CN116334441A - A kind of free-cutting high-conductivity oxygen-free lead-copper alloy and preparation method thereof - Google Patents

Abstract

The free-cutting high-conductivity oxygen-free lead-copper alloy comprises the following components in percentage by mass: 0.003% -0.012%, pb:0.8 to 1.2 percent, O:1 to 10ppm, the balance of Cu and unavoidable impurities, and controlling the content of impurity elements Fe and Si to be less than or equal to 0.005 percent, al, sb, mn, ni to be less than or equal to 0.02 percent and the total content of the impurity elements to be less than or equal to 0.05 percent. The preparation adopts a bottom blowing refining technology, charcoal coverage, annealing times reduction, cold working pass deformation increase and other methods, and the process comprises the following steps: smelting, casting, extruding, pickling, cold drawing processing, annealing, straightening and sawing. The invention has simple and reasonable process, the oxygen content of the prepared oxygen-free lead-copper alloy is lower than 10ppm, the lead particles are tiny and dispersed, the grain size is moderate, the machinability is good and can reach more than 85%, and the oxygen-free lead-copper alloy can be used for precision machining, and has better conductivity (more than 90% IACS) and hydrogen embrittlement resistance (grade 1-3) compared with the traditional lead-copper alloy.

Description

A kind of free-cutting high-conductivity oxygen-free lead-copper alloy and preparation method thereof

technical field

The invention belongs to the technical field of copper alloys, and relates to a free-cutting high-conductivity oxygen-free lead-copper alloy and a preparation method thereof.

Background technique

High-conductivity copper alloys have been widely used in optoelectronic devices, microwave technology, aerospace, national defense and military industry, electronics industry and connectors in home appliance industry and other industries. Most high-conductivity copper alloy materials have poor cutting performance, and the cutting performance directly affects the machining accuracy of the material.

Lead element is the most commonly used alloying element to improve cutting performance, which can significantly improve the cutting performance of materials, and its cutting performance improvement effect is significantly better than other easy-cutting elements such as sulfur, selenium, tellurium, etc. Low levels of lead (less than 4 wt.%) in alloys are exempted.

However, lead-copper alloys often have no standard requirements for oxygen content. Oxygen-containing lead-copper alloys are prone to induce hydrogen embrittlement in high-temperature reducing atmospheres and lead to cracks, which limits the high-temperature application of high-conductivity lead-copper alloys; More oxidation products are produced, reducing thermal and electrical conductivity. In addition, the aggregation and growth of lead particles in lead-copper alloys during thermal processing and heat treatment will cause a decrease in cutting performance.

In view of the lack of cutting performance of high-conductivity copper alloy materials and the hydrogen embrittlement resistance of lead-copper alloys, it is necessary to improve the original lead-copper alloy and develop a low-cost, easy-to-cut, high-conductivity non-metallic alloy that is easy to realize industrialization. Oxygen lead copper alloy.

Contents of the invention

The first technical problem to be solved by the present invention is to provide an oxygen-free lead-copper alloy with high electrical conductivity which is easy to cut and has good cutting performance and resistance to hydrogen embrittlement.

The second technical problem to be solved by the present invention is to provide a method for preparing a free-cutting high-conductivity oxygen-free lead-copper alloy, which has simple process and low cost, and can realize industrial production.

The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a kind of free-cutting high-conductivity oxygen-free lead-copper alloy, characterized in that: the mass percentage of the lead-copper alloy is composed of:

P 0.003%～0.012%;

Pb 0.8%～1.2%;

O 1～10ppm;

Unavoidable impurities ≤ 0.05%, control impurity element content Fe, Si ≤ 0.005%, Al, Sb, Mn, Ni ≤ 0.02%;

The balance is Cu.

Further, the oxygen content of the lead-copper alloy is lower than 10 ppm, the grain size is 25-50 μm, and the number of lead particles per square millimeter is 10000-20000.

Further, the hydrogen embrittlement grade of the lead-copper alloy is grade 1-3.

Further, the cutting performance of the lead-copper alloy reaches above 85% (with HPb63-3 as the standard), and the electrical conductivity reaches above 90% IACS.

Finally, the tensile strength of the lead-copper alloy in a hard state is 270-320 MPa, the yield strength is 210-260 MPa, the elongation is 8-12%, and the Vickers hardness is 100-130 HV.

The technical scheme adopted by the present invention to solve the above-mentioned second technical problem is: a kind of preparation method of free-cutting high-conductivity oxygen-free lead-copper alloy, it is characterized in that comprising the following steps:

1) Casting

According to the above mass percentage, the P element is added as a phosphor copper master alloy; use a preheating furnace to heat the high-purity cathode copper and lead block to above 100°C to dry the water, and put the preheated cathode copper and lead block into Melting in a power frequency induction furnace, blowing inert gas into the bottom of the induction furnace through a ventilating device, heating up and melting under the protection of the covering agent, and keeping it at rest after the melting temperature reaches 1200-1300°C, the standing time is not less than 30min; The copper liquid is transferred into the holding furnace, and the phosphor-bronze intermediate alloy is added to the holding furnace when the copper liquid is transferred. The bottom of the holding furnace is equipped with a ventilation device, and an inert gas is blown through the ventilation device, so that the oxygen content of the copper liquid in the furnace is less than 10ppm , the hydrogen is less than 5ppm, the temperature of the holding furnace is controlled at 1100-1200°C, the purified copper liquid is poured into the crystallizer and cooled to form a billet, the casting speed is 20-60mm/min, and the temperature of the ingot out of the mold is 600 ~950℃;

2) Squeeze

Put the cast slab obtained in step 1) into an induction furnace, heat it to 600-900°C, keep it warm for 5-30 minutes, and then perform extrusion processing with an extrusion ratio of 30-200 and an extrusion speed of 0.5-5mm/s;

3) pickling

Pickling the extruded billet in step 2) to remove surface oxides;

4) Cold drawing and annealing

The pickled billet is subjected to cold drawing processing, and the drawing is carried out in multiple passes. After 2 passes of drawing processing, intermediate annealing and pickling are carried out. Carry out subsequent pass stretching;

5) Straightening and sawing

The cold-processed material is sawed to a specified length, straightened on a straightening machine, and packaged for storage after passing the appearance inspection and physical performance inspection.

Preferably, the covering agent in step 1) is charcoal, and the covering thickness of charcoal is not less than 20cm.

Preferably, the phosphor-bronze master alloy in the step 1) is CuP14, the inert gas blown into the bottom of the smelting furnace and the holding furnace is any one of argon and nitrogen, the gas flow rate is 50-200L/min, and the inert gas The oxygen content in the medium does not exceed 0.03vol.%, and the moisture does not exceed 3.0g/L.

Further, in the pickling process of the step 3), it is necessary to add a pickling corrosion inhibitor that can reduce the precipitation of hydrogen.

Finally, the number of stretching passes in the cold drawing processing in the step 4) is 3-4 times, the stretching processing rate of each pass is controlled at 10-30%, and the total stretching processing rate is 50-90%.

Compared with the prior art, the present invention has the advantages of: based on the copper-lead alloy, adding phosphorus element as a deoxidizer, combined with bottom blowing refining technology, charcoal covering and other methods to regulate the oxygen content, so that the oxygen content is lower than 10ppm , to meet the standard of oxygen-free copper; the addition of trace phosphorus in copper alloy can improve the fluidity of the melt, improve the welding performance, corrosion resistance and softening resistance of copper alloy; the role of lead element is to improve the cutting performance of the alloy; Reduce the times of annealing, increase the amount of deformation in cold working passes, make the lead particles fine and dispersed, control the grain size, improve the cutting performance, electrical conductivity and cold heading performance of the alloy, and adjust the temperature and strain rate of hot working to obtain An oxygen-free lead-copper alloy with low cost and simple industrialization, which is easy to cut and highly conductive. The process of the present invention is simple and reasonable, and the oxygen content of the prepared oxygen-free lead-copper alloy is lower than 10ppm, reaching the oxygen-free copper TU2 level; and the lead particles in the oxygen-free lead-copper alloy are fine and dispersed, the grain size is moderate, and has good machinability, It can reach more than 85% (with HPb63-3 as the standard), and can be used for precision machining. Compared with traditional lead-copper alloys, it has better electrical conductivity (above 90% IACS) and hydrogen embrittlement resistance (grade 1-3 ).

Description of drawings

Fig. 1 is the metallographic structure photograph of embodiment 1 provided by the invention;

Fig. 2 is the metallographic structure photo of embodiment 2 provided by the present invention;

Fig. 3 is the lead particle distribution metallographic photograph of embodiment 1 provided by the invention;

Fig. 4 is the metallographic photograph of the lead particle distribution of Example 2 provided by the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

In the following examples and comparative examples, when adding raw materials, all add by weight fraction. The specific ingredients are shown in Table 1.

The composition of table 1 embodiment, comparative example

A preparation method of free-cutting high-conductivity oxygen-free lead-copper alloy, comprising the following steps:

(1) Casting

According to the above mass percentage, the P element is added as a phosphor copper master alloy; use a preheating furnace to heat the high-purity cathode copper and lead block to above 100°C to dry the water, and put the preheated cathode copper and lead block into Melt in a power frequency induction furnace, blow inert gas into the bottom of the induction furnace through a ventilation device, heat up and melt under the protection of charcoal covering, and the thickness of charcoal covering is not less than 20cm. After the melting temperature reaches 1200-1300°C, keep it warm and let it stand for no less than 30 minutes. Transfer the melted copper liquid into the holding furnace, and add phosphor-bronze intermediate alloy into the holding furnace when transferring the copper liquid. The bottom of the holding furnace is equipped with a ventilation device, and high-purity argon gas is blown in through the ventilation device, and the gas flow rate is 50~ 200L/min, further purify the copper liquid to remove impurities, so that the oxygen content of the copper liquid in the furnace is less than 10ppm, and the hydrogen content is less than 5ppm. The temperature of the holding furnace is controlled at 1100-1200°C. Billet, casting speed is 20-60mm/min, ingot exiting mold temperature is 600-950℃.

(2) extrusion

After passing the component and surface quality inspection of the billet, put it into the induction furnace, heat it to 600-900°C, keep it warm for 5-30 minutes, and then carry out extrusion processing. The extrusion ratio is 30-200, and the extrusion speed is 0.5-5mm/ s.

See Tables 2 and 3 for specific process parameters of casting and extrusion.

Table 2 Embodiment of the present invention, the melting and casting process parameter control of comparative example

Table 3 embodiment, the extrusion process parameter control of comparative example

(3) pickling

Pickling the above extruded billets to remove surface oxides. During the pickling process, a pickling corrosion inhibitor needs to be added to reduce the precipitation of hydrogen, inhibit the hydrogen absorption of the alloy, and improve the anti-hydrogen embrittlement ability of the material.

(4) Cold drawing and annealing

The above-mentioned pickled bar blank is subjected to cold drawing processing, and the stretching is carried out in multiple passes, the number of stretching passes is 3 to 4 times, and the drawing processing rate of each pass is controlled at 10 to 30%, and the total drawing processing rate 50-90%; intermediate annealing and pickling are carried out after 2 passes of stretching, the annealing temperature is 300-500°C, the time is 2-5h, the grain size of the alloy after annealing is 25-50μm, and then the subsequent Pass stretching.

The specific process parameters of cold drawing and annealing are shown in Table 4.

The cold drawing process of table 4 embodiment, comparative example and annealing process parameter control

(5) straightening and sawing

After the cold drawing process, the material is sawed to a specified length, straightened on a straightening machine, and after passing the appearance inspection and physical performance inspection, it is packaged and put into storage.

Comparative example 1 is a commercially available lead-copper alloy C18700.

The difference between Comparative Example 2 and Example 1 is that the content of impurity elements is too high.

The difference between Comparative Example 3 and Example 1 is that the annealing temperature is too low.

The difference between Comparative Example 4 and Example 1 is that the annealing temperature is too high.

The difference between Comparative Example 5 and Example 1 is that no bottom blowing refining was carried out.

The difference between Comparative Example 6 and Example 1 is that the gas flow rate of the bottom blowing refining is too low.

The difference between Comparative Example 7 and Example 1 is that the gas flow rate of the bottom blowing refining is too high.

The difference between Comparative Example 8 and Example 1 is that the casting speed is too low.

The difference between Comparative Example 9 and Example 1 is that the casting speed is too high.

The difference between Comparative Example 10 and Example 1 is that the extrusion speed is too high.

Carry out mechanical property and/or microstructure detection to the lead-copper alloy prepared by embodiment and comparative example, concrete detection index and detection standard are as follows:

1) Hardness HV5: GB/T 4340.1-2009 Vickers hardness test for metallic materials Part 1: Test method.

2) Tensile strength, yield strength, elongation: GB/T 228.1-2010 Tensile test of metal materials Part 1: Tensile test method at room temperature.

3) Metallographic microscopic test: YS/T 449-2002 Microstructural examination method of copper and copper alloy casting and processed products.

4) Cutting index: Evaluate according to the cutting performance test method in Appendix B of YS-T 647-2007 "Copper Zinc Bismuth Tellurium Alloy Rod", and set the cutting index of C36000 (HPb63-3) to 100%.

5) Conductivity: GB/T 351-2019 Measurement method for resistivity of metal materials.

6) Oxygen content/hydrogen embrittlement level: YS/T 335-2009 metallographic examination method for oxygen content of oxygen-free copper, GB/T 5121.8-2008 chemical analysis method for copper and copper alloy Part 8: Determination of oxygen content.

The performance of the embodiment of the present invention, comparative example of table 5

The determination of the innovation point of the present invention and process data is further described below:

The invention is based on copper-lead alloy, adding phosphorus element as a deoxidizer, combined with bottom blowing refining and charcoal covering to control the oxygen content. In addition, the addition of trace amounts of phosphorus in the copper alloy can improve the fluidity of the melt, improve the welding performance, corrosion resistance and softening resistance of the copper alloy. The role of the lead element in the present invention is to improve the cutting performance of the alloy, but the lead element will significantly reduce the high-temperature processing performance of the copper alloy, and the added amount is too low to achieve better cutting performance, so the lead added amount needs to be controlled at 0.8%. ~1.2% range.

Among the impurity elements that may exist in the raw materials and introduced in the processing process, Fe and Si elements have a greater impact on the electrical conductivity of the alloy, and their content should be controlled to ≤0.005%; Al, Sb, Mn, and Ni elements have a general impact on the alloy electrical conductivity, control The content is ≤0.02%, and the total amount of impurity elements is controlled to be ≤0.05%.

In the above melting and casting process, the temperature of the melting furnace is 1200-1300°C, and the temperature of the holding furnace is 1100-1200°C. If the temperature is too high, it will lead to waste of energy, hydrogen absorption, coarse grains and burning loss of phosphorus; if the temperature is too low, the It is not conducive to the melting of alloying elements and the discharge of gas and inclusions, and increases the tendency to form segregation, cold shut, and under-casting. It will also cause the castings to fail to receive reasonable shrinkage due to insufficient riser heat.

In the above-mentioned melting and casting process, the casting speed is 20-50mm/min. If the casting speed is too low, the product production cycle will be increased and the production efficiency will be reduced, and because the alloy liquid cavity is shallow, it is easy to cause defects such as cold shut and inclusions in the ingot; If the casting speed is too high, it will lead to defects such as cracks and pores in the ingot, and even lead to insufficient cooling time of the copper liquid, resulting in copper leakage.

In the above melting and casting process, the thickness of the charcoal covering should not be less than 20cm, otherwise it will reduce the isolation effect between the copper liquid and the air and cause air inhalation.

During the above bottom blowing refining process, an inert gas is blown into the bottom of the smelting furnace and the holding furnace through a ventilation device. The inert gas is any one of argon and nitrogen, and the gas flow rate is 50-200 L/min. The oxygen content in the inert gas must not exceed 0.03vol.%, and the water content must not exceed 3.0g/L, otherwise the refining effect will be significantly reduced. If the gas flow rate is too small, the number of bubbles will be too small to achieve a good degassing and refining effect; if the gas flow rate is too large, the volume of the bubbles will increase and the number will decrease, reducing the effect of degassing and refining, and even form a through flow, causing The copper liquid is splashed or the slag covered on the surface is involved in the interior of the copper liquid to cause pollution.

In the above-mentioned extrusion process, the heating temperature is 600-900°C. If it is lower than 600°C, the deformation resistance of the metal will be greater, and the extrusion force will also increase relatively, making it difficult to extrude; if it is too high, the tendency of copper alloy thermal cracking will increase. Even overheating and overburning will cause the grains of the metal to grow excessively, resulting in coarse grains of the extruded product and low metal strength. The extrusion ratio is 30-200. If it is too low, it will lead to insufficient extrusion deformation and reduce the mechanical properties of the extruded product; if it is too high, it will cause the required extrusion force to be too high, making extrusion difficult and easy. cracking. Extrusion speed is 1-10mm/s, if the extrusion speed is too low, the extrusion time will increase. The extrusion process is accompanied by the temperature loss of the ingot, and the extrusion force will increase greatly when the extrusion reaches the end stage, which will affect the extrusion efficiency and Quality; Excessive extrusion speed will lead to the accumulation of extrusion deformation heat, which will cause temperature rise and increase the thermal cracking tendency of the material.

In the above pickling process, it is necessary to add a pickling corrosion inhibitor to reduce the precipitation of hydrogen, inhibit the hydrogen absorption of the alloy, and improve the hydrogen embrittlement resistance of the material.

In the above-mentioned cold drawing process, the processing rate of each pass is 10-30%. If the processing rate of a single pass is too large, the chuck may break, and if the processing rate of a single pass is too small, the number of drawing passes will be increased and the production efficiency will be reduced. The total processing rate is 50-90%, and the processing rate of cold-drawn products can be set according to requirements, so as to obtain products in different states such as 1/4 hard state, semi-hard state or hard state.

In the above annealing process, the annealing temperature is 300-500°C, the time is 2-5 hours, and annealing is only performed once after stretching. If the annealing temperature is too low and the time is too short, the residual stress cannot be completely eliminated; if the temperature is too high and the time is too long, it will cause the lead particles to aggregate and grow, and the grains will grow, causing the cutting performance and mechanical properties to decrease; It will cause lead particles to aggregate and grow. Control the grain size in the range of 25-50 μm. If the grain size is too small, the electrical conductivity of the material will decrease and it will be easy to crack during cold heading. If the grain size is too large, the mechanical properties of the material will decrease.

The above embodiments are only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above-mentioned content of the invention still belong to the scope of the present invention. protected range.

Claims (10)

1. A free-cutting high-conductivity oxygen-free lead copper alloy is characterized in that: the lead-copper alloy comprises the following components in percentage by mass:

P 0.003％～0.012％；

Pb 0.8％～1.2％；

O 1～10ppm；

unavoidable impurities are less than or equal to 0.05 percent, and the content of impurity elements Fe and Si is controlled to be less than or equal to 0.005 percent, and Al, sb, mn, ni is controlled to be less than or equal to 0.02 percent;

the balance being Cu.

2. The free-cutting, highly conductive, oxygen-free lead copper alloy of claim 1, wherein: the oxygen content of the lead-copper alloy is lower than 10ppm, the grain size is 25-50 mu m, and the lead particle number per square millimeter is 10000-20000.

3. The free-cutting, highly conductive, oxygen-free lead copper alloy of claim 1, wherein: the hydrogen embrittlement grade of the lead-copper alloy is 1-3.

4. The free-cutting, highly conductive, oxygen-free lead copper alloy of claim 1, wherein: the cutting performance of the lead-copper alloy reaches more than 85 percent (taking HPb63-3 as a standard), and the conductivity reaches more than 90 percent IACS.

5. The free-cutting, high-conductivity, oxygen-free lead copper alloy according to any one of claims 1 to 4, wherein: the hard lead-copper alloy has tensile strength of 270-320 MPa, yield strength of 210-260 MPa, elongation of 8-12% and Vickers hardness of 100-130 HV.

6. A method for preparing the free-cutting high-conductivity oxygen-free lead copper alloy according to any one of claims 1 to 5, which is characterized by comprising the following steps:

1) Casting

Proportioning according to the mass percentage, wherein the P element is added by using a phosphorus-copper intermediate alloy; heating high-purity cathode copper and lead to above 100 ℃ by using a preheating furnace, drying water, putting the preheated cathode copper and lead into a power frequency induction furnace for melting, blowing inert gas into the bottom of the induction furnace through a ventilation device, heating up for melting under the covering protection of a covering agent, keeping the temperature and standing for not less than 30min after the melting temperature reaches 1200-1300 ℃; transferring molten copper into a heat preservation furnace, adding phosphorus-copper intermediate alloy into the heat preservation furnace during transferring copper, arranging a ventilation device at the bottom of the heat preservation furnace, blowing inert gas into the furnace through the ventilation device to ensure that the oxygen content of copper in the furnace is less than 10ppm and the hydrogen content is less than 5ppm, controlling the temperature of the heat preservation furnace to be 1100-1200 ℃, pouring purified copper into a crystallizer, cooling and forming into a casting blank, wherein the casting speed is 20-60 mm/min, and the temperature of the casting blank out of the crystallizer is 600-950 ℃;

2) Extrusion

Placing the casting blank obtained in the step 1) into an induction furnace, heating to 600-900 ℃, preserving heat for 5-30 min, and then performing extrusion processing, wherein the extrusion ratio is 30-200, and the extrusion speed is 0.5-5 mm/s;

3) Acid washing

Pickling the rod blank extruded in the step 2) to remove surface oxides;

4) Cold drawing and annealing

Cold drawing the pickled bar blank, stretching the bar blank for multiple times, carrying out intermediate annealing and pickling after 2 times of stretching, wherein the annealing temperature is 300-500 ℃ and the time is 2-5 hours, and then stretching the bar blank for the subsequent times;

5) Straightening sawing

Sawing the cold-processed material to a specified length, straightening the material on a straightening machine, and packaging and warehousing after appearance inspection and physical property inspection are qualified.

7. The method of manufacturing according to claim 6, wherein: the covering agent in the step 1) is charcoal, and the covering thickness of the charcoal is not less than 20cm.

8. The method of manufacturing according to claim 6, wherein: the phosphorus-copper intermediate alloy in the step 1) is CuP14, inert gas blown into the smelting furnace and the heat preservation furnace bottom is any one of argon and nitrogen, the gas flow is 50-200L/min, the oxygen content in the inert gas is not more than 0.03vol.%, and the water content is not more than 3.0g/L.

9. The method of manufacturing according to claim 6, wherein: and 3) adding an acid pickling corrosion inhibitor capable of reducing the precipitation of hydrogen in the acid pickling process of the step 3).

10. The method of manufacturing according to claim 6, wherein: the number of drawing channels of the cold drawing in the step 4) is 3-4, the drawing processing rate of each channel is controlled to be 10-30%, and the total drawing processing rate is 50-90%.

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