著者

黒木 英憲 徳永 洋一

出版者

Japan Society of Powder and Powder Metallurgy

雑誌

粉体および粉末冶金 (ISSN:05328799)

巻号頁・発行日

vol.20, no.2, pp.49-54, 1973-06-25 (Released:2009-05-22)

参考文献数

10

---

Impact strength of iron compacts, prepared from commercial powders by single compacting under the pressure of 2-9 t/cm2 and by sintering in hydrogen at the temperature range of 1100-1300°C for less than 1 hr, did not simply increase with densification at room temperature, but decreased in the density range around 7 g/cm3.Three different mechanisms for the observed phenomena of abnormal brittleness were considered.First, a shear crack could propagate through large flaky pores formed by the removal of pressed powder lubricants between iron particles. This type of brittleness disappeared after the elimination of flaky pores by sintering at higher temperatures for longer periods.Second, an abnormal growth of ferritic grains could cause an increase of ductile-brittle transition temperature, together with the increase of porosity on grain boundary. This type of brittleness was the same as previously observed by the authors on double pressed materials, and it became remarkable with the progress of sintering.Third, when the ductile-brittle transition occurred above room temperature, the impact strength of high density (above 7 g/cm3) sintered irons could become lower than that of lower density ones at room temperature, because the transition appeared more evidently with densification.

著者

篠崎 賢二 羅 湘軍 有吉 秀文 黒木 英憲 白井 誠

出版者

社団法人溶接学会

雑誌

溶接学会論文集 : quarterly journal of the Japan Welding Society (ISSN:02884771)

巻号頁・発行日

vol.17, no.2, pp.286-293, 1999-05-05

被引用文献数

11

---

This study was carried out quantitatively to evaluate the hot cracking susceptibilities of various Ni-base superalloys and the effect of grain size on hot cracking susceptibility during laser welding. Ni-base superalloys used were Inconel 718,Inconel X-750,Inconel 617,Inconel 625,Nimonic 90 Waspaloy, Hastelloy X. The grain size of Inconel 718 varied from about 10 to 110 μm. In this study, the hot craking susceptibility was evaluated by a modified U-type hot cracking tester during CO_2 laser welding. Samples were solution heat-treated before welding and welded with laser powers of 3 and 5 kW and with a traveling speed of 0.5 to 3 m/min. The hot cracking occurring in the weldment during the bead on plate test was reproduced on the U-type hot cracking test. Consequently, the liquation cracking susceptibilities of various Ni-base superalloys decreased in the order of Waspaloy, Inconel 617,Inconel 718,Hastelloy X, Inonel 625,Inconel X-750 and Nimonic 90. Liquation cracking susceptibility of Inconel 718 increased with an increase in grain size.