CN114540662A

CN114540662A - Brass alloy and preparation method thereof

Info

Publication number: CN114540662A
Application number: CN202210162683.5A
Authority: CN
Inventors: 王东; 舒孟洋; 欧阳好
Original assignee: Ningbo Jintian Copper Group Co Ltd
Current assignee: Ningbo Jintian Copper Group Co Ltd
Priority date: 2022-02-22
Filing date: 2022-02-22
Publication date: 2022-05-27
Anticipated expiration: 2042-02-22
Also published as: CN114540662B

Abstract

The invention discloses a brass alloy which is characterized by comprising the following components in percentage by mass: 59-63 wt%, Si: 0.2 to 0.8 wt%, Sn: 0.4 to 1.0 wt%, Pb: 0.05 to 0.15 wt%, Al: 0.1 to 0.2 wt%, As: 0.02-0.15 wt%, and the balance of Zn and inevitable impurities. The alloy of the invention meets the environmental protection requirement, and simultaneously utilizes the proportion control of Cu and Si elements and the addition of Sn and As elements to obtain 10-25% of beta phase, can reach the standard of dezincification corrosion resistance test below 100 micrometers, greatly reduces the failure of products in the valve and bathroom industry caused by dezincification, and simultaneously solves the problem that the conventional dezincification-resistant alpha single-phase brass is difficult to be subjected to hot forging processing.

Description

Brass alloy and preparation method thereof

Technical Field

The invention belongs to the technical field of copper alloys, and particularly relates to a brass alloy and a preparation method thereof.

Background

The brass alloy is the most widely used lead brass, because lead is basically not dissolved in the copper-zinc alloy, and is usually distributed on a grain boundary in a free particle point manner, so that the cutting chips are easy to break when the material is machined, and the brass has a lubricating effect, so that the lead-containing brass has good cutting performance. However, with the development of society, people find that the materials have great influence on human health in the using process, especially in the valve and water heating bathroom industry, the lead content in water is too high, which causes damage to the brain center and nervous system, and also causes influence on the digestive system, blood system and immune system. The governments of various countries have also been in turn provided with relevant laws and regulations to strictly limit the range of application of lead brass and its content. The U.S. NSF standard, japanese JIS standard and national GB standard also have regulations for the amount of heavy metals precipitated from drinking water contact products. Therefore, in recent years, a plurality of free-cutting brasses of lead-free and low-lead series have been developed at home and abroad, and the machinability is improved mainly by substituting lead with bismuth, lead with silicon, lead with antimony, and the like, and the comprehensive properties of the brass are improved by adding other alloy elements. In the industries of valves, water heating and bathroom, bismuth brass has the problems of difficult scrap recycling, poor welding performance and the like due to the defects generated in the hot processing process, and bismuth is used for replacing lead and cannot be implemented on a large scale. Antimony brass also has toxicity, so that the precipitation test of valve and water nozzle products cannot meet the requirement of 0.6 mu g/L specified by NSF61 standard, and the hidden danger of harming human health also exists, so the antimony brass can not be applied to valve and water heating bathroom industry.

Besides the requirements of environmental protection and easy cutting, valves and water heating products are generally produced by hot forging, so that brass materials are required to have excellent hot forging performance. The service properties that need to be taken into account are the dezincification corrosion resistance and the mirror polishing performance, since dezincification corrosion of brass is one of the main failure modes, and polishing is for the aesthetic appearance of the final plumbing fixture product. Among them, dezincification corrosion of brass is a selective corrosion, generally presenting two forms, one being uniform layered dezincification and one being plug corrosion. The requirements and the test method for the dezincification corrosion resistance performance are specified by the ISO standard, the Australia AS standard and the GB standard of China. Therefore, the service life of the product is determined by the dezincification corrosion resistance.

Disclosure of Invention

The first technical problem to be solved by the invention is to provide a brass alloy which has low lead content and excellent dezincification corrosion resistance and can meet the requirements of cutting and hot forging.

The technical scheme adopted by the invention for solving the first technical problem is as follows: the brass alloy is characterized by comprising the following components in percentage by mass: 59-63 wt%, Si: 0.2 to 0.8 wt%, Sn: 0.4 to 1.0 wt%, Pb: 0.05 to 0.15 wt%, Al: 0.1 to 0.2 wt%, As: 0.02-0.15 wt%, and the balance of Zn and inevitable impurities.

The brass is alpha + beta two-phase brass, Cu is a main element determining the proportion of an alpha phase, the content of other elements is combined, the content of copper is limited to 59-63 wt%, and the required proportion of the alpha phase and the beta phase is obtained.

Si is mainly used for improving the casting performance and the cutting performance of the alloy, and simultaneously, because the zinc equivalent of Si is 10, the proportion of alpha phase is reduced, and the proportion of beta phase required in the product is ensured. However, as the content of Si increases, the dezincification corrosion resistance becomes worse, so that the content of Si should be controlled to 0.2-0.8 wt% in order to ensure the dezincification corrosion resistance.

The dezincification corrosion resistance is improved by Sn, and the dezincification corrosion resistance is better along with the increase of the Sn content, so that the Sn content is controlled to be 0.4-1.0 wt%, and the cutting performance is influenced and the raw material cost of the product is increased due to the excessively high Sn content.

The Al element can improve the fluidity of the alloy, improve the hot forging performance and simultaneously increase the tensile strength of the alloy, but the beta phase is expanded due to the excessively high Al content to influence the dezincification resistance, so that the content is controlled to be 0.1-0.2 wt%.

As element can block Cu²⁺The formation of the copper-arsenic alloy can obviously inhibit the dezincification corrosion resistance of brass, and the addition of the copper-arsenic alloy is more environment-friendly and effective than the direct addition of simple substance arsenic. The control range of As is 0.02-0.15 wt%, and the excessive As can not meet the precipitation standard of drinking water systems in various countries or regions.

Preferably, the base structure of the brass alloy comprises an alpha phase and a beta phase, and the area ratio of the beta phase is 10-25%. The brass is alpha + beta biphase brass, alpha phase atoms are distributed in a face-centered cubic structure, and the brass has good plasticity and can make the material smoothly undergo cold machining deformation. The beta phase determines the dezincification resistance and the hot forging resistance of the brass, when the beta phase is high, the dezincification resistance cannot be achieved, and when the beta phase is low, the hot forging resistance is poor, so that the area ratio of the beta phase is 10-25%.

Preferably, the dezincification corrosion resistant depth of the brass alloy is less than 100 microns, and the machinability index reaches more than 65 percent of that of lead brass HPb 59-1.

The second technical problem to be solved by the invention is to provide a preparation method of the brass alloy.

The technical scheme adopted by the invention for solving the second technical problem is as follows: a preparation method of a brass alloy is characterized by comprising the following steps: the preparation method comprises the following preparation steps:

1) preparing materials: weighing Cu, Si, Sn, Pb, Al, Zn, copper-arsenic intermediate alloy and aluminum rare earth according to required components;

2) smelting: adding Cu, Si and Sn into a power frequency smelting furnace with the voltage of 350-400V, stirring and melting, reducing the power of the smelting furnace after the materials are melted, controlling the temperature to be 1000-1050 ℃, adding Pb, Al, Zn and copper-arsenic intermediate alloy into the furnace for melting, stirring and adding a brass slag remover after the materials are melted, and fishing out the slag by using a slag fishing tool;

3) and (3) component testing: sampling in molten copper, detecting the components of the molten copper, controlling the temperature of the molten copper at 950-1000 ℃ after the components meet the requirements, pressing aluminum rare earth into the position below the liquid level of the molten copper according to 0.1-0.3 wt% of the total amount of the molten copper for melting, heating the molten copper to 1100-1150 ℃, flaming for 2-5 min, controlling the molten copper to keep the temperature at 1050-1100 ℃ and standing for 5-10 min, and then, turning the molten copper into a heat preservation furnace;

4) casting: casting a copper bar blank by adopting continuous casting;

5) drawing: drawing and processing the copper bar blank into a copper bar;

6) annealing: and (3) preserving the heat of the copper rod at 450-520 ℃ for 3-4 h, and cooling the copper rod to below 100 ℃ after discharging at a cooling speed of 120-180 ℃/h.

In the annealing heat treatment process, the temperature of the copper rod is raised to more than 450 ℃ to ensure that the alpha + beta phase is converted to the alpha phase, the temperature is not too high and the time is not too long, otherwise, crystal grains grow slowly, and the recrystallization conversion cannot be finished at low temperature. And (3) rapidly cooling the copper bar after the copper bar is taken out of the furnace, separating out the beta phase again and dispersing the beta phase, and if the cooling speed is not enough, continuously distributing the beta phase in a strip-shaped and sheet-shaped manner to cause the dezincification corrosion resistance to be poor, so that the copper bar is cooled to be below 100 ℃ after being taken out of the furnace according to the cooling speed of 120-180 ℃/h.

Compared with the prior art, the invention has the advantages that:

1) the alloy of the invention meets the environmental protection requirement, and simultaneously utilizes the proportion control of Cu and Si elements and the addition of Sn and As elements to obtain 10-25% of beta phase, can reach the standard of dezincification corrosion resistance test below 100 microns, greatly reduces the failure of products in the valve and bathroom industries caused by dezincification, and simultaneously solves the problem that the conventional dezincification resistant alpha single-phase brass is difficult to be hot forged.

2) The brass alloy does not contain Sb element, has extremely low Pb content, and can meet the lead precipitation amount limitation of drinking water contact products such as NSF61, BS6920, GB18145 and the like. The alloy does not contain Bi element, is suitable for wide application and popularization, and does not have the problem of difficult waste recovery. The addition of Si is utilized to improve the cutting performance of the material. Meanwhile, the product has excellent polishing performance and obvious market competitive advantage.

Detailed Description

The present invention will be described in further detail with reference to examples.

The present invention provides 3 examples and 1 comparative example, the examples being the components of the present invention and prepared according to the preparation method of the present invention.

Example 1

The brass alloy comprises 61.5 wt% of Cu, 0.3 wt% of Si, 0.6 wt% of Sn, 0.1 wt% of Pb, 0.1 wt% of Al, 0.1 wt% of As and the balance of Zn.

The preparation steps of the brass alloy are as follows:

1) preparing materials: weighing Cu, Si, Sn, Pb, Al, Zn, a copper-arsenic intermediate alloy and aluminum rare earth, wherein the copper content of the copper-arsenic intermediate alloy is 70 wt%, and the aluminum content of the aluminum rare earth is 90 wt%.

2) Smelting: adding Cu, Si and Sn into a power frequency smelting furnace with the voltage of 380V, stirring and melting, reducing the power of the smelting furnace after the Cu, Si and Sn are melted, controlling the temperature to be 1000-1050 ℃, adding Pb, Al, Zn and copper-arsenic alloy into the furnace for melting, stirring and adding a brass slag removing agent after the materials are melted, and fishing out the slag by using a slag fishing tool.

3) And (3) component testing: sampling in molten copper, detecting the components of the molten copper, performing corresponding dilution or compensation treatment if the components do not meet the requirements until the components meet the requirements, controlling the temperature of molten copper at 950-1000 ℃ after the components meet the requirements, pressing aluminum rare earth into the liquid level of the molten copper for melting according to 0.2 wt% of the total charge amount, heating the molten copper to 1100-1150 ℃, flaming for 2-5 min, controlling the molten copper to keep the temperature of 1050-1100 ℃ and standing for 5-10 min, and then, turning the molten copper to a holding furnace;

4) casting: continuously casting to obtain a copper bar blank with the specification of 42.5 mm;

5) drawing: drawing and processing the copper bar blank into a copper bar with the thickness of 41 mm;

6) annealing: and (3) preserving the heat of the copper rod for 3h at 490 ℃, and cooling the copper rod to below 100 ℃ after discharging according to the cooling speed of 150 ℃/h.

Example 2

The brass alloy composition was 61.7 wt% Cu, 0.35 wt% Si, 0.7 wt% Sn, 0.13 wt% Pb, 0.1 wt% Al, 0.12 wt% As, and the balance Zn.

The preparation steps of the brass alloy are as follows:

4) casting: casting a copper bar blank with the thickness of 31.5mm by adopting continuous casting;

5) drawing: drawing and processing the copper bar blank into a copper bar with the thickness of 30 mm;

6) annealing: and (3) preserving the heat of the copper rod for 3.5h at 480 ℃, and cooling the copper rod to be below 100 ℃ after the copper rod is taken out of the furnace according to the cooling speed of 160 ℃/h.

Example 3

The brass alloy comprises, by weight, 62.5% of Cu, 0.2% of Si, 0.6% of Sn, 0.1% of Pb, 0.1% of Al, 0.1% of As, and the balance of Zn.

The preparation steps of the brass alloy are as follows:

2) Smelting: adding Cu, Si and Sn into a power frequency smelting furnace with the voltage of 390V, stirring and melting, reducing the power of the smelting furnace after the Cu, Si and Sn are melted, controlling the temperature to be 1000-1050 ℃, adding Pb, Al, Zn and copper-arsenic alloy into the furnace for melting, stirring and adding a brass slag removing agent after the materials are melted, and fishing out the slag by using a slag fishing tool.

4) casting: casting a copper bar blank by adopting continuous casting for 20 mm;

5) drawing: drawing and processing the copper bar blank into a copper bar with the thickness of 19 mm;

6) annealing: and (3) preserving the heat of the copper rod for 3h at 500 ℃, and cooling the copper rod to be below 100 ℃ after the copper rod is taken out of the furnace according to the cooling speed of 150 ℃/h.

Comparative example: american standard number C46500: 61.5 wt% of Cu, 0.82 wt% of Sn, 0.15 wt% of Pb, 0.052 wt% of As, and the balance of Zn.

The microstructures, machinability, polishing properties, dezincification corrosion resistance, and hot forging properties of the examples and comparative examples were tested. The specific test method is as follows, and the test results are shown in table 1.

And (3) detecting the microstructure: the beta phase ratio was measured according to the method specified in item 4.6 (image analyzer measurement method) of GB/T15749-.

And (3) testing the cutting performance: machining tests were carried out by using a lathe at a rotational speed of 500r/min with a machining amount of 0.3mm, and the cutting index was evaluated in terms of the size of chips on the basis of HPb 59-1.

And (3) testing the polishing performance: taking not less than 50cm²The peripheral surface of the bar is firstly polished by a 320-mesh abrasive belt, then is polished by a 600-mesh abrasive belt, and finally is polished by a coarse and a fine belt, the surface roughness of the bar is not more than 0.2 mu m, and then the mass point number of the polished surface is observed.

Dezincification corrosion resistance: the samples were tested according to the ISO 6509 precision of metals and alloys-Determination of the resistance of the fibre standard.

And (3) testing hot forging performance: the sample was heated to 650 c and free forged using a 40 ton hot forging press to see if edge cracking occurred.

TABLE 1 Properties of examples of the invention and comparative examples

Claims

1. The brass alloy is characterized by comprising the following components in percentage by mass: 59-63 wt%, Si: 0.2 to 0.8 wt%, Sn: 0.4 to 1.0 wt%, Pb: 0.05 to 0.15 wt%, Al: 0.1 to 0.2 wt%, As: 0.02-0.15 wt%, and the balance of Zn and inevitable impurities.

2. A brass alloy in accordance with claim 1, wherein: the brass alloy has a matrix structure comprising an alpha phase and a beta phase, wherein the area percentage of the beta phase is 10-25%.

3. A brass alloy in accordance with claim 1, wherein: the dezincification corrosion resistant depth of the brass alloy is below 100 microns, and the machinability index reaches more than 65% of that of lead brass HPb 59-1.

4. A method of making a brass alloy in accordance with any one of claims 1 to 3, wherein: the preparation method comprises the following preparation steps:

4) casting: casting a copper bar blank by adopting continuous casting;

5) drawing: drawing and processing the copper bar blank into a copper bar;