A production method for preventing eccentricity in continuous casting of solid-liquid bimetals

Abstract

The present invention provides a method for preventing eccentricity in the continuous casting of solid-liquid bimetals, which comprises the following steps: (1) subjecting a metal inner core to drawing, annealing, straightening, and grinding and rounding to obtain an inner core body; (2) preheating, casting, and crystallizing the inner core body. The method for preventing eccentricity in the continuous casting of solid-liquid bimetals according to the present invention ensures that the deviation of the raw material is within the allowable range through the previous material regularization (drawing, annealing, straightening, grinding and rounding), and ensures the combination of the raw material and the outer metal layer and controls the external metal shrinkage through the preheating process; adopts the centering technology for the inlet and outlet of the furnace body to ensure that the inlet and outlet of the material are in the center position; and adopts the anti-eccentric crystallization die butt joint structure to ensure that no deviation occurs at the crystallization position.

Description

Technical Field

[0001] The present invention belongs to the field of casting, and particularly relates to a method for preventing eccentricity in continuous casting of solid-liquid bimetal. Background Art

[0002] Solid-liquid bimetal composite casting is a new casting method that combines two metal materials, making use of the performance advantages of the two metals respectively to form a firm metallurgical bond. The main methods for preparing bimetal composite materials are casting composite method, explosion composite method, rolling composite method, extrusion composite method and diffusion welding method. The solid-liquid bimetal composite casting method has the characteristics of good interface bonding, high production efficiency and wide alloy application range compared with other bimetal composite methods, and is thus increasingly widely used.

[0003] The main difficulty in the process of continuous casting of solid-liquid bimetal is the control of the uniformity of the outer cladding metal layer. At present, it is possible to achieve bimetal composite casting, but the uniformity of the surface metal cladding layer cannot be effectively controlled, resulting in defects in the performance of the fabricated material and affecting the performance of the material. Summary of the Invention

[0004] In view of this, the present invention aims to overcome the defects in the prior art and proposes a method for preventing eccentricity in continuous casting of solid-liquid bimetal.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows:

[0006] A method for preventing eccentricity in continuous casting of solid-liquid bimetal includes the following steps:

[0007] (1) The metal inner core is drawn, annealed, straightened and polished to obtain an inner core body.

[0008] (2) The obtained inner core body is preheated, cast and crystallized.

[0009] Further, the difference between the inner diameter of the drawing die in the drawing step of step (1) and the outer diameter of the metal inner core before drawing is 2 mm ± 5 μm. The metal inner core is first pre-straightened by a pre-straightening mechanism for the coiled material, and then enters the drawing die. The drawing die uses a cold drawing die. When the material enters the drawing die, a lubricating intermediate material (such as wire drawing powder, lubricating oil, etc.) needs to be added to facilitate drawing and protect the raw material from problems such as burrs and scratches that affect the quality of the raw material. Then it enters an inverted wire drawing machine for actual drawing.

[0010] Further, the temperature of the annealing step in the step (1) is 550 - 700 °C, and the heat preservation is for 5 - 8 hours. During the wire drawing process of the material, stress concentration will occur in the metal, increasing the hardness of the material. To facilitate the processing of subsequent processes, the material needs to be annealed. The annealing process selects a suitable annealing process according to the different processed materials, which can achieve the functions of reducing the hardness of the raw material and increasing the toughness.

[0011] Further, in the grinding and rounding step in the step (1), a grinding machine is used; the grinding machine is a round wheel sand belt machine; the running speed of the round wheel sand belt machine is coordinated with the advancing speed of the metal core; the running speed of the round wheel sand belt machine is 800 - 1200 revolutions per minute, and the advancing speed of the metal core is 35 - 50 cm / min.

[0012] In the grinding and rounding step, the round wheel sand belt makes a circular motion around the material, and the circumference of the circular motion is the circumference of the required material, ensuring that the roundness of the material after pre - straightening is controlled within ±0.1 mm. The purpose is to remove the slight gaps existing after straightening and the oxide layer on the surface of the raw material through the rotary sand belt machine, exposing the core material matrix to ensure the quality of the subsequent continuous casting process; and to remove the oxide particles and surface oil stains on the surface of the material, ensuring that the surface - coated metal can be combined with the base material in the later stage.

[0013] Further, the temperature of the pre - heating step in the step (2) is 50 - 100 °C lower than the crystallization temperature of the metal core; the pre - heating step uses a pre - heating barrel, and the pre - heating barrel uses medium - and high - frequency heating. The pre - heating barrel is used to raise the temperature of the material so that when the material enters the horizontal continuous casting furnace body, there will be no rapid condensation of the molten metal, enabling atomic diffusion between the surface - coated metal molten liquid and the metal core to form a molecular - level bond. If the temperature in the pre - heating barrel is too high, voids will be formed on the bonding surface; if the temperature is too low, condensation delamination and incomplete surface crystallization will occur on the bonding surface.

[0014] Further, in the casting step in the step (2), the central alignment of the furnace body inlet and the furnace body outlet is ensured; the furnace body uses medium - and high - frequency heating. If there is a deviation in the central alignment of the furnace body inlet and the furnace body outlet, it will seriously affect the uniformity of the composite casting. The heating efficiency of medium - and high - frequency heating is higher than that of radiation heating and resistance heating, which is beneficial to the maintenance and control of the metal temperature.

[0015] Further, in the casting step of step (2), the temperature of the clad metal molten liquid is 30 - 100°C higher than the melting point of the clad metal; in the casting step of step (2), the amount of each addition of the clad metal molten liquid is 5 - 10% of the clad metal molten liquid in the furnace body. The temperature of the clad metal molten liquid in the furnace body is higher than the melting point of the clad metal, which can prevent heat loss caused by the base material taking away heat while ensuring the temperature during product crystallization. Adding an excessive amount of clad metal molten liquid will cause a sharp drop in the metal temperature in the furnace, thus affecting production and the quality of bimetal composite continuous casting.

[0016] Further, in the crystallization step of step (2), the crystallization mold and the crystallizer are connected in a spindle shape. The crystallizer and the crystallization mold must be centered horizontally and vertically. If the crystallization mold and the crystallizer are installed by threaded docking, it is very easy for the center of the crystallizer to deviate from the center of the mold, resulting in the deviation of the surface metal crystallization during bimetal composite casting.

[0017] In the crystallization step of step (2), the temperature of the cooling water is 35 - 45°C; in the crystallization step of step (2), the pressure inside the pipe is 0.5 - 0.6 Mpa. Cooling water needs to be added to the crystallizer to cool the material, and the temperature and pressure of the cooling water directly affect the crystallization quality and production efficiency. The cooling water enters the cooling crystallization mold through the copper head of the crystallizer, so as to cause the molten metal to crystallize outside the inner core body. Too high or too low temperature of the cooling water will affect the surface quality of the product and production efficiency. The cooling water in the crystallizer needs to maintain a certain flow rate. High pressure and high flow rate can quickly take away the heat conducted from the crystallization mold to the copper head of the crystallizer, thus achieving the effect of cooling crystallization.

[0018] Application of the solid-liquid bimetal continuous casting anti-eccentric production method, application of the production method in the preparation of bimetal round bar composite wire; the bimetal round bar composite wire is one of copper-clad steel wire, zinc-clad steel wire or aluminum-clad copper wire.

[0019] A solid-liquid bimetal continuous casting anti-eccentric production line, the production line includes a drawing die, an inverted wire drawing machine, an annealing furnace, a straightening machine, a grinding machine, a preheating barrel, a horizontal continuous casting furnace, a crystallizer and a traction device; the centers of the straightening machine, the grinding machine, the preheating barrel, the inlet and outlet of the horizontal continuous casting furnace, the crystallization mold of the crystallizer and the traction device are all aligned; the crystallization mold and the crystallizer are connected in a spindle shape; the grinding machine is a sand belt grinding machine. The traction device and the inlet and outlet of the horizontal continuous casting furnace are centered, and the deviation in the up, down, left and right directions is controlled within ±2 mm. If the deviation increases, it will cause accelerated wear of the crystallization mold, and ultimately lead to non-round or roundness deviation of the product.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The method for preventing eccentricity in the continuous casting of solid-liquid bimetals according to the present invention ensures that the deviation of the raw materials is within the allowable range through the previous material regularization (drawing, annealing, straightening, grinding and rounding), and ensures the combination of the raw materials and the outer metal layer and controls the external metal shrinkage through the preheating process; the centering technology for the inlet and outlet of the furnace body is adopted to ensure that the inlet and outlet of the material are in the center position; the anti-eccentric crystallization die butt joint structure is adopted to ensure that no deviation occurs at the crystallization position. Description of the Drawings

[0022] Figure 1 It is a schematic diagram of the anti-eccentric production line for continuous casting of solid-liquid bimetals according to the embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of the spindle-shaped connection between the crystallization die and the crystallizer according to the embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the zinc-coated steel bimetal composite grounding wire according to Embodiment 1 of the present invention;

[0025] Figure 4 It is a schematic diagram of the surface of the steel core with slip marks lacking the grinding and rounding step according to Comparative Example 1 of the present invention;

[0026] Figure 5 It is a schematic diagram of the surface of the steel core with oil stains and impurities lacking the grinding and rounding step according to Comparative Example 1 of the present invention;

[0027] Figure 6 It is a cross-sectional view of the product lacking the grinding and rounding step according to Comparative Example 1 of the present invention;

[0028] Figure 7 It is a surface schematic diagram of the product lacking the grinding and rounding step according to Comparative Example 1 of the present invention;

[0029] Figure 8 It is a schematic diagram of incomplete crystallization on the surface of the product according to Comparative Example 2 of the present invention;

[0030] Figure 9 It is a schematic diagram of exposed steel due to eccentricity of the product according to Comparative Example 2 of the present invention;

[0031] Figure 10 It is a schematic diagram of the eccentricity of the product according to Comparative Example 3 of the present invention.

[0032] Description of the Reference Numerals:

[0033] 1. Drawing die; 2. Inverted wire drawing machine; 3. Annealing furnace; 4. Straightening machine; 5. Grinding machine; 6. Preheating barrel; 7. Horizontal continuous casting furnace; 8. Traction equipment; 9. Crystallization die notch; 10. Crystallizer die seat. Detailed Embodiments

[0034] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. The test reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0035] The present invention will be described in detail below with reference to the examples.

[0036] Example 1 Production of Zinc-Clad Steel Bimetallic Composite Grounding Wire

[0037] The raw material is Φ14 black steel bar (Q235 material), and the outer covering material is 0# zinc alloy (zinc content 99.9%). The produced product is a zinc-clad steel grounding wire product with a total diameter of Φ14 and an outer zinc layer thickness of 1 mm (the inner steel core diameter is Φ12). The production method is as follows:

[0038] 1. Due to the deviation of the steel specifications on the market, the outer diameter of the Φ12 steel has a certain deviation. To ensure the outer diameter and roundness of the raw material, the steel needs to be drawn. The drawing die uses an imported die with an outer diameter of Φ14 mm and an exit of 12 mm ± 2 um for drawing; specific steps: first place the black steel bar on the feeding rack, then introduce the steel bar into the straightening unit. After the steel bar is straightened, it enters the drawing die. During drawing, appropriate lubricants or wire-drawing powders and other media are added to lubricate and protect the drawing die. After the steel bar enters the drawing die, it is traction-drawn through an inverted wire-drawing machine, which can achieve the purpose of removing the oxide scale on the steel surface and regularizing the outer diameter of the steel;

[0039] 2. Since the hardness of the steel increases after drawing, for subsequent production, the steel needs to be annealed to ensure that the inner core steel parameters meet the national technical parameter requirements for the grounding wire steel core; the annealing furnace uses an RT3-850-9 model annealing furnace with a maximum temperature of 950 °C. Set the annealing temperature to 650 °C and the holding time to 6.5 hours, and then let it cool naturally in the furnace to obtain a steel core that meets the national standards, with a hardness of 155 HB, a tensile strength ≥ 375 MPa, and a yield strength ≥ 235 MPa;

[0040] 3. Introduce the annealed steel into the straightening unit for straightening. Ensure the straightness of the steel during straightening. The standard is that the local deviation relative to the straight line should be ≤ 0.4% within a length of 1000 mm;

[0041] 4. Introduce the straightened steel bar into a rotary grinding machine. The grinding machine uses a sand belt with a width of 100 mm, the sand belt running speed is 980 - 1000 revolutions per minute, and the forward speed of the steel core is 40 cm per minute. After the material is ground, it can effectively remove the oxide scale, the oil stain on the steel surface, and the scratches on the steel surface during the drawing process. After the material is fully ground, it enters the next process;

[0042] 5. The ground steel core enters the intermediate frequency heating device under atmosphere protection. The gas used for atmosphere protection is nitrogen. The heating device uses intermediate frequency heating, and the heating temperature is set at 420°C, and the actual temperature of the heated steel is 350°C. The atmosphere protection is to prevent the steel surface from being re-oxidized during the heating process and to remove the moisture (moisture) that may adhere to the steel surface.

[0043] 6. The heated material is introduced into the horizontal continuous casting machine. The horizontal continuous casting machine uses a power frequency furnace. When installing the mold, the central positions of the inlet and outlet molds are kept centered and horizontal at the same time. The connection between the crystallization mold and the mold uses a spindle connection method to keep the centering and levelness consistent with the mold. The inlet and outlet water ports of the mold are connected to cooling water, and the temperature of the cooling water is controlled by a fully automatic computer temperature control device. The water temperature range is set at 40°C, and the pressure is set at 0.55 MPa. The heating temperature of the furnace body is set at 480°C. The steel core enters the furnace body for continuous casting, and the continuous casting speed is 40 cm / minute. The product is drawn out from the outlet end of the horizontal continuous casting furnace body by a tractor and formed into a coil.

[0044] The surface zinc layer of each specification and thickness produced by this process is uniform, without eccentricity. The product is as Figure 3 shown, and the test results are shown in Table 1.

[0045] Table 1 Test Results

[0046]

[0047] Note: 900 - 1100 um is the normal and reasonable range, and the standard value should be 1000 um.

[0048] Comparative Example 1

[0049] The difference from Example 1 is only that: the grinding and rounding step is missing.

[0050] The steel core obtained without the grinding and rounding step is as Figures 4 - 5 shown. There are easily oil stains and slip marks on the material surface, which will damage the crystallization mold during the actual production of the product, resulting in eccentricity. The existence of oil stains reduces the bonding strength of the product, and there is a visible interface between the outer zinc layer and the steel core, causing the inner core to separate from the outer layer. There is a quality risk of the inner core separating from the outer zinc layer and eccentricity after the mold is damaged, scratches on the product appearance. At the same time, the outer diameter of the product will increase, as Figures 6 - 7 shown. The test results are shown in Table 2.

[0051] Table 2 Test Results

[0052]

[0053] Note: 900 - 1100um is the normal and reasonable range, and the standard value should be 1000um.

[0054] Comparative Example 2

[0055] The difference from Example 1 is only that: the preheating temperature of the steel core is set at 250°C.

[0056] The resulting product still has condensation delamination on the bonding surface and incomplete surface crystallization due to the too low temperature of the inner core, as Figures 8 - 9 shown.

[0057] Comparative Example 3

[0058] The difference from Example 1 is only that: the notch of the crystallization mold is threadedly connected to the mold base of the crystallizer.

[0059] During the threaded connection process, due to the easy wear of the graphite thread of the crystallization mold and the slight deviation of the thread misalignment in actual operation, the center position of the mold is inconsistent. Due to the inconsistent center position of the crystallization mold, the produced product is eccentric, as Figure 10 shown. The test results are shown in Table 3.

[0060] Table 3 Test Results

[0061]

[0062] Note: 900 - 1100um is the normal and reasonable range, and the standard value should be 1000um.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preventing eccentricity in continuous casting of solid-liquid bimetals, characterized in that: It includes the following steps: (1) After drawing, annealing, straightening and grinding and rounding the metal inner core, an inner core body is obtained; (2) After preheating, casting and crystallization of the inner core body, it is completed; The grinding and rounding step in the step (1) uses a grinding machine; the grinding machine is a circular wheel sand belt machine; the running speed of the circular wheel sand belt machine is coordinated with the advancing speed of the metal inner core; the running speed of the circular wheel sand belt machine is 800 - 1200 revolutions per minute, and the advancing speed of the metal inner core is 35 - 50 cm / min; The temperature of the preheating step in the step (2) is 50 - 100 °C lower than the crystallization temperature of the metal inner core; the preheating step uses a preheating barrel, and the preheating barrel uses medium or high frequency heating; In the casting step of the step (2), the central alignment of the furnace body inlet and the furnace body outlet is achieved; the furnace body uses industrial, medium or high frequency heating; In the crystallization step of the step (2), the crystallization mold and the crystallizer are connected in a shuttle shape; the temperature of the cooling water in the crystallization step of the step (2) is 35 - 45 °C; the internal pressure of the pipe in the crystallization step of the step (2) is 0.5 - 0.6 Mpa.

2. The solid-liquid bimetal continuous casting anti-eccentric production method according to claim 1, wherein: The difference between the inner diameter of the drawing die in the drawing step of the step (1) and the outer diameter of the metal inner core before drawing is 2 mm ± 5 μm.

3. The solid-liquid bimetal continuous casting anti-eccentric production method according to claim 1, characterized in that: The temperature of the annealing step in the step (1) is 550 - 700 °C, and the heat preservation time is 5 - 8 hours.

4. The solid-liquid bimetal continuous casting anti-eccentric production method according to claim 1, characterized in that: In the casting step of the step (2), the temperature of the clad metal melt is 30 - 100 °C higher than the melting point of the clad metal; the amount of each addition of the clad metal melt in the casting step of the step (2) is 5 - 10% of the clad metal melt in the furnace body.

5. Use of the method for preventing eccentricity in continuous casting of solid-liquid bimetal according to any one of claims 1-4, characterized in that: The application of the production method in the preparation of bimetallic round bar composite wire; the bimetallic round bar composite wire is one of copper-clad steel wire, zinc-clad steel wire or aluminum-clad copper wire.

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