RU2348720C2 - Machinable alloy on basis of copper and method of its manufacturing - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention concerns obtaining of metal product made of alloy on the basis of copper, tractable by turning, cutting or rolling. Blank made of alloy, containing, wt %: nickel 1-20, tin 1-20, lead 0.2-3, copper - the rest, is received by continuous casting with following forging, casting into molds, spray-type moulding or semicontinuous casting with following extrusion. Thermal treatment of blank by homogenizing annealing is implemented at temperature of single-phase structure existing with cooling with speed, providing prevention of cracking and restriction of two-phase structure moulding. Product machinability index from declared alloys exceed 80% relative to bronze in concordance with standard ASTM C36000 and can reach even 90%.

EFFECT: obtaining of metal product from alloy on the basis of copper, tractable by turning, cutting or rolling.

14 cl, 5 tbl, 4 ex

Description

FIELD OF TECHNOLOGY

The present invention relates to an alloy based on copper, nickel, tin, lead and to a method for its production. In particular, the present invention relates to an alloy based on copper, nickel, tin, lead, easily processed by turning, cutting or rolling.

BACKGROUND

Alloys based on copper, nickel and tin are known and widely used. They have high mechanical properties and show strong hardening during strain hardening. Their mechanical properties are further improved by a known heat aging treatment, such as spinodal decomposition. The mechanical resistance of an alloy containing 15 wt.% Nickel and 8 wt.% Tin (alloy in accordance with ASTM C72900) can reach 1500 MPa.

Another advantageous property of Cu-Ni-Sn alloys is that they have high tribological properties comparable to those of bronzes and at the same time show excellent mechanical properties.

Another advantage of these materials lies in their good formability, combined with high elastic properties. In addition, these alloys have high corrosion resistance and high resistance to thermal stress relaxation. For this reason, springs from Cu-Ni-Sn alloys do not lose compressive force during aging, under vibrations and strong thermal stresses.

These beneficial properties, combined with high thermal and electrical conductivity, ensure the wide use of these materials for the manufacture of highly reliable connectors for telecommunications and the automotive industry. These alloys are also used in separate switches (switches) and electrical or electromechanical devices or as substrates of electronic blocks or for the manufacture of supporting friction surfaces subjected to high loads.

Cu-Be alloys can be machined quite well and can compete in mechanical properties with Cu-Ni-Sn alloys and even surpass them. The machinability of Cu-Be alloys can reach 50-60% relative to brass in accordance with ASTM C36000. However, their cost is high and their production, use and return to recycling are largely restrained due to the high toxicity of beryllium. The resistance of these materials to thermal stress relaxation is lower than the resistance of Cu-Ni-Sn for temperatures above 150-175 ° C.

One drawback of Cu-Ni-Sn alloys is that they are poorly suited to processes such as rolling, turning or cutting, or any other known process. An additional drawback of these alloys is the strong segregation during casting.

Therefore, it is an object of the present invention to provide an alloy combining the advantageous mechanical properties of copper, nickel and tin based alloys with high machinability.

Another objective of the present invention is to provide a method of manufacturing a machinable product based on Cu-Ni-Sn, which does not have the disadvantages of prior art methods.

Another objective of the present invention is to provide a machinable alloy having high elasticity and mechanical resistance and not containing beryllium or toxic elements.

An additional objective of the present invention is to provide a method of manufacturing a machinable product based on Cu-Ni-Sn, providing the ability to solve problems associated with segregation.

These problems are solved in the product and method, which are the objects of the independent claims, in that the machinable product consists of an alloy containing from 1 to 20 wt.% Ni, from 1 to 20 wt.% Sn, from 0.1 up to 4 wt.% Pb, the rest, essentially, is copper subjected to heat-homogenizing treatment, including the step of heating the alloy followed by a cooling step at a sufficiently slow speed to prevent cracking.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to alloys based on copper, nickel, tin and lead obtained by continuous or semi-continuous casting, "static" casting into billets or by injection molding. Copper-nickel-tin alloys have a long solidification period, which leads to a noticeable segregation during casting. Of the four above methods, the injection molding method, also known as the “Osprey” method and disclosed, for example, in EP0225732, makes it possible to obtain an almost uniform microstructure indicating a minimal degree of segregation. In this method, a metal preform is obtained by continuous deposition of atomized droplets. Segregation can only occur on a film of atomized droplets. The diffusion distances needed to reduce segregation are therefore reduced. In the case of continuous or semi-continuous casting, segregation is stronger than in the method of spray molding, but it remains small enough to avoid excessive brittleness of the alloy. “Static” casting into billets leads to strong segregation, which can be eliminated only by long-term heat treatment.

Lead is essentially insoluble in other metals of the alloy, and therefore the resulting product will contain lead particles dispersed in a Cu-Ni-Sn matrix. During machining operations, lead has a lubricating effect and facilitates the breakdown of films.

The amount of lead introduced into the alloy depends on the degree of machinability to be achieved. Usually, lead can be added in an amount up to several wt.% Without changing the mechanical properties of the alloy at normal temperature. However, at temperatures above the melting point of lead (327 ° C), liquid lead greatly weakens the alloy. Alloys containing lead are difficult to manufacture, on the one hand, because they have a very pronounced tendency to crack and, on the other hand, because they have a two-phase crystalline structure containing an undesirable weakening phase.

The method according to the present invention makes it possible to obtain a machinable product Cu-Ni-Sn-Pb having high mechanical properties, containing up to several wt.% Lead, without cracking it during manufacture. The proportion of lead can vary in the range from 0.1 to 4 wt.%, Preferably from 0.2 to 3 wt.%, Even more preferably from 0.5 to 1.5 wt.%.

After smelting the castings, further production methods can be divided into successive workpieces; for the first billet, two cases can be considered, depending on how the product is made: continuous casting of billets with a small diameter or “static” casting into billets, spray molding, semi-continuous or continuous casting of billets with a large diameter.

The products according to the invention are characterized by high machinability, which exceeds that of Cu-Be alloys. The machinability index of the claimed alloys exceeds 80% relative to brass according to ASTM C36000 and can even reach 90%.

First blank

Alloys obtained by continuous casting of a rod of small diameter, for example 25 mm or less, are subjected to heat-homogenizing treatment or the stage of cold deformation by forging followed by homogenization and recrystallization treatment. The temperature of the heat treatment should be in the range in which the alloy is single-phase. Cooling after heat treatment should occur at a slow enough speed to prevent cracking of the alloy due to internal stresses created due to the temperature difference during cooling, and fast enough to limit the formation of a two-phase structure. If the speed is too slow, a noticeable amount of the second phase may appear. The specified second phase is very fragile and significantly reduces the deformability of the alloy. The critical cooling rate necessary to avoid the formation of too much second phase will depend on the chemical composition of the alloy and will be higher with a higher nickel and tin content.

In addition, transient internal stresses occur in the alloy during cooling. They are related to the temperature difference between the surface and the core of the product. If these stresses exceed the resistance of the alloy, the alloy will crack and is then unusable. Internal stresses due to cooling, the 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 even more relevant for Cu-Ni-Sn-Pb alloys, since above their melting point of 327 ° C, lead significantly weakens the alloy.

In the method according to the present invention, the cooling after heat treatment occurs at a predetermined speed taking into account the chemistry of the alloy and the transverse size or diameter of the product. At the same time, the cooling rate should be low enough to prevent cracking, and high enough to prevent the formation of too much embrittlement phase.

During the production of a large-diameter product, internal stresses, due to the temperature difference, are greater than in a small-sized product and, therefore, the cooling rate should be limited. At the same time, high Ni and Sn contents accelerate the formation of the embrittlement phase and require faster cooling.

Alloys obtained by spray molding, “static” casting into billets or semi-continuous casting are subjected to hot extrusion treatment. This also applies to alloys obtained by continuous casting, if the product is large in diameter. Cooling during extrusion should be slow enough to prevent cracking, and fast enough to limit the formation of an embrittle second phase. Alternatively, if the cooling during extrusion is too slow, the heat-homogenization and recrystallization treatments, which are indicated above for the production of small diameter products by continuous casting, should be followed after extrusion.

After manufacturing the first workpiece, the final machinable product must be obtained directly in one or more cold deformation operations, for example by rolling, wire drawing, stretch molding, or any other cold deformation method, or obtained from one or more subsequent workpieces.

Subsequent blanks

From the first preform, subsequent preforms were obtained in one or several cold deformation operations, followed by recrystallization during heating by treatment. The processing temperature for recrystallization should be in the range in which the alloy is single phase. Cooling after heat treatment should occur at a slow enough rate to prevent cracking, but always fast enough to limit the formation of a two-phase structure. Due to the manufacture of subsequent preforms, the size of the product is reduced. The final product is obtained from the last preform in one or more cold deformation operations.

The mechanical properties of the resulting alloy can then be improved by heat treatment, including spinodal decomposition. Such processing can be carried out before final machining or after it.

The following will provide examples of methods and machinable products in accordance with the present invention. In the following examples, cooling temperatures refer to the core of the product.

Example 1

The chemical composition of the alloy in this example is presented in table 1.

Table 1 Component Part (mass) Cu rest Ni 7.5% Sn 5% Pb one% Mn 0.1-1% other <0.5%

Manganese is introduced into the composition as a deoxidizing agent. However, it can be used instead of other elements or additives to prevent oxidation of the alloy.

This alloy can be cast in accordance with various of the above methods. In this example, the alloy is obtained by continuous casting of a billet with a diameter of 180 mm.

First blank

Extruded preforms, for example, with a diameter of 18 mm. At the exit of the extrusion head, the alloy is cooled by a stream of compressed air, providing 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 brittle second phase. Water jet cooling can also be used to achieve cooling rates of 300 to 1000 ° C / min without cracking the material. Other means may also be used to achieve a suitable cooling rate. If the cooling at the exit of the extrusion die is not fast enough, a too large fraction of the second phase may form, and the alloy must be subjected to homogenization treatment at the same cooling rates and at a temperature in the range in which the alloy is single-phase, i.e. for the composition of table 1 at temperatures from 690 to 920 ° C.

Second workpiece

The material of the first billet with a diameter of 18 mm is rolled to a diameter of 13 mm, then annealed in a continuous furnace or a furnace with a removable arch. For the alloy with the chemical composition of example 1, the annealing temperature should be in the range from 690 to 920 ° C. To limit the formation of the second phase in this composition and for a diameter of 13 mm, a cooling rate of about 10 ° C / min is sufficient. In addition, the possibility of preventing cracking and limiting the formation of an embrittling second phase provides cooling with a water stream at a speed of 300 to 3000 ° C / min.

Fine finishing

The material of the second workpiece is drawn into the wire by drawing or formed with a hood up to a diameter of 8 mm to obtain a machinable product. Finally, spinodal degradation treatment is performed on a machinable product or machinable parts to obtain optimum mechanical properties.

Example 2

The chemical composition of the alloy in this example is presented in table 2.

table 2 Component Part (mass) Cu rest Ni 9% Sn 6% Pb one% Mn 0.1-1% other <0.5%

In this example, the alloy is obtained by continuous casting of rods with a diameter of 18 mm.

First blank

The rods are subjected to homogenization treatment in a continuous furnace at a temperature of from 700 to 920 ° C, corresponding to the single-phase range for the chemical composition of Example 2. The cooling rate from 100 to 1000 ° C / min allows preventing cracking and limiting the proportion of embrittling second phase. Such cooling rates can be achieved, for example, using compressed air, a water stream or a gas-water cooler.

Second workpiece

The material of the first workpiece with a diameter of 18 mm is rolled, drawn into a wire by drawing or formed with a hood to a diameter of 13 mm, then annealed in a continuous furnace at a temperature in the range from 700 to 920 ° C. With a diameter of 13 mm and a chemical composition shown in Table 2, the cooling rate from 100 to 3000 ° C / min provides the possibility of limiting the formation of the second phase while avoiding cracking.

Third workpiece

The material of the second workpiece with a diameter of 13 mm is rolled, drawn into a wire by drawing or molded with a hood to a diameter of 10 mm, then annealed in a continuous furnace or annealing furnace at a temperature of from 700 to 920 ° C. With a diameter of 10 mm and a chemical composition shown in Table 2, the cooling rate from 100 to 15000 ° C / min provides the possibility of limiting the formation of the second phase without cracking.

Fourth blank

The material of the third workpiece with a diameter of 10 mm is rolled, drawn into a wire or formed with a hood to a diameter of 7 mm, then annealed in a continuous furnace or annealing furnace at temperatures from 700 to 920 ° C. With a diameter of 7 mm and the chemical composition shown in Table 2, the cooling rate from 100 to 20,000 ° C / min provides the possibility of limiting the formation of an embrittle second phase without cracking.

Fifth workpiece

The material of the fourth billet with a diameter of 7 mm is rolled, drawn into a wire by drawing or formed with a hood to a diameter of 5 mm, then annealed in a continuous furnace or annealing furnace at temperatures from 700 to 920 ° C. With a diameter of 5 mm and a chemical composition shown in Table 2, the cooling rate from 100 to 30,000 ° C / min provides the possibility of limiting the formation of an embrittle second phase without cracking. A cooling rate of the order of 15,000 ° C./min can be achieved by quenching in appropriate fluids.

Sixth blank

The material of the fifth workpiece with a diameter of 5 mm is rolled, drawn into a wire by drawing or formed with a hood to a diameter of 3 mm, annealed in a continuous furnace or annealing furnace at a temperature of 700 to 920 ° C, then cooled at a cooling rate of 100 to 40,000 ° C / min

Seventh blank

The material of the sixth billet with a diameter of 3 mm is rolled, drawn into a wire by drawing or formed with a hood to a diameter of 2 mm, annealed in a continuous furnace or annealing furnace at a temperature of 700 to 920 ° C, then cooled at a cooling rate of 100 to 40,000 ° C / min

Eighth blank

The material of the seventh preform with a diameter of 2 mm is rolled, drawn into a wire or formed with a hood to a diameter of 1.60 mm, annealed in a continuous furnace or annealing furnace at a temperature of from 700 to 920 ° C and then cooled at a cooling rate of from 100 to 50,000 ° C / min

Fine finishing

The material of the eighth workpiece is rolled, drawn into a wire, or formed with a hood to a diameter of 1 mm to obtain a machinable product. Finally, spinodal decay processing of the machinable product or machinable parts is performed to obtain optimum mechanical properties.

The ASTM Mechanical Testability Test Method provides a method for determining the processability with respect to CuZn39Pb3 or C36000 brass. The machinability index of the alloy in accordance with this aspect of the invention is 80% higher.

Example 3

The chemical composition of the alloy in this example is the same as in the second example, presented in table 2. In this example, the alloy is obtained by continuous casting with a diameter of 25 mm

First blank

A casting from a bar with a diameter of 25 mm is forged to a diameter of 16 mm. Forging allows the material to deform with a significant degree of compression without prior heat-homogenization treatment. When using this method at this stage, a high content of the remaining embrittling second phase may be allowed. The volume fraction of the second phase can be about 50%.

After forging, a bar with a diameter of 16 mm is subjected to homogenization and recrystallization treatment in a continuous furnace. The heat treatment temperature should be between 700 and 920 ° C. Subsequent cooling will occur at a rate of from 100 to 3000 ° C / min. The indicated cooling rates make it possible to prevent cracking and to limit the content of the second phase in the product of the indicated diameter and composition. Such speeds can be obtained using compressed air, a water jet or gas-water coolers.

Fine finishing

The material of the first workpiece is pulled into a wire or formed with a hood to a diameter of 10 mm to obtain a machinable product. Finally, spinodal decay processing of the machinable product or machinable parts is performed to obtain optimum mechanical properties.

Example 4

The chemical composition of the alloy in this example is presented in table 3:

Table 3 Component Part (mass) Cu rest Ni fifteen% Sn 8% Pb one% Mn 0.1-1% other <0.5%

This alloy can be cast in accordance with various of the above methods. In this example, the alloy can be obtained by spray molding of blanks with a diameter of 240 mm.

First blank

Extruded blanks, for example, with a diameter of 20 mm If the roughness of the workpieces is too large, a turning step may be necessary before extrusion. At the exit of the extrusion head, the alloy is cooled by a water jet, providing a cooling rate of 300 to 3000 ° C / min, measured at the core of the alloy. This speed is slow enough to avoid cracking, and fast enough to limit the formation of an embrittle second phase. If the cooling at the exit of the extrusion die is not fast enough, too much of a second phase may form. The alloy can then be subjected to homogenization treatment at the same cooling rates and at a temperature in the range in which the alloy is single-phase, that is, for the composition of table 3 at a temperature of from 780 to 920 ° C.

Second workpiece

The material of the first billet with a diameter of 20 mm is forged to a diameter of 11 mm, then annealed in a continuous furnace. For an alloy with the chemical composition of Example 3, the annealing temperature should be between 780 and 920 ° C. For a diameter of 11 mm and the chemical composition of Table 3, a cooling rate of 300 to 15,000 ° C / min limits the presence of the second phase while preventing cracking. The use of forging provides the ability to achieve significant strain hardening rates even for brittle material. When using this method, the content of the remainder of the embrittling second phase may be higher than in methods of rolling, drawing into wire or forming with a hood. It can reach values of the order of 50 vol.%.

Third workpiece

The material of the second billet with a diameter of 11 mm is forged to a diameter of 6.5 mm, then annealed in a continuous furnace or annealing furnace at a temperature of from 780 to 920 ° C. With a diameter of 6.5 mm, the alloy of Table 3 provides cooling rates from 300 to 20,000 ° C / min without cracking. These speeds make it possible to limit the content of the embrittling second phase.

Fine finishing

The material of the third workpiece is pulled into a wire or molded with a hood to a diameter of 4 mm to obtain a machinable product. Finally, spinodal degradation treatment is performed on a machinable product or machinable parts to obtain optimum mechanical properties.

Cooling test

Samples of the claimed alloy were subjected to a quick cooling test to determine the occurrence of cracking. The chemical composition of the alloy in this test is presented in table 2.

The samples were heat-treated at 800 ° C and then rapidly cooled by immersion in a tempering medium (EXXON XD90) and water.

With each cooling, the cooling rate in ° C / min was measured with a thermocouple in the core of the sample. The presence of cracking was confirmed by a tensile test.

Table 4 diameter / mm speed xd90 tensile test speed in water tensile test four 24000 ○ 63000 H 6 16000 ○ 48500 H 8 12000 ○ 33000 H 10.8 8350 ○ - H 13 6500 ○ / h 23500 H

(○ = good result / H = unsuccessful result).

The test makes it possible to observe that diameters up to about 10 mm can be allowed to cool in the tempering medium. On the other hand, tempering in water always leads to cracking of the sample, and cooling can be allowed to a minimum diameter of 4 mm.

For Cu-Ni-Sn-Pb alloys in the form of small-sized products, cooling rates of more than 24,000 ° C / min can be used. In this case, tempering in water can be effective if the product size is small enough to limit unsteady internal stresses and thus prevent cracking.

Each of the machinable products in Examples 1, 2, 3, and 4 can be made by the methods of Examples 1, 2, 3, and 4, provided that the cooling rates and heat treatment temperatures are adapted to the chemical compositions and sizes. In each of the examples presented, the number of blanks may vary depending on the size of the final product.

Part of the copper in the alloys of the present invention can be replaced by other elements, for example Fe, Zn or Mn, for example, in an amount up to 10%.

Other elements may also be present, such as Nb, Cr, Mg, Zr and Al, in an amount up to several percent. These elements, among others, improve spinodal hardening.

Claims (14)

1. The method of production of a metal product from an alloy containing from 1 to 20 wt.% Nickel, from 1 to 20 wt.% Tin, from 0.2 to 3 wt.% Lead, the rest is essentially copper, including the preparation of a workpiece, its heat treatment by homogenization at the temperature of existence of a single-phase structure, cooling at a rate that prevents cracking and limits the formation of a two-phase structure in the alloy. 2. The method according to claim 1, in which, after heat treatment, cold deformation is carried out by rolling, drawing by wire, molding with a hood or forging. 3. The method according to claim 1, in which the heat treatment is carried out in a continuous furnace. 4. The method according to claim 1, in which the preform is obtained by continuous casting, followed by forging or casting, or by spray molding, or semi-continuous casting followed by extrusion. 5. The method according to claim 1, in which the heat treatment is carried out at a temperature of from 690 to 920 ° C. 6. The method according to claim 1, in which the transverse size of the workpiece during heat treatment is from 1 to 100 mm 7. The method according to claim 1, in which the cooling rate is from 10 to 24000 ° C / min or from 10 to 4000 ° C / min, or from 100 to 1500 ° C / min. 8. The method according to claim 1, in which the cooling rate is from 100 to 1000 ° C / min. 9. The method according to claim 1, in which after heat treatment is carried out drawing into a wire or molding with a hood, or forging, or rolling. 10. The method according to claim 1, including processing with spinodal hardening. 11. The method according to claim 1, in which the alloy contains from 6 to 8 wt.% Nickel, from 4 to 6 wt.% Tin and from 0.5 to 2 wt.% Lead. 12. The method according to claim 1, in which the alloy contains from 8 to 10 wt.% Nickel, from 5 to 7 wt.% Tin and from 0.5 to 2 wt.% Lead. 13. The method according to claim 1, in which the alloy contains from 14 to 16 wt.% Nickel, from 7 to 9 wt.% Tin and from 0.5 to 2 wt.% Lead. 14. The metal product obtained by the method according to claim 1.