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WO2017038879A1 - Acier pour moules et outil de moulage - Google Patents

Acier pour moules et outil de moulage Download PDF

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Publication number
WO2017038879A1
WO2017038879A1 PCT/JP2016/075518 JP2016075518W WO2017038879A1 WO 2017038879 A1 WO2017038879 A1 WO 2017038879A1 JP 2016075518 W JP2016075518 W JP 2016075518W WO 2017038879 A1 WO2017038879 A1 WO 2017038879A1
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Prior art keywords
mass
mold
steel
amount
thermal conductivity
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Japanese (ja)
Inventor
河野　正道
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Daido Steel Co Ltd
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Daido Steel Co Ltd
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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
    • C21D6/00—Heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to mold steel and a molding tool using the same.
  • the molding tool is composed of a mold or mold parts alone or in combination.
  • the molding tool is used for die casting, plastic injection molding, rubber processing, various castings, warm forging, hot forging, hot stamping and the like. These molding tools have a portion that comes into contact with a molded article having a temperature higher than room temperature.
  • Molds used for die casting, injection molding, hot-to-warm plastic processing, etc. are usually manufactured by quenching and tempering the raw material and processing it into a predetermined shape by die-sculpting.
  • the mold is subjected to a large heat cycle and a large load. Therefore, the material used for this type of mold is required to be excellent in toughness, high temperature strength, wear resistance, crack resistance, heat check resistance and the like.
  • it is difficult to improve a plurality of properties at the same time in mold steel.
  • Patent Document 1 C: 0.1 to 0.6, Si: 0.01 to 0.8, Mn: 0.1 to 2.5, Cu: 0.01 to 2.0 in mass%. Ni: 0.01 to 2.0, Cr: 0.1 to 2.0, Mo: 0.01 to 2.0, one or more of V, W, Nb and Ta in total: Mold steel comprising 0.01 to 2.0, Al: 0.002 to 0.04, N: 0.002 to 0.04, O: 0.005 or less, the balance being Fe and inevitable impurities Is disclosed.
  • This document describes that heat fatigue characteristics and softening resistance are increased by heat-treating such materials under predetermined conditions, thereby suppressing heat check and water-cooled hole cracking. .
  • Patent Document 2 by mass, C: 0.2 to 0.6%, Si: 0.01 to 1.5%, Mn: 0.1 to 2.0%, Cu: 0.01 to 2 0.0%, Ni: 0.01 to 2.0%, Cr: 0.1 to 8.0%, Mo: 0.01 to 5.0%, one or two of V, W, Nb and Ta Total of seeds or more: 0.01 to 2.0%, Al: 0.002 to 0.04%, and N: 0.002 to 0.04%, with the balance being Fe and inevitable impurities Mold steel is disclosed. According to the document, such a material has good hardenability, and by heat-treating it under a predetermined condition, a required impact value can be obtained, and the mold life can be increased. It is described that it is easy to cut.
  • Patent Document 3 C: 0.15 to 0.55 mass%, Si: 0.01 to 2.0 mass%, Mn: 0.01 to 2.5 mass%, Cu: 0.01 to 2. mass%. Selected from the group consisting of 0% by mass, Ni: 0.01-2.0% by mass, Cr: 0.01-2.5% by mass, Mo: 0.01-3.0% by mass, and V and W
  • a steel for a mold material is disclosed that contains at least one total amount of 0.01 to 1.0% by mass, and the balance being Fe and inevitable impurities. This document describes that by heat-treating such a material under predetermined conditions, softening resistance is increased and wear resistance is also improved.
  • Patent Document 4 C: 0.26 to 0.55 wt%, Cr: less than 2 wt%, Mo: 0 to 10 wt%, W: 0 to 15 wt% (however, the contents of W and Mo Is 1.8 to 15 wt% in total), (Ti, Zr, Hf, Nb, Ta): 0 to 3 wt%, V: 0 to 4 wt%, Co: 0 to 6 wt%, Si: 0 to Disclosed is a tool steel comprising 1.6 wt%, Mn: 0-2 wt%, Ni: 0-2.99 wt%, and S: 0-1 wt% with the balance being iron and inevitable impurities ing.
  • This document describes that the thermal conductivity is higher than that of conventional tool steel by using such a composition.
  • Patent Document 5 describes, in mass%, 0.35 ⁇ C ⁇ 0.50, 0.01 ⁇ Si ⁇ 0.19, 1.50 ⁇ Mn ⁇ 1.78, 2.00 ⁇ Cr ⁇ 3.05. , 0.51 ⁇ Mo ⁇ 1.25, 0.30 ⁇ V ⁇ 0.80, and 0.004 ⁇ N ⁇ 0.040, with the balance being made of Fe and inevitable impurities. Has been. This document describes that the thermal conductivity of the mold can be increased by using such a composition.
  • a molding tool constituted by a mold or a mold part alone or in combination has a portion that comes into contact with an object to be molded having a temperature higher than room temperature, it is exposed to a thermal cycle of temperature rise and fall during use. Depending on the application, high pressure may be applied. In order to withstand this severe thermal cycle, molds and mold parts are used in a quenched and tempered state.
  • the heating conditions during quenching depend on the steel composition, application, mold size, etc., but are often maintained at 1030 ° C. for about 1 to 3 hours.
  • industrially, “mixed loading” in which a large mold and a small mold are heated together during quenching is common. However, in the case of mixed loading, if the heating conditions during quenching are matched with a large mold, the small mold is excessively heated and the crystal grains become coarse.
  • Japanese Unexamined Patent Publication No. 2008-056882 Japanese Unexamined Patent Publication No. 2008-121032 Japanese Unexamined Patent Publication No. 2008-169411 Japanese National Table 2010-500471 Japanese Unexamined Patent Publication No. 2011-094168
  • An object of the present invention is to provide a molding tool composed of a mold and mold parts using the same.
  • the molding tool is It is composed of a mold or a mold part alone or in combination, and includes a portion that is in direct contact with a workpiece whose temperature is higher than room temperature.
  • At least one of the mold and the mold part is: 0.38 ⁇ C ⁇ 0.55 mass%, 0.003 ⁇ Si ⁇ 0.300 mass%, 0.70 ⁇ Mn ⁇ 1.80 mass%, 0.80 ⁇ Cr ⁇ 2.00 mass%, 0.003 ⁇ Cu ⁇ 1.200 mass%, 0.003 ⁇ Ni ⁇ 1.380 mass%, 0.500 ⁇ Mo ⁇ 3.500 mass%, 0.55 ⁇ V ⁇ 1.20 mass%, and 0.0002 ⁇ N ⁇ 0.1200 mass%
  • the balance consists of Fe and inevitable impurities, 0.550 ⁇ Cu + Ni + Mo ⁇ 3.600 mass% Made of mold steel that satisfies Hardness is 33HRC more than 57HRC, Old austenite grain size number at the time of quenching is 5 or more,
  • the thermal conductivity ⁇ at 25 ° C. measured using a laser flash method is more than 27.0 [W / m / K].
  • the mold steel according to the present invention is: 0.38 ⁇ C ⁇ 0.55 mass%, 0.003 ⁇ Si ⁇ 0.300 mass%, 0.70 ⁇ Mn ⁇ 1.80 mass%, 0.80 ⁇ Cr ⁇ 2.00 mass%, 0.003 ⁇ Cu ⁇ 1.200 mass%, 0.003 ⁇ Ni ⁇ 1.380 mass%, 0.500 ⁇ Mo ⁇ 3.500 mass%, 0.55 ⁇ V ⁇ 1.20 mass%, and 0.0002 ⁇ N ⁇ 0.1200 mass%
  • the balance consists of Fe and inevitable impurities, 0.550 ⁇ Cu + Ni + Mo ⁇ 3.600 mass%
  • the gist is to satisfy.
  • the mold steel according to the present invention has excellent high-temperature strength and corrosion resistance, high quenching productivity, high thermal conductivity, and can generate fine austenite crystal grains during quenching.
  • FIG.2 (a) is a structure
  • FIG.2 (b) is a structure
  • the mold steel according to the present invention contains the following elements, with the balance being Fe and inevitable impurities.
  • the kind of additive element, its component range, and the reason for limitation are as follows.
  • the amount of Si when the amount of Si becomes excessive, the decrease in thermal conductivity increases.
  • the steel for molds according to the present invention has a relatively large amount of V, V-based carbides are likely to crystallize during casting, and this must be dissolved in the subsequent heat treatment.
  • the amount of Si if the amount of Si is excessive, the V-based crystallized carbide tends to be large and difficult to be dissolved.
  • the V-type crystallized carbide remaining without being dissolved is harmful since it becomes a starting point of destruction during use as a mold.
  • the amount of Si when the amount of Si becomes excessive, the problem that segregation of other elements becomes remarkable at the time of casting tends to occur. Therefore, the amount of Si needs to be less than 0.300 mass%.
  • the amount of Si is preferably less than 0.230 mass%, more preferably less than 0.190 mass%.
  • the mold steel according to the present invention has relatively little Cr. Therefore, if the amount of Mn is small, the hardenability is insufficient, and the toughness is reduced due to the mixing of bainite. Therefore, the amount of Mn needs to be more than 0.70 mass%.
  • the amount of Mn is preferably more than 0.75 mass%, more preferably more than 0.87 mass%.
  • the amount of Mn becomes excessive, the decrease in thermal conductivity is large.
  • the amount of Mn becomes excessive segregation becomes remarkable at the time of casting. Therefore, the amount of Mn needs to be less than 1.80 mass%.
  • the amount of Mn is preferably less than 1.78 mass%, more preferably less than 1.76 mass%.
  • the Cr amount needs to be 0.80 mass% or more.
  • the amount of Cr is preferably more than 0.85 mass%, more preferably more than 0.90 mass%.
  • the Cr amount needs to be less than 2.00 mass%.
  • the amount of Cr is more preferably less than 1.99 mass%.
  • the amount of Cu needs to be 0.003 mass% or more.
  • the amount of Cu is preferably 0.004 mass% or more, and more preferably 0.005 mass% or more.
  • the amount of Cu needs to be less than 1.200 mass%.
  • the amount of Cu is preferably less than 1.170 mass%, more preferably less than 1.150 mass%, and even more preferably 0.7 mass% or less. When the amount of Cu is 0.7 mass% or less, it is possible to avoid an excessive decrease in annealing and thermal conductivity while exhibiting a great drag effect.
  • Ni has a large drag effect like Cu, it can be added for the purpose of maintaining fine grains during quenching.
  • Cu may impair hot workability
  • Ni not only does not impair hot workability but also has an effect of restoring deterioration of hot workability due to the addition of Cu.
  • Ni has an effect of increasing the strength by bonding with Al when Al is present, and the effect of increasing the strength is poor when the amount of Ni is small. Further, it is not impossible to reduce Ni more than necessary by careful selection of raw materials, but it causes a significant increase in cost. Therefore, the amount of Ni needs to be 0.003 mass% or more.
  • the amount of Ni is preferably 0.004 mass% or more, and more preferably 0.005 mass% or more.
  • the amount of Ni needs to be less than 1.380 mass%.
  • the amount of Ni is preferably less than 1.250 mass%, more preferably less than 1.150 mass%, and even more preferably 0.7 mass% or less.
  • the amount of Ni is preferably 0.3 to 1.2 times the amount of Cu.
  • the amount of Ni is not necessarily 0.3 to 1.2 times the amount of Cu. .
  • Mo has a relatively large drag effect like Cu and Ni, it can be added for the purpose of maintaining fine grains during quenching. Mo also has an advantage that hot workability is not impaired like Cu.
  • the amount of Mo is small, (a) the drag effect is small, (b) the contribution of secondary curing is small, and when the tempering temperature is high, it is difficult to stably obtain a hardness exceeding 33 HRC. ) Problems such as a small effect of improving the corrosion resistance by the combined addition with Cr occur. Therefore, the Mo amount needs to be more than 0.500 mass%.
  • the amount of Mo is preferably more than 0.530 mass%, more preferably more than 0.560 mass%.
  • the Mo amount needs to be less than 3.500 mass%.
  • the amount of Mo is preferably less than 3.400 mass%, more preferably less than 3.300 mass%.
  • the V amount In order to maintain fine particles during quenching, it is necessary to use both the drag effect of solid solution elements and the pinning effect of dispersed particles. It is preferable to optimize the V amount in consideration of the C amount so that the VC of the dispersed particles becomes an appropriate amount. When the amount of V is small, the amount of VC is small, so that the effect of suppressing the coarsening of the ⁇ crystal grains (the crystal grain size number becomes small) is poor. Therefore, the V amount needs to be more than 0.55 mass%.
  • the amount of V is preferably more than 0.56 mass%, more preferably more than 0.57 mass%, still more preferably more than 0.7 mass%. When the amount of V is more than 0.7 mass%, the crystal grains are very fine and preferable grain size number 8 or more.
  • the V amount needs to be less than 1.20 mass%.
  • the amount of V is preferably less than 1.16 mass%, more preferably less than 1.13 mass%.
  • the present invention has a V amount and (Cu + Ni + Mo) amount that do not exist in the past, and positively provides a drag effect of solid solution elements and a pinning effect of dispersed particles. The feature is that it is used together.
  • N also affects the amount of dispersed particles VC. As the amount of N increases, the solid solution temperature of VC increases. Therefore, even if the amount of C and V is the same, the residual VC at the time of quenching increases. When the amount of N is small, VC particles at the time of quenching are excessively reduced. Therefore, the effect of suppressing the coarsening of the ⁇ crystal grains (decreasing the crystal grain size number) is poor. In addition, N has an effect of assisting in preventing coarsening of the crystal grains by forming AlN particles when Al is present, but such an effect is small when the amount of N is small. Therefore, the N amount needs to be 0.0002 mass% or more. The amount of N is preferably more than 0.0010 mass%, more preferably more than 0.0030 mass%.
  • the N amount needs to be less than 0.1200 mass%.
  • the amount of N is preferably less than 0.1000 mass%, more preferably less than 0.0800 mass%.
  • the mold steel according to the present invention is an inevitable impurity, P ⁇ 0.05 mass%, S ⁇ 0.003 mass%, Al ⁇ 0.10 mass%, W ⁇ 0.30 mass%, O ⁇ 0.01 mass%, Co ⁇ 0.10 mass%, Nb ⁇ 0.004 mass%, Ta ⁇ 0.004 mass%, Ti ⁇ 0.004 mass%, Zr ⁇ 0.004 mass%, B ⁇ 0.0001 mass%, Ca ⁇ 0.0005 mass%, Se ⁇ 0.03 mass%, Te ⁇ 0.005 mass%, Bi ⁇ 0.01 mass%, Pb ⁇ 0.03 mass%, Mg ⁇ 0.02 mass%, or REM ⁇ 0.10 mass% May be included.
  • the mold steel according to the present invention may contain one or more elements as described above.
  • the content of the element is not more than the above upper limit value, the element behaves as an inevitable impurity.
  • a part of the element may be contained exceeding the upper limit. In this case, the effects described below are obtained depending on the type and content of the element.
  • the mold steel according to the present invention is characterized in that the total amount of Cu, Ni and Mo satisfies the relationship of the following formula (a). 0.550 ⁇ Cu + Ni + Mo ⁇ 3.600 mass% (a)
  • the amount of Cu + Ni + Mo is important. If the total amount of these elements is small, a sufficient drag effect cannot be obtained. Therefore, the total amount of these elements needs to be more than 0.550 mass%. The total amount is preferably greater than 0.600 mass%, more preferably greater than 0.700 mass%. On the other hand, if the total amount of these elements is excessive, it may cause cracking during hot working, decrease in thermal conductivity, decrease in toughness due to excessive precipitation of intermetallic compounds, decrease in fracture toughness, and the like. Therefore, the total amount of these elements needs to be less than 3.600 mass%. The total amount is preferably less than 3.550 mass%, more preferably less than 3.500 mass%, and still more preferably 2.000 mass% or less.
  • the mold steel according to the present invention may further contain one or more elements as described below.
  • the kind of additive element, its component range, and the reason for limitation are as follows.
  • W or Co is effective to obtain a stable and fine ⁇ crystal grain by combining the pinning effect of VC particles and the drag effect of solute atoms.
  • the amount of W and the amount of Co each preferably exceed the lower limit values described above.
  • the W amount and the Co amount are each preferably not more than the above upper limit value.
  • either one of W or Co may be contained in the steel for metal mold
  • Nb, Ta, Ti, and / or Zr may be selectively added. When these elements are added, these elements form fine precipitates. The fine precipitates suppress the movement of the ⁇ grain boundary (pinning effect), so that a fine austenite structure can be maintained. In order to obtain such an effect, the amount of these elements is preferably an amount exceeding the above lower limit value.
  • the amount of these elements is preferably not more than the above upper limit value.
  • the mold steel may contain any one of these elements, or Two or more kinds may be included.
  • Al combines with N to form AlN and has the effect of suppressing the growth of ⁇ crystal grains (pinning effect).
  • Al has a high affinity with N and accelerates the penetration of N into the steel. For this reason, when a steel material containing Al is subjected to nitriding treatment, the surface hardness tends to increase. It is effective to use a steel material containing Al for a mold for nitriding for higher wear resistance.
  • the amount of Al is preferably more than 0.10 mass%.
  • the amount of Al is preferably 1.50 mass% or less. Even if the Al amount is an impurity level (0.10 mass% or less), the above effect may be exhibited depending on the N amount.
  • nitride may be formed with an element having an affinity for N that is greater than that of B to suppress the bond between B and N.
  • examples of such elements include Nb, Ta, Ti, and Zr described above. These elements have an effect of fixing N even when present at an impurity level (0.004 mass% or less), but depending on the amount of N, an amount exceeding the impurity level may be added. Even if a part of B is combined with N in steel to form BN, if surplus B exists alone in the steel, it enhances hardenability.
  • B is also effective in improving machinability.
  • BN may be formed.
  • BN is similar in nature to graphite and lowers cutting resistance while improving chip friability.
  • the amount of B is preferably more than 0.0001 mass%.
  • the amount of B is preferably 0.0050 mass% or less.
  • the amount of these elements is preferably an amount exceeding the above lower limit value.
  • the amount of these elements is preferably not more than the above upper limit value.
  • any 1 type of these elements may be contained in the steel for metal mold
  • the mold is required to be difficult to wear or deform. Therefore, the mold needs to have hardness. If the hardness exceeds 33 HRC, the problem of wear or deformation hardly occurs even when applied to various uses.
  • the hardness is more preferably 35 HRC or more.
  • the hardness needs to be 57 HRC or less.
  • the hardness is more preferably 56 HRC or less. This point is the same for the mold parts, and the hardness is preferably within the above range.
  • the austenite grain size number at the time of quenching needs to be 5 or more.
  • the austenite grain size number is more preferably 5.5 or more.
  • the crystal grain size number is 6 or more, or 6.5 or more. This is the same for mold parts, and the prior austenite grain size number is preferably within the above range.
  • thermal conductivity In order to reduce product damage (seizure, cracking, wear) by cooling the product quickly or reducing the temperature of the die or reducing thermal stress, it is necessary to increase the thermal conductivity of the die.
  • the thermal conductivity ⁇ at 25 ° C. of general-purpose steel used for die casting is 23.0 to 24.0 [W / m / K]. Even in steel with high thermal conductivity, ⁇ is 27.0 [W / m / K] or less, which is insufficient. In order to cool the product quickly or reduce mold damage, the thermal conductivity ⁇ needs to exceed 27.0 [W / m / K].
  • the thermal conductivity ⁇ is more preferably more than 27.5 [W / m / K].
  • thermal conductivity is 28.0 [W / m / K] or more, or 28.5 [W / m / K] or more. This is the same for mold parts, and the thermal conductivity is preferably within the above range.
  • thermal conductivity refers to a value at 25 ° C. measured using a laser flash method.
  • the forming tool has the following configuration.
  • the molding tool is It is composed of a mold or a mold part alone or in combination, and includes a portion that is in direct contact with a workpiece whose temperature is higher than room temperature.
  • At least one of the mold and the mold part is made of mold steel according to the present invention.
  • At least one of the mold and the mold part is: Hardness is 33HRC more than 57HRC, Old austenite grain size number at the time of quenching is 5 or more,
  • the thermal conductivity ⁇ at 25 ° C. measured using a laser flash method is more than 27.0 [W / m / K].
  • the molding tool according to the present invention is used for processing a molding having a temperature higher than room temperature.
  • processing include die casting, plastic injection molding, rubber processing, various castings, warm forging, hot forging, and hot stamping.
  • molding tool (A) a mold having a portion in direct contact with a workpiece having a temperature higher than room temperature; and (B) It is configured by a single or a combination of mold parts having a portion that is in direct contact with a molding whose temperature is higher than room temperature, and plays a role of molding the molding into a predetermined shape.
  • the “mold” refers to a part other than a mold part, a mold part, and a part (for example, a mold fastener) that does not have a portion in direct contact with a molding object. For example, in the case of die casting, there are molds on the movable side and the fixed side, respectively.
  • the nesting is handled as a mold part to be described later.
  • the “mold component” refers to a component that plays a role of molding a workpiece having a temperature higher than room temperature into a predetermined shape, alone or in combination with the mold. Therefore, for example, bolts and nuts for fastening the mold are not included in the “mold part” in the present invention.
  • the present invention is characterized by high thermal conductivity, and one of the objects is to quickly cool a die cast, hot stamp or injection molded product. Therefore, a mold part having a portion in contact with a molten metal, a heated steel plate, or a molten resin is an application target of the present invention.
  • mold parts include a plunger tip, a spool bush, a spool core (a diverter), a shot pin, a chill vent, and a nest. These mold parts are sometimes called molds in a broad concept.
  • the molding may be a melt or a semi-melt, and may be a solid.
  • the temperature of a to-be-molded object changes with uses of a molding tool.
  • the temperature of the object to be molded molten metal
  • the temperature of the workpiece (molten plastic) is usually 70 to 400 ° C. in a kneader.
  • the temperature of the molding unvulcanized rubber
  • the heating temperature of the molding (steel material) is usually 150 to 800 ° C.
  • the heating temperature of the molding (steel material) is usually 800 to 1350 ° C.
  • the heating temperature of the molded product (steel plate) is usually 800 to 1050 ° C.
  • a die-casting die or its component is demonstrated to an example.
  • the die casting mold is used in a quenching and tempering state.
  • the heating conditions for quenching are often quenching temperature: 1030 ° C. and holding time at quenching temperature: 1 to 3 Hr.
  • the die-casting steel sometimes becomes an austenite single phase, but generally has a mixed structure of austenite and residual carbide. Thereafter, austenite is transformed into a structure mainly composed of martensite by cooling, and hardness and toughness are imparted by combination with tempering. This is because the mold requires hardness to ensure erosion resistance and toughness to ensure crack resistance.
  • the austenite grain size number during quenching is large (the austenite crystal grain size is small). This is because cracks are less likely to propagate when the crystal grains are finer, and the effect of suppressing cracks in the mold is greater.
  • the austenite grain size number at the time of quenching is determined by the heating temperature and the holding time. The austenite grain size number becomes large (crystal grains become fine) when the heating temperature is low and the holding time is short. For this reason, care is taken in quenching so that the heating temperature does not become excessively high and the holding time does not become excessively long.
  • a technique of dispersing residual carbides in austenite may be employed.
  • it is set as the steel of the component system which optimized C amount and the amount of carbide forming elements.
  • Residual carbide has an effect of suppressing the movement of austenite grain boundaries by pinning (pinning effect), and as a result, coarsening of austenite crystal grains is prevented (a large grain size number is maintained).
  • FIG. 1 shows a schematic diagram of changes in furnace temperature and mold temperature during mixed heating. As described above, the heating time at the quenching temperature requires about 1 to 3 hours. At the time of mixed loading, a holding time of the furnace temperature is given so that a large mold meets this condition. If it does so, the small metal mold
  • the thermal conductivity ⁇ of SKD61 which is a general-purpose steel for die casting molds, at 25 ° C. is 23.0 to 24.0 [W / m / K], whereas the thermal conductivity of steel considered to have high thermal conductivity. ⁇ is 24.0 to 27.0 [W / m / K].
  • the Cr content is significantly lower than the Cr content (about 5%) of general hot die steel.
  • the amount of Cr is low (0.5% ⁇ Cr ⁇ 5%), and even when held at 1030 ° C. for 5 hours, the austenite grain size number is 5 or more. If the steel has thermal conductivity exceeding 27.0 [W / m / K] and high temperature strength and corrosion resistance that can withstand practical use, the following three points can be realized simultaneously. (1) Improvement in hardenability productivity (can be mixed for quenching at 1030 ° C. for large molds). (2) Reduction of die casting cycle time and reduction of mold seizure (high thermal conductivity). (3) Prevention of cracking of die casting mold (fine austenite during quenching). However, at present, such steel does not exist. There is a strong industry need for high thermal conductivity steel that is difficult to coarsen during quenching.
  • the amounts of C, V and N related to VC particles which suppress the grain boundary movement of crystal grains by a pinning effect are set. Optimized. In particular, the amount of V is important. Furthermore, in order to make the austenite crystal grains fine at the time of quenching, the amounts of Cu, Ni, and Mo, which are solid solution elements that suppress the movement of crystal grain boundaries by the drag effect, were optimized. In particular, the amount of (Cu + Ni + Mo) is important.
  • a major feature of the present invention is that the pinning effect and the drag effect are positively used together, and the amount of V and the amount of (Cu + Ni + Mo) are in an unprecedented balance.
  • the addition of Ni is effective.
  • the addition of Ni is limited to an amount that does not significantly reduce the thermal conductivity when the mold is formed.
  • the steel for molds according to the present invention has an austenite grain size number of 5 or more even when quenched at 1030 ° C. for 5 hours. Therefore, the toughness after quenching and tempering is high, and cracking of the mold can be prevented. Moreover, since the steel for molds according to the present invention has a thermal conductivity exceeding 27.0 [W / m / K] after quenching and tempering, it is possible to realize a reduction in die casting cycle time and seizure. Furthermore, since a maximum hardness of 57 HRC is obtained after quenching and tempering, it is also resistant to wear due to die casting injection. High hardness is preferable because high wear resistance can be obtained even when applied to a hot stamping mold.
  • the mold steel according to the present invention contains Cr, it has corrosion resistance that can withstand practical use. Therefore, rust hardly occurs during storage of materials and use as a mold, compared with steel containing almost no Cr (Cr ⁇ 0.5%).
  • FIG. 2 (a) shows a structure photograph of Cu-free steel (steel A) that was quenched at 1030 ° C. ⁇ 5Hr and then quenched.
  • FIG. 2 (b) shows a structure photograph of the Cu-added steel (steel B) that was quenched at 1030 ° C. ⁇ 5Hr and then quenched.
  • the composition of steel A is 0.04C-0.05Si-1.58Mn-1.93Cr-1.10Mo-0.81V-0.020N.
  • Steel B is obtained by adding 1.120 mass% Cu to steel A.
  • Fig. 2 is a comparison of the structures in which the former ⁇ grain boundaries appeared after quenching.
  • Quenching temperature At 1030 ° C., VC particles are dispersed in steel A and steel B, and the amount of VC particles is approximately the same in steel A and steel B. Therefore, the growth of ⁇ grains is suppressed by the pinning effect of the crystal grain boundaries caused by the VC grains.
  • FIG. 1 when the holding at 1030 ° C. reaches 5 hours, the pinning effect is weakened due to the decrease due to the solid solution of the VC particles, and the driving force of the extremely large grain boundary movement is stopped. I can't do that.
  • the ⁇ grain size of Steel A was 100 to 200 ⁇ m (crystal grain size number: 2 to 4).
  • the ⁇ crystal grain size of steel B is about 15 ⁇ m (the crystal grain size number is about 9).
  • 1.120% of Cu is all dissolved in ⁇ .
  • This solid solution Cu suppresses the movement of the ⁇ grain boundary by the “solute drag effect” and maintains a very fine ⁇ structure together with pinning of the ⁇ grain boundary by VC particles. It can be judged.
  • solid solution Cu has a strong drag effect, and a fine grain structure can be stably obtained by combining with the pinning effect by dispersed particles. This is the greatest feature of the present invention.
  • comparative example 1 is the general-purpose steel JIS SKD61 of a die-casting die.
  • Comparative Example 2 is also a hot die steel, but is a commercially available brand steel.
  • Comparative Examples 3 and 4 are JIS SNCM439 and JIS SCM435, respectively.
  • Comparative Example 5 is a brand steel marketed as a high thermal conductivity steel.
  • Table 2 shows the crystal grain size numbers.
  • FIG. 3 shows the relationship between the amount of (Cu + Ni + Mo) and the ⁇ grain size number during quenching.
  • FIG. 4 shows the relationship between the V amount and the ⁇ grain size number at the time of quenching.
  • the crystal grain size numbers of Comparative Examples 1 and 2 are as large as about 10, and the austenite at the time of quenching is very fine.
  • Comparative Example 3 since both the V amount and the (Cu + Ni + Mo) amount are small, the crystal grain size number is about 2 and coarse particles. Since Comparative Example 4 and Comparative Example 5 had poor hardenability, ferrite precipitated. The amount of ferrite is greater in Comparative Example 5.
  • the crystal grain size numbers of Examples 1 to 25 stably exceed 5.
  • the grain size number tends to increase, and the drag effect (FIG. 3) and the pinning effect (FIG. 4) overlap. I understand.
  • Table 3 shows the hardness after tempering.
  • Comparative Example 4 ferrite was precipitated during quenching and softening resistance was low, so that it was about 27 HRC, and the hardness required for the mold: more than 33 HRC could not be secured.
  • Comparative Example 5 also had a low hardness ( ⁇ 20 HRC) that cannot be measured by HRC because a large amount of ferrite precipitated during quenching. It can be seen that using Comparative Example 4 and Comparative Example 5 for die-cast mold parts is virtually impossible from the viewpoint of hardenability and softening resistance.
  • Comparative Example 1 and Comparative Example 2 were only used for die casting molds and could be tempered to 47HRC without problems. In addition, it was confirmed that all of Examples 1 to 25 could be tempered to 47 HRC and could be applied to a die casting mold from the viewpoint of hardenability and softening resistance.
  • Table 4 shows the thermal conductivity of the materials shown in Table 3. Since the comparative example 1 has many Si and Cr, it has the lowest thermal conductivity. Comparative Example 2 has a higher thermal conductivity than Comparative Example 1 due to extremely low Si, but remains at ⁇ ⁇ 27.0 due to the large amount of Cr. Since Comparative Examples 3 to 5 are low Si and low Cr, they have high thermal conductivity of ⁇ > 27.0.
  • Table 5 summarizes the above survey results. The austenite grain size number when heated at 1030 ° C. ⁇ 5 Hr, the hardness in the quenched and tempered state, and the thermal conductivity are summarized. In Comparative Examples 4 and 5, the tempering hardness required for the mold: more than 33 HRC could not be obtained. Other steels could be tempered to 47HRC except for Comparative Example 3. In Table 5, “ ⁇ ” means that the target has been achieved and is good, and “ ⁇ ” means that the target has not been reached and is inferior.
  • Comparative Examples 1 to 5 there is “x” in any item. Comparative Example 1 and Comparative Example 2 have low thermal conductivity. Comparative Examples 3 to 5 have a small crystal grain size number (large crystal grains). In Comparative Examples 1 and 2 with low thermal conductivity, it is difficult to reduce damage to the mold and quickly cool the product when the die-cast mold is formed. In Comparative Examples 3 to 5, there is a concern that large cracks may occur when die casting molds are obtained. Moreover, since Comparative Examples 4 and 5 have low hardenability, it is difficult to apply them to a die casting mold.
  • the austenite crystal grains at the time of quenching are as fine as a grain size number of 5 or more, and have a high thermal conductivity exceeding 27 [W / m / K] in a tempered state of 47 HRC.
  • the following three points can be realized simultaneously. (1) Improvement in hardenability productivity (can be mixed for quenching at 1030 ° C. for large molds). (2) Reduction of die casting cycle time and reduction of mold seizure (high thermal conductivity). (3) Prevention of cracking of die casting mold (fine austenite during quenching).
  • the mold steel according to the present invention is suitable for die casting molds or parts thereof because austenite crystal grains are hard to be coarsened during quenching and high hardness and high thermal conductivity are obtained after tempering.
  • the die steel according to the present invention is applied to a die casting die or a part thereof, it is possible to suppress cracking or seizure of the die or the part thereof and to shorten the die casting cycle time.
  • the steel for molds according to the present invention can be made into a rod shape or a line shape and used as a welding repair material for the mold or its parts. Or it is also applicable to the metal mold

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Abstract

L'invention concerne un acier pour des moules qui contient 0,38 % en masse < C < 0,55 % en masse, 0,003 % en masse ≤ Si < 0,300 % en masse, 0,70 % en masse < Mn < 1,80 % en masse, 0,80 % en masse ≤ Cr < 2,00 % en masse, 0,003 % en masse ≤ Cu < 1,200 % en masse, 0,003 % en masse ≤ Ni < 1,380 % en masse, 0,500 % en masse < Mo < 3,500 % en masse, 0,55 % en masse < V < 1,20 % en masse et 0,0002 % en masse ≤ N < 0,1200 % en masse, le reste étant constitué de Fe et d'impuretés inévitables, et cet acier pour moules satisfait à la relation 0,550 % en masse < (Cu + Ni + Mo) < 3,600 % en masse. La présente invention concerne également un outil de moulage qui comprend un moule et/ou un élément de moule qui est formé à partir de cet acier pour des moules.
PCT/JP2016/075518 2015-09-02 2016-08-31 Acier pour moules et outil de moulage Ceased WO2017038879A1 (fr)

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CN109609856A (zh) * 2019-02-22 2019-04-12 无锡宏达重工股份有限公司 优化42CrMo低温冲击吸收功的热处理工艺
EP3483295A1 (fr) * 2017-11-14 2019-05-15 Daido Steel Co.,Ltd. Matériau de réparation-soudage pour puce
JP2020015927A (ja) * 2018-07-23 2020-01-30 山陽特殊製鋼株式会社 耐衝撃性に優れた機械構造用合金鋼
TWI687524B (zh) * 2018-04-02 2020-03-11 日商大同特殊鋼股份有限公司 模具用鋼材及模具
CN111945080A (zh) * 2020-08-27 2020-11-17 靖江市钜顺精密轻合金成型科技有限公司 一种高寿命压铸模具钢及制造铝镁压铸模的工艺方法
CN113122779A (zh) * 2021-04-26 2021-07-16 江苏沙钢集团淮钢特钢股份有限公司 一种细晶粒免正火工具钢及其生产方法
CN113462985A (zh) * 2021-07-16 2021-10-01 鞍钢股份有限公司 免退火折弯性能优异的低成本高表面硬度工具钢
CN114888090A (zh) * 2022-05-16 2022-08-12 湖北腾升科技股份有限公司 高硬度高镍铬钼复合轧辊结构

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JP7608772B2 (ja) * 2019-12-03 2025-01-07 大同特殊鋼株式会社 金型用鋼及び金型
JP7532824B2 (ja) 2020-03-16 2024-08-14 株式会社プロテリアル 熱間加工用金型用鋼、熱間加工用金型およびその製造方法
CN116891978A (zh) * 2023-09-11 2023-10-17 宁波众远新材料科技有限公司 一种铝合金冲压模具钢及其制备方法

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EP3483295A1 (fr) * 2017-11-14 2019-05-15 Daido Steel Co.,Ltd. Matériau de réparation-soudage pour puce
TWI687524B (zh) * 2018-04-02 2020-03-11 日商大同特殊鋼股份有限公司 模具用鋼材及模具
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JP2020015927A (ja) * 2018-07-23 2020-01-30 山陽特殊製鋼株式会社 耐衝撃性に優れた機械構造用合金鋼
JP7176877B2 (ja) 2018-07-23 2022-11-22 山陽特殊製鋼株式会社 耐衝撃性に優れた機械構造用合金鋼
CN109609856A (zh) * 2019-02-22 2019-04-12 无锡宏达重工股份有限公司 优化42CrMo低温冲击吸收功的热处理工艺
CN111945080A (zh) * 2020-08-27 2020-11-17 靖江市钜顺精密轻合金成型科技有限公司 一种高寿命压铸模具钢及制造铝镁压铸模的工艺方法
CN113122779A (zh) * 2021-04-26 2021-07-16 江苏沙钢集团淮钢特钢股份有限公司 一种细晶粒免正火工具钢及其生产方法
CN113122779B (zh) * 2021-04-26 2022-06-07 江苏沙钢集团淮钢特钢股份有限公司 一种细晶粒免正火工具钢及其生产方法
CN113462985A (zh) * 2021-07-16 2021-10-01 鞍钢股份有限公司 免退火折弯性能优异的低成本高表面硬度工具钢
CN114888090A (zh) * 2022-05-16 2022-08-12 湖北腾升科技股份有限公司 高硬度高镍铬钼复合轧辊结构
CN114888090B (zh) * 2022-05-16 2024-05-07 湖北腾升科技股份有限公司 高硬度高镍铬钼复合轧辊结构

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