EP0767251B1 - Acier à durcissement par vieillissement pour moules de coulée sous pression - Google Patents

Acier à durcissement par vieillissement pour moules de coulée sous pression Download PDF

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Publication number
EP0767251B1
EP0767251B1 EP19960112457 EP96112457A EP0767251B1 EP 0767251 B1 EP0767251 B1 EP 0767251B1 EP 19960112457 EP19960112457 EP 19960112457 EP 96112457 A EP96112457 A EP 96112457A EP 0767251 B1 EP0767251 B1 EP 0767251B1
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EP
European Patent Office
Prior art keywords
die
age
steel
ratio
dimensional change
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Revoked
Application number
EP19960112457
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German (de)
English (en)
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EP0767251A1 (fr
Inventor
Masamitu Noguchi
Takashi Ohfuji
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyota Motor Corp
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Toyota Motor Corp
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Publication of EP0767251A1 publication Critical patent/EP0767251A1/fr
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten

Definitions

  • This invention relates to an age-hardening steel for die-casting dies and particularly to an age-hardening steel for die -casting dies which is superior in heat check resistance and has a small ratio of dimensional change by ageing.
  • the tool steel for hot working which mainly contains 5 % Cr and 1 ⁇ 1.5 % Mo.
  • the quenching and tempering treatments are carried out to cause the tool steel to display the required hardness and strength.
  • the age -hardening steel such as typically 18 % Ni marageing steel has been examined to apply to the die-casting dies.
  • this marageing steel includes a problem that the life of the casting die constituted by this steel is remarkably short comparing to that made of the conventional tool steel for hot working.
  • the form and dimension of the dies before the ageing treatment are determined making allowances for the shrinkage due to the heat treatment.
  • the shrinking deformation due to the heat treatment is in excess of a certain level, it becomes difficult to finally assure the dimensional accuracy of the die-casting dies.
  • EP-A- 105 864 there is disclosed a composition for railway applications, wherein Ni: 7 ⁇ 20%, Cr: 0 ⁇ 13%, Mo: 1 ⁇ 5 ⁇ 6%, Co: 0 ⁇ 15%, Ti: 0.1 ⁇ 1%, Al: 0 ⁇ 0.2%, Si: 0.01 ⁇ 0.2%, Mn: 0.01 ⁇ 0.2%, C: 0.01 ⁇ 0.05%, Fe: the remainder.
  • Japan unscreened publication Toku-kai -hei 6-248389 there is disclosed a marageing steel for die -casting die having the following composition to increase the softening resistance so as to improve the heat check resistance, wherein Ni : 12 ⁇ 14 %, Mo : 4.5 ⁇ 6.0 %, Co : 7.5 ⁇ 9.5 %, Ti : 0.5 ⁇ 1.0 %, C : ⁇ 0.03 %, Si : ⁇ 0.1 %, Mn : ⁇ 0.1%, P : ⁇ 0.01 %, S : ⁇ 0.01 %, Cr : ⁇ 0.05 %, N : ⁇ 0.01 %, Al : 0.02 ⁇ 0.20 %, Fe : the remainder.
  • Japan unscreened patent publication Toku-kai-sho 63-145753 there is disclosed a marageing steel having the following composition to improve the delayed fracture resistance, wherein C : ⁇ 0.03 %, Si : ⁇ 0.10 %, Mn : ⁇ 0.10 %, Cu : ⁇ 0.10 %, Ni : 7 ⁇ 20 %, Cr : ⁇ 0.10 %, Mo : 2 ⁇ 6 %, Co : 5 ⁇ 18 %, Al : ⁇ 0.50 %, Ti : 0.8 ⁇ 2.5 %, B : 0.0005 ⁇ 0.005 %, P : ⁇ 0.0025 %, S : ⁇ 0.0025 % , %, Fe : P + S : ⁇ 0.0030 the remainder.
  • Japan unscreened patent publication -kai-sho 62-228455 there is disclosed a marageing steel having the following composition to improve the fatigue property, wherein C : ⁇ 0.03 %, Si : ⁇ 0.10 %, Mn : ⁇ 0.10 %, Cu : ⁇ 0.1 %, Ni : 7 ⁇ 20 %, Cr : ⁇ 0.1 %, Mo : 1 ⁇ 10 %, Co : ⁇ 18 %, Al : ⁇ 1 %, Ti : ⁇ 2.5 %, P : ⁇ 0.002 %, S : ⁇ 0.0015 %, P + S : ⁇ 0.0030%, Fe : the remainder.
  • the object of the present invention is to provide an age-hardening steel for die-casting dies which is superior in heat check resistance, displays long life of the die, and has an improved ratio of dimensional change in the age heat treatment in the case of the application to the die-casting dies.
  • the present invention to accomplish this object is characterized in that the composition of the age-hardening steel for die-casting die, in weight %, contains C : ⁇ 0.03 %, Si : ⁇ 0.10 %, Mn : ⁇ 0.10 %, Ni : 9.0 ⁇ 11.0 %, Cr : 0.10 ⁇ 5.0 %, Mo : 5.0 ⁇ 8.0 %, Co : 5.0 ⁇ 8.0 %, Ti : 0.10 ⁇ 1.0 %, Al : 0.05 ⁇ 0.15 %, and 30 ⁇ Co (%) x Mo (%) ⁇ 50, and the remainder Fe and incidental impurities.
  • the composition may contain Cr : 0.30 ⁇ 1.0 %.
  • N may be regulated to 0.0050 % or less.
  • the TiN inclusion in the steel material it is preferable that the TiN inclusion larger than 10 ⁇ m in the equivalent circular diameter may be 2 % of the whole or less.
  • the age-hardening steel according to the present invention has a small ratio of dimensional change in the heat treatment, so that it is possible to reduce the machining man power in the manufacturing of the die-casting dies and to improve the dimensional accuracy of the die-casting dies as well.
  • Figure 1 is a diagram illustrating the heat check resistance and the Charpy impact value respectively relating to the solubility product of Co(%) and Mo(%) based on the example of the present invention.
  • the present inventor When researching the technical measures to improve the heat check resistance and the ratio of dimensional change in the heat treatment for the age-hardening steel for die -casting dies, the present inventor has obtain a knowledge that the reduction of the Ni quantity and the addition of the proper Cr quantity are effective to the reduction of the ratio of dimensional change in the ageing treatment.
  • the reduction of the Ni quantity results in the rising of the austenitic transformation point (As point) and contributes to the improvement of the heat check resistance.
  • the temperature of the As point is low, according to the heating operation of the molten metal during the use of the die-casting dies, the surface stratum of the die is liable to austenitize from the martensitic structure, and it promotes the generation of the cracks.
  • the As point is caused to be high, this problem can be prevented, so that it is possible to improve the heat check resistance.
  • the ratio of dimensional change in the heat treatment is caused to be small according to the addition of the appropriate Cr quantity.
  • the addition of Cr causes to lower the As point, so that it is feared that the heat check resistance may be made inferior.
  • the adding quantity of Cr is controlled under the certain level.
  • the preferred content of Cr is in 0.30 ⁇ 1.0 % and the quantity of N is preferable to be as little as possible.
  • the increase of N results in the deposition of the TiN, and thereby the low cycle fatigue property of the die-casting dies is made inferior, wherein the low cycle fatigue is the phenomenon that the casting die is broken under the big die-tightening force, for example.
  • the N quantity is as little as possible.
  • the extreme minimization of N results in the rising of the manufacturing cost, so that it is preferable that the upper limit of the N quantity is set in 0.0050 % even when the quantity of N is made as little as possible.
  • the TiN particles larger than 10 ⁇ m in the equivalent circular diameter may be 2% of the whole or less.
  • Si causes the toughness inferior, it is necessary that Si is made 0.10 % or less.
  • Mn ⁇ 0.10 %
  • Mn is controlled to 0.10 % or less because it produces the MnS inclusion combining with S so as to make the toughness inferior.
  • Ni 9.0 ⁇ 11.0 %
  • Ni is an essential element to form a matrix superior in the toughness in a solid solution of Fe.
  • the quantity of depositing material increases along with the increase of the adding quantity, so that it causes to extend the ratio of age shrinkage (ratio of dimensional change).
  • the austenitic transformation point As lowers to make the heat check resistance inferior. Since the surface of the casting die is exposed to the molten aluminum in high temperature of 600 ⁇ 650 °C , for example, it is required that the As point is over the arriving surface temperature. For that purpose, it is necessary that Ni may be 11.0 % or less. However, if the adding quantity of Ni is less than 9.0 %, the necessary toughness can not be assured. For that reason, the content of Ni is set in 9.0 ⁇ 11.0 % in the present invention. Cr : 0.10 ⁇ 5.0 %
  • the increase of the Co quantity has an effect to promote the age hardening property because it results in the lowering of the solubility degree of Mo in the solid solution.
  • Ti is a hardening element which forms Ni 3 Ti and contributes the age-hardening
  • the excessive addition of Ti causes to deposit TiN and to make the toughness and the low cycle fatigue property inferior.
  • the Ms point is caused to lower, so that the Ti segregation band becomes the retained austenitic band, and also the austenitic transformation point is caused to lower, so that the heat check resistance is made inferior. Consequently, the upper limit of Ti is set in 1.0 %.
  • Al is a component to be added as a deoxidizer and contributes even to the age-hardening together with Ti. However, when it is under 0.05 %, the age-hardening property is insufficient, and on the contrary, when it is over 0.15 %, the toughness is made inferior. Consequently, Al is set in 0.05 ⁇ 0.15 % in the present invention. N : ⁇ 0.0050 %
  • the quantity of N may be reduced as far as possible.
  • the extreme minimization of N results in rising of the manufacturing cost, so that the upper limit is set in 0.0050 %.
  • the particles become the starting points of fracture in the portion under the die-tightening force, the teeming stress or the thermal stress. As a result, it causes the lowering of the low cycle fatigue property and even the big fracture of the casting die. Consequently, it is required that the particles of TiN inclusion larger than 10 ⁇ m may be 2 % of the whole or less. 30 ⁇ Co (%) x Mo (%) ⁇ 50
  • the solubility product of Co (%) x Mo (%) indicates the age-hardening property, and when this solubility product is reduced, also the aged hardness is lowered. As a result, it restrains the toughness from lowering due to the reduction of the Ni quantity and results in the assurance of the toughness. Consequently, the upper limit of this value is set in 50.
  • the age-hardening steel of the chemical composition shown in Table 1 was treated in atmospheric induction melting and in ingot-making (350 mm phi), cooled by water after holding in 930 ⁇ 1130 °C, and moreover cooled by air after holding in 880 ⁇ 980 °C. From such a steel material were extracted a JIS No.3 Charpy impact test piece in the T direction (vertical to the rolling direction) of 1/2R (radius) portion, a heat check test piece of 15 mm phi (diameter) x 5 mm t (thickness), and a low cycle fatigue test piece. Then, the Charpy impact test, heat check test, and low cycle fatigue test were performed with those test pieces.
  • the ageing 520 °C x 5 hr, Air cooling (in the peak ageing condition)
  • the heat check resistance test High-frequency heating 650 °C x 4 sec and Water cooling 3 sec, repeated in 1000 times of this heating and cooling cycle.
  • the Charpy impact test 2 mm U-notched test piece, extracted in the T direction, tested in the room temperature.
  • the measurements of the ratio of dimensional change by ageing were performed respectively in the longitudinal (L) and transverse (T) directions of the block test piece of 210 mm L x 130 mm W x 45 mm t.
  • the low cycle fatigue test was carried out by examining the number of the repeated times to result in the fracture when the one-side tension was repeatedly applied to the test piece along the single axis under the maximum stress of 123 kgf/ mm 2 .
  • the comparative example 18, in which the content of Ni is out of the range limited in the present invention, is low in As point and inferior in the heat check resistance; the comparative example 19, which contains Ni : 18 %, is extremely low in As point and also remarkably inferior in heat check resistance although it shows a good figure of the Charpy impact value.
  • the figures 1 (A) and 1 (B) show the heat check resistance and the Charpy impact value respectively relating to the solubility product of Co and Mo based on the results of Table 2. Referring to those figures, it will be seen that the good results are obtained either in the heat check resistance or in the Charpy impact value by controlling the solubility product of Co and Mo in the range of 30 ⁇ 50.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)

Claims (4)

  1. Un acier durcissant au vieillissement pour moule de coulée sous pression présentant une résistance supérieure aux craquelures par choc thermique et un meilleur rapport de variation dimensionnelle au vieillissement, comprenant : en poids %, C : ≤ 0,03%, Si : ≤ 0,10%, Mn : ≤ 0,10%, Ni : 9,0 à 11,0%, Cr : 0,10 à 5,0%, Mo : 5,0 à 8,0%, Co : 5,0 à 8,0%, Ti : 0,10 à 1,0%, Al : 0,05 à 0,15% et 30 < Co (%) x Mo (%) < 50, et le reste étant Fe et d'éventuelles impuretés.
  2. Un acier durcissant au vieillissement pour moule de coulée sous pression présentant une résistance supérieure aux craquelures par choc thermique et un meilleur rapport de variation dimensionnelle au vieillissement selon la revendication 1 caractérisé en ce que la composition est contrôlée dans des valeurs de Cr comprises entre 0,30 et 1,0%.
  3. Un acier durcissant au vieillissement pour moule de coulée sous pression présentant une résistance supérieure aux craquelures par choc thermique et un meilleur rapport de variation dimensionnelle au vieillissement selon la revendication 1 ou 2, caractérisé en ce que la composition est contrôlée dans une valeur de N ≤ 0,0050%.
  4. Un acier durcissant au vieillissement pour moule de coulée sous pression présentant une résistance supérieure aux craquelures par choc thermique, un meilleur rapport de variation dimensionnelle au vieillissement et des cycles de fatigue réduits selon les revendications 1, 2 ou 3, caractérisé en ce que la proportion des inclusions de TiN d'un diamètre circulaire supérieur à 10 µm (micromètres) est inférieure ou égale à 2% de l'ensemble.
EP19960112457 1995-08-10 1996-08-01 Acier à durcissement par vieillissement pour moules de coulée sous pression Revoked EP0767251B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP227080/95 1995-08-10
JP22708095A JP3201711B2 (ja) 1995-08-10 1995-08-10 ダイカスト型用時効硬化鋼

Publications (2)

Publication Number Publication Date
EP0767251A1 EP0767251A1 (fr) 1997-04-09
EP0767251B1 true EP0767251B1 (fr) 1998-10-21

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EP19960112457 Revoked EP0767251B1 (fr) 1995-08-10 1996-08-01 Acier à durcissement par vieillissement pour moules de coulée sous pression

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EP (1) EP0767251B1 (fr)
JP (1) JP3201711B2 (fr)
DE (1) DE69600831T2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1094125B2 (fr) † 1999-03-19 2014-09-03 Honda Giken Kogyo Kabushiki Kaisha Acier maraging tres resistant a la fatigue et son procede de fabrication

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI107269B (fi) * 1998-12-02 2001-06-29 Metso Powdermet Oy Muottiteräs
CA2715998C (fr) * 2008-02-20 2015-07-28 Questek Innovations Llc Acier tres dur a ultra haute resistance
CN104087859A (zh) * 2014-07-02 2014-10-08 钢铁研究总院 钼强化10Ni7Co二次硬化超高强度钢及制备方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5161B1 (fr) * 1967-09-18 1976-01-05
AT374846B (de) * 1982-09-15 1984-06-12 Voest Alpine Ag Herzstueck, insbesondere herzstueckspitze, fuer schienenkreuzungen oder -weichen, sowie verfahren zu seiner herstellung
JPS60255959A (ja) * 1984-05-28 1985-12-17 Japan Steel Works Ltd:The 高硬度高飽和磁束密度合金鋼
JPS61190050A (ja) * 1985-02-20 1986-08-23 Hitachi Metals Ltd 高強度，高電気抵抗値および軟質な磁気特性を兼ね備えたマルエ−ジング鋼

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1094125B2 (fr) † 1999-03-19 2014-09-03 Honda Giken Kogyo Kabushiki Kaisha Acier maraging tres resistant a la fatigue et son procede de fabrication

Also Published As

Publication number Publication date
DE69600831T2 (de) 1999-04-08
EP0767251A1 (fr) 1997-04-09
JPH0949057A (ja) 1997-02-18
DE69600831D1 (de) 1998-11-26
JP3201711B2 (ja) 2001-08-27

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