CN111575528A

CN111575528A - Method for producing Zr-containing copper alloy material and copper alloy material produced thereby

Info

Publication number: CN111575528A
Application number: CN202010595560.1A
Authority: CN
Inventors: 高维林; 屠晓梅
Original assignee: Hangzhou Tongxin Technology Co ltd
Current assignee: Hangzhou Tongxin Technology Co ltd
Priority date: 2020-06-28
Filing date: 2020-06-28
Publication date: 2020-08-25

Abstract

The invention provides a method for manufacturing Zr-containing copper alloy material, in the continuous or semi-continuous casting process, Zr-containing raw material is directly and continuously added between a chute and a crystallizer, and the relative error of Zr content in the obtained ingot and the finished product is within 10%. The copper alloy material produced by the method contains 0.05-0.35 wt% of Zr, or 0.05-0.35 wt% of Zr, 0.1-0.6 wt% of Cr, and further contains one or more selected from Si, P, Mg and Ti, and the total amount is less than 0.2 wt%, and the balance is Cu and unavoidable impurity. The copper alloy material can be in the shape of a plate strip, a bar line or a section special-shaped material. The copper alloy material has excellent overall characteristics of an electric conductivity of 90% IACS or more and a hardness HV130 or more, or an electric conductivity of 80% IACS or more, a hardness HV150 or more, and a heat resistance temperature of 500 ℃.

Description

Method for producing Zr-containing copper alloy material and copper alloy material produced thereby

Technical Field

The present invention relates to a method for producing a copper alloy material as a conductive material for electric and electronic parts such as high-speed railways, various connectors, and lead frames for integrated circuits, and a copper alloy material produced by the method. The method for producing a copper alloy material can produce a copper alloy material having excellent properties such as electrical conductivity, strength and heat resistance, low production cost and high property uniformity.

Background

In use, the basic copper alloy material of the high-speed railway electrification system and various electric appliances and electronic components requires good electrical conductivity and heat conductivity in order to ensure current flow and inhibit heat generated during electrification; meanwhile, in order to ensure the stability of the current flow, it is necessary to have sufficient contact pressure between the parts, and thus the copper alloy material is required to have sufficiently high strength. In order to ensure the reliability of the contact between the electric and electronic parts, the material is required to have good heat resistance (the property of suppressing the softening of the copper alloy with the temperature increase).

In the field of high conductivity, which is internationally recognized at present, excellent copper alloy materials are a Cu — Zr alloy (commonly known as zirconium copper) and a Cu — Cr — Zr alloy (commonly known as chromium zirconium copper). Cu-Zr alloy, such as C15100, has a conductivity of 90% IACS or more and a hardness of HV120 or so. The Cu-Cr-Zr alloys, such as C18140, C18150, and C18400, have substantially the same properties, an electrical conductivity of about 80% IACS, and a hardness of about HV 150.

The two alloy systems have a common feature of containing about 0.1 wt% of Zr. In the Cu matrix, Zr has an effect of improving strength and heat resistance incomparably with other elements, and has a very small influence (reduction degree) on electric conductivity. However, Zr is very easily oxidized, and during dissolution and casting, Zr causes non-uniformity of composition and characteristics of Zr in the material due to oxidation loss, and at the same time, Zr oxide causes various surface and internal defects of the material.

In order to prevent oxidation of Zr, a vacuum melting casting method is generally adopted. The vacuum melting casting method has two modes, one mode is melting and casting under vacuum (or adding protective gas such as argon after vacuum pumping). Because of the limitation of the vacuum environment space, the alloy material which can be manufactured is very small, the large-scale production cannot be realized, the manufacturing cost is high, the production efficiency is low, and the production and the application of the product are influenced. Another method is to perform continuous casting in the atmosphere after dissolution in a vacuum (or after evacuation by adding a protective gas such as argon) and a general casting method (i.e., molten copper is introduced into a mold through a launder). Although the oxidation degree of Zr is greatly inhibited, the oxidation of Zr is inevitable when molten copper passes through the launder even if protective gas is added during the launder.

At present, the main stream of the industrialized production of Zr-containing copper alloy is non-vacuum dissolution and casting, and the oxidation of Zr is prevented and reduced by adding charcoal into a melting furnace and adding carbon ash into a launder and a crystallizer, and further taking the protection of argon or nitrogen on the basis of adding charcoal and carbon ash into the melting furnace and the launder and the crystallizer. However, the oxidation of Zr cannot be completely prevented, which causes problems of low quality and properties of the ingot (and the final product) and non-uniformity of the properties. If the protective measures are not appropriate, it is sometimes the case that the Zr content in the ingot at the final stage of the semicontinuous casting is zero.

In view of the actual market needs and the above-mentioned problems, a new manufacturing method has been developed in the present invention to obtain a copper alloy material having the same conductivity, higher strength and heat resistance as the existing products, and also having higher uniformity of composition and characteristics.

Disclosure of Invention

The present inventors have found, based on detailed research and experiments, that a copper alloy material containing Zr can be effectively inhibited from being oxidized by a copper alloy solution casting method different from the general one, and an ingot having a uniform Zr content and no surface or internal defects can be obtained. The present invention has been completed based on these findings.

The invention provides a method for producing a copper alloy material, which comprises continuously adding Zr raw material between a launder and a crystallizer without adding Zr raw material in a melting furnace during a solution casting process by using a general copper alloy semi-continuous casting solution casting device for a copper alloy material containing Zr of not more than 0.35 wt%. The added Zr directly flows into the crystallizer along with the molten copper, and the oxidation of the Zr can be effectively inhibited.

The method comprises covering the melting furnace with charcoal during the dissolving process; the inside of the chute and the crystallizer are covered by carbon ash; a weir is further provided at the middle part of the length direction of the chute (the flow direction of molten copper) to prevent coarse charcoal floating on the surface of the molten copper and slag in the raw material from flowing into the crystallizer; introducing protective gases such as argon, nitrogen and the like into the crystallizer.

The ingot obtained by the method has no surface and internal defects, the Zr content in the casting direction (the length direction of the ingot) is uniform, and the relative error of the Zr content in the length direction of the ingot is less than 10 percent in the continuous casting process. The section of the ingot can be rectangular, round and special-shaped. The subsequent manufacturing process and conditions of the cast ingot can be completed according to the commonly used process conditions. Such as hot rolling (or hot forging), face milling (or peeling), cold rolling (or cold forging, drawing), continuous annealing or bell heat treatment, cleaning and straightening, etc.

The present invention provides a copper alloy material produced by the above method, which contains 0.05 to 0.35 wt% of Zr, or 0.05 to 0.35 wt% of Zr, 0.1 to 0.6 wt% of Cr, further contains one or more selected from Si, P, Mg and Ti, and the total amount thereof is 0.2 wt% or less, and the balance being Cu and unavoidable impurity composition. The copper alloy material can be in the shape of a plate strip, a bar line or a section special-shaped material.

The copper alloy material has an electrical conductivity of 90% IACS or more and a hardness of HV130 or more; or the conductivity is above 80% IACS, the hardness is above HV150, and the heat-resisting temperature is above 500 ℃.

The conductivity was measured according to the method defined in JIS H0505. Hardness was measured by vickers hardness. The heat-resistant temperature is measured by cutting a plate-like sample from a material, heating and holding the sample at 200 to 700 ℃ for 30 minutes at an interval of 50 ℃ and measuring the hardness. As the holding temperature is increased by heating, the hardness is decreased. The hardness after heating and the heating temperature were plotted as a curve, and the temperature corresponding to the hardness after the sample was heated and held at 80% of the hardness before heating was defined as the heat-resistant temperature.

The copper alloy material obtained by the manufacturing method of the present invention has excellent comprehensive characteristics which are difficult to obtain according to the existing manufacturing technology and alloy components. In order to meet the anticipated future demand for high strength and high conductivity.

Description of the preferred embodiments

1. Manufacturing method

The copper alloy material is generally cast by a longitudinal semi-continuous casting method because of the need of precise addition element matching, analysis and adjustment. The main equipment consists of melting furnace, chute and crystallizer (casting machine). Cu and the required raw materials containing the additive elements are mixed in weight ratio according to the alloy components in advance, and are added into a melting furnace for dissolution. After the raw material is completely melted, the components are sampled and analyzed, compared with the target value, Cu or other raw materials are added for component adjustment, analysis is carried out again for adjustment, and continuous casting is started after the component analysis value reaches the target value. This process is long, at least 1 hour, and if Zr which is very easily oxidized is contained in the molten copper, it is difficult to prevent the oxidation even if the melting furnace is covered with charcoal and protected with a protective gas.

The melting furnace is tilted so that the molten copper flows into the chute, and flows into the mold through the chute, and continuous casting starts. In the process that molten copper flows into the chute from the melting furnace and enters the crystallizer, the chute and the crystallizer can be covered by carbon ash or protective gas, and Zr oxidation is difficult to avoid. Particularly, when an ingot casting process is relatively long (generally 1 to 2 hours), the Zr content difference in the length direction of the ingot is easily large due to the Zr oxidation loss.

The method of the invention is that Zr is not added in a melting furnace before continuous casting, after the continuous casting is started, a Zr-containing copper coil (commonly called as copper-clad zirconium wire, namely a wire which is formed by wrapping pure copper with Zr or Cu-Zr alloy powder) is directly arranged between a chute and a crystallizer, and continuous addition is carried out according to Zr target components, the cross section area of an ingot, the casting speed and the Zr content in the copper-clad zirconium wire unit length to obtain the continuous addition speed of the copper-clad zirconium wire. The Zr-containing powder is caused to uniformly flow into the crystallizer by the flowing impulse of the molten copper from the launder to the crystallizer. Oxidation of Zr in solution casting is avoided. According to the addition amount of Zr, the adding position of the copper-clad zirconium wire can be properly adjusted, and the position of the copper-clad zirconium wire is closer to or far away from the crystallizer in the chute, so that the Zr is fully dissolved.

The Zr-containing powder in the copper-clad zirconium wire can be pure Zr powder, preferably Cu-Zr intermediate alloy powder with the weight percent of 50-70 percent, and most preferably Cu-Zr intermediate alloy powder with the weight percent of 50 percent. The pure Zr powder has the advantages of small addition amount, which is beneficial to the dispersion and distribution of the powder in a crystallizer, but the melting point of the pure Zr is higher (1855 ℃), and the pure Zr powder is required to be very fine (for example, the average diameter of powder particles is less than 1mm) in order to ensure the full dissolution of the Zr, thus being unfavorable for the addition cost of the alloy. The melting point of 50-70 wt% Cu-Zr intermediate alloy is only about 900-950 deg.C (the copper melting temperature in crystallizer is generally about 1200 deg.C), it is easy to dissolve, and the powder particles can be thicker (for example, the average diameter of the powder particles is less than 3 mm). Meanwhile, in order to further promote sufficient dissolution of Zr, the casting (drawing) speed may be appropriately reduced, or [ copper-clad zirconium wire ] may be heated with a heating gun or the like before inserting molten copper.

Other anti-oxidation measures can be taken by common methods, such as adding charcoal in a dissolving furnace, adding charcoal ash or protective gas in a chute and a crystallizer, and the like. In addition, the present invention is characterized in that a weir is provided at the middle part in the longitudinal direction of the chute (molten copper flow direction), that is, a graphite plate is half-suspended and fixed in the chute, so that molten copper can flow only at the bottom of the chute, and coarse charcoal floating on the surface of molten copper and slag in the raw material are prevented from flowing into the mold, thereby preventing defects such as slag inclusion in the ingot.

2. Quality of ingot

The ingot obtained by the method has uniform Zr distribution and no surface and internal defects. In the casting by the semi-continuous casting method, the Zr content in the bottom, middle and upper parts of the ingot is gradually reduced by the oxidation of Zr, resulting in non-uniformity of characteristics. If the Zr contents of the bottom and upper parts are expressed by { Zr } max and { Zr } min, respectively, and the average value is expressed by { Zr } ave, the following formula (1) is satisfied,

({Zr}max-{Zr}min)/{Zr}ave≤10％……(1)

namely, the maximum deviation of the distribution of the Zr content in the copper alloy is less than 10%.

The above-described copper alloy sheet ingot of the present invention can be produced into various shapes of cross section, such as a square billet for producing a sheet or a strip, a round billet for producing a wire rod, and the like, and can be subsequently produced by the following general copper alloy process. Namely: hot rolling (or hot forging) -cold rolling (or cold forging, drawing) -continuous or bell heat treatment-final cold rolling (drawing) -low temperature stress relief annealing. In addition, although not mentioned above, according to actual needs, milling (peeling) may be performed after hot rolling (hot forging), and optional pickling, grinding or degreasing, stretch bending straightening, and the like may be performed after heat treatment.

3. Alloy composition

Zr (zirconium) is basically not dissolved in the Cu matrix (the solid solubility is very small, and is less than 0.01 wt%), and a monomer or Cu and the Cu are uniformly and finely distributed in the Cu matrix in the form of an intermetallic compound. Since the solid solubility of Zr in the Cu matrix is very small, the influence (reduction) on the conductivity is very small; and the uniform and fine Zr and the intermetallic compound of the Zr and the Cu can prevent dislocation and grain boundary movement and improve the strength and heat resistance of the alloy. When the Zr content is less than 0.05 wt%, the effect of improving the strength and heat resistance of the alloy is not significant; if the content exceeds 0.35 wt%, the resulting alloy may not be completely dissolved in a crystallizer, and if the Zr content is too high, the intermetallic compound of Cu and Zr may grow and the strength may be lowered. Therefore, the Zr content is controlled to be 0.05 to 0.35 wt%, preferably 0.10 to 0.30 wt%.

Cr (chromium) has a precipitation strengthening effect in the Cu matrix, and particularly in the presence of Zr, Zr makes Cr precipitates more uniformly and less dispersed, resulting in higher strength. Meanwhile, the solid solubility of Cr in a Cu matrix is relatively low, and the reduction range of the conductivity of the alloy is small when Cr is added, so that the Cr is one of main addition elements of the high-strength conductive copper alloy. When the Cr content is less than 0.2 wt%, the strengthening effect is insufficient; if the content is 0.6 wt% or more, the strengthening effect tends to be saturated, and the addition of an excessive amount also deteriorates the manufacturability of the alloy. Therefore, the Cr content is between 0.2 and 0.6.

As the other elements, one or more elements selected from Si, P, Mg and Ti may be contained as the case may be. Wherein: si and P can form precipitates with Zr, Cr and the like, so that the strength is further improved; mg and Ti have the functions of refining grains and improving heat resistance. When one or more elements selected from Si, P, Mg and Ti are contained, the content of each element is preferably 0.01 wt% or more in order to sufficiently exhibit the above-described various effects. However, the above-mentioned contents of the various elements are too large, and the conductivity is liable to be lowered. Therefore, the total content of these elements is preferably controlled to 0.2 wt% or less, more preferably 0.15 wt% or less.

4. Characteristics of

The mainstream of the high-conductivity copper alloy materials at present is a Cu-Zr alloy, a Cu-Cr-Zr alloy and the like, and the common problems are that the quality problem caused by Zr oxidation and the strength need to be further improved. Further improvement of the strength by increasing the Zr content is conceivable in the industry. Since the problem of Zr oxidation is not easily solved, the Zr content of both the Cu-Zr alloy and the Cu-Cr-Zr alloy has to be set to 0.1 wt% Zr, and the Zr content is generally 0.05 to 0.1 wt% as a practical result. The Cu-Zr alloy and the Cu-Cr-Zr alloy according to the present invention can contain more Zr, and have higher strength and heat resistance at the same conductivity.

Specifically, the Cu-Zr alloy has an electric conductivity of 90% IACS or more, a hardness of HV130 or more, and a heat resistance temperature of 500 ℃ or more. The Cu-Cr-Zr alloy has an electrical conductivity of 80% IACS or higher, a hardness of HV150 or higher, and a heat resistance temperature of 500 ℃ or higher.

5. Examples of the embodiments

Ingots having the compositions shown in Table 1 were cast by a conventional vertical type semi-continuous casting apparatus and conditions for copper alloys, the effective volume of the melting furnace was 3 tons, and the cross-sectional area of the mold (and ingot) was 400 × 180mm and 180mm²(square billet) the length of the cast ingot formed by drawing casting is 4.5m, the drawing casting speed is 60mm/min, and the drawing casting time is about 75 min.

In the examples, instead of adding Zr or Zr-containing raw material in the melting furnace, a pure copper tape with a thickness of 0.15mm was wrapped with Cu-50% Zr master alloy powder [ copper-clad zirconium wire ] with a diameter of 8mm during the casting process and continuously added at a predetermined rate to the molten copper flowing between the outlet of the chute and the mold. The predetermined speed is obtained by calculating the Zr addition amount required in unit time according to the target Zr content of each alloy, the section area of the cast ingot and the casting speed and according to the Zr content in unit length (copper-clad zirconium wire).

Comparative examples No.21 and No.22 have the same target alloy composition as in examples No.1 and No.3, respectively, and Zr or a Zr-containing raw material was added to a melting furnace by a general melting casting method.

The length of the ingot of the present example and comparative example after cutting the head and the tail was 4 m. Samples were taken at the bottom and upper part of the ingot length (4 m apart) for compositional analysis. When the analysis values of the bottom and top are expressed as { Zr } max and { Zr } min, respectively, and the average value is { Zr } ave, the maximum deviation of the Zr content distribution in the copper alloy is expressed as ({ Zr } max- { Zr } min)/{ Zr } ave.

The ingot was cut off at the end and heated to 950 ℃ for 4 hours, followed by hot rolling. And carrying out water cooling after hot rolling. And removing the oxide film on the surface by milling. Then cold rolling is carried out to the required thickness, and the aging treatment is carried out at 480 ℃ to adjust the aging time so as to lead the hardness to reach the maximum value. The optimum ageing treatment time for the alloy composition is known from prior experiments. The aged material sample was subjected to final cold rolling at a reduction ratio of 30%, and after the cold rolling, low-temperature annealing was performed in a heating furnace at 400 ℃ for 3 minutes. The middle is subjected to the procedures of acid washing, degreasing, stretch bending, edge shearing and the like as required. The plate thicknesses of the final samples were set to 0.50 mm. The obtained plate was sampled from both ends in the longitudinal direction (corresponding to the bottom and upper positions of the ingot, respectively) to evaluate the characteristics.

The characteristics of the obtained sample were evaluated as follows. Namely: electrical conductivity, vickers hardness, heat resistance temperature.

[ conductivity ]: measured according to the method prescribed in JIS H0505.

[ hardness ]: the Vickers hardness was measured at a load of 500 g.

[ temperature resistance ]: the plate-like test piece was heated and held at 200 to 700 ℃ for 30 minutes at an interval of 50 ℃ and then the hardness was measured. As the holding temperature is increased by heating, the hardness is decreased. The hardness after the heat treatment was plotted against the heating temperature, and the temperature corresponding to the hardness after the sample was heated and held at 80% of the hardness before the heating was defined as the heat-resistant temperature.

[ Table 1 ]:

as can be seen from Table 1, in all the examples obtained by the casting method and the manufacturing process of the present invention, the maximum relative error of Zr content distribution is 10% or less, the head and tail characteristics are uniform, the conductivity is 90% IACS or more, and the hardness is HV130 or more; or an electric conductivity of 80% IACS or more, a hardness of HV170 or more, and excellent heat resistance at a heat resistant temperature of 500 ℃ or more.

In contrast, comparative examples 21 and 22 are copper alloys having the same target alloy composition as that of examples 1 and 3, respectively, and also being the most representative of the present Cu — Zr alloy and Cu — Cr — Zr alloy composition, and produced by a conventional casting method and process. The maximum relative error of Zr content distribution is more than 15%, so that the difference of head and tail characteristics is large, the electric conductivity is difficult to meet more than 90% IACS, and the hardness is more than HV 130; or the conductivity of the alloy is 80% IACS or more, the hardness is HV170 or more, and the heat resistance temperature is 500 ℃ or more.

Compared with the traditional manufacturing method, the manufacturing method of the Zr-containing copper alloy can not only keep the characteristic uniformity of the copper alloy by preventing and avoiding the oxidation of Zr; meanwhile, the strength of the alloy can be further improved by increasing the Zr content in the copper alloy.

Claims

1. A method for manufacturing a Zr-containing copper alloy material is characterized in that the method utilizes the existing copper alloy continuous or semi-continuous casting dissolution casting equipment to the copper alloy material containing not more than 0.35 wt% of Zr, Zr raw material is continuously added between a launder and a crystallizer in the dissolution casting process, the added Zr directly flows into the crystallizer along with molten copper, and an ingot with the Zr content within 10% relative error is obtained after crystallization.

2. The method for producing a Zr-containing copper alloy material according to claim 1, wherein the melting furnace is covered with charcoal, the chute and the mold are covered with charcoal ash, a weir is provided at a middle portion in the length direction of the chute to prevent coarse charcoal floating on the surface of the molten copper and dross in the raw material from flowing into the mold, and an inert shielding gas is introduced into the mold during the melting casting.

3. The method for producing a Zr-containing copper alloy material according to claim 1, wherein the weir is formed by fixing a graphite plate in a half-suspended manner in a chute so that the molten copper flows only at the bottom of the chute, and coarse charcoal floating on the surface of the molten copper and dross in the raw material are prevented from flowing into the mold, thereby preventing the occurrence of slag inclusion in the ingot.

4. The method for producing the Zr-containing copper alloy material according to claim 1, 2 or 3, wherein, when Zr is continuously added, Zr is added in the form of a copper-clad zirconium wire composed of pure Zr powder having an average particle size of less than 1mm coated with copper or Cu-Zr master alloy powder having an average particle size of less than 3mm in an amount of 50 to 70 wt%.

5. The method for producing the Zr-containing copper alloy material according to claim 4, wherein the Zr-containing alloy material is added in the form of a copper-clad zirconium wire comprising Cu-Zr master alloy powder in an amount of 50 wt% wrapped with copper.

6. The method of producing the Zr-containing copper alloy material according to claim 4 or 5, wherein the copper-clad zirconium wire is preheated and then inserted into the molten copper.

7. The method for producing the Zr containing copper alloy material according to claim 1, 2 or 3, wherein the Zr containing copper alloy material contains 0.05 to 0.35 wt% of Zr, or 0.05 to 0.35 wt% of Zr, 0.1 to 0.6 wt% of Cr, and the balance of Cu and unavoidable impurities, and the shape of the Zr containing copper alloy material is a plate strip, a bar wire or a profile.

8. The method for producing the Zr containing copper alloy material according to claim 7, wherein the Zr containing copper alloy material contains 0.1 to 0.3 wt% of Zr, or 0.1 to 0.3 wt% of Zr, 0.2 to 0.6 wt% of Cr, and the balance being Cu and unavoidable impurity composition.

9. The method for producing the Zr containing copper alloy material according to claim 7 or 8, wherein the Zr containing copper alloy material further contains one or more elements selected from the group consisting of Si, P, Mg and Ti in a total amount of 0.2 wt% or less.

10. The Zr-containing copper alloy material produced by the production method according to claim 1 or 2, which has an electrical conductivity of 90% IACS or more and a hardness of HV130 or more; or the conductivity is above 80% IACS, the hardness is above HV150, and the heat-resisting temperature is above 500 ℃.