Study on the machinability of resulfurized composite free-cutting steels

Lou, Dianjun; Cui, Kun; Jia, Yongzhen

doi:10.1007/s11665-997-0017-0

Cited by 32 publications

(24 citation statements)

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“…[5][6][7][8] Manganese sulfide inclusions are typical inclusions detected in non-quenched and tempered (NQT) steels. Medium content of sulfur is usually added into steels for their beneficial effects on improving machinability, 9,10) retarding grain growth 11,12) and inducing intragranular ferrite. 11,13,14) However, the large-sized elongated MnS inclusions, which exist in longitudinal section after deformation, are severely detrimental to the transverse mechanical properties of steels.…”

Section: Introductionmentioning

confidence: 99%

Distribution and Morphology of MnS Inclusions in Resulfurized Non-Quenched and Tempered Steel with Zr Addition

Cheng

Chen³

et al. 2018

ISIJ International

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Distribution and morphology of MnS inclusions in as-cast ingots and as-forged bars of two Zr-bearing resulfurized non-quenched and tempered (NQT) steels have been performed. In the low Zr-bearing steel (0.001 wt%), MnS inclusions, which are teardrop-shaped or rod-like in two-dimensional (2D) morphology and dendritic or skeletal in three-dimensional (3D) morphology, are mainly distributed and segregated at the grain boundaries. While in the high Zr-bearing steel (0.0066 wt%), MnS inclusions are spherical or angular in both 2D and 3D observation and the distribution is more uniform than those in low zirconium steel. The calculated results by Thermo-Calc software show that the content of oxygen is not the direct factor that influences the morphology and distribution of MnS inclusions in medium-sulfur low-oxygen NQT steels. ZrO 2 particles are ideal partcles for generation of spherical type I MnS inclusions owing to their strong nucleation capability and large amounts. However, the Zr and Al contents should be controlled cautiously to avoid generating large-sized agminated complex oxides, which are not easy to float and be removed owing to their high density. Otherwise, the ideal particles ZrO 2 would decrease sharply in number and fail in offering sufficient heterogeneous nuclei for type I MnS inclusions. Besides, high proportion of complex MnS inclusions would decrease the supersaturation when pure MnS inclusions begin to precipitate, suppressing the generation of dendritic type II MnS inclusions.

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Section: Introductionmentioning

confidence: 99%

Distribution and Morphology of MnS Inclusions in Resulfurized Non-Quenched and Tempered Steel with Zr Addition

Cheng

Chen³

et al. 2018

ISIJ International

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Section: Modification Mechanism and Route Of Ca On Sulfidesmentioning

confidence: 99%

“…The works of Averin [7], Lou [8], and Jiang et al [9] have shown that Ca can partially transform MnS into CaS, and they can form a solid solution with each other to generate a new phase of (Mn,Ca)S. The hardness of (Mn,Ca)S is relatively high and the ductility is relatively low, and thus it can improve the transverse impact toughness of the steel after rolling. Carl [10] studied the effects of Ca treatment on inclusions in steel, and found that some of the Ca in steel combines with Al2O3 and forms liquid calcium-aluminate, which can be the nucleation core of (Mn,Ca)S inclusions in the subsequent solidification process.…”

Section: Modification Mechanism and Route Of Ca On Sulfidesmentioning

confidence: 99%

Key Elements of Sulfide Modification in the Sulfur-based Free-cutting Steel

Li¹,

Huang²,

An³

et al. 2017

Proceedings of the 2017 2nd International Symposium on Advances in Electrical, Electronics and Computer Engineering (ISAEECE 20

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Sulfides are beneficial inclusion in free-cutting steel, and can cause chips to break easily as an internal source of stress concentration when cutting steel, and also lubricate the tool and workpiece, thus reducing tool wear and improving machinability. Sulfide morphology directly determines the performance of the free-cutting steel, and it is possible to improve the machinability of the free-cutting steel by changing the MnS inclusions into small, dispersive, spherical or spindle-shaped inclusions, thus making them difficult to deform. In aluminum-killed steel treated with Ca or Mg, there are numerous small and dispersive complex inclusions with an oxide core (CaO· Al2O3 or MgO· Al2O3) and a sulfide surface layer ((Mn,Ca)S or (Mn,Mg)S). Mg can form simple oxides like MgO, MgS or Mg-O-S. Mg can also form complex inclusions with an oxide core (MgO) and sulfide surface layer (MnS or Mn-Mg-S). Overview of Sulfide in Sulfur-based Free-cutting SteelThe sulfide in sulfur-based free-cutting steel usually exists as (FeMn)S[1]. MnS are beneficial inclusions which can cause chips to be easily broken as an internal source of stress concentration when cutting steel, and can also lubricate the tool and workpiece and reduce tool wear, thus improving machinability [2,3]. MnS is one of the most common plastic nonmetallic inclusions in free-cutting steel, and is commonly used to improve machinability. The size, shape and distribution of MnS have a significant impact on the performance of the resulting steel. MnS can suppress the grain growth and promote the precipitation of intragranular ferrite, by improving w(Mn)/w(S) to generate more MnS while decreasing the generation of FeS, which has a low melting point, thus finally improving the high temperature ductility of the steel [4].MnS has good deformability and is easy to extend along the rolling direction in the rolling process, which causes anisotropy and significantly decreases the transverse properties of the material [5], and these elongated MnS inclusions are ready sources of cracks and expansion channels in slab steel, thus reduce the life of the material [6]. In order to suppress such harmful effects, it is helpful to form hard inclusions which are difficult to deform by adding an appropriate amount alloying elements, like Ca, Ti, Mg, RE and so on. These hard inclusions distribute around the MnS and suppress its deformation, and make the MnS spindle-shaped or spherical (L /W≤3). Such inclusions deform less during hot processing, and this steel has good machinability. Modification Mechanism and Route of Ca on SulfidesCa is the currently most widely used alloying element to modify sulfides. The works of Averin [7], Lou [8], and Jiang et al. [9] have shown that Ca can partially transform MnS into CaS, and they can form a solid solution with each other to generate a new phase of (Mn,Ca)S. The hardness of (Mn,Ca)S is relatively high and the ductility is relatively low, and thus it can improve the transverse impact

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“…Nowadays, the non-quenched and tempered steel has been widely applied to manufacturing fields, particularly in the form of the machining parts. So a good machinability which is mainly affected by the distribution, composition and quantity of the inclusions in steel is quite vital [1][2][3]. However, the machinability of non-quenched and tempered steel improved is mainly to modify the inclusions by adding elements to liquid steel during the refining process [4,5].…”

Section: Introductionmentioning

confidence: 99%

Inclusions modification and improvement of machinability in a non-quenched and tempered steel with Mg treatment

Sun

Xie

et al. 2020

Metall. Res. Technol.

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To explore the effect of Mg on the inclusions and machinability in a non-quenched and tempered steel, the industrial tests and machining experiments were carried out. The evolutions of the inclusions after Mg treatment were described and the machining effects between Mg addition and non-addition were compared. The results show that with Mg addition of 13 ppm, most of the long-strip inclusions above 50 µm were transformed into spindle and spherical inclusions with the sizes below 50 µm, and the density of inclusions increased from 197 to 356 mm2. The percentage of composite inclusions increased from 9.23 to 28.38%. The machining experiments show that the surface roughness of steel decreased from 4.64 to 2.81. After Mg–Ca treatment, the tool wear decreased from 0.164 to 0.113 mm, and the percentage of C-type chips increased from 24.37 to 79.03%.

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Study on the machinability of resulfurized composite free-cutting steels

Cited by 32 publications

References 0 publications

Distribution and Morphology of MnS Inclusions in Resulfurized Non-Quenched and Tempered Steel with Zr Addition

Distribution and Morphology of MnS Inclusions in Resulfurized Non-Quenched and Tempered Steel with Zr Addition

Key Elements of Sulfide Modification in the Sulfur-based Free-cutting Steel

Inclusions modification and improvement of machinability in a non-quenched and tempered steel with Mg treatment

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