1935, H. Schenk, a famous German metallurgist, pointed out in the article "Causes of white spots in steel" that hydrogen in steel is the fundamental reason for white spots. Subsequently, Elende, director of the Institute of Iron and Steel Metallurgy, Department of Mining and Metallurgy, Aachen University of Technology, Germany, turned to the study of hydrogen in steel, which began with 1930.
Hydrogen in steel
From 65438 to 0938, Sun Dehe studied for an engineer's degree in this school, and his thesis was about the absorption and escape speed of hydrogen. Sun Dehe studied and explored the basic laws of hydrogen absorption and hydrogen release in industrial pure iron, various binary alloy steels and ternary alloy steels, and started from 1940. As an assistant and doctoral student of Professor Elende, he continued to study the behavior laws of hydrogen in steels, especially alloy steels. Its scope involves the study of diffusion coefficient and diffusion velocity of hydrogen in different alloy steels, especially the different structures of different alloy steels; Hydrogen content and defects in different alloy steels; In the smelting process of high frequency induction furnace, processes such as carburizing, decarbonization and deoxidation will affect the hydrogen content. Sun Dehe drew the following conclusions: different phase structures lead to different hydrogen precipitation, such as no hydrogen precipitation in face-centered cubic austenitic steel with Ni and Mn as the main components; Hydrogen precipitation in cube-centered martensitic steel and cubic-centered ferritic steel is related to the affinity of alloying elements for hydrogen, and the alloying elements with high affinity can inhibit hydrogen precipitation. In addition, the precipitation of hydrogen is also related to the diffusion ability of hydrogen in alloy steel. The diffusion coefficient of hydrogen in ferritic steel decreases with the increase of Si and Cr content, thus completely inhibiting the precipitation of hydrogen.
He determined the diffusion coefficient formula of hydrogen in α-Fe and γ-Fe, which was called "W Geller-Sun" formula by later generations and was often cited. Sun Dehe cooperated with Geller to establish the binary phase diagram of iron-rich angle of iron-hydrogen system by thermodynamic calculation method. This phase diagram was included in the Handbook of Binary Phase Diagram written by Hansen in Germany and the Complete Book of Metallographic Diagram published in Germany.
alloy steel
He designed and manufactured the vacuum hydrogen and oxygen determination instrument for molten steel (vacuum method for short), which is a new instrument with compact structure and reliable performance. The hydrogen content measured by this instrument is compared with that measured by general non-vacuum hydrogen measurement method. The results show that all hydrogen escaping from molten steel during solidification can be collected by vacuum method, so the loss of hydrogen can be ignored. Instead of vacuum sampling, it is difficult to avoid the loss of hydrogen precipitated during liquid solidification. In addition, the amount of CO2 measured by vacuum method can be used to calculate the oxygen content in molten steel. Therefore, the instrument designed by Sun Dehe can measure both hydrogen and oxygen. According to the literature, the improved industrial hydrogen and oxygen measuring device in 1957 still follows the principle of vacuum hydrogen and oxygen measuring device in Sun Dehe. According to the test data of Sun Dehe hydrogen and oxygen analyzer, vacuum pumping can promote dehydrogenation in molten steel. This experimental conclusion has great enlightenment to the vacuum degassing method developed in Germany in the early 1950 s.
The above research results of WernerGdler in Sun Dehe have been published in German iron and steel metallurgical documents 1939, 1943, 1944 and 1950 in the form of papers. Commenting on Sun Dehe's contribution to hydrogen research, Elende wrote: "Sun Dehe has extraordinary diligence, rare agility, skillful and reliable experimental skills and persistent dedication." He expressed his respect and gratitude to Sun Dehe for his experimental work in metallurgy and his contribution and strong support to the work of "stabilizing gas" in the Institute.