Method for producing free-cutting lead brass

Abstract

The application relates to a preparation method of a fast-cutting lead brass, which is characterized by comprising the following steps: ① smelting, raw materials are melted in a smelting furnace, the temperature is kept at 1010-1030 DEG C; the composition of the copper water is tested by sampling, the temperature is increased to 1060-1080 DEG C, the composition of the copper water meets the following weight percentage: Cu 57-57.5%, Pb 2.8-3.2%, and the impurity elements which need to be controlled, and the balance is zinc; ② horizontal continuous casting of a billet; ③ horizontal extrusion of a wire billet; ④ wire drawing; and ⑤ low-temperature bright annealing. The lead brass rod material has excellent machining performance, no curling and no burr, and the drilling is all broken materials; the tensile strength of the material reaches 460 Mpa; the surface roughness is below 0.2ummax; the rod material tolerance is controlled within 0.001mm; and the tolerance fluctuation is within 5%.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of copper alloys, in particular to a preparation method of lead brass. BACKGROUND

[0002] Lead brass, which belongs to brass, is widely used in bolts, nuts, small screws, shafts, gears, valves, clock parts, carburetors, precision instrument parts and other mechanical parts due to its good cold and hot working performance, machining performance, mechanical properties and corrosion resistance.

[0003] With the rapid development of household appliances, transportation, power engineering, metallurgy, engineering machinery and other fields, the parts become extremely complex, and thus the machining performance, drilling and chip removal performance and the roughness of the surface of the material are required to be more excellent, and the machining performance consistency of the raw material is required to be higher.

[0004] The common lead brass C3604 has good cutting performance, but due to unreasonable production process, the product appears to have more than 4 layers of curled cutting end material, which causes sticking and difficult chip removal, leads to low processing product efficiency, and the product surface roughness is more than 0.5ummax, which causes poor air tightness of the assembly container of the precision instrument, and the product is defective, and the material organization consistency is poor, which causes serious shaking in the machining process, and finally the material size tolerance is poor, and based on the above product problems, it is urgent to develop a production process for optimizing the machining performance of the existing lead brass. SUMMARY

[0005] The application solves the technical problem of providing a fast cutting lead brass preparation method with good surface roughness and small machining product tolerance.

[0006] The technical scheme adopted by the application to solve the above technical problem is that a fast cutting lead brass preparation method comprises the following steps:

[0007] ① Melting: the raw material is melted in a melting furnace, and the temperature is kept at 1010-1030 DEG C;

[0008] After the raw material is completely melted, the temperature is increased to 1080-1100 DEG C, a slag cleaning agent is added, and the slag is stirred and removed, after the slag removal is completed, the temperature is adjusted to 1010-1040 DEG C, the refining agent is pressed in, and the stirring is uniform, and the temperature is kept constant;

[0009] The composition of the copper water is tested by sampling, the temperature is increased to 1060-1080 DEG C, the composition of the copper water satisfies the following weight percentage: Cu 57-57.5%, Pb 2.8-3.2%, Fe+Sn≤1.2%, and the impurity elements need to be controlled, and the balance is zinc;

[0010] ②Horizontal continuous casting billet, the drawing starting temperature is 1060℃-1180℃, when the casting is stable, the temperature is kept at 1020℃-1040℃, the speed is 70mm / min-80mm / min, the temperature difference of water cooling is 15℃-20℃;

[0011] ③Horizontal extrusion wire billet, using an extruder, the extrusion temperature is 650℃-690℃;

[0012] ④Wire drawing, the wire drawn by pressure needs to be processed by 15-20% to become finished product;

[0013] ⑤Low temperature bright annealing, the wire after processing is subjected to bright annealing, the annealing temperature is 450-480℃, and the processing time is 2-3h.

[0014] The test results of the relationship between the machinability of H59 brass with Cu content of about 59% and the Pb content show that when the Pb content is 1.0% (HPb59-1), the machinability is about 75%; when the Pb content is 2.0% (HPb59-2), the machinability is about 92%; and when the Pb content is 3.0%, the machinability is about 100%; when the Pb content is greater than 3.0%, the machinability of the alloy will not be further improved, and on the contrary, the mechanical properties of the alloy will be comprehensively reduced due to the softness and low melting point of Pb particles. At this time, the Pb particles are in a fine form and uniformly distributed in the structure, and the effect of improving the machinability is even better than increasing the Pb content.

[0015] The extrusion process breaks the structure, eliminates the as-cast structure, realizes grain refinement, pressure processing and tempering, realizes the recovery recrystallization process, and further refines the grains. By using different dies, the size of the variable diameter is controlled to realize the control of the deformation rate.

[0016] The smaller the grain size, the higher the strength and hardness of the crystal. This is because the smaller the grain size, the larger the grain boundary area, and the grain boundary hinders the movement of dislocations, so the resistance to dislocation is greater, thus improving the strength and hardness of the crystal. Therefore, for the same material, the smaller the grain size, the easier the cutting.

[0017] By controlling the extrusion temperature, the temperature above 450℃-480℃ is the phase transition temperature interval, and above this temperature, enough β stable phase can be obtained, so the extrusion temperature needs to be above it, and at the same time, air cooling is used to ensure that the copper bar can quickly pass through this area to ensure that enough high-temperature stable β phase is preserved. However, the β stable phase at this time is in a network state, and through the above step E, heat preservation treatment is carried out to precipitate α phase on the surface of the β phase, breaking the network structure, thereby realizing smooth chip breaking during cutting.

[0018] In the two-phase brass, the α phase is soft, plastic and tough, and is not easy to cut; while the β phase is hard, and is easy to break chips during cutting. The α phase, the β phase morphology and the distribution ratio have great influence on the cutting performance. Increasing the proportion of the β phase in the structure, and making the shape of the α phase or the β phase into an isolated block, can improve the cutting performance of the material. To obtain more β phase ratio, low temperature annealing is required, and the annealing temperature is at 450-480°C, which is at the phase transition temperature. The β phase surface precipitates α phase, and the β phase network structure is broken, and tends to be small blocky. Using low temperature annealing, the α phase is divided into relatively isolated small blocky structure by numerous fine β phase. When machining, the chip is easy to break, the cutting effect is good, and the subsequent machining is easy to carry out.

[0019] Tensile processing of lead brass can increase the shearing force, and the cutting resistance can be greatly reduced due to the influence of Pb. However, the tensile reduction amount should not be too large, and the cold hardening should not be too large, otherwise the cutting resistance will be increased.

[0020] As preferred, the melting of raw materials in step ① includes the following steps: during the smelting process, first add 500 kg of back material to the melting area in the furnace, and the voltage is set to high voltage 400 V. After melting, add 500 kg of copper scrap. After the copper scrap is melted, finally add 2000 kg of processing back material to the furnace. After all the raw materials are melted, the temperature is maintained at 1010-1030°C.

[0021] The back material is mainly the skin material and the sawing material. The copper scrap mainly includes the recycled copper alloy waste, including bathroom parts, pipe fittings and the like. The processing back material mainly includes the edge material and defective waste during the processing.

[0022] As preferred, the drawing specification in step ② is φ175 mm.

[0023] As preferred, the extrusion machine in step ③ is a 1800 type horizontal extruder.

[0024] As preferred, the extrusion blank specification in step ③ is 7.8 mm.

[0025] As preferred, the wire drawing in step ④ is drawn to φ7.8 mm→φ7.2 mm.

[0026] As preferred, it further includes step ⑥ sizing, and the sizing is produced by using a combined drawing machine.

[0027] As preferred, the sizing production in step ⑥ is φ7.2 mm→φ7.0 mm.

[0028] As preferred, the main phases of the fast cutting lead brass obtained in step ⑥ are α and β phases, and the proportion of the β phase is 60%-70%. The β phase exists in the form of a single island.

[0029] Compared with the prior art, the lead brass rod has the advantages of excellent machining performance, no curling and no drillings, a tensile strength of the material reaching 460 MPa, a surface roughness below 0.2 um max, a rod tolerance controlled within 0.01 mm and a tolerance fluctuation within 5%. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A microstructure photograph of the lead brass in Example 1.

[0031] Figure 2 A photograph of the lead brass in Example 1 cut into drillings.

[0032] Figure 3 A microstructure photograph of the lead brass in Example 2.

[0033] Figure 4 A photograph of the lead brass in Example 2 cut into drillings.

[0034] Figure 5 A microstructure photograph of the lead brass in the comparative example.

[0035] Figure 6 A photograph of the lead brass in the comparative example cut into drillings. DETAILED DESCRIPTION

[0036] The application will be further described in detail below with reference to the accompanying drawings.

[0037] Example 1

[0038] A copper bar with a specification of φ9 mm is produced in the following specific process.

[0039] Step A: ① In a 3t power frequency melting furnace, 500 kg of return material drillings is first added into the melting area in the melting process, the voltage is set to high voltage 400 V, after melting, 500 kg of copper scrap is added, after the copper scrap is melted, 2000 kg of processing return material is finally added into the furnace, after all the materials are melted, the temperature is kept at 1010-1030 °C.

[0040] ② After the raw materials are completely melted, the temperature is increased to 1080-1100 °C, 3 kg of slag cleaning agent is added, the slag is stirred and removed, after the slag removal is completed, the temperature is adjusted to 1010-1040 °C, 3 kg of refining agent is pressed in, and the stirring is uniform, and the temperature is kept constant.

[0041] ③ The composition of the copper water is tested by sampling, Cu 57.1, Pb 2.85, Fe+Sn≤1.0, and other impurity elements that need to be controlled, zinc balance, the temperature is increased to 1060-1080 °C.

[0042] Step B: open the pull, pull specification φ175mm, pull the starting temperature at 1060-1180 ℃, when the casting is stable, the temperature is maintained at 1020-1040 ℃, the speed is 70-80 mm / min, the water temperature difference is 15-20 ℃.

[0043] Step C: using 1800 type horizontal extruder, extrusion temperature 650-680 ℃, ingot length 590 mm, extrusion blank specification 9.8 mm.

[0044] Step D: extrusion directly on the drawing production, φ9.8 mm→φ9.2 mm.

[0045] Step E: the processed disc line adopts bright annealing, annealing process 470 ℃+3h

[0046] Step F: the annealed disc line adopts combined drawing machine for sizing production, φ9.2 mm→φ9.0 mm.

[0047] The lead brass bar produced according to the above method has excellent machining performance, no curling and no foam, and the drilling is all broken material. The tensile strength of the material is 465 Mpa, the surface roughness is 0.1 um max, the bar tolerance is controlled at about 0.01 mm (1 silk), and the tolerance fluctuation is within 4%.

[0048] From Figure 1 and Figure 2 It can be seen that the main phase is а+β phase and elemental Pb phase, and the β phase is dispersed, all of which are small blocks, and the а phase is divided into many blocks, which directly reflects Figure 2 Cut into broken foam material, and the grain size of the organization is small, which further optimizes the cutting performance.

[0049] Example 2

[0050] A copper bar with a specification of φ15mm is produced as follows:

[0051] Step A: ① In the 3t power frequency melting furnace, first add 500kg of back material foam to the melting area in the melting process, and the voltage is set to high voltage 400V. After melting, add 500kg of copper scrap. After the copper scrap is melted, finally add 2000kg of processing back material to the furnace. After all the materials are melted, the temperature is maintained at 1010-1030 ℃.

[0052] ② After the raw materials are completely melted, the temperature is increased to 1080-1100 ℃, 3kg of slag cleaning agent is added, and the slag is stirred and removed. After the slag removal is completed, the temperature is adjusted to 1010-1040 ℃, 3kg of refining agent is pressed in, and the stirring is uniform. After standing and keeping warm.

[0053] ③Sampling test copper water composition, Cu57.3, Pb3.05, Fe+Sn≤1.2, and other need to control the impurity elements, zinc balance, the temperature to 1060℃-1080℃ can be increased.

[0054] Step B: open the pull, pull specification φ175mm, pull start temperature at 1060℃-1180℃, when the casting is stable, the temperature is maintained at 1020℃-1040℃, speed 70mm / min-80mm / min, water cooling water temperature difference 15℃-20℃.

[0055] Step C: using 1800 type horizontal extruder, extrusion temperature 650℃-660℃, ingot length 590mm, extrusion blank specification 16.3mm.

[0056] Step D: extrusion directly on the drawing production, φ16.3mm→φ15.2mm.

[0057] Step E: the disc line after processing is used for bright annealing, annealing process 470℃+3h

[0058] Step F: the annealed disc line is used for fixed size production by combined drawing machine, φ15.2mm→φ15.0mm.

[0059] The lead brass bar produced according to the above method has excellent machining performance, no curling and no foam, and the drilling is broken material. The tensile strength of the material is 455Mpa, the surface roughness is 0.15ummax, the bar tolerance is controlled at about 0.015mm (1.5 silk), and the tolerance fluctuation is within 3%.

[0060] From the above Figure 3 And Figure 4 It can be seen that the main phase is а+β phase and elemental Pb phase, and the β phase is dispersed, and the а phase is divided into many blocks, which directly reflects Figure 2 Cutting into broken foam material, and the grain size of the organization is small, which further optimizes the cutting performance.

[0061] Comparative example

[0062] A copper bar with a specification of φ9mm is produced as follows:

[0063] Step A: ① in 3t power frequency melting furnace, first add 500kg of back material foam to the melting area in the melting process, the voltage is high to 400V, after melting, add 500kg of copper scrap, after the copper scrap is melted, finally add 2000kg of processing back material into the furnace, after all the materials are melted, the temperature is maintained at 1010℃-1030℃.

[0064] After the raw material is completely melted, the temperature is increased to 1080-1100℃, 3kg of slag remover is added, and slag is removed by stirring. After slag removal is completed, the temperature is adjusted to 1010-1040℃, 3kg of refining agent is pressed in, and stirred uniformly. Then, it is kept still and heat preserved.

[0065] The composition of the copper water is tested by sampling, Cu 57.5, Pb 3.5, Fe+Sn≤1.0, and other impurity elements that need to be controlled, zinc balance, and the temperature is increased to 1060-1080℃.

[0066] Step B: open the drawing, the drawing specification is φ175mm, the drawing starting temperature is 1060-1180℃, when the casting is stable, the temperature is kept at 1020-1040℃, the speed is 70-80mm / min, and the water temperature difference is 15-20℃.

[0067] Step C: 1800 type horizontal extruder is used, the extrusion temperature is 650-660℃, the ingot length is 590mm, and the extrusion blank specification is 11mm.

[0068] Step D: direct drawing production after extrusion, φ11mm→φ10mm.

[0069] Step E: the processed disc wire is annealed by cover annealing, and the annealing process is 550℃+3h

[0070] Step F: after annealing, it is pickled, and then disc drawing is performed, φ10mm→φ9.3mm

[0071] Step F: the joint drawing machine is used for fixed-length production, φ9.3mm→φ9.0mm.

[0072] The lead brass rod produced according to the above method has excellent machining performance, no curling and no sub, and the drilling is all broken material. The tensile strength of the material is 555Mpa, the surface roughness is 0.7ummax, the rod tolerance is controlled at about 0.03mm (3 wires), and the tolerance fluctuation is more than 10%.

[0073] From the above Figure 5 And Figure 6 It can be seen that the main phases are а+β phases and elemental Pb phases, the β phases exist and are connected together, the а phases also exist in large blocks, and there are local abnormal organizations. The direct effect is Figure 6 The cutting is curled material, the grain fineness of the organization is 100um, the cutting property is deteriorated, the actual production is seriously affected by efficiency, and the product is continuously high in badness.

[0074] Table 1 performance table

[0075]

[0076] Note: The roughness is detected by TIME3200 metal surface roughness meter.

Claims

1. A method for preparing quick-cut leaded brass, characterized in that... Includes the following steps: ① Smelting: The raw materials are melted in a smelting furnace, and the temperature is maintained at 1010℃~1030℃; After the raw materials are completely melted, the temperature is raised to 1080℃~1100℃, a slag remover is added, and the slag is removed by stirring. After the slag is removed, the temperature is adjusted to 1010℃~1040℃, the refining agent is pressed in, the mixture is stirred evenly, and the mixture is kept at a constant temperature. To test the composition of the molten copper, the temperature should be raised to 1060℃~1080℃. The composition of the molten copper should meet the following weight percentages: Cu 57~57.5%, Pb 2.8~3.2%, and the impurity elements that need to be controlled, with the balance being zinc. ② For horizontal continuous casting of billets, the initial temperature of the casting is 1060℃~1180℃, and after the casting is stable, the temperature is maintained at 1020℃~1040℃. ③ Horizontal extrusion line blank, using an extrusion press, extrusion temperature 650℃~690℃; ④ The drawn and pressurized coiled wire needs to undergo a 15-20% processing rate to become a finished product; ⑤ Low-temperature bright annealing: The processed wire is subjected to bright annealing at a temperature of 450-480℃ to obtain free-cutting leaded brass. The raw material melting process in step ① includes the following steps: During the smelting process, 500 kg of recycled material is first added to the melting zone of the furnace, the voltage is set to a high voltage of 400V, and after melting, 500 kg of scrap copper is added. After the scrap copper melts, 2000 kg of processed recycled material is finally added to the furnace. After all the raw materials are melted, the temperature is maintained at 1010℃~1030℃. In step ⑤, the main phases of the free-cutting lead brass obtained are α and β phases, with the β phase accounting for 60% to 70%; the β phase exists in the form of isolated islands.

2. The method for preparing free-cutting leaded brass according to claim 1, characterized in that... The copper solution must meet the following condition: Fe + Sn ≤ 1.2%.

3. The method for preparing free-cutting leaded brass according to claim 1, characterized in that... The pulling speed in step ② is 70mm / min to 80mm / min, and the temperature difference between the inlet and outlet water of the water cooling system is 15℃ to 20℃.

4. The method for preparing free-cutting leaded brass according to claim 1, characterized in that... The annealing time in step ⑤ is 2 to 3 hours.

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