WO2014125770A1 - Lead-containing free-machining steel - Google Patents
Lead-containing free-machining steel Download PDFInfo
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- WO2014125770A1 WO2014125770A1 PCT/JP2014/000317 JP2014000317W WO2014125770A1 WO 2014125770 A1 WO2014125770 A1 WO 2014125770A1 JP 2014000317 W JP2014000317 W JP 2014000317W WO 2014125770 A1 WO2014125770 A1 WO 2014125770A1
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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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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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
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
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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
- C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
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- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
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- 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
- C21D2261/00—Machining or cutting being involved
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- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
Definitions
- the present invention relates to free-cutting steel, and more particularly to lead-free-cutting steel containing lead.
- General machine products such as automobiles and electrical appliances include multiple parts. Many of these parts are manufactured by cutting. Therefore, the steel used as the material of the parts is required to have “easy to cut”, that is, excellent machinability.
- Free-cutting steel has excellent machinability. Typical free-cutting steels are, for example, SUM23, SUM24L, etc. defined in JIS standards. Since Pb enhances the machinability of steel, most free-cutting steel contains Pb. Hereinafter, free-cutting steel containing Pb is referred to as lead free-cutting steel.
- Patent Document 1 JP-A-11-222646 (Patent Document 1) and JP-A-2004-176175 (Patent Document 2) propose improvement of machinability of free-cutting steel. Specifically, in Patent Document 1 and Patent Document 2, the form of MnS inclusions in steel is controlled to enhance the machinability of steel.
- An object of the present invention is to provide a lead free-cutting steel excellent in machinability.
- the lead free-cutting steel according to the present embodiment is, in mass%, C: 0.005 to 0.2%, Mn: 0.3 to 2.0%, P: 0.005 to 0.2%, S: 0 0.01 to 0.7%, Pb: 0.03 to 0.5%, N: 0.004 to 0.02%, and O: 0.003 to 0.03%, with the balance being Fe and Consists of impurities. Further, the number of Pb inclusions having a circle-equivalent diameter of 0.01 to 0.5 ⁇ m in the steel is 10,000 / mm 2 or more.
- the lead free cutting steel according to the present embodiment has excellent machinability.
- the number of Pb inclusions having an equivalent circle diameter of 0.01 to 0.5 ⁇ m and the number of MnS inclusions having an equivalent circle diameter of 0.01 to 0.5 ⁇ m in the steel Is 15000 pieces / mm 2 or more.
- the lead free-cutting steel is one type selected from the group consisting of Cu: 0.5% or less, Ni: 0.5% or less, and Sn: 0.5% or less, instead of part of Fe. You may contain 2 or more types.
- the lead free-cutting steel may contain one or more selected from the group consisting of Te: 0.2% or less and Bi: 0.5% or less, instead of part of Fe. .
- the above-mentioned free-cutting steel may contain one or more selected from the group consisting of Cr: 0.5% or less and Mo: 0.5% or less, instead of part of Fe.
- FIG. 1A is a sectional view in the vicinity of a cutting surface when a cutting edge is large during cutting.
- FIG. 1B is a cross-sectional view of the vicinity of the cutting surface when the cutting edge is small during cutting.
- FIG. 2 is a photographic image of Pb inclusions and Pb—MnS inclusions in steel.
- FIG. 3 is a photographic image of fine Pb inclusions in the matrix.
- FIG. 4 is a schematic diagram for explaining the cooling rate in the casting process.
- FIG. 5A is a schematic diagram for explaining a plunge cutting test.
- FIG. 5B is another schematic diagram for explaining the plunge cutting test.
- the inventors focused on the relationship between the form of Pb inclusions and MnS inclusions in lead free-cutting steel and machinability, and investigated and examined them. As a result, the present inventors obtained the following knowledge.
- the component cutting edge means a part of the steel material being cut and adheres to the cutting edge of the cutting tool being cut.
- the constituent cutting edge functions as a substantial cutting edge while repeatedly falling off and attaching to the tool. Therefore, the constituent cutting edge affects the machinability.
- FIG. 1A and 1B are cross-sectional views of the vicinity of the cutting surface after the cutting tool is removed during the cutting process.
- the white broken line in the figure means the cutting edge position of the cutting tool 3.
- FIG. 1A a large component cutting edge 2 is formed, and the component cutting edge 2 is attached to the steel material 1 away from the cutting tool 3.
- FIG. 1B the constituent cutting edge is sufficiently smaller than that in FIG. 1A, so that it is detached from the steel material 1 together with the cutting tool 3.
- the constituent cutting edge when the constituent cutting edge grows greatly, the constituent cutting edge easily adheres to the steel material.
- the component cutting edge adhering to the steel material comes into contact with the cutting tool again. At this time, the cutting tool may be damaged.
- the surface roughness of the cutting surface of the steel material may become rough due to the component cutting edge adhering to the steel material.
- the constituent cutting edge when detached from the cutting tool, a part of the constituent cutting edge may remain on the cutting tool. In this case, a part of the remaining component cutting edge becomes a nucleus, and the component cutting edge grows again. Therefore, the cutting tool is damaged or the steel surface becomes rough.
- the constituent cutting edge is small as shown in FIG. 1B, the constituent cutting edge is easily detached from the steel material and the cutting tool. In this case, the component cutting edge hardly affects the life of the cutting tool, and the surface roughness of the steel material tends to be good (small).
- the constituent cutting edge is small, and it is preferable that the constituent cutting edge hardly grows during cutting.
- the constituent cutting edge is small, the generation of cracks accompanying the falling off of the constituent cutting edge is promoted.
- the constituent cutting edges frequently fall off while being fine, the surface roughness is improved and the tool life is extended. That is, machinability is increased.
- FIG. 2 is a cross-sectional photograph of lead free-cutting steel obtained by microstructural observation.
- matrix 100, Pb inclusions 4, MnS inclusions, and Pb—MnS inclusions 7 are present in the lead free-cutting steel.
- the Pb inclusion 4 means an inclusion composed of Pb and impurities.
- the MnS inclusion means an inclusion composed of Mn, S and impurities.
- the Pb—MnS inclusion 7 means an inclusion containing MnS inclusion 5 and Pb6 adhering to the surface of the MnS inclusion 5.
- the equivalent circle diameter of each inclusion (Pb inclusion 4, MnS inclusion, and Pb—MnS inclusion 7) in the cross section of the steel material in the drawing direction (for example, the rolling direction) may be larger than 0.5 ⁇ m.
- Pb inclusions, MnS inclusions, and Pb—MnS inclusions having an equivalent circle diameter larger than 0.5 ⁇ m are referred to as “coarse free cutting inclusions”.
- Coarse free-cutting inclusions cause stress concentration and promote crack generation and propagation during cutting. The smaller the aspect ratio of the coarse free-cutting inclusion and the more spherical it is, the more easily stress concentration occurs and cracks are more likely to occur and propagate.
- FIG. 3 is a photographic image of the fine Pb inclusions 40 in the matrix 100 of the lead free-cutting steel of this embodiment obtained by the replica extraction method.
- spherical fine Pb inclusions 40 having a small aspect ratio are dispersed in matrix 100.
- Fine Pb inclusions embrittle the matrix. Therefore, if a large number of fine Pb inclusions are dispersed in the matrix, the constituent blade tip does not grow coarsely, and the fine constituent blade tip is easily generated and dropped off. As a result, the machinability of lead free-cutting steel is increased. Specifically, if the number of fine Pb inclusions is 10,000 / mm 2 or more, excellent machinability can be obtained.
- MnS inclusions having an equivalent circle diameter of 0.01 to 0.5 ⁇ m in the cross section in the drawing direction of the steel material are referred to as “fine MnS inclusions”.
- Fine MnS inclusions are less effective than fine Pb inclusions, but embrittle the matrix. Therefore, if not only fine Pb inclusions but also many fine MnS inclusions are dispersed in the matrix, the machinability is further enhanced. Specifically, if the total number of fine Pb inclusions and fine MnS inclusions is 15000 pieces / mm 2 or more, the machinability of lead free-cutting steel is further enhanced.
- the present inventors have completed the lead free-cutting steel according to this embodiment.
- the lead free-cutting steel according to the present embodiment will be described in detail.
- the lead free-cutting steel according to the present embodiment has the following chemical composition.
- C 0.005 to 0.2%
- Carbon (C) increases the strength of the steel. C further affects the amount of oxygen in the steel and the machinability. If the C content is too low, a large amount of oxygen remains in the steel and pinholes are generated. Furthermore, a hard oxide is produced and machinability is reduced. On the other hand, if the C content is too high, the strength of the steel becomes too high and the machinability deteriorates. Therefore, the C content is 0.005 to 0.2%.
- the minimum with preferable C content is higher than 0.005%, More preferably, it is 0.05%, More preferably, it is 0.07%.
- the upper limit with preferable C content is less than 0.2%, More preferably, it is 0.12%, More preferably, it is 0.09%.
- Mn 0.3 to 2.0%
- Manganese (Mn) forms a soft oxide in the molten steel and suppresses the formation of a hard oxide. Therefore, the machinability of steel is increased. Mn further binds to S to form MnS, thereby reducing the amount of dissolved S. If the amount of dissolved S is reduced, high temperature embrittlement cracking is suppressed. If the Mn content is too low, the above effect is difficult to obtain. If the Mn content is too low, S forms FeS instead of S forming MnS, and the steel becomes brittle. On the other hand, if the Mn content is too high, the hardness of the steel becomes too high, and the machinability and cold workability deteriorate.
- the Mn content is 0.3 to 2.0%.
- the minimum with preferable Mn content is higher than 0.3%, More preferably, it is 0.5%, More preferably, it is 0.8%.
- the upper limit with preferable Mn content is less than 2.0%, More preferably, it is 1.8%, More preferably, it is 1.6%.
- P 0.005 to 0.2% Phosphorus (P) embrittles the steel and increases the machinability of the steel. If the P content is too low, this effect cannot be obtained. On the other hand, if the P content is too high, the effect of improving machinability is saturated. If the P content is too high, it is further difficult to stably produce steel. Therefore, the P content is 0.005 to 0.2%.
- the minimum with preferable P content is higher than 0.005%, More preferably, it is 0.03%, More preferably, it is 0.05%.
- the upper limit with preferable P content is less than 0.2%, More preferably, it is 0.15%, More preferably, it is 0.1%.
- S 0.01 to 0.7% Sulfur (S) combines with Mn to form MnS inclusions. MnS inclusions enhance the machinability of steel. Furthermore, since Pb is aggregated around MnS crystallized in the solidification process, MnS uniformly disperses Pb in the steel. If the S content is too low, the above effect cannot be obtained. On the other hand, if the S content is too high, a sulfide containing coarse MnS as a main component is generated, and the hot deformation characteristics are deteriorated. Therefore, the S content is 0.01 to 0.7%.
- the preferable lower limit of the S content is higher than 0.01%, more preferably 0.05%, and further preferably 0.15%. is there.
- the upper limit with preferable S content is less than 0.7%, More preferably, it is 0.5%, More preferably, it is 0.4%.
- the preferable S content is 0.28% or more.
- Pb 0.03 to 0.5%
- Lead (Pb) hardly dissolves in Fe of the matrix and forms soft Pb inclusions. Further, Pb is adjacent to the periphery of MnS and forms Pb—MnS inclusions. Furthermore, Pb exists as fine Pb inclusions in the matrix, and enhances the machinability of steel. If the Pb content is too low, the above effect cannot be obtained. On the other hand, if the Pb content is too high, it becomes difficult to stably produce lead free-cutting steel. Therefore, the Pb content is 0.03 to 0.5%.
- the minimum with preferable Pb content is higher than 0.03%, More preferably, it is 0.1%, More preferably, it is 0.15%.
- the upper limit with preferable Pb content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.35%.
- N 0.004 to 0.02% Nitrogen (N) affects the machinability and the surface roughness after cutting. If the N content is too low, dislocations in the steel at the time of cutting tend to move. Therefore, the ductility of the matrix becomes too high. In this case, cutting flaking easily occurs and good surface roughness cannot be obtained. On the other hand, if the N content is too high, dislocations are difficult to move. In this case, the steel becomes brittle, and the steel is easily cracked during cold working other than cutting such as wire drawing or cold forging. Therefore, the N content is 0.004 to 0.02%.
- the minimum with preferable N content is higher than 0.004%, More preferably, it is 0.006%, More preferably, it is 0.008%.
- the upper limit with preferable N content is less than 0.02%, More preferably, it is 0.018%, More preferably, it is 0.015%.
- Oxygen (O) affects the shape of MnS. If the O content is too low, the amount of oxygen in MnS is also reduced. Therefore, the stretchability of MnS increases.
- MnS is easily stretched in a predetermined direction (for example, the rolling direction), and anisotropy is easily generated in the steel. In this case, the cutting edge of the component becomes large during cutting, or irregular dropping of the cut steel portion occurs. Therefore, the steel surface becomes rough and the tool deteriorates.
- the shape of MnS affects the dispersion of Pb. Therefore, a high aspect ratio (that is, stretched) MnS is not preferable.
- the O content is 0.003 to 0.03%.
- the minimum with preferable O content is higher than 0.003%, More preferably, it is 0.005%, More preferably, it is 0.008%, More preferably, it is 0.012%.
- the upper limit with preferable O content is less than 0.03%, More preferably, it is 0.025%, More preferably, it is 0.022%.
- a more preferable upper limit of the O content is 0.018%.
- the remainder of the lead free cutting steel according to the present embodiment is made of iron (Fe) and impurities.
- the impurities referred to here are ores and scraps used as raw materials for steel, or elements mixed in from the environment of the manufacturing process.
- Pb inclusions circle equivalent diameter in the stretching direction of the cross section of the steel material is 0.01 ⁇ 0.5 [mu] m (fine Pb inclusions) number N Pb is 10000 / mm 2 or more.
- the matrix becomes brittle when a large number of fine Pb inclusions are dispersed in the matrix. Therefore, fine cutting edges are frequently generated and dropped during cutting. As a result, machinability is increased.
- the number of fine Pb inclusions NPb is less than 10,000 / mm 2 , the matrix is not sufficiently brittle. For this reason, the generation and separation of the constituent cutting edges are easily caused by the shape of the coarse free-cutting inclusion.
- the material of the steel portion including the coarse inclusions is not uniform.
- the attachment, generation and growth of the constituent cutting edges are also likely to occur non-uniformly in the width direction of the cutting edge.
- the constituent cutting edge has large irregularities and tends to be coarse.
- the shape of the detaching piece of the component cutting edge to be detached becomes irregular and large, causing damage to the tool or deteriorating the surface roughness. That is, machinability is reduced.
- the number of fine Pb inclusions NPb is preferably 15000 pieces / mm 2 or more, more preferably 20000 pieces / mm 2 or more.
- the upper limit of the number of fine Pb inclusions NPb is not particularly limited.
- the upper limit of the number of fine Pb inclusions NPb is, for example, 1 million pieces / mm 2 .
- the total number of the fine Pb inclusions and the number of MnS inclusions (fine MnS inclusions) having a circle-equivalent diameter of 0.01 to 0.5 ⁇ m (hereinafter referred to as fine rebound).
- the total number of cutting inclusions TN) is 15000 pieces / mm 2 or more.
- the fine MnS inclusion is less effective than the fine Pb inclusion, the matrix becomes brittle. Therefore, when the total number TN of fine free-cutting inclusions is 15000 pieces / mm 2 or more, the matrix is further embrittled and the machinability is further improved.
- the total number TN of fine free-cutting inclusions is preferably 20000 pieces / mm 2 or more, more preferably 25000 pieces / mm 2 or more.
- the upper limit of the total number TN of fine free-cutting inclusions is not particularly limited.
- the upper limit of the total number TN of fine free-cutting inclusions is, for example, 1 million pieces / mm 2 .
- the fine Pb inclusion number NPb and the fine free-cutting inclusion total number TN are obtained by the following measuring method.
- a cross section (hereinafter referred to as a main surface) that is parallel to the drawing direction (for example, rolling direction) of the lead free-cutting steel material (for example, bar steel, wire rod, etc.) and includes the center line of the lead-free-cutting steel material is polished.
- a test piece is taken from a position (so-called R / 2 position) at a half depth of the radius in the radial direction from the surface of the lead free cutting steel material.
- a sample is prepared from the main surface of the test piece based on the extraction replica method. Using a transmission electron microscope (TEM), TEM images of any 10 fields of the sample surface are obtained. The magnification of TEM shall be 20000 times. The area of each visual field is 50 ⁇ m 2 (10 ⁇ m ⁇ 5 ⁇ m, that is, 5 ⁇ 10 ⁇ 4 mm 2 ).
- TEM transmission electron microscope
- inclusions are identified by EPMA (electron beam microanalyzer) or EDS (energy dispersive X-ray microanalyzer). Thereby, Pb inclusion and MnS inclusion can be specified.
- EPMA electron beam microanalyzer
- EDS energy dispersive X-ray microanalyzer
- the equivalent circle diameter means the diameter of a circle when the area of inclusions is converted into a circle having the same area.
- the equivalent circle diameter can be measured using a known particle size distribution measurement software using a TEM image.
- the total number N1 of Pb inclusions (fine Pb inclusions) having an equivalent circle diameter of 0.01 to 0.5 ⁇ m in 10 fields of view and the equivalent circle diameter in 10 fields of view of 0.01 to 0.5 ⁇ m.
- the total number N2 (pieces) of MnS inclusions (fine MnS inclusions) is determined.
- the number of fine Pb inclusions NPb (pieces / mm 2 ) and the total number of fine free-cutting inclusions TN (pieces / mm 2 ) are obtained by the following formulas (1) and (2).
- N Pb N1 / TA (1)
- TN (N1 + N2) / TA (2)
- the lead free-cutting steel according to the present embodiment may further contain one or more selected from the group consisting of Cu, Ni and Sn instead of a part of Fe. These selective elements increase the corrosion resistance.
- Cu 0.5% or less Copper (Cu) is a selective element. Cu increases the corrosion resistance of steel. Cu further increases the machinability of the steel. On the other hand, if the Cu content is too high, the hot ductility of the steel decreases. Therefore, the Cu content is 0.5% or less. If the Cu content is 0.05% or more, the above-described effect is remarkably obtained.
- the more preferable lower limit of the Cu content is 0.07%, and more preferably 0.15%.
- the upper limit with preferable Cu content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.3%.
- Nickel (Ni) is a selective element. Ni increases the corrosion resistance of steel. Ni further increases the ductility of the steel. When the lead free-cutting steel contains Cu, Ni suppresses embrittlement of the lead free-cutting steel and improves the production stability of the steel. On the other hand, if Ni content is too high, ductility will become high too much and machinability will fall. Therefore, the Ni content is 0.5% or less. If the Ni content is 0.05% or more, the above effects are remarkably obtained. A more preferred lower limit of the Ni content is 0.1%. The upper limit with preferable Ni content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.3%.
- Tin (Sn) is a selective element. Sn increases the corrosion resistance of steel. Sn further increases the machinability of the steel. On the other hand, if the Sn content is too high, the hot ductility of the steel decreases. Therefore, the Sn content is 0.5% or less. If the Sn content is 0.05% or more, the above-described effect is remarkably obtained.
- the more preferable lower limit of the Sn content is 0.1%, and more preferably 0.2%.
- the upper limit with preferable Sn content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.3%.
- the lead free-cutting steel according to the present embodiment may further contain one or more selected from the group consisting of Te and Bi instead of a part of Fe. These elements are selective elements and enhance the machinability of the steel.
- Te 0.2% or less
- Tellurium (Te) is a selective element. Te increases the machinability of the steel. Te is particularly effective in controlling the shape of free-cutting inclusions. Specifically, the aspect ratio of MnS inclusions and Pb—MnS inclusions is reduced. On the other hand, if the Te content is too high, the hot ductility of the steel decreases. Therefore, the Te content is 0.2% or less. If the Te content is 0.0003% or more, the above-described effect is remarkably obtained. The more preferable lower limit of the Te content is 0.0008%, and more preferably 0.01%. The upper limit with preferable Te content is less than 0.2%, More preferably, it is 0.1%, More preferably, it is 0.05%.
- Bi 0.5% or less Bismuth (Bi) is a selective element. Bi increases the machinability of steel. On the other hand, if the Bi content is too high, the hot ductility of the steel decreases. Therefore, the Bi content is 0.5% or less. If the Bi content is 0.005% or more, the above-described effect is remarkably obtained.
- the more preferable lower limit of the Bi content is 0.008%, and more preferably 0.01%.
- the upper limit with preferable Bi content is less than 0.5%, More preferably, it is 0.1%, More preferably, it is 0.05%.
- the lead free-cutting steel according to the present embodiment may further contain one or more selected from the group consisting of Cr and Mo instead of part of Fe. These selective elements increase the hardness of the steel after rolling.
- the lead free-cutting steel of this embodiment often cuts a material that has been drawn and work-hardened. Generally, the harder the steel, the better the surface roughness, but the tool wear is promoted. Therefore, the hardness of the steel affects the dimensional accuracy. In precision parts, it is preferable to control the hardness of steel after work hardening by wire drawing to about 150 to 250 HV, and it is preferable to adjust the hardness to the optimum depending on the shape to be processed and the amount of cutting.
- the hardness of steel after work hardening by wire drawing is determined by the hardness of the steel after rolling, work hardening characteristics, and the amount of work.
- the processing amount for example, the wire drawing area reduction ratio
- the hardness after processing is not easily increased. Therefore, it is effective to increase the hardness of the steel after rolling in advance.
- elements that improve the hardenability such as Cr and / or Mo are effective.
- Chromium (Cr) is a selective element. Cr increases the hardness of the steel after rolling. If the Cr content is too high, the steel becomes too hard or it becomes difficult to obtain machinability as free-cutting steel. Therefore, the Cr content is 0.5% or less. If the Cr content is 0.05% or more, the above effects are remarkably obtained.
- the minimum with preferable Cr content is 0.08%, More preferably, it is 0.1%.
- the upper limit with preferable Cr content is less than 0.5%, More preferably, it is 0.3%, More preferably, it is 0.2%.
- Mo 0.5% or less Molybdenum (Mo) is a selective element. Mo increases the hardness of the steel after rolling. If the Mo content is too high, the steel becomes too hard or it becomes difficult to obtain machinability as free-cutting steel. Therefore, the Mo content is 0.5% or less. If the Mo content is 0.02% or more, the above-described effects can be obtained remarkably. A preferable lower limit of the Mo content is 0.03%. The upper limit with preferable Mo content is less than 0.2%, More preferably, it is 0.1%.
- molten steel satisfying the above chemical composition is made into a slab by a continuous casting method.
- the molten steel is made into an ingot by the ingot-making method. (Casting process).
- a slab or an ingot is hot-worked and a lead free-cutting steel material is manufactured (hot work process).
- molten steel is cast to produce a slab.
- the cross-sectional area of the slab is, for example, any of 350 mm ⁇ 560 mm, 220 mm ⁇ 220 mm, and 150 mm ⁇ 150 mm.
- the cooling rate RC of the molten steel is controlled by the cross-sectional area of the material and the cooling conditions during the solidification process.
- Pb has almost no solubility in molten steel and is dispersed as droplets in the molten steel.
- Pb aggregates with MnS inclusions to form coarse free-cutting inclusions (Pb—MnS inclusions), or Pb grains aggregate to form coarse Pb inclusions.
- Pb also produces fine Pb inclusions.
- FIG. 4 is a cross-sectional view of the cast slab.
- the cooling rate from the liquidus temperature to the solidus temperature at the point P1 at the position W / 4 from the surface toward the material center is the cooling rate in the casting step S1. It is defined as RC (° C./min).
- RC ° C./min
- the cooling rate RC is 15 to 30 ° C./min, many fine Pb inclusions are dispersed in the steel.
- the number of fine Pb inclusions NPb is less than 10,000 / mm 2 .
- the cooling rate RC exceeds 30 ° C./min
- the solid solution S increases excessively.
- the hot ductility of the steel is reduced. Therefore, when producing a raw material (slab) by a continuous casting method, breakout may occur.
- the material may crack during hot working, or wrinkles due to the crack may occur.
- the secondary dendrite arm interval ⁇ 2 depends on the cooling rate. Therefore, the cooling rate RC can be obtained by measuring the secondary dendrite arm interval ⁇ 2.
- the molten steel is sufficiently stirred during continuous casting. Specifically, the molten steel in the mold is stirred during continuous casting so that the molten steel flow velocity VE is 10 to 40 cm / s.
- the molten steel flow velocity VE is less than 10 cm / s, stirring is insufficient. Therefore, fine Pb inclusions are difficult to be generated and uniformly dispersed, and the number of fine Pb inclusions NPb is less than 10,000 / mm 2 .
- the molten steel flow velocity VE exceeds 40 cm / s, the fluctuation of the molten metal surface becomes too large and continuous casting becomes difficult.
- the molten steel flow speed VE by controlling the cooling rate RC, may be 10,000 / mm 2 or more fine Pb inclusions number N Pb.
- the production by continuous casting has been described.
- the ingot is formed by top pouring using a mold having a cross-sectional area of 40000 mm 2 or less (for example, 200 mm ⁇ 200 mm).
- the molten steel is stirred at a speed corresponding to the molten steel flow velocity VE of 10 to 40 cm / s, and the cooling rate RC is also 15 to 30 ° C./min.
- Hot working process In the hot working process, the material is first heated. The heated material is hot worked to produce a lead free cutting steel material.
- Lead free-cutting steel materials are, for example, steel bars, wire rods, billets and the like.
- Hot working includes, for example, block rolling, continuous rolling with a VH stand, hot forging, and the like.
- the surface temperature of the material at the start of hot processing (hereinafter referred to as processing start temperature) is set to 1000 ° C. or higher. If the machining start temperature is low, the fine Pb inclusions are unevenly distributed, because they do not uniformly dispersed, not a fine Pb inclusions number N Pb is 10000 / mm 2 or more.
- the processing start temperature is less than 1000 ° C.
- fine MnS inclusions may not be sufficiently generated.
- the total number TN of fine free-cutting inclusions may be less than 15000 / mm 2 .
- the hot working may be performed a plurality of times.
- the material is heated and subjected to ingot rolling (first hot working), and then the ingot rolled material is heated again to produce a steel bar (second heat).
- first hot working first hot working
- second heat second heat
- the processing start temperature during at least one hot processing (at the first hot processing) is set to 1000 ° C. or higher
- the number of fine Pb inclusions NPb becomes 10,000 / mm 2 or higher.
- the preferable cooling rate RC is 20 ° C./min or more, and the preferable molten steel flow velocity VE is 20 cm / s or more.
- the number of fine Pb inclusions NPb is 10000 / mm 2 or more, but is often less than 15000 / mm 2 . In this case, in order for the total number TN of fine free-cutting inclusions to be 15000 pieces / mm 2 or more, it is preferable that many fine MnS inclusions are generated.
- the cooling rate RC is 20 ° C./min or more and the molten steel flow velocity VE is 20 cm / s or more, many fine MnS inclusions are generated during hot working. Therefore, the total number TN of fine free-cutting inclusions is 15000 pieces / mm 2 or more, and further excellent machinability is obtained.
- the processing start temperature is 1000 ° C. or higher, stretching of coarse free-cutting inclusions during hot processing is also suppressed.
- the processing start temperature can be measured by, for example, a radiation thermometer arranged on the entry side of a hot working apparatus (a lump rolling mill, a continuous rolling mill, a hot forging machine, etc.).
- Lead free cutting steel was manufactured with various chemical compositions and manufacturing conditions, and machinability was evaluated.
- the raw material (slab section 220 ⁇ 220 mm) was manufactured by continuous casting using molten steel.
- the cooling rate RC (° C./min) when casting the steel of each test number was as shown in Table 1.
- the cooling rate RC of each test number was obtained by calculation based on the above formula (3) by measuring the secondary dendrite arm interval.
- the electromagnetic stirring was implemented with respect to the molten steel in a mold at the time of continuous casting.
- the molten steel flow velocity VE (cm / s) of each test number during electromagnetic stirring was as shown in Table 1.
- a round bar material having an outer diameter of 50 mm was manufactured by performing hot working on the material of each test number. In each hot working, any one of a block rolling, a drawing rolling and a hot forging was performed. In the first hot working of each test number, the working start temperature T (° C.) was measured. Table 1 shows the processing start temperature T for each test number.
- test number each time hot working was performed, the surface of the material after hot working was observed to check for cracks. When cracking occurred, the test of that test number was stopped.
- [Free-cutting inclusion observation test] A test piece for observing the structure was taken from the round bar of each test number. Of the surface of the test piece, a cross section that is parallel to the longitudinal direction of the round bar (that is, the rolling direction or the stretching direction) and includes the center line of the round bar is defined as a specular surface. Based on the above-described method, the number of fine Pb inclusions NPb (pieces / mm 2 ) and the total number of fine free-cutting inclusions TN (pieces / mm 2 ) were determined on the microscopic surface. Table 1 shows the number of fine Pb inclusions NPb and the total number of fine free-cutting inclusions TN for each test number.
- Drill drilling test The machinability of the steel of each test number was evaluated by a drill drilling test.
- a 15 mm deep hole was continuously formed a plurality of times at an arbitrary cutting speed using a drill on the round bar material of each test number. Then, the maximum cutting speed VL1000 (m / min) that was capable of being cut until the cumulative hole depth reached 1000 mm (that is, 67 or more holes with a depth of 15 mm could be drilled) was obtained.
- a drill with a diameter of 5 mm made by NACHI (trademark) was used.
- the projecting amount of the drill was 60 mm
- the feed was 0.33 mm / rev
- a commercially available water-soluble cutting oil was used for drilling.
- the drilling direction was a direction (transverse direction) perpendicular to the longitudinal direction of the round bar. Drilling was repeatedly performed until the drill was melted or broken to obtain a cutting speed VL1000. The larger the cutting speed VL1000, the higher the number of holes that can be drilled. Therefore, it was determined that the tool life was excellent and the machinability was high.
- plunge cutting test The surface roughness after cutting the steel of each test number was evaluated by the plunge cutting test shown in FIGS. 5A and 5B.
- the plunge cutting test the surface of the round bar 30 was cut using the parting tool 20 while rotating the round bar 30 around the axis, and grooves G1 to G10 were sequentially formed as shown in FIG. 5B.
- the parting tool 20 was advanced in the radial direction of the round bar 30 to form the groove G1.
- the parting tool 20 was moved backward in the radial direction of the round bar 30 and then moved a predetermined distance in the axial direction of the round bar.
- the parting tool 20 was advanced again in the radial direction to form the groove G2. Thereafter, the grooves G3 to G10 were sequentially formed in the same manner. After forming the groove G10, the parting tool 20 was moved again to the position of the groove G1, and the groove processing was repeated again for the grooves G1 to G10. After performing 200 groove processing (20 grooves for each of the grooves G1 to G10), the surface roughness of the bottom surface of the groove G10 was evaluated.
- the material of the parting tool 20 corresponds to JIS standard SHK57, and the rake angle was 20 ° and the clearance angle was 6 °.
- the cutting speed of the parting tool 20 during grooving was 80 m / min, and the feed was 0.05 mm / rev.
- a commercially available water-insoluble cutting oil was used for cutting.
- the surface roughness was measured by the following method.
- the maximum height Rmax ( ⁇ m) was measured according to JIS B0601 (1972) using a stylus type surface roughness meter on the bottom surface of the groove G10 after the 200-groove processing. It was evaluated that the smaller the maximum height Rmax, the better the machinability.
- Test results The test results are shown in Table 1. “Yes” in the “work crack” column in Table 1 means that a crack was confirmed after hot working. “None” means that no cracks were observed.
- N Pb the number of fine Pb inclusions NPb (pieces / mm 2 ) of each test number is described.
- TN the total number of fine free-cutting inclusions TN (pieces / mm 2 ) of each test number is described.
- VL1000 the cutting speed (m / min) of each test number obtained in the drill drilling test is described.
- Rmax the maximum height Rmax ( ⁇ m) of the surface of each test number obtained in the plunge cutting test is described.
- the chemical composition is appropriate, the cooling rate RC (° C./min) in the casting process, the molten steel flow rate VE (cm / s), the processing start temperature in the hot working process. T (° C.) was also appropriate. Therefore, the number of fine Pb inclusions NPb (pieces / mm 2 ) in the steel is 10000 pieces / mm 2 or more, and the total number of fine free-cutting inclusions TN (pieces / mm 2 ) is 15000 pieces / mm 2 or more. It was. Therefore, the cutting speeds VL1000 of test numbers 1 to 15 were all high and were 130 m / min or higher. Further, the maximum heights Rmax of test numbers 1 to 15 were all small and 14.5 ⁇ m or less.
- the chemical composition was appropriate, the cooling rate RC was in the range of 15 to 30 ° C./min, the molten steel flow velocity VE was 10 to 40 cm / s, and the processing start temperature T was 1000 ° C. or higher. . Therefore, the cutting speed VL1000 was 130 m / min or more, and the maximum height Rmax was 14.5 ⁇ m or less. However, the Pb content was less than 0.15%, and the cooling rate RC was less than 20 ° C./min.
- test number 16 although the number of fine Pb inclusions NPb (pieces / mm 2 ) in steel was 10,000 pieces / mm 2 or more, the total number of fine free-cutting inclusions TN (pieces / mm 2 ) was 15000. The number was less than pieces / mm 2 . Therefore, both the cutting speed VL1000 and the maximum height Rmax were inferior to those of test numbers 1 to 15.
- test number 18 Although the chemical composition was appropriate, the cooling rate RC was too slow. Moreover, the molten steel flow velocity VE was too slow. Furthermore, the processing start temperature T was less than 1000 ° C. Therefore, the number of fine Pb inclusions NPb (pieces / mm 2 ) and the total number of fine free-cutting inclusions TN (pieces / mm 2 ) in the round bar were too small. As a result, the cutting speed VL1000 was too small and the maximum height Rmax was too high.
- test number 19 Although the chemical composition was appropriate, the molten steel flow velocity VE was too slow. Therefore, the number of fine Pb inclusions N Pb (pieces / mm 2 ) was too small, and the maximum height Rmax was high.
- Test number 20 was too low in oxygen content. Furthermore, the molten steel flow velocity VE was too slow. Therefore, the number of fine Pb inclusions N Pb (pieces / mm 2 ) was too small, the cutting speed VL1000 was small, and the maximum height Rmax was also high.
- test number 22 the N content was too low. Therefore, the maximum height Rmax was large and the machinability was low. It is considered that the ductility of the matrix became too high because the N content was low.
- test number 23 Although the chemical composition was appropriate, the cooling rate RC and the molten steel flow rate VE were too slow. Therefore, the number of fine Pb inclusions N Pb (pieces / mm 2 ) was too small, the cutting speed VE was small, and the maximum height Rmax was high.
- test number 24 the chemical composition, the cooling rate RC, and the molten steel flow rate VE were appropriate, but the processing start temperature T was less than 1000 ° C. Therefore, the number of fine Pb inclusions N Pb (pieces / mm 2 ) was too small, the cutting speed VE was small, and the maximum height Rmax was high.
- test number 25 the chemical composition, the molten steel flow velocity VE, and the processing start temperature T were appropriate, but the cooling rate RC was too slow. Therefore, the number of fine Pb inclusions N Pb (pieces / mm 2 ) was too small, the cutting speed VE was small, and the maximum height Rmax was high.
Abstract
Description
本実施の形態による鉛快削鋼は、以下の化学組成を有する。 [Chemical composition]
The lead free-cutting steel according to the present embodiment has the following chemical composition.
炭素(C)は、鋼の強度を高める。Cはさらに、鋼中の酸素量及び被削性に影響を与える。C含有量が低すぎれば、鋼中に酸素が多量に残存し、ピンホールが発生する。さらに、硬質酸化物が生成され、被削性が低下する。一方、C含有量が高すぎれば、鋼の強度が高くなり過ぎ、被削性が低下する。したがって、C含有量は0.005~0.2%である。C含有量の好ましい下限は0.005%よりも高く、さらに好ましくは0.05%であり、さらに好ましくは0.07%である。C含有量の好ましい上限は0.2%未満であり、さらに好ましくは0.12%であり、さらに好ましくは0.09%である。 C: 0.005 to 0.2%
Carbon (C) increases the strength of the steel. C further affects the amount of oxygen in the steel and the machinability. If the C content is too low, a large amount of oxygen remains in the steel and pinholes are generated. Furthermore, a hard oxide is produced and machinability is reduced. On the other hand, if the C content is too high, the strength of the steel becomes too high and the machinability deteriorates. Therefore, the C content is 0.005 to 0.2%. The minimum with preferable C content is higher than 0.005%, More preferably, it is 0.05%, More preferably, it is 0.07%. The upper limit with preferable C content is less than 0.2%, More preferably, it is 0.12%, More preferably, it is 0.09%.
マンガン(Mn)は、溶鋼中において軟質な酸化物を形成し、硬質酸化物の生成を抑制する。そのため、鋼の被削性が高まる。Mnはさらに、Sと結合してMnSを形成し、固溶S量を低減する。固溶S量が低減すれば、高温脆化割れが抑制される。Mn含有量が低すぎれば、上記効果が得られにくい。Mn含有量が低すぎればさらに、SがMnSを形成する代わりにFeSを形成し、鋼が脆化する。一方、Mn含有量が高すぎれば、鋼の硬度が高くなりすぎ、被削性及び冷間加工性が低下する。したがって、Mn含有量は0.3~2.0%である。Mn含有量の好ましい下限は0.3%よりも高く、さらに好ましくは0.5%であり、さらに好ましくは0.8%である。Mn含有量の好ましい上限は2.0%未満であり、さらに好ましくは1.8%であり、さらに好ましくは1.6%である。 Mn: 0.3 to 2.0%
Manganese (Mn) forms a soft oxide in the molten steel and suppresses the formation of a hard oxide. Therefore, the machinability of steel is increased. Mn further binds to S to form MnS, thereby reducing the amount of dissolved S. If the amount of dissolved S is reduced, high temperature embrittlement cracking is suppressed. If the Mn content is too low, the above effect is difficult to obtain. If the Mn content is too low, S forms FeS instead of S forming MnS, and the steel becomes brittle. On the other hand, if the Mn content is too high, the hardness of the steel becomes too high, and the machinability and cold workability deteriorate. Therefore, the Mn content is 0.3 to 2.0%. The minimum with preferable Mn content is higher than 0.3%, More preferably, it is 0.5%, More preferably, it is 0.8%. The upper limit with preferable Mn content is less than 2.0%, More preferably, it is 1.8%, More preferably, it is 1.6%.
燐(P)は鋼を脆化し、鋼の被削性を高める。P含有量が低すぎれば、この効果が得られない。一方、P含有量が高すぎれば、被削性向上の効果が飽和する。P含有量が高すぎればさらに、鋼を安定的に製造することが困難になる。したがって、P含有量は0.005~0.2%である。P含有量の好ましい下限は0.005%よりも高く、さらに好ましくは0.03%であり、さらに好ましくは0.05%である。P含有量の好ましい上限は0.2%未満であり、さらに好ましくは0.15%であり、さらに好ましくは0.1%である。 P: 0.005 to 0.2%
Phosphorus (P) embrittles the steel and increases the machinability of the steel. If the P content is too low, this effect cannot be obtained. On the other hand, if the P content is too high, the effect of improving machinability is saturated. If the P content is too high, it is further difficult to stably produce steel. Therefore, the P content is 0.005 to 0.2%. The minimum with preferable P content is higher than 0.005%, More preferably, it is 0.03%, More preferably, it is 0.05%. The upper limit with preferable P content is less than 0.2%, More preferably, it is 0.15%, More preferably, it is 0.1%.
硫黄(S)は、Mnと結合してMnS介在物を形成する。MnS介在物は鋼の被削性を高める。さらに、Pbは、凝固過程で晶出したMnSの周辺に凝集されるため、MnSは、Pbを鋼中に均一に分散する。S含有量が低すぎれば、上記効果が得られない。一方、S含有量が高すぎれば、粗大なMnSを主成分とする硫化物が生成され、熱間変形特性が低下する。したがって、S含有量は0.01~0.7%である。被削性と圧延等の製造性とのバランスを考慮した場合、S含有量の好ましい下限は0.01%よりも高く、さらに好ましくは0.05%であり、さらに好ましくは0.15%である。S含有量の好ましい上限は0.7%未満であり、さらに好ましくは0.5%であり、さらに好ましくは0.4%である。製造時における鋼の品質安定性を維持しつつ、被削性以外の機械的特定よりも被削性を優先する場合、好ましいS含有量は0.28%以上である。 S: 0.01 to 0.7%
Sulfur (S) combines with Mn to form MnS inclusions. MnS inclusions enhance the machinability of steel. Furthermore, since Pb is aggregated around MnS crystallized in the solidification process, MnS uniformly disperses Pb in the steel. If the S content is too low, the above effect cannot be obtained. On the other hand, if the S content is too high, a sulfide containing coarse MnS as a main component is generated, and the hot deformation characteristics are deteriorated. Therefore, the S content is 0.01 to 0.7%. When considering the balance between machinability and manufacturability such as rolling, the preferable lower limit of the S content is higher than 0.01%, more preferably 0.05%, and further preferably 0.15%. is there. The upper limit with preferable S content is less than 0.7%, More preferably, it is 0.5%, More preferably, it is 0.4%. In the case where machinability is given priority over mechanical identification other than machinability while maintaining the quality stability of the steel at the time of production, the preferable S content is 0.28% or more.
鉛(Pb)はマトリクスのFeにほぼ固溶せず、軟質のPb介在物を形成する。Pbはさらに、MnS周辺に隣接し、Pb-MnS介在物を形成する。Pbはさらに、マトリクス中に微細Pb介在物として存在し、鋼の被削性を高める。Pb含有量が低すぎれば、上記効果が得られない。一方、Pb含有量が高すぎれば、鉛快削鋼を安定して製造するのが困難になる。したがって、Pb含有量は0.03~0.5%である。Pb含有量の好ましい下限は0.03%よりも高く、さらに好ましくは0.1%であり、さらに好ましくは0.15%である。Pb含有量の好ましい上限は0.5%未満であり、さらに好ましくは0.4%であり、さらに好ましくは0.35%である。 Pb: 0.03 to 0.5%
Lead (Pb) hardly dissolves in Fe of the matrix and forms soft Pb inclusions. Further, Pb is adjacent to the periphery of MnS and forms Pb—MnS inclusions. Furthermore, Pb exists as fine Pb inclusions in the matrix, and enhances the machinability of steel. If the Pb content is too low, the above effect cannot be obtained. On the other hand, if the Pb content is too high, it becomes difficult to stably produce lead free-cutting steel. Therefore, the Pb content is 0.03 to 0.5%. The minimum with preferable Pb content is higher than 0.03%, More preferably, it is 0.1%, More preferably, it is 0.15%. The upper limit with preferable Pb content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.35%.
窒素(N)は被削性及び切削後の表面粗さに影響を与える。N含有量が低すぎれば、切削時の鋼中の転位が動きやすい。そのため、マトリクスの延性が高くなり過ぎる。この場合、切削むしれが生じやすくなり、良好な表面粗さが得られない。一方、N含有量が高すぎれば、転位が動きにくくなる。この場合、鋼が脆化し、伸線や冷間鍛造等の切削以外の冷間加工時に鋼が割れやすくなる。したがって、N含有量は0.004~0.02%である。N含有量の好ましい下限は0.004%よりも高く、さらに好ましくは0.006%であり、さらに好ましくは0.008%である。N含有量の好ましい上限は0.02%未満であり、さらに好ましくは0.018%であり、さらに好ましくは0.015%である。 N: 0.004 to 0.02%
Nitrogen (N) affects the machinability and the surface roughness after cutting. If the N content is too low, dislocations in the steel at the time of cutting tend to move. Therefore, the ductility of the matrix becomes too high. In this case, cutting flaking easily occurs and good surface roughness cannot be obtained. On the other hand, if the N content is too high, dislocations are difficult to move. In this case, the steel becomes brittle, and the steel is easily cracked during cold working other than cutting such as wire drawing or cold forging. Therefore, the N content is 0.004 to 0.02%. The minimum with preferable N content is higher than 0.004%, More preferably, it is 0.006%, More preferably, it is 0.008%. The upper limit with preferable N content is less than 0.02%, More preferably, it is 0.018%, More preferably, it is 0.015%.
酸素(O)は、MnSの形状に影響を与える。O含有量が低すぎる場合、MnS中の酸素量も低減する。そのため、MnSの延伸性が高まる。圧延等により鋼を加工した場合、所定の方向(たとえば圧延方向)にMnSが延伸しやすくなり、鋼に異方性が生じやすくなる。この場合、切削時に構成刃先が大型化したり、切削された鋼部分の不規則な脱落が生じる。そのため、鋼の表面が粗くなったり、工具が劣化したりする。本実施形態では特に、MnSの形状はPbの分散に影響する。そのため、アスペクト比の高い(つまり、延伸した)MnSは好ましくない。一方、O含有量が高すぎる場合、鋼中で過剰な硬質酸化物が形成され、鋼の被削性が低下する。したがって、O含有量は0.003~0.03%である。O含有量の好ましい下限は0.003%よりも高く、さらに好ましくは0.005%であり、さらに好ましくは0.008%であり、さらに好ましくは0.012%である。O含有量の好ましい上限は0.03%未満であり、さらに好ましくは0.025%であり、さらに好ましくは0.022%である。耐火物の溶損等を考慮した場合、O含有量のさらに好ましい上限は0.018%である。 O: 0.003-0.03%
Oxygen (O) affects the shape of MnS. If the O content is too low, the amount of oxygen in MnS is also reduced. Therefore, the stretchability of MnS increases. When steel is processed by rolling or the like, MnS is easily stretched in a predetermined direction (for example, the rolling direction), and anisotropy is easily generated in the steel. In this case, the cutting edge of the component becomes large during cutting, or irregular dropping of the cut steel portion occurs. Therefore, the steel surface becomes rough and the tool deteriorates. Particularly in the present embodiment, the shape of MnS affects the dispersion of Pb. Therefore, a high aspect ratio (that is, stretched) MnS is not preferable. On the other hand, when the O content is too high, excessive hard oxide is formed in the steel, and the machinability of the steel is reduced. Accordingly, the O content is 0.003 to 0.03%. The minimum with preferable O content is higher than 0.003%, More preferably, it is 0.005%, More preferably, it is 0.008%, More preferably, it is 0.012%. The upper limit with preferable O content is less than 0.03%, More preferably, it is 0.025%, More preferably, it is 0.022%. When considering the refractory erosion and the like, a more preferable upper limit of the O content is 0.018%.
本実施形態による快削鋼では、鋼材の延伸方向の断面における円相当径が0.01~0.5μmのPb介在物(微細Pb介在物)数NPbが10000個/mm2以上である。上述のとおり、微細Pb介在物がマトリクス中に多数分散することにより、マトリクスが脆化する。そのため、切削時において、微細な構成刃先が頻繁に生成及び脱落する。その結果、被削性が高まる。微細Pb介在物数NPbが10000個/mm2未満である場合、マトリクスが十分に脆化しない。そのため、構成刃先の生成及び離脱が粗大快削介在物の形状に起因しやすくなる。鋼中にアスペクト比が大きい(つまり、延伸した)粗大快削介在物が存在する場合、粗大介在物を含む鋼部分の材質が不均一になる。そのため、構成刃先の付着、生成及び成長も切削刃先の幅方向に不均一に生じやすくなる。この場合、構成刃先は凹凸が大きく、かつ、粗大になりやすい。その結果、離脱する構成刃先の脱落片の形状がイレギュラーかつ大きくなり、工具損傷の原因になったり表面粗さを劣化させたりする。つまり、被削性が低下する。 [About fine Pb inclusions]
The free-cutting steel according to the present embodiment, Pb inclusions circle equivalent diameter in the stretching direction of the cross section of the steel material is 0.01 ~ 0.5 [mu] m (fine Pb inclusions) number N Pb is 10000 / mm 2 or more. As described above, the matrix becomes brittle when a large number of fine Pb inclusions are dispersed in the matrix. Therefore, fine cutting edges are frequently generated and dropped during cutting. As a result, machinability is increased. When the number of fine Pb inclusions NPb is less than 10,000 / mm 2 , the matrix is not sufficiently brittle. For this reason, the generation and separation of the constituent cutting edges are easily caused by the shape of the coarse free-cutting inclusion. When coarse free-cutting inclusions having a large aspect ratio (that is, stretched) are present in the steel, the material of the steel portion including the coarse inclusions is not uniform. For this reason, the attachment, generation and growth of the constituent cutting edges are also likely to occur non-uniformly in the width direction of the cutting edge. In this case, the constituent cutting edge has large irregularities and tends to be coarse. As a result, the shape of the detaching piece of the component cutting edge to be detached becomes irregular and large, causing damage to the tool or deteriorating the surface roughness. That is, machinability is reduced.
好ましくはさらに、鋼材の延伸方向の断面において、上記微細Pb介在物数と、0.01~0.5μmの円相当径を有するMnS介在物(微細MnS介在物)数の総数(以下、微細快削介在物総数TNという)が、15000個/mm2以上である。微細MnS介在物は、微細Pb介在物よりも効果は小さいものの、マトリクスを脆化する。したがって、微細快削介在物総数TNが15000個/mm2以上である場合、マトリクスはさらに脆化し、被削性がさらに高まる。 [About fine MnS inclusions]
Preferably, in the cross section in the drawing direction of the steel material, the total number of the fine Pb inclusions and the number of MnS inclusions (fine MnS inclusions) having a circle-equivalent diameter of 0.01 to 0.5 μm (hereinafter referred to as fine rebound). The total number of cutting inclusions TN) is 15000 pieces / mm 2 or more. Although the fine MnS inclusion is less effective than the fine Pb inclusion, the matrix becomes brittle. Therefore, when the total number TN of fine free-cutting inclusions is 15000 pieces / mm 2 or more, the matrix is further embrittled and the machinability is further improved.
微細Pb介在物数NPb及び微細快削介在物総数TNは、次の測定方法で求められる。鉛快削鋼材(たとえば、棒鋼、線材等)の延伸方向(たとえば圧延方向)に平行であり、鉛快削鋼材の中心線を含む断面(以下、主面という)を研磨する。主面において、鉛快削鋼材の表面から径方向に向かって半径の1/2深さの位置(いわゆるR/2位置)部分から試験片を採取する。試験片の主面から、抽出レプリカ法に基づいて、サンプルを作成する。透過電子顕微鏡(TEM)を用いて、サンプル表面のうち任意の10視野のTEM画像を得る。TEMの倍率は20000倍とする。各視野の面積は50μm2(10μm×5μm、つまり、5×10-4mm2)とする。 [Measuring method of the number of fine Pb inclusions NPb and the number of fine free-cutting inclusions TN]
The fine Pb inclusion number NPb and the fine free-cutting inclusion total number TN are obtained by the following measuring method. A cross section (hereinafter referred to as a main surface) that is parallel to the drawing direction (for example, rolling direction) of the lead free-cutting steel material (for example, bar steel, wire rod, etc.) and includes the center line of the lead-free-cutting steel material is polished. On the main surface, a test piece is taken from a position (so-called R / 2 position) at a half depth of the radius in the radial direction from the surface of the lead free cutting steel material. A sample is prepared from the main surface of the test piece based on the extraction replica method. Using a transmission electron microscope (TEM), TEM images of any 10 fields of the sample surface are obtained. The magnification of TEM shall be 20000 times. The area of each visual field is 50 μm 2 (10 μm × 5 μm, that is, 5 × 10 −4 mm 2 ).
NPb=N1/TA (1)
TN=(N1+N2)/TA (2)
ここで、TA(mm2)は、10視野の総面積である。上記条件において、TA=5×10-4(mm2)である。 Based on the above measurement, the total number N1 of Pb inclusions (fine Pb inclusions) having an equivalent circle diameter of 0.01 to 0.5 μm in 10 fields of view and the equivalent circle diameter in 10 fields of view of 0.01 to 0.5 μm. The total number N2 (pieces) of MnS inclusions (fine MnS inclusions) is determined. Then, the number of fine Pb inclusions NPb (pieces / mm 2 ) and the total number of fine free-cutting inclusions TN (pieces / mm 2 ) are obtained by the following formulas (1) and (2).
N Pb = N1 / TA (1)
TN = (N1 + N2) / TA (2)
Here, TA (mm 2 ) is the total area of 10 fields of view. Under the above conditions, TA = 5 × 10 −4 (mm 2 ).
本実施の形態による鉛快削鋼はさらに、Feの一部に代えて、Cu、Ni及びSnからなる群から選択される1種又は2種以上を含有してもよい。これらの選択元素は耐食性を高める。 [Selected elements]
The lead free-cutting steel according to the present embodiment may further contain one or more selected from the group consisting of Cu, Ni and Sn instead of a part of Fe. These selective elements increase the corrosion resistance.
銅(Cu)は選択元素である。Cuは鋼の耐食性を高める。Cuはさらに、鋼の被削性を高める。一方、Cu含有量が高すぎれば、鋼の熱間延性が低下する。したがって、Cu含有量は0.5%以下である。Cu含有量が0.05%以上であれば、上記効果が顕著に得られる。Cu含有量のさらに好ましい下限は、0.07%であり、さらに好ましくは0.15%である。Cu含有量の好ましい上限は0.5%未満であり、さらに好ましくは0.4%であり、さらに好ましくは0.3%である。 Cu: 0.5% or less Copper (Cu) is a selective element. Cu increases the corrosion resistance of steel. Cu further increases the machinability of the steel. On the other hand, if the Cu content is too high, the hot ductility of the steel decreases. Therefore, the Cu content is 0.5% or less. If the Cu content is 0.05% or more, the above-described effect is remarkably obtained. The more preferable lower limit of the Cu content is 0.07%, and more preferably 0.15%. The upper limit with preferable Cu content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.3%.
ニッケル(Ni)は選択元素である。Niは鋼の耐食性を高める。Niはさらに、鋼の延性を高める。鉛快削鋼がCuを含有する場合は、Niは鉛快削鋼の脆化を抑制し、鋼の製造安定性を高める。一方、Ni含有量が高すぎれば、延性が高くなりすぎ、被削性が低下する。したがって、Ni含有量は0.5%以下である。Ni含有量が0.05%以上であれば、上記効果が顕著に得られる。Ni含有量のさらに好ましい下限は、0.1%である。Ni含有量の好ましい上限は0.5%未満であり、さらに好ましくは0.4%であり、さらに好ましくは0.3%である。 Ni: 0.5% or less Nickel (Ni) is a selective element. Ni increases the corrosion resistance of steel. Ni further increases the ductility of the steel. When the lead free-cutting steel contains Cu, Ni suppresses embrittlement of the lead free-cutting steel and improves the production stability of the steel. On the other hand, if Ni content is too high, ductility will become high too much and machinability will fall. Therefore, the Ni content is 0.5% or less. If the Ni content is 0.05% or more, the above effects are remarkably obtained. A more preferred lower limit of the Ni content is 0.1%. The upper limit with preferable Ni content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.3%.
錫(Sn)は選択元素である。Snは鋼の耐食性を高める。Snはさらに、鋼の被削性を高める。一方、Sn含有量が高すぎれば、鋼の熱間延性が低下する。したがって、Sn含有量は0.5%以下である。Sn含有量が0.05%以上であれば、上記効果が顕著に得られる。Sn含有量のさらに好ましい下限は0.1%であり、さらに好ましくは0.2%である。Sn含有量の好ましい上限は0.5%未満であり、さらに好ましくは0.4%であり、さらに好ましくは0.3%である。 Sn: 0.5% or less Tin (Sn) is a selective element. Sn increases the corrosion resistance of steel. Sn further increases the machinability of the steel. On the other hand, if the Sn content is too high, the hot ductility of the steel decreases. Therefore, the Sn content is 0.5% or less. If the Sn content is 0.05% or more, the above-described effect is remarkably obtained. The more preferable lower limit of the Sn content is 0.1%, and more preferably 0.2%. The upper limit with preferable Sn content is less than 0.5%, More preferably, it is 0.4%, More preferably, it is 0.3%.
テルル(Te)は選択元素である。Teは鋼の被削性を高める。Teは特に、快削介在物の形状制御に有効であり、具体的には、MnS介在物、Pb-MnS介在物のアスペクト比を小さくする。一方、Te含有量が高すぎれば、鋼の熱間延性が低下する。したがって、Te含有量は0.2%以下である。Te含有量が0.0003%以上であれば、上記効果が顕著に得られる。Te含有量のさらに好ましい下限は0.0008%であり、さらに好ましくは0.01%である。Te含有量の好ましい上限は0.2%未満であり、さらに好ましくは0.1%であり、さらに好ましくは0.05%である。 Te: 0.2% or less Tellurium (Te) is a selective element. Te increases the machinability of the steel. Te is particularly effective in controlling the shape of free-cutting inclusions. Specifically, the aspect ratio of MnS inclusions and Pb—MnS inclusions is reduced. On the other hand, if the Te content is too high, the hot ductility of the steel decreases. Therefore, the Te content is 0.2% or less. If the Te content is 0.0003% or more, the above-described effect is remarkably obtained. The more preferable lower limit of the Te content is 0.0008%, and more preferably 0.01%. The upper limit with preferable Te content is less than 0.2%, More preferably, it is 0.1%, More preferably, it is 0.05%.
ビスマス(Bi)は選択元素である。Biは鋼の被削性を高める。一方、Bi含有量が高すぎれば、鋼の熱間延性が低下する。したがって、Bi含有量は0.5%以下である。Bi含有量が0.005%以上であれば、上記効果が顕著に得られる。Bi含有量のさらに好ましい下限は0.008%であり、さらに好ましくは0.01%である。Bi含有量の好ましい上限は0.5%未満であり、さらに好ましくは0.1%であり、さらに好ましくは0.05%である。 Bi: 0.5% or less Bismuth (Bi) is a selective element. Bi increases the machinability of steel. On the other hand, if the Bi content is too high, the hot ductility of the steel decreases. Therefore, the Bi content is 0.5% or less. If the Bi content is 0.005% or more, the above-described effect is remarkably obtained. The more preferable lower limit of the Bi content is 0.008%, and more preferably 0.01%. The upper limit with preferable Bi content is less than 0.5%, More preferably, it is 0.1%, More preferably, it is 0.05%.
クロム(Cr)は選択元素である。Crは圧延後の鋼の硬さを高める。Cr含有量が高すぎれば、鋼が硬くなりすぎたり、快削鋼としての被削性が得られにくくなる。したがって、Cr含有量は0.5%以下である。Cr含有量が0.05%以上であれば、上記効果が顕著に得られる。Cr含有量の好ましい下限は0.08%であり、さらに好ましくは0.1%である。Cr含有量の好ましい上限は0.5%未満であり、さらに好ましくは0.3%であり、さらに好ましくは0.2%である。 Cr: 0.5% or less Chromium (Cr) is a selective element. Cr increases the hardness of the steel after rolling. If the Cr content is too high, the steel becomes too hard or it becomes difficult to obtain machinability as free-cutting steel. Therefore, the Cr content is 0.5% or less. If the Cr content is 0.05% or more, the above effects are remarkably obtained. The minimum with preferable Cr content is 0.08%, More preferably, it is 0.1%. The upper limit with preferable Cr content is less than 0.5%, More preferably, it is 0.3%, More preferably, it is 0.2%.
モリブデン(Mo)は選択元素である。Moは圧延後の鋼の硬さを高める。Mo含有量が高すぎれば、鋼が硬くなりすぎたり、快削鋼としての被削性が得られにくくなる。したがって、Mo含有量は0.5%以下である。Mo含有量が0.02%以上であれば、上記効果が顕著に得られる。Mo含有量の好ましい下限は0.03%である。Mo含有量の好ましい上限は0.2%未満であり、さらに好ましくは0.1%である。 Mo: 0.5% or less Molybdenum (Mo) is a selective element. Mo increases the hardness of the steel after rolling. If the Mo content is too high, the steel becomes too hard or it becomes difficult to obtain machinability as free-cutting steel. Therefore, the Mo content is 0.5% or less. If the Mo content is 0.02% or more, the above-described effects can be obtained remarkably. A preferable lower limit of the Mo content is 0.03%. The upper limit with preferable Mo content is less than 0.2%, More preferably, it is 0.1%.
上述の鉛快削鋼の製造方法の一例を次に説明する。 [Production method]
Next, an example of the manufacturing method of the above-mentioned lead free cutting steel will be described.
鋳造工程では、溶鋼を鋳造して鋳片を製造する。鋳片の横断面積はたとえば、350mm×560mm、220mm×220mm及び150mm×150mmのいずれかである。その素材の断面積及び凝固過程での冷却条件により、溶鋼の冷却速度RCが制御される。Pbは溶鋼への溶解度がほとんどなく、溶鋼中で液滴として分散する。凝固時において、PbはMnS介在物と凝集して粗大快削介在物(Pb-MnS介在物)を形成したり、Pb粒同士で凝集して粗大なPb介在物を生成したりする。Pbはさらに、微細Pb介在物も生成する。溶鋼を十分に攪拌し、かつ、凝固時における冷却速度RCを制御することにより、微細Pb介在物が鋼中で多数分散する。 [Casting process]
In the casting process, molten steel is cast to produce a slab. The cross-sectional area of the slab is, for example, any of 350 mm × 560 mm, 220 mm × 220 mm, and 150 mm × 150 mm. The cooling rate RC of the molten steel is controlled by the cross-sectional area of the material and the cooling conditions during the solidification process. Pb has almost no solubility in molten steel and is dispersed as droplets in the molten steel. During solidification, Pb aggregates with MnS inclusions to form coarse free-cutting inclusions (Pb—MnS inclusions), or Pb grains aggregate to form coarse Pb inclusions. Pb also produces fine Pb inclusions. By sufficiently stirring the molten steel and controlling the cooling rate RC during solidification, many fine Pb inclusions are dispersed in the steel.
RC=(λ2/770)-(1/0.41) (3) The cooling rate RC can be obtained by the following method. Cut the solidified material in the transverse direction. Of the cross section of the material, the secondary dendrite arm interval λ2 (μm) in the thickness direction of the solidified tissue at the point P1 is measured. Using the measured value λ2, the cooling rate RC (° C./min) is obtained based on the following equation (3).
RC = (λ2 / 770) − (1 / 0.41) (3)
熱間加工工程では、初めに、素材を加熱する。そして、加熱された素材を熱間加工して鉛快削鋼材を製造する。鉛快削鋼材はたとえば、棒鋼や線材、ビレット等である。熱間加工はたとえば、分塊圧延、V-Hスタンドによる連続圧延、熱間鍛造等である。 [Hot working process]
In the hot working process, the material is first heated. The heated material is hot worked to produce a lead free cutting steel material. Lead free-cutting steel materials are, for example, steel bars, wire rods, billets and the like. Hot working includes, for example, block rolling, continuous rolling with a VH stand, hot forging, and the like.
表1に示す化学組成を有する試験番号1~25の溶鋼を製造した。 [Test method]
Molten steels having test numbers 1 to 25 having the chemical compositions shown in Table 1 were produced.
各試験番号の丸棒材から、組織観察用の試験片を採取した。試験片の表面のうち、丸棒材の長手方向(つまり、圧延方向又は延伸方向)と平行であり、かつ、丸棒材の中心線を含む断面を検鏡面と定義した。上述の方法に基づいて、検鏡面において、微細Pb介在物数NPb(個/mm2)及び微細快削介在物総数TN(個/mm2)を求めた。表1に、各試験番号の微細Pb介在物数NPb及び微細快削介在物総数TNを示す。 [Free-cutting inclusion observation test]
A test piece for observing the structure was taken from the round bar of each test number. Of the surface of the test piece, a cross section that is parallel to the longitudinal direction of the round bar (that is, the rolling direction or the stretching direction) and includes the center line of the round bar is defined as a specular surface. Based on the above-described method, the number of fine Pb inclusions NPb (pieces / mm 2 ) and the total number of fine free-cutting inclusions TN (pieces / mm 2 ) were determined on the microscopic surface. Table 1 shows the number of fine Pb inclusions NPb and the total number of fine free-cutting inclusions TN for each test number.
各試験番号の鋼の被削性を、ドリル穿孔試験で評価した。ドリル穿孔試験では、各試験番号の丸棒材に対して、ドリルを用いて任意の切削速度で15mm深さの穴を複数回形成し続けた。そして、累計の穴深さが1000mmとなるまで切削可能(つまり、15mm深さの穴が67個以上穿孔可能)であった最高の切削速度VL1000(m/min)を求めた。 [Drill drilling test]
The machinability of the steel of each test number was evaluated by a drill drilling test. In the drill drilling test, a 15 mm deep hole was continuously formed a plurality of times at an arbitrary cutting speed using a drill on the round bar material of each test number. Then, the maximum cutting speed VL1000 (m / min) that was capable of being cut until the cumulative hole depth reached 1000 mm (that is, 67 or more holes with a depth of 15 mm could be drilled) was obtained.
各試験番号の鋼の切削後の表面粗さを、図5A及び図5Bに示すプランジ切削試験で評価した。プランジ切削試験では、突切工具20を用いて、丸棒材30を軸周りに回転させながら丸棒材30の表面を切削して、図5Bに示すとおり、溝G1~G10を順次形成した。具体的には、突切工具20を丸棒材30の半径方向に前進して溝G1を形成した。その後、図5B中の矢印のとおり、突切工具20を丸棒材30の半径方向に後進し、その後、丸棒材の軸方向に所定距離移動した。そして、突切工具20を再び半径方向に前進して、溝G2を形成した。その後、同様に溝G3~溝G10を順次形成した。溝G10を形成後、突切工具20を再び溝G1の位置まで移動し、溝G1~溝G10に対して再び溝加工を繰り返した。200溝加工(各溝G1~G10ごとに20溝加工)実施した後、溝G10の底面の表面粗さを評価した。 [Plunge cutting test]
The surface roughness after cutting the steel of each test number was evaluated by the plunge cutting test shown in FIGS. 5A and 5B. In the plunge cutting test, the surface of the
試験結果を表1に示す。表1中の「加工割れ」欄の「有」は、熱間加工後に割れが確認されたことを意味する。「無」は、割れが確認されなかったことを意味する。「NPb」欄には、各試験番号の微細Pb介在物数NPb(個/mm2)が記載されている。「TN」欄には各試験番号の微細快削介在物総数TN(個/mm2)が記載されている。「VL1000」欄には、ドリル穿孔試験で得られた各試験番号の切削速度(m/min)が記載されている。「Rmax」欄には、プランジ切削試験で得られた各試験番号の表面の最大高さRmax(μm)が記載されている。 [Test results]
The test results are shown in Table 1. “Yes” in the “work crack” column in Table 1 means that a crack was confirmed after hot working. “None” means that no cracks were observed. In the “N Pb ” column, the number of fine Pb inclusions NPb (pieces / mm 2 ) of each test number is described. In the “TN” column, the total number of fine free-cutting inclusions TN (pieces / mm 2 ) of each test number is described. In the “VL1000” column, the cutting speed (m / min) of each test number obtained in the drill drilling test is described. In the “Rmax” column, the maximum height Rmax (μm) of the surface of each test number obtained in the plunge cutting test is described.
Claims (5)
- 質量%で、
C:0.005~0.2%、
Mn:0.3~2.0%、
P:0.005~0.2%、
S:0.01~0.7%、
Pb:0.03~0.5%、
N:0.004~0.02%、及び、
O:0.003~0.03%、
を含有し、残部はFe及び不純物からなり、
鋼中の0.01~0.5μmの円相当径を有するPb介在物数が10000個/mm2以上である、鉛快削鋼。 % By mass
C: 0.005 to 0.2%,
Mn: 0.3 to 2.0%,
P: 0.005 to 0.2%,
S: 0.01 to 0.7%,
Pb: 0.03 to 0.5%,
N: 0.004 to 0.02%, and
O: 0.003-0.03%,
And the balance consists of Fe and impurities,
Lead free-cutting steel in which the number of Pb inclusions having a circle-equivalent diameter of 0.01 to 0.5 μm in the steel is 10000 / mm 2 or more. - 請求項1に記載の鉛快削鋼であってさらに、
鋼中の0.01~0.5μmの円相当径を有するPb介在物数と、0.01~0.5μmの円相当径を有するMnS介在物数との総計が15000個/mm2以上である、鉛快削鋼。 The lead free-cutting steel according to claim 1, further comprising:
The total number of Pb inclusions having an equivalent circle diameter of 0.01 to 0.5 μm and the number of MnS inclusions having an equivalent circle diameter of 0.01 to 0.5 μm in the steel is 15000 pieces / mm 2 or more. There is lead free cutting steel. - 請求項1又は請求項2に記載の鉛快削鋼であって、
前記Feの一部に代えて、
Cu:0.5%以下、
Ni:0.5%以下、及び、
Sn:0.5%以下、
からなる群から選択される1種又は2種以上を含有する、鉛快削鋼。 The lead free-cutting steel according to claim 1 or claim 2,
Instead of a part of the Fe,
Cu: 0.5% or less,
Ni: 0.5% or less, and
Sn: 0.5% or less,
Lead free-cutting steel containing one or more selected from the group consisting of: - 請求項1~請求項3のいずれか1項に記載の鉛快削鋼であって、
前記Feの一部に代えて、
Te:0.2%以下、及び、
Bi:0.5%以下、
からなる群から選択される1種以上を含有する、鉛快削鋼。 The lead free-cutting steel according to any one of claims 1 to 3,
Instead of a part of the Fe,
Te: 0.2% or less, and
Bi: 0.5% or less,
Lead free-cutting steel containing one or more selected from the group consisting of: - 請求項1~請求項4のいずれか1項に記載の鉛快削鋼であって、
前記Feの一部に代えて、
Cr:0.5%以下、及び、
Mo:0.5%以下、
からなる群から選択される1種以上を含有する、鉛快削鋼。 The lead free-cutting steel according to any one of claims 1 to 4,
Instead of a part of the Fe,
Cr: 0.5% or less, and
Mo: 0.5% or less,
Lead free-cutting steel containing one or more selected from the group consisting of:
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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JP2015500126A JP5954483B2 (en) | 2013-02-18 | 2014-01-23 | Lead free cutting steel |
CN201480009269.4A CN104995324B (en) | 2013-02-18 | 2014-01-23 | Lead treated steel |
KR1020157018484A KR101685863B1 (en) | 2013-02-18 | 2014-01-23 | Lead-containing free-machining steel |
Applications Claiming Priority (2)
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JP2013029261 | 2013-02-18 | ||
JP2013-029261 | 2013-02-18 |
Publications (1)
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WO2014125770A1 true WO2014125770A1 (en) | 2014-08-21 |
Family
ID=51353787
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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PCT/JP2014/000317 WO2014125770A1 (en) | 2013-02-18 | 2014-01-23 | Lead-containing free-machining steel |
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JP (1) | JP5954483B2 (en) |
KR (1) | KR101685863B1 (en) |
CN (1) | CN104995324B (en) |
TW (1) | TWI510650B (en) |
WO (1) | WO2014125770A1 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2016199843A1 (en) * | 2015-06-10 | 2016-12-15 | 新日鐵住金株式会社 | Free-cutting steel |
JPWO2018021452A1 (en) * | 2016-07-27 | 2019-05-30 | 日本製鉄株式会社 | Machine structural steel |
WO2021132371A1 (en) * | 2019-12-23 | 2021-07-01 | Jfeスチール株式会社 | Free cutting steel and method for manufacturing same |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN110382727A (en) | 2017-02-28 | 2019-10-25 | 杰富意钢铁株式会社 | Machining wire rod |
TWI717990B (en) * | 2019-12-23 | 2021-02-01 | 日商杰富意鋼鐵股份有限公司 | Free-cutting steel and its manufacturing method |
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- 2014-01-23 CN CN201480009269.4A patent/CN104995324B/en active Active
- 2014-01-23 KR KR1020157018484A patent/KR101685863B1/en active IP Right Grant
- 2014-01-23 WO PCT/JP2014/000317 patent/WO2014125770A1/en active Application Filing
- 2014-02-10 TW TW103104265A patent/TWI510650B/en active
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Also Published As
Publication number | Publication date |
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JP5954483B2 (en) | 2016-07-20 |
CN104995324A (en) | 2015-10-21 |
TWI510650B (en) | 2015-12-01 |
KR20150092321A (en) | 2015-08-12 |
CN104995324B (en) | 2016-08-24 |
TW201437390A (en) | 2014-10-01 |
JPWO2014125770A1 (en) | 2017-02-02 |
KR101685863B1 (en) | 2016-12-12 |
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