US20030152476A1 - Low-carbon free cutting steel - Google Patents

Low-carbon free cutting steel Download PDF

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US20030152476A1
US20030152476A1 US10/357,419 US35741903A US2003152476A1 US 20030152476 A1 US20030152476 A1 US 20030152476A1 US 35741903 A US35741903 A US 35741903A US 2003152476 A1 US2003152476 A1 US 2003152476A1
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steel
machinability
free cutting
sulfide
mns
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Naoki Matsui
Yasutaka Okada
Koji Watari
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Assigned to SUMITOMO METAL INDUSTRIES, LTD. reassignment SUMITOMO METAL INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: OKADA, YASUTAKA, MATSUI, NAOKI, WATARI, KOJI
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working

Definitions

  • This invention relates to a low-carbon free cutting steel, which is free of Pb and yet superior in machinability and hot workability to the conventional leaded free cutting steels and composite free cutting steels in which lead and one or more machinability improving elements are used combinedly.
  • free cutting steels In manufacturing soft small articles not required to have very high strength, steel materials excellent in machinability, namely the so-called free cutting steels, have so far been used for the improvement of productivity.
  • the most known free cutting steels include resulfurized free cutting steels which is improved in machinability by means of MnS resulting from addition of a large amount of S, leaded free cutting steels obtained by addition of Pb, and composite free cutting steels containing both of S and Pb.
  • leaded free cutting steels are excellent in chip disposability and contribute toward prolonging the tool life.
  • free cutting steels containing Te (tellurium) and/or Bi (bismuth) for the purpose of machinability improvement. These are used in large amounts in automotive parts, personal computer and its accompaniment parts, electric machine/appliance parts, molds, and other various machine parts.
  • JP Kokai S50-20917 there is disclosed a resulfurized free cutting steel containing not more than 0.5% of C, 0.3-0.75% of S and 0.1-0.5% of Ti with the proviso that the Ti content does not exceed the S content.
  • This steel is improved in machinability by utilizing iron sulfides in the main and adding Ti thereto to thereby cause iron sulfides to contain Ti and Mn as solid solution.
  • the C content of this steel is not less than 0.24%.
  • JP Kokai H09-53147 discloses a free cutting steel excellent in carbide tool machinability, which contains C: 0.01-0.2%, Si: 0.10-0.60%, Mn: 0.5-1.75%, P: 0.005-0.15%, S: 0.15-0.40%, O (oxygen): 0.001-0.010%, Ti: 0.0005-0.020% and N: 0.003-0.03%.
  • carbide tool machinability which contains C: 0.01-0.2%, Si: 0.10-0.60%, Mn: 0.5-1.75%, P: 0.005-0.15%, S: 0.15-0.40%, O (oxygen): 0.001-0.010%, Ti: 0.0005-0.020% and N: 0.003-0.03%.
  • the upper limit to the Ti content is as low as 0.02%, no satisfactory tool life can be obtained, and, at the same time, no good chip disposability, which is important as well as tool life, can be obtained.
  • JP Kokai 2001-107182, JP Kokai 2001-152281, JP Kokai 2001-152282 and JP Kokai 2001-152283 disclose a steel containing, as main components, C: less than 0.05%, Mn: 0.1-4.0%, S: more than 0.15% and up to 0.5%, Cr: less than 0.5%, Ti: 0.003-0.3% and B: 0.0003-0.004%. It is a free cutting steel improved in chip disposability by causing B to segregate around sulfides and at the same time improved in machinability by reducing the C content to a level lower than 0.05%. However, since the C content is less than 0.05%, plucking of the steel surface may occur during machining, deteriorating the finished surface; thus, no sufficient machinability can be obtained.
  • JP Kokai 2001-294976 discloses a free cutting steel containing C: 0.02-0.15%, Mn: 0.3-1.8%, S: 0.2-0.5% and, further, at least one of Ti: 0.1-0.6% and Zr: 0.1-0.6% on condition that “Ti+Zr” amounts to 0.3-0.6% and (Ti+Zr)/S is 1.1-1.5.
  • This steel is improved in mechanical anisotropy and machinability by employing the above composition to thereby cause the formation of Ti and Zr sulfides, which have high deformation resistance during hot working.
  • such sulfides having high deformation resistance make it difficult to obtain a pseudo lubricating effect of sulfides during machining; thus, the cutting force increases and the machinability improving effect is restricted.
  • the C content should be 0.05-0.19%.
  • Ti scarcely becomes solid solution in MnS, hence will not form Mn—Ti sulfide, namely (Mn,Ti)S.
  • Ti occurs as Ti sulfide or Ti carbosulfide in a phase separate from MnS. These Ti-based inclusions (sulfide, carbosulfide) occur within MnS, or in a state included in MnS.
  • these sulfides serve as sources of stress concentration and promote the propagation of crack, so that better chip disposability can be attained simultaneously as compared with the conventional resulfurized free cutting steels and Pb-containing composite free cutting steels. Furthermore, the above-mentioned steels have no hot workability problems, hence can be produced in a continuous casting plant without causing any trouble; they are thus excellent in practicability.
  • the present invention has been completed based on the above findings and also on the results of further close investigations concerning the effects of other components than the alloying components mentioned above.
  • the gist of the invention consists in the free cutting steels defined below under (1) to (4).
  • a low-carbon resulfurized free cutting steel that is characterized by consisting of, by mass percent, C: 0.05-0.19%, Mn: 0.4-2.0%, S: 0.21-1.0%, Ti: 0.03-0.30%, Si: not more than 1.0%, P: 0.001-0.3%, Al: not more than 0.2%, O (oxygen): 0.0010-0.050% and N: 0.0001-0.0200%, with the balance being Fe and impurities, and that the contents of Ti and S satisfy the relation (1) given below and the atomic ratio between Mn and S satisfies the relation (2) given below, and containing MnS with Ti sulfide and/or Ti carbosulfide included therein.
  • a low-carbon resulfurized free cutting steel that further comprises, in addition to the components specified above (1), one or more elements selected from the group consisting of Se: 0.001-0.01%, Te: 0.001-0.01%, Bi: 0.005-0.3%, Sn: 0.005-0.3%, Ca: 0.0005-0.01%, Mg: 0.0005-0.01% and rare earth elements: 0.0005-0.01%, and satisfies the above relations (1) and (2).
  • a low-carbon resulfurized free cutting steel that further comprises, in addition to the components specified above (1), one or more elements selected from the group consisting of Cu: 0.01-1.0%, Ni: 0.01-2.0%, Cr: 0.01-2.5%, Mo: 0.01-1.0%, V: 0.005-0.5% and Nb: 0.005-0.1%, and satisfies the above relations (1) and (2).
  • a low-carbon resulfurized free cutting steel that further comprises, in addition to the components specified above (1), one or more elements selected from the group consisting of Se: 0.001-0.01%, Te: 0.001-0.01%, Bi: 0.005-0.3%, Sn: 0.005-0.3%, Ca: 0.0005-0.01%, Mg: 0.0005-0.01% and rare earth elements: 0.0005-0.01%, and one or more elements selected from the group consisting of Cu: 0.01-1.0%, Ni: 0.01-2.0%, Cr: 0.01-2.5%, Mo: 0.01-1.0%, V: 0.005-0.5% and Nb: 0.005-0.1%, and satisfies the above relations (1) and (2).
  • the free cutting steels defined above (1) to (4) desirably have an Si content of less than 0.1% by mass.
  • FIG. 1 is a representation of the results of EPMA (electron probe micro analyzer) analysis of MnS including Ti sulfide and/or Ti carbosulfide observed in a steel according to the invention.
  • FIG. 1( a ) shows one inclusion
  • FIG. 1( b ), FIG. 1( c ) and FIG. 1( d ) show the occurrence of Ti, Mn and S, respectively, in that inclusion.
  • FIG. 2 is a graphic representation showing the relationship between chip disposability and tool life for steels of the invention (steels Nos. 1-29) and steels for comparison (steels Nos. 30-47).
  • FIG. 3 is a graphic representation showing the relationship between reduction of area in hot ductility testing and tool life for steels of the invention (steels Nos. 1-29) and steels for comparison (steels Nos. 30-47).
  • One of the important features of the free cutting steel of the invention is that it contains “MS with Ti sulfide and/or Ti carbosulfide included therein”.
  • Ti in trace amounts, can dissolve in MnS and thus may occur as (Mn,Ti)S. However, the amount of Ti dissolving in that MnS is slight and, therefore, this sulfide is substantially composed of MnS.
  • Ti sulfide or Ti carbosulfide representable by the chemical formula TiS or Ti 4 C 2 S 2 and manifestly differing from such MnS. Most of Ti sulfide and Ti carbosulfide in MnS exists as distinctly separated phases from MnS.
  • FIG. 1 shows the results of area analysis of the steel No. 3 shown in Table 1 given later using the EPMA.
  • One inclusion is shown in (a), and (b) to (d) show the occurrence of Ti, Mn and S respectively in the inclusion.
  • the Ti sulfide or Ti carbosulfide occurs in various states, for example in a state of segregation at interface of MnS and matrix, or in a state of being surrounded by MnS.
  • Ti sulfide and/or Ti carbosulfide occur in that manner together with one MnS particle in separate phases and the percent in area occupied by MnS in one sulfide particle is not less than 50%, such sulfide is defined as “MnS with Ti sulfide and/or Ti carbosulfide included therein”.
  • the constitution and area percentage of the Ti sulfide and/or Ti carbosulfide included in one MnS particle can be confirmed by using the above-mentioned EPMA or EDX.
  • the “MnS with Ti sulfide and/or Ti carbosulfide included therein” in a steel can also be confirmed by the same method, and the number of particles thereof can also be determined. When the number of particles counted in a plurality of fields of view and expressed in terms of mean number per mm 2 is not less than 10/mm 2 , good machinability can be obtained.
  • MnS with Ti sulfide and/or Ti carbosulfide included therein can be caused to occur in a steel by adjusting the composition of the steel in the manner mentioned hereinabove.
  • it is desirable to give a thermal hysteresis to the steel for example, by heating it to a sufficiently high temperature not lower than 1,000° C. after casting and maintaining it at that temperature for a sufficiently long time, followed by forging, or by normalizing it at such a high temperature as mentioned above.
  • C is an important element exerting a great influence on the machinability of the steel.
  • a C content exceeding 0.19% increases the strength of the steel material, thus deteriorating the machinability.
  • the C content is less than 0.05%, the steel material becomes too soft, allowing the occurrence of plucking of the steel surface during machining, and the wear of the tool is rather promoted and the chip disposability is deteriorated. Therefore, the C content is restricted to the range of 0.05-0.19%. A more adequate C content range for obtaining still better machinability is 0.05-0.17%.
  • Mn is an important element, which forms sulfide inclusions with S and exerts a great influence on the machinability.
  • the absolute quantity of the sulfides is insufficient, hence a satisfactory level of machinability cannot be obtained.
  • the strength of the steel material increases and, accordingly, the cutting force increases, so that the tool life is shortened.
  • the relation with the content of S is important.
  • the amount of S should be such that the atomic ratio relation “Mn/S ⁇ 1” should be maintained. For securing those performance characteristics, it is desirable that the Mn content be 0.6 to 1.8%.
  • S is an indispensable element that is effective in forming sulfides or carbosulfides with Mn and/or Ti and improves the machinability.
  • the machinability improving effect of MnS in particular, increases with the increase in the amount thereof. However, at levels below 0.21%, it is impossible to obtain a sufficient amount of sulfide inclusions; hence, no satisfactory machinability can be expected.
  • the S content exceeds 0.35%, the hot workability of the steel is deteriorated, and segregation of S and cracks occur in the center of the steel ingot in the stage of casting.
  • the upper limit to the S content can be raised to 1.0%, without such harmful effects.
  • 0.70% is a preferred upper limit of the S content.
  • Ti forms Ti sulfide or Ti carbosulfide with S or S and C, and the occurrence of these in a form included in MnS improves the machinability and hot workability of the steel. Therefore, Ti is an indispensable important element in the steel of the invention. Even when compared with Mn, Ti is a potent sulfide-forming element and, when its content is not less than 0.03%, it forms Ti sulfide and/or Ti carbosulfide and these occur in a state included in MnS, so that the machinability improving effect can be obtained to a satisfactory extent. At levels lower than 0.03%, the effect is insufficient.
  • a more desirable upper limit to the Ti content is 0.10%.
  • Si is useful as a deoxidizing element in adjusting the oxygen content in the steel.
  • the upper limit to the Si content is set at 1.0%. It is more desirable to reduce the Si content to a level lower than 0.1%.
  • the Si content is desirably not less than 0.001%. Even when it is substantially 0% (zero percent), the machinability will not deteriorate if the oxygen content in the steel can be adjusted to an appropriate level, for example by addition of Al to be mentioned later.
  • P promotes segregation in the steel ingot and deteriorates the hot workability. Therefore, the upper limit to its content is set at 0.3%.
  • P is an element having a machinability improving effect, so that 0.001% is selected at the lower limit so as to produce that effect.
  • a more preferred P content is 0.01-0.15%.
  • Al is used as a potent deoxidizing element and may be contained up to a level of 0.2%.
  • the oxide formed by deoxidation is hard. Therefore, when the Al content exceeds 0.2%, the hard oxide is formed in large amounts, deteriorating the machinability.
  • An Al content of not more than 0.1% is more preferred. In cases where sufficient deoxidation is possible with the above-mentioned Si, the addition of Al is unnecessary, hence the content thereof may be substantially 0% (zero percent).
  • oxygen When an appropriate amount of oxygen is contained in the steel, that oxygen is dissolved in MnS and prevents the elongation of MnS and reduces the anisotropy in mechanical properties. Oxygen further contributes to the improvements in machinability and hot workability and is also effective in preventing the segregation of S. Therefore, it is recommended that oxygen be contained at a level not less than 0.0010%. At levels exceeding 0.05%, however, it may produce adverse effects, such as deterioration of and damage to the refractory material in the stage of melting. Therefore, 0.05% is selected as the upper limit. A more preferred range for properly obtaining the above effects is 0.005-0.02%.
  • N 0.0001-0.0200%
  • N forms hard nitrides with Al and/or Ti, and these nitrides have an effect making grains finer. This effect is produced at an N content level of not less than 0.0001%.
  • these nitrides when present in large amounts, deteriorate the machinability and increase the wear of the cutting tool.
  • TiN is formed on the tool surface and protects the tool and, therefore, a certain amount of nitrides may be present in the steel without deteriorating the machinability.
  • N contents exceeding 0.0200% that effect diminishes.
  • an N content of not more than 0.0150% is preferred.
  • an N content of not more than 0.0100% is preferred.
  • the remainder of the steel other than the components mentioned above comprises Fe and impurities.
  • the steel of the invention comprises, in addition to the components mentioned above, one or more elements selected from the first group or second group or the first and the second groups of elements mentioned below.
  • the first group of elements comprises Se, Te, Bi, Sn, Ca, Mg and rare earth elements. These elements further improve the machinability of the steel.
  • the second group of elements comprises Cu, Ni, Cr, Mo, V and Nb, and these elements improve the mechanical properties of the steel.
  • Se and Te form Mn(S,Se) or Mn(S,Te) with Mn, and are elements effective in machinability improvement. At a level below 0.001%, the effect of each of these is not significant. On the other hand, at levels exceeding 0.01%, not only the effect of each of Se and Te arrives at a point of saturation but also the addition thereof becomes uneconomical; in addition, the hot workability deteriorates.
  • Bi and Sn occur as low-melting metallic inclusions in the steel and produce a lubricating effect in the step of machining, thus improving the machinability. Such effect becomes significant at a level of not lower than 0.005%. However, when the content of each exceeds 0.3%, not only the effect arrives at a point of saturation but also the hot workability becomes deteriorated.
  • Ca and Mg each has a high affinity for S and oxygen in the steel, so that they form sulfides or oxides with these; at the same time, they are dissolved in MnS and occur therein as (Mn,Ca)S and (Mn,Mg)S, respectively. Further, MnS crystallizes with those oxides as nuclei for its formation, so that they are effective in preventing the elongation of MnS. In this way, Ca and Mg control the form of sulfides and thus improve the machinability, so that they may be added according to need. For securing this effect, Ca and Mg may be added each to a content level of not less than 0.0005%.
  • the upper limit to the content of each of them is set at 0.01%.
  • Rare earth elements constitute a group of elements classified as lanthanoids. When they are added, a misch metal or the like containing them as main components is generally used.
  • the content of rare earth elements so referred to herein, is expressed in terms of the total content of one or more elements among the rare earth elements.
  • the rare earth elements form sulfides or oxides with S and oxygen and, at the same time, control the form of sulfides and thereby improve the machinability.
  • their content should be not less than 0.0005%. However, at content levels exceeding 0.01%, the effect arrives at a point of saturation and, further, the yield of addition thereof is low, like Ca and Mg, and the addition thereof in large amounts is uneconomical.
  • Cu improves the hardenability of the steel. When such effect is desired, it may be added to a content of not less than 0.01%. However, when its content exceeds 1.0%, the hot workability of the steel deteriorates and, further, a decrease in machinability is caused.
  • Ni is effective in improving the strength of the steel through solid-solution strengthening and further is effective in improving the hardenability and toughness.
  • its content is desirably not less than 0.01%.
  • content levels exceeding 2.0% cause the machinability to deteriorate and, at the same time, cause the hot workability to deteriorate.
  • Cr is effective in improving the hardenability of the steel.
  • a Cr content of not less than 0.01% is preferred.
  • the machinability deteriorates at content levels exceeding 2.5%.
  • Mo is effective in making the microstructure of the steel fine and thus improving the toughness.
  • a Mo content of not less than 0.01% is desirable.
  • contents exceeding 1.0% the effects arrive at a point of saturation and, in addition, the cost of production of the steel increases.
  • V 0.005-0.5%
  • Nb 0.005-0.1%
  • V and Nb precipitate as fine nitrides or carbonitrides and increase the strength of the steel.
  • the content of each is desirably not less than 0.005%.
  • the above effect arrives at a point of saturation and, in addition, nitrides and/or carbides are formed in excess, causing the machinability to deteriorate.
  • Ti forms Ti sulfide or Ti carbosulfide with S or C and S.
  • the tendency is larger than the tendency of Mn sulfide formation.
  • the effect of Ti is improvement in the tool life because TiN is formed on the tool surface by formation of Ti-basis inclusions during machining as mentioned above.
  • Ti sulfide and Ti carbosulfide are hard inclusions showing a higher deformation resistance as compared with MnS.
  • S is an element inducing cracking during hot forging.
  • a composition satisfies the atomic ratio relation “Mn/S ⁇ 1”, S crystallizes as Mn sulfide and the hot workability will not be adversely affected.
  • Test specimens for microscopic observation were taken from the above forgings at a site corresponding to Df/4 (Df is the diameter of each forging) in the longitudinal sectional direction and, after polishing, subjected to area analysis and quantitative analysis using an EPMA and an EDX. As a result, it was confirmed that, on the average, 10 or more MnS particles with Ti sulfide and/or Ti carbosulfide included therein were present in each mm 2 of the steels from No. 1 to No. 29.
  • Each round bar obtained by forging was machined into bars of 60 mm diameter and subjected to a cutting test.
  • the bar was subjected, at the time of crack formation, to normalization by maintaining the bar as it was at 950° C. for 1 hour, followed by air cooling (AC) and further followed by machining into 60 mm diameter in order to give a test specimen.
  • the machinability test was carried out using a JIS P type carbide tool without TiN coating treatment.
  • the cutting was carried out in the manner of dry turning (without using any lubricating oil) under the following conditions.
  • Cutting speed 150 m/min
  • Feed 0.10 mm/rev
  • Depth of cut 2.0 mm.
  • the mean flank wear (VB) of the cutting tool was measured. For those test specimens showing a mean flank wear of not less than 200 ⁇ m within 30 minutes, the time required for arriving at such wear and the mean flank wear (VB) at that time were measured for each of the specimens. Further, tool life evaluation was carried out using, as a measure, the time required for the mean flank wear (VB) to arrive at 100 ⁇ m. When the test specimen became short during testing due to its superiority in suppressing the tool wear and slow wear rate of the tool, the time required for the mean flank wear (VB) to arrive at 100 ⁇ m was calculated from the turning time-tool wear curve by the regression method. The chip disposability was evaluated by collecting at least 200 chips representative of the chips discharged, weighing them, and calculating the number of chips per unit weight.
  • the hot workability was evaluated in the following manner. For simulating the production conditions in a continuous casting plant, a test specimen, 10 mm in diameter and 130 mm in height for elevated temperature tensile test was taken from each 150-kg steel ingot. The ingot was produced in the same manner as mentioned above. The test specimen was taken in the direction of the steel ingot height so that the specimen center might be close to the surface of the ingot, namely at a site of Di/8 (Di is the diameter of the steel ingot). The specimen was heated to 1,250° C. for 5 minutes by direct charge of an electric current at a fixation distance of 110 mm, and cooled to 1,100° C. at a cooling rate of 10° C./sec.
  • tensile test was carried out at a strain rate of 10 ⁇ 3 /sec. In the tensile test, the area reduction at the site of breakage was determined and the hot workability was evaluated based thereon.
  • the steels Nos. 30 and 31 are composite free cutting steels, and the steel No. 32 is a resulfurized free cutting steel. These are steels (materials corresponding to JIS SUM23L or SUM23) are so far regarded as highest in machinability. As is evident from Table 3 and Table 4 as well as FIG. 2, the steels of the invention are definitely superior in suppressing the tool wear even when compared with the steels Nos. 30 and 31. Furthermore, no crack were observed at all in the steels Nos.
  • those steels are at least comparable to the composite free cutting steels and resulfurized free cutting steel, as shown in Table 3, and thus are free of problems from the practical viewpoint.
  • the steels failing to meet at least one requirement prescribed herein, such as the steels Nos. 30-47, are inferior in at least one of hot ductility, tool life and chip disposability to the steels of the present invention.
  • the steels Nos. 41 and 42 failing to satisfy the relation (2) with respect to Mn and S are very poor in hot workability.
  • the free cutting steel of the invention is superior in machinability to the conventional leaded free cutting steels and composite free cutting steels.
  • This steel is excellent in hot workability as well and can be produced at low cost by continuous casting. Therefore, it is suited for use as a raw material of various machine parts.

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  • Engineering & Computer Science (AREA)
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JP2002026368A JP3758581B2 (ja) 2002-02-04 2002-02-04 低炭素快削鋼
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CN (1) CN1210432C (ja)
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US20050025658A1 (en) * 2003-08-01 2005-02-03 Sumitomo Metal Industries, Ltd. Low-carbon free cutting steel
US20080035296A1 (en) * 2006-04-23 2008-02-14 Sanyo Special Steel Co., Ltd Process for producing cast steel billet or steel ingot of titanium-added case hardening steel
KR101536469B1 (ko) * 2013-12-24 2015-07-13 주식회사 포스코 절삭 가공성 및 진동 감쇠능이 우수한 고망간 강재
US10400320B2 (en) 2015-05-15 2019-09-03 Nucor Corporation Lead free steel and method of manufacturing
CN114480963A (zh) * 2021-12-24 2022-05-13 鞍钢集团北京研究院有限公司 一种环保型低碳低硫含铋易切削钢

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