋｇ．大きさ１
２０ｍｍ角のパイロットインゴットを第３図の比較例に
示す温度変化パターンとなるように冷却することな＜１
３００℃に加熱した．そして、１３００℃に加熱したイ
ンゴットを圧延して鋼片とした．
ここで得られた鋼片の疵取りによる減耗量を調べたとこ
ろ第２表の比較例の欄に示す結果であった．
次に、第１表に示したと同じ化学成分をもつ実川鋼塊（
重是１．５ｔｏｎ）を用いて、第３図の実施例に示した
温度変化パターンに従って８４０℃から急冷して表面温
度が４００゜Ｃとなったのち加熱して１３００℃とし、
この後正延して鋼片とすることにより，鋼片の疵発生状
況および鋼片の疵取りによる減耗率を調べた．この結果
，鋼片の疵発生状況は第４図の実施例の項に示すとおり
であり、鋼片の疵取りによる減耗率は第３表の実施例の
欄に示すとおりであった．
また，比較のために、第１表に示したと同じ化学或分を
もつ実用鋼塊（重量１．５ｔｏｎ）を川いて、第３図の
比較例に示した温度変化パターンに従って８ ４ ０
’Ｃから加熱して１３００℃とし、この後圧延して鋼片
とすることにより、鋼片の疵発生状況および鋼片の疵取
りによる減粍率を調べた．この結果、鋼片の疵発生状況
は第４図の比較例の項に示すとおりであり、鋼片の疵取
りによる減耗率は第３表の比較例の欄に示すとおりであ
った．
さらに、参考のために、第１表に示したと同じ化学成分
をもつ実用鋼塊（重量１．５ｔｏｎ）を用いて、第３図
の参考例に示した温度変化ノくターンに従っていったん
冷塊としたのち加熱して１ ３ ０ ０ ’Ｃとし、こ
の後圧延して鋼片とすることにより、鋼片の疵発生状況
および鋼片の疵取りによる減耗率を調べた．この結果、
鋼片の疵発生状況は第４図の参考例の項に示すとおりで
あり、鋼片の疵取りによる減耗率は第３表の参考例の欄
に示すとおりであった．
第２表および第３表に示した結果より明らかなように、
実用鋼塊を用いた試験結果はテストインゴットを用いた
試験結果と同様の傾向を示しており，加熱前に水冷を行
った熱塊水冷の場合には、加熱前に冷却を行わなかった
熱塊の場合に比べて，鋼片の減摩量をかなり少なくでき
ることが認められた．また、第４図に示すように、実用
鋼塊では鋼片のコーナー割れが著しく改善されることも
認められた．
さらに、加熱前に水冷を行った熱塊水冷の場合には，第
２図に示すように，ミクロ組織が微細なものとなってお
り、δ一Ｆｅ形態においても平均径が大きく面積率も大
きなものとなっているので，δ−Ｆｅの増加による粒界
へのＳ，Ｓｅの析出低減、δ−Ｆｅの形態変化（網状形
態の分断）による割れ感受性の低下、組織の微細化によ
る粒界へのＳ，Ｓｅ析出量および析出密度の低減による
熱間加工性の向上がもたらされ、加熱後の熱間圧延にお
いて鋼片にコーナー割れが発生しがたいものとなってい
ることが推察された．
これに対して、加熱前に冷却を行わない比較例の熱塊の
場合には，第２図の比較例の欄に示すように、δ一Ｆｅ
の平均径が小さなものとなっており、またδ一Ｆｅの面
積率も少ないものとなっており、さらにδ一Ｆｅの形態
においては網状に広がったものとなっており，表層組織
は柱状晶の残存とみられる粗い組織となっていて、熱間
加工性があまり良くないことから熱間圧延時において鋼
片にコーナー割れが発生しやすいものとなっていること
が推察された．(Means for Solving the Problems) The present invention provides #ft5 casting molds such as ingot molds or continuous casting molds.
Ripe ingots made of free-cutting steel containing at least one type of S and Se extracted from etc. (in the case of ingots 1 and ingots of the former) or hot pieces (continuous #4 of the latter) In the process of heating and then rolling a slab (in the case of a cast slab by molding) and then rolling it into a steel slab, the hot lump or hot slab is cooled before heating to refine the LLI weave in at least the surface M portion, and then It is characterized by a structure in which a hot lump or piece is heated and then rolled into a steel piece, and the structure of the method for manufacturing such free-cutting steel has been developed as a means to solve the conventional problems described above. There is. The method for producing free-cutting steel according to the present invention is as follows. Essentially contains at least one selected from S and Se as a machinability improving element, and S, such as Pb, Te, Bi, P, and Ca.
Applicable to free-cutting steels that optionally contain one or more machinability-improving elements other than Se. For such free-cutting steel, the hot rolling temperature is approximately 1300°C.
It is particularly desirable to apply this to those in which the phase diagram is α+γ, for example, when the C content is 0.
08-0.40% by weight, Cr content 10-18% by weight
A free-cutting martensitic stainless steel with C:0.
08 to 0.15%, Si: 1.00% or less, Mn: 1.
25% or less, P: 0.060% or less, S: 0.10-0
．． 35%, Cu: 0.50% or less, Ni: 0.50%
Below, Cr: l2.0-14.0%, Mo: 0
．． 6 0% or less, N: 0.030% or less, Pb: 0.10 to 0.30% as necessary, S as necessary
e: 0.10-0.20%, also as necessary Te:
0.02-0.06%, also as necessary B: 0.0
04 - 0.007% SU, the remainder consisting essentially of Fe
3416 series, C: 0.28-0.35%. Si
:0.10-1.00%, Mn: 0. 8 0
N1. 2 5%. P: 0.040% or less, S: 0
．． 08 ~0.30%, Cu: 0.50% or less, Ni:
0.60% or less, Cr: 12.0-14.0%, Mo:
0.60% or less, N: 0.04% or less, the remainder is F
There are SUS420 series made of E, and as structural steel, free-cutting JJba steel with a C content of 0.08 to O and 55% by weight is used. , for example, C: 0. 1 j% or less, Si:
0.30% or less, Mn: 0.75 to 1.35%, P
:0.040-0.090%, S:0.10-0.3
5%, if necessary Pb: 0.04-0.30%, also if necessary Se: 0.
10-0.20%, also if necessary Te: 0.10
~0.20%, also as necessary Ca: 0.
0005 ~0. 0.005%, free-cutting structural steel made of Fe, etc., but it goes without saying that the steel is not limited to those exemplified here. In the method for producing free-cutting steel according to the present invention, in the step of heating a hot ingot or a ripe piece made of the free-cutting steel exemplified above and then rolling it into a steel billet, the hot ingot is heated before heating. Alternatively, after cooling the hot piece and refining the structure by controlling the structure morphology at least in the surface layer, the hot lump or ripe piece is heated and then rolled to form a steel piece, and the steel piece is heated during hot rolling. In this case, it is simple and economically preferable to use water cooling as a means of cooling the hot lumps or pieces, and cooling using water spray or mist is used. It is also possible to do so. In addition, for water refining, it is desirable that at least the surface layer of the hot lump or hot piece is cooled from the α+γ10K+ (carbide) state to a temperature that passes through the α+K1 transformation point. It is desirable to perform rapid cooling to a temperature of 500°C or less. However, if the cooling temperature is too low or if the cooling is performed to a depth that exceeds what is effective in preventing corner cracking of the billet, the amount and time of subsequent heating will be large, resulting in poor economic performance. Therefore, it is necessary to cool the steel piece to an extent that does not cause corner cracks during hot rolling, for example, if the surface part
It is also desirable, if necessary, to provide cooling to a temperature of 0 to 500°C. By performing such cooling before heating, the structural morphology of at least the surface layer is controlled to become a fine structure, the average diameter and area ratio of δ-Fe become thicker, and furthermore, the average diameter and area ratio of δ-Fe become thicker. Since the shape is also changed, corner cracks are less likely to occur in the steel slab obtained by heating and hot rolling after cooling. In this case, as described above, by cooling before heating, the structural morphology of at least the surface layer is controlled, and the f-average and area ratio of δ-Fe increase, resulting in S. This reduces Se and contributes to improving hot workability, but in this case, the surface layer (2
The average grain size of δ-Fe in the ~3mm portion) is 6
~logm. It is particularly desirable that the area ratio of δ-Fe be approximately 5 to 10%. (Function of the invention) In the method for manufacturing free-cutting steel according to the present invention, for example, a hot lump or hot piece made of free-cutting steel containing at least one selected from S and Se is heated, and then In the step of rolling into a steel billet, the hot lump or ripe piece is cooled before heating to refine the structure at least in the surface layer, and then the hot lump or hot piece is heated and then rolled to become a steel billet. Therefore, the cooling performed before heating controls the structural morphology of at least the surface layer of the hot mass or hot flakes,
Compared to the case where the hot lump is not cooled before heating, when the hot lump is cooled and water-cooled, the δ in the surface layer is
-By increasing the average diameter of Fe and increasing its area ratio, it is possible to reduce the precipitation of S and Se at grain boundaries, and the morphology of δ-Fe also changes, causing If it is left as a hot lump without being cooled, it has a coarse structure that is considered to be a residual columnar product.
On the other hand, when the δ-Fe is cooled before heating and the hot mass is water-cooled, the form of δ-Fe changes, and when the δ-Fe is not cooled before heating, the δ-Fe is Cooling results in fragmentation and roundness, which reduces cracking susceptibility.Furthermore, cooling also refines the structure of at least the surface debris, causing S.I. S
Since the precipitation amount and precipitation density of e are reduced, the hot workability is significantly improved, and therefore corner cracks are less likely to occur in the steel billet during hot rolling. Effect is brought about. (Example) After obtaining a hot lump consisting of a test ingot with a weight of 40 kg and a size of 120 mm square by melting and casting a certain amount of steel shown in Table 1, the hot lump was water-cooled for 15 minutes. The surface portion is rapidly cooled in the temperature change pattern shown in the example of FIG.
It was cooled to 00℃. Next, the hot water-cooled steel ingot was heated to 1300°C.
After heating and holding for 90 minutes, the sample was rapidly cooled using the temperature change pattern shown in the example shown in Figure 1, and its microstructure was observed. The microstructure and δ-Fe morphology observed here are shown in the Example (hot mass water cooling) column of Figure 2. For comparison, steel having the chemical composition shown in Table 1 as in the previous example was melted and cast to obtain a hot lump consisting of a test ingot weighing 40 kg and measuring 120 mm square. Without water cooling (the temperature change pattern shown in the comparative example in Figure 1), the sample was heated to 1300°C, held for 90 minutes, and then rapidly cooled, and its microstructure was observed. The microstructure and δ-Fe shape observed here are shown in the comparative example (thermal mass) column of Figure 2. Next, the above-mentioned heavy i40
kg. Two pilot ingots with a size of 120 mm square were heated so as to have the temperature change pattern shown in the example in Fig. 3.
Cooling is carried out to a surface temperature of 400°C, then 1300°C.
It was heated to ℃. and. An ingot heated to 1300°C was rolled into a steel billet. When the amount of wear of the obtained steel slab due to flaw removal was investigated, the results were shown in the Example column of Table 2. Also, for comparison, the weight 40 kg mentioned above. size 1
A 20 mm square pilot ingot was cooled to the temperature change pattern shown in the comparative example in Figure 3.
It was heated to 300℃. The ingot heated to 1300°C was then rolled into a steel billet. When the amount of wear of the steel slab obtained here due to flaw removal was investigated, the results were shown in the Comparative Example column of Table 2. Next, the Jitsukawa Steel Ingot (
(weight: 1.5 ton) was rapidly cooled from 840°C according to the temperature change pattern shown in the example in Figure 3 until the surface temperature reached 400°C, and then heated to 1300°C.
After this, the steel slabs were flat-rolled to form steel slabs, and the occurrence of defects in the steel slabs and the rate of wear caused by removing the scratches from the steel slabs were investigated. As a result, the occurrence of flaws on the steel slabs was as shown in the Examples section of Figure 4, and the rate of wear of the steel slabs due to flaw removal was as shown in the Examples section of Table 3. For comparison, a practical steel ingot (weighing 1.5 tons) having the same chemical composition as shown in Table 1 was washed down a river, and the temperature change pattern shown in the comparative example in Fig. 3 was 840.
The steel pieces were heated to 1300°C and then rolled into steel pieces to investigate the occurrence of defects in the steel pieces and the rate of reduction in defects due to the removal of defects from the steel pieces. As a result, the occurrence of flaws on the steel slabs was as shown in the Comparative Example section of Figure 4, and the rate of wear of the steel slabs due to flaw removal was as shown in the Comparative Example column of Table 3. Furthermore, for reference, a practical steel ingot (weight 1.5 tons) having the same chemical composition as shown in Table 1 is used, and once cooled into a cold ingot according to the temperature change diagram shown in the reference example in Figure 3. After that, it was heated to 1300'C and then rolled into steel slabs to examine the occurrence of flaws in the steel slabs and the rate of wear caused by removing the flaws from the steel slabs. As a result,
The occurrence of flaws on the steel slabs is as shown in the reference example section of Figure 4, and the wear rate due to flaw removal on the steel slabs is as shown in the reference example column of Table 3. As is clear from the results shown in Tables 2 and 3,
The test results using practical steel ingots show the same tendency as the test results using test ingots. It was confirmed that the amount of friction loss on the steel billet could be significantly reduced compared to the case of . In addition, as shown in Figure 4, it was also observed that corner cracking of the steel slab was significantly improved in the commercial steel ingot. Furthermore, in the case of hot mass water cooling, in which water cooling is performed before heating, the microstructure is fine, as shown in Figure 2, and even in the δ-Fe form, the average diameter is large and the area ratio is large. As a result, the precipitation of S and Se at grain boundaries is reduced due to an increase in δ-Fe, the cracking susceptibility is reduced due to a change in the morphology of δ-Fe (disintegration of the network morphology), and the precipitation of S and Se at grain boundaries is reduced due to a refinement of the structure. It was inferred that hot workability was improved by reducing the amount of S and Se precipitation and the precipitation density, making it difficult for corner cracks to occur in the steel billet during hot rolling after heating. ．． On the other hand, in the case of the hot mass of the comparative example that is not cooled before heating, as shown in the comparative example column of Fig. 2, δ - Fe
The average diameter of δ-Fe is small, the area ratio of δ-Fe is also small, and the form of δ-Fe is spread out like a network, and the surface structure is composed of columnar crystals. It was assumed that the steel slab had a rough structure that appeared to be residual, and its hot workability was not very good, making it likely that corner cracks would occur in the steel slab during hot rolling.
この発明では，ＳおよびＳｅのうちから選ばれる少なく
とも１種を含有する快削鋼からなる熱塊または熱片を加
熱し次いで圧延して鋼片とする工程において、加熱前に
前記熱塊または熱片を冷却して少なくとも表層部分の組
織を微細化したのち，前記熱塊または熱片を加熱し次い
で圧延して鋼片とする構成としたから，圧延により得ら
れた鋼片にコーナー割れが発生するのをできるだけ防止
することが可能であり、鋼片の減摩量を著しく低下させ
ることができるようになって鋼材歩留りの向上をはかる
ことが可能であると共に、鋼片の表而手入れ作業を効率
よく短時間のうちに終らすことが可能になるという著大
なる効果がもたらされる．In this invention, in the step of heating a hot lump or hot piece made of free-cutting steel containing at least one selected from S and Se and then rolling it into a steel piece, the hot lump or hot piece is heated before heating. Since the hot lump or hot piece is heated and then rolled into a steel piece after cooling the piece to refine the structure at least in the surface layer, corner cracks occur in the steel piece obtained by rolling. It is possible to prevent this as much as possible, and it is possible to significantly reduce the amount of friction loss of the steel billet, thereby improving the steel material yield, and it is possible to improve the surface care work of the steel billet. This has the great effect of making it possible to complete the process efficiently and in a short period of time.
第１図は本発明の実施例および比較例に対応するテスト
インゴットの温度変化パターンを示す説明図、第２図は
本発明の実施例および比較例に対応するテストインゴッ
トのミクロ組織（５０倍）およびδ−Ｆｅ形態（４００
倍）を示す金属組織顕ＷＬ鏡写真、第３図は本発明の実
施例．比較例および参考例における鋼塊の温度変化パタ
ーンを示す説明図、第４図は鋼片の疵発生状況を調べた
結果を示す説１１図である．
特詐出舶人 大同特殊鋼株式会社Figure 1 is an explanatory diagram showing the temperature change pattern of test ingots corresponding to the examples and comparative examples of the present invention, and Figure 2 is the microstructure (50x magnification) of the test ingots corresponding to the examples and comparative examples of the present invention. and δ-Fe form (400
Fig. 3 is a metallographic microscopic WL micrograph showing an example of the present invention. Fig. 4 is an explanatory diagram showing the temperature change pattern of the steel ingots in comparative and reference examples, and Fig. 11 is an explanatory diagram showing the results of investigating the occurrence of flaws in the steel slabs. Special fraud shipper Daido Special Steel Co., Ltd.
Claims (1)
を含有する快削鋼からなる熱塊または熱片を加熱し次い
で圧延して鋼片とする工程において、加熱前に前記熱塊
または熱片を冷却して少なくとも表層部分の組織を微細
化したのち、前記熱塊または熱片を加熱し次いで圧延し
て鋼片とすることを特徴とする快削鋼の製造方法。 （２）快削鋼は、被削性向上元素としてＳおよびＳｅの
うちから選ばれる少なくとも１種を必須で含有し、Ｐｂ
、Ｔｅ、Ｂｉ、Ｐ、ＣａなどのＳ、Ｓｅ以外の被削性向
上元素の１種以上を任意で含有しているものである請求
項第（１）項に記載の快削鋼の製造方法。 （３）快削鋼は、Ｃ含有量が０．０８〜 ０．４０重量％、Ｃｒ含有量が１０〜１８重量％の快削
マルテンサイト系ステンレス鋼である請求項第（１）項
または第（２）項に記載の快削鋼の製造方法。 （４）快削鋼は、Ｃ含有量が０．０８〜 ０．５５重量％の快削構造用鋼である請求項第（１）項
または第（２）項に記載の快削鋼の製造方法。 （５）加熱前に冷却される熱塊または熱片は、冷却によ
り少なくともその表面が５００℃以下の温度に冷却され
たのち、加熱され次いで圧延される請求項第（１）項、
第（２）項、第（３）項または第（４）項のいずれかに
記載の快削鋼の製造方法。[Claims] (1) In the step of heating a hot ingot or hot piece made of free-cutting steel containing at least one selected from S and Se and then rolling it into a steel piece, before heating, A method for producing free-cutting steel, which comprises cooling the hot lump or hot piece to refine the structure of at least a surface layer portion, and then heating the hot lump or hot piece and then rolling it into a steel piece. (2) Free-cutting steel essentially contains at least one element selected from S and Se as machinability-improving elements, and Pb
The method for producing free-cutting steel according to claim (1), which optionally contains one or more machinability improving elements other than S and Se, such as Te, Bi, P, and Ca. . (3) The free-cutting steel is free-cutting martensitic stainless steel with a C content of 0.08 to 0.40% by weight and a Cr content of 10 to 18% by weight. The method for producing free-cutting steel according to item (2). (4) Manufacture of free-cutting steel according to claim (1) or (2), wherein the free-cutting steel is a free-cutting structural steel with a C content of 0.08 to 0.55% by weight. Method. (5) The hot lump or hot piece that is cooled before heating is cooled to a temperature of at least 500°C or less on its surface by cooling, and then heated and then rolled.
The method for producing free-cutting steel according to any one of paragraphs (2), (3), or (4).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18886389A JPH0356618A (en) | 1989-07-24 | 1989-07-24 | Production of free cutting steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18886389A JPH0356618A (en) | 1989-07-24 | 1989-07-24 | Production of free cutting steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0356618A true JPH0356618A (en) | 1991-03-12 |
Family
ID=16231184
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18886389A Pending JPH0356618A (en) | 1989-07-24 | 1989-07-24 | Production of free cutting steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0356618A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100920621B1 (en) * | 2002-12-24 | 2009-10-08 | 주식회사 포스코 | Method for Manufacturing Billet of Bi-S Based Free-Cutting Steel |
-
1989
- 1989-07-24 JP JP18886389A patent/JPH0356618A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100920621B1 (en) * | 2002-12-24 | 2009-10-08 | 주식회사 포스코 | Method for Manufacturing Billet of Bi-S Based Free-Cutting Steel |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0202336B1 (en) | Process for producing a thin plate of a high ferrosilicon alloy | |
| JPS5831062A (en) | Continuous cast steel strand | |
| JPS63112058A (en) | Continuous casting method | |
| KR940003251B1 (en) | Process for preparing rollable metal sheet from quench solidified thin cast sheet as starting material | |
| KR950005320B1 (en) | Process for producing thin sheet of cr-ni based stainless steel having excellent surface quality and workability | |
| JPH0356618A (en) | Production of free cutting steel | |
| JPH0565263B2 (en) | ||
| JPS63168260A (en) | Hot working method for continuously cast billet | |
| JP3215573B2 (en) | Continuous casting method of nickel-containing steel | |
| JPH0660369B2 (en) | Cr-Ni type stainless steel that is less likely to crack during the casting process or the subsequent hot rolling process | |
| EP0378705A1 (en) | PROCESS FOR PRODUCING THIN Cr-Ni STAINLESS STEEL SHEET EXCELLENT IN BOTH SURFACE QUALITY AND QUALITY OF MATERIAL | |
| JPS6320412A (en) | Hot working method for austenitic stainless steel containing mo and n | |
| KR920007883B1 (en) | Method of continous casting slabs to produce good surface quality hot-rolled band | |
| JP2561476B2 (en) | Method for preventing cracking during rapid solidification of Cr-Ni stainless steel or Cr-Ni high alloy steel | |
| KR100419644B1 (en) | A Method for Manufacturing Continuously Cast Strands from High Ni Containing Steel | |
| JPH03215625A (en) | Production of superplastic duplex stainless steel and hot working method therefor | |
| JP2971292B2 (en) | Manufacturing method of austenitic stainless steel with few surface defects | |
| JPS58144418A (en) | Manufacture of high-mn steel | |
| JPH0670253B2 (en) | Method for producing Cr-Ni type stainless steel thin plate having excellent surface quality and material | |
| JPH0730407B2 (en) | Method for producing Cr-Ni type stainless steel thin plate with excellent surface quality | |
| Wai et al. | A study of high temperature cracking in ferritic stainless steels | |
| JP2768527B2 (en) | Method for producing thin Cr-Ni stainless steel sheet with excellent workability | |
| JP2548942B2 (en) | Method for preventing cracking during rapid solidification of Fe-Ni based alloy | |
| JPS61193758A (en) | Production of hot worked steel material having good surface characteristic | |
| JP2020066047A (en) | Manufacturing method of steel piece |