Formation Mechanism of Band Delta-Ferrite in 416 Stainless Steel and Its Relationship with MnS and M23C6

Sulfides like MnS are common phases in resulfurized free‐cutting steels, and required to be controlled during the hot working process due to its influence on machinability, mechanical and physical properties of final products. This article extensively reviews published researchs on sulfides in resulfurized free‐cutting steels. The formation mechanism and modification of MnS during steelmaking, casting, and heat treatment are discussed based on a number of relevant studies. Measures to control the morphology and number of sulfides are supplied, which are beneficial for the producing of resulfurized free‐cutting steels with high quality. Thermodynamic calculation proves to be an effective method to predict and control sulfides.This article is protected by copyright. All rights reserved.

Section: Calcium (Ca)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

State‐of‐the‐Art in the Control of Sulfides in Steels

Gao,

Zhang

2023

“…The phase diagram of an AISI 416 steel is shown in Figure 17 c. [ 80 ] According to the phase diagram, the steel could realize complete austenization below 1124 °C. However, on one hand, affected by solidification segregation, δ‐ferrite existed in the billet.…”

Section: Industrial Application Of Te Treatmentmentioning

confidence: 99%

Section: Industrial Application Of Te Treatmentmentioning

confidence: 99%

See 1 more Smart Citation

Tellurium Treatment for the Modification of Sulfide Inclusions and Corresponding Industrial Applications in Special Steels: A Review

Tian

et al. 2022

Self Cite

In 1782, Franz-Joseph Müller von Richenstein, a chemist, discovered a rare element with properties similar to those of selenium (Se). In 1798, Martin H. Klaproth, a German chemist, rediscovered this semi-metallic substance and named it tellurium (Te). [1] Te is mainly concentrated in scattered telluride minerals, sulfide mineral structure of most gold deposits, and bismuth tailings. However, in nature, Te appears in quantities that are considered negligible [2] and is mainly extracted from the ore. Generally, concentrations of 1% to 4% Te can be recovered from the anode slime of an electrolytic copper (Cu) refinery. [3] It has been reported that seafloor ferromanganese nodules are rich in Te; however, the recovery of seafloor minerals is still in its infancy. [3] In organic chemistry, Te can also be produced by the reaction of organic matter with metal compounds of Te. [4] Te plays an important role in chemicals, electronics, inorganic nonmetallic materials, metallurgy, and other industries. [5][6][7][8] Tellurides are considered excellent materials for thermoelectric technologies. [9][10][11][12][13] Te is also widely used nonferrous metallurgy and iron and steel metallurgy. Te can significantly improve the properties of Cu-, tin (Sn)-, and lead (Pb)-based alloys, steels, and cast irons. In the iron and steel metallurgical industry, Te is usually utilized as an added element in steels to refine the grains, regulate the morphology and occurrence state of sulfides in steels, and improve the mechanical properties of steels. [14,15] Te is widely used to increase the machinability of steels. Therefore, Te-bearing steel is typically used to manufacture parts with high precision, high surface quality, and rapid cutting. The forms of Te in different type of steel vary. In addition to the usual states of Fe 1.2 Te and MnTe, [16,17] PbTe [18] is formed in Pb-alloyed steels; Cr 2 Te 3 , [19,20] stainless steels; and CuTe, Cu-alloyed steels. [21] In addition, composite particles formed by telluride and sulfide have been reported in Te-treated sulfur (S)-bearing steel. [22][23][24] In recent years, Te has been added to S-bearing steels, such as free-cutting steel and medium-carbon microalloyed steel, also called nonquenched and tempered steel (NQTS) in China, to reduce the aspect ratio of sulfide and the anisotropy of steel. [23,24]

Pitting Initiated by MnO·Cr₂O₃–MnS and MnS Inclusions in a Si‐/Mn‐Killed Stainless Steel

Liu,

Ren,

Zhang

2024

Two types of inclusions in the stainless steels are detected: MnO·Cr2O3–MnS dual‐phase ones and pure MnS ones. The increase of sulfur content can inhibit the formation of MnO–Cr2O3–MnS inclusions and reduce the harm of MnO·Cr2O3–MnS inclusions on the pitting corrosion of stainless steels. When the sulfur content increases from 26 to 70 ppm, the average pitting potential increases from 0.34 to 0.4 VSCE due to the decrease in the number density of MnO–Cr2O3–MnS inclusions. A Cr‐depletion zone exists in the steel matrix around MnO–Cr2O3–MnS inclusions. The size of pits induced by MnO·Cr2O3–MnS inclusions is larger, which poses a more serious threat to the pitting resistance of stainless steels.