JP2015206090A - Die steel for plastic molding and manufacturing method therefor - Google Patents
Die steel for plastic molding and manufacturing method therefor Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 46
- 239000010959 steel Substances 0.000 title claims abstract description 46
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 11
- 238000010137 moulding (plastic) Methods 0.000 title claims abstract description 11
- 230000032683 aging Effects 0.000 claims abstract description 21
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 8
- 239000012535 impurity Substances 0.000 claims abstract description 7
- 239000000203 mixture Substances 0.000 claims abstract description 7
- 239000002184 metal Substances 0.000 claims abstract description 6
- 229910052751 metal Inorganic materials 0.000 claims abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 6
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 4
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 4
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 4
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 3
- 239000002245 particle Substances 0.000 claims description 13
- 229910001214 P-type tool steel Inorganic materials 0.000 claims description 7
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims 1
- 239000010931 gold Substances 0.000 claims 1
- 229910052737 gold Inorganic materials 0.000 claims 1
- 229910052720 vanadium Inorganic materials 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 16
- 238000010438 heat treatment Methods 0.000 abstract description 13
- 230000008569 process Effects 0.000 abstract description 7
- 239000006104 solid solution Substances 0.000 abstract description 6
- 239000000243 solution Substances 0.000 abstract description 6
- 230000001105 regulatory effect Effects 0.000 abstract description 4
- 239000002131 composite material Substances 0.000 abstract 1
- 230000002708 enhancing effect Effects 0.000 abstract 1
- 238000001556 precipitation Methods 0.000 description 17
- 229910000943 NiAl Inorganic materials 0.000 description 12
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 12
- 230000000694 effects Effects 0.000 description 12
- 230000007423 decrease Effects 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 238000013461 design Methods 0.000 description 6
- 150000001247 metal acetylides Chemical class 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 238000001816 cooling Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 229910000765 intermetallic Inorganic materials 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229920003023 plastic Polymers 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 239000002436 steel type Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 229910003310 Ni-Al Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 238000004881 precipitation hardening Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 230000035945 sensitivity Effects 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- 239000006061 abrasive grain Substances 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- 229910001105 martensitic stainless steel Inorganic materials 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
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- 238000007711 solidification Methods 0.000 description 1
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- 238000009628 steelmaking Methods 0.000 description 1
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- 238000005496 tempering Methods 0.000 description 1
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Abstract
Description
この発明は、プリハードンタイプの高清浄度のプラスチック成形金型鋼およびその製造方法に関するものである。 The present invention relates to a pre-hardened high-purity plastic mold steel and a method for producing the same.
プラスチック成形では、プラスチックが充填される金型の意匠面がプラスチックに転写されることから、金型の表面肌を管理する必要があり、鏡面磨き性は金型鋼として重要な特性の一つである。金型の鏡面磨き性に作用する因子の一つとして金型鋼の硬さが挙げられる。一般的に金型鋼の硬さが高いほど鏡面性は良くなる。これは、素地の硬さと、工業的に鋼を製造する上で不可避に生成する硬質な非金属介在物などとの硬さの差異が小さくなるためなどとして解釈されている。 In plastic molding, the design surface of the mold filled with plastic is transferred to the plastic, so it is necessary to manage the surface of the mold, and mirror polishability is one of the important characteristics of mold steel. . One factor affecting the mirror polishability of the mold is the hardness of the mold steel. Generally, the higher the hardness of the mold steel, the better the specularity. This is interpreted as the difference in hardness between the substrate hardness and the hard non-metallic inclusions that are inevitably generated when industrially manufacturing steel is reduced.
プラスチック製品の種々の鏡面性の要求に応えるために、様々な硬さを有する鋼種が金型鋼として製品化されている。例えば、研磨材の粒度がＪＩＳ＃２０００程度の比較的低い鏡面性で足りる場合には、ショア硬さが３０ＨＳ程度の炭素鋼が、また、＃１００００以上の高い鏡面性が必要な場合には、５０ＨＳを超えるマルテンサイト系ステンレス鋼などが使われている。 In order to meet the various specularity requirements of plastic products, steel types having various hardness have been commercialized as mold steel. For example, when a relatively low specularity of about JIS # 2000 is sufficient for the abrasive grain size, a carbon steel with a Shore hardness of about 30 HS is required, and when a high specularity of # 10000 or more is required, Martensitic stainless steel exceeding 50HS is used.
また、マルテンサイトもしくはベイナイトの素地に、鋼の製造工程において付加される熱処理によってＮｉ−Ａｌ系金属間化合物及びＣｕなどを時効析出させ、硬さをロックウェル硬さで４０ＨＲＣ（５４ＨＳ）程度に調整して出荷されるプリハードンタイプの金型鋼がある。特許文献１、特許文献２、特許文献３、特許文献４及び特許文献５では、金属間化合物であるＮｉＡｌを析出させており、ＮｉＡｌの析出強化作用によって硬さを確保することがこれらに共通した特徴となっている。 Also, Ni-Al intermetallic compounds and Cu are aged on the martensite or bainite substrate by a heat treatment applied in the steel manufacturing process, and the hardness is adjusted to about 40 HRC (54 HS) with Rockwell hardness. And pre-hardened mold steels. In Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5, NiAl that is an intermetallic compound is precipitated, and it is common to secure hardness by the precipitation strengthening action of NiAl. It is a feature.
特許文献１、特許文献２、特許文献３、特許文献４及び特許文献５には、前記した析出硬化タイプの金型鋼の耐食性を改善するために、一定量のＣｒが添加された鋼種が提案されている。耐食性は塩化ビニルにおける塩素ガスなどのように、高腐食性のガスが発生する樹脂を用いる場合に必要である。また、金型内の溶融樹脂の合流部分において発生するウェルドラインを防止するために、近年になって金型の意匠面を急速加熱・冷却するウェルドレス成形法が開発された。この方法において、意匠面近傍に設けた配管内に蒸気や液体を通して加熱や冷却を行う場合、配管内表面に錆が生じれば金型への伝熱効率が低下するので、この点からも耐食性が必要である。このように、Ｃｒは耐食性の向上を目的として添加されているが、添加により生じるＣｒ系炭化物を積極的に硬さ向上に利用した例はない。 Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4 and Patent Document 5 propose a steel type to which a certain amount of Cr is added in order to improve the corrosion resistance of the precipitation hardening type mold steel. ing. Corrosion resistance is necessary when using a resin that generates highly corrosive gases such as chlorine gas in vinyl chloride. In recent years, a weldless molding method has been developed in which a design surface of a mold is rapidly heated and cooled in order to prevent a weld line generated at a joining portion of molten resin in the mold. In this method, when heating or cooling is performed through steam or liquid in the piping provided near the design surface, if rust is generated on the inner surface of the piping, the heat transfer efficiency to the mold is reduced. is necessary. Thus, Cr is added for the purpose of improving the corrosion resistance, but there is no example in which Cr-based carbide generated by the addition is positively used for improving the hardness.
上記した析出硬化タイプの金型鋼では、主にＮｉ−Ａｌ系金属間化合物の析出によって必要な硬さを得ることから、Ｎｉを２．０％〜５．０％程度含有している。しかしながら、近年Ｎｉの価格は高騰しており、適正な価格での普及を実現する観点から、上記タイプの金型鋼におけるＮｉ含有量の低下が望まれている。 The above-described precipitation hardening type mold steel contains about 2.0% to 5.0% of Ni because the necessary hardness is obtained mainly by precipitation of Ni—Al intermetallic compounds. However, in recent years, the price of Ni has soared, and from the viewpoint of realizing widespread use at an appropriate price, it is desired to reduce the Ni content in the above-described mold steel.
また、上記タイプの金型鋼では、ＮｉＡｌ等の微細析出物による析出強化を利用するため、固溶化後に時効処理を行うのが一般的である。固溶化後の冷却の際は、十分な速度で冷却し、マルテンサイト変態させる必要があるが、同鋼種群のマルテンサイト変態開始温度（Ｍｓ点）は４２０℃程度であるため、固溶化後に室温〜２００℃の温度域まで冷却する必要がある。また、上記タイプの金型鋼では室温〜４００℃の温度域では時効による硬さ向上の効果が得られず、４００℃〜５５０℃の温度域では逆に硬さが過剰となる場合があるため、プリハードンタイプの金型用鋼に求められる４０ＨＲＣの硬さを満たすには、５５０℃〜６００℃程度まで加熱し、時効に加え焼戻し効果を与える必要があり、工程上効率が悪いという問題がある。 In addition, in the above type of mold steel, aging treatment is generally performed after solidification in order to utilize precipitation strengthening by fine precipitates such as NiAl. At the time of cooling after solid solution, it is necessary to cool at a sufficient rate to cause martensitic transformation. However, since the martensitic transformation start temperature (Ms point) of the same steel type group is about 420 ° C., it is room temperature after solid solution. It is necessary to cool to a temperature range of ˜200 ° C. In addition, in the above-described mold steel, the effect of improving the hardness due to aging cannot be obtained in the temperature range of room temperature to 400 ° C, and the hardness may be excessive in the temperature range of 400 ° C to 550 ° C. In order to satisfy the hardness of 40 HRC required for pre-hardened mold steel, it is necessary to heat to about 550 ° C. to 600 ° C. to give a tempering effect in addition to aging, and there is a problem that the efficiency in the process is poor.
本発明は上記の課題を解決するためになされたもので、希少金属であるＮｉ量を低減し、かつＭｓ点の向上、また炭化物を主とした組織で構成されていることによる時効温度の低減により熱処理工程の効率化を可能とするプリハードンタイプの高清浄度プラスチック成形金型鋼およびその製造方法を提供することを目的とする。 The present invention has been made in order to solve the above-mentioned problems. The amount of Ni which is a rare metal is reduced, the Ms point is improved, and the aging temperature is reduced by being composed of a structure mainly composed of carbides. It is an object of the present invention to provide a pre-hardened type high cleanliness plastic molding die steel and a method for manufacturing the same, which can improve the efficiency of the heat treatment process.
本発明のプラスチック成形金型鋼のうち、第１の本発明は、質量％で、Ｃ：０．０１〜０．１５％、Ｓｉ：０．５〜２．０％、Ｍｎ：０．３〜２．０％、Ｃｒ：２．０〜６．０％、Ｎｉ：２．０％未満、Ａｌ：０．５％以下、Ｂ：０．００１〜０．０１％、ＭｏとＷを単独もしくは複合でＭｏ＋１／２Ｗ：０．４〜１．５％を含有し、残部がＦｅ及び不可避不純物からなり、かつ不可避不純物中でＣｕ：０．２５％以下、Ｓ：０．００２％以下、Ｏ：０．００１５％以下、Ｎ：０．０１％以下に規制した組成を有することを特徴とする。 Among the plastic mold steels of the present invention, the first present invention is mass%, C: 0.01 to 0.15%, Si: 0.5 to 2.0%, Mn: 0.3 to 2 0.0%, Cr: 2.0 to 6.0%, Ni: less than 2.0%, Al: 0.5% or less, B: 0.001 to 0.01%, Mo and W alone or in combination Mo + 1 / 2W: 0.4 to 1.5%, with the balance being Fe and inevitable impurities, and Cu: 0.25% or less, S: 0.002% or less, O: 0.0. It has a composition restricted to 0015% or less and N: 0.01% or less.
第２の本発明のプラスチック成形金型鋼は、前記第１の本発明において、前記組成として、さらにＶ：０．３％以下を含有することを特徴とする。 The plastic mold steel according to the second aspect of the present invention is characterized in that, in the first aspect of the present invention, the composition further contains V: 0.3% or less.
第３の本発明のプラスチック成形金型鋼は、前記第１または第２の本発明において、Ｍｓ点が４２０℃以上であることを特徴とする。 The plastic mold steel of the third aspect of the present invention is characterized in that, in the first or second aspect of the present invention, the Ms point is 420 ° C. or higher.
第４の本発明のプラスチック成形金型鋼は、前記第１〜第３の本発明のいずれかにおいて、鋼中に存在するＭ２３Ｃ６型のＣｒ系炭化物粒子の平均粒径が等価円直径で７０ｎｍ以下であることを特徴とする。 The plastic mold steel of the fourth aspect of the present invention is the plastic mold steel according to any one of the first to third aspects of the present invention, wherein the average particle diameter of the M 23 C 6 type Cr-based carbide particles present in the steel is an equivalent circular diameter. It is 70 nm or less.
第５の本発明のプラスチック成形用金型鋼の製造方法は、前記第１〜第３の本発明のいずれかに記載のプラスチック成形用金型鋼に、固溶化処理を行った後、４００℃〜５５０℃で時効処理を行うことを特徴とする。 According to a fifth aspect of the present invention, there is provided a method of producing a mold steel for plastic molding according to any one of the first to third aspects of the present invention. An aging treatment is performed at ° C.
本発明では硬さ向上の手段として、上記特許文献で用いられたＮｉＡｌの析出を必要とせず、微細なＭ２３Ｃ６型のＣｒを主構成元素とする炭化物の析出を利用することによって、希少金属であるＮｉの低減を実現している。前記炭化物は等価円直径７０ｎｍ以下が望ましく、より望ましくは等価円直径２〜５０ｎｍである。さらに、これらの結果生じるＭｓ点の向上及び析出温度の低下によって、固溶化後の下げ切り温度及び時効温度をそれぞれ向上及び低下させ、効率的な熱処理工程が可能となることを見出した。 The present invention does not require the precipitation of NiAl used in the above-mentioned patent document as a means for improving the hardness, and makes use of the precipitation of carbides containing fine M 23 C 6 type Cr as the main constituent element. Reduction of Ni which is a metal is realized. The carbide preferably has an equivalent circular diameter of 70 nm or less, and more preferably has an equivalent circular diameter of 2 to 50 nm. Furthermore, it has been found that the resulting Ms point and the precipitation temperature are lowered, so that the lowering temperature and the aging temperature after solid solution are raised and lowered, respectively, and an efficient heat treatment process becomes possible.
次に、本発明で成分範囲を限定した理由を以下に説明する。
Ｃ：０．０１〜０．１５％
Ｃは焼入れ性を向上させる元素であり、また目的の硬さに調整するためにも０．０１％以上の含有が必要である。一方、多量に含有した場合にはＣｒと結合して過剰の炭化物を形成し、素地のＣｒ濃度低下に伴って耐食性が低下するとともに、溶接性も劣化することから、その上限を０．１５％とする。なお、同様の理由で下限を０．０３％、上限を０．１％とするのが望ましい。
Next, the reason for limiting the component range in the present invention will be described below.
C: 0.01 to 0.15%
C is an element that improves the hardenability and needs to be contained in an amount of 0.01% or more in order to adjust to the desired hardness. On the other hand, when it is contained in a large amount, it combines with Cr to form excess carbides, and as the Cr concentration in the substrate decreases, the corrosion resistance decreases and the weldability also deteriorates, so the upper limit is 0.15% And For the same reason, it is desirable that the lower limit is 0.03% and the upper limit is 0.1%.
Ｓｉ：０．５〜２．０％
Ｓｉは溶製時に脱酸剤として作用するとともに、被削性を向上させる効果も有する。そのためには、０．５％以上の含有を要する。一方、含有量が多い場合は、成分偏析が生じて鏡面性を劣化させるとともに、過度の靱性低下を招くので、その含有量の上限を２．０％とする。なお、同様の理由で下限を０．５％、上限を１．５％とするのが望ましい。
Si: 0.5 to 2.0%
Si acts as a deoxidizer during melting and has an effect of improving machinability. For that purpose, 0.5% or more of content is required. On the other hand, when the content is large, component segregation occurs and the specularity is deteriorated and excessive toughness is lowered. Therefore, the upper limit of the content is set to 2.0%. For the same reason, it is desirable to set the lower limit to 0.5% and the upper limit to 1.5%.
Ｍｎ：０．３〜２．０％
Ｍｎは焼入れ性向上に効果的な元素であり、添加により良好な機械的特性を得ることができる。その効果を得るためには、０．３％以上の含有が必要である。ただし、過度の含有は靱性の低下を招くので、上限を２．０％とした。なお、同様の理由で下限を０．３％、上限を１．５％とするのが望ましい。
Mn: 0.3 to 2.0%
Mn is an element effective for improving hardenability, and good mechanical properties can be obtained by addition. In order to acquire the effect, containing 0.3% or more is required. However, excessive content causes a decrease in toughness, so the upper limit was made 2.0%. For the same reason, it is desirable to set the lower limit to 0.3% and the upper limit to 1.5%.
Ｃｒ：２．０〜６．０％
Ｃｒは耐食性の向上及び焼入れ性の向上に有効な元素であり、加えて本発明ではＣと結合して微細なＭ２３Ｃ６型炭化物を形成し、硬さを向上させる作用ももたらす。含有量を増加させるほどこれらの効果は顕著となるが、一方で過度の含有は熱伝導率、耐食性及び溶接性の低下につながることから、含有量を２．０〜６．０％に調整する必要がある。なお、同様の理由で下限を３．０％、上限を５．０％とするのが望ましい。
Cr: 2.0-6.0%
Cr is an element effective for improving corrosion resistance and hardenability. In addition, in the present invention, it combines with C to form fine M 23 C 6 type carbide, and also has an effect of improving hardness. These effects become more prominent as the content is increased, but excessive content leads to a decrease in thermal conductivity, corrosion resistance and weldability, so the content is adjusted to 2.0 to 6.0%. There is a need. For the same reason, it is desirable to set the lower limit to 3.0% and the upper limit to 5.0%.
Ｎｉ：２．０％未満
ＮｉはＡｌと結合してＮｉＡｌを形成するが、本発明ではＮｉＡｌの析出を必要とせず、希少金属であるＮｉを低減した組織設計とすることから、含有量上限を２．０％未満としている。
なお、極端な焼入れ性の低下を防ぎ、加えて母相の強度と靱性を確保する目的から、下限を０．５％とするのが望ましい。
Ni: Less than 2.0% Ni combines with Al to form NiAl, but the present invention does not require precipitation of NiAl and has a structure design in which Ni which is a rare metal is reduced. Less than 2.0%.
In order to prevent an extreme decrease in hardenability and to secure the strength and toughness of the parent phase, it is desirable to set the lower limit to 0.5%.
Ａｌ：０．５％以下
これまでプリハードンタイプの金型材ではＮｉＡｌの析出強化を利用しているため、Ａｌを添加しなければならなかったが、本発明はＮｉＡｌを析出させない設計であるため、ＮｉＡｌを析出させるためのＡｌは不要である。ただし、製鋼時の脱酸効果を得るためにＡｌを添加してもよいが、その場合の含有量の上限は０．５％とする。なお、ＮｉＡｌの析出を抑制するため、上限を０．０５％未満とするのが望ましく、さらに０．０３％以下とするのが一層望ましい。
Al: 0.5% or less In the past, pre-hardened mold materials used NiAl precipitation strengthening, so Al had to be added. However, since the present invention is designed not to precipitate NiAl, NiAl Al for precipitating is not necessary. However, Al may be added to obtain a deoxidation effect during steelmaking, but the upper limit of the content in that case is 0.5%. In order to suppress NiAl precipitation, the upper limit is preferably less than 0.05%, and more preferably 0.03% or less.
Ｂ：０．００１〜０．０１％
Ｂは焼入れ性の向上効果を有するに加えて、被削性を付与させる作用もあるため、０．００１％以上の含有が必要である。一方で過度に含有した場合は、熱間加工性を阻害することに加えて溶接時の割れ感受性を高めるために、その上限を０．０１％とする。なお、上記と同様の理由で上限を０．００５％とするのが望ましい。
B: 0.001 to 0.01%
In addition to improving the hardenability, B also has an effect of imparting machinability, so it is necessary to contain 0.001% or more. On the other hand, when it contains excessively, in order to increase the cracking sensitivity at the time of welding in addition to inhibiting hot workability, the upper limit is made 0.01%. For the same reason as described above, it is desirable to set the upper limit to 0.005%.
Ｃｕ：０．２５％以下
Ｃｕは時効処理によって析出し、素材を硬化させる作用を有するものの、靱性を著しく劣化させる。また、Ｃｕ添加鋼を製造した場合、鋼塊製造用の設備がＣｕで汚染されて、同一設備を使って製造するその後の製品にＣｕが混入する可能性がある。Ｃｕは熱間加工性の著しい低下をもたらすので、Ｃｕ添加鋼を製造した後に、比較的Ｃｕ感受性が低い鋼を釜洗いの目的で製造するなどの制約が生じる。したがって、Ｃｕ含有量は、不可避不純物として極力低減させる必要があり、上限を０．２５％に規制する。
Cu: 0.25% or less Cu is precipitated by aging treatment and has a function of hardening the material, but significantly deteriorates toughness. Moreover, when manufacturing Cu addition steel, the equipment for steel ingot manufacture is contaminated with Cu, and Cu may mix in the subsequent product manufactured using the same equipment. Since Cu causes a significant decrease in hot workability, there is a restriction that, for example, a steel having a relatively low Cu sensitivity is produced for the purpose of washing in a kettle after the Cu-added steel is produced. Therefore, the Cu content must be reduced as much as possible as an inevitable impurity, and the upper limit is regulated to 0.25%.
Ｓ：０．００２％以下、Ｏ：０．００１５％以下、Ｎ：０．０１％以下
ＳはＭｎ、ＯはＳｉやＡｌなど、ＮはＡｌなどと結合して非金属介在物を形成する。これらは、鏡面研磨時に脱落してピンホール欠陥の原因になりうるため、鏡面性を高める上での障害となる。また、腐食環境下での錆の起点ともなりうる。これらの理由から、上記した非金属介在物はできるだけ少なくするのが望ましく、そのためには、Ｓ、Ｏ、Ｎの含有量を極力低減させることが必要である。このため、Ｓ、Ｏ、Ｎの上限は、それぞれ０．００２％、０．００１５％、０．０１％とする。
S: 0.002% or less, O: 0.0015% or less, N: 0.01% or less S is Mn, O is Si or Al, N is bonded to Al or the like to form non-metallic inclusions. Since these may fall off during mirror polishing and cause pinhole defects, they become an obstacle to improving the mirror surface. It can also be a starting point for rust in corrosive environments. For these reasons, it is desirable to reduce the above-described nonmetallic inclusions as much as possible. To that end, it is necessary to reduce the contents of S, O, and N as much as possible. For this reason, the upper limits of S, O, and N are set to 0.002%, 0.0015%, and 0.01%, respectively.
Ｍｏ＋１／２Ｗ：０．４％〜１．５％
ＭｏとＷは、溶体化処理後の冷却時あるいは時効処理時に微細な炭化物を形成し、硬さ向上の役割を果たすが、過剰に添加すると靱性の低下をもたらすことから、上限及び下限を定めることが必要である。ここでＷは、Ｍｏに対して質量％でほぼ倍の量で同様の効果が認められることから、Ｍｏ＋１／２Ｗの計算式で、下限を０．４％、上限を１．５％に規制する。なお、上記と同様の理由で下限を０．５％、上限を１．０％とするのが望ましい。
Mo + 1 / 2W: 0.4% to 1.5%
Mo and W form fine carbides at the time of cooling or aging treatment after solution treatment, and play a role in improving hardness, but if added excessively, the toughness is reduced, so an upper limit and a lower limit are determined. is necessary. Here, since W has the same effect as Mo in mass% with respect to Mo, the same effect is recognized, so the lower limit is regulated to 0.4% and the upper limit is regulated to 1.5% in the formula of Mo + 1 / 2W. . For the same reason as described above, it is desirable to set the lower limit to 0.5% and the upper limit to 1.0%.
Ｖ：０．３％以下
Ｖは焼戻し軟化抵抗性を高めるとともに、硬質の炭化物を微細に形成して耐磨耗性を向上させる効果があるので所望により含有させることができる。ただし、多すぎると金型加工時の工具の摩耗を増加させるとともに、多量の炭化物の析出による靱性低下を招くので、０．３％以下とする。
V: 0.3% or less V increases the resistance to temper softening and has the effect of finely forming hard carbides to improve wear resistance, so V can be contained as desired. However, if the amount is too large, the wear of the tool during die processing is increased and the toughness is reduced due to the precipitation of a large amount of carbides.
次に、本発明でＭ２３Ｃ６型のＣｒ系炭化物粒子の平均粒径を限定した理由を以下に述べる。
本発明では、析出強化を目的としてＭ２３Ｃ６型のＣｒ系炭化物を析出させているが、析出粒子が微細なほど硬化作用が得られることから、等価円直径は７０ｎｍ以下が望ましく、より望ましくは５０ｎｍ以下とする。ただし、炭化物粒子の過度の微細化には体積分率の減少が伴い、これによる硬さの低下が避けられないことから、粒子径の下限値を２ｎｍとするのが望ましい。
Next, the reason why the average particle size of the M 23 C 6 type Cr-based carbide particles is limited in the present invention will be described below.
In the present invention, M 23 C 6 type Cr carbide is precipitated for the purpose of precipitation strengthening. However, the finer the precipitated particles are, the harder the action is, so the equivalent circular diameter is desirably 70 nm or less, more desirably. Is 50 nm or less. However, excessive refinement of the carbide particles is accompanied by a decrease in volume fraction, and a decrease in hardness due to this is unavoidable, so the lower limit of the particle diameter is preferably 2 nm.
また、本発明では、Ｍｓ点が４２０℃以上であるのが望ましい。Ｍｓ点を高めることで、固溶化後の下げ切り温度を向上させることができ、効率的な熱処理工程が可能となる効果がある。 In the present invention, the Ms point is desirably 420 ° C. or higher. By raising the Ms point, the cut-off temperature after solid solution can be improved, and an efficient heat treatment process is possible.
また、本発明の製造方法では、固溶化処理を行った後、４００℃〜５５０℃で時効処理を行うことで、等価円直径７０ｎｍ以下の微細なＭ２３Ｃ６型Ｃｒ系炭化物の析出を硬さ向上手段として利用するため、ＮｉＡｌの析出を利用しない組織設計が可能となり、その結果、希少金属であるＮｉの低減が可能となる。さらに、これらの結果生じるＭｓ点の向上及び析出温度の低下によって、固溶化後の下げ切り温度及び時効温度をそれぞれ向上及び低下させる。 Further, in the production method of the present invention, after the solution treatment, the aging treatment is performed at 400 ° C. to 550 ° C. to harden the precipitation of fine M 23 C 6 type Cr carbide having an equivalent circular diameter of 70 nm or less. Since it is used as an improvement means, it is possible to design a structure without using NiAl precipitation, and as a result, it is possible to reduce Ni which is a rare metal. Furthermore, the lowering temperature and the aging temperature after the solid solution are improved and lowered by the improvement of the Ms point and the reduction of the precipitation temperature, which are caused as a result of these.
以上説明したように、本発明では、微細なＭ２３Ｃ６型Ｃｒ系炭化物の析出を硬さ向上手段として利用するため、ＮｉＡｌの析出を利用しない組織設計が可能となり、その結果、希少金属であるＮｉの低減が可能となる。さらに、Ｍｓ点の向上及び析出温度の低下によって、効率的な熱処理工程が可能となる効果がある。 As described above, in the present invention, since the precipitation of fine M 23 C 6 type Cr-based carbide is used as a means for improving hardness, it is possible to design a structure that does not use NiAl precipitation. Some Ni can be reduced. Furthermore, there is an effect that an efficient heat treatment process is possible by improving the Ms point and lowering the deposition temperature.
本発明の金型鋼は常法により溶製することができるが、Ｓ、Ｏ、Ｎを厳格に規制するという点では、エレクトロスラグ再溶解法を採用するのが望ましい。また、エレクトロスラグ再溶解法では、厳密な組織が得られるために、この点からも鏡面性に対して有利である。該溶解法では、任意のエレクトロスラグ再溶解鋳塊が得られるように成分設計した電極を用いて溶製される。
好適には、エレクトロスラグ再溶解法により溶製された鋳塊は必要に応じて鍛造などの加工を施し、さらに熱処理を行う。
Although the mold steel of the present invention can be melted by a conventional method, it is desirable to adopt an electroslag remelting method in terms of strictly controlling S, O, and N. In addition, the electroslag remelting method is advantageous in terms of specularity because a precise structure can be obtained. In the melting method, melting is performed using an electrode whose components are designed so that an arbitrary electroslag remelting ingot is obtained.
Preferably, the ingot made by the electroslag remelting method is subjected to processing such as forging as necessary and further subjected to heat treatment.
熱処理工程では、固溶化処理及び時効処理を行う。
固溶化処理は、８５０〜１３００℃に加熱して行うことができる。時効処理温度はＭ２３Ｃ６型Ｃｒ系炭化物による析出強化を図るため、４００℃〜５５０℃とするのが望ましい。時効処理の時間は特に限定されるものではないが、５〜１５時間を例示することができ、冷却は、１０℃／時間以上の冷却速度で行うのが望ましい。
上記した熱処理によりプリハードンされた金型鋼は、良好な鏡面研磨性や耐食性、靱性を示し、かつＮｉ量の低減及び熱処理工程の効率化を可能とする。
In the heat treatment step, a solution treatment and an aging treatment are performed.
The solution treatment can be performed by heating to 850 to 1300 ° C. The aging treatment temperature is preferably 400 ° C. to 550 ° C. in order to enhance precipitation strengthening by the M 23 C 6 type Cr-based carbide. Although the time of an aging treatment is not specifically limited, 5 to 15 hours can be illustrated, and cooling is desirably performed at a cooling rate of 10 ° C./hour or more.
The mold steel pre-hardened by the heat treatment described above exhibits good mirror polishability, corrosion resistance, and toughness, and can reduce the amount of Ni and increase the efficiency of the heat treatment process.
本発明の実施例を以下に説明する。
表１に、供試材として用意した本発明の成分範囲になる発明鋼と、本発明の成分範囲を外れた比較鋼の化学成分（残部Ｆｅおよびその他の不可避不純物）を示す。
極低Ｓ化を実現するため、鋳塊製造過程においてエレクトロスラグ再溶解法を用いた。鋳塊溶製後、鍛造により所定寸法への加工を行い、焼ならし、溶体化、時効処理を行い、硬さを約４０ＨＲＣに調整した。
その際の溶体化処理条件は９５０℃×４時間とした。また、上述の熱処理を行った試料の硬さ及びシャルピー衝撃試験の結果も表１に示した。シャルピー衝撃試験の際は、ＪＩＳ Ｚ ２２４２で規定されているノッチ深さ２ｍｍのＵノッチ試験片を用い、室温にて試験を実施した。
Examples of the present invention will be described below.
Table 1 shows the chemical composition (remainder Fe and other unavoidable impurities) of the inventive steel prepared as the test material, which falls within the component range of the present invention, and the comparative steel outside the component range of the present invention.
In order to realize extremely low S, an electroslag remelting method was used in the ingot manufacturing process. After the ingot was melted, it was processed into a predetermined size by forging, normalized, solutionized, and subjected to aging treatment, and the hardness was adjusted to about 40 HRC.
The solution treatment conditions at that time were 950 ° C. × 4 hours. Table 1 also shows the hardness of the sample subjected to the above heat treatment and the result of the Charpy impact test. In the Charpy impact test, a U-notch test piece having a notch depth of 2 mm defined in JIS Z 2242 was used, and the test was performed at room temperature.
上記供試材より試験片を採取し、以下に記す各種特性を調査した。
得られた供試材のうち、発明鋼１と比較鋼１について、Ｍｓ点とＭｆ点とを測定し、その結果を図１に示した。その結果から分かるように、オーステナイト安定化元素であるＮｉの低減によって発明鋼のＭｓ点およびＭｆ点はともに比較鋼１のそれより３０℃向上した。
Test pieces were sampled from the above test materials, and various properties described below were investigated.
Among the obtained test materials, Ms point and Mf point were measured for Invention Steel 1 and Comparative Steel 1, and the results are shown in FIG. As can be seen from the results, both the Ms point and the Mf point of the inventive steel were improved by 30 ° C. from those of the comparative steel 1 due to the reduction of Ni as an austenite stabilizing element.
次に時効温度を、固溶化まま、２００℃、３００℃、４００℃、４５０℃、５００℃、５５０℃、６００℃で変えて、ロックウェルＣスケール硬さを測定し、図２の測定結果を示した。その結果、比較鋼１および２においては、少なくとも４５０〜５００℃の時効によって目標硬さ上限を超えるため、５５０℃程度で時効する必要があるが、発明鋼１は４００〜５００℃で目標硬さを満たしており、より低温の時効によって目標硬さが得られることが確認された。 Next, the aging temperature was changed to 200 ° C., 300 ° C., 400 ° C., 450 ° C., 500 ° C., 550 ° C., and 600 ° C. while measuring the Rockwell C scale hardness, and the measurement results of FIG. Indicated. As a result, in comparative steels 1 and 2, the upper limit of the target hardness is exceeded by aging at least 450 to 500 ° C., and therefore it is necessary to age at about 550 ° C., but inventive steel 1 has a target hardness of 400 to 500 ° C. It was confirmed that the target hardness was obtained by aging at a lower temperature.
発明鋼１について、日本電子株式会社製のＴＥＭ（透過型電子顕微鏡）の明視野像を撮影し、図３に示した。
図３から明らかなように、等価円直径２０〜３０ｎｍ程度のＭ２３Ｃ６型Ｃｒ炭化物が母相中に析出していることが確認された。
For inventive steel 1, a bright field image of a TEM (transmission electron microscope) manufactured by JEOL Ltd. was photographed and shown in FIG.
As apparent from FIG. 3, it was confirmed that M 23 C 6 type Cr carbide having an equivalent circular diameter of about 20 to 30 nm was precipitated in the matrix.
また、時効温度及び時間を変化させることにより、Ｍ２３Ｃ６型のＣｒ系炭化物の平均炭化物粒子径を変え、その際のロックウェルＣスケール硬さを測定し、その結果を図４に示した。平均炭化物粒子径は、前記ＴＥＭ装置で測定した明視野像面積を画像解析ソフトにより測定し、同一の面積となる円の直径を算出して求めた。
図４から分かるように、Ｍ２３Ｃ６型のＣｒ系炭化物の平均粒子径を７０ｎｍ以下にすることで、目標硬さ３７〜４２ＨＲＣが得られた。また、５０ｎｍ以下にすることで４０ＨＲＣ程度に調整可能であることが確認された。
Further, by changing the aging temperature and time, the average carbide particle diameter of the M 23 C 6 type Cr-based carbide was changed, and the Rockwell C scale hardness at that time was measured, and the result is shown in FIG. . The average carbide particle diameter was obtained by measuring the bright field image area measured by the TEM apparatus with image analysis software and calculating the diameter of a circle having the same area.
As can be seen from FIG. 4, the target hardness of 37 to 42 HRC was obtained by setting the average particle diameter of the M 23 C 6 type Cr carbide to 70 nm or less. Moreover, it was confirmed that adjustment to about 40 HRC was possible by setting the thickness to 50 nm or less.
以上、本発明について上記実施形態に基づいて説明を行ったが、本発明の範囲を逸脱しない限りは適宜の変更が可能であり、その変更した内容は本発明の範囲内である。 As mentioned above, although this invention was demonstrated based on the said embodiment, unless it deviates from the scope of the present invention, an appropriate change is possible and the changed content is in the scope of the present invention.
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| CN113444867B (en) * | 2021-06-30 | 2022-09-20 | 江苏省沙钢钢铁研究院有限公司 | Production method of plastic die steel plate and plastic die steel plate |
| CN113528971A (en) * | 2021-07-21 | 2021-10-22 | 攀钢集团江油长城特殊钢有限公司 | Hot work die steel and preparation method thereof |
| CN115354228A (en) * | 2022-08-29 | 2022-11-18 | 山东钢铁集团日照有限公司 | Production method of high-uniformity pre-hardened plastic die steel |
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