DE-LEADING TREATMENT METHOD FOR LEAD-CONTAINING COPPER ALLOY AND DE-LEADING CORED WIRE USED IN SAID METHOD

Abstract

A copper alloy such as brass and bronze centered on rod products in which machinability is mainly required contains a certain amount of lead. The scrap of these products has been recycled at a high rate. A lead-removing step is indispensable for recycling the scrap of these products for low-lead products, and development of lead-removal techniques is urgently necessary. It is known that a material containing metal element calcium exhibits an effect in removing lead in a copper alloy, and since there are differences in the specific gravity and the melting point between a de-leading agent and a copper alloy, a de-leading method at a practical mass production level is required. In order to solve this problem, for the purpose of de-leading treatment of a copper alloy molten metal, there is provided a cored wire for lead removal characterized in that a metal band which does not affect the components of a copper alloy molten metal is used as a sheath material; a single de-leading agent and/or a de-leading coagent such as an aggregation/floatation agent for a PbCa compound required for a step is used as contents; and physical properties that endure mechanical and continuous feed by a cored wire feeding device are provided.

Claims

1. A de-leading treatment method of a lead-containing copper alloy, characterized in that the method comprises: successively feeding a cored wire for lead removal to molten metal of a copper alloy containing lead and allowing the cored wire to sink in the molten metal to subject the molten metal to de-leading treatment, the cored wire for lead removal comprising one or both of a de-leading agent and a de-leading coagent that are covered with a sheath material comprising copper or a copper alloy, wherein the de-leading agent is a granular or powdery de-leading agent containing metal element calcium, and the de-leading coagent is a granular or powdery de-leading coagent containing at least one of a Ca compound, an aggregation/floatation agent for a PbCa compound, a tin blocking material, copper, zinc, tin, a compound of copper, a compound of zinc, and a compound of tin.

2. The de-leading treatment method according to claim 1, wherein a plurality of the cored wire for lead removal are fed simultaneously in the molten metal.

3. The de-leading treatment method according to claim 1, wherein the cored wire for lead removal is fed and allowed to sink in the molten metal once or multiple times to subject the molten metal to de-leading treatment.

4. A cored wire for lead removal, characterized in that the cored wire for lead removal comprises one or both of a de-leading agent and a de-leading coagent that are covered with a sheath material comprising copper or a copper alloy, wherein the sheath material has a tensile strength of 150 to 600 N/mm.sup.2 and a ductility of 15 to 60%, wherein the de-leading agent is a granular or powdery de-leading agent containing metal element calcium, and wherein the de-leading coagent is a granular or powdery de-leading coagent containing at least one of a Ca compound, an aggregation/floatation agent for a PbCa compound, a tin blocking material, copper, zinc, tin, a compound of copper, a compound of zinc, and a compound of tin.

5. A cored wire for lead removal according to claim 4, wherein the sheath material covers both the de-leading agent and the de-leading coagent.

6. A cored wire for lead removal according to claim 4, wherein the sheath material covers the de-leading agent.

7. The cored wire for lead removal according to claim 4, wherein the diameter of the cored wire for lead removal is 4 to 30 mm.

8. The cored wire for lead removal according to claim 4, wherein the thickness of the sheath material of the cored wire for lead removal is 0.1 to 3 mm.

9. (canceled)

10. A cored wire for lead removal according to claim 4, wherein the sheath material covers the de-leading coagent.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] FIG. 1 is a schematic explanatory diagram of a cored wire feeding device for carrying out the present invention.

[0034] FIG. 2 is an explanatory diagram of a cross section of a cored wire for lead removal showing an example of the present invention.

[0035] FIG. 3 is an explanatory diagram of a cross section of a cored wire for lead removal showing an example of the present invention.

[0036] FIG. 4 is an explanatory diagram of a cross section of a cored wire for lead removal showing an example of the present invention.

[0037] FIG. 5 is an explanatory diagram of a cross section of a cored wire for lead removal showing an example of the present invention.

DESCRIPTION OF EMBODIMENTS

[0038] The cored wire feeding device used in the present invention will be described using FIG. 1 showing an example. A cored wire feeding device 10 is a device for feeding a cored wire for lead removal 1 to a treatment container 11 such as a melting furnace for treating a lead-containing copper alloy molten metal which is an object of the present invention. The cored wire for lead removal 1 is pulled out of a coil 12 wound in a coiled form and fed to the treatment container 11 by a feeder 13.

[0039] The feeder 13 is installed on a mount 14 and is configured to pull the cored wire for lead removal 1 out of the coil 12 and charge it into the molten metal 17 received in the treatment container 11. Various types of mechanisms can be employed in this feeder 13, but in a general mechanism, the cored wire for lead removal 1 is sandwiched by plural rolls rotated by a motor and a plurality of carrying rolls to continuously perform the pulling out and the charge.

[0040] A plurality of guides 15 for the cored wire for lead removal 1 are provided at suitable places on the mount 14 to smoothly pull out the cored wire for lead removal 1 pulled out of the coil 12 and send it to the feeder 13. A guide pipe 16 is provided between the feeder 13 and the treatment container 11 and bears the sending of the cored wire for lead removal 1 and the continuous charge thereof in the vertical direction into the molten metal 17. Further, the guide pipe 16 can be movably supported by a support arm 141 projecting from the mount 14.

[0041] The lower end of the guide pipe 16 may project into the treatment container 11 provided that it does not contact molten metal. The cored wire for lead removal 1 is preferably fed near the bottom of the treatment container 11, and it is preferred to adjust the feeding rate in consideration of the material and the thickness of the sheath material 4 so that it melts near the bottom of the treatment container 11. In the cored wire for lead removal 1 used in the present invention, metal calcium and calcium silicon are used singly or in combination as a de-leading agent 2. A granular or powdery de-leading agent 2 may be used.

[0042] Further, as shown in FIGS. 2 to 5 which are the cross section diagrams of the cored wire for lead removal, the de-leading agent 2 may be used in combination with the de-leading coagent 3 as the contents, that is, the components, of the cored wire for lead removal (FIGS. 2 and 3), but only one of the de-leading agent 2 and the de-leading coagent 3 may also be used as the content to form an independent separate cored wire for lead removal (FIGS. 4 and 5). This suggests that various matrices of de-leading treatment occurring in practical mass production can be flexibly responded to by using a plurality of cored wires for lead removal 1. Therefore, the cored wire for lead removal 1 used for lead removal in the present invention includes those in which the de-leading agent 2 and/or the de-leading coagent 3 is used singly or in combination.

[0043] The present invention is characterized by using a metal such as copper, brass or bronze, or a copper alloy containing zinc, tin, or the like that does not have compositional influence on the copper alloy, as the sheath material 4 for covering the de-leading agent 2 and/or the de-leading coagent 3.

[0044] Unlike an iron cored wire produced using an existing technique, the sheath material of copper or a copper alloy used in the present invention shows high work hardening when it is worked. This is a phenomenon that when stress is given to a metal, hardness of the metal is increased by plastic deformation, and the characteristics are shown by the size of a work hardening factor. A common carbon steel (0.6C steel) has a work hardening factor of 0.15, while 65/35 brass which is one of the sheath materials 4 used in the present invention has a work hardening factor of 0.53, which is a numerical value 3 times or more larger than that of the common carbon steel. This means that when the copper alloy is worked as the sheath material 4, the function such as flexibility that is expected from the cored wire for lead removal 1 will be lost.

[0045] Since tensile strength and ductility are generally significantly different depending on material, a cored wire for lead removal 1 that endures practical use must be prepared by changing production conditions of the cored wire taking the type and physical properties of the sheath material 4 into account. In order to solve this problem, the metal to be used for the sheath material 4 has been tested in the present invention, and it has been elucidated that, with respect to the physical properties required for the cored wire for lead removal, tensile strength is desirably in the range of 150 to 600 N/mm.sup.2, and ductility is desirably from 15 to 60%. When tensile strength is less than 150 N/mm.sup.2, risk of cutting is high, and the metal does not endure use; and when tensile strength is larger than 600 N/mm.sup.2, the metal is too strong and adversely affects the production of the cored wire for lead removal, and the use of winding into and pulling out of a coil has been difficult. Further, when ductility is less than 15%, there is no room for deformation, and the production, working, and feed of the cored wire for lead removal is difficult; and when ductility is larger than 60%, an inconvenience occurs in the dimension of the cored wire for lead removal and in keeping the shape thereof during feed.

[0046] Further, the diameter of the cored wire for lead removal is preferably 4 to 30 mm for the purpose of facilitating production and working of the cored wire for lead removal and keeping the shape thereof during feed. Furthermore, from the same purpose, the thickness of the sheath material 4 used in the present invention is desirably in the range of 0.1 mm to 3.0 mm. This is because when the thickness is less than 0.1 mm, strength is low, which may cause tearing and cutting, and when the thickness is more than 3.0 mm, it is difficult to bend a cored wire for lead removal 1, which makes it difficult to produce and feed the cored wire.

[0047] Further, the best material and thickness of the sheath 41 used in the present invention can be selected in the range proposed above in consideration of the matrix of physical properties and the de-leading effect also taking the result of calculation of the position and time to melt into account so that the contents may act more efficiently in the molten metal to be de-leaded. Furthermore, with respect to the material of the sheath material 4, those having the quality described in JIS material symbols C1020-1441 and C2100-4640 correspond to the material used in the present invention, and it is practically convenient to use these materials.

[0048] With respect to the contents of the cored wire for lead removal, the following various additives can be provided as the de-leading coagent 3 for increasing the de-leading effect. A granular or powdery coagent can be used as the de-leading coagent 3. Examples include a Ca compound 31 such as CaF2, CaCO3, and CaO which contributes to the fixing of the de-leading agent in the cored wire for lead removal and is used for the flux after the reaction, an aggregation/floatation agent for a PbCa compound 32, a mineral containing sodium fluoride and alumina silica glass or the like 33, which is generally called a tin blocking agent, a metal such as copper, zinc, and tin, or a compound thereof 34, which is a component constituting the copper alloy itself to be de-leaded and which contributes to the fixing of the de-leading agent in the cored wire for lead removal and the adjustment of components of the molten metal after de-leading. These can be contained in the cored wire for lead removal by selecting desired additives. Further, as an alternative in the present invention, it is possible to produce a cored wire for lead removal containing only one of these additives, for example, only a Ca compound (FIG. 5), only an aggregation floatation agent, only a tin blocking agent, or only a metal such as copper or a compound thereof. The cored wire containing only the de-leading coagent may also be referred to as an auxiliary cored wire for lead removal. As described above, the cored wire for lead removal 1 include those in which one or more de-leading agents and one or more de-leading coagents are covered with a sheath material, those in which one or more de-leading agents are covered with a sheath material, and those in which one or more de-leading coagents are covered with a sheath material. Further, the cored wire for lead removal 1 include those in which one or more de-leading agents and one de-leading coagent are covered with a sheath material and those in which one de-leading agent and one or more de-leading coagents are covered with a sheath material.

[0049] For integrating and fixing the de-leading agent 2 and/or the de-leading coagent 3 to the cored wire 1, the ductility of the sheath material 4 is exhibited during the working of the cored wire for lead removal 1, and the cored wire for lead removal 1 is compressed while closely contacting the de-leading agent 2 and the de-leading coagent 3 as the contents with the cored wire for lead removal 1. As a method for performing the above, both ends of the sheath material 4 are preferably secured, for example, by caulking 5 to cover the contents.

Examples

[0050] In order to verify the effectiveness of the present invention, the tests shown in Table 1 were performed utilizing the cored wire feeding device 10 shown in FIG. 1.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Wire contents Metal calcium (mass %) 90 90 Specific gravity (g/cm.sup.3) 1.55 1.55 Fluorite (mass %) 10 10 Specific gravity (g/cm.sup.3) 3.18 3.18 Sheath material Material Brass Brass Wire diameter (mm) 13 13 Sheath material thickness (mm) 0.35 0.4 Wire average specific gravity (g/cm.sup.3) 4.6 5.0 Copper alloy Material Brass Brass molten metal Specific gravity (g/cm.sup.3) 8.3 8.2 Molten metal weight (kg) 4000 4500 Molten metal temperature ( C.) 950 950 Number of wires 1 1 Wire feed length (m) 350 450 Wire feed time (min) 10 15 Amount of removed lead (kg) 40 70

[0051] In the above Examples 1 and 2, the cored wire for lead removal 1 was continuously fed into the brass molten metal 17. A predetermined amount (length) of the cored wire for lead removal 1 of the present invention was able to be charged into the molten metal without causing problems such as fracture, rupture, and opening, and the de-leading described in Table 1 was accomplished. From Examples, it is determined that the best cored wire for lead removal can be produced, and the conditions of feeding the same can be set, in accordance with the weight and temperature of molten metal and the shape of a furnace. The results of Examples above proved that it was possible to perform de-leading in tens of kilogram unit in the mass production scale using a real machine which was not able to be achieved in prior art examples. Further, since problems such as fracture, rupture, and opening did not occur irrespective of using a sheath material which did not belong to a prior art material, it is determined that the characteristics required for the sheath material specified in the present invention satisfy the conditions that can endure the production of a cored wire for lead removal and the feed thereof by a machine.

[0052] Note that although the tests using brass were performed in the Examples, it is apparent that the tests are not limited to brass but can be similarly applied to a copper alloy such as bronze.

INDUSTRIAL APPLICABILITY

[0053] In view of the present circumstances in which many products of a copper alloy including brass are produced by remelting the scrap thereof, it is extremely important to remake scrap into a raw material to produce a good quality copper alloy. The present invention extremely efficiently removes lead contained in a copper alloy, allows mass remaking of a copper alloy in a good condition, and can achieve quality improvement of copper alloy products and cost reduction of the products produced therefrom. Thus, the present invention has a large in-use effect.