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Hashimura, Masayuki; Miyamoto, Keisuke; Hirosumi, Taro; Miyanishi, Kei

doi:10.2320/materia.46.105

Cited by 2 publications

(4 citation statements)

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“…[11][12][13][14] Free-machining steels containing Pb and S were widely used up to now, and needs for their replacement were strongly raised because they contain a harmful element of Pb for human bodies. [15][16][17] In the European Union and Japan, the use of Pb in free-machining steels was recently restricted, [18] but the development and commercialization of alternative free-machining steels such as Bi-S-based free-machining steels was delayed. This is because the hot rolling of Bi-S-based steels is more difficult than that of Pb-S-based steels as the hotrolling cracking occurs more frequently.…”

Section: Introductionmentioning

confidence: 99%

Formation Mechanisms of Cracks Formed During Hot Rolling of Free-Machining Steel Billets

Kim

Shin

Rhee

et al. 2011

Metall Mater Trans A

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In this study, cracks formed in the edge side of Bi-S-based free-machining steel billets during hot rolling were analyzed in detail, and their formation mechanisms were clarified in relation with microstructure. Particular emphasis was placed on roles of bands of pearlites or C-and Mn-rich regions and complex iron oxides present in the edge side. Pearlite bands in the cracked region were considerably bent to the surface, while those in the noncracked region were parallel to the surface. This was because the alignment direction of pearlite bands was irregularly deviated up to 45 deg from the normal direction parallel to the surface, while the billet was rolled and rotated at 90 deg in the same direction between rolling passes. On the edge side, where pearlite bands were bent, iron oxides intruded deeply into the interior along pearlite bands, which worked as stress concentration sites during hot rolling and, consequently, main causes of the crack initiation in the rolled billet. On the surface of the wire rod rolled from the cracked billet, a few scabs were found when some protrusions were folded during hot rolling. In order to prevent the cracking in billets and scab formation in wire rods, (1) the increase of rolling passes and the decrease of reduction ratio for homogeneous rolling of billets and (2) the reduction in sulfur content for minimizing the formation and intrusion of complex iron oxides were suggested.

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Section: Introductionmentioning

confidence: 99%

Formation Mechanisms of Cracks Formed During Hot Rolling of Free-Machining Steel Billets

Kim

Shin

Rhee

et al. 2011

Metall Mater Trans A

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“…Previous studies have used primarily simple optical or electron microscopes to observe the inclusions. [1][2][3][4][5][6][7][8][9] They are generally regarded as the best tools for the observation of microstructures because of their high resolution data in real space. On the other hand, smallangle scattering (SAS) techniques provide limited morphological information about the microstructures, but have the advantage of being able to evaluate a significantly larger area at one time.…”

Section: Introductionmentioning

confidence: 99%

“…However, conventional free cutting steels need lead (Pb) to achieve sufficient machinability. [1][2][3][4][5] Since Pb causes environmental damage, development of reduced-Pb or Pb-free steels is a high-priority task which is being intensively explored. [1][2][3][4][5][6] Resulfurized free cutting steel, which has better machinability than conventional Pb-free steels due to manganese sulfide (MnS) inclusions, is a promising candidate.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5] Since Pb causes environmental damage, development of reduced-Pb or Pb-free steels is a high-priority task which is being intensively explored. [1][2][3][4][5][6] Resulfurized free cutting steel, which has better machinability than conventional Pb-free steels due to manganese sulfide (MnS) inclusions, is a promising candidate. However, since the properties of typical Pb-free resulfurized free cutting steels, e.g., SUM23 of the Japanese Industrial Standards (JIS) Agency and AISI1215 of the American Iron and Steel Institute (AISI), are still insufficient for practical applications compared to Pb-containing steels, additional improvements are still required.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Analysis of Inclusions in Low Carbon Free Cutting Steel Using Small-angle X-ray and Neutron Scattering

et al. 2012

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The microstructure of inclusions in low carbon free cutting steel without lead addition was investigated using small-angle X-ray scattering (SAXS) coupled with small-angle neutron scattering (SANS). The twodimensional (2D) SAXS pattern shows clear scattering due to inclusions composed of large elongated particles aligned along the rolling direction, and small isotropic particles. From a comparison of the simulated and experimental 2D SAXS patterns, the shapes of the inclusions are regarded as ellipsoid for the larger inclusions and spherical for the smaller inclusions. The length of the minor axis in the large inclusion is 6.9 μm, while the diameter of the small inclusion is 0.50 μm. The aspect ratio of the large inclusion is estimated to be 3.8 in the lower q region, and is reduced slightly to 3.5 in the higher q region from the azimuthal plots. The results of an alloy contrast variation (ACV) analysis using both the SAXS and SANS data indicate that the chemical composition of the inclusions is almost NaCl-type manganese sulfide, and that the amount of iron sulfide is low. The volume fractions are 1.4% for the large inclusions and 0.2% for the small inclusions. This is consistent with the area fraction estimated using an optical microscope, and indicates that nearly all of the sulfur in the steel sample forms the manganese sulfide inclusions.

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Cited by 2 publications

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Formation Mechanisms of Cracks Formed During Hot Rolling of Free-Machining Steel Billets

Formation Mechanisms of Cracks Formed During Hot Rolling of Free-Machining Steel Billets

Quantitative Analysis of Inclusions in Low Carbon Free Cutting Steel Using Small-angle X-ray and Neutron Scattering

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