Preparation method of free-cutting lead brass alloy

Abstract

According to the preparation method of the free-cutting lead brass alloy, trace elements such as tellurium, cobalt, samarium and selenium are added into lead brass, the tellurium, the selenium and the like can easily form low-melting-point compounds with other elements, grain growth can be inhibited, dispersed distribution of fine lead particles is promoted, stress concentration is reduced, and the cutting performance is improved; by adding cobalt, samarium and the like, grain refinement is facilitated, distribution and forms of selenium, tellurium and other elements are changed, alloy fluidity is promoted, dispersed distribution of lead and the like is promoted to be more uniform, the cutting performance is further improved, in addition, dissolution of lead can be inhibited through the passive film layer, the environment-friendly performance is improved, and harm caused by dissolution of lead is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of materials, and particularly to a preparation method of free-cutting lead brass alloy. Background Art

[0002] Lead brass is widely used in many fields due to its unique properties. Generally, the lead content in lead brass is about 3%. However, lead is insoluble in copper and is distributed in the crystal grains and grain boundaries. The presence of lead can significantly improve the cutting performance, but lead is easily dissolved out, which has a greater impact on the environment or any other aspects. Therefore, how to reduce the amount of lead used and the dissolution of lead while retaining the cutting performance and other properties is an urgent problem to be solved. Summary of the Invention

[0003] To solve the above at least one technical defect, the present invention provides the following technical solutions:

[0004] This application document discloses a preparation method of free-cutting lead brass alloy, including the following steps:

[0005] First step, by mass, the raw material ratio is: lead 0.8 - 1.2%, sulfur 0.003 - 0.005%, tellurium 0.02 - 0.05%, selenium 0.1 - 0.3%, cobalt 0.01 - 0.03%, samarium 0.005 - 0.008%, and the balance is copper. Melting lead, sulfur, and copper in the raw materials, and then adding tellurium and selenium;

[0006] Second step, adding a modifier to the molten solution formed by the raw materials. The modifier includes fluorite, borax, silicon dioxide, titanium dioxide, sodium fluorosilicate, manganese, and nickel; adding cobalt and samarium and stirring after the modification treatment;

[0007] Third step, keeping the molten solution formed in the second step at 1000 - 1080 °C, and then heating it to 1150 - 1180 °C and pouring;

[0008] Fourth step, performing extrusion, drawing, and annealing treatments on the cast alloy billet;

[0009] Fifth step, performing passivation treatment on the billet after annealing treatment, and forming a passivation film layer on the billet through a passivation solution.

[0010] In this solution, trace elements such as tellurium, cobalt, samarium, and selenium are added to the lead brass. Among them, tellurium, selenium, etc. are easy to form low-melting-point compounds with other elements and can inhibit grain growth, promote the dispersed distribution of fine lead particles, reduce stress concentration, and help improve the cutting performance. The addition of cobalt, samarium, etc. helps to refine the grains, and changes the distribution and morphology of elements such as selenium and tellurium, which helps to promote the fluidity of the alloy and makes the dispersed distribution of lead, etc. more uniform, thereby improving the cutting performance again.

[0011] In addition, in this solution, the passivation film layer can inhibit the dissolution of lead, thereby improving the environmental protection performance and reducing the harm caused by lead dissolution, etc.

[0012] Furthermore, in the first step, the smelting temperature is 1100 - 1200 °C. In the second step, after adjusting the temperature to 950 - 1050 °C, the modifying agent is added. In the third step, it is kept warm at 1000 - 1080 °C for 20 - 40 min. The preferred parameters are helpful for improving the performance of the subsequent alloy.

[0013] Furthermore, in the fourth step, during the extrusion process, the processing rate is 60 - 90%, the drawing deformation rate is 75 - 85%, and the temperature during the annealing treatment is 370 - 410 °C. After extrusion, drawing, and annealing, it is helpful for improving the mechanical properties of the alloy, etc.

[0014] Furthermore, in the fifth step, by mass, the passivation solution includes 1000 parts of water, 5 - 8 parts of phytic acid, 2 - 4 parts of boric acid, 8 - 12 parts of ammonium chloride, 4 - 7 parts of sodium tartrate, 1 - 3 parts of hydrogen peroxide, and 14 - 16 parts of polyethylene glycol. Defining the components of the passivation solution can stably form a film layer on the surface of the alloy and better inhibit the dissolution of lead.

[0015] Furthermore, in the fifth step, the treatment temperature during passivation is 38 - 42 °C, and the time is 30 - 45 s.

[0016] Furthermore, by mass, the modifying agent includes 38 - 45% of fluorite, 30 - 35% of borax, 13 - 16% of silicon dioxide, 1 - 3% of titanium dioxide, 2 - 6% of sodium fluorosilicate, 0.3 - 0.9% of manganese, and 0.1 - 1.2% of nickel, which is helpful for improving the quality of the alloy.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. The present invention changes the alloy formula and subsequent treatment process. By adding elements such as tellurium, selenium, cobalt, and samarium, it is helpful for improving the cutting performance of the alloy, and the formation of the passivation film is helpful for reducing the dissolution of lead and reducing the harm caused by lead. Specific Embodiments

[0019] The present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1

[0021] A method for preparing a free-cutting lead brass alloy, comprising the following steps:

[0022] In the first step, materials are prepared according to the following raw material ratio. By mass, the raw material ratio is: lead 0.8%, sulfur 0.003%, tellurium 0.02%, selenium 0.1%, cobalt 0.01%, samarium 0.005%, and the balance is copper.

[0023] Add lead, sulfur, and copper in the raw materials into the furnace for smelting. The smelting temperature is 1150°C. After the raw materials are melted, add tellurium and selenium.

[0024] In the second step, after adjusting the temperature to 980°C, add a modifier to the molten solution of the formed raw materials. By mass, the modifier includes 40% fluorite, 33% borax, 16% silicon dioxide, 3% titanium dioxide, 6% sodium fluorosilicate, 0.9% manganese, and 1.1% nickel. After the modification treatment, add cobalt and samarium to the prepared materials and stir.

[0025] In the third step, adjust the temperature of the molten solution formed in the second step to 1050°C and keep it warm for 30 minutes. Then, raise the temperature to 1150°C and pour.

[0026] In the fourth step, perform extrusion, drawing, and annealing treatments on the poured alloy billets. Among them, the processing rate during extrusion is 75%, the speed of the extrusion wheel is 10 mm / s, the drawing deformation rate is 80%, the temperature during annealing treatment is 400°C, and the time is 2 hours.

[0027] In the fifth step, perform passivation treatment on the billets after annealing treatment. By mass, the passivation solution includes 1000 parts of water, 6 parts of phytic acid, 2 parts of boric acid, 8 parts of ammonium chloride, 5 parts of sodium tartrate, 2 parts of hydrogen peroxide, and 14 parts of polyethylene glycol. Immerse the billets in the passivation solution at a temperature of 40°C for 40 seconds.

[0028] Example 2

[0029] Compared with Example 1, the difference is that in the first step, the raw material ratio is 1.0% lead, 0.004% sulfur, 0.04% tellurium, 0.2% selenium, 0.02% cobalt, 0.007% samarium, and the balance is copper; in the fifth step, the passivation solution includes 1000 parts of water, 8 parts of phytic acid, 3 parts of boric acid, 11 parts of ammonium chloride, 6 parts of sodium tartrate, 2 parts of hydrogen peroxide, and 15 parts of polyethylene glycol.

[0030] Example 3

[0031] Compared with Example 1, the difference is that in the second step, the modifier includes 43% fluorite, 35% borax, 14% silicon dioxide, 3% titanium dioxide, 4% sodium fluorosilicate, 0.6% manganese, and 0.4% nickel.

[0032] Comparative Example 1

[0033] Compared with Example 1, the difference is that in this example, no tellurium is added.

[0034] Comparative Example 2

[0035] Compared with Example 1, the difference is that in this example, there is no passivation process.

[0036] The alloys prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and the evaluation of the cutting performance was based on B1112 free-cutting steel as 100%, as shown in Table 1 specifically.

[0037] Table 1

[0038] Cutting performance % Lead precipitation μg / L Example 1 ＞160 ＜7 Example 2 ＞160 ＜7 Example 3 ＞160 ＜7 Comparative Example 1 ＜120 ＜7 Comparative Example 2 ＞160 ＞15

[0039] As can be seen from Table 1, the cutting performance of the present lead brass alloy formed by the combination of multiple elements such as tellurium, selenium, cobalt and a small amount of lead is close to that of C36000, but the lead content is greatly reduced, and the precipitation of lead is inhibited by the passivation film, which helps to reduce the harm of lead in combination.

[0040] The above is only the preferred implementation manner of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions falling within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a free-cutting lead brass alloy, characterized in that, It includes the following steps: First step, by mass, the raw material ratio: lead 0.8 - 1.2%, sulfur 0.003 - 0.005%, tellurium 0.02 - 0.05%, selenium 0.1 - 0.3%, cobalt 0.01 - 0.03%, samarium 0.005 - 0.008%, and the balance is copper. Smelt lead, sulfur, and copper in the raw materials, and then add tellurium and selenium; Second step, add a modifier to the molten solution formed by the raw materials. The modifier includes fluorite, borax, silicon dioxide, titanium dioxide, sodium fluorosilicate, manganese, and nickel; add cobalt and samarium and stir after modification treatment; Third step, keep the molten solution formed in the second step at 1000 - 1080 °C, and then heat it up to 1150 - 1180 °C and pour it; Fourth step, perform extrusion, drawing, and annealing treatments on the cast alloy billet; Fifth step, perform passivation treatment on the billet after annealing treatment, and form a passivation film layer on the billet through a passivation solution.

2. The preparation method of the free-cutting leaded brass alloy according to claim 1, characterized in that: In the first step, the smelting temperature is 1100 - 1200 °C. In the second step, adjust the temperature to 950 - 1050 °C and then add the modifier. In the third step, keep it at 1000 - 1080 °C for 20 - 40 min.

3. The preparation method of the free-cutting leaded brass alloy according to claim 1, characterized in that: In the fourth step, the processing rate during extrusion is 60 - 90%, the drawing deformation rate is 75 - 85%, and the temperature during annealing treatment is 370 - 410 °C.

4. The preparation method of the free-cutting leaded brass alloy according to claim 1, characterized in that: In the fifth step, by mass, the passivation solution includes 1000 parts of water, 5 - 8 parts of phytic acid, 2 - 4 parts of boric acid, 8 - 12 parts of ammonium chloride, 4 - 7 parts of sodium tartrate, 1 - 3 parts of hydrogen peroxide, and 14 - 16 parts of polyethylene glycol.

5. The preparation method of the free-cutting leaded brass alloy according to claim 1, characterized in that: In the fifth step, the treatment temperature during passivation is 38 - 42 °C, and the time is 30 - 45 s.

6. The preparation method of the free-cutting leaded brass alloy according to claim 1, characterized in that: By mass, the modifier includes 38 - 45% of fluorite, 30 - 35% of borax, 13 - 16% of silicon dioxide, 1 - 3% of titanium dioxide, 2 - 6% of sodium fluorosilicate, 0.3 - 0.9% of manganese, and 0.1 - 1.2% of nickel.