辊弯成型异型管角部硬度变形规律的研究

通过对冷弯成型异型管角部的研究,分析总结出其变形规律。在生产异型管时,角部的变形量大,加工硬化所产生硬度普遍高于平直部,而且对同一部位总的趋势为:内层硬度外层硬度中心层硬度。角部在变形大时易产生应力集中现象,有时存在裂纹倾向。为避免加工过程中产生不利因素,需要控制辊弯成型变形量,主要是外圆角不可过小。在弯曲角不能改变的条件下只能加大弯曲半径,通常情况下,外圆角大于或等于壁厚的2倍,而当壁厚大于或等于8 mm时,外圆角应大于或等于壁厚的2.5倍。对后续有深加工要求的异型管产品,必须选择钢质好的原材料,尤其要保证一定的塑性,并根据异型管产品钢种和断面形状的不同,控制一定的屈强比和延伸率[1]。     

Fabrication of silica-based ceramic cores with internal lattice structures by stereolithography

Ceramic cores are widely used in investment casting, and ideal properties of cores are essential for high-quality castings. Under the circumstances requiring thick cores, solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage. Therefore, with the superiority of ceramic stereolithography in producing complex ceramic parts, hollow cores with lattice structures were designed and fabricated. The dimensional accuracy and properties of the green and sintered bodies were evaluated. Results show the dimensional accuracy of sintered cores is controlled within ±0.25 mm benefited from the precise green bodies. The mechanical properties are not obviously deteriorated. The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500 °C with a creep deformation of 0.345 mm. Furthermore, casting verifications prove that the hollow cores meet the requirements of investment casting. Smooth casting surfaces are obtained, at the same time, the core-removal efficiency is improved by over 3 times.

     

轨道客车车顶架用多功能不锈钢异形管成型工艺设计

介绍了我国城市轨道交通的发展趋势,以及不锈钢型材在轨道客车上的使用优势。对采用圆变方冷弯成型工艺制造的用于地铁客车车顶架不锈钢异形排水管的工艺设计方法进行了分析。经试制和检测,产品性能达到了Q/SF 90-004—2006《轨道车辆常用不锈钢和钢带订货技术条件》要求,并得到了广泛的推广应用。     

通长不锈钢地铁客车车顶边梁的开发

由于301/301L奥氏体不锈钢具有成型性能好、表面质量优良、耐大气腐蚀性能好、成本低等特点,所以越来越广泛地应用在城市轨道客车车体的制造中。但301/301L奥氏体不锈钢在冷弯变形过程存在较大的弹性回复变形,且屈服强度越大,弹性回复就越大。通过对301L奥氏体不锈钢冷弯变形过程中的生产工艺分析,运用合理的变形工艺,解决了变形过程中产生的各种缺陷。