Tramp Elements Research Articles

The Creep-Rupture Properties of 80 Ni-20 Cr Alloys

The creep-rupture properties and the creep behavior of a series of 80 Ni-20 Cr alloys were investigated over the 1200 to 1800-F range. In the group were two vacuum-melted and three air-melted alloys. Among these five heats there were small but important differences in minor constituents such as silicon, manganese, sulfur, and possible tramp elements, primarily as a result of the melting practice in each case. Of particular interest in this study was the variation in ductility which the various alloys exhibited in creep-rupture tests which lasted from a few minutes to more than 1000 hr. A close examination of ductility behavior was undertaken by breaking down the creep curve into primary, secondary, and third-stage creep as a function of stress and temperature. It is shown that the stress-rupture properties are not affected over a wide temperature and stress range by a change in minor constituents, whereas the ductility behavior can vary considerably.

鋼材の加熱条件とtramp elementsの表面富化

鋼材の加熱条件とtramp elementsの表面富化

鋼材のひびわれ疵防止に関する研究（第1報）加熱条件，スケール生成量および鋼材中の不純元素がひびわれ疵におよぼす影響

In order to investigate the influences of tramp elements contained in steel and of heating conditions upon the surface fissures of hot-worked steel products, hot-bending tests were performed paying special attention to the depth of scaling. The results obtained were as follows: (1) There is a certain critical value of scaling for surface fissures to occur, and over this value cracks increase with the increase of scaling. (2) The critical value of scaling increases as the heating temperature is raised and the tramp elements decreased. (3) The tangent of the curve of crack severity number versus scaling loss of a sample (%) increases as the heating temperature is raised and the amount of the tramp elements increased. (4) When Sn content in steel is 0.03%, there is a linear relationship between the crack severity number and (Cu% in steel × scaling loss of a sample (%)). When Sn content exceeds 0.03%, the curves rise steeply at first and then gradually. (5) The heating atmosphere affects the fissures indirectly through scaling loss, but the scaling velocity has some effects when it is extraodinarily large or small. (6) The relative effects of Sn on the fissures are usually of about the same as that of Cu, but vary with its content and the heating temperature. The relative effects of As on the fissures is about 1/4 of that by Cu. (7) Ni and S have an effect towards decreasing of fissures, and in our experiment the fissures were totally prevented by Ni%/Cu%=1.6.