JP2007289979A - Method for producing cast slab or steel ingot made of titanium-added case hardening steel and the cast slab or steel ingot, and case hardening steel made of the cast slab or steel ingot - Google Patents

Method for producing cast slab or steel ingot made of titanium-added case hardening steel and the cast slab or steel ingot, and case hardening steel made of the cast slab or steel ingot Download PDF

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JP2007289979A
JP2007289979A JP2006118602A JP2006118602A JP2007289979A JP 2007289979 A JP2007289979 A JP 2007289979A JP 2006118602 A JP2006118602 A JP 2006118602A JP 2006118602 A JP2006118602 A JP 2006118602A JP 2007289979 A JP2007289979 A JP 2007289979A
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Satoru Nakana
悟 中名
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Sanyo Special Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D25/00—Special casting characterised by the nature of the product
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cast slab of Ti-added case hardening steel in which the formation of TiN or N-enriched TiCN inclusions with a large diameter exerting adverse influence on its machinability is suppressed. <P>SOLUTION: The cast slab of a Ti-added case hardening steel with a diameter of ≤23 cm is provided which has a composition comprising, by mass, 0.10 to 0.30% C, 0.03 to 1.00% Si, 0.20 to 1.00% Mn, ≤0.025% P, 0.001 to 0.030% S, ≤0.0100% N, 0.05 to 0.20% Ti, 0.003 to 0.050% Al and ≤0.0030% O, and further comprising one or more kinds selected from 0.15 to 2.00% Cr, 0.10 to 2.00% Ni, 0.03 to 0.30% Mo, 0.0001 to 0.0020% B, 0.01 to 0.20% V and 0.01 to 0.15% Nb, and the balance Fe with inevitable impurities, wherein the maximum size √ (area max) of TiC or TiNC crystallized out at an observation area of 30,000 mm<SP>2</SP>in prediction by extreme value statistics is ≤50 μm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、自動車用部品やその他の種々の産業用機械や装置の部品に使用される機械構造用鋼においてＴｉを添加したはだ焼鋼からなる鋳鋼片または鋼塊の製造方法およびその鋳鋼片または鋼塊並びにはだ焼鋼からなる鋼材に関するものである。   The present invention relates to a method for producing cast steel pieces or ingots made of case-hardened steel to which Ti is added in machine structural steel used for parts for automobiles and other various industrial machines and devices, and the cast steel pieces. Or it is related with the steel materials which consist of a steel ingot and hardened steel.

従来、はだ焼鋼は一般に熱間加工や冷間加工、切削加工などにより所定の製品形状とした後、９００℃以上の浸炭焼入れ焼戻し処理が行われる。しかし、浸炭前組織や浸炭条件などの組み合わせにより、浸炭時に結晶粒の粗大化が発生して、鋼材の疲労強度や静的強度などの低下をもたらすことがある。それを防ぐために、はだ焼鋼においてはＡｌＮやＮｂＣＮといった析出物をピン止め粒子として活用する。このため、鋼材にＡｌ、Ｎｂ、Ｎなどの成分調整を行うことがある。Ｔｉ添加はだ焼鋼も結晶粒の粗大化防止を目的にＴｉを添加した鋼材である。しかしながら、このようなＴｉ添加はだ焼鋼では、硬質のＴｉＮまたはＮリッチなＴｉＣＮが多量に存在するため、その後の切削加工が困難となる問題がある。特に、量産炉にて溶解したＴｉ添加はだ焼鋼においてはその傾向が顕著に認められている。   Conventionally, a case hardening steel is generally formed into a predetermined product shape by hot working, cold working, cutting, or the like, and then carburized and tempered at 900 ° C. or higher. However, depending on the combination of the pre-carburization structure and the carburizing conditions, coarsening of crystal grains may occur during carburizing, leading to a decrease in fatigue strength and static strength of the steel material. In order to prevent this, precipitates such as AlN and NbCN are utilized as pinning particles in case-hardened steel. For this reason, components such as Al, Nb, and N may be adjusted to the steel material. Ti-added hardened steel is a steel material to which Ti is added for the purpose of preventing coarsening of crystal grains. However, in the case of such a Ti-added hardened steel, a large amount of hard TiN or N-rich TiCN is present, which makes it difficult to perform subsequent cutting. In particular, the tendency of Ti addition melted in a mass production furnace is noticeable in case-hardened steel.

出願人は、機械構造用Ｔｉ添加鋼の疲労特性に悪影響を及ぼすＴｉＮまたはＮリッチなＴｉＣＮの生成を抑制したＴｉ添加鋼において、極値統計法により予測した被検面積３０，０００ｍｍ2における鋼中に晶出のＴｉＮまたはＴｉＣＮの最大大きさの（ａｒｅａ ｍａｘ）1/2（以下、「√（ａｒｅａ ｍａｘ）」という。）が８０μｍ以下であるとしたＴｉ添加高強度鋼の発明を提案している（例えば、特許文献１参照。）。しかし、このＴｉ添加高強度鋼では、上記のように疲労強度を良好とするものであるが、この被削性は必ずしも優れていなかった。 Applicant has found that in Ti-added steel that suppresses the formation of TiN or N-rich TiCN that adversely affects the fatigue properties of Ti-added steel for machine structural use, in steel at a test area of 30,000 mm 2 predicted by the extreme statistical method. Proposed an invention of a Ti-added high-strength steel in which the maximum size (area max) 1/2 of the crystallized TiN or TiCN (hereinafter referred to as “√ (area max)”) is 80 μm or less. (For example, refer to Patent Document 1). However, this Ti-added high-strength steel has good fatigue strength as described above, but this machinability is not always excellent.

特開２００４−１４３５５０号公報JP 2004-143550 A

本発明が解決しようとする課題は、Ｔｉ含有の機械構造用鋼の鋼材から切削加工して製品形状とする際に、従来のＴｉ添加鋼においては十分に解決することができなかった被削性に悪影響を及ぼす大径のＴｉＮまたはＮリッチなＴｉＣＮの介在物の生成を抑制しうるＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊の製造方法およびその方法からなる鋳鋼片または鋼塊並びにその鋳鋼片または鋼塊からなるはだ焼鋼材を提供することである。   The problem to be solved by the present invention is a machinability that cannot be sufficiently solved by conventional Ti-added steels when it is cut from Ti-containing steel for machine structural steel into a product shape. Ti-added cast steel slab or steel ingot made of hardened steel that can suppress the formation of large-diameter TiN or N-rich TiCN inclusions that adversely affect the production, cast steel slab or steel ingot comprising the method, and It is to provide a case-hardened steel material made of cast steel pieces or ingots.

上記の課題を解決するための本発明の手段は、請求項１の発明では、はだ焼鋼の製造において、質量％で、Ｃ：０．１０〜０．３０％、Ｔｉ：０．０５〜０．２０％、Ｎ：０．０１００％以下の成分を含有する鋼を、直径２３ｃｍ以下の丸鋳鋼片または丸鋼塊に製造することを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊の製造方法である。   The means of the present invention for solving the above-mentioned problems is that, in the invention of claim 1, in the manufacture of case-hardened steel, in mass%, C: 0.10 to 0.30%, Ti: 0.05 to A steel containing 0.20% or less, N: 0.0100% or less of steel is produced into a round cast steel slab or round steel ingot having a diameter of 23 cm or less, or a cast steel slab comprising Ti-added hardened steel or It is a manufacturing method of a steel ingot.

請求項２の発明では、はだ焼鋼の製造において、質量％で、Ｃ：０．１０〜０．３０％、Ｔｉ：０．０５〜０．２０％、Ｎ：０．０１００％以下の成分を含有する鋼を、短辺２３ｃｍ以下の角鋳鋼片または角鋼塊に製造することを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊の製造方法である。   In the invention of claim 2, in the manufacture of case-hardened steel, the components in mass% are C: 0.10 to 0.30%, Ti: 0.05 to 0.20%, N: 0.0100% or less. A Ti-added cast steel slab or steel ingot manufacturing method is characterized by manufacturing a steel containing bismud into a square cast steel slab or square steel ingot having a short side of 23 cm or less.

請求項３の発明では、はだ焼鋼において、質量％で、Ｃ：０．１０〜０．３０％、Ｔｉ：０．０５〜０．２０％、Ｎ：０．０１００％以下の成分を含有し、直径または短辺が２３ｃｍ以下の鋳鋼片または鋼塊からなり、該鋳鋼片または鋼塊は極値統計法により予測した被検面積３０，０００ｍｍ2における鋼中に晶出のＴｉＮまたはＴｉＮＣの最大大きさ：√（ａｒｅａ ｍａｘ）が５０μｍ以下であることを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊である。 In the invention according to claim 3, in the case-hardened steel, in mass%, C: 0.10 to 0.30%, Ti: 0.05 to 0.20%, N: 0.0100% or less of components The cast steel piece or ingot has a diameter or short side of 23 cm or less, and the cast steel piece or ingot is made of TiN or TiNC crystallized in the steel in the test area 30,000 mm 2 predicted by the extreme value statistical method. The maximum size: √ (area max) is 50 μm or less, and Ti addition is a cast steel slab or ingot made of hardened steel.

請求項４の発明では、質量％で、Ｃ：０．１０〜０．３０％、Ｓｉ：０．０３〜１．００％、Ｍｎ：０．２０〜１．００％、Ｐ：０．０２５％以下、Ｓ：０．００１〜０．０３０％、Ｎ：０．０１００％以下、Ｔｉ：０．０５〜０．２０％、Ａｌ：０．００３〜０．０５０％、Ｏ：０．００３０％以下を含有し、さらにＣｒ：０．１５〜２．００％、Ｎｉ：０．１０〜２．００％、Ｍｏ：０．０３〜０．３０％、Ｂ：０．０００１〜０．００２０％、Ｖ：０．０１〜０．２０％、Ｎｂ：０．０１〜０．１５％の１種または２種以上を含有し、残部Ｆｅおよび不可避不純物からなる鋼からなり、直径または短辺が２３ｃｍ以下の鋳鋼片または鋼塊からなり、該鋳鋼片または鋼塊は極値統計法により予測した被検面積３０，０００ｍｍ2における鋼中に晶出のＴｉＮまたはＴｉＮＣの最大大きさ：√（ａｒｅａ ｍａｘ）が５０μｍ以下であることを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊である。 In the invention of claim 4, in mass%, C: 0.10 to 0.30%, Si: 0.03 to 1.00%, Mn: 0.20 to 1.00%, P: 0.025% Hereinafter, S: 0.001 to 0.030%, N: 0.0100% or less, Ti: 0.05 to 0.20%, Al: 0.003 to 0.050%, O: 0.0030% or less Cr: 0.15-2.00%, Ni: 0.10-2.00%, Mo: 0.03-0.30%, B: 0.0001-0.0020%, V : 0.01 to 0.20%, Nb: 0.01 to 0.15% of one or more, made of steel consisting of the balance Fe and inevitable impurities, the diameter or short side is 23cm or less consists cast steel strip or steel ingot, the template steel strip or steel ingot is in the inspection area 30,000 mm 2 predicted by extreme value statistics method Crystallization of TiN or TiNC maximum magnitude in: √ (area max) is cast steel strip or steel ingot consisting of Ti added hardening steel, characterized in that at 50μm or less.

請求項５の発明では、請求項１〜４のいずれか１項の手段の鋳鋼片または鋼塊を熱間圧延または熱間鍛造して得ることを特徴とするＴｉ添加はだ焼鋼鋼材である。   The invention according to claim 5 is a Ti-added hardened steel material obtained by hot rolling or hot forging the cast steel slab or steel ingot according to any one of claims 1 to 4. .

上記の発明の構成における限定理由を説明する。
先ず、成分限定理由について、なお、％は質量％を示す。 The reason for limitation in the configuration of the above invention will be described.
First, for reasons of component limitation,% indicates mass%.

Ｃ：０．１０〜０．３０％
Ｃは、素材の芯部の焼入性、鍛造性、機械加工性に影響する元素であり、Ｃが０．１０％未満では十分な芯部の硬さが得られず、強度が低下するため、０．１０％以上を含有する必要がある。しかし、０．３０％を超えると、素材の硬さが増加して被削性および鍛造性などの加工性を阻害する。そこでＣは０．１０〜０．３０％とする。 C: 0.10 to 0.30%
C is an element that affects the hardenability, forgeability, and machinability of the core of the material. If C is less than 0.10%, sufficient core hardness cannot be obtained and the strength decreases. , It is necessary to contain 0.10% or more. However, if it exceeds 0.30%, the hardness of the material increases, and the workability such as machinability and forgeability is hindered. Therefore, C is set to 0.10 to 0.30%.

Ｔｉ：０．０５〜０．２０％、好ましくは０．０５〜０．１５％
Ｔｉは浸炭時の結晶粒を微細化させるのに有効な元素であり、Ｔｉが０．０５％未満では浸炭時の結晶粒の微細化の効果は発揮されないので０．０５％以上を含有する必要がある。しかし、０．２０％を超えるとＴｉＮやＴｉＣＮを生成して被削性を阻害する。そこでＴｉは０．０５〜０．２０％、好ましくは０．０５〜０．１５％とする。 Ti: 0.05 to 0.20%, preferably 0.05 to 0.15%
Ti is an element effective for refining crystal grains during carburizing. If Ti is less than 0.05%, the effect of refining crystal grains during carburizing is not exhibited, so 0.05% or more must be contained. There is. However, if it exceeds 0.20%, TiN or TiCN is generated to inhibit machinability. Therefore, Ti is made 0.05 to 0.20%, preferably 0.05 to 0.15%.

Ｎ：０．０１００％以下、好ましくは０．００８０％以下
Ｎは上記のとおり、０．２０％を超えるＴｉと反応してＴｉＮやＴｉＣＮを生成してり被削性を阻害する。そこでＮは０．０１００％以下、好ましくは０．００８０％以下とする。 N: 0.0100% or less, preferably 0.0080% or less As described above, N reacts with Ti exceeding 0.20% to produce TiN or TiCN, thereby inhibiting machinability. Therefore, N is set to 0.0100% or less, preferably 0.0080% or less.

Ｓｉ：０．０３〜１．００％、好ましくは０．０５〜０．４０％
Ｓｉは脱酸に必要な元素であり、Ｓｉが０．０３％未満ではその効果は十分でなく、１．００％を超えると、素材の硬さが増加し被削性および鍛造性などの加工性を阻害する。そこでＳｉは０．０３〜１．００％、好ましくは０．０５〜０．４０％とする。 Si: 0.03 to 1.00%, preferably 0.05 to 0.40%
Si is an element necessary for deoxidation. If Si is less than 0.03%, the effect is not sufficient, and if it exceeds 1.00%, the hardness of the material increases and machining such as machinability and forgeability. Inhibits sex. Therefore, Si is 0.03 to 1.00%, preferably 0.05 to 0.40%.

Ｍｎ：０．２０〜１．００％、好ましくは０．２５〜０．７０％
Ｍｎは焼入れ性の確保に必要な元素であり、Ｍｎが０．２０％未満ではその効果は十分でなく、１．００％を超えると、素材の硬さが増加し被削性および鍛造性などの加工性を阻害する。そこでＭｎは０．２０〜１．００％、好ましくは０．２５〜０．７０％とする。 Mn: 0.20 to 1.00%, preferably 0.25 to 0.70%
Mn is an element necessary for ensuring hardenability. If Mn is less than 0.20%, the effect is not sufficient. If it exceeds 1.00%, the hardness of the material increases and machinability, forgeability, etc. Impairs the processability of Therefore, Mn is 0.20 to 1.00%, preferably 0.25 to 0.70%.

Ｓ：０．００１〜０．０３０％、好ましくは０．００３〜０．０２０％
Ｓは被削性の確保には有効な元素であり、Ｓが０．００１％未満ではその効果は十分でなく、好ましくは０．００３％以上を必要とし、０．０３０％を超えると、冷間加工性が阻害され、疲労強度が劣化する。そこでＳは０．００１〜０．０３０％、好ましくは０．００３〜０．０２０％とする。 S: 0.001 to 0.030%, preferably 0.003 to 0.020%
S is an element effective for ensuring machinability. If S is less than 0.001%, the effect is not sufficient, preferably 0.003% or more is required, and if it exceeds 0.030%, Interworkability is hindered and fatigue strength deteriorates. Therefore, S is 0.001 to 0.030%, preferably 0.003 to 0.020%.

Ａｌ：０．００３〜０．０５０％
Ａｌは製鋼時の脱酸に必要な元素であり、０．００３％以下では脱酸が不充分であり、０．０５０％を超えると、非金属介在物が生成して疲労強度が低下する。そこでＡｌは０．００３〜０．０５０％とする。 Al: 0.003 to 0.050%
Al is an element necessary for deoxidation at the time of steelmaking. If it is 0.003% or less, deoxidation is insufficient, and if it exceeds 0.050%, nonmetallic inclusions are generated and fatigue strength decreases. Therefore, Al is made 0.003 to 0.050%.

Ｐ：０．０２５％以下
Ｐは不純成分で浸炭部品の結晶粒界を脆化させるので、Ｐは０．０２５％以下とする。 P: 0.025% or less P is an impure component and embrittles the grain boundary of the carburized part. Therefore, P is set to 0.025% or less.

Ｏ：０．００３０％以下
Ｏは各種の非金属介在物を生成して浸炭部品の結晶粒界を脆化させるので、Ｏは０．００３０％以下とする。 O: 0.0030% or less O generates various non-metallic inclusions and embrittles the grain boundaries of the carburized parts, so O is made 0.0030% or less.

Ｃｒ、Ｎｉ、Ｍｏ、Ｂ、Ｖ、Ｎｂ：選択的に１種または２種以上とする。   Cr, Ni, Mo, B, V, Nb: selectively 1 type or 2 types or more.

Ｃｒ：０．１５〜２．００％
Ｃｒは焼入れ性の確保および靱性の向上に必要な元素であり、Ｃｒが０．１５％未満ではその効果は十分でなく、２．００％を超えると、素材の硬さが増加し被削性および鍛造性などの加工性を阻害する。そこでＣｒは０．１５〜２．００％とする。 Cr: 0.15-2.00%
Cr is an element necessary for ensuring hardenability and improving toughness. If Cr is less than 0.15%, the effect is not sufficient, and if it exceeds 2.00%, the hardness of the material increases and machinability. And workability such as forgeability is hindered. Therefore, Cr is made 0.15 to 2.00%.

Ｎｉ：０．１０〜２．００％
Ｎｉは靭性の向上に有効な元素である。しかし、Ｎｉは０．１０％未満ではその効果はなく、２．００％を超えると、素材の硬さが増加し、被削性および鍛造性などの加工性を阻害し、コストアップとなる。そこでＮｉは０．１０〜２．００％とする。 Ni: 0.10 to 2.00%
Ni is an element effective for improving toughness. However, if Ni is less than 0.10%, the effect is not obtained, and if it exceeds 2.00%, the hardness of the material is increased, and workability such as machinability and forgeability is hindered, resulting in an increase in cost. Therefore, Ni is set to 0.10 to 2.00%.

Ｍｏ：０．０３〜０．３０％
Ｍｏは靭性の向上に有効な元素であるが、０．０３％未満ではその効果はない。一方、Ｍｏは０．３０％を超えると、素材の硬さが増加し、被削性および鍛造性などの加工性を阻害し、コストアップとなる。そこでＭｏは０．０３〜０．３０％とする。 Mo: 0.03-0.30%
Mo is an element effective for improving toughness, but if it is less than 0.03%, there is no effect. On the other hand, if the Mo content exceeds 0.30%, the hardness of the material increases, which obstructs workability such as machinability and forgeability, and increases costs. Therefore, Mo is 0.03 to 0.30%.

Ｂ：０．０００１〜０．００２０％
Ｂは焼入れ性の向上に有効な元素であるが、０．０００１％未満ではその効果はなく、０．００２０％を超えると、その効果は飽和する。そこでＢは０．０００１〜０．００２０％とする。 B: 0.0001 to 0.0020%
B is an element effective for improving the hardenability, but if it is less than 0.0001%, there is no effect, and if it exceeds 0.0020%, the effect is saturated. Therefore, B is made 0.0001 to 0.0020%.

Ｖ：０．０１〜０．２０％
Ｖは結晶粒微細化し靱性向上に有効な元素であるが、０．０１％未満ではその効果はなく、０．２０％を超えると、結晶粒微細化の効果は飽和し、コストアップとなる。そこでＶは０．０１〜０．２０％とする。 V: 0.01-0.20%
V is an element effective for improving the toughness by refining crystal grains. However, if it is less than 0.01%, there is no effect, and if it exceeds 0.20%, the effect of crystal grain refining is saturated and the cost increases. Therefore, V is set to 0.01 to 0.20%.

Ｎｂ：０．０１〜０．１５％
Ｎｂは結晶粒微細化し靱性向上に有効な元素であるが、０．０１％未満ではその効果はなく、０．１５％を超えると、結晶粒微細化の効果は飽和し、コストアップとなる。そこでＮｂは０．０１〜０．１５％とする。 Nb: 0.01 to 0.15%
Nb is an element effective for improving the toughness by refining crystal grains. However, if it is less than 0.01%, there is no effect, and if it exceeds 0.15%, the effect of crystal grain refining is saturated and the cost increases. Therefore, Nb is set to 0.01 to 0.15%.

丸鋳片および丸鋼塊の直径２３ｃｍ以下、もしくは角鋳鋼片または角鋼塊の短辺２３ｃｍ以下
丸鋳片および丸鋼塊の直径もしくは角鋳鋼片または角鋼塊の短辺が２３ｃｍを超えると、ＴｉＮやＴｉＣＮの介在物のサイズが大きくなり、被削性に悪影響を及ぼすこととなる。そこで直径あるいは短辺が２３ｃｍ以下のサイズの鋳鋼片あるいは鋼塊に鋳造することで介在物のＴｉＮ、ＴｉＣＮのサイズが小さくでき、被削性への悪影響を低減することができる。そこで丸鋳片および丸鋼塊の直径２３ｃｍ以下、もしくは角鋳鋼片または角鋼塊の短辺２３ｃｍ以下とする。 When the diameter of round cast slab and round steel ingot is 23 cm or less, or the short side of square cast steel piece or square steel ingot is 23 cm or less, when the diameter of round cast slab and round steel ingot or the short side of square cast steel ingot or square steel ingot exceeds 23 cm, TiN Further, the size of inclusions of TiCN and TiCN is increased, which adversely affects machinability. Therefore, the size of inclusions TiN and TiCN can be reduced by casting into a cast steel piece or steel ingot having a diameter or short side of 23 cm or less, and the adverse effect on machinability can be reduced. Therefore, the diameter of the round slab and round steel ingot is 23 cm or less, or the short side of the square cast steel piece or square steel ingot is 23 cm or less.

√（ａｒｅａ ｍａｘ）が５０μｍ以下、好ましくは３０μｍ以下
極値統計法により予測した被検面積３０，０００ｍｍ2における鋼中に晶出する介在物のＴｉＮまたはＴｉＮＣの最大大きさの√（ａｒｅａ ｍａｘ）が５０μｍより大きいと被削性を阻害する。そこで介在物のＴｉＮまたはＴｉＮＣの最大大きさの√（ａｒｅａ ｍａｘ）を５０μｍ以下、好ましくは３０μｍ以下とする。 √ (area max) is 50 μm or less, preferably 30 μm or less √ (area max) of the maximum size of TiN or TiNC of inclusions crystallized in steel in the test area 30,000 mm 2 predicted by the extreme value statistical method If it is larger than 50 μm, machinability is hindered. Therefore, the maximum size √ (area max) of the inclusion TiN or TiNC is set to 50 μm or less, preferably 30 μm or less.

本発明による方法により製造のＴｉ添加のはだ焼鋼からなる鋳鋼片または鋼塊並びにこれらからなるＴｉ添加はだ焼鋼鋼材は、鋼材製造時の鋳片あるいは鋼塊の鋳造サイズの大きさを、丸形状のものではその直径を、角形状のものではその短辺を、それぞれ２３ｃｍ以下に規定することで、被削性に悪影響を及ぼすＴｉＮまたはＴｉＣＮからなる介在物の最大大きさの√（ａｒｅａ ｍａｘ）を５０μｍ以下とでき、その結果、本発明は被削性に優れたＴｉ添加はだ焼鋼からなる鋳鋼片もしくは鋼塊または鋼材を得ることができるなど、本発明の手段からなる製造方法およびその製造方法よりなる鋳鋼片または鋼塊並びにその鋳鋼片または鋼塊から熱間圧延または熱間鍛造して得たＴｉ添加はだ焼鋼鋼材は従来にない優れた効果を奏するものである。   Cast steel slabs or ingots made of Ti-added case-hardened steel manufactured by the method of the present invention and Ti-added case-hardened steel steel materials made of these materials have the same size as the cast slab or steel ingot when they are manufactured. By defining the diameter of the round shape and the short side of the square shape to 23 cm or less, the maximum size of the inclusion made of TiN or TiCN which adversely affects the machinability √ ( area max) can be 50 μm or less, and as a result, the present invention can produce a cast steel piece or steel ingot or steel material made of Ti-added hardened steel with excellent machinability, etc. The Ti-added hardened steel material obtained by hot rolling or hot forging from the cast steel slab or steel ingot and the cast steel slab or steel ingot comprising the method and its manufacturing method has an unprecedented excellent effect. is there.

本発明を実施するための最良の形態を以下に説明する。
表１および表２に示す成分からなる鋼を９０ｔ電気炉で溶製し、あるいは１ｔ真空溶解炉（１ｔＶＩＭ炉）で溶解生成し、種々のサイズの大きさに鋳造を行い、鋳鋼片および鋼塊とした。これらの鋳鋼片および鋼塊のサイズは、電気炉材では、短辺３８ｃｍ×長辺４９ｃｍの鋳鋼片とし、真空溶解炉材では、短辺１６ｃｍ×長辺１８ｃｍの鋼塊、または直径３０ｃｍの丸鋼塊、直径１９ｃｍの丸鋼塊をそれぞれ得た。これらの鋳鋼片および鋼塊を１２３０℃以上に加熱して、φ６０ｍｍおよびφ３２ｍｍの棒鋼に熱間鍛造した。得られた棒鋼について、９００℃で１時間の焼準処理を行った後に各試験片を作製した。なお、表１のＮｏ．１〜２０に区分でＴｉ添加鋼（請求成分）として本発明の請求項で規定する成分のＴｉ添加はだ焼鋼についての化学成分と適用の溶解炉を示す。なお、表１において網掛け部で示すＣｒ、Ｎｉ、Ｍｏは不可避的に含有される不純物である。さらに表２のＮｏ．２１〜２８に区分でＴｉ無添加鋼として、本発明で規定するＴｉ含有量未満の鋼を比較鋼として示し、Ｎｏ．２９〜３６に区分でＴｉ添加鋼（請求外成分）として、Ｔｉが本発明の請求項で規定する範囲から外れているか、本発明の請求項の範囲を満たしていても他の化学成分が本発明の請求項を満足しない成分からなる鋼について、それらを網掛け部で示し、それらの化学成分と溶解炉の種類を電気炉または１ｔＶＩＭとして示す。 The best mode for carrying out the present invention will be described below.
Steel consisting of the components shown in Table 1 and Table 2 is melted in a 90t electric furnace, or melted and generated in a 1t vacuum melting furnace (1tVIM furnace), cast into various sizes, cast steel pieces and ingots It was. The size of these cast steel pieces and steel ingots is a cast steel piece having a short side of 38 cm × long side of 49 cm in the case of an electric furnace material, and a steel ingot of short side of 16 cm × long side of 18 cm in a vacuum melting furnace material, or a round of 30 cm in diameter. Steel ingots and round steel ingots with a diameter of 19 cm were obtained. These cast steel pieces and steel ingots were heated to 1230 ° C. or higher, and hot forged into φ60 mm and φ32 mm steel bars. About the obtained steel bar, each test piece was produced after performing the normalization process for 1 hour at 900 degreeC. In Table 1, No. The Ti addition of the component prescribed | regulated by the claim of this invention as a Ti addition steel (claimed component) in 1-20 is shown about the chemical composition and application melting furnace about a hardened steel. In Table 1, Cr, Ni, and Mo indicated by the shaded portions are impurities inevitably contained. Further, in Table 2, No. As steels with no Ti content as defined in the present invention, steels with less than the Ti content defined in the present invention are shown as comparative steels in sections 21 to 28 as No. 1 steels. As Ti-added steels (unclaimed components) in 29 to 36, even if Ti is out of the range defined in the claims of the present invention or other chemical components are present even if they satisfy the scope of the claims of the present invention. For steels composed of components that do not satisfy the claims of the invention, they are indicated by hatching, and their chemical components and the type of melting furnace are indicated as an electric furnace or 1 tVIM.

Figure 2007289979
Figure 2007289979

Figure 2007289979
Figure 2007289979

φ６０ｍｍの棒鋼からＴｉＮまたはＴｉＮＣの最大大きさの√（ａｒｅａ ｍａｘ）を極値統計法により、棒鋼の中部および周部について被検面積：３０，０００ｍｍ2において予測した。さらに、φ６０ｍｍの棒鋼から超硬旋削試験片とドリル寿命試験片を作製して被削性の評価を行った。なお、表３に超硬旋削試験の条件を示し、表４にドリル寿命試験の条件を示す。一方、φ３２ｍｍの棒鋼からシャルピー衝撃試験片（角１０ｍｍ×５５ｍｍ−２ｍｍ１０ＲＣノッチ）および３点曲げ試験片（角１０ｍｍ×７０ｍｍ−２ｍｍＶノッチ）を作製し、試験に供した。なお、シャルピー試験片と３点曲げ試験片は、φ３２ｍｍの焼準処理材をφ３０ｍｍに旋削後、減面率５０％で引き抜き加工した棒鋼から試験片を割出し、９５０℃にて浸炭焼入れした後に、１８０℃の焼き戻しを実施してそれぞれ評価した。 √ (area max) of the maximum size of TiN or TiNC from a steel bar of φ60 mm was predicted at the test area: 30,000 mm 2 for the central part and the peripheral part of the steel bar by the extreme value statistical method. Furthermore, a carbide turning test piece and a drill life test piece were manufactured from a φ60 mm steel bar, and machinability was evaluated. Table 3 shows the conditions for the carbide turning test, and Table 4 shows the conditions for the drill life test. On the other hand, Charpy impact test pieces (10 mm square x 55 mm-2 mm 10 RC notch) and 3-point bend test pieces (10 mm square x 70 mm-2 mm V notch) were prepared from a steel bar having a diameter of 32 mm and subjected to the test. The Charpy test piece and the three-point bend test piece were obtained by turning a standardized material of φ32 mm to φ30 mm, indexing the test piece from a steel bar drawn at a surface reduction rate of 50%, and carburizing and quenching at 950 ° C. Each was evaluated by tempering at 180 ° C.

Figure 2007289979
Figure 2007289979

Figure 2007289979
Figure 2007289979

上記の各種の鋳片サイズおよび鋼塊サイズにおける試験結果を表５に示す。これらの表５において、鋳片サイズおよび鋼塊サイズとして、丸鋳片および丸鋼塊の場合は直径で、角状の鋳片および鋼塊の場合はその短辺でその大きさを示している。   Table 5 shows the test results for various slab sizes and steel ingot sizes. In these Table 5, as the slab size and the steel ingot size, the diameter is shown in the case of round slabs and round steel ingots, and the size is shown in the short side in the case of square slabs and steel ingots. .

Figure 2007289979
Figure 2007289979

表５において奇数番のＮｏ．のものは、鋳片および鋼塊サイズが丸型のものではその直径が、角型のものではその短辺が２３ｃｍを超えるものである。これに対し、偶数番のＮｏ．のものは、鋳片および鋼塊サイズが丸型のものではその直径が、角型のものではその短辺が２３ｃｍ以内のものである。表５および図１に見られるように、本発明の請求項に規定する化学成分を有するＴｉ添加はだ焼鋼のＮｏ．１〜２０の２０種中の偶数番の１０種のものは、鋳片および鋼塊サイズの直径または短径の値が２３ｃｍ以下の小さなものであり、この場合、ＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）は３９μｍ以下で、奇数番の１０種のものよりも小さいことがわかる。   In Table 5, the odd number No. In the case of the slab and the steel ingot size, the diameter is round, and in the case of the square, the short side exceeds 23 cm. On the other hand, even number No. In the case of the slab and the steel ingot size, the diameter is round, and in the case of the square, the short side is within 23 cm. As can be seen in Table 5 and FIG. 1, the Ti-added hardened steel having the chemical composition defined in the claims of the present invention is No. 10 of the even numbers among the 20 types of 1 to 20 are small ones having a slab and steel ingot size diameter or short axis value of 23 cm or less. In this case, the maximum size of TiN or TiCN It can be seen that √ (area max) is 39 μm or less, which is smaller than the odd number of 10 types.

さらに表５および図１から、同一の鋳片サイズおよび鋼塊サイズで比較すると、表５のＮｏ．１〜２０の本発明の請求成分のＴｉ添加はだ焼鋼のＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）は、表５のＮｏ．２９〜３６の本発明の請求外成分のＴｉ添加鋼よりも、小さいことがわかる。   In addition, from Table 5 and FIG. The maximum size √ (area max) of TiN or TiCN in the case of Ti-added hardened steel of claim 1 to 20 according to the present invention is shown in No. 5 of Table 5. It turns out that it is smaller than Ti addition steel of 29-36 of the non-claimed component of this invention.

さらに表５および図２から、表５のＮｏ．１〜２０の本発明の請求項に規定する成分のＴｉ添加鋼の中で、本発明である１０種の偶数番の鋳片および鋼塊サイズの直径または短径の値が２３ｃｍ以下の小さなものでは、ＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）が小さいほど、超硬旋削試験によるチップの磨耗量が少なく、かつ、鋳片および鋼塊サイズの直径または短径の値が２３ｃｍより大きな奇数番のものに比して小さいことがわかる。   Further, from Table 5 and FIG. Among Ti-added steels of the components defined in the claims of 1 to 20 of the present invention, the ten kinds of even-numbered slabs according to the present invention and the small ingots having a diameter or minor axis value of 23 cm or less Then, the smaller the √ (area max) of the maximum size of TiN or TiCN is, the smaller the wear amount of the chip by the carbide turning test, and the diameter or short diameter value of the slab and the ingot size is larger than 23 cm. It can be seen that it is smaller than the odd one.

さらに表５および図３から、表５のＮｏ．１〜２０の本発明のＴｉ添加鋼のものは、ＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）の小さい鋳片および鋼塊サイズの直径または短径の値が２３ｃｍ以下の偶数番の本発明のものは、ドリル穿孔数が奇数番のものよりも、多くなっていることがわかる。   Further, from Table 5 and FIG. 1 to 20 Ti-added steels according to the present invention include a slab having a small maximum √ (area max) of TiN or TiCN, and an even-numbered book having a steel ingot size diameter or minor axis value of 23 cm or less. It can be seen that the invention has more drill holes than the odd number.

表５のＮｏ．１〜２０の本発明の成分範囲のＴｉ添加鋼のものは、結晶粒の粗大化は認められず、従って、その衝撃強度および３点曲げ試験による亀裂発生荷重は、表５のＮｏ．２１〜２８の比較鋼である非Ｔｉ添加鋼のものよりも高く、本発明のＴｉ添加鋼は優れていることがわかる。   No. in Table 5 In the case of Ti-added steel having the component range of 1 to 20 of the present invention, no coarsening of crystal grains was observed, and therefore, the impact strength and crack initiation load by the three-point bending test are No. 5 in Table 5. It is higher than that of non-Ti-added steel, which is a comparative steel of 21 to 28, and it can be seen that the Ti-added steel of the present invention is superior.

鋳片および鋼塊サイズとＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）の関係を示すグラフである。It is a graph which shows the relationship of slab and steel ingot size, and √ (area max) of the maximum size of TiN or TiCN. ＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）と超硬旋削試験によるチップの磨耗量の関係を示すグラフである。It is a graph which shows the relationship between √ (area max) of the maximum size of TiN or TiCN and the wear amount of the chip by the carbide turning test. ＴｉＮまたはＴｉＣＮの最大大きさの√（ａｒｅａ ｍａｘ）とドリル穿孔数の関係を示すグラフである。It is a graph which shows the relation of √ (area max) of the maximum size of TiN or TiCN and the number of drill holes.

Claims (5)

はだ焼鋼の製造において、質量％で、Ｃ：０．１０〜０．３０％、Ｔｉ：０．０５〜０．２０％、Ｎ：０．０１００％以下の成分を含有する鋼を、直径２３ｃｍ以下の丸鋳鋼片または丸鋼塊に製造することを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊の製造方法。   In the manufacture of case-hardened steel, a steel containing components of C: 0.10 to 0.30%, Ti: 0.05 to 0.20%, N: 0.0100% or less in mass% A method for producing a cast steel piece or ingot made of Ti-added hardened steel, characterized in that it is produced into a round cast steel piece or round ingot of 23 cm or less. はだ焼鋼の製造において、質量％で、Ｃ：０．１０〜０．３０％、Ｔｉ：０．０５〜０．２０％、Ｎ：０．０１００％以下の成分を含有する鋼を、短辺２３ｃｍ以下の角鋳鋼片または角鋼塊に製造することを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊の製造方法。   In the production of bare steel, a steel containing components of C: 0.10 to 0.30%, Ti: 0.05 to 0.20%, N: 0.0100% or less in terms of mass% is short. A method for producing a cast steel piece or ingot made of Ti-added hardened steel, characterized in that it is produced into a square cast steel piece or square steel ingot having a side of 23 cm or less. はだ焼鋼において、質量％で、Ｃ：０．１０〜０．３０％、Ｔｉ：０．０５〜０．２０％、Ｎ：０．０１００％以下の成分を含有し、直径または短辺が２３ｃｍ以下の鋳鋼片または鋼塊からなり、該鋳鋼片または鋼塊は極値統計法により予測した被検面積３０，０００ｍｍ2における鋼中に晶出のＴｉＮまたはＴｉＮＣの最大大きさ：（ａｒｅａ ｍａｘ）1/2（以下、「√（ａｒｅａ ｍａｘ）」という。）が５０μｍ以下であることを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊。 In case-hardened steel, it contains components of C: 0.10 to 0.30%, Ti: 0.05 to 0.20%, N: 0.0100% or less in mass%, and the diameter or short side is The cast steel slab or steel ingot is 23 cm or less, and the cast steel slab or ingot is the maximum size of TiN or TiNC crystallized in the steel in the test area 30,000 mm 2 predicted by the extreme value statistical method: (area max ) A cast steel slab or ingot made of Ti-added hardened steel, characterized in that 1/2 (hereinafter referred to as “√ (area max)”) is 50 μm or less. 質量％で、Ｃ：０．１０〜０．３０％、Ｓｉ：０．０３〜１．００％、Ｍｎ：０．２０〜１．００％、Ｐ：０．０２５％以下、Ｓ：０．００１〜０．０３０％、Ｎ：０．０１００％以下、Ｔｉ：０．０５〜０．２０％、Ａｌ：０．００３〜０．０５０％、Ｏ：０．００３０％以下を含有し、さらにＣｒ：０．１５〜２．００％、Ｎｉ：０．１０〜２．００％、Ｍｏ：０．０３〜０．３０％、Ｂ：０．０００１〜０．００２０％、Ｖ：０．０１〜０．２０％、Ｎｂ：０．０１〜０．１５％の１種または２種以上を含有し、残部Ｆｅおよび不可避不純物からなる鋼からなり、直径または短辺が２３ｃｍ以下の鋳鋼片または鋼塊からなり、該鋳鋼片または鋼塊は極値統計法により予測した被検面積３０，０００ｍｍ2における鋼中に晶出のＴｉＮまたはＴｉＮＣの最大大きさ：√（ａｒｅａ ｍａｘ）が５０μｍ以下であることを特徴とするＴｉ添加はだ焼鋼からなる鋳鋼片または鋼塊。 In mass%, C: 0.10 to 0.30%, Si: 0.03 to 1.00%, Mn: 0.20 to 1.00%, P: 0.025% or less, S: 0.001 -0.030%, N: 0.0100% or less, Ti: 0.05-0.20%, Al: 0.003-0.050%, O: 0.0030% or less, Cr: 0.15-2.00%, Ni: 0.10-2.00%, Mo: 0.03-0.30%, B: 0.0001-0.0020%, V: 0.01-0. 20%, Nb: 0.01 to 0.15% of one or more, made of steel consisting of the remainder Fe and inevitable impurities, made of cast steel pieces or steel ingots with a diameter or short side of 23 cm or less , the template steel strip or steel ingot is crystallization of TiN in the steel in a subject area 30,000 mm 2 predicted by extreme value statistics method or The maximum size of TiNC: √ (area max) is cast steel strip or the steel ingot of Ti added hardening steel, characterized in that at 50μm or less. 請求項１〜４のいずれか１項に記載の鋳鋼片または鋼塊を熱間圧延または熱間鍛造して得ることを特徴とするＴｉ添加はだ焼鋼鋼材。   A Ti-added hardened steel material obtained by hot rolling or hot forging the cast steel piece or steel ingot according to any one of claims 1 to 4.
JP2006118602A 2006-04-23 2006-04-23 Method for producing cast slab or steel ingot made of titanium-added case hardening steel and the cast slab or steel ingot, and case hardening steel made of the cast slab or steel ingot Pending JP2007289979A (en)

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