Refinement of Solidification Structure of H13 Steel by Rare Earth Sulfide

Abstract

To improve the solidification structure of H13 steel, rare earth sulfide (Ce−S) is used as the nucleation core of δ‐ferrite or γ‐austenite to refine the original austenite grain. The relationship between rare earth inclusions and grain refinement is discussed in terms of the type, distribution, size, number, and formation characteristic of rare earth inclusions. The results show that to form a large amount of Ce−S (> 35 mm−2) and inhibit the formation of rare earth oxide (Ce−O), rare earth oxysulfide (Ce−O−S), and MnS, the content of O, S, and Ce must be strictly controlled. Most Ce−S in the solidification structure is located in the original austenite grain interior, indicating that Ce−S can act as the nucleation core of δ‐ferrite or γ‐austenite. The most effective size of Ce−S as nucleation core is 1−2 μm, followed by 2−3 μm, and the Ce−S with the size larger than 3 μm has the least effect. The original austenite grain size is related to the number density of Ce−S, and the higher the number density of Ce−S, the smaller the grain size. The precipitation size of Ce−S during solidification is mostly 1−3 μm, and these Ce−S can act as the nucleation core more effectively.

Effect of trace rare earth elements (Ce) on corrosion resistance of high strength steel used for offshore platform

“…Among them, smallangle grain boundaries mainly include sub-grain boundaries, and large-angle grain boundaries mainly include original austenite grain boundaries and granular bainite grain boundaries. They have high energy and irregular atomic arrangements [30,31]. In addition, these large-angle grain boundaries are high-frequency areas of corrosion.…”

Effect of Rare Earth Cerium Replacement of Nickel on Cryogenic Toughness of 7Ni Steel

“…The research also shows that 0.020-0.022 wt%Ce is added to H13 steel to form small-sized Ce-S inclusions distributed in the grain, while most of Ce-O is distributed in the grain boundary, indicating that Ce-S inclusions is preferentially used as the nucleation core to refine δ-ferrite or γ-austenite grain structure. [42] By adding a certain amount of RE elements, the irregular angular inclusions can be modified into spherical or elliptical REAlO 3 and REAlO 3 -MnS inclusions, reducing the size of the inclusions, and purify the matrix, avoid the formation of crack sources, and improve the performance of steel. [43,44] It is found from the experimental results that on the basis of 7Ni steel, when 0.0026 wt%Ce is added to replace 0.5 wt%Ni, large-angle grain boundaries and fine Ce-containing inclusions can be formed, which effectively inhibit the initiation and propagation of cracks.…”

Cerium Addition Improves Cleanliness and Refines Microstructure of As‐Cast High‐Nitrogen Stainless Bearing Steel

“…To compare the formation possibility of these different products, the chemical reaction equations, together with the standard Gibbs free energy ΔG Θ and the equilibrium constant K a , are listed in Table 2. [13,52] It is known that the standard Gibbs free energy ΔG Θ is calculated as follows: [13] ΔG Θ ¼ ÀRT ln K a (1) where a in Table 2 Besides, f i is the activity coefficient, which can be calculated as follows: [13] log…”