Classifications

• • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/001—Heat treatment of ferrous alloys containing Ni
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/26—Methods of annealing
• • 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
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/06—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
• • 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
  • C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
• • 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
  • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
• • 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
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • 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
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals

Definitions

• the present invention relates to a low thermal expansion alloy, and more particularly, to a low thermal expansion alloy having excellent machinability.
• Invar alloys having high thermal stability are widely used as component materials for electronics, semiconductor-related equipment, laser working machines, and ultra-precision working equipment.
• conventional Invar alloy has low machinability, and therefore it is limited to a very narrow field of practical use.
• PLT1 discloses a low thermal expansion cast steel, in which C and S are used as free-cutting elements, and which has a graphite of 0.5 to 3% in area ratio, a massive MnS of 0.02 to 0.3% in area ratio, and a tabular MnS of 8 ⁇ m or more of 10 to 700 per 1mm 2 , and has a chemical composition comprising, by mass%, C: 0.3 to 0.9%, Si: 1.5% or less, Mn: 1.0% or less, S: 0.01 to 0.3%, Ni: 25 to 40%, and Mg: 0.005 to 0.1%, wherein the contents of S and Mn satisfy S ⁇ (1/4) Mn or (1/4)Mn ⁇ S ⁇ (1/4)Mn+0.05.
• PLT2 discloses an alloy for a low thermal expansion cast steel excellent in machinability, in which S is used as a free-cutting element, and which consists of an iron-based alloy comprising, by mass%, C: 0.1% or less, Ni: 30 to 34%, Co: 4 to 6%, Mn: 0.1 to 1.0% and S: 0.02 to 0.15%, wherein (Mn/54.94)>(S/32.06) is satisfied, or MnS of 0.007 to 0.2% by volume fraction is contained, and the solid solution S is substantially absent.
• An alloy used for a component of a precision device is required to have excellent machinability from the viewpoint of ease of processing. There is room for further improvement in the machinability of alloys having a low coefficient of thermal expansion.
• the object of the present invention is to provide a low thermal expansion alloy excellent in machinability.
• the present inventors have intensively studied a method of obtaining a low thermal expansion alloy with further improved machinability. As a result, it was found that a low thermal expansion alloy having a low coefficient of thermal expansion and excellent machinability can be obtained by appropriately controlling the contents of Mn, S, and Ni.
• the present invention has been made based on the above findings, and includes the following embodiments.
• a low thermal expansion alloy comprising, by mass%, C: 0.005% or less, Si: 0.50% or less, Mn: 2.00 to 4.00%, P: 0.050% or less, S: 0.100 to 0.300%, Ni:35.00 to 40.00%, and balance of Fe and unavoidable impurities, wherein [Mn] and [S], which denote the content of Mn and S by mass%, satisfy [Mn]/[S] ⁇ 10.0, and an average coefficient of thermal expansion at 18 to 28°C is 5.00 ⁇ 10 -6 /°C or less.
• the content of C is an element which crystalizes as graphite in the cast steel and enhances machinability, also an element which increases the coefficient of thermal expansion.
• the content of C in order to suppress an increase in the coefficient of thermal expansion, should be 0.050% or less.
• the content of C is not essential and the content of C may be 0%.
• the content of C may be 0.001% or more, 0.003% or more, 0.004% or more, or 0.005% or more.
• the content of C may be 0.045% or less, 0.040% or less, 0.035% or less, 0.030% or less, 0.025% or less, or 0.020% or less.
• Si is an element which improves machinability by combining with S. Since the coefficient of thermal expansion increases as the content of Si increases, considering the balance between machinability and the coefficient of thermal expansion, the content of Si should be 0.50% or less. Since the improvement in machinability can be also obtained by adding S, Si is not essential, and the content of Si may be 0%.
• the content of Si may be 0.47% or less, 0.45% or less, 0.40% or less, 0.35% or less, 0.30% or less, or 0.20% or less.
• the content of Si may be 0.01% or more, 0.02% or more, 0.03% or more, 0.05% or more, 0.10% or more, or 0.15% or more.
• Mn is an element which forms a compound with S and improves machinability. Mn is also an element for suppressing cracking during casting and forging. Since the coefficient of thermal expansion increases as the content of Mn increases, the content of Mn should be 2.00 to 4.00% considering the balance between machinability and the coefficient of thermal expansion.
• the content of Mn may be 2.10% or more, 2.20% or more, 2.30% or more, 2.40% or more, 2.50% or more, 2.75% or more, or 3.00% or more.
• the content of Mn may be 3.90% or less, 3.80% or less, 3.70% or less, 3.60% or less, 3.50% or less, or 3.40% or less.
• P is an element contained as an impurity, it is not necessary to be contained in the low thermal expansion alloy of the present invention, and the content of P may be 0%. If P is contained in a large amount, the casting crack is likely to occur, the content of P should be 0.050% or less.
• the content of P may be 0.040% or less, 0.035% or less, 0.030% or less, 0.025% or less, or 0.020% or less. Since the manufacturing cost is increased when the content of P is excessively lowered, the content of P may be more than 0.001%, 0.002% or more, 0.003% or more 0.005% or more.
• S is an element that forms a compound with Mn and improves machinability. Since if the content of S is increased, S segregates at the grain boundaries, causing the alloy to become brittle and easily cracked during casting and forging, considering the balance of embrittlement of the machinability and the alloy, the content of S should be 0.100 to 0.300%.
• the content of S may be 0.105% or more, 0.110% or more, 0.120% or more, 0.130% or more, 0.150% or more, 0.170% or more, or 0.200% or more.
• the S content may be 0.290% or less, 0.280% or less, 0.260% or less, 0.240% or less, or 0.230% or less.
• Ni is an element which decreases the coefficient of thermal expansion.
• the low thermal expansion alloy of the present invention has an average coefficient of thermal expansion of 5.00 ⁇ 10 -6 /°C or less at 18 to 28°C. This coefficient of thermal expansion is obtained mainly by controlling the content of Ni to an appropriate range. If the content of Ni is too large or too small, the coefficient of thermal expansion does not become sufficiently small. In order to sufficiently decrease the coefficient of thermal expansion, the content of Ni should be 35.00 to 40.00%.
• the content of Ni may be 35.20% or more, 35.40% or more, 35.60% or more, 35.80% or more, 36.00% or more, 36.50% or more, 37.00% or more, or 37.50% or more.
• the content of Ni may be 39.80% or less, 39.60% or less, 39.40% or less, 39.20% or less, 39.00% or less, 38.70% or less, or 38.40% or less.
• the balance of the chemical composition is Fe and impurities.
• impurity means to an impurity which is unavoidably mixed from a raw material, a manufacturing environment, or the like when a casting having a chemical composition mainly specified in the present invention is industrially manufactured, and which does not deteriorate the machinability and the coefficient of thermal expansion of the low thermal expansion alloy of the present invention even if the element is mixed.
• the content of impurities is preferably not more than 0.50% in total.
• the content of the impurities may be less than 0.40%, 0.30% or less, 0.20% or less and not more than 0.10% in total. Mn / S ⁇ 10.0
• [Mn]/[S] should be 10.0 or more so that S sufficiently forms a compound S with Mn and machinability is improved.
• [Mn]/[S] may be 10.5 or more, 11.0 or more, 11.5 or more, 12.0 or more, 13.0 or more, 14.0 or more, 15.0 or more, 20.0 or more, or 25.0 or more.
• the small [Mn]/[S] means that the content of S is relatively large compared to the content of Mn, and that the amount of segregation of S at the grain boundaries increases. As a result, there is a possibility that cracks are likely to occur during casting and forging. If [Mn]/[S] is large, the amount of segregation of S at the grain boundaries decreases. Therefore, the upper limit of [Mn]/[S] is not specified.
• [Mn]/[S] may be 50.0 or less, 46.0 or less, 43.0 or less, 37.0 or less, 30.0 or less, or 27.0 or less.
• the low thermal expansion alloy of the present invention has an average coefficient of thermal expansion of 5.00 ⁇ 10 -6 at 18 to 28°C or less.
• the coefficient of thermal expansion is measured by taking a coefficient of thermal expansion measurement test piece from the vicinity of center of a cast product or a forged product, and using a thermal expansion measuring device to measure the range from 0 to 50°C at a heating rate of 3°C/min.
• a thermal expansion measuring device a TD5030S manufactured by Bruker Japan Co., Ltd. may be used.
• the average coefficient of thermal expansion may be 4.90 ⁇ 10 -6 /°C or less, 4.81 ⁇ 10 -6 /°C or less, 4.62 ⁇ 10 -6 /°C or less, 4.50 ⁇ 10 -6 /°C or less, 4.00 ⁇ 10 -6 /°C or less, 4.43 ⁇ 10 -6 /°C or less, or 4.34 ⁇ 10 -6 /°C or less.
• the lower limit of the average coefficient of thermal expansion is not specified.
• the average coefficient of thermal expansion may be a negative value.
• the average thermal expansion coefficient may be 0.01 ⁇ 10 -6 /°C or more, 0.40 ⁇ 10 -6 /°C or more, 0.80 ⁇ 10 -6 /°C or more, 1.60 ⁇ 10 -6 /°C or more, 2.00 ⁇ 10 -6 /°C or more, or 2.50 ⁇ 10 -6 /°C or more.
• the casting mold used in manufacturing the low thermal expansion alloy of the present invention, the pouring device of molten steel into the casting mold, the pouring method is not particularly limited, it may be used known apparatus and methods.
• the steel product can be obtained by directly processing a cast product produced by casting by cutting or the like, or processing after forging.
• the obtained cast product is subjected to a solution treatment.
• the solution treatment the cast product is heated to 750 to 850°C, held 0.5 to 3hr, and then air-cooled. By air cooling, it is possible to reduce the warpage and strain generated during the cutting process since no residual stress occurs as in the case of quenching.
• the solution treatment may be performed after forging described below, instead of after casting.
• hot forging is performed at a temperature of 1050 to 1250°C.
• the forging ratio is preferably 3 or more. Even when hot forging is performed, the low thermal expansion characteristics of the low thermal expansion alloy of the present invention is substantially maintained. Further, it is also possible to process to the thickness 0.1 to 10mm by hot rolling and cold rolling. Even in this case, the low thermal expansion characteristics are substantially maintained.
• the alloy has the chemical composition of the present invention, it is possible to obtain a low thermal expansion alloy excellent in machinability without using a special manufacturing method.
• Low thermal expansion alloys were obtained in the same manner as in Example 1 except that the chemical composition was set to the chemical composition described in Table 1, test pieces for measuring the coefficient of thermal expansion, and a test pieces for evaluating machinability were taken.
• No. 1 to 10 are inventive examples, and No. 11 to 19 are comparative examples in which any chemical compositions or [Mn]/[S] is outside the scope of the present invention. Note that in Nos. 2, 3, 4, 5, 7, 8, 10, 11, 13, 14, and 19, the thermal expansion coefficient measuring test piece, machinability evaluation test piece was taken, also from the cast product before forging.
• the coefficient of thermal expansion As for the coefficient of thermal expansion, the average coefficient of thermal expansion at 18°C to 28°C was measured by using a thermal expansion measuring device (TD5030S manufactured by Bruker Japan Co., Ltd.), and measuring the range of 0 to 50°C at a heating rate of 3°C/min.
• Tool wear amount will be described with reference to FIG. 1 .
• Tool wear amount was defined as the distance from the point where the drill base material was visible (1) to the cutting edge (2) of the drill after processing 100 holes, as shown in FIG. 1 , and machinability was judged to be good, if the tool wear amount was 0.100mm or less.
• the crushability of the chips will be described with reference to FIG. 2 .
• the crushability of the chip was evaluated as "Good” if 80% or mor of the chips were broken into pieces having length of 1cm or less when observing the chips.
• FIG. 2 (a) shows an example of good crushability of chips, (b) shows an example of poor crushability. Note that “poor-extend” in Table 2 means that the length exceeds 1cm with more than 20% of chips.
• Nos. 1 to 10 are inventive examples in which the coefficient of thermal expansion is small, and the tool wear amount and the crushability of the chips are also good, and it was confirmed that the low thermal expansion alloys of the present invention have good machinability in both cast product and forged product.

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• 2024
  • 2024-04-11 JP JP2025514009A patent/JPWO2024214777A1/ja active Pending
  • 2024-04-11 WO PCT/JP2024/014674 patent/WO2024214777A1/ja not_active Ceased
  • 2024-04-11 EP EP24788799.5A patent/EP4696797A1/en active Pending
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