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Comparison of processing performance of oxygen-free copper rod and low-oxygen copper rod

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  • Time of issue:2021-11-12
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(Summary description)There are many manufacturing methods for continuous-rolled low-oxygen copper rods. The main processing requirements for copper rods in common downstream processes are SCR, Properzi, and Contirrod. In shaft furnace (individually adopt electric furnace performance and surface quality.

Comparison of processing performance of oxygen-free copper rod and low-oxygen copper rod

(Summary description)There are many manufacturing methods for continuous-rolled low-oxygen copper rods. The main processing requirements for copper rods in common downstream processes are SCR, Properzi, and Contirrod. In shaft furnace (individually adopt electric furnace performance and surface quality.

  • Categories:Industry News
  • Author:
  • Origin:
  • Time of issue:2021-11-12
  • Views:0

There are many manufacturing methods for continuous-rolled low-oxygen copper rods. The main processing requirements for copper rods in common downstream processes are SCR, Properzi, and Contirrod. In shaft furnace (individually adopt electric furnace performance and surface quality.

After melting with an induction electric furnace, the copper liquid passes through the holding furnace, chute, and tundish, and enters from the pouring pipe for casting;

1. Drawing performance The drawing performance of the closed gold-copper rod formed by the wheel and the steel belt (or double steel belt) is dependent on many factors in the mold cavity, with greater cooling strength, continuous; related, such as impurity content and distribution After the formation of the slab, the oxygen content and the content of the cast slab are then subjected to multi-pass rolling, i-laying, production process control and so on. When the performance of the copper rod is good, the copper wire rod produced is in the processed structure and the oxygen content is good, generally between 200 and 400 ppm in the drawing 0. 4mm and 0. 2mm. Oxygen-free copper rods, for example, there is a difference in the wire breakage rate between oxygen-free copper rods and low-oxygen copper rods

Basically, all domestic products are produced by Upcast continuous casting method, but the reasons for disconnection are different.

After the metal is melted in the induction electric furnace, the metal passes through the stone. 1. The influence of the melting method on the impurities such as S. The ink mold is continuously cast by upward casting and then cooled. During the manufacturing process, the electrolysis should be strictly controlled.

Rolled or cold drawn processing, the copper rods produced are mostly cast copper impurity content. Since the continuous casting and rolling process is generally constructed or cold-worked, the oxygen content is generally used for shaft furnace melting, and the effect of combustible gas is below 20ppm. Due to the difference between the two manufacturing processes, through oxidation and volatilization, the structure, oxygen content and distribution, and impurity of the copper rod can be reduced to a certain extent. Some impurities enter the copper liquid, and there are many aspects in the form and distribution of normal biomass. In relatively poor production, because S is abundantly present on the surface of the copper plate, it can reduce the weight {left pound is suitable for sweet low-chloride copper and I}. The difference in manufacturing method of the anaerobic forging rod is that the quality of raw material electrolytic copper is generally better than the melting method. Furnace, individual use induction electric furnace, induction electric furnace molten metal transfer method, holding furnace, chute, tundish one-piece induction furnace, flow casting method in tire metal mold or double belt metal mold, graphite in mold rolling method, hot rolling without rolling or Cold-rolled pickling method Alcohol-free pickling

38 Resource regeneration 201 0 1 2 is about half less. Zn, Cr, Mn, Cd and other elements can also be removed during oxidation and combustion, so the continuous casting and rolling method requires relatively low raw materials.

The upward continuous casting oxygen-free copper rod is melted by an induction electric furnace, and there is no oxygenation and combustion process. The "patina" and "copper beans" on the surface of the electrolytic copper plate

Almost all melted into the copper liquid. Among them, the molten S has a great influence on the plasticity of oxygen-free copper rods. It generates hard and brittle Cu and S in the copper, which increases the wire breakage rate.

Its formation reaction is:

6Cu+SO, =2Cu, O+Cu, S

At the same time, due to the limited capacity of the upward continuous casting method and the characteristics of the underflow type, when the impurity content of a certain electrolytic copper plate fluctuates, it will have a certain impact on the composition of the copper liquid around the mold mouth. Compared with the continuous casting and rolling process, the electrolysis The impurity content and stability requirements of the copper plate are higher.

2. The entry of impurities during the manufacturing process. During the production process, the continuous casting and rolling process needs to transfer the copper liquid through the holding furnace, chute, and tundish, which is relatively easy to cause the refractory material to peel off.

The hot rolling process needs to pass through the rolls, causing the iron to fall off, which will bring external inclusions to the copper rod. In hot rolling, the rolling of oxides on the skin and under the skin will adversely affect the drawing of the hypoxic rod.

As shown in Figure 1, Figure 2, and Figure 3, they are respectively the low-oxygen copper wire 0 40mm broken samples, which contain Fe and C r impurities after testing. Figure 4 shows the low-oxygen copper wire.

0 20mm Scanning electron microscope image of fracture with A J impurities. Figure 5 is a scan of the 0.10mm fracture of the low-oxygen copper wire containing refractory impurities, and Figure 6 is the scan of the low-oxygen copper wire O 10mm containing the peeling roll material H13 impurities.

In contrast, the upstream continuous casting process has a shorter process, and the copper liquid is transferred through the submerged furnace in the conjoined furnace, which has little impact on refractory materials.

The crystallization process of up-drawing continuous casting is carried out in the graphite mold, completely isolated from oxygen, and no heat is applied afterwards. There are fewer pollution sources that may be generated, and there are fewer opportunities for impurities to enter during the production process, as shown in Figure 7.

Figure 8 shows O 1 in oxygen-free copper wire

Fracture scan of Si impurities in 5mm.

The two elements 0 and S are almost insoluble in copper, and will form high melting point brittle compounds with copper, which has a great influence on the production process of copper rods.

3. The distribution of oxygen in low-oxygen copper rods and oxygen-free copper rods and their effects. Oxygen content has a significant impact on the wire-drawing performance of low-oxygen copper rods. When processed into 0.4mm copper wire, the obtained data, the V-shaped curve shows that when the oxygen content increases to the optimal value, the copper rod has the lowest wire breakage rate. This is because oxygen acts as a scavenger in the process of reacting with most impurities. Appropriate oxygen is also conducive to removing hydrogen in the copper liquid, generating water vapor to overflow, and reducing the formation of pores. The best oxygen content provides the best for the drawing process

conditions of.

Oxide distribution of low-oxygen copper rods: In the initial stage of solidification in continuous casting, the heat dissipation rate and uniform cooling are the main factors that determine the oxide distribution of copper rods. Uneven cooling will cause substantial differences in the internal structure of the copper rod, but the subsequent thermal processing, the columnar crystals will usually be destroyed, making the cuprous oxide particles finer and uniformly distributed. The typical situation caused by the aggregation of oxide particles is the center burst. Figures 9 and 10 are the scanning images of the 0. 40mm' f l ~ oxygen copper wire due to the center burst fracture. The uneven area is caused by cracks in the deformation of the oxide particles under the action of external force. As shown in Figure 1, the dark part is shown in Table 2. The influence of the manufacturing process on the quality of the copper rod is compared with the melting method. Shaft furnace combustion can remove some S impurities, induction electric furnace The S impurity cannot be removed, the furnace capacity is large, the composition fluctuation in the furnace is relatively small, the volume is small, and the composition in the furnace is easy to fluctuate. It is difficult to rule out pores and shrinkage. The surface oxide is rolled into the non-pickling method. The surface oxide layer is peeled off. Figure 1 Low oxygen copper wire O40mm 1 000× Figure 2 Low oxygen copper wire O40mm 200X Figure 3 Low oxygen copper wire eO40mm 1000× Picture 4 Low-oxygen copper wire 0 20mm 800X Picture 5 Oxygen copper wire mouth 0 1Omm Refractory impurity ring 6 Low-oxygen copper wire 0 1 Omm Roll H1 3 Exfoliated impurities

Figure 7 Oxygen-free copper wire 0 15mmS impurities. In addition to the influence of oxide particle distribution, copper rods with smaller oxide particles show better wire-drawing characteristics, and larger Cu O particles are likely to cause stress concentration points and break the wires. figure 1



3 is made of 0.49mm low-oxygen copper wire Cu2 0 particles

3 9


Technology n n 0 Yo y

One one one One 1 2 Ol 49mm low oxygen copper wire 2OOX 1 3 port O49mm low oxygen copper wire 2oO× Figure 1 4 O49mm low oxygen copper wire 2O0×

Fig. 15 is a photo of a broken end sample formed by the metallographic structure of an oxygen-free copper rod 12 5mm sample. Figure 14 is a photo of the initial fracture of 0.49mm in the low-oxygen copper wire.

The oxygen content of oxygen-free copper exceeds the standard, the copper rod becomes brittle, the elongation rate decreases, the fracture of the tensile pattern is dark red, and the crystal structure is loose. When [01 exceeds 8×1O, the process performance becomes worse, which is manifested by a sharp increase in the rate of breakage and wire breakage during casting and stretching. This is because oxygen can form Cu and O brittle phases with copper to form a Cu-Cu O eutectic, which is distributed on the grain boundary in a network structure. This brittle phase has high hardness and will be separated from the copper matrix during cold deformation, leading to a reduction in the mechanical properties of the copper rod due to resource regeneration by 2010/2, and it is easy to cause fracture in the subsequent processing. High oxygen content can also lead to a decrease in the conductivity of oxygen-free copper rods. Therefore, it is necessary to strictly control the oxygen content in the oxygen-free copper rod, so as to control the up-drawing continuous casting process and product quality.

4. Influence of hydrogen

In upward continuous casting, the control of oxygen content is low, and the side effects of oxides are greatly reduced, but the influence of hydrogen becomes a more significant problem. The solubility of hydrogen in copper is very large, and the molten liquid copper can dissolve 6 3 cm per 1 O Og. Hydrogen, which is 2 to 3 times greater than the solubility of hydrogen in solid state copper at the same temperature. The following equilibrium reactions exist in the melt after inhalation:

H2 0( g) =【 O】 +2【 H1

The pores and porosity are formed by the precipitation and accumulation of hydrogen from the supersaturated melt during the crystallization process. The hydrogen precipitated along the edge before crystallization can reduce the Cu Of l i to generate water vapor bubbles. As the feature of upward casting is the crystallization of copper liquid from top to bottom, the shape of the formed liquid cavity is almost cone-shaped. The gas precipitated before the copper liquid crystallizes is blocked in the solidified structure during the floating process, and pores are formed in the cast rod during crystallization. When the upper gas content is small, the hydrogen precipitated is present at the grain boundaries, forming looseness; when the gas content is high, it gathers into pores. Therefore, the pores and looseness are formed by both oxygen and water vapor. According to relevant data, when [H] exceeds O 6 X 10, the process performance becomes worse.

It is manifested by a sharp increase in the rate of rod interruption and wire breakage during casting and stretching.

Hydrogen originates from various technological links in the up-induction production process, such as the "patina" of the raw material electrolytic copper, the auxiliary material charcoal is moist, the climate is moist, and the graphite crystallizer is not dry. Therefore, the surface of the copper liquid in the melting furnace should be covered with roasted charcoal, and the electrolytic copper should try to remove the "patina", "copper beans" and "ears", which is very important to improve the quality of oxygen-free copper rods.

In the continuous casting and rolling process, the appropriate control of oxygen content (200-300ppm) is often used to control hydrogen. The reaction formula is:

Cu, 0+H, =2Cu+ H, 0

Because the copper liquid crystallizes from bottom to top in the casting wheel, the water vapor generated by the oxygen and hydrogen in the copper liquid can easily float up and escape, and most of the hydrogen in the copper liquid can be effectively removed, which has a greater impact on the copper rod. small.

3. Annealing performance In the annealing process of copper wire, the elongation of oxygen-free copper rod is 1 5% to 30% lower than that of low-oxygen copper under the same power and time. therefore. When annealing the copper wire, it is necessary to distinguish the material and use different annealing processes to ensure the flexibility of the product. The reason for this is better explained in the following metallographic comparison:

figure 1

5. Figure 1 6 is the oxygen-free copper rod 1

2. 5mm and middle 8mm specimens. The sample structure is divergent coarse columnar crystals with a grain size of 2 to 3 mm. There are only a few equiaxed grains on the surface and inside. Figures 17 and 18 are the middle and edge structures of the 8mm sample in the low-oxygen copper rod. The dark brown phase is the general annealing re-crystallization phase, and the white phase is the twin crystal phase formed during the annealing process. Generally, the size of the twin crystal phase is between 1 O ~ 2 O u m,

The dark brown color is about 25 u m. It can be seen that the low-oxygen copper rod is hot-rolled, so its structure is thermally deformed. The original cast structure has been broken and appears in the form of recrystallization; while the oxygen-free copper rod is a cast structure with coarse grains and few grain boundaries. , Since recrystallization occurs near the grain boundary and the intersection of twins,

Therefore, even through drawing deformation. The crystal edges are relatively small compared to low-oxygen copper rods, so higher annealing power is required.

In addition, oxygen and impurity elements in low-oxygen copper form oxides, which separate impurity elements from the copper solid solution, thereby reducing the influence of harmful impurity elements on annealing temperature, conductor resistance and rebound angle. Oxygen-free copper because of its low oxygen content, impurity elements still exist in the copper in solid solution form and formation and dispersion phases, resulting in a higher annealing temperature of oxygen-free copper than low-oxygen copper.

Four surface quality in the process of producing products such as magnet wires

It also puts forward requirements for the surface quality of copper rods.

The surface of the copper wire that needs to be drawn has no burrs, less copper powder, no rotten wires, and no oil stains. And through the torsion test to measure the quality of the surface copper powder and observe the recovery of the copper rod after twisting to determine its quality.

In the continuous casting and rolling process, the temperature of the copper billet is high between the exit of the casting wheel and the entrance of the J SL machine, and it is completely exposed to the air, so that a thick oxide layer is formed on the surface of the cast slab, about 40000~10 00 0 00 A, in the rolling

Figure 1 7 8mm' L ~ Oxygen Copper Rod Trial Metallographic Shao Weaving (Middle) Figure 18 8mm Low Oxygen tlo]'F Tangerine Box Phase Silk Weaving (During the edge process, with the rotation of the roller, oxide particles are rolled into the copper wire Surface. Alcohol or sulfuric acid is usually used for cleaning, and the chemical reaction formula is:



Due to the large difference between the density of copper and copper oxide, after the reaction, the surface film will form cracks and pores, and the shallow oxide particles will be partially dissolved and peeled off, forming pits and roughness on the surface, forming hemp during drawing. pit. Because Cu and O are high melting point and brittle compounds, for the deeper Cu and O rolled in, when the strip-shaped aggregate is stretched by the mold, it will cause burrs on the outer surface of the copper rod, which will cause trouble for subsequent painting. The oxygen-free copper rod manufactured by the upward continuous casting process is completely isolated from oxygen due to casting and cooling, and there is no subsequent hot rolling process. The surface of the copper rod has no oxides rolled into the surface, and the quality is good, and there is less copper powder after drawing. , No bad line, the above problems are less existed.

V. Conclusion The differences in the manufacturing methods of continuous casting and rolling low-oxygen copper rods and upward continuous casting oxygen-free copper rods are related to the structure, oxygen content and distribution, impurity existence mode, and hydrogen content, etc. Different, which determines the difference in the use characteristics of the two.

1. Continuous casting and rolling adopts shaft furnace melting, which has a large furnace capacity and relatively low requirements for the quality of electrolytic copper. The upward continuous casting process has higher requirements for raw materials.

2. The continuous casting and rolling process will bring impurities and oxides into the copper rod in the subsequent casting, hot rolling and other processes, which will bring greater disadvantages to the drawing, and the upward continuous casting process has no such problems;

3. Oxygen content and the distribution of oxides have a significant impact on the drawing performance of low-oxygen copper rods, and oxygen-free copper rods are easier to control this problem;

4. Hydrogen has a greater impact on the drawing performance of oxygen-free copper rods;

5. The difference in the tissue structure, the existence mode of impurities, and the types of impurities result in the annealing performance of the low-oxygen copper rods being significantly better than that of the oxygen-free copper rods;

6. Due to the rolling in of the surface oxide layer during hot rolling, the surface quality of the low-oxygen copper rod is significantly lower than that of the oxygen-free copper rod.

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