Cooperative control method and equipment system based on direct current casting-warm rolling direct connection

Abstract

The invention relates to a cooperative control method and equipment system based on direct current casting-warm rolling direct connection, and belongs to the technical field of metal material machining. The system comprises a melting furnace, a standing furnace, a crystallizer, an electromagnetic stirrer, a four-roller warm rolling machine, a coiling furnace and other core units which are connected in sequence. The technological process comprises the key procedures of melt preparation, casting blank forming, online detection, warm rolling machining, heat treatment and the like. By innovatively adopting the electromagnetic stirring and direct current casting cooperative control technology and the continuous drawing and warm rolling integrated design, the technical problems of casting nozzle blockage and short service life in the traditional magnesium alloy continuous casting and rolling process are effectively solved, meanwhile, the secondary heating link is omitted, and the energy consumption and the production cost are remarkably reduced. The continuous and efficient production of the magnesium alloy plate can be realized, and the obtained product has the advantages of fine grains, uniform structure and the like, is suitable for processing and manufacturing of a plurality of series of magnesium alloys such as AZ, MB and the like, and has a good industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium alloy casting-rolling equipment and manufacturing technology, and particularly relates to a collaborative control method and equipment system based on direct current casting-warm rolling direct connection, which is particularly suitable for the efficient, energy-saving and continuous production of wrought magnesium alloy sheets. Background Art

[0002] Magnesium alloys exhibit broad application prospects in the fields of aerospace, automotive manufacturing, electronic communication, etc. due to their excellent lightweight performance. However, there are many bottleneck problems in the current continuous casting and rolling and slab rolling processes commonly used for magnesium alloy sheet production:

[0003] I. Key Technical Pain Points Currently Existed

[0004] The current continuous casting and rolling process of magnesium alloys has the following key technical pain points, which seriously restrict production efficiency, product quality and economic benefits:

[0005] 1. Nozzle clogging problem (core pain point)

[0006] Root cause:

[0007] The high activity of the magnesium alloy melt is prone to oxidation (generating MgO / Al2O3 inclusions)

[0008] When the solid fraction > 15%, dendritic fragments accumulate (especially for high-aluminum alloys such as AZ91)

[0009] Manifestation:

[0010] The nozzle life ≤ 50 hours (requiring frequent shutdowns for replacement)

[0011] The clogging failure rate > 15 times / year, and the single handling time ≥ 2 hours

[0012] The head and tail scrap rate of the strip increases by 8 - 12%

[0013] 2. High energy consumption for secondary heating

[0014] Defects of traditional process:

[0015] The slab needs to be reheated to 350 - 450 °C for rolling (energy consumption 600 - 800 kWh / ton)

[0016] Grain coarsening (50 - 100 μm) during the heating process leads to performance degradation

[0017] Economic impact:

[0018] Accounting for more than 30% of the total production cost

[0019] The carbon emission increases by 40 - 50%

[0020] 3. Bottleneck in wide-width production

[0021] Technical limitations:

[0022] The maximum width of twin-roll casting and rolling ≤ 800 mm (extrusion rolling ≤ 600 mm)

[0023] The incidence of edge cracks in wide-width plates (≥ 1200 mm) > 30%

[0024] Application constraints:

[0025] It is difficult to meet the integrated forming requirements of aerospace structural parts

[0026] 4. Poor tissue uniformity

[0027] Typical defects:

[0028] Center segregation (CV value of Al element ≥ 0.25)

[0029] Grain size gradient (surface 20 μm vs core 50 μm)

[0030] Anisotropy (Δr value > 1.5)

[0031] Performance impact:

[0032] The elongation fluctuation reaches ± 15%

[0033] The fatigue life is reduced by 30 - 40%

[0034] 5. Difficult to control surface quality

[0035] Problem manifestations:

[0036] The thickness of oxide scale ≥ 10 μm (pickling treatment is required in traditional process)

[0037] Roll surface sticking with magnesium results in stripe defects (incidence > 5%)

[0038] Consequences:

[0039] Increase the polishing / pickling process (cost increases by ￥500 - 800 / ton)

[0040] Limit high-end applications (such as 3C product appearance parts)

[0041] 6. Insufficient process continuity

[0042] System short board:

[0043] The matching accuracy of casting / rolling speed is poor (synchronization error > 0.1 m / min)

[0044] The temperature drop fluctuation is large (casting and rolling interval > 20℃)

[0045] The response delay of on-line detection ≥ 5 seconds

[0046] 7. Equipment reliability issues

[0047] Pain points of key equipment:

[0048] The service life of the crystallizer copper sleeve ≤ 3 months (thermal stress cracks)

[0049] The peeling period of the roll surface < 2000 tons

[0050] The consumption of protective gas > 15 m 3 / ton

[0051] Industry impact analysis

[0052]

[0053] Technical breakthrough directions

[0054] No-casting-nozzle technology: Develop a direct-current casting - warm rolling direct connection system (such as the present invention)

[0055] Waste heat utilization: The latent heat of solidification is directly used for warm rolling (eliminating secondary heating)

[0056] Multi-field regulation: Electromagnetic stirring + supernormal cooling cooperate to refine the microstructure

[0057] Intelligent control: Machine learning is used to optimize process parameters in real time

[0058] These pain points are exactly the key research and development directions in the current magnesium alloy processing field, and also the core solution targets of the technical solution of the present invention. II. Technical pain points of the magnesium alloy billet rolling process

[0059] The technical pain points of the magnesium alloy billet rolling process mainly focus on the following aspects, which directly affect product quality, production efficiency and cost control:

[0060] 1. Initial quality defects of billets

[0061] Macroscopic segregation

[0062] Segregation of AI / Mn elements at the center line of the billet (CV value ≥ 0.3)

[0063] Interdendritic shrinkage porosity (porosity > 2%)

[0064] Microstructure problems

[0065] Coarse columnar crystals (diameter 50 - 200 μm)

[0066] Second phase (such as β-Mg 17 Al 12 ) network distribution

[0067] Influence: Edge cracks and delamination are likely to occur during rolling, and a milling process needs to be added (material loss ≥ 5%)

[0068] 2. Secondary heating process defects

[0069] High energy consumption

[0070] Soaking energy consumption is 600 - 800 kWh / ton (accounting for 40% of the total process energy consumption)

[0071] Oxidation loss rate of the heating furnace is 1.5 - 3%

[0072] Microstructure deterioration

[0073] Abnormal grain growth (grain size reaches 100 - 150 μm after holding at 400°C for 2 h)

[0074] Surface oxide layer thickness ≥ 20 μm

[0075] Case: The elongation of AZ31 billet decreases by 15 - 20% after secondary heating

[0076] 3. Difficulties in hot rolling process control

[0077]

[0078] 4. Limitations of rolling equipment

[0079] Width bottleneck

[0080] The maximum rolling width of traditional hot rolling mills ≤ 1500 mm

[0081] Edge speed reduction during wide-width rolling leads to uneven properties (Δσ0.2 ≥ 30 MPa)

[0082] Insufficient precision

[0083] Flatness control precision > 1 mm / m (automobile sheet requires ≤ 0.5 mm / m)

[0084] Thickness tolerance ± 0.15 mm (high-end requirement ± 0.05 mm)

[0085] 5. Poor process connection

[0086] Uncontrollable temperature drop

[0087] Temperature drop during the transfer process from billet to rolling mill > 50°C (the target should be < 20°C)

[0088] Resulting in a 15 - 20% increase in rolling force

[0089] Speed mismatch

[0090] The continuous casting speed (1 - 1.5 m / min) and the rolling speed (2 - 3 m / min) are difficult to synchronize

[0091] 6. Difficulties in rolling special alloys

[0092] High-strength magnesium alloy (such as ZK60)

[0093] Narrow thermal processing window (300-350°C)

[0094] The pass reduction should be less than 15% (AZ31 can reach 30%)

[0095] Ultra-thin plate (<1mm)

[0096] Rolling more than 10 times, grain size unevenness> 40%

[0097] Industry solution path

[0098] Casting and rolling integration

[0099] Developed direct rolling process (eliminating secondary heating)

[0100] As the direct-current casting-warm rolling technology of the present invention

[0101] Organizational Regulation

[0102] Electromagnetic stirring of casting (grain refinement to below 20μm)

[0103] Multi-pass warm rolling + intermittent annealing

[0104] Intelligent rolling

[0105] Machine learning predicts rolling force (error < 5%)

[0106] Laser thickness gauge closed-loop control (response time <0.1s)

[0107] Surface treatment

[0108] Online plasma cleaning (instead of pickling)

[0109] Nano-ceramic coating roller (lifespan increased by 3 times)

[0110] These pain points need to be solved through collaborative innovation of technology, equipment and materials, and breakthroughs in widening, shortening processes and intelligence are the current main directions of technological development. Summary of the Invention

[0111] 1. Purpose of the Invention

[0112] This paper addresses the three major technical bottlenecks in the existing magnesium alloy sheet production process: high nozzle blockage rate (>0.1 times / 1,000 tons), high secondary heating energy consumption (≥600kWh / ton), and low yield rate (≤75%). A collaborative control method and equipment system based on direct DC casting and warm rolling is proposed to achieve the following technical goals:

[0113] Breakthrough in process continuity

[0114] By constructing a coupled system of melt solidification in the crystallizer - ingot traction - online warm rolling, the dependence of the traditional continuous casting and rolling process on the casting nozzle is eliminated, the frequency of production interruption is reduced to <0.01 times / thousand tons, and a single continuous operation time of ≥240 hours is achieved.

[0115] Structural optimization of energy consumption

[0116] Utilize the residual heat of solidification of the ingot (350-400℃) to directly carry out warm rolling, eliminating the secondary heating step, and reducing the energy consumption per unit product to <

[0117] 300kWh / ton (reduced by more than 60% compared with traditional processes).

[0118] Improved production efficiency

[0119] Through the coordinated control of electromagnetic stirring, gradient cooling and rolling deformation, the following are achieved:

[0120] Yield rate ≥90% (20% higher than traditional process)

[0121] Production cycle <2 hours (shortened by more than 90%)

[0122] The width of the plate has been increased to ≥1500mm (meeting the requirements of wide-width parts for aerospace)

[0123] Enhanced application scalability

[0124] Applicable to AZ / AM / ZK series magnesium alloys, making the plate:

[0125] Room temperature elongation increased to ≥18% (traditional process ≤12%)

[0126] Anisotropy index Δr≤0.5 (traditional ≥1.2)

[0127] Surface treatment-free, directly reaching Ra≤1.6μm

[0128] 2. Technical Solution

[0129] To achieve the above-mentioned purpose, the present invention provides a magnesium alloy DC casting-warm rolling direct production system and control method, the innovative technical features of which are as follows:

[0130] (1) Integrated production system

[0131]

[0132]

[0133]

[0134] like Figure 1As shown, the system successively includes along the transmission direction of the magnesium alloy plate (29):

[0135] Melting unit: composed of a melting furnace (2) and a ladle transfer pipe (6), and a ceramic foam filter with 40 - 60 ppi is built in the ladle transfer pipe;

[0136] Melt treatment unit: including a holding and static furnace (8), a reflux pipe (9), and a melt distribution tundish (21), with the liquid level control accuracy of the tundish being ±2 mm;

[0137] Casting unit: composed of a mold (20), an electromagnetic stirrer (17), and a water spray ring (24);

[0138] Warm rolling unit: including a four - high warm rolling mill (26) and a coiling furnace (28), and the surface roughness Ra of the working roll of the rolling mill is ≤0.2 μm;

[0139] Detection unit: configured with an infrared thermometer (25) and an on - line eddy current flaw detector (27), and the detection frequency is ≥100 Hz;

[0140] Protection system: equipped with a protective gas distribution ring (15) and an inert protective gas injector (14), and the gas purity is ≥99.99%;

[0141] (II) Technical characteristics of core components

[0142] Mold assembly

[0143] Structural characteristics:

[0144] (1) The three - dimensional size is 1600 mm (width) × 1200 mm (height) × (20 ± 0.1) mm (cavity thickness);

[0145] (2) Inner cavity fillet gradient design: in the upper 600 mm area, R50 → in the middle 400 mm area, a gradual change from R50 - R30 → in the lower 200 mm area, R15;

[0146] (3) Composite wall structure: from the inside to the outside, it is successively:

[0147] Copper alloy inner wall (CuCrZr, hardness HRB75 - 80, thickness 28 ± 0.5 mm)

[0148] Chromium plating layer (thickness 20 - 30 μm, Ra ≤ 0.8 μm)

[0149] Spiral cooling water channel (cross - sectional area 15 × 15 mm 2 , machining accuracy ±0.1 mm)

[0150] Steel shell (45# steel, thickness 45 ± 1 mm)

[0151] Electromagnetic stirring system

[0152] Structural parameters:

[0153] (1) 4-pole rotating magnetic field design, installed 400 - 600 mm below the liquid surface;

[0154] (2) The coil is made of H-class insulated copper pipe, and the cooling water flow rate is 2 - 5 L / min;

[0155] Control parameters:

[0156] (1) Working mode:

[0157] Low-frequency mode (15 - 25 Hz): for alloys with w(AI) ≥ 6%

[0158] High-frequency mode (30 - 50 Hz): for the working condition of slab thickness ≤ 15 mm

[0159] (2) Alternate stirring: forward rotation for 30 s → stop for 5 s → reverse rotation for 30 s, magnetic induction intensity 0.05 - 0.15 T

[0160] Gradient cooling system

[0161] Zone control:[[ID=X]] [[ID=X]]

[0162] [[ID=X]] [[ID=X]] [[ID=X]]

[0163] Control accuracy: flow rate ± 0.5 m 3 / h, temperature ± 1 °C

[0164] (3) Process control logic

[0165] When the infrared thermometer (25) detects that the surface temperature of the slab enters the warm rolling window of 350 - 400 °C, the PLC system is automatically triggered:

[0166] 1. The billet feeding speed is adjusted to 0.8 - 1.5 m / min;

[0167] 2. The rolling force is controlled at 50 - 150 MPa:

[0168] 3. The coiling tension is maintained at 5 - 10 kN.

[0169] (4) DC casting direct warm rolling process

[0170] This process realizes integrated casting and rolling production through the following steps. The technical characteristics and control logic of each step are as follows:

[0171] 1. Melting preparation and pouring control Note: There seem to be some consecutive tags with the same ID (from ID=X) in the original text which might be an error. I've left them as they are in the translation for consistency with the original.

[0172] Melting stage:

[0173] (1) In the melting furnace (2), under the dual protection of inert gas and covering agent, heat the magnesium alloy raw materials to 700 - 750 °C, and control the melt hydrogen content to ≤ 1.5 mL / 100 g;

[0174] (2) The melt is transported through the transfer pipe (6), and a ceramic foam filter (3) with 40 - 60 ppi is installed inside the pipe, and the filtration flow rate is ≤ 0.8 m / s;

[0175] (3) Stand still in the holding furnace (8) for 10 - 15 min, and the temperature fluctuation is ≤ ±5 °C.

[0176] Pouring stage:

[0177] (1) Control the tundish (21) liquid level at 300 ± 2 mm, and the pouring temperature at 680 ± 10 °C;

[0178] (2) Use a pneumatic slide valve to control the flow rate, and the opening is linked with the casting speed (proportional coefficient 0.8 - 1.2);

[0179] (3) The protective gas system maintains the oxygen content in the pouring area < 50 ppm (Ar + CO2 mixed gas, ratio 7:3).

[0180] 2. Control of slab forming (key process parameters)

[0181]

[0182]

[0183] 3. On-line detection and dynamic regulation

[0184] Temperature closed-loop control:

[0185] (1) The infrared thermometer (5) monitors the surface temperature of the slab in real time (sampling frequency 100 Hz);

[0186] (2) The PLC adjusts according to the temperature deviation ΔT:

[0187] ΔT > 10 °C: Step regulation of the cooling water flow rate (±2 m 3 / h)

[0188] ΔT ≤ 10 °C: PID continuous regulation (±0.5 m 3 / h)

[0189] Defect detection:

[0190] Use a 5MHz ultrasonic flaw detector (4), with a detection sensitivity of Φ1mm flat-bottomed hole, and the scanning speed is synchronized with the casting speed. 4. Warm rolling processing technology (multi-pass collaborative control)

[0191]

[0192] 5. Post-treatment process

[0193] Coiling control:

[0194] (1) Tension control: 8 - 12N / mm 2 , the radial runout of the coiler drum ≤ 0.1mm;

[0195] (2) Coiling temperature: 200 - 250°C, with mica paper (thickness 0.05mm) placed between layers.

[0196] Annealing process:

[0197]

[0198] IV. Equipment collaborative control logic

[0199] Temperature - speed coupling control

[0200] When the temperature detected by the infrared thermometer exceeds the set range, the PLC synchronously adjusts:

[0201] Casting speed (±0.1m / min)

[0202] Cooling water flow rate (±0.5m 3 / h)

[0203] Electromagnetic stirring power (±2kW)

[0204] Multi-stand speed matching

[0205]

[0206] Gas protection linkage

[0207] When the pouring flow rate > 50kg / min, the air curtain spraying flow rate is automatically increased to 8L / min;

[0208] System leakage detection (alarm when the pressure difference > 5kPa).

[0209] The present invention has the following beneficial effects compared with the prior art:

[0210] Process innovation

[0211] Through the direct coupling of direct current casting and warm rolling, a dummy bar with a dovetail groove structure is set at the bottom of the mold to achieve melt plugging. Utilizing the synergistic cooling effect of the spray cooling on the outer wall of the mold and the dummy bar, the melt flowing to the bottom of the mold is rapidly solidified and forms a mechanical interlocking structure with the dovetail groove of the dummy bar. Through the traction of the coiler, the continuously drawn all-solid billet directly enters the warm rolling process, fundamentally solving the technical problem of nozzle blockage in the traditional magnesium alloy continuous casting and rolling process (the blockage rate is reduced to <0.1 times per thousand tons).

[0212] Solidification control optimization

[0213] Adopt the synergistic regulation mechanism of electromagnetic stirring and gradient cooling in the upper part of the mold, where:

[0214] Electromagnetic stirring parameters: frequency 20 - 50Hz, magnetic induction intensity 0.05 - 0.15T

[0215] Gradient cooling partition: the cooling intensity ratio of the upper / middle / lower parts is 1:3:2

[0216] Refine the grain size of the billet to 10 - 15μm (40 - 50% lower than the traditional process), and the solute segregation coefficient (CV value)

[0217] ≤0.15

[0218] Process integration advantages

[0219] Build an "solidification - traction - warm rolling" integrated production line to achieve:

[0220] Process reduction: Cancel the secondary heating link

[0221] Energy consumption reduction: <300kWh / ton (60% lower than the traditional process)

[0222] Yield improvement: ≥90% (traditional process ≤80%)

[0223] Production cycle: <2 hours (traditional 24 - 48 hours)

[0224] Performance improvement effect

[0225] Mechanical properties: Tensile strength is increased by 15 - 20% (the contribution rate of warm rolling recrystallization is ≥70%)

[0226] Quality index: The inclusion removal rate is increased by 30%, and the sheet thickness tolerance is controlled within ±0.1mm

[0227] Surface quality: Ra ≤1.6μm (pickling - free treatment)

[0228] Advancement of equipment control

[0229] Temperature control: Multi - sensor fusion achieves an accuracy of ±3°C

[0230] Rolling system: The unit rolling force of the four-high rolling mill is ≥ 150 MPa, and the flatness control accuracy is 0.5 mm / m

[0231] Process stability: The temperature drop in the solidification-rolling interval is < 8 °C, and the cross-sectional temperature difference is < 15 °C

[0232] Application scalability

[0233] Applicable to series of magnesium alloys such as AZ31 / AM60, breakthrough achievements:

[0234] Wide-width sheet: ≥ 1600 mm (traditional process ≤ 800 mm)

[0235] Application benefits: The weight of aerospace components is reduced by 30%, and the stamping formability of 3C products is improved by 40% Brief description of the drawings

[0236] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0237] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention disclosure in any way. Additionally, the shapes and proportional dimensions of the components in the drawings are only schematic and are used to assist in understanding the present invention, rather than specifically defining the shapes and proportional dimensions of the components of the present invention. Those skilled in the art can, under the teachings of the present invention, select various possible shapes and proportional dimensions according to specific circumstances to implement the present invention.

[0238] Figure 1 It is a schematic side view structure diagram of the direct current casting-hot rolling integrated production system of the present invention (Embodiment 1);

[0239] Figure 2 For Figure 1 A partial enlarged schematic side view structure diagram of the crystallizer (20) region in, showing the cooperative structure of gradient cooling and electromagnetic stirring;

[0240] Figure 3 For Figure 1 A schematic side view cross-sectional structure diagram of the working area of the four-high hot rolling mill (26) in, showing the rolling force transmission and temperature field distribution;

[0241] Figure 4 It is a process flow diagram of the direct current casting-hot rolling integrated production process (process parameters correspond to Embodiment 2).

[0242] List of unified reference numerals

[0243]

[0244]

[0245] Specific Embodiments

[0246] The technical solution of the present invention will be described in detail below in combination with embodiments and the accompanying drawings. It should be particularly noted that:

[0247] The embodiments are only used to illustrate the technical principle and core innovation points of the present invention, and do not constitute a limitation on the protection scope;

[0248] Those skilled in the art can make equivalent transformations or parameter adjustments to the following embodiments within the scope defined by the claims.

[0249] Embodiment Description Specification Brief Description of the Drawings

[0251] The drawings are simplified schematic diagrams, omitting structures not directly related to the inventive points (such as brackets, fasteners, etc.);

[0252] The proportional relationship is not the actual size ratio, and the key components are shown with partial enlarged views to display the feature details;

[0253] The same reference numerals represent the same technical features, and different reference numerals represent embodiments with structural or parameter variations.

[0254] Definition of Orientation Terms

[0255] Based on the attached Figure 1 The coordinate system shown is defined as follows:

[0256] ″Up / Down″: Along the casting direction (Z-axis), the moving direction of the dummy bar is ″down″;

[0257] ″Front / Back″: Along the rolling direction (X-axis), the feeding direction of the rolling mill is ″front″;

[0258] ″Left / Right″: Along the width direction of the plate (Y-axis).

[0259] Embodiment Options

[0260] It can be implemented by, but not limited to, the following methods:

[0261] Parameter combination: Embodiment 1 (AZ31 alloy) + Embodiment 2 (electromagnetic stirring mode B);

[0262] Structure replacement: The rounding design of the mold can adopt Embodiment A (gradual change type) or Embodiment B (step type);

[0263] Process adjustment: Gradient cooling can use water cooling (Example 3) or aerosol cooling (Example 4).

[0264] Technical feature explanation

[0265] Omission statement

[0266] Conventional technical features not shown in the drawings include:

[0267] The waste gas treatment system of the melting furnace;

[0268] The hydraulic balance device of the rolling mill;

[0269] The purification equipment of the protective gas.

[0270] Measurement reference

[0271] All process parameters are measured under the following conditions:

[0272] Temperature: Measured by a K-type thermocouple at a position 10 mm from the surface of the continuous casting billet;

[0273] Dimensions: Measured by a laser rangefinder (accuracy ±0.01 mm) at room temperature;

[0274] Mechanical properties: Sampled and tested according to ASTM E8 standard.

[0275] Change description

[0276] Without departing from the technical solution defined in the claims, the following changes can be made:

[0277] Material substitution: The inner wall of CuCrZr can be replaced with CuCoBe alloy;

[0278] Parameter expansion: The electromagnetic stirring frequency can be expanded to 10 - 60 Hz;

[0279] Structural equivalence: The dovetail groove can be replaced with a T-shaped groove structure (the depth ratio needs to be maintained ≥0.6).

[0280] Example 1 (rolling of 20 mm → 8 mm deformed magnesium alloy sheet)

[0281] 1. Continuous casting billet preparation

[0282] (1) Preheat the leading strip to 250 - 300 °C and insert it into the bottom of the mold, ensuring that the biting depth of the dovetail groove and the solidifying magnesium alloy is ≥50 mm.

[0283] (2) Inject the magnesium alloy melt at 680 - 720 °C into the mold through a 40 ppi ceramic filter transfer pipe (flow rate 1.2 - 1.5 m 3 / h).

[0284] (3) Apply electromagnetic stirring in the upper 1 / 3 area of the mold (parameters: 25 Hz / 0.12 T, intermittent period 30 s) to refine the grains.

[0285] (4) Zone cooling control:

[0286] Upper part: 5 m 3 / h (25 °C) weak cooling

[0287] Middle part: 20 m 3 / h (15 °C) strong cooling

[0288] Lower part: 10 m 3 / h (18 °C) medium cooling

[0289] Ensure that the magnesium alloy in the lower part of the mold is completely solid.

[0290] 2. Warm rolling process

[0291]

[0292] 3. Post-treatment

[0293] Coiling: 280 - 300 °C / 10 - 15 N / mm 2 Tension

[0294] Annealing: Gradually heat up to 400 °C, hold for 2 h, and then cool in the furnace

[0295] Example 2 (Precision rolling of AZ31B 20 mm → 5 mm magnesium alloy)

[0296] 1. Raw material treatment

[0297] AZ31B magnesium alloy ingot (composition: Al 2.5 - 3.5 wt%, Zn 0.7 - 1.3 wt%, Mn 0.2 - 1.0 wt%) under a CO2 + SF6 protective atmosphere:

[0298] Melting temperature: 720 ± 5 °C

[0299] Transfer liquid conditions: Φ150 mm / 50 ppi filter screen → 650 °C heat preservation and static furnace

[0300] 2. Cast billet forming

[0301] Mold parameters: 1400 mm (width) × 20 mm (thickness) × 1000 mm (height)

[0302] Cavity gradual change fillet: Upper part R60 → Middle part R35 → Lower part R15

[0303] Cooling system:

[0304] Upper part: 6 m 3 / h (28 °C)

[0305] Lower part: 22 m 3 / h (12 °C)

[0306] Electromagnetic stirring: 30 Hz / 0.1 T (42 kW)

[0307] Casting speed: Initial 0.8 m / min → Stable 1.2 m / min (Surface temperature gradient ≤ 15 °C / m)

[0308] 3. Warm rolling process

[0309]

[0310] 4. Key control

[0311] Temperature monitoring: Two-color infrared thermometer (Accuracy ±1.5 °C)

[0312] Temperature drop compensation: Induction heating (≤5 °C / s)

[0313] Recrystallization control: ≥100 s between passes

[0314] Grain size: ASTM grade 12 - 13 (6 - 8 μm)

[0315] 5. Post-treatment

[0316] Coiling: 290 ± 10 °C / 12 ± 1 N / mm 2 Tension (Coil diameter of Φ1500 mm)

[0317] Annealing: Stepwise heating from 300 °C to 400 °C + 120 min holding

[0318] Example 3 (Rolling of 20 mm → 6 mm MB1 magnesium alloy sheet)

[0319] 1. Raw material treatment

[0320] Alloy composition: MB1 magnesium alloy (Mn 1.3 - 2.0 wt%, Fe ≤ 0.05 wt%, Si ≤ 0.10 wt%)

[0321] Melting process:

[0322] Heat to 700 ± 10 °C for melting under CO2 + 0.5% SF6 protective atmosphere

[0323] Transfer through a Φ120 mm, 60 ppi ceramic filter screen to a 660 °C holding and static furnace

[0324] Melt pouring temperature 680 - 700 °C

[0325] 2. Ingot preparation

[0326] Mold parameters:

[0327] Dimensions: 1200 mm (width) × 20 mm (thickness) × 800 mm (height)

[0328] Cavity fillet gradient: upper part R50 → middle part R30 → lower part R10 (optimize stress distribution)

[0329] Cooling control:

[0330] Upper part: 5 m 3 / h (26 °C) weak cooling (reduce the risk of hot cracks)

[0331] Middle part: 18 m 3 / h (16 °C) strong cooling (promote columnar crystal growth)

[0332] Lower part: 12 m 3 / h (18 °C) medium cooling (ensure complete solidification)

[0333] Electromagnetic stirring:

[0334] Apply 20 Hz / 0.15 T (power 35 kW) in the upper 1 / 3 area, intermittent mode (on for 30 s / off for 20 s) Casting speed:

[0335] Initial 0.7 m / min, increased to 1.0 m / min after stabilization

[0336] Surface temperature gradient control ≤ 12 °C / m

[0337] 3. Warm rolling process (four-pass rolling)

[0338]

[0339] Process key points:

[0340] Temperature control:

[0341] Install a two-color infrared thermometer at the mill inlet (accuracy ±1 °C)

[0342] Use induction heating compensation between passes (temperature drop ≤ 4 °C / s)

[0343] Recrystallization control:

[0344] Residence time between passes ≥ 80 s (ensure the completion of dynamic recrystallization)

[0345] Target grain size ASTM 11 - 12 (8 - 10 μm)

[0346] Deformation distribution:

[0347] Large deformation (30%) in the first two passes to break the as-cast structure, and gradually reduce the deformation in the last two passes

[0348] 4. Post-treatment

[0349] Coiling:

[0350] Temperature 270 ± 10°C, tension 8 - 10 N / mm 2 (Prevent sheet warping)

[0351] Coil diameter Φ1200 mm (matched with the charging size of the subsequent annealing furnace)

[0352] Annealing:

[0353] Stepwise temperature rise: 250°C (1 h) → 350°C (1 h) → 400°C (2 h)

[0354] Cool in the furnace to 150°C and then air-cool (to eliminate residual stress)

[0355] 5. Quality control indicators

[0356]

[0357] Process advantages:

[0358] Balance work hardening and recrystallization through four-pass progressive rolling to avoid edge cracks

[0359] Low-temperature finish rolling (330 - 350°C) inhibits excessive grain growth, taking into account both strength and plasticity

[0360] Stepwise annealing optimizes the texture and improves the deep drawing performance of MB1 alloy (Note: MB1 is a low-alloyed magnesium alloy, and the Mn content and Fe / Si impurities need to be strictly controlled to ensure rolling plasticity)

[0361] Example 4 (Rolling of 20 mm → 4 mm wide AZ91D magnesium alloy sheet)

[0362] 1. Raw material pretreatment

[0363] Alloy composition: AZ91D magnesium alloy (AI 8.3 - 9.7 wt%, Zn 0.35 - 1.0 wt%, Mn 0.15 - 0.5 wt%) Melting control:

[0364] Adopt double-layer protective gas (bottom layer CO2 + 0.8% SF6, liquid surface layer Ar + 2% SF6)

[0365] Melting temperature 720 ± 5°C, holding temperature of the static furnace 690 ± 5°C for 20 min

[0366] The transfer pipe is equipped with a 60 ppi gradient ceramic filter (50 ppi at the inlet → 70 ppi at the outlet)

[0367] 2. Preparation of wide-width billet

[0368] Mold system:

[0369] Cavity size: 1600 mm (width) × 20 mm (thickness) × 1200 mm (height)

[0370] Round corner design:

[0371] Upper 500 mm: R60 round corner (to inhibit hot cracks)

[0372] Middle 500 mm: Gradual change from R60 to R25 (to control the proportion of columnar crystals)

[0373] Lower 200 mm: R10 round corner (to ensure complete solidification)

[0374] Cooling regime:

[0375] Upper part: 8 m 3 / h (28 °C) weak cooling

[0376] Middle part: 25 m 3 / h (14 °C) strong cooling

[0377] Lower part: 15 m 3 / h (16 °C) medium cooling

[0378] Electromagnetic stirring:

[0379] Adopt dual-frequency mode (fundamental frequency 25 Hz + harmonic 50 Hz)

[0380] Magnetic induction intensity 0.18 T (20% higher than conventional)

[0381] Power density 42 kW / m 2 (Optimized for high Al content)

[0382] 3. Five-pass warm rolling process

[0383]

[0384] Key technical measures:

[0385] Deformation distribution:

[0386] In the first 3 passes, use 30% large deformation to break coarse β-Mg 17 Al 12 phase

[0387] In the last 2 passes, gradually reduce the deformation (≤26.5%) to control the texture development

[0388] Temperature strategy:

[0389] Adopt reverse temperature rise (300 °C → 360 °C) to compensate for work hardening

[0390] Insert induction heating after the fourth pass (heating rate: 8 °C / s)

[0391] Width control:

[0392] Configure a hydraulic AGC system (control accuracy: ±0.03 mm)

[0393] The work roll adopts four-segment crown adjustment (compensation amount: 0 - 0.15 mm)

[0394] 4. Post-treatment process

[0395] Tension coiling:

[0396] Temperature: 280 ± 5 °C, tension gradient control:

[0397] Leading end: 12 N / mm 2 → Middle of the strip: 10 N / mm 2 → Tail end of the strip: 8 N / mm 2

[0398] Immediately sleeve with a heat shrinkable film after coiling (to prevent oxidation)

[0399] Multi-stage annealing:

[0400] First stage: 250 °C × 1 h (to eliminate rolling stress)

[0401] Second stage: 320 °C × 2 h (β-phase spheroidization)

[0402] Third stage: 400 °C × 1 h (complete recrystallization)

[0403] Fourth stage: 280 °C × 4 h (slow cooling to control precipitation)

[0404] 5. Performance indicators

[0405]

[0406] Innovation points of the process:

[0407] 1. Aiming at the high-Al characteristics of AZ91D:

[0408] Optimize the electromagnetic stirring frequency combination to inhibit β-phase segregation

[0409] Adopt reverse temperature rise rolling to delay work hardening

[0410] 2. Wide-width flatness control:

[0411] Develop a four-segment roll profile adjustment technology

[0412] Innovate the tension gradient coiling scheme

[0413] 3. In terms of post-treatment:

[0414] Design a four-stage annealing system to balance strength and formability

[0415] Heat shrink film packaging solves the oxidation problem of high-Al alloys (Note: This embodiment is particularly applicable to the production of wide-width magnesium alloy housing parts for automobiles, and the yield rate can reach over 92%).

[0416] Legal statement and implementation instructions

[0417] Citation of reference documents

[0418] All patent documents and non-patent documents cited in this specification are incorporated herein by reference in their entirety as if fully set forth. The cited documents include, but are not limited to:

[0419] Chinese invention patent CN106975660A (A magnesium alloy continuous casting and rolling device and a magnesium alloy continuous casting and rolling method)

[0420] "Light Metal Processing Technology" (2023 edition), Section 2, Chapter 5

[0421] ASTM B107 / B107M-21 Standard Specification

[0422] Rules for interpreting technical features

[0423] (1) The term "comprising / including" means containing at least the recited element and allowing the presence of other elements not expressly recited that do not change the essential characteristics of the invention;

[0424] (2) The term "consisting essentially of" is limited to including the recited essential technical features and non-essential features that do not substantially affect the inventiveness of the invention;

[0425] (3) The term "may" indicates an optional technical feature, the presence or absence of which does not affect the integrity of the technical solution.

[0426] Implementation modes of technical solutions

[0427] Integration and decomposition: Any of the said devices can be implemented as an independent device or integrated with other devices to form a production line system;

[0428] Quantitative relationship: The said "one / kind" element can be extended to a combination of multiple similar elements (such as multiple crystallizers in parallel);

[0429] Association of embodiments: The different parts of each embodiment are described separately, and for the same technical features, refer to the detailed description of Embodiment 1.

[0430] Statement of the scope of protection The scope of protection of this invention is subject to the claims. Without departing from the core technical innovation points of this invention:

[0431] Material substitution (such as CuCrZr → CuCoBe alloy);

[0432] Parameter adjustment (such as a ±10% fluctuation in electromagnetic stirring frequency);

[0433] Structural equivalent transformation (such as dovetail groove → T-shaped groove)

[0434] All of these shall be regarded as falling within the protection scope of the present invention.

[0435] The technical boundary states that the following situations are not regarded as substantial changes to the present invention:

[0436] Industry standard adaptation adjustment of conventional process parameters;

[0437] Equivalent replacement of detection equipment (such as infrared temperature measurement → thermocouple temperature measurement);

[0438] Conventional proportional changes in the composition of the protective gas.

Claims

1. A collaborative control method and equipment system based on direct connection of DC casting and warm rolling, characterized in that, Including those arranged in sequence along the production path: melting furnace (2), ladle transfer pipe (6), holding and staticizing furnace (8), reflux pipe (9), molten metal distribution tundish (21), mold (20), dummy bar head (23), water spray ring (24), infrared thermometer (25), online flaw detector (27), four-high hot rolling mill (26) and coiling furnace (28); the mold (20) is of a flat rectangular box structure, with the cavity size of 1200 mm (width) × 1000 mm (height) × 20 mm (thickness), and the fillets in the cavity change in a gradient manner: the upper 400 mm area has a fillet radius of R50, the middle 400 mm area has a gradual transition from R50 to R30, and the lower 200 mm area has a fillet radius of R15; the wall layer structure of the mold (20) from the inside to the outside includes: Cu-Cr-Zr alloy inner wall (thickness 28 ± 0.5 mm, surface chromium plating layer 20 - 30 μm), cooling water tank (width 15 ± 0.2 mm, machining accuracy ± 0.1 mm), steel shell (thickness 45 ± 1 mm); the device also includes: an electromagnetic stirrer (17) installed at the upper 1 / 3 liquid cavity height of the mold (20), which is a rotating magnetic field type 4-pole structure, and the working parameters meet: frequency 15 - 50 Hz, magnetic induction intensity 0.05 - 0.15 T, power 20 - 50 kW, positive and negative rotation alternating period 30 s; a protective gas system, including a protective gas distribution ring (15) and an inert protective gas injector (14), and a protector nozzle (5) for maintaining the O2 content < 50 ppm.

2. The device according to claim 1, wherein The ladle transfer pipe (6) is internally provided with a ceramic filter screen (3) with 40 - 60 ppi, and the filter screen pore size is distributed in a gradient manner, with the inlet end being 40 ppi and the outlet end being 60 ppi.

3. A direct warm rolling process for magnesium alloy sheets by direct current casting based on the device described in claim 1, characterized in that, Including the following steps: (1) Melting preparation: Under the protection of inert gas, melt the magnesium alloy at 700 - 750 °C, and flow it into the holding and static furnace (21) at 680 + 10 °C through the transfer pipe (6). After standing for 10 - 15 minutes, pour it into the mold; (2) Cast billet forming: Start the mold electromagnetic stirrer (17), parameters: for high Al content alloys, use the low-frequency mode of 15 - 25 Hz, and for thin-specification cast billets, use the high-frequency mode of 30 - 50 Hz; Segmented cooling control: Upper molten zone of the mold: 25 - 30 °C / 5 - 8 m 3 / h weak cooling, middle semi-solid zone: 10 - 15 °C / 15 - 20 m 3 / h strong cooling, lower fully solid zone: 18 - 23 °C / 10 - 15 m 3 / h medium cooling; Drawing speed 0.8 - 1.5 m / min, realizing the mechanical bite between the magnesium alloy and the dummy bar (23) through the dovetail groove of the dummy bar; (3) On-line regulation: The infrared thermometer (25) monitors the temperature in real time (accuracy ±3 °C), linkage regulation: Cooling water flow rate (±0.5 m 3 / h), drawing speed (±0.1 m / min), electromagnetic stirring power (±2 kW); (4) Warm rolling process: First pass: 20 mm → 15 mm (deformation rate 25%) at 320 - 350 °C, rolling speed 1.0 - 1.2 m / min; Second pass: 15 mm → 11 mm (deformation rate 26.7%) at 340 - 360 °C, and after rolling, supplement the temperature to 350 ± 10 °C; Third pass: 11 mm → 8 mm (deformation rate 27.3%) at 330 - 350 °C; (5) Post-treatment: Coiling tension 8 - 12 N / mm 2 , Step annealing: 350 °C (10 °C / min) → 400 °C (5 °C / min, hold for 2 h) → Furnace cool to 150 °C.

4. The process according to claim 3, characterized in that, The temperature regulation realizes three-closed-loop control through the PLC: infrared temperature measurement signal → cooling water regulating valve, temperature deviation → electromagnetic stirring power compensation, rolling force feedback → inter-pass temperature correction.

5. The process according to claim 3, characterized in that, The speed synchronization system meets: the matching relationship of the casting speed V1 of the mold, the rolling speed V2 of the rolling mill, and the coiling speed V3 is: |V1 - V2| ≤ 0.03 m / min, |V2 - V3| ≤ 0.05 m / min.

6. The process according to claim 3, characterized in that, The partitioned gas supply parameters of the protective gas system are: melting area: 8 L / min (CO2 + 0.3% SF6), mold liquid level: 5 L / min (Ar + 1% SF6), rolling area: 3 L / min (pure N2).

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