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Volume 76 (2005)
- Issue 4 Pages 229-
- Issue 3 Pages 159-
- Issue 2 Pages 79-
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Volume 76, Issue 4
Displaying 1-8 of 8 articles from this issue
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Takayuki Shimizu, Kozo Ozaki2005 Volume 76 Issue 4 Pages 229-240
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSThe influence of carbide volume and size on endmilling machinability of cold working die steels have been investigated. The volume of large primary carbide (M7C3) and small spheroidal carbide (M23C6,M7C3 and M6C) is controlled by carbon and chromium content.
The results are as follows.
(1)Tool life of endmilling is prolonged by decreasing carbide volume. It is affected by carbide size ; large primary carbide is more effective than small spheroidal carbide.
(2)Cutting force FR and frictional force F are not affected by carbide volume and size at early stage of cutting (cutting length=0.2 m). On the other hand, FR and F increase with increasing carbide volume at finally stage (maximum width of flank wear is 500 μm). Large primary carbide is drastically increased both FR and F more than small spheroidal carbide.
(3)The types of wear are the abrasive wear at tool edge and th e adhesive wear at clearance face. Volume of abrasive wear increases with increasing carbide volume. Large primary carbide remarkably increases the volume of abrasive wear more than small spheroidal carbide.
(4)The changes in FR and F are due to volume of abrasive wear at tool edge. Volume of adhesive wear at clearance face can be estimated by frictional force F and cutting length.View full abstractDownload PDF (247K) -
Motohiro Ibuki, Kozo Ozaki2005 Volume 76 Issue 4 Pages 241-248
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSHigh vacuum die-casting process and low speed die-casting process are used in these days. These die-casting processes need high projection speed or high temperature molten Al alloy. So dissolution of steels in molten Al alloy becomes important. The purpose of this study is to reveal the effect of carbide volume fraction and carbide type on dissolution of steels in molten Al alloy. In the dissolution test, specimen immerse in molten Al alloy. The results are as follows.
1) Dissolution weight was nearly equal to cabide fraction and carbide type with no rotation in the dissolution test.
2) Dissolution weight was decresed with increase of carbide fraction. Dissolution weight was not related to carbide type.
3) There are two reasons for effect of carbide on dissolution weight. One is that increase of carbide volume fraction affects decrease of iron diffusion flux in molten Al alloy. Another is that increase of carbide volume fraction increase of molten Al alloy viscosity coefficient.
4) It is necessary to consider the laminor flow and turbulent flow for the diffusion control of Fe in molten Al alloy.View full abstractDownload PDF (165K) -
Kozo Ozaki2005 Volume 76 Issue 4 Pages 249-257
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSThe effect of distribution of primary carbides on fatigue strength has not been fully clarified for cold work die steels. Eight percent Cr type steel and JIS SKD11 have been studied by changing carbides area fraction. We have tested low cycle fatigue properties and discussed with comparing tensile properties and microfractographs. The test results are summarized as follows.
1) Tensile strength of 8Cr type steel and JIS-SKD11 is decreased by increasing carbide area fraction. But σ0.2 and σ0.02 is same in tested steels. independent to carbide area fraction.
2) Fatigue strength is decreased by increasing carbide area fraction and fatigue strength of 8Cr type cold die steel is higher than that of JIS-SKD11.
3) Fatigue crack is initiated from primary carbide in all specimens.
4) Fatigue life is determined by initiation life of fatigue crack in these cold work die steels.
5) Small crack is initiated at primary carbide in early stage of fatigue test and this small crack is connected to neighborhood carbide, finally this crack changes to propagation mode of fatigue phenomena.View full abstractDownload PDF (185K)
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Yukinori Matsuda2005 Volume 76 Issue 4 Pages 259-267
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSThe trend of the development of recent die and mold steels has been reviewed.
With increase in the transplant of automobiles and automotive-parts production to Asian nations, mainland China, especially, high and stable quality die and mold steels have been developed.
Among them are aluminum die-casting die steels to meet the severe users' requirements such as recommended by NADCA.
High strength steel sheets and high strength aluminum alloys being applied to automotive parts for weight reduction, furthermore, high strength cold work die steels are urgently demanded together with surface coating to stand high applied load and wearing conditons.
Moreover, near net shaped high precision forming technology in warm and cold forging has improved.
To meet these technology, new matrix type high speed steels for forging dies have been developed. Theses grades are characterized by their finely dispersed carbides free from coarse primary carbides and contirbute to prolonged die life.
I n the field of plastic injection molds, to meet the main requirement such as precision and super mirror polishing, wide variety new grades have been developed too.View full abstractDownload PDF (153K) -
Kazuki Kawata2005 Volume 76 Issue 4 Pages 269-277
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSThe trend of recent surface treatment technology is reviewed. Various kinds of hard coating processes such as TRD, CVD, PVD and PCVD have been applied to dies and molds. As a recent trend of the surface treatment technology for dies and molds, a low-temperature process has been desired from a viewpoint of deformation and change in dimension, and a coating process for dies and molds of complicated geometry has become important. Furthermore, the duplex process (diffusion-hardening treatment + hard coating) has been used for prolongation of dies and molds lives.
The PCVD process has good film adhesion and good throwing power at low temperatures, and it can perform the duplex process continuously. Consequently, the PCVD process has been widely applied to dies and molds. It is expected that the nano-composite films of TiAlSiCNO system and the DLC films by the PCVD realize lubricant-free cold pressing and cold forging and lubricant-less warm and hot working.View full abstractDownload PDF (111K)
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Shunsuke Nakahama, Yukinori Matsuda, Kunio Namiki, Kozo Ozaki2005 Volume 76 Issue 4 Pages 279-286
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSThe best way to attain high toughness in high carbon-high hard tool steels is to refine carbides. Besides powder metallurgy, carbides control by alloy designing and production process is the key technology. This time we have developed three matrix type high speed steels, DRM steels, and have clarified their superiority to conventional type steels not only in fundamental study but in practical use.
This series are composed of three steels DRM1 to 3 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 toughness and fatigue strength than conventional type steels. DRM1 is mainly used for hot and warm forging tools with the hardness 56 to 58 HRC. DRM2 is applied to warm and cold forging tools with a higher hardness 58 to 62 HRC. DRM3, the highest hardness one, is the best grade for cold toolings.
These DRM steels have shown longer life and contributed to total cost reduction mainly in forging tools of automobile and machinery components. They are further expected to expand their application fields.View full abstractDownload PDF (236K) -
Koichiro Inoue, Takashi Ofuji, Yuji Ichioka, Toshihiko Araki2005 Volume 76 Issue 4 Pages 287-292
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSLong life die casting die steels have been required to reduce die cast product cost. The main life limiting factor is premature failure. To obtain higher fracture resistance, high reliable hot work die steel, "DHA1-ES", has been developed. Generally, crack susceptibility is estimated by the Charpy impact value. It is cleared that clean and homogenized steel shows higher Charpy impact value. To improve the toughness the manufacturing process of this steel is optimized such as melting, forging and heat treatment. Though DHA1-ES has the same compositions as those of JIS SKD61, its Charpy impact values, dispersion and anisotropy are improved remarkably. Furthermore, low cycle fatigue life of this grage is longer than JIS-SKD61. It is expected that DHA1-ES is widely used in die casting industry with high reliability.View full abstractDownload PDF (208K) -
Masamichi Kawano2005 Volume 76 Issue 4 Pages 293-298
Published: November 15, 2005
Released on J-STAGE: April 19, 2010
JOURNAL FREE ACCESSThe strongly commercial interests have been focused on avoid distortion and attain higher toughness of quenched JIS SKD61 die block. FE (Finite Element) analyses before practical trials that can visualize local distribution of temperature or stress are available to complete these requests. In order to establish the basics of simulation technique, stress-strain behavior is derived from tensile tests and also boundary condition data is generated through quenching tests in compressed N2 gas. It's obvious that the elastic/plastic boundary stress which to be treated as yield point in FE analyses is from 35 to 80 % for 0.2 % proof stress. And the influence of gas pressure P on heat transfer coefficient h is defined for material surface temperature. Given h is approximately 250 W/m2/K for P equals to 4700 torr. Then the validity of database is verified on quenching of die-block-like two types of 4 kg work-pieces. Predicted transformation temperature is agreed well with that in experiments. And also the tendency of change in work-piece size is represented by FE analyses. Moreover the difference of distortion between shapes of work-pieces during quenching is shown. These results suggest that the recommended process could be designed for each die shape and it's expected through numerical simulation.View full abstractDownload PDF (204K)
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