巻号一覧
78 巻, 4 号
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論説
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清水 崇行, 井上 幸一郎2007 年 78 巻 4 号 p. 289-290
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーThe influence of coarse carbide volume on anisotropy of dimensional change at heat treatment of cold working die steels has been investigated. The influence of carbide shape on anisotropy has been estimated by FEM analysis using very simplified models that contained carbide. Dimensional change increases with increasing carbon content of martensite. Anisotropy isn't affected by carbon content and phase transformation in this experiment. On the other hand, volume of large primary carbides affects anisotropy ; a parallel direction in forging direction is longer than vertical direction. By FEM analysis, Anisotropy is generated including the carbide. The length of test piece increases with increasing aspect ratio of carbide. The result of anisotropy by FEM analysis at a large aspect ratio is same as the experiment result.抄録全体を表示PDF形式でダウンロード (1100K) -
五味 伸幸, 塩田 哲郎, 森川 秀人2007 年 78 巻 4 号 p. 299-306
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーMiddle carbon 5Cr-1Mo-V type steels such as SKD61 and AISI H13 have been widely and globally used for hot working applications from die casting to forging. As for V, although 1 % V steels are popular, 0.5 % V steels have been applied as well. In these 20 years, low Si and high Mo type steels have been developed and evaluated as high performance steels mainly for die casting fields. In forging applications, however, the effect of Si has not been fully clarified. Therefore, the steel with 0.06Si and 0.55V has been studied to make it clear the effect of Si and V on wear resistance and toughness especially in hot forging tools. The results obtained are as follows. (1) Softening resistance is almost the same in both steels of A and SKD61. The hardness of these steels tempered at 873 K and 973 K for 3.6 ks is 44 and 30 HRC, respectively. In spite of lower hardness, steel A with 49.5 HRC shows 28 % less wear than SKD61 with 52.7 HRC. Oxide film of steel A is thicker than that of SKD61. (2) The friction coefficient, μ, in metal-metal contact condition is approximately 0.7. In oxide film-metal contact condition, on the other hand, μ reduces to smaller than 0.35. Steel A shows lower μ value than SKD61 at the all oxidation temperature ranges. (3) In high temperature oxidized specimen, the higher contact pressure Pmax, the higher μ value. With Pmax less than 20 MPa, μ of SKD61 is much more sensitive to Pmax than that of steel A. The oxidized surface of steel A with small μ is hardly worn away without the adhesion of worn dust. (4) Charpy impact value of steel A is remarkably improved, which is caused by the suppress of coarse primary carbides sized 10 to 30 μm by reducing Si and V contents.抄録全体を表示PDF形式でダウンロード (1062K) -
平岡 泰, 井上 幸一郎2007 年 78 巻 4 号 p. 307-314
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーNitriding is widely applied to hot-work tool steel to improve the thermal fatigue, corrosion, and tribological properties. For improvement in life of hot-work tool steel, it is important to give the optimal thickness of compound layer and diffusion zone. Therefore, influenc of alloying elements on nitrogen concentration distribution in diffusion layer after nitrocarburiding was investigated in this study. Steels that added silicon, nickel, chromium, molybdenum, vanadium, tungsten and cobalt based on JIS-S40C were nitrocuarburized at 823 K for 18 ks. After this, the nitrogen concentration of these steels were mesured. The diffusion simulation that considered kinetics of nitride precipitation was examined, and the influence of the alloy element was arranged by reactive speed constant K that decided the generation speed of nitride. This simulation can forecast the nitrogen concentration distribution in the diffusion layer after nitrocarburiding at the nitriding temperature and the time in hot-work tool steel.抄録全体を表示PDF形式でダウンロード (715K) -
横井 直樹, 平岡 泰, 井上 幸一郎2007 年 78 巻 4 号 p. 315-322
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーNitriding, which includes nitrocarburizing, is the most popular surface treatment in order to prolong durability of hot working die steels. However, it has not been elucidated that either precipitation hardening or solid solution hardening caused the hardening mechanism of the nitriding. In this work, the morphology of nitrogen in a diffusion layer of Fe-C-Si-Mn-Cr in a practical nitrocarburizing condition was investigated by transmission electron microscopy and X-ray diffraction in order to elucidate the influence of Cr on the hardening mechanism in the nitrocarburizing. In the diffusion layer of the nitrocarburized specimens, precipitation of CrN was identified regardless of the amount of Cr contents. The crystal structure of CrN was confirmed as a cubic B1 type and has Baker-Nutting orientation relationship with martensite. Besides, the lattice constant of martensite in the diffusion layer measured by X-ray diffraction was still similar to that of the unnitrided zone. Those results show that the major contribution of nitrogen to the hardening in the diffusion layer is precipitation hardening as CrN, and the contribution to the solid solution hardening is small. And increasing Cr contents enhanced the CrN precipitation and the hardness of the diffusion layer, although the diffusion layer shrank.抄録全体を表示PDF形式でダウンロード (777K)
解説
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蓮野 昭人2007 年 78 巻 4 号 p. 323-329
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーThe demand of quality improvement and reduction in costs from the user of die casting products increases every year. And, in order to fulfill the requirement, new technologies are developed as follows; (1) The high vacuum process reduces the gas content in the die castings and enables the welding of die cast products. (2) The high speed casting process enables larger and thinner product. (3) New die lubricant technique and optimization of cooling by CAE contributes to productivity improvement. On the other hand, these new technologies might give the die serious damages. Further cooperation of related manufacturers is necessary and indispensable for a further improvement in the future.抄録全体を表示PDF形式でダウンロード (895K) -
小森 誠2007 年 78 巻 4 号 p. 331-340
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーThe life time of warm-hot forging die recently tends to become shorter though it's originally very short comparing with that of other material processing. It is big impact, therefore, on productivity, economy and earth environment to improve die life. To improve die life, we have to make sure its reason and to consider its dispersion. We also have to make sure its damage mode in case it causes life out. We should examine rather life total cost in economical study and consider die material resource circulation for earth environment. From the points to reduce die life total cost and to consider resource circulation, we build up a base of "no-break-die" by optimizing die material and its heat treatment, and then prolong the die life by applying surface modification or partially reinforcing with special materials. It becomes more important to challenge boldly difficult technical subjects with cross-fuctional collaboration of various brains not only from persons concerned in die industry but also from other fields.抄録全体を表示PDF形式でダウンロード (755K)
技術資料
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北川 利博, 小林 喜一2007 年 78 巻 4 号 p. 341-346
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーThe purpose of aluminum die casters is to supply low cost and high quality products. It is necessary to shorten a cycle in production time. Therefore, die lubricant is more strongly sprayed from die surface to solidify a product fast. However, higher cycle die casting is occurred various problems such as heat-checking or soldering on die surface. This reason is that temperature amplitude of die surface is increasing. Amicoat is new multi layer PVD coating which was developed to solve these problems. Amicoat has two kinds of Amicoat-H and Amicoat-D. Amicaot-H suppresses heat-checking and corrosion / erosion more effectively than conventional PVD coatings or nitriding. On the other hand Amicoat-D has excellent soldering resistance. When core pin coated Amicoat-D, the life was improved two or three times compared to conventional PVD coatings.抄録全体を表示PDF形式でダウンロード (575K) -
河野 正道, 井上 幸一郎2007 年 78 巻 4 号 p. 347-352
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーThe strongly commercial interests have been focused on hot working die steels with improved hardenability to attain higher impact value and ensure adequate dies life even in the larger mass blocks. Hardenability, avoiding pearlite transformation and attain a finer bainitic microstructure, is quite important on quenching of large die blocks. In addition strength of die is essential to improve sensitivity for ware at elevated temperature. In this paper, several properties such as hardnenability, inpact value, fracture toughness and high temperature strength of newly developed hot working die steel 'DH31-SS1' will be represented. The given results by comparing with conventional hot working die steel DHA1-ES (corresponding to AISI H13) are as follows. (1) Retarded quenched material has finer bainitic microstructure and superior impact value of 30 J/cm2. (2) Stress of resistance to deform at 973 K after short time holding is higher from 100 MPa upto 150 MPa. (3) Fracture toughness on high hardness is same but on low hardness, inferior.抄録全体を表示PDF形式でダウンロード (746K) -
中濱 俊介, 清水 崇行2007 年 78 巻 4 号 p. 353-360
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリー'DRM series' is new matrix type high speed steel. It is composed of three steels 'DRM1, DRM2, DRM3' which are used with the maximum hardness 58, 62 and 66 HRC, respectively. These steels are characterized by their more finely dispersed carbides free from coarse primary ones, higher fatigue strength and toughness than conventional steels. Molds which are used for precision forging on high hardness have the problems of the small crack. Application of DRM steels showed the effect to the life improvement of the mold with this problem. The greatest reason of longer mold life was higher fatigue strength which is the feature of DRM steels. The DRM steels have shown longer life mainly in forging tools of automobile and machinery components. They are further expected to expand their application fields.抄録全体を表示PDF形式でダウンロード (853K) -
井ノ口 貴之2007 年 78 巻 4 号 p. 361-368
発行日: 2007/11/29
公開日: 2008/05/29
ジャーナル フリーMirror polishability is one of the most important properties of the plastic injection mold for making transparent or mirror surface products. Mirror surfaces are to be free from pinholes and undulation. Pinhole is a kind of small pit which appears during polishing process. Although the effects of metallurgical factors such as microstructure, hardness, cleanliness on pinhole susceptibility have been studied, the actual forming mechanism of pinholes has not been fully clarified. To make it clear this mechanism current injection mold steels have been studied by observing actually polished surfaces with gradually refining polishing media. The results obtained are as follows. (1) Soft non-metaric inclusions such as sulfides cause pinholes by beeing ground preferentially. Hard particles:nitrides, oxides and carbides, on the other hand, form pinholes by dropping themselves off. (2) Pinhole shape depends on the type of particles. Shallow and wide for soft inclusions and deep and narrow for hard patricles. (3) In case of large polishing grits, pinholes hardly appear whether they are in the manner of preferential grinding or peeling off. Small grits, however, increases the number of pinholes. (4) When grit size is close to those of particles, hard inclusions and carbides tend to drop off easily. (5) When hard inclusions are distributed together with soft ones, they drop off easier than solely distributed.抄録全体を表示PDF形式でダウンロード (1061K)
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