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Study on Diffusion Bonding of Cast Irons

铸铁扩散连接研究

基本信息

批准号：
63550551
负责人：
NISHIO Kazumasa
金额：
$ 1.28万
依托单位：
Kyushu Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63550551/
关键词：
Diffusion bonding Spheroidal graphite cast iron Toughness Number of graphite Torsion insert metal Charpy impact test S - N curve 衝撃試験ねじり黒鉛の析出インサート金属吸収エネルギ異材接合

项目摘要

Spheroidal graphite cast irons which are a very difficult material to fusion weld were diffusion bonded. The joints were fabricated with Ni foil as an insert metal or without it at 820, 900 and 950 ﾟC for 1.8 ks. And then they were annealed to ferritize the cast iron matrix at 720 ﾟC for 10.8 ks. Impact and torsion characteristics of the diffusion bonds have been investigated. Main results obtained are as follows.(1) The bond toughness of the joints directly bonded was very low due to much precipitation of graphites at the bond interface. When the cast irons were bonded with Ni foil as an insert metal, however, the bond toughness was strongly improved. The absorbed energy of the joints with Ni foil of 50 mu m in thickness was nearly the same as that of the base metal.(2) The absorbed energy of joints of cast irons with lower number of graphite particles, the cast irons were directly bonded, decreased with an increase in bonding temperature. When the number of graphite particles was more than 250 particles/mm^2 in the cast iron, however, the absorbed energy of the joints increased with the increase in bonding temperature. This is considered as follow. As the ferritizing speed of the cast iron increased with an increase in number of graphite particles, precipitation of graphites during the ferritizing was mainly developed on the graphite particles in the cast iron rather than at the bond interface. As a result, the bond toughness was improved by a decrease of precipitation of graphite at the bond interface.(3) When the cast iron joints directly bonded were torsion tested, and endurance of the torsion fatigue was largely scattered at the same stress. This is due to the precipitation of graphites at the bond interface. The endurance of the joints with Ni foil of 10 mu m in thickness was hardly scattered, and the fatigue limit was 160 MPa.

采用扩散焊方法对难以熔焊的球墨铸铁进行了焊接。在820 ℃、900 ℃和950 ℃下，用Ni箔作为插入金属或不使用Ni箔，进行1.8 ks的焊接。然后在720 ℃退火10.8ks使铸铁基体铁素体化。研究了扩散连接的冲击和扭转特性。主要结果如下。(1)直接连接接头的结合韧性很低，这是由于在结合界面处有大量的石墨析出。然而，当铸铁与Ni箔作为插入金属结合时，结合韧性显著提高。用50 μ m厚的Ni箔焊接的接头吸收的能量与母材几乎相同。(2)石墨颗粒数较少的铸铁，即直接连接的铸铁，其接头吸收能量随连接温度的升高而降低。然而，当铸铁中石墨颗粒的数量大于250个/mm^2时，接头的吸收能量随着接合温度的升高而增加。这被认为是如下。随着石墨颗粒数量的增加，铸铁的铁素体化速度增加，铁素体化过程中石墨的析出主要发生在铸铁中的石墨颗粒上，而不是在结合界面处。结果表明，粘结界面处石墨的析出减少，从而提高了粘结韧性。(3)对直接连接的铸铁接头进行扭转疲劳试验时，在相同应力下扭转疲劳寿命分散较大。这是由于石墨在结合界面处沉淀。用10 μ m厚的Ni箔焊接的接头的疲劳强度几乎不分散，疲劳极限为160 MPa。