Comparison of Testing the Z-direction Tear Resistance of Steel Plates with Sulfide Inclusions

ZHONG Yujia

doi:10.3969/j.issn.1004-4620.2025.04.009

Abstract：To clarify the effect law and regulation path of sulfur content on the Z-direction tensile properties of steel plates,mechanical property tests,metallographic observations and SEM analyses were adopted to explore the influence mechanism of sulfur content changes on the Z-direction properties of steel plates.The results show that sulfur content is the core factor regulating the Z-direction cross-sectional reduction rate of steel plates,and has a weak influence on the strength index.When the sulfur content was increased from 0.005%to 0.015%,the Z-direction reduction of area dropped sharply from 45%to 30%,a decrease of 33%,while the tensile strength and yield strength only decreased by 4%and 3%respectively.Microscopic analysis confirmed that under high-sulfur conditions,the number of long strip MnS inclusions in steel significantly increased,with the average length-to-diameter ratio rising from 3 to 12.Inclusions are prone to stress concentration under Z-direction stress,inducing intergranular fracture and accelerating crack propagation,thereby deteriorating Z-direction toughness.By implementing the pre-desulfurization of molten iron and the refining process outside the furnace,the sulfur content can be controlled below 0.010%.Combined with Mn/Ca alloying treatment to optimize the morphology of inclusions,the Z-direction reduction of area can be increased to over 48%.