In this work, the non‐metallic inclusions contained in a trial X70 pipeline steels are characterized by optical microscopy, scanning electron microscopy, energy‐dispersive X‐ray spectrum, and transmission electron microscopy. Statistical analysis is conducted to summarize the size and shape of the inclusions. The hydrogen trapping and the resulting hydrogen‐induced cracking (HIC) susceptibility of the steels are tested. Density functional theory is used to calculate the binding energy of hydrogen at MnS inclusions, and the impact of MnS inclusions on hydrogen trapping and the HIC susceptibility is evaluated. It is found that the majority of submicron scale inclusions are MnS, which serve as irreversible hydrogen traps. The content of the trapped hydrogen can be effectively decreased by controlling the size of MnS inclusions below submicron scale and distributing the inclusions uniformly in the steel. As a result, the susceptibility of the steel to HIC is reduced.

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The micro/macro magnetic properties, local element distribution, martensite transformation, and mechanical properties of 304H stainless wires are determined for two cold drawing chains. Finite element simulations are used to analyse the local strain and heat generation. The results show that there is obvious inhomogeneity in the magnetic properties, strain/stress relationship, and strain-induced heat within the drawn wires. Comparing wires with the same total strain, a larger area reduction of previous drawing processes contributes to a higher volume of the martensite phase, while a smaller area reduction of the first process results in an inhibited phase transformation. A higher single strain in the first drawing process leads to additional heat generation at the subsurface of the wire, which would eventually retard the martensite transformation. The inhomogeneous deformation-induced differences in the grain size affect the stability of austenite and transform the final martensite.

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