Stability Control of Induction Furnaces in Casting of Automotive Engine Blocks

In the automotive industry, the casting of engine blocks (обычно HT250/GJL-250 или HT300/GJL-300 grade Grey Cast Iron) represents a “high-precision” sector. Facing the high-speed demands of automated molding lines (such as DISAMATIC or HWS), тот core conflict lies in how to eliminate the fluctuations caused by the “intermittent melting” nature of induction furnaces and provide a supply of molten iron that is as “continuous and stable” as that of a Blast Furnace or Cupola.

я. Extreme Consistency Control of Composition and Temperature

In mass production, minute differences in each batch of molten iron can lead to uneven hardness, machining difficulties, or shrinkage porosity in castings. The key to control is transforming “variables” в “constants.”

1. Refined Charge Management (Управление источником)

Induction furnaces operate on the principle of “garbage in, garbage out” and lack the metallurgical reaction capabilities of cupolas. Поэтому, charge management is the cornerstone of stability.

• Cleanliness Control: Automotive castings are sensitive to gas porosity. Oil, moisture, and rust on Steel Scrap must be strictly controlled. For Bales, density and internal inclusions must be monitored.
• Batching Точность: Automatic batching systems must be used to ensure the ratio errors of Pig Iron, Возврат, and Steel Scrap are controlled within ± 1%.
• Trace Element Tracking: Grey iron is extremely sensitive to trace elements (например, Из, Пб, Ал). A supplier archive for trace elements must be established to avoid accumulation effects that degrade graphite morphology.

2. “Heel Melting” and Process Discipline

To maintain consistency across continuous batches, the furnace must never be fully emptied.

• Heel Melting Operation: Always maintain 30%~50% liquid iron (the heel) in the furnace.
  • Функция: Shortens the melting time for the next batch and, Что еще более важно, uses the old molten iron as a Buffer to significantly dilute the compositional fluctuations of the new charge.
• Full Power & Быстрое отопление: If grey iron stays in the high-temperature zone too long, the nucleation cores (Nuclei) will dissolve/fade, leading to an increased chill tendency. The strategy is: Melt with high power, tap immediately upon reaching temperature, and strictly prohibit holding the iron for long periods.

3. Closed-Loop Temperature Control

• Цель Точность: The pouring temperature window is usually extremely narrow (например, 1420°C ± 10°C).
• Tap Temperature Compensation: Considering the temperature drop in the transfer ladle (typically 30–50°C), the furnace tapping temperature must be adjusted via a dynamic compensation algorithm based on transfer distance and ladle status (Cold Ladle vs. Hot Ladle).

II. Configuration Schemes for Automated Molding Lines: Duplexing & Multi-systems

Automated molding lines (such as vertical parting lines) are characterized by continuous and high-speed iron consumption (например, 300-500 molds/hour). A single induction furnace cannot simultaneously satisfy the demands of Melting (Batch process) and Pouring (Continuous process).

1. Core Concept: Decoupling Melting and Holding

Separating the “плавление” function from the “Supplying” function is key to achieving a continuous flow.

2. Typical Configuration Schemes

А. “One-to-Two” или “Multi-supply-One” Duplexing

This is the most mainstream high-efficiency configuration.

• Mode: Multiple high-power Mains or Medium Frequency Melting Furnaces + 1 large capacity Holding/Pouring Furnace.
• Рабочий процесс:
  • Melting furnace melts at full speed and adjusts composition.
  • Iron is tapped into a transfer ladle.
  • Iron is poured into the large holding furnace (например, а 10-20 ton Channel Induction Furnace or Pressurized Pouring Furnace).
• Преимущества:
  • Homogenization: The holding furnace acts as a massive “mixing pool.” Even if there are slight Carbon/Silicon fluctuations between melting batches, they are leveled out upon entering the large pool, outputting extremely stable iron.
  • Buffer: During melting furnace maintenance or charging, the holding furnace inventory allows the molding line to continue production for 20-30 минуты.

Беременный. Butterfly Configuration

Suitable for ultra-large-scale production.

• Layout: 2-3 Melting furnaces arranged around a rotating intermediate transfer device or automated charging car.
• Power Distribution: Использование “Dual-Power” или “Tri-Power” systems (например, one power supply unit feeding two furnace bodies). One melts at full power while the other holds or sinters, achieving seamless switching with minimal power grid fluctuation.

3. Integration of Automated Pouring

At the end of the induction furnace duplexing scheme, а Automatic Pouring Machine (например, Pressure or Bottom-pour type) важно:

• Stream Inoculation: The auto-pourer is equipped with a precise stream inoculation device to ensure consistent inoculant dosage per mold (ошибка < 2%), which is critical for the graphite morphology of grey iron.
• Visual Positioning: Utilizes laser vision systems to automatically adjust flow rate based on the pouring cup liquid level, keeping the pouring cycle perfectly synchronized with the molding line.

Iii. Key Process Control Techniques

To guarantee the stability of the systems mentioned above, the following monitoring methods must be introduced:

Краткое содержание

For automotive engine block casting, “Стабильность” is not just a technical indicator; it is an economic one.

By utilizing a configuration of “Multi-furnace Melting + Большой Емкость Holding/Homogenization + Automatic Pouring,” combined with strict “Heel Melting” и “Precise Inoculation” процессы, the discreteness of single-batch melting can be eliminated. This satisfies the rigorous requirements of automated production lines for “Zero Defect, Continuous Flow” molten iron.