WO2016136401A1 - 熱間工具およびその製造方法 - Google Patents
熱間工具およびその製造方法 Download PDFInfo
- Publication number
- WO2016136401A1 WO2016136401A1 PCT/JP2016/053019 JP2016053019W WO2016136401A1 WO 2016136401 A1 WO2016136401 A1 WO 2016136401A1 JP 2016053019 W JP2016053019 W JP 2016053019W WO 2016136401 A1 WO2016136401 A1 WO 2016136401A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- hot
- hot tool
- quenching
- tool
- less
- Prior art date
Links
Images
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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/01—Selection of materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D37/00—Tools as parts of machines covered by this subclass
- B21D37/20—Making tools by operations not covered by a single other subclass
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J13/00—Details of machines for forging, pressing, or hammering
- B21J13/02—Dies or mountings therefor
-
- 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
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- 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
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- 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
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
-
- 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
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
-
- 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
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- 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
- C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
-
- 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
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
- B22D17/20—Accessories: Details
- B22D17/22—Dies; Die plates; Die supports; Cooling equipment for dies; Accessories for loosening and ejecting castings from dies
-
- 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
- C21D2211/001—Austenite
-
- 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
- C21D2211/008—Martensite
Definitions
- the present invention relates to various hot tools such as a press die, a forging die, a die casting die, and an extrusion tool, and a manufacturing method thereof.
- hot tools Since hot tools are used in contact with high-temperature workpieces and hard workpieces, they must have toughness that can withstand impacts.
- SKD61 series alloy tool steel which is a JIS steel type, is used as a hot tool material.
- alloy tool steel materials with improved component composition of the above SKD61-based alloy tool steel have been proposed as hot tool materials (Patent Documents 1 and 2). ).
- a hot tool is usually manufactured by machining a hot tool material in an annealed state with low hardness into the shape of a hot tool, and then quenching and tempering it to adjust it to a predetermined working hardness. Is done. Further, it is common to perform finishing machining after the use hardness is adjusted. In some cases, the hot tool material is first quenched and tempered (so-called pre-hardened material) and then machined to the shape of the hot tool with the finishing machining described above. Sometimes it is done. Quenching means heating the hot tool material in the annealed state (or the hot tool material after the hot tool material is machined) to the austenite temperature range and holding it, and then rapidly cooling it. , Work to transform the organization into martensite.
- the component composition of the hot tool material can be adjusted to a martensite structure by quenching.
- the grain boundaries of the austenite crystal grains generated in the process of heating and holding to the austenite temperature range are confirmed as “old austenite grain boundaries”.
- the distribution of the “old austenite grain size” formed at the prior austenite grain boundaries is substantially maintained even in the metal structure after the next tempering (that is, the structure of the finished hot tool). ing.
- the toughness of the hot tool can be improved by reducing the content of inevitable impurities such as P, S, O, and N contained in the component composition. ing.
- P is an element that segregates at the prior austenite grain boundaries in the martensite structure after quenching and tempering, embrittles the grain boundaries, and greatly reduces the toughness of the hot tool. Therefore, it has been proposed to limit the P content in the hot tool material (that is, the hot tool) to, for example, 0.020 mass% or less (Patent Document 3).
- the toughness of a hot tool can be improved by reducing the prior austenite grain size in the martensite structure (Patent Document 3).
- Reducing the P content contained in the hot tool is very effective for improving the toughness of the hot tool after quenching and tempering.
- P in the hot tool material is removed by a refining process or the like, a large amount of energy is consumed. And removal of P by this refining process etc., on the other hand, has also become a factor that stagnates the promotion of use of low-grade scrap having a high P content.
- P to be reduced is an element with a large environmental load.
- An object of the present invention is to provide a hot tool that can maintain sufficient toughness even if the allowable amount of P content contained in the hot tool is increased.
- the present invention has a component composition that can be adjusted to a martensite structure by quenching, and in a hot tool having a martensite structure after quenching and tempering, Said component composition contains more than 0.020 mass% and 0.050 mass% or less P,
- the grain size of the prior austenite grains in the martensite structure after quenching and tempering is a grain size number according to JIS-G-0551, 9.5 or more,
- This hot tool has a P concentration at the grain boundary of the prior austenite grains of 1.5% by mass or less.
- it is a hot tool in which the above component composition further contains 0.0250% by mass or less of Zn.
- the present invention performs quenching and tempering on a hot tool material having a component composition that can be adjusted to a martensite structure by quenching.
- the component composition of the hot tool material described above includes 0.020 mass% and 0.050 mass% or less of P
- the grain size of the prior austenite grains in the martensite structure after the above quenching and tempering is the grain size number in accordance with JIS-G-0551, No. It is a manufacturing method of a hot tool which is 9.5 or more and the P concentration at the grain boundary of this prior austenite grain is 1.5% by mass or less.
- the component composition of the hot tool material further includes 0.0250% by mass or less of Zn.
- the toughness of the hot tool containing P of more than 0.020 mass% and 0.050 mass% or less can be sufficiently maintained.
- the present inventor has studied a technique that can sufficiently maintain the toughness of the hot tool even if the P content contained in the hot tool material is high.
- the prior austenite grain size It has been found that adjusting the "function" "directly” in suppressing the P segregation to the prior austenite grain boundaries.
- P allowable amount and “ The present invention has been reached by clarifying the specific relationship amount with the “old austenite grain size”. Below, each component of this invention is demonstrated.
- the hot tool of the present invention is “having a component composition that can be adjusted to a martensite structure by quenching and having a martensite structure after quenching and tempering”.
- a hot tool is produced by quenching and tempering a hot tool material in an annealed state.
- This hot tool material having an annealed structure is made of a steel ingot or a material made of a steel piece obtained by dividing a steel ingot, and is subjected to various hot working and heat treatments to obtain a predetermined steel material.
- the steel material is annealed and finished, for example, in a block shape.
- tissue by quenching and tempering is conventionally used for the hot tool material.
- the martensite structure is a structure necessary for basing the absolute toughness of various hot tools.
- a raw material of such a hot tool that is, a hot tool material
- various hot tool steels are typical.
- Hot tool steel is used in an environment where the surface temperature is raised to approximately 200 ° C. or higher.
- the component composition of the hot tool steel for example, standard steel types in “Alloy Tool Steel” in JIS-G-4404 and other proposed steels can be representatively applied.
- element types other than those specified in the hot tool steel can be added or contained as necessary.
- the quenching and tempering structure is the requirement of (3) described later. Satisfying this can be achieved. Therefore, the above-described effect of the present invention can be achieved except that an “allowable value (lower limit)” of the P content of the hot tool is set in order to make the effect of suppressing the P segregation of the present invention meaningful. Therefore, it is not necessary to specify the component composition of the above-described material.
- the composition of the hot tool steel further includes V: 0.10 to 1.50%.
- Mo and W are used alone or in combination (Mo + 1 / 2W): hot containing 3.50% or less It preferably has a component composition of tool steel.
- the value of (Mo + 1 / 2W) is more preferably 0.50% or more. Specifically, C: 0.30 to 0.50%, Si: 2.00% or less, Mn: 1.50% or less, S: 0.0500% or less, Cr: 3.00 to 6. 00%, Mo and W are used alone or in combination (Mo + 1 / 2W): 0.50 to 3.50%, V: 0.10 to 1.50%, and a component composition containing P described later. It is preferable to have.
- the effect of suppressing the P segregation of the present invention acts synergistically with this, and a hot tool with better toughness can be obtained.
- Various elements that can constitute the component composition of the hot tool of the present invention will be described as follows.
- C 0.30 to 0.50 mass% (hereinafter simply expressed as “%”)
- C is a basic element of a hot tool that partly dissolves in the base to give strength and partly forms carbides to improve wear resistance and seizure resistance.
- C dissolved as interstitial atoms when added together with substitutional atoms having a high affinity with C, such as Cr, has an I (interstitial atom) -S (substitutional atom) effect (the drag resistance of solute atoms).
- the strength of the hot tool is increased).
- the content is preferably 0.30 to 0.50%. More preferably, it is 0.34% or more. Further, it is more preferably 0.40% or less.
- Si is a deoxidizer during steelmaking, but if it is too much, ferrite is generated in the tool structure after quenching and tempering. Therefore, it is preferable to set it as 2.00% or less. More preferably, it is 1.00% or less. More preferably, it is 0.50% or less. On the other hand, Si has the effect of increasing the machinability of the material. In order to obtain this effect, addition of 0.20% or more is preferable. More preferably, it is 0.30% or more.
- Mn has the effect of improving hardenability, suppressing the formation of ferrite in the tool structure, and obtaining appropriate quenching and tempering hardness. Moreover, since it exists as MnS of a nonmetallic inclusion, there is a great effect in improving machinability. In order to obtain these effects, Mn is preferably added in an amount of 0.10% or more. More preferably, it is 0.25% or more. More preferably, it is 0.45% or more.
- S 0.0500% or less
- S is an element that can be inevitably contained in various hot tools even if not added. And it is an element which degrades hot workability at the time of the raw material of a hot tool, and causes a crack in the raw material during hot working. Therefore, in order to improve the hot workability described above, it is preferable to limit the amount to 0.0500% or less.
- S has an effect of improving machinability by being bonded to Mn as described above and existing as MnS of non-metallic inclusions. In order to obtain this effect, 0.0300% or more is preferably added.
- ⁇ Cr 3.00 to 6.00% Cr is an element that enhances hardenability and forms carbides, and is effective in strengthening the base and improving wear resistance. And it is a basic element of a hot tool which contributes to the improvement of temper softening resistance and high temperature strength. However, excessive addition causes a decrease in high temperature strength. In addition, the hardenability is reduced. Therefore, the content is preferably 3.00 to 6.00%. And it is 5.50% or less more preferably. Further, it is more preferably 3.50% or more. More preferably, it is 4.00% or more. Particularly preferably, it is 4.50% or more.
- Mo and W are single or composite (Mo + 1 / 2W): 0.50 to 3.50% Mo and W are elements that give strength and softening resistance to the hot tool by precipitating or agglomerating fine carbides in the structure by tempering. Mo and W can be added alone or in combination. The addition amount at this time can be specified together by the Mo equivalent defined by the formula of (Mo + 1 / 2W) since W is an atomic weight approximately twice that of Mo. Of course, only one of them may be added, or both may be added together. And in order to acquire said effect, 0.50% or more of addition is preferable by the value of (Mo + 1 / 2W). More preferably, it is 1.50% or more. More preferably, it is 2.50% or more. However, since too much will lead to a decrease in machinability and toughness, the value of (Mo + 1 / 2W) is preferably 3.50% or less. More preferably, it is 2.90% or less.
- V 0.10 to 1.50%
- V has the effect of forming carbides and improving the strength of the base, wear resistance, and temper softening resistance.
- tissue works as "pinning particle
- addition of 0.10% or more is preferable. More preferably, it is 0.30% or more. More preferably, it is 0.50% or more. However, if it is too much, machinability and toughness decrease due to an increase in the carbide itself are caused, so it is preferable to be 1.50% or less. More preferably, it is 1.00% or less. More preferably, it is 0.70% or less.
- the component composition of the hot tool of the present invention can be the component composition of steel containing the above element species and containing P described later. Further, the remainder can be made Fe and impurities, including the above-mentioned elemental species and P described later. In addition to the above element species, the following element species can also be contained.
- ⁇ Ni 0-1.00%
- Ni is an element that increases the viscosity of the base and lowers the machinability. Therefore, the Ni content is preferably 1.00% or less. More preferably, it is less than 0.50%, More preferably, it is less than 0.30%.
- Ni is an element that suppresses the formation of ferrite in the tool structure.
- the essential toughness of the matrix is also improved, it may be added as necessary in the present invention. When added, 0.10% or more is preferable.
- Co 0-1.00% Since Co reduces the toughness of the hot tool, the content is preferably 1.00% or less. On the other hand, during use of a hot tool, Co forms a very dense and protective oxide film with good adhesion on the surface when the temperature is raised. This oxide film prevents metal contact with the counterpart material, suppresses temperature rise on the tool surface, and provides excellent wear resistance. Therefore, Co may be added as necessary. When added, addition of 0.30% or more is preferable.
- Nb causes a decrease in machinability, and is therefore preferably set to 0.30% or less.
- Nb has the effect of forming carbides and improving the reinforcement of the base and the wear resistance.
- Nb may be added as necessary. When added, 0.01% or more is preferable.
- Cu, Al, Ca, Mg, O (oxygen), and N (nitrogen) are elements that may remain in the steel as unavoidable impurities, for example.
- the content of these elements is preferably as low as possible.
- a small amount may be contained in order to obtain additional functions and effects such as control of the shape of inclusions, other mechanical properties, and improvement of production efficiency.
- Cu ⁇ 0.25%, Al ⁇ 0.025%, Ca ⁇ 0.0100%, Mg ⁇ 0.0100%, O ⁇ 0.0100%, and N ⁇ 0.0300% are sufficient. This is a preferable upper limit of regulation of the present invention.
- the hot tool of the present invention has the above-described component composition "including P exceeding 0.020% and 0.050% or less".
- P content was regulated to 0.020% or less, for example (patent document 3).
- the toughness of the hot tool can be maintained at the conventional level. If it exists, the energy etc. concerning reduction of P content can be reduced, and the burden on the environment can be reduced.
- the target is limited to a hot tool containing “P exceeding 0.020%”, and a method that can sufficiently maintain the toughness of the hot tool is studied. Is significant in that it can be reduced.
- the above object is limited to a hot tool containing “0.025% or more P”.
- the P content is 0.050% or less. Preferably it is less than 0.040%. More preferably, it is 0.035% or less.
- the hot tool of the present invention has a martensite structure after quenching and tempering, wherein “the grain size of the prior austenite grains is a crystal grain size number in accordance with JIS-G-0551, with a No. 9.5 or higher. And the P concentration at the grain boundary of the prior austenite grains is 1.5% by mass or less.
- the present inventor is a specific index for evaluating the toughness “toughness value (for example, (Charpy impact value) "and” grain boundary P concentration (that is, P concentration of prior austenite grain boundary) ", which is a specific index for evaluating P segregation, was investigated.
- FIG. 1 is a graph showing the relationship between the Charpy impact value and the grain boundary P concentration (that is, the P concentration of prior austenite grain boundaries) for a hot tool (quenched and tempered hardness: 43HRC) made of SKD61.
- Plotted in the graph are hot tools A1, B1, C1, D1 and A2, B2, C2, D2 evaluated in the examples described later.
- the measure below the graph shows that hot tools having a predetermined P content (0.009%, 0.020%, 0.025%) as a whole have various grain boundary P concentrations in the graph.
- the prior austenite grain size (average crystal grain size) is shown.
- the allowable upper limit value of the P content specified in SKD61 is 0.030%.
- the P content is actually reduced to less than 0.010% in consideration of a decrease in toughness, as described in Patent Document 3. It is. Further, as disclosed in Patent Document 3, the prior austenite grain size of the conventional hot tool is a grain size number in accordance with JIS-G-0551, No. About 8.0 (average crystal grain size is about 20 to 30 ⁇ m). And about such a conventional hot tool, when this inventor investigated, while the impact value by a 2 mmU notch Charpy impact test exceeds 70 (J / cm ⁇ 2 >), the grain boundary P density
- the grain boundary P concentration is lower than the conventional level, for example, “1.5% by mass or less”. If it can be suppressed, the toughness level of a conventional hot tool having a P content of less than 0.020% can be maintained. Preferably, the grain boundary P concentration is suppressed to “1.0 mass% or less”.
- this inventor investigated about the relationship between the grain boundary P density
- concentration of a hot tool concentration of a hot tool
- the volume of the prior austenite grain boundary which is a segregation site of P, is increased. did.
- the volume of the prior austenite grain boundary increases, the P concentration measured at the position of the prior austenite grain boundary is diluted even between hot tools having the same P content, and the grain boundary P concentration decreases.
- the effect of suppressing the P segregation of the present invention can be exhibited and the toughness can be improved.
- various hot tools having a component composition that can be adjusted to a martensite structure by quenching when the P content as a whole exceeds 0.020%, the effect of suppressing P segregation of the present invention is effective.
- the prior austenite grain size is a crystal grain size number in accordance with JIS-G-0551, with a small diameter of “No. 9.5 or more”. I found out. The larger the grain size number, the smaller the prior austenite grain size. And No. A crystal grain size number of 9.5 corresponds to an average crystal grain size of about 15 ⁇ m.
- the prior austenite grain size is about 15 ⁇ m or less in terms of average grain size (that is, grain size number, No. 9.5 or more), the grain boundary P concentration is suppressed to 1.5 mass% or less, and it can be seen that the Charpy impact value can be maintained at the conventional level of 70 (J / cm 2 ).
- the prior austenite grain size is the crystal grain size number, No. It is to make it a small diameter of 10.0 or more. This No. A prior austenite grain size of 10.0 or more is a preferable requirement, particularly when the P content of the hot tool is 0.025% or more.
- the crystal grain size number based on JIS-G-0551 can be handled equivalently to the crystal grain size number based on ASTM-E112, which is an international standard. These crystal grain size numbers are hereinafter simply expressed as “No.”.
- the upper limit of the grain size number of the prior austenite grain size is not particularly required. 12.0 (average crystal grain size is about 6 ⁇ m) is realistic. More realistically, no. 11.5 (average crystal grain size is about 7.5 ⁇ m).
- the position of the hot tool for measuring the prior austenite grain size can be a position where toughness is required. For example, it can be set as the work surface (surface in contact with the mating member) of various hot tools such as a mold or a jig, or other surface positions. Moreover, it can be set as the position of the surface (inner surface), such as the inside of various hot tools, and the hole and groove
- concentration of an above-mentioned prior austenite grain shall be measured with an Auger electron spectroscopy analyzer (AES).
- AES Auger electron spectroscopy analyzer
- one side of the measurement region is generally as wide as about 1 ⁇ m, and is around the former austenite grain boundary (ie, within the grain).
- the amount of P can also be measured.
- one side of the above measurement region is about 10 nm, which is optimal for measuring the P concentration targeting the prior austenite grain boundary.
- the hot tool is subjected to grain boundary fracture to expose the fracture surface.
- the position corresponding to the prior austenite grain boundary confirmed in the fracture surface is analyzed with an Auger electron spectroscopic analyzer, and each element is measured from the measurement region whose area is 3 ⁇ m ⁇ 3 ⁇ m.
- An Auger electron spectrum is collected (see FIG. 5).
- P concentration can be quantitatively analyzed and it can be set as said grain boundary P concentration.
- the upper limit of P that can be contained in the hot tool of the present invention is 0.050%.
- the hot tool of the present invention is “in addition, it contains 0.0250% or less of Zn” in its component composition.
- Zn is an element that can improve the toughness of the hot tool by being contained in the hot tool having the component composition described in (1) and (2) above. As a result, the deterioration of toughness due to an increase in the P content can be compensated.
- the effect of improving toughness can be sufficiently obtained by containing more than 0.0025%. More preferably, it is 0.0030% or more.
- the upper limit is preferably 0.0250%. More preferably, it is 0.0200% or less, More preferably, it is 0.0150% or less.
- the method for manufacturing a hot tool of the present invention is to “quenze and temper” the hot tool material having the component composition described in (1), (2) and (4) above.
- the hot tool material used for manufacturing the hot tool of the present invention is prepared into a martensite structure having a predetermined hardness by quenching and tempering, and is prepared into a hot tool product.
- said hot tool material is arranged in the shape of a hot tool by various machinings, such as cutting and a drilling.
- the timing of the machining is preferably performed in a state where the hardness of the material is low (that is, in an annealed state) before quenching and tempering. In this case, finishing machining may be performed after quenching and tempering.
- the pre-hardened material after quenching and tempering may be collectively machined into the shape of a hot tool, together with the finishing machining.
- the above-mentioned quenching and tempering temperatures vary depending on the component composition of the raw material and the target hardness, but the quenching temperature is preferably about 1000 to 1100 ° C., and the tempering temperature is preferably about 500 to 650 ° C.
- the quenching temperature is about 1000 to 1030 ° C.
- the tempering temperature is about 550 to 650 ° C.
- the quenching and tempering hardness is preferably 50 HRC or less. For this, 40-50 HRC is preferred. More preferably, it is 48 HRC or less.
- Substantial forging is hot working when an entity (that is, the above material) is trained to reduce its cross-sectional area and increase its length. And it is represented by the ratio A / a of the cross-sectional area A of the cross-section of the material whose cross-sectional area is reduced by this hot working and the cross-sectional area a of the cross-section whose cross-sectional area is reduced after the hot working.
- the “forging molding ratio” is preferably set to the above “7S or more”. Then, it is effective to end the hot working in a short actual working time without performing reheating during the hot working.
- the non-uniform distribution of P derived from the solidified structure of the material can be made uniform. Furthermore, the above-described hot working with a high working ratio can make the austenite grain size coarsened by the homogenization treatment fine. Then, immediately after the hot working is completed, the segregation sites of P in the structure can be increased, and the segregation of P again during the cooling after the hot working can be suppressed. By these conditions, it can suppress more effectively that P concentrates in the prior austenite grain boundary after quenching and tempering.
- Materials A, B, C and D (thickness 70 mm ⁇ width 70 mm ⁇ length 100 mm) made of hot working tool steel SKD61, which is a standard steel grade of JIS-G-4404 having the composition shown in Table 1, were prepared.
- the material A is a conventional material in which P is reduced to less than 0.010%.
- Cu, Al, Ca, Mg, O, and N are not added (including the case where Al is added as a deoxidizing agent in the dissolution step), Cu ⁇ 0.25%, Al ⁇ 0.025%, Ca ⁇ 0.0100%, Mg ⁇ 0.0100%, O ⁇ 0.0100%, and N ⁇ 0.0300%.
- Hot-steel tool material A1, B1, C1, D1 which performed annealing at 860 degreeC to the steel material which finished hot processing, and made the processing ratio at the time of said hot processing into 2S, and the processing ratio is 7S or more Hot tool materials A2, B2, C2, and D2 were prepared. Then, these hot tool materials A1 to D1 and A2 to D2 were quenched from 1030 ° C. and tempered at 630 ° C. (target hardness 43HRC) to obtain hot tools A1 to D1 having a martensitic structure, and A2 to D2 were prepared.
- a Charpy impact test piece (L direction, 2 mmU notch) was sampled from each of the hot tools A1 to D1 and A2 to D2, and a Charpy impact test was performed. Then, the prior austenite grain size in the structure of these Charpy impact test pieces was measured with a crystal grain size number in accordance with JIS-G-0551 (ASTM-E112). In addition, the P concentration (grain boundary P concentration) of the prior austenite grain boundaries of these hot tools was measured with a field emission Auger electron spectrometer (FE-AES). First, samples each having a diameter of 3.0 mm and a length of 20.0 mm were collected from each of the hot tools A1 to D1 and A2 to D2.
- FE-AES field emission Auger electron spectrometer
- a “notch” having a depth of 0.5 mm is processed in the circumferential portion of the sample.
- this sample was cooled to ⁇ 196 ° C. with liquid nitrogen in a high vacuum FE-AES apparatus, and then fractured to cause grain boundary fracture.
- a position where the old austenite grain boundary was broken was selected, and an Auger electron spectrum of a region having an area of 3 ⁇ m ⁇ 3 ⁇ m was collected.
- the P concentration was quantitatively analyzed from the collected Auger electron spectrum to obtain the grain boundary P concentration.
- Table 2 shows the analysis result of the grain boundary P concentration.
- the hot tool A1 is a conventional hot tool. And the P content was reduced to less than 0.010% in consideration of a decrease in toughness, and the Charpy impact value was 70 J / cm 2 or more. Moreover, the hot tool A2 is also a hot tool in which the P content is reduced to less than 0.010%. A large amount of energy is required to reduce the P content of the hot tool. In contrast to such a hot tool, the hot tools B1, C1, and D1 are hot tools in which the P content of the hot tool A1 is increased by more than 0.020%. And the grain boundary P density
- the hot tool B2 is a hot tool of the present invention, and the P content of the hot tool B1 is kept as it is, and the prior austenite grain size is No. in terms of the crystal grain size number.
- This is a hot tool with a reduced diameter of 9.5.
- concentration fell to the level of the conventional hot tool A1, and the Charpy impact value rose to 70 J / cm ⁇ 2 > or more.
- the hot tools C2 and D2 are also hot tools of the present invention, and the prior austenite grain size is No. in terms of the crystal grain size number while maintaining the P content of the hot tools C1 and D1, respectively. It is a hot tool with a diameter reduced to 9.5 or more.
- the Charpy impact value increased to about 80 J / cm 2 in combination with the effect of the decrease in the grain boundary P concentration by further containing an appropriate amount of Zn.
- FIG. 3 shows an image obtained by observing the fracture surface of the hot tool B1 with a scanning electron microscope (2000 ⁇ magnification) and an element mapping diagram showing the P concentration in the image.
- the portion where the fracture surface is smooth corresponds to the “grain boundary fracture portion (former austenite grain boundary)”.
- a portion indicated by a white dot is “a portion where P element is concentrated (a portion where P concentration is high)” (in practice, this element mapping is performed).
- the figure is displayed in color, and in this actual element mapping diagram, the portion where the P element is concentrated is indicated by a red region including the white dot portion) .
- the concentration of P element is remarkably increased and the grain boundary P concentration is high at the grain boundary fracture portion of FIG. 3 (hot tool B1).
- this hot tool B2 of this invention which reduced the prior austenite particle size of this FIG. 3, the grain boundary P density
Abstract
Description
そして、焼入れされた後のマルテンサイト組織中には、上記のオーステナイト温度域にまで加熱して保持する過程で生成されたオーステナイト結晶粒の粒界が、「旧オーステナイト粒界」として確認される。この旧オーステナイト粒界で形成される「旧オーステナイト粒径」の分布状況は、次に焼戻しされた後の金属組織(つまり、完成された熱間工具の組織)においても、実質的に、維持されている。
上記の成分組成は、0.020質量%を超え、かつ、0.050質量%以下のPを含み、
上記の焼入れ焼戻し後のマルテンサイト組織における旧オーステナイト粒の粒径が、JIS-G-0551に準拠した結晶粒度番号で、No.9.5以上であり、
この旧オーステナイト粒の粒界のP濃度が1.5質量%以下の熱間工具である。
好ましくは、上記の成分組成が、さらに、0.0250質量%以下のZnを含む熱間工具である。
上記の熱間工具材料の成分組成は、0.020質量%を超え、かつ、0.050質量%以下のPを含み、
上記の焼入れ焼戻しを行った後のマルテンサイト組織における旧オーステナイト粒の粒径が、JIS-G-0551に準拠した結晶粒度番号で、No.9.5以上であり、かつ、この旧オーステナイト粒の粒界のP濃度が1.5質量%以下の熱間工具の製造方法である。
好ましくは、上記の熱間工具材料の成分組成が、さらに、0.0250質量%以下のZnを含む熱間工具の製造方法である。
通常、熱間工具は、焼鈍状態の熱間工具材料に焼入れ焼戻しを行って作製される。この焼鈍組織を有した熱間工具材料は、鋼塊または鋼塊を分塊加工した鋼片でなる素材を出発材料として、これに様々な熱間加工や熱処理を行って所定の鋼材とし、この鋼材に焼鈍処理を行って、例えばブロック形状に仕上げられる。そして、従来、熱間工具材料に、焼入れ焼戻しによってマルテンサイト組織を発現する素材が用いられていることは、上述の通りである。マルテンサイト組織は、各種の熱間工具の絶対的な靱性を基礎付ける上で必要な組織である。このような熱間工具(すなわち、熱間工具材料)の素材として、例えば各種の熱間工具鋼が代表的である。熱間工具鋼は、その表面温度が概ね200℃以上に昇温される環境下で使用されるものである。そして、この熱間工具鋼の成分組成には、例えばJIS-G-4404の「合金工具鋼鋼材」にある規格鋼種や、その他提案されているものを代表的に適用できる。また、上記の熱間工具鋼に規定される以外の元素種も、必要に応じて添加や含有が可能である。
但し、熱間工具の絶対的な機械的特性を基礎付ける上で、例えば、上記したマルテンサイト組織を発現する一成分組成として、質量%で、C:0.30~0.50%、Cr:3.00~6.00%を含み、かつ、後述のPを含んだ熱間工具鋼の成分組成を有することが好ましい。そして、熱間工具の絶対的な靱性を向上させる上で、さらに、V:0.10~1.50%を含んだ熱間工具鋼の成分組成を有することが好ましい。あるいは、MoまたはWを含有する場合には、熱間工具の絶対的な靱性を向上させる上で、MoおよびWは単独または複合で(Mo+1/2W):3.50%以下を含んだ熱間工具鋼の成分組成を有することが好ましい。このとき、熱間工具に強度および軟化抵抗を付与する上で、上記の(Mo+1/2W)の値は、0.50%以上とすることが、より好ましい。
そして、具体的には、C:0.30~0.50%、Si:2.00%以下、Mn:1.50%以下、S:0.0500%以下、Cr:3.00~6.00%、MoおよびWは単独または複合で(Mo+1/2W):0.50~3.50%、V:0.10~1.50%を含み、かつ、後述のPを含んだ成分組成を有することが好ましい。熱間工具の基本的な靱性値を上げておくことで、これに本発明のP偏析の抑制効果が相乗的に作用して、より靱性に優れた熱間工具を得ることができる。本発明の熱間工具の成分組成を構成し得る各種元素について、以下の通り説明する。
Cは、一部が基地中に固溶して強度を付与し、一部は炭化物を形成することで耐摩耗性や耐焼付き性を高める、熱間工具の基本元素である。また、侵入型原子として固溶したCは、Cr等のCと親和性の大きい置換型原子と共に添加した場合に、I(侵入型原子)-S(置換型原子)効果(溶質原子の引きずり抵抗として作用し、熱間工具を高強度化する作用)も期待される。但し、過度の添加は靭性や熱間強度の低下を招く。よって、0.30~0.50%とすることが好ましい。より好ましくは0.34%以上である。また、より好ましくは0.40%以下である。
Siは、製鋼時の脱酸剤であるが、多過ぎると焼入れ焼戻し後の工具組織中にフェライトの生成を招く。よって、2.00%以下とすることが好ましい。より好ましくは1.00%以下である。さらに好ましくは0.50%以下である。一方、Siには、材料の被削性を高める効果がある。この効果を得るためには、0.20%以上の添加が好ましい。より好ましくは0.30%以上である。
Mnは、多過ぎると基地の粘さを上げて、材料の被削性を低下させる。よって、1.50%以下とすることが好ましい。より好ましくは1.00%以下である。さらに好ましくは0.75%以下である。一方、Mnには、焼入性を高め、工具組織中のフェライトの生成を抑制し、適度の焼入れ焼戻し硬さを得る効果がある。また、非金属介在物のMnSとして存在することで、被削性の向上に大きな効果がある。これらの効果を得るために、Mnは0.10%以上の添加が好ましい。より好ましくは0.25%以上である。さらに好ましくは0.45%以上である。
Sは、通常、添加しなくても、各種の熱間工具に不可避的に含まれ得る元素である。そして、熱間工具の素材時において熱間加工性を劣化させ、熱間加工中の素材に割れを生じさせる元素である。したがって、上記の熱間加工性を向上するためには、0.0500%以下に規制することが好ましい。一方、Sには、上記したMnと結合して、非金属介在物のMnSとして存在することで、被削性を向上する効果がある。この効果を得るためには、0.0300%以上の添加が好ましい。
Crは、焼入性を高め、また炭化物を形成して、基地の強化や耐摩耗性の向上に効果を有する元素である。そして、焼戻し軟化抵抗および高温強度の向上にも寄与する、熱間工具の基本元素である。但し、過度の添加は、かえって高温強度の低下を招く。また、焼入性の低下も招く。よって、3.00~6.00%とすることが好ましい。そして、より好ましくは5.50%以下である。また、より好ましくは3.50%以上である。さらに好ましくは4.00%以上である。特に好ましくは4.50%以上である。
MoおよびWは、焼戻しによって組織中に微細炭化物を析出または凝集させて、熱間工具に強度および軟化抵抗を付与する元素である。MoおよびWは、単独または複合で添加することができる。そして、この際の添加量は、WがMoの約2倍の原子量であることから、(Mo+1/2W)の式で定義されるMo当量で一緒に規定できる。当然、いずれか一方のみの添加としてもよいし、双方を共に添加することもできる。そして、上記の効果を得るためには、(Mo+1/2W)の値で0.50%以上の添加が好ましい。より好ましくは1.50%以上である。さらに好ましくは2.50%以上である。但し、多過ぎると被削性や靭性の低下を招くので、(Mo+1/2W)の値で3.50%以下が好ましい。より好ましくは2.90%以下である。
Vは、炭化物を形成して、基地の強化や耐摩耗性、焼戻し軟化抵抗を向上する効果を有する。そして、焼鈍組織中に分布した上記のV炭化物は、焼入れ加熱時のオーステナイト結晶粒の粗大化を抑制する“ピン止め粒子”として働き、靭性の向上に寄与する。これらの効果を得るためには0.10%以上の添加が好ましい。より好ましくは0.30%以上である。さらに好ましくは0.50%以上である。但し、多過ぎると被削性や、炭化物自身の増加による靭性の低下を招くので、1.50%以下とするのが好ましい。より好ましくは1.00%以下である。さらに好ましくは0.70%以下である。
・Ni:0~1.00%
Niは、基地の粘さを上げて被削性を低下させる元素である。よって、Niの含有量は1.00%以下とすることが好ましい。より好ましくは0.50%未満、さらに好ましくは0.30%未満である。一方、Niは、工具組織中のフェライトの生成を抑制する元素である。また、C、Cr、Mn、Mo、Wなどとともに工具材料に優れた焼入性を付与し、焼入時の冷却速度が緩やかな場合でもマルテンサイト主体の組織を形成して、靭性の低下を防ぐための効果的元素である。さらに、基地の本質的な靭性も改善するので、本発明では必要に応じて添加してもよい。添加する場合、0.10%以上の添加が好ましい。
Coは、熱間工具の靭性を低下させるので、1.00%以下とするのが好ましい。一方、Coは、熱間工具の使用中において、その昇温時の表面に極めて緻密で密着性の良い保護酸化皮膜を形成する。この酸化皮膜は、相手材との間の金属接触を防ぎ、工具表面の温度上昇を抑制するとともに、優れた耐摩耗性をもたらす。よって、Coは、必要に応じて添加してもよい。添加する場合、0.30%以上の添加が好ましい。
Nbは、被削性の低下を招くので、0.30%以下とするのが好ましい。一方、Nbは、炭化物を形成し、基地の強化や耐摩耗性を向上する効果を有する。また、焼戻し軟化抵抗を高めるとともに、Vと同様、結晶粒の粗大化を抑制し、靭性の向上に寄与する効果を有する。よって、Nbは、必要に応じて添加してもよい。添加する場合、0.01%以上の添加が好ましい。
熱間工具の靱性が劣化する要因の一つが、そのPの含有に起因した、マルテンサイト組織中の旧オーステナイト粒界へのP偏析にあることは、上述の通りである。よって、従来の熱間工具の場合、P含有量は、例えば、0.020%以下に規制されていた(特許文献3)。しかし、このような背景において、P含有量の許容値を上げても、具体的には、P含有量が0.020%を超えても、熱間工具の靱性を従来のレベルに維持できるのであれば、P含有量の低減に掛かるエネルギー等を削減することができ、環境への負荷を軽減することができる。また、熱間工具の靱性を、従来を超えるレベルに向上できれば、熱間工具自体の特性向上にも寄与できる。そこで、本発明では、対象を「0.020%を超えるP」を含有した熱間工具に限定して、この熱間工具の靱性を十分に維持できる手法を検討したところに、上記したエネルギー等を削減できる点で、大きな意味がある。好ましくは、上記の対象を「0.025%以上のP」を含有した熱間工具に限定する。
但し、Pの含有量が多過ぎると、後述する通り、本発明のP偏析の抑制効果が有効に発揮され難い。よって、P含有量は、0.050%以下とする。好ましくは0.040%未満である。より好ましくは0.035%以下である。
まず、本発明者は、熱間工具の靱性に及ぼす、旧オーステナイト粒界のP偏析の影響度を把握するために、その靱性を評価するための具体的な指標である「靱性値(例えば、シャルピー衝撃値)」と、P偏析を評価するための具体的な指標である「粒界P濃度(つまり、旧オーステナイト粒界のP濃度)」との関係を調査した。その結果、これら熱間工具の靱性値と粒界P濃度との間には相関があり、全体としてのP含有量が同じ熱間工具であっても、粒界P濃度が異なれば、熱間工具の靱性値に差が生じることを知見した。そして、熱間工具の全体としてのP含有量を低減するのではなくて、上記の粒界P濃度を狙って、これを低減することこそが、熱間工具の靱性値の向上に直接的に作用することを突きとめた。
SKD61に規格されているP含有量の許容上限値は0.030%である。しかし、従来の熱間工具において、そのP含有量は、実際には、特許文献3にあるように、靱性の低下に配慮して、0.010%未満にまで低減されているのが一般的である。また、特許文献3にあるように、従来の熱間工具の旧オーステナイト粒径は、JIS-G-0551に準拠した結晶粒度番号でNo.8.0程度(平均結晶粒径で20~30μm程度)である。そして、このような従来の熱間工具について、本発明者が調査したところ、2mmUノッチシャルピー衝撃試験による衝撃値が70(J/cm2)を超えるのに対して、その粒界P濃度は概ね1.0質量%未満のレベルであった(図1の熱間工具A1)。
そして、焼入れによってマルテンサイト組織に調整できる成分組成を有した各種の熱間工具において、全体としてのP含有量が0.020%を超えたときに、本発明のP偏析の抑制効果が有効に発揮される条件を検討した結果、上記の旧オーステナイト粒径を、JIS-G-0551に準拠した結晶粒度番号で、「No.9.5以上」の小径にすることが有効であることを、突きとめた。なお、上記の結晶粒度番号が大きくなる程、旧オーステナイト粒径は小さくなる。そして、No.9.5の結晶粒度番号は、平均結晶粒径で15μm程度に相当する。
なお、この旧オーステナイト粒径の結晶粒度番号について、上限は特に要しないが、No.12.0(平均結晶粒径で6μm程度)が現実的である。より現実的には、No.11.5(平均結晶粒径で7.5μm程度)である。
上記の旧オーステナイト粒径を測定する熱間工具の位置は、靱性の求められる位置とすることができる。例えば、金型や治具といった各種の熱間工具の作業面(相手材と接する表面)や、その他の表面の位置とすることができる。また、各種の熱間工具の内部や、その内部に形成された孔や溝等の表面(内面)の位置とすることができる。
まず、粒界P濃度を測定する熱間工具の位置で、熱間工具を粒界破壊して、破断面を露出させる。次に、この破断面中に確認される旧オーステナイト粒界に相当する位置(図4を参照)をオージェ電子分光分析装置で分析して、その面積が3μm×3μmとなる測定領域から各元素のオージェ電子スペクトルを収集する(図5を参照)。そして、得られた各元素のピーク強度比から、P濃度を定量分析して、上記の粒界P濃度とすることができる。
なお、一般的には、焼入れ焼戻し後の熱間工具において、上記の旧オーステナイト粒径をNo.13.0以上にまで小径化するのは容易でない。そして、上記の旧オーステナイト粒径の小径化が容易でない中で、全体としてのP含有量だけが増加すると、旧オーステナイト粒界でのP濃度の希釈に限界があり、本発明のP偏析の抑制効果が十分に発揮され難くなる。そして、例えば、上記した70(J/cm2)のシャルピー衝撃値のレベルを維持し難くなる。よって、本発明の熱間工具が含有できるPの上限は、0.050%としている。
Znは、上記の(1)および(2)で説明した成分組成の熱間工具に含有させることで、熱間工具の靭性を向上させることができる元素である。これによって、P含有量の増加による靭性の劣化分を補うことができる。好ましくは0.0025%を超えて含有することで、この靱性向上の効果を十分に得ることができる。より好ましくは0.0030%以上である。
但し、Znを過度に含有すると、旧オーステナイト粒界などに極端なZn偏析が生じて、かえって靱性を劣化させる要因となり得る。よって、Znを含有する場合でも、上限は0.0250%とすることが好ましい。より好ましくは0.0200%以下、さらに好ましくは0.0150%以下である。
本発明の熱間工具の製造に使用される熱間工具材料は、焼入れおよび焼戻しによって所定の硬さを有したマルテンサイト組織に調製されて、熱間工具の製品に整えられる。そして、上記の熱間工具材料は、切削や穿孔といった各種の機械加工等によって、熱間工具の形状に整えられる。上記の機械加工のタイミングは、焼入れ焼戻し前の、材料の硬さが低い状態(つまり、焼鈍状態)で行うことが好ましい。この場合、焼入れ焼戻し後に仕上げの機械加工を行ってもよい。また、場合によっては、焼入れ焼戻しを行った後のプリハードン材料の状態で、上記の仕上げの機械加工も合わせて、一括して熱間工具の形状に機械加工してもよい。
そして、上記の均質化処理を行った後の、上記の熱間加工は、その加工比(断面積比)を7S以上の実体鍛錬とすることが有効である(「S」は、実体鍛錬を示す記号である)。実体鍛錬とは、実体(つまり、上記の素材)を鍛錬して、その断面積を減少し長さを増した場合の熱間加工のことである。そして、この熱間加工によって断面積が減少することとなる素材の横断面の断面積Aと、その熱間加工後に断面積が減少した横断面の断面積aとの比A/aで表される「鍛錬成形比」を、上記の「7S以上」とすることが好ましい。そして、この熱間加工中の再加熱は行わずに、短い実加工時間で熱間加工を終了することが有効である。
高温長時間の上記の均質化処理によって、素材の凝固組織に由来する不均一なPの分布を均一にすることができる。さらに、加工比の高い上記の熱間加工によって、均質化処理で粗大になったオーステナイト粒径を微細にすることができる。そして、熱間加工が終了した直後で、組織中のPの偏析サイトを増加させることができ、熱間加工後の冷却中にPが再度偏析することを抑えられる。これらの条件によって、焼入れ焼戻し後の旧オーステナイト粒界にPが濃縮することを、更に効果的に抑制できる。
そして、熱間加工を終えた鋼材に860℃の焼鈍を行って、上記の熱間加工時の加工比を2Sとした熱間工具材料A1、B1、C1、D1と、同加工比を7S以上とした熱間工具材料A2、B2、C2、D2とを作製した。そして、これら熱間工具材料A1~D1およびA2~D2に、1030℃からの焼入れと、630℃の焼戻しを行って(狙い硬さ43HRC)、マルテンサイト組織を有した熱間工具A1~D1およびA2~D2を作製した。
また、これら熱間工具の旧オーステナイト粒界のP濃度(粒界P濃度)を、電界放射型オージェ電子分光分析装置(FE-AES)で測定した。まず、上記の熱間工具A1~D1およびA2~D2のそれぞれから、直径3.0mm×長さ20.0mmの試料を採取した。この試料の円周部には、深さ0.5mmの「切欠き」が加工されている。次に、この試料を、高真空にしたFE-AESの装置内において、液体窒素で-196℃に冷却した後、破断して、粒界破壊させた。そして、この粒界破壊させた破断面から、旧オーステナイト粒界で破壊している位置を選択して、3μm×3μmの面積となる領域のオージェ電子スペクトルを収集した。そして、この収集したオージェ電子スペクトルからP濃度を定量分析して、粒界P濃度とした。粒界P濃度の分析結果を表2に示す。
各図の上側にある走査型電子顕微鏡画像において、破断面が滑らかな部分が「粒界破壊部(旧オーステナイト粒界)」に相当する。そして、各図の下側にある元素マッピング図において、白色の点で示される部分が「P元素が濃化した部分(P濃度が高い部分)」である(なお、実際には、この元素マッピング図は、カラーで表示されている。そして、この実際の元素マッピング図において、上記のP元素が濃化した部分は、上記の白色の点の部分を含んだ赤色の領域で示されている)。図2と図3との比較において、図3(熱間工具B1)の粒界破壊部で、P元素の濃化が著しく、粒界P濃度が高いことがわかる。そして、この図3の旧オーステナイト粒径を小径化した本発明の熱間工具B2は、その破断面における粒界P濃度が図2(熱間工具A1)のレベルにまで低下した。
Claims (4)
- 焼入れによってマルテンサイト組織に調整できる成分組成を有し、焼入れ焼戻し後のマルテンサイト組織を有する熱間工具において、
前記成分組成は、0.020質量%を超え、かつ、0.050質量%以下のPを含み、
前記焼入れ焼戻し後のマルテンサイト組織における旧オーステナイト粒の粒径が、JIS-G-0551に準拠した結晶粒度番号で、No.9.5以上であり、
前記旧オーステナイト粒の粒界のP濃度が1.5質量%以下であることを特徴とする熱間工具。 - 前記成分組成は、さらに、0.0250質量%以下のZnを含むことを特徴とする請求項1に記載の熱間工具。
- 焼入れによってマルテンサイト組織に調整できる成分組成を有した熱間工具材料に焼入れ焼戻しを行う、マルテンサイト組織を有する熱間工具の製造方法において、
前記熱間工具材料の成分組成は、0.020質量%を超え、かつ、0.050質量%以下のPを含み、
前記焼入れ焼戻しを行った後のマルテンサイト組織における旧オーステナイト粒の粒径が、JIS-G-0551に準拠した結晶粒度番号で、No.9.5以上であり、かつ、前記旧オーステナイト粒の粒界のP濃度が1.5質量%以下であることを特徴とする熱間工具の製造方法。 - 前記熱間工具材料の成分組成は、さらに、0.0250質量%以下のZnを含むことを特徴とする請求項3に記載の熱間工具の製造方法。
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP16755151.4A EP3263730B1 (en) | 2015-02-25 | 2016-02-02 | Hot-working tool and manufacturing method therefor |
CN201680007496.2A CN107208219A (zh) | 2015-02-25 | 2016-02-02 | 热作工具及其制造方法 |
US15/533,550 US10494688B2 (en) | 2015-02-25 | 2016-02-02 | Hot-working tool and manufacturing method therefor |
JP2017502018A JP6156670B2 (ja) | 2015-02-25 | 2016-02-02 | 熱間工具およびその製造方法 |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2015035314 | 2015-02-25 | ||
JP2015-035314 | 2015-02-25 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2016136401A1 true WO2016136401A1 (ja) | 2016-09-01 |
Family
ID=56788223
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2016/053019 WO2016136401A1 (ja) | 2015-02-25 | 2016-02-02 | 熱間工具およびその製造方法 |
Country Status (6)
Country | Link |
---|---|
US (1) | US10494688B2 (ja) |
EP (1) | EP3263730B1 (ja) |
JP (1) | JP6156670B2 (ja) |
CN (1) | CN107208219A (ja) |
TW (1) | TWI577807B (ja) |
WO (1) | WO2016136401A1 (ja) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP3150735B1 (en) * | 2014-05-28 | 2020-01-15 | Hitachi Metals, Ltd. | Hot work tool material and method for manufacturing hot work tool |
JP6826767B2 (ja) * | 2018-10-05 | 2021-02-10 | 日立金属株式会社 | 熱間工具鋼および熱間工具 |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003328078A (ja) * | 2002-05-10 | 2003-11-19 | Komatsu Ltd | 高硬度高靭性鋼およびその鋼材を使用した装軌部品、耐土砂摩耗部品、締結ボルト、高靭性歯車、高靭性高耐面圧歯車、耐摩耗鋼板 |
JP2005082813A (ja) * | 2003-09-04 | 2005-03-31 | Daido Steel Co Ltd | プラスチック成形金型用プレハードン鋼 |
JP2007224418A (ja) * | 2006-01-30 | 2007-09-06 | Hitachi Metals Ltd | 靭性に優れた熱間工具鋼 |
JP2010031366A (ja) * | 2008-06-26 | 2010-02-12 | Hitachi Metals Ltd | 高温強度および表面仕上げ特性に優れた金型およびその製造方法 |
JP2013032576A (ja) * | 2011-07-04 | 2013-02-14 | Hitachi Metals Ltd | 靭性に優れた熱間工具鋼の製造方法 |
JP2013082992A (ja) * | 2011-09-28 | 2013-05-09 | Hitachi Metals Ltd | 靭性に優れた金型用鋼材の製造方法 |
Family Cites Families (19)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2985529A (en) * | 1958-08-27 | 1961-05-23 | Birmingham Small Arms Co Ltd | Creep resistant non-austenitic steels |
US3132937A (en) * | 1962-06-11 | 1964-05-12 | Int Nickel Co | Cast steel |
JP2700264B2 (ja) | 1988-12-30 | 1998-01-19 | 愛知製鋼株式会社 | 熱間工具鋼 |
DE69422028T2 (de) * | 1993-12-28 | 2000-03-30 | Nippon Steel Corp | Martensitischer wärmebeständiger stahl mit hervorragender erweichungsbeständigkeit und verfahren zu dessen herstellung |
US20020011285A1 (en) * | 1997-09-22 | 2002-01-31 | Nobuyuki Fujitsuna | Ferritic heat-resistant steel and method for producing it |
JP3468126B2 (ja) * | 1998-10-14 | 2003-11-17 | 大同特殊鋼株式会社 | 冷間加工性にすぐれたマルテンサイト系耐熱鋼 |
JP2000328196A (ja) | 1999-05-25 | 2000-11-28 | Daido Steel Co Ltd | 熱間工具鋼 |
DE10025808A1 (de) * | 2000-05-24 | 2001-11-29 | Alstom Power Nv | Martensitisch-härtbarer Vergütungsstahl mit verbesserter Warmfestigkeit und Duktilität |
JP3838928B2 (ja) | 2002-03-11 | 2006-10-25 | 日本高周波鋼業株式会社 | 熱間工具鋼 |
JP4400423B2 (ja) * | 2004-01-30 | 2010-01-20 | Jfeスチール株式会社 | マルテンサイト系ステンレス鋼管 |
US8083990B2 (en) * | 2005-11-09 | 2011-12-27 | Japan Science And Technology Agency | Iron-based alloy having shape memory properties and superelasticity and its production method |
JP5385554B2 (ja) * | 2008-06-19 | 2014-01-08 | 株式会社神戸製鋼所 | 熱処理用鋼 |
EP2439304B1 (en) * | 2009-06-01 | 2014-10-22 | JFE Steel Corporation | Steel sheet for brake disc, and brake disc |
JP5515442B2 (ja) * | 2009-06-16 | 2014-06-11 | 大同特殊鋼株式会社 | 熱間工具鋼及びこれを用いた鋼製品 |
DE102010025287A1 (de) * | 2010-06-28 | 2012-01-26 | Stahlwerk Ergste Westig Gmbh | Chrom-Nickel-Stahl |
MX342629B (es) * | 2010-07-28 | 2016-10-07 | Nippon Steel & Sumitomo Metal Corp | Lamina de acero enrollada en caliente, lamina de acero enrollada en frio, lamina de acero galvanizada y metodos para fabricar los mismos. |
JP5528986B2 (ja) * | 2010-11-09 | 2014-06-25 | 株式会社日立製作所 | 析出硬化型マルテンサイト系ステンレス鋼およびそれを用いた蒸気タービン部材 |
CN103403209B (zh) * | 2011-03-03 | 2016-01-13 | 日立金属株式会社 | 韧性优异的热作工具钢及其制造方法 |
EP3150735B1 (en) * | 2014-05-28 | 2020-01-15 | Hitachi Metals, Ltd. | Hot work tool material and method for manufacturing hot work tool |
-
2016
- 2016-02-02 JP JP2017502018A patent/JP6156670B2/ja active Active
- 2016-02-02 EP EP16755151.4A patent/EP3263730B1/en active Active
- 2016-02-02 US US15/533,550 patent/US10494688B2/en active Active
- 2016-02-02 WO PCT/JP2016/053019 patent/WO2016136401A1/ja active Application Filing
- 2016-02-02 CN CN201680007496.2A patent/CN107208219A/zh active Pending
- 2016-02-18 TW TW105104680A patent/TWI577807B/zh active
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003328078A (ja) * | 2002-05-10 | 2003-11-19 | Komatsu Ltd | 高硬度高靭性鋼およびその鋼材を使用した装軌部品、耐土砂摩耗部品、締結ボルト、高靭性歯車、高靭性高耐面圧歯車、耐摩耗鋼板 |
JP2005082813A (ja) * | 2003-09-04 | 2005-03-31 | Daido Steel Co Ltd | プラスチック成形金型用プレハードン鋼 |
JP2007224418A (ja) * | 2006-01-30 | 2007-09-06 | Hitachi Metals Ltd | 靭性に優れた熱間工具鋼 |
JP2010031366A (ja) * | 2008-06-26 | 2010-02-12 | Hitachi Metals Ltd | 高温強度および表面仕上げ特性に優れた金型およびその製造方法 |
JP2013032576A (ja) * | 2011-07-04 | 2013-02-14 | Hitachi Metals Ltd | 靭性に優れた熱間工具鋼の製造方法 |
JP2013082992A (ja) * | 2011-09-28 | 2013-05-09 | Hitachi Metals Ltd | 靭性に優れた金型用鋼材の製造方法 |
Also Published As
Publication number | Publication date |
---|---|
JP6156670B2 (ja) | 2017-07-05 |
EP3263730A1 (en) | 2018-01-03 |
EP3263730B1 (en) | 2019-09-11 |
US10494688B2 (en) | 2019-12-03 |
TWI577807B (zh) | 2017-04-11 |
JPWO2016136401A1 (ja) | 2017-06-29 |
TW201632638A (zh) | 2016-09-16 |
US20170342517A1 (en) | 2017-11-30 |
EP3263730A4 (en) | 2018-07-18 |
CN107208219A (zh) | 2017-09-26 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2757393C (en) | Case-hardened steel superior in cold workability, machinability, and fatigue characteristics after carburized quenching and method of production of same | |
KR101520208B1 (ko) | 기소강 및 그의 제조 방법, 및 기소강을 이용한 기계 구조 부품 | |
US8673094B2 (en) | Case hardening steel and manufacturing method thereof | |
EP2065483A1 (en) | Hot-working tool steel having excellent stiffness and high-temperature strength and method for production thereof | |
JP4964063B2 (ja) | 冷間鍛造性および結晶粒粗大化防止特性に優れた肌焼鋼およびそれから得られる機械部品 | |
WO2015182586A1 (ja) | 熱間工具材料および熱間工具の製造方法 | |
CN109477179B (zh) | 高频淬火用钢 | |
KR20190028781A (ko) | 고주파 담금질용 강 | |
KR20190028782A (ko) | 고주파 담금질용 강 | |
CN111411293A (zh) | 高速工具及其制造方法 | |
EP3315626B1 (en) | Bolt | |
WO2010074017A1 (ja) | 鋼の焼入方法 | |
WO2017115842A1 (ja) | 肌焼鋼、浸炭部品および肌焼鋼の製造方法 | |
US11447849B2 (en) | Non-heat treated steel for induction hardening | |
WO2007123164A1 (ja) | 内燃機関用ピストンリング材 | |
WO2012118053A1 (ja) | 靭性に優れた熱間工具鋼およびその製造方法 | |
WO2018061101A1 (ja) | 鋼 | |
JP6156670B2 (ja) | 熱間工具およびその製造方法 | |
JP2000034538A (ja) | 旋削加工性に優れた機械構造用鋼 | |
EP3173500B2 (en) | Hot-working tool material, method for manufacturing hot-working tool, and hot-working tool | |
JP4528363B1 (ja) | 冷間加工性、切削性、浸炭焼入れ後の疲労特性に優れた肌焼鋼及びその製造方法 | |
CN107429359B (zh) | 热轧棒线材、部件及热轧棒线材的制造方法 | |
EP3385398A1 (en) | High-strength bolt | |
JP5976581B2 (ja) | 転動疲労特性に優れた軸受用鋼材、および軸受部品 | |
WO2023008413A1 (ja) | 高温強度及び靭性に優れた熱間工具鋼 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 16755151 Country of ref document: EP Kind code of ref document: A1 |
|
ENP | Entry into the national phase |
Ref document number: 2017502018 Country of ref document: JP Kind code of ref document: A |
|
WWE | Wipo information: entry into national phase |
Ref document number: 15533550 Country of ref document: US |
|
REEP | Request for entry into the european phase |
Ref document number: 2016755151 Country of ref document: EP |
|
NENP | Non-entry into the national phase |
Ref country code: DE |