Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
• • 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
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
  • C22C21/16—Alloys based on aluminium with copper as the next major constituent with magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C37/00—Manufacture of metal sheets, rods, wire, tubes, profiles or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
  • B21C37/06—Manufacture of metal sheets, rods, wire, tubes, profiles or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
• • 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
  • B21D53/00—Making other particular articles
  • B21D53/02—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers
  • B21D53/06—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers of metal tubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
  • B32B15/016—Layered products comprising a layer of metal all layers being exclusively metallic all layers being formed of aluminium or aluminium alloys
• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C30/00—Alloys containing less than 50% by weight of each constituent
  • C22C30/02—Alloys containing less than 50% by weight of each constituent containing copper
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C30/00—Alloys containing less than 50% by weight of each constituent
  • C22C30/06—Alloys containing less than 50% by weight of each constituent containing zinc
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/02—Tubular elements of cross-section which is non-circular
  • F28F1/06—Tubular elements of cross-section which is non-circular crimped or corrugated in cross-section
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/40—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only inside the tubular element
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
  • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
  • F28F21/081—Heat exchange elements made from metals or metal alloys
  • F28F21/084—Heat exchange elements made from metals or metal alloys from aluminium or aluminium alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C23/00—Extruding metal; Impact extrusion
  • B21C23/002—Extruding materials of special alloys so far as the composition of the alloy requires or permits special extruding methods of sequences
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C23/00—Extruding metal; Impact extrusion
  • B21C23/02—Making uncoated products
  • B21C23/04—Making uncoated products by direct extrusion
  • B21C23/08—Making wire, rods or tubes
  • B21C23/10—Making finned tubes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F2255/00—Heat exchanger elements made of materials having special features or resulting from particular manufacturing processes
  • F28F2255/16—Heat exchanger elements made of materials having special features or resulting from particular manufacturing processes extruded

Definitions

• the invention relates to an aluminium alloy for use in tubes for heat exchangers and to tubes produced from the alloy.
• the tubes preferably have inner helical grooves or inner straight grooves or a combination of straight and helical grooves.
• the invention also relates to heat exchangers comprising the tubes.
• heat transfer tubes for heat exchangers it is important to assure an efficient heat transfer performance of the tube. It is known to provide heat transfer tubes with alternating grooves on their inner surfaces. The grooves cooperate to enhance turbulence of fluid heat transfer mediums, such as water, delivered within the tube. This turbulence increases the fluid mixing close to the inner tube surface to reduce or virtually eliminate the boundary layer build-up of the fluid medium close to the inner surface of the tube which may otherwise increase the heat transfer resistance of the tube.
• the grooves and ridges also provide extra surface area for additional heat exchange.
• Helically grooved tubes (hereinafter HG tube) are widely applied in heat exchangers in domestic and commercial air conditioners, heat pump water heaters etc.
• the process for internal grooving of heat exchanger tubes are known from e g EP1866119.
• the alloy used for HG tubes in the market is mainly AA3003 or AA3003 with zinc arc spray coating for better corrosion resistance.
• There is a demand for corrosion resistant heat exchangers and so called“long-life” alloys are used in many applications to meet the requirements. Existing long-life alloys however cannot be applied to make helically grooved tubes because of the limitation in drawability and tensile strength.
• AA3003 alloy HG tubes do not meet the corrosion resistance requirements in the market, while it has excellent drawability and high tensile strength, as well as good endurance to the tough helical grooving process.
• the corrosion resistance may be improved by spraying the tubes with a Zn coating.
• the cost will be increased a lot because of zinc arc spray and zinc diffusion annealing processes. Consequently, there is a need for a long-life alloy, which is suitable for making a helically grooved tube.
• one aspect of the invention relates to an aluminium alloy preferably comprising 1.0-1.5 wt% Mn, up to 0.1 wt% Mg, up to 0.3 wt% Si: up to 0.3 wt% Fe, up to 0.1 wt% Cu, up to 0.25 wt% Cr, up to 0.1 wt% Ni, up to 0.3 wt% Zn, up to 0.1 wt% Ti, up to 0.2 wt% Zr and unavoidable impurities, each 0.05 wt.% maximum and the total of impurities 0.15 wt.% maximum, balance aluminium.
• Another aspect of the invention relates to an aluminium tube produced from the alloy according to the invention.
• a further aspect of the invention relates to heat exchanger comprising tubes and fins, wherein the tubes are made from the aluminium tube according to the invention.
• the alloy according to the invention is suitable for making corrosion resistant tubes for heat exchangers.
• the alloy is suited for making helically grooved tubes due to its mechanical strength and formability in combination with its corrosion resistance properties.
• Heat transfer tubes are commonly used in equipment, for example, evaporators, condensers, coolers and heaters, used in the automotive and HVAC&R sector.
• a variety of heat transfer mediums may be used in these applications, including, but not limited to, pure water, a water glycol mixture, any type of refrigerant (such as R- 22, R-134a, R-123, R410a etc.), ammonia, petrochemical fluids, and other mixtures.
• Figure 1 shows the time to perforation of tubes of alloy A according to the invention and tubes made from alloy B with and without a Zn coating.
• Figure 2a shows a cross section of a leaking tube from a tube of alloy B after 7 days of SWAAT testing
• Figure 2b shows a cross section of a non-perforated tube from an alloy A according to the invention after 118 days of SWAAT testing
• Figure 5 Mechanical properties of a helically grooved tube according to the invention after in-line anneal compared to a tube made from alloy B.
• the alloy in Table 1 is a long-life alloy specification according to the invention for making heat exchanger tubes.
• the chemical composition comprises 1.0-1.5 wt% Mn, up to 0.1 wt% Mg, preferably 0.08 wt% Mg, up to 0.3 wt% Si: up to 0.3 wt% Fe, up to 0.1 wt% Cu, up to 0.25 wt% Cr, up to 0.1 wt% Ni, up to 0.3 wt% Zn, up to 0.2 wt% Ti, up to 0.2 wt% Zr and unavoidable impurities, each 0.05 wt.% maximum and the total of impurities 0.15 wt.% maximum, balance Aluminium.
• the alloy of the invention relates to an aluminium alloy comprising 1.0-1.2 wt% Mn, up to 0.1 wt% Mg, preferably 0.08 wt% Mg, 0.10-0.15 wt% Si: up to 0.3 wt%
• Fe up to 0.05 wt% Cu, up to 0.03-0.2 wt% Cr, up to 0.05 wt% Ni, up to 0.2-0.3 wt% Zn, up to 0.1 wt% Ti, up to 0.2 wt% Zr and unavoidable impurities, each 0.05 wt.% maximum and the total of impurities 0.15 wt.% maximum, balance aluminium.
• the alloy invention relates to an aluminium alloy comprising 1.0-1.1 wt% Mn, up to 0.05 wt% Mg, 0.10-0.15 wt% Si: up to 0.3 wt% Fe, up to 0.05 wt% Cu, 0.05- 0.1 wt% Cr, preferably 0.0 up to 0.05 wt% Ni, 0.2-0.25 wt% Zn, up to 0.05 wt% Ti, up to 0.05 wt% Zr and unavoidable impurities, each 0.05 wt.% maximum and the total of impurities 0.15 wt.% maximum, balance aluminium.
• the invention also relates to an aluminium tube produced from such aluminium alloys, in particular to tubes having an internally grooved surface. The internal grooves preferably have a height of at least 0.05 mm.
• the invention also relates to a heat exchanger comprising tubes and fins, wherein the tubes are made from the inventive aluminium tubes, the heat exchanger preferably being made by inserting the tubes in holes in plates forming the fins of the heat exchanger.
• the heat exchanger may also be a serpentine heat exchanger formed by parallel multiport extruded tubes between which undulating aluminium fins are brazed.
• the inventive alloy is a combination of carefully selected elements in ranges that provide properties that are particularly suitable for heat exchanger tubes with internal grooves.
• Mn is the main additive element for improving the alloy strength, if the Mn amount is less than 1.0 wt%, the strength of the alloy is insufficient to undergo the helical grooving process and may cause tube breakage. If the Mn content exceeds 1.5 wt%, the tube expansion becomes difficult since the material will become too hard and more force will be needed to expand the tube which will cause the fins inside of the tube to collapse, and the tube is at risk of being bent due to high friction between the fins and the billet during expansion which will impact the tube corrosion resistance post brazing.
• the preferred content of Mn is 1.0-1.2 wt%, more preferably 1.0-1.1 wt%.
• Mg should be ⁇ 0.1 wt%, preferably ⁇ 0.08 wt%, most preferably ⁇ 0.05 wt% to get good brazing of the heat exchanger with Nocolok flux application.
• Si and Fe is controlled to ⁇ 0.3 wt% each for improving the corrosion resistance.
• the content of Si should preferably be 0.10-0.15 wt% to improve the corrosion resistance performance.
• Cr is added for refining the grain structure and improving alloy strength and corrosion resistance, but it needs to be controlled to ⁇ 0.25 wt%, preferably ⁇ 0.05 -0.2 wt%, more preferably ⁇ 0.05-0.1 wt% for good extrudability and good formability during the helical grooving process.
• Cu shall be ⁇ 0.1 wt%, preferably the Cu content shall be ⁇ 0.05 wt% for good corrosion resistance of the tube.
• Zn is an important element to add up to 0.3 wt% for improving pit corrosion resistance, driving corrosion uniform around tube surface.
• the content of Zn is 0.1 wt%- 0.3 wt%, preferably 0.2-0.3 wt%, more preferably 0.25-0.3 wt%.
• Fe is controlled to be up to 0.3 wt% Fe since higher contents may affect the corrosion resistance negatively.
• High Fe-containing particles act as cathodes dissolving anodic surroundings.
• Ni is known to be very detrimental to the intergranular corrosion resistance and should be limited to ⁇ 0.1 wt%, preferably ⁇ 0.05 wt%.
• Ti is primarily used for grain refining but is also used to improve the corrosion
• the Ti content should be limited to ⁇ 0.2 wt%, ⁇ 0.1 wt%, preferably ⁇ 0.05 wt%.
• Zr is considered positive to corrosion due to a positive effect on the size of intermetallics and may be added up to 0.2 wt%.
• the formed intermetallic AI3Zr is not known to be active in a corrosive environment and thus not detrimental to the corrosion resistance. If adding more than 0.2wt% Zr the alloy cost will be high due to Zr being an expensive element. Alloys comprising >0.2wt% Zr will also be more difficult to recycle and have a lower formability. Tests have been made to compare the corrosion resistance of an alloy A according to the invention with an alloy B with slightly higher contents of Si, Fe and Ti, but lower contents of Zn and Cr. The combined content of Zinc, Si and Fe in the alloy according to the invention is the main reason for the excellent corrosion resistance.
• Fig 2a is a photo of a cross section of the tube made from Alloy B which shows leakage already after 7 days of testing in SWAAT.
• the mode of corroding is pit corrosion, while in Fig 2b a cross section of a alloy A tube a more uniform corrosion has taken place and the Alloy A tubes leaked only after 118 days SWAAT.
• the balls are driven by a motor that spin at high speed and presses aluminium into the die for helical grooving.
• the outer diameter is decided by assembly dimension of gear box size and steel ball diameter, which rotate surrounding the tube. To pass the grooving process, it is necessary that the alloy has a good formability and a high strength.
• the tube (1 ) After helical grooving, the tube (1 ) will have a ball mark and may need to pass a sink drawing unit comprising a drawing die and a drawing plug for smoothing the outer surface and obtain the final tube size.
• Figure 4 shows the tensile strength of tubes tested according to EN 755-2.
• the tensile strength of the FIG tubes made from alloy A according to the invention is all little bit lower than for the tubes made from alloy B, but the strength is good enough to ensure a reliable manufacturing by the helical grooving process.
• the reduction of the tube dimensions during the drawing after different number of passes through the drawing station is shown in Figure 6.
• the drawing test is outlined in fig 6.
• the pillars in the graph shows the % reduction of the dimensions in each draw.
• the total drawing deformation of the tubes was 81 %.
• the outer diameter can be from 5 to 10 mm, wall thickness 0.35 -0.7 mm, fin height max 0.35 mm and fin numbers max 50.
• a heat exchanger with enhanced heat transfer performance is produced by forming internal grooves on the inside of tubes that are to be inserted into an insertion hole opened in an aluminum heat dissipating fin (also called fin and tube type heat exchanger) and then inserting a mandrel for expanding the tube having an outer diameter larger than the inner diameter of the heat transfer tube, and the outer peripheral surface of the heat transfer tube is in close contact with the insertion hole of the aluminum heat dissipating fin.
• an aluminum heat dissipating fin also called fin and tube type heat exchanger
• the alloy according to the invention can also be used to produce regular round tubes and to extrude micro-channel flat tubes (MPEs).
• Preferred dimensions for smooth tubes are diameters from 5-30 mm and wall thicknesses above 0.3 mm.
• Preferred dimensions for MPEs are widths down to 8 mm, with minimum heights of 1 mm, and wall thicknesses above 0.15 mm.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Geometry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Extrusion Of Metal (AREA)

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• 2019
  • 2019-07-22 CN CN201910661744.0A patent/CN112254563A/zh active Pending
  • 2019-11-21 KR KR1020267005910A patent/KR20260036039A/ko active Pending
  • 2019-11-21 MX MX2022000821A patent/MX2022000821A/es unknown
  • 2019-11-21 US US17/626,748 patent/US12584197B2/en active Active
  • 2019-11-21 EP EP19938404.1A patent/EP4004476A4/en active Pending
  • 2019-11-21 JP JP2022502397A patent/JP7524299B2/ja active Active
  • 2019-11-21 WO PCT/IB2019/060038 patent/WO2021014203A1/en not_active Ceased
  • 2019-11-21 KR KR1020227001500A patent/KR20220035127A/ko not_active Ceased

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