Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/06—Alloys based on aluminium with magnesium as the next major constituent
  • C22C21/08—Alloys based on aluminium with magnesium as the next major constituent with silicon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2030/00—Pneumatic or solid tyres or parts thereof

Definitions

• This invention relates to an aluminum alloy suitable as a starting material of a tire mold used in the vulcanization building of tires, and more particularly to a casting aluminum alloy and a tire mold comprising such an aluminum alloy.
• a tire mold (hereinafter referred to as “mold” simply), particularly a so-called split mold consisting of plural mold segments is commonly made from an aluminum alloy from a viewpoint of the casting property.
• the casting aluminum alloy used in the tire mold are known AC2B, AC4C and AC7A defined in JIS H5202 (1992), which is disclosed in Non-Ferrous Metals of JIS HANDBOOK.
• These aluminum alloys are easy in the plastic deformation because an elastic limit strain ⁇ e is as small as 0.04% in AC2B system, 0.10% in AC4C system and 0.12% in AC7A system.
• the local deformation of the mold is caused in the repeated opening-closing operations, particularly in the fitting of the mold segments.
• the local deformation results in the deformation of the inner face form of the mold, which brings about the deterioration of RR in the tire or the poor fitting among the mutual mold segments in the split mold and hence disadvantageously produces a rubber-protruded tire.
• Such a local deformation of the mold is usually generated in about one year starting from the use in the vulcanization building of the tires, so that it is obliged to conduct the repairing of the mold at a cycle of one year.
• an object of the invention to propose a way for enhancing an elastic limit strain of a casting aluminum alloy in order to suppress the local deformation of the mold made of the aluminum alloy.
• the construction of the invention is as follows.
• An aluminum alloy for a tire mold comprising Mg: 3.0-6.0 mass %, Si: 0.2-4.5 mass % and the balance being Al and inevitable impurities.
• An aluminum alloy for a tire mold according to the item (1) which further contains at least one of Cu: not more than 0.10 mass %, Zn: not more than 0.10 mass %, Fe: not more than 0.10 mass %, Mn: not more than 0.10 mass %, Ni: not more than 0.05 mass %, Ti: 0.01-0.30 mass %, Sn: not more than 0.05 mass %, Cr: not more than 0.10 mass %, B: not more than 0.10 mass %, Ag: not more than 0.10 mass % and Ca: not more than 0.10 mass %.
• a tire mold for use in vulcanization building of a tire which comprises an aluminum alloy as described in the item (1) or (2).
• the design for enhancing the elastic limit strain can be given to the casting aluminum alloy. Therefore, by using such an aluminum alloy can be improved mechanical properties of a cast mold made of the aluminum alloy, and particularly the local deformation is suppressed during the vulcanization building, and hence it is possible to prolong the service life of the mold.
• Mg is a solid-solution strengthening element and is included for strengthening the grain boundary with Al—Mg precipitates. Also, Mg having an atomic radius larger than that of Al is inhabited in the crystal grain to form Guinier-Preston zone (GP zone), and the elasticity can be maintained by the GP zone. That is, the GP zone is a stacking fault due to aggregation of solid-solution elements.
• the solid-solution strengthening by the GP zone appearingly serves as a dispersion strengthening to trap dislocation causing loss of elasticity, and hence the elastic limit increases and the strength rises. For this end, it is required to include nor less than 3.0 mass % of Mg. On the other hand, when the content of Mg exceeds 6.0 mass %, the stable GP zone is not formed and the scattering of the properties inclusive of elastic limit becomes large every the cast lot and further the castability is considerably deteriorated and the precision casting is difficult.
• Si contributes to strengthen the grain boundary by an eutectic system with Al. Since Al—Si eutectic is easily peeled off from Al matrix, it is required that Al—Mg—Si based inclusion is produced at the solidification stage of the casting and bonded to the Al—Si eutectic to prevent the crystal slippage at the grain boundary. For this end, it is required to include not less than 0.2 mass % of Si. Particularly, in order to produce the Al—Mg—Si based inclusion at the solidification stage of the casting, the aforementioned inclusion of not less than 3.0 mass % of Mg is required in addition to not less than 0.2 mass % of Si.
• the Al—Mg—Si based inclusion produces Al—Mg 2 Si fine precipitates, and the Al—Mg 2 Si also forms the GP zone to bring about the improvement of the elastic limit likewise the above case.
• the Al—Mg 2 Si is preferentially precipitated in the grain boundary to easily cause embrittlement, so that Si is required to be not more than 4.5 mass %.
• the balance other than Mg and Si is Al and inevitable impurities.
• one or more of Cu, Zn, Fe, Mn, Ni, Ti, Sn, Cr, B, Ag and Ca may be included in addition to the above components, if necessary.
• Sn, B, Ca and Cr are existent as an inevitable impurity.
• a preferable content range of each of these components is as follows.
• Cu is preferably added in an amount of not less than 0.05 mass % in order to stably produce the Al—Mg based GP zone and Al—Mg 2 Si based GP zone, but when the addition amount of Cu exceeds 0.10 mass %, the above GP zones are segregated to make the scattering of the properties large, so that the upper limit is 0.10 mass %.
• Zn is is preferably added in an amount of not less than 0.05 mass % in order to stably produce the Al—Mg based GP zone and Al—Mg 2 Si based GP zone, but when the addition amount of Zn exceeds 0.10 mass %, there is a fear that Al—Mg 2 Si is preferentially precipitated in the grain boundary to induce the intergranular cracking, so that the upper limit is 0.10 mass %.
• Fe is preferably added in an amount of not less than 0.05 mass %.
• the addition amount exceeds 0.10 mass %, the castability is obstructed, so that the upper limit is 0.10 mass %.
• Mn is preferably added in an amount of not less than 0.05 mass % for improving the heat resistance, but when the addition amount exceeds 0.10 mass %, the castability is obstructed, so that the upper limit is 0.10 mass %.
• Ni not more than 0.05 mass %
• Ni is preferably added in an amount of not less than 0.03 mass % for improving the heat resistance and elastic limit, but when the addition amount exceeds 0.05 mass %, the castability is obstructed, so that the upper limit is 0.05 mass %.
• Ti is added in an amount of not less than 0.01 mass % for forming fine grain boundary, but when the addition amount exceeds 0.30 mass %, the effect of forming the fine grain boundary is unchangeable, so that the upper limit is 0.30 mass %.
• Sn is incorporated as an inevitable impurity, but when the content exceeds 0.05 mass %, the castability is obstructed, so that the content is controlled to not more than 0.05 mass %.
• Cr is also incorporated as an inevitable impurity, but when the content exceeds 0.10 mass %, the properties are obstructed, so that the content is controlled to not more than 0.10 mass %.
• B is also incorporated as an inevitable impurity, but when the content exceeds 0.10 mass %, the properties, particularly elongation are obstructed, so that the content is controlled to not more than 0.10 mass %.
• Ag is preferably added in an amount of not less than 0.01 mass % for making finer the size of the polycrystalline alloy up to nano-size, but when the content exceeds 0.10 mass %, the effect of making the size finer is saturated, so that the upper limit is 0.10 mass %.
• Ca is incorporated as an inevitable impurity, but when the content exceeds 0.10 mass %, the castability is obstructed, so that the content is controlled to not more than 0.10 mass %.
• the aluminum alloy having the aforementioned composition is first produced as an ingot, which is cast through a melting furnace and a holding furnace to form a cast slab and then the resulting cast slab is reshaped through elastic and plastic deformations and finally subjected to a machine work to form a mold.
• the mold repairing cycle means a cycle required for repairing the spue-generated mold in the continuous use of the mold, which is evaluated from the mold-repairing result.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

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• 2007
  • 2007-03-23 JP JP2007077512A patent/JP2008231565A/ja not_active Withdrawn
• 2008
  • 2008-03-05 US US12/073,471 patent/US20080233000A1/en not_active Abandoned
  • 2008-03-11 EP EP08250827A patent/EP1972697A1/fr not_active Withdrawn

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