A method for improving the corrosion fatigue strength of marine copper alloys

Abstract

The present invention provides a method for improving the corrosion fatigue strength of marine copper alloys. The method comprises the following steps: S1: Weigh raw materials according to a preset formula and put them into an induction melting furnace, and obtain marine copper alloy castings based on the existing preparation process; S2: Perform vacuum heat treatment on the marine copper alloy castings; S3: Perform shot peening treatment on the marine copper alloy castings after vacuum heat treatment. Through the method for improving the corrosion fatigue strength of marine copper alloys according to the present invention, on the basis of keeping the existing preparation process unchanged, the corrosion fatigue strength of marine copper alloys, especially nickel-aluminum bronze alloy ZBAl 7-7-4-2, in a seawater medium is improved, providing strong support for the safe and reliable use of marine copper alloy components.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material processing and preparation, and in particular, to a method for improving the corrosion fatigue strength of marine copper alloys. Background Art

[0002] Marine copper alloys are widely used in components such as seawater pipelines, propellers, seawater pump valves and filters, and heat exchangers in the ship field due to their good hot and cold working properties, excellent resistance to marine fouling, good seawater corrosion resistance, and good welding properties. When in use, they are subjected to working conditions such as seawater corrosion and alternating stress. Therefore, improving the corrosion fatigue strength of marine copper alloys is very important for improving the service life of marine copper alloy components.

[0003] In the prior art, Li Huaji et al. studied the corrosion fatigue properties of five casting copper alloys (including manganese brass ZHMn55-3-1, manganese brass Lima55, aluminum brass ZHAl 67-5-2-2, medium manganese nickel-free zinc-containing bronze ZQAl10-6-7-3, and high manganese aluminum bronze ZQAl 12-8-3-2) used for ship propellers at that time (Metal Science and Technology, March 1984, Vol. 3, No. 1). The copper alloy specimens used were machined from cast specimens and were not subjected to any post-treatment, and it was pointed out that the corrosion fatigue resistance of bronze is better than that of brass, and appropriately controlling the zinc content can improve the corrosion fatigue performance of brass of the same grade. The patent document with the application number CN201710667249.1 discloses a corrosion system for rotating bending loading corrosion fatigue test and its manufacturing method. This method can adjust the balance of the corrosion liquid inlet and outlet in a short time, neither polluting the corrosion liquid nor avoiding the splash of the corrosion liquid driven by the high-speed rotating specimen. Liang Jian used this method to detect the corrosion fatigue strength of the casting copper alloy material ZCuAl8Mn13Fe3Ni2 (Journal of Mechanical Strength, 2004, 26(S): 074-076).

[0004] With the development of marine copper alloy materials and their processing and preparation technologies, currently, nickel-aluminum bronze alloys are mainly used in components such as seawater pump valves and filters, and propellers. However, there is no publicly reported method for improving the corrosion fatigue strength of marine nickel-aluminum bronze alloys in seawater media. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is: to propose a method for improving the corrosion fatigue strength of marine copper alloys, and on the basis of keeping the existing preparation process unchanged, to improve the corrosion fatigue strength of marine copper alloys, especially nickel-aluminum bronze alloy ZBAl 7-7-4-2, in seawater media, so as to provide strong support for the safe and reliable use of marine copper alloy components.

[0006] To solve the above technical problems, the present invention provides a method for improving the corrosion fatigue strength of marine copper alloys, which includes the following steps:

[0007] S1: Weigh the raw materials according to a preset formula and put them into an induction melting furnace, and obtain marine copper alloy castings based on the existing preparation process;

[0008] S2: Conduct vacuum heat treatment on the marine copper alloy castings;

[0009] S3: Conduct shot peening on the marine copper alloy castings after vacuum heat treatment.

[0010] Preferably, the marine copper alloy is nickel-aluminum bronze alloy ZBAl 7-7-4-2.

[0011] Preferably, in step S2, the vacuum degree ≤ 1×10 -2 Pa, the heat treatment temperature is between 750°C and 950°C, the holding time is 60 minutes to 120 minutes, and the cooling method is argon air cooling.

[0012] Preferably, in step S3, stainless steel shots with a diameter of 0.8 - 1.2 mm are used to conduct shot peening on the marine copper alloy castings after vacuum heat treatment.

[0013] Preferably, in step S3, the rotating speed of the shot peening machine head is 2000 - 2500 revolutions per minute, the number of shot peening times is 1 - 3 times, and the time for each shot peening is 15 minutes to 45 minutes.

[0014] Preferably, in step S1, the mass percentage of copper in the formula raw materials is greater than 50%.

[0015] Preferably, the mass percentage of aluminum is 7%, the mass percentage of nickel is 7%, the mass percentage of iron is 4%, the mass percentage of manganese is 2%, and the balance is copper and unavoidable impurities.

[0016] Preferably, step S1 includes the following specific operation steps:

[0017] S11: Weigh the raw materials containing copper, aluminum, nickel, iron, manganese and return materials according to a preset formula and put them into an induction melting furnace;

[0018] S12: Add cryolite to remove slag after all the raw materials are melted at the first preset temperature T1 to obtain a copper alloy melt;

[0019] S13: Measure the temperature of the copper alloy melt with a thermocouple, and conduct casting when it cools to the second preset temperature T2 to obtain marine nickel-aluminum bronze alloy ZBAl 7-7-4-2 castings, where T2 < T1.

[0020] Preferably, T1 = 1400°C and T2 = 1250°C.

[0021] Preferably, for the marine copper alloy casting after shot peening treatment in step S3, its seawater corrosion fatigue strength is increased by more than 20%.

[0022] Compared with the prior art, the method for improving the corrosion fatigue strength of marine copper alloy according to the present invention has the following beneficial effects:

[0023] 1) On the basis of keeping the existing preparation process unchanged, by adding double processes of vacuum heat treatment and surface shot peening, the improvement of the corrosion fatigue strength of marine copper alloy, especially nickel-aluminum bronze alloy ZBAl 7-7-4-2, in seawater medium is realized, providing strong support for the safe and reliable use of marine copper alloy parts;

[0024] 2) The corrosion fatigue strength of marine copper alloy castings, especially nickel-aluminum bronze ZBAl 7-7-4-2 castings, in seawater medium is successfully increased by more than 20%, and good applications have been realized in the preparation of nickel-aluminum bronze ZBAl 7-7-4-2 castings for seawater valves in the fields of ships and ocean engineering, and the batch production process has good stability. Specific Embodiments

[0025] To make the above objects, technical solutions and advantages of the present invention clearer and easier to understand, the present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only part of the embodiments of the present invention, which are only used to explain the present invention and do not constitute a limitation to the present invention. Without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0026] The present invention provides a method for improving the corrosion fatigue strength of marine copper alloy, including the following steps:

[0027] S1: Weigh raw materials according to a preset formula and put them into an induction melting furnace to obtain a marine copper alloy casting based on the existing preparation process;

[0028] S2: Perform vacuum heat treatment on the marine copper alloy casting;

[0029] S3: Perform shot peening treatment on the marine copper alloy casting after vacuum heat treatment.

[0030] Specifically, the method for improving the corrosion fatigue strength of marine copper alloy proposed by the present invention, on the basis of keeping the existing preparation process unchanged, first realizes the coordinated improvement of the strength and toughness of marine copper alloy by adding a vacuum heat treatment process, and then realizes the uniform distribution of compressive stress on the surface of marine copper alloy by adding a surface shot peening process, thereby successfully realizing the improvement of the corrosion fatigue strength of marine copper alloy in seawater medium and providing strong support for the safe and reliable use of marine copper alloy parts.

[0031] Preferably, the marine copper alloy is nickel-aluminum bronze alloy ZBAl 7-7-4-2.

[0032] Specifically, with the development of marine copper alloy materials and their processing and preparation technologies, currently, nickel-aluminum bronze alloy is the main copper alloy used in components such as seawater pump valves, filters, and propellers. When the marine copper alloy is nickel-aluminum bronze alloy ZBAl7-7-4-2, through the existing process of step S1, nickel-aluminum bronze ZBAl 7-7-4-2 castings can be obtained. Subsequently, after adding the double post-treatment processes of steps S2-S3 and testing according to the method specified in GB / T 4337-2015, the corrosion fatigue strength of nickel-aluminum bronze ZBAl 7-7-4-2 in seawater medium can be increased by more than 20%.

[0033] Preferably, in step S1, the mass percentage of copper in the formula raw materials is greater than 50%.

[0034] As one of the preferred examples of the present invention, in the formula raw materials for preparing marine copper alloy castings, especially nickel-aluminum bronze ZBAl 7-7-4-2 castings, in step S1, the mass percentage of aluminum is 7%, the mass percentage of nickel is 7%, the mass percentage of iron is 4%, the mass percentage of manganese is 2%, and the balance is copper and unavoidable impurities.

[0035] Preferably, step S1 includes the following specific operation steps:

[0036] S11: Weigh the raw materials containing copper, aluminum, nickel, iron, manganese, and return materials according to a preset formula and put them into an induction melting furnace.

[0037] S12: After all the raw materials are melted at the first preset temperature T1, add cryolite to remove slag to obtain a copper alloy melt.

[0038] S13: Measure the temperature of the copper alloy melt with a thermocouple and perform casting when it cools to the second preset temperature T2, where T2 < T1, to obtain marine nickel-aluminum bronze alloy ZBAl 7-7-4-2 castings.

[0039] Specifically, in the present invention, T1 is approximately equal to 1400 °C and T2 is approximately equal to 1250 °C.

[0040] Preferably, in step S2, the vacuum degree ≤ 1×10 -2 Pa, the heat treatment temperature is between 750 °C and 950 °C, the holding time is 60 minutes to 120 minutes, and the cooling method is air cooling with argon.

[0041] Specifically, vacuum heat treatment is a metal heat treatment process in which metal workpieces are heated under a negative pressure of less than 1 atmosphere. By controlling the above parameters in the vacuum heat treatment process, the internal structure of the above alloy can be transformed into coexisting phases and their proportions as required within the crystal grains and at the grain boundaries respectively, which can better achieve the coordinated improvement of the strength and toughness of marine copper alloys, especially nickel-aluminum bronze alloy ZBAl7-7-4-2.

[0042] Preferably, in step S3, nickel-aluminum bronze ZBAl 7-7-4-2 castings after vacuum heat treatment are shot-peened with stainless steel shots having a diameter of 0.8 to 1.2 mm.

[0043] Preferably, in step S3, the rotational speed of the shot-peening machine head is 2000 to 2500 revolutions per minute, the number of shot-peening times is 1 to 3 times, and the shot-peening time for each time is 15 to 45 minutes.

[0044] Specifically, step S3 aims to achieve a uniform distribution of compressive stress on the surface of marine copper alloys by adding a surface shot-peening process. By controlling the above parameters in the surface shot-peening process, the stress concentrated at the "tips" of the castings is improved, and the residual casting tensile stress with different directions on the surface of the castings is regulated into compressive stress, which can make the compressive stress more uniformly distributed on the surface of marine copper alloys, especially on the surface of nickel-aluminum bronze alloy ZBAl 7-7-4-2.

[0045] Preferably, the seawater corrosion fatigue strength of the marine copper alloy castings after being shot-peened in step S3 is increased by more than 20%.

[0046] Specifically, compared with the marine copper alloy castings without post-treatment processes in the prior art, on the basis of keeping the existing preparation process of marine copper alloy castings unchanged, the present invention first realizes the coordinated improvement of the strength and toughness of marine copper alloys by adding a vacuum heat treatment process, and then realizes the uniform distribution of compressive stress on the surface of marine copper alloys by adding a surface shot-peening process. Thus, the corrosion fatigue strength of marine copper alloys, especially nickel-aluminum bronze alloy ZBAl 7-7-4-2, in seawater medium is successfully improved, providing strong support for the safe and reliable use of marine copper alloy parts.

[0047] After testing, the present invention has successfully increased the corrosion fatigue strength of marine copper alloy castings, especially nickel-aluminum bronze ZBAl 7-7-4-2 castings, in seawater medium by more than 20%, and has been successfully applied in the preparation of nickel-aluminum bronze ZBAl 7-7-4-2 castings for seawater valves in the fields of ships and ocean engineering, and the batch production process has good stability.

[0048] Example 1

[0049] The present invention provides a method for improving the corrosion fatigue strength of marine nickel-aluminum bronze alloy ZBAl 7-7-4-2 castings, and the specific implementation steps are as follows:

[0050] Weigh raw materials such as copper, aluminum, nickel, iron, manganese and return materials according to a preset formula, put them into an induction melting furnace, add cryolite for slag removal after complete melting at about 1400°C to obtain a copper alloy melt, where the mass percentage of aluminum is 7%, the mass percentage of nickel is 7%, the mass percentage of iron is 4%, the mass percentage of manganese is 2%, and the balance is copper and inevitable impurities; measure the temperature of the copper alloy melt with a thermocouple and pour it at about 1250°C to obtain marine nickel-aluminum bronze alloy ZBAl 7-7-4-2 castings;

[0051] Then, perform vacuum heat treatment on the nickel-aluminum bronze ZBAl 7-7-4-2 castings, with a vacuum degree ≤ 1×10 -2 Pa, the heat treatment temperature is 900°C, the holding time is 90 minutes, and the cooling method is air cooling with argon;

[0052] Then, perform shot peening on the nickel-aluminum bronze ZBAl 7-7-4-2 castings after vacuum heat treatment with stainless steel shots with a diameter of about 1.0 mm. The rotation speed of the shot peening machine turntable is 2200 revolutions per minute, the number of shot peening times is 2 times, and the shot peening time for each time is 30 minutes.

[0053] After vacuum heat treatment and shot peening, tested according to the method specified in GB / T 4337-2015, the measured value of the corrosion fatigue strength of nickel-aluminum bronze ZBAl 7-7-4-2 in seawater medium is 152.14 MPa, which is increased by 21.5% compared with the corrosion fatigue strength value of 125.21 MPa of nickel-aluminum bronze alloy ZBAl 7-7-4-2 without vacuum heat treatment and shot peening.

[0054] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A method for improving the corrosion fatigue strength of marine copper alloys, characterized in that, The marine copper alloy is nickel-aluminum bronze alloy ZBAl 7-7-4-2, with the mass percentage of aluminum being 7%, the mass percentage of nickel being 7%, the mass percentage of iron being 4%, the mass percentage of manganese being 2%, and the balance being copper and inevitable impurities; it includes the following steps: S1: Weigh the raw materials according to the preset formula and put them into an induction melting furnace to obtain marine copper alloy castings based on the existing preparation process; S2: Conduct vacuum heat treatment on the marine copper alloy castings; S3: Conduct shot peening on the marine copper alloy castings after vacuum heat treatment; In step S2, the degree of vacuum ≤ 1×10 -2 Pa, the heat treatment temperature is between 750 °C and 950 °C, the holding time is 60 minutes to 120 minutes, and the cooling method is air cooling with argon; In step S3, use stainless steel shots with a diameter of 0.8 - 1.2 mm to conduct shot peening on the marine copper alloy castings after vacuum heat treatment; In step S3, the rotational speed of the shot peening machine head is 2000 - 2500 revolutions per minute, the number of shot peening times is 1 - 3 times, and the shot peening time for each time is 15 - 45 minutes.

2. A method for improving the corrosion fatigue strength of marine copper alloy according to claim 1, characterized in that, In step S1, the mass percentage of copper in the formula raw materials is greater than 50%.

3. A method for improving the corrosion fatigue strength of marine copper alloy according to claim 1, characterized in that, Step S1 includes the following specific operation steps: S11: Weigh the raw materials containing copper, aluminum, nickel, iron, manganese and return materials according to the preset formula and put them into an induction melting furnace; S12: Add cryolite for slag removal after all the raw materials are melted at the first preset temperature T1 to obtain a copper alloy melt; S13: Measure the temperature of the copper alloy melt with a thermocouple, and conduct casting when it cools to the second preset temperature T2 to obtain marine nickel-aluminum bronze alloy ZBAl 7-7-4-2 castings, where T2 < T1.

4. A method for improving the corrosion fatigue strength of marine copper alloy according to claim 3, characterized in that, T1 = 1400 °C, T2 = 1250 °C.

5. A method for improving the corrosion fatigue strength of marine copper alloy according to any one of claims 1-4, characterized in that After the marine copper alloy castings are subjected to shot peening treatment in step S3, their seawater corrosion fatigue strength is increased by more than 20%.