Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/06—Alloys based on copper with nickel or cobalt as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/02—Alloys based on copper with tin as the next major constituent

Definitions

• the present invention relates to an alloy based on copper, nickel tin, lead and its manufacturing process.
• the present invention relates to an alloy based on copper, nickel, lead tin easily machinable by turning, bar turning or milling.
• Copper, nickel and tin based alloys are known and widely used. They offer excellent mechanical qualities and exhibit strong hardening during work hardening. Their mechanical properties are further improved by the thermal aging treatment known as spinodal decomposition. For an alloy containing, by weight, 15% of nickel and 8% of tin, (alloy standard ASTM 15 C72900) the mechanical resistance can reach 1500 MPa.
• Cu-Ni-Sn alloys offer good tribological properties, comparable to those of bronzes, while exhibiting superior mechanical properties.
• Cu-Be alloys have fairly good machinability and can compete with and even surpass the mechanical properties of Cu-Ni-Sn alloys.
• the machinability index of Cu-Be alloys can reach 50-60% compared to brass standard ASTM C36000. Their cost is however high and their production, use and recycling are particularly restrictive due to the high toxicity of beryllium.
• the resistance to thermal relaxation of the stresses of these materials is lower than that of Cu-Ni-Sn for temperatures above 150-175 ° C.
• a disadvantage of Cu-Ni-Sn alloys is that they do not lend themselves well to processes such as milling, turning or bar turning or any other known process.
• a subsequent drawback of these alloys is the high segregation that they exhibit during casting.
• a further aim of the present invention is to propose a method for producing a machinable product based on Cu-Ni-Sn which makes it possible to solve the problems linked to segregation.
• a machinable product composed of an alloy comprising between 1% and 20% by weight of Ni, between 1% and 20 % by weight of Sn, between 0.1% and 4% of Pb, the balance consisting essentially of Cu, having undergone a hot homogenization treatment comprising a step of heating said alloy followed by a step of cooling at a sufficiently speed slow to prevent cracking;
• the present invention relates to alloys based on copper, nickel, tin and lead obtained by a continuous or semi-continuous casting process, or static billet casting or by sprayforming casting.
• copper-nickel-tin have a wide solidification interval leading to significant segregation during casting.
• sprayforming also known under the name of the “Osprey” method, and described for example in patent EP0225732
• a metal billet is obtained by continuous deposition of atomized droplets. Segregation can take place only on the scale of atomized droplets. The dissemination routes required to reduce segregation are therefore shortened.
• the segregation is more pronounced than with the sprayforming process but it remains sufficiently reduced to avoid excessive brittleness of the alloy.
• Static billet casting leads to strong segregation which can only be eliminated by prolonged heat treatment.
• the product obtained will contain lead particles dispersed in a Cu-Ni-Sn matrix.
• lead has a lubricating effect and facilitates chip fragmentation.
• the amount of lead introduced into the alloy depends on the degree of machinability that one wishes to obtain. In general, an amount of lead of up to a few percent by weight can be introduced, without the mechanical qualities of the alloy at normal temperature being modified. However above the melting point of lead (327 ° C), liquid lead strongly weakens the alloy. Alloys containing lead are therefore difficult to manufacture, because on the one hand they have a very pronounced tendency to cracking, and on the other hand they can have a two-phase crystallographic structure containing an undesirable embrittling phase.
• the process of the present invention makes it possible to produce a machinable product of Cu-Ni-Sn-Pb containing up to a few percent by weight of lead, without it cracking during manufacture, and having excellent mechanical properties.
• the proportion of lead can vary between 0.1% and 4% by weight, preferably between 0.2% and 3% by weight, more preferably between 0.5% and 1.5% by weight.
• the manufacturing processes are broken down into successive blanks: For the first draft, two cases must be considered depending on whether the product is produced by continuous casting in small diameter or by static casting in billets, sprayforming, semi-continuous casting or continuous casting in large diameter.
• the products of the invention are characterized for their excellent machinability, which is superior to that of CuBe alloys.
• the machinability index of the alloys of the invention exceeds 80% compared to the brass standard ASTM C36000, and can go up to 90%.
• the temperature of the heat treatment must be in the area where the alloy is single phase.
• the cooling after the heat treatment must have a sufficiently slow speed to prevent cracking of the alloy following the internal stresses generated by the temperature differences during cooling, and fast enough to limit the formation of a two-phase structure. If the speed is too slow, a significant amount of second phase may appear. This second phase is very fragile and greatly reduces the deformability of the alloy.
• the critical rate of cooling required to avoid the formation of too much second phase depends on the chemistry of the alloy and is higher for a larger amount of nickel and tin.
• transient internal stresses are generated in the alloy. They are related to temperature differences between the surface and the center of the product. If these stresses exceed the resistance of the alloy, it will crack and no longer be usable.
• the internal stresses due to cooling are higher the larger the diameter of the product.
• the critical cooling rates to avoid cracking therefore depend on the diameter of the product. This problem is all the more acute with Cu-Ni-Sn-Pb alloys because above its melting temperature, 327 ° C, lead weakens the alloy very strongly.
• the cooling after heat treatment takes place at a predetermined speed taking into account the chemistry of the alloy and the transverse dimension, or diameter, of the product.
• the cooling rate must be both slow enough to prevent cracking and at the same time significant enough to prevent the formation of too much embrittling phase.
• the alloys obtained by the sprayforming, static billet casting or semi-continuous casting processes are subjected to a hot extrusion treatment. This is also the case for continuous casting if the product has a large diameter. Cooling during extrusion must be slow enough to prevent cracking and fast enough to limit the formation of a second embrittling phase. Alternatively, if the cooling during the extrusion is too slow, heat treatments for homogenization and recrystallization as explained above for the case of continuous casting products of small diameter must follow the extrusion.
• the final machinable product can either be obtained directly by one or more cold deformation operations, for example by rolling, drawing, drawing, hammering or any other cold deformation process, or obtained by one or more several successive drafts.
• the following blanks are obtained by one or more cold deformation operations followed by a recrystallization heat treatment.
• the temperature of the recrystallization treatment must be in the range where the alloy is single phase. Cooling after heat treatment must be slow enough to prevent cracking, but always fast enough to limit the formation of a two-phase structure. By successive drafts the dimensions of the product are reduced. From the last draft, the final product is obtained by one or more cold deformation operations.
• the mechanical properties of the alloy obtained can be further increased by a thermal decomposition treatment spinodal. This treatment can take place before or after the final machining. Examples of processes and products which can be machined according to the present invention are presented below. In the following examples the cooling temperatures refer to the center of the product.
• Example 1 The chemical composition of the alloy in this example is given in Table 1: Table 1
• Manganese is introduced into the composition as a deoxidizer. It is however possible to use in its place other elements or devices intended to prevent the oxidation of the alloy.
• This alloy can be cast using the various methods mentioned above.
• this alloy is obtained by continuous casting of billets whose diameter is 180 mm.
• the billets are extruded for example to a diameter of 18 mm.
• the alloy is cooled by a flow of compressed air making it possible to obtain a cooling rate of 50 to 300 ° C / min, measured at the center of the alloy. This speed is slow enough to avoid cracking and fast enough to limit the formation of a second embrittling phase.
• Water mist cooling can also be used, possibly achieving cooling rates of 300 to 1000 ° C / min without cracking the material. Other means making it possible to obtain a suitable cooling rate can also be used.
• the alloy will have to undergo a homogenization treatment with the same characteristics for the cooling rate.
• a temperature in the range where the alloy is single phase between 690 ° C and 920 ° C for the composition of table 1.
• 2 ee blank the material of the first preform to the diameter of 10 18 mm is laminated to the diameter 13 mm and then annealed in a pass-through oven or in a bell oven.
• the annealing temperature must be between 690 and 920 ° C.
• a cooling rate of the order of 10 ° C / min is sufficient to limit the formation of second phase for this composition and this diameter of 13 mm. Furthermore, cooling by water mist at speeds of 300 ° C / min to 3000 ° C / min makes it possible to avoid cracking and to limit the formation of a second embrittling phase. Finishing: the material of the second blank is drawn or drawn to a diameter of 8 mm to obtain a machinable product. A spinodal decomposition treatment is finally carried out on the workable product or on the workpieces to obtain the optimum mechanical properties.
• Example 2 The chemical composition of the alloy in this example is given in Table 2: Table 2? ⁇ Component Proportion (weight) Cu balance Ni 9% Sn 6% Pb 1% Mn 0.1% -1% Impurities ⁇ 0.5%
• this alloy is obtained by continuous casting of wire whose diameter is 18 mm.
• First draft the wire undergoes a homogenization treatment in a passage oven at a temperature between 700 and 920 ° C, corresponding to the single-phase range of the chemical composition of Example 2.
• a cooling rate of between 100 and 1000 ° C / min makes it possible to avoid cracking and to limit the proportion of weakening second phase.
• Such cooling rates can for example be obtained using compressed air, a water mist or a gas / water exchanger cooler.
• 2nd draft the material of the first preform to the diameter of 18 mm is rolled, or hammered tréfilée the diameter 13 mm and then annealed in a continuous furnace at a temperature between 700 and 920 ° C.
• a cooling rate of between 100 and 3000 ° C / min makes it possible to limit the formation of the second phase while avoiding cracking.
• 3rd draft the material of the second preform to the diameter of 13 mm is rolled, or hammered tréfilée the diameter 10 mm and then annealed in a continuous furnace or a tempering furnace at a temperature between 700 and 920 ° C.
• a cooling rate of between 100 and 15,000 ° C / min makes it possible to limit the formation of the second phase without creating cracks.
• 4 th draft the material of the third draft of the diameter
• 10 mm is rolled, drawn or hammered to a diameter of 7 mm and then annealed in a pass-through oven or in a quenching oven at a temperature between 700 and 920 ° C.
• a cooling rate of between 100 and 20,000 ° C / min makes it possible to limit the formation of the second phase without creating cracks.
• 5th blank the material of the fourth preform to the diameter of 7 mm is rolled, or hammered tréfilée the diameter of 5 mm and then annealed in a continuous furnace or a tempering furnace at a temperature between 700 and 920 ° C.
• a cooling rate of between 100 and 30,000 ° C / min makes it possible to limit the formation of the second phase without creating cracks.
• a cooling rate of the order of 15000 ° C / min can be obtained by quenching in suitable fluids.
• 6 th blank the material of the fifth blank to the diameter of 5 mm is laminated, tréfilée or hammered in diameter 3 mm, annealed in a passage furnace or a tempering furnace at a temperature between 700 and 920 ° C, then cooled at a cooling rate of between 100 and 40,000 ° C min.
• the material of the sixth blank to the diameter of 3 mm is laminated, tréfilée or hammered to the diameter 2 mm, annealed in a continuous furnace or a tempering furnace at a temperature between 700 and 920 ° C, then cooled at a cooling rate of between 100 and 40,000 ° C / min.
• the material of the seventh blank with a diameter of 2 mm is rolled, drawn or hammered to a diameter of 1.60 mm, annealed in a pass-through oven or in a quenching oven at a temperature between 700 and 920 ° C. then cooled at a cooling rate of between 100 and 50,000 ° C / min.
• the material of the eighth blank is drawn or drawn to a diameter of 1 mm to obtain a machinable product.
• a spinodal decomposition treatment is finally carried out on the machinable product or on the machined parts to obtain optimal mechanical properties.
• the ASTM test method for machinability test provides a method for determining the machinability index in relation to brass standard CuZn39Pb3, or brass C36000.
• the machinability index of the alloy according to this aspect of the invention is better by 80%.
• the chemical composition of the alloy of this example is the same as that of the second example given in Table 2.
• the alloy is obtained by continuous casting with a diameter of 25 mm.
• First draft the cast wire with a diameter of 25 mm is hammered with a diameter of 16 mm. Hammering makes it possible to deform the material with a significant reduction rate without heat treatment of prior homogenization. With this process a high residual rate of second embrittling phase can be tolerated at this stage.
• the second phase can reach a volume proportion of the order of 50%.
• After hammering the wire with a diameter of 16 mm undergoes a heat treatment of homogenization and recrystallization in a passage oven.
• the temperature of the heat treatment must be between 700 ° C and 920 ° C.
• the next cooling takes place at a speed of between 100 and 3000 ° C / min. These cooling rates make it possible to avoid the formation of cracks and limit the proportion of second phase for a product of this diameter and of this composition. Such speeds can be obtained using compressed air, water mist or gas / water exchangers. Finishing: the material of the first blank is drawn or drawn to a diameter of 10 mm to obtain a machinable product. A spinodal decomposition treatment is finally carried out on the machinable product or on the machined parts to obtain optimal mechanical properties.
• the chemical composition of the alloy in this example is given in Table 3: Table 3 Component Proportion (weight) Cu balance Ni 15% Sn 8% Pb 1% Mn 0.1% -1% Impurities ⁇ 0.5%
• This alloy can be poured according to the different processes - mentioned above. In this example, this alloy is obtained by sprayforming billets whose diameter is 240 mm. 5 First draft: the billets are extruded, for example to a diameter of 20 mm. If the dimensional irregularities of the billets are too large, a turning step may be necessary before extrusion. At the outlet of the extrusion die, the alloy is cooled by a water mist making it possible to obtain a cooling rate of
• 2nd blank the material of the first blank with a diameter of 20 to 20 mm is hammered with a diameter of 11 mm and then annealed in a passage oven.
• the annealing temperature must be between 780 and 920 ° C.
• a cooling rate of between 300 and 15,000 ° C / min 25 makes it possible to limit the presence of second phase while avoiding cracking.
• the use of hammering allows significant hardening rates even with a fragile material. With this process the residual rate second embrittling phase can be higher than with rolling, drawing or drawing processes. It can reach values of the order of 50% by volume.
• Third blank the material of the second blank with a diameter of 11 mm is hammered with a diameter of 6.5 mm and then annealed in a passage oven or a quenching oven at a temperature between 780 and 920 ° C. With a diameter of 6.5 mm, the alloy in Table 3 allows cooling rates between 300 and 20,000 ° C / min without cracking. These speeds make it possible to limit the proportion of weakening second phase. Finishing: the material of the third blank is drawn or drawn to a diameter of 4 mm to obtain a machinable product. A spinodal decomposition treatment is finally carried out on the machinable product or on the machined parts to obtain optimal mechanical properties.
• Cooling test Samples of the alloy of the invention were subjected to rapid cooling tests to determine the appearance of cracking.
• the chemical composition of the alloy in this test is given in Table 2.
• the samples were subjected to a heat treatment at a temperature of 800 ° C. and then rapidly cooled by immersion in a quenching fluid (EXXON XD90) and in the water.
• the test shows that diameters up to about 10 mm can tolerate cooling in a quenching fluid. Water quenching, on the other hand, always led to cracking of the sample, and this up to a minimum diameter of 4 mm.
• cooling rates higher than 24000 ° C / min can be used.
• water quenching can be effective if the size of the product is small enough to limit transient internal stresses and thus avoid the formation of cracks.
• the machinable products of examples 1, 2, 3 and 4 can each be produced by the methods of examples 1, 2, 3 and 4 provided that the cooling rates and temperatures of the heat treatments are adapted to the chemical compositions and to the dimensions.
• the number of blanks can vary depending on the size of the finished product.
• Part of the copper of the alloys of the present invention can be replaced by other elements, for example Fe, Zn or Mn, in a proportion ranging for example up to 10%.
• Other elements such as for example Nb, Cr, Mg, Zr and Al may also be present, in a proportion of up to a few percent. Among other things, these elements have the effect of improving spinodal hardening.

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• 2004
  • 2004-04-05 BR BRPI0418718-0A patent/BRPI0418718A/pt not_active Application Discontinuation
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