​Complete Guide to Melting and Application of HT400 Grey Cast Iron

Overview of HT400 In the casting industry, HT400 gray cast iron has become the preferred material for many key castings due to its excellent comprehensive performance.

How was it 'refined'? In which high-end fields can one demonstrate their skills?

The commonly used melting equipment includes a blast furnace and a medium frequency induction furnace.

Cupola has high melting efficiency and low cost, making it suitable for large-scale production. However, it has strict requirements for raw materials, and the situation of element burnout and sulfur addition during melting is complex. The medium frequency induction furnace, with its advantages of fast melting speed, precise temperature control (up to ± 10 ℃), and low element loss, can effectively control the composition of molten iron and is an ideal choice for melting high-quality gray cast iron.

The art of temperature and stirring in the melting process takes the medium frequency induction furnace as an example. After loading the furnace material into the furnace, turn on the power and gradually increase the temperature.

During smelting, it is necessary to closely observe the condition inside the furnace. When the furnace material begins to melt, stir the molten iron in a timely manner to promote uniform composition. The temperature is controlled at around 1500~1560 ℃, which can ensure the full melting and uniform composition of the molten iron, while reducing gas dissolution and inclusion generation.

The precise adjustment of composition controls each element during the melting process, and uses pre furnace analysis methods such as spectral analysis to detect the composition of the molten iron.

If the carbon content is too high, add scrap steel for adjustment; If the carbon content is too low, add a carbon enhancer.

For elements such as silicon and manganese, alloys such as ferrosilicon and manganese iron should be added in a timely manner based on the analysis results and target composition. Silicon can promote graphitization and reduce the tendency towards white casting, while manganese can enhance the strength and wear resistance of gray cast iron. Both are indispensable.

Fertility treatment endows castings with a "delicate soul" to refine graphite flakes and improve their mechanical properties. Before being discharged from the furnace, a fertility agent needs to be added to the molten iron. The commonly used amount of 75% silicon iron added is generally 0.3% to 0.6% of the mass of the molten iron. By using methods such as in flow inoculation or in package inoculation, the inoculant is evenly dispersed in the molten iron, fully exerting the effect of refining graphite sheets.

Pre furnace inspection with multiple quality assurance triangle test pieces is a commonly used method. By observing the width of the white mold, the effect and composition of the iron liquid can be determined to meet the standards. If they do not meet the standards, the composition or dosage of the iron liquid can be adjusted in a timely manner.

In addition, methods such as thermal analysis can also be used to detect the solidification characteristics of molten iron, ensuring that the final melted iron meets the performance requirements of HT400 gray cast iron.

Application fields of HT400 gray cast iron

Machine tool castings stabilize the "steel skeleton" bed and worktable of machine tools: The bed of milling machines, lathes, and other machine tools needs to withstand various loads such as their own weight and cutting forces. HT400 gray cast iron ensures that the bed body will not deform during long-term use due to its high strength, and its good shock absorption reduces machine tool vibration, thereby improving machining accuracy.

Column and crossbeam: The columns and crossbeams of large machine tools must withstand enormous cutting forces and workpiece weight during processing. The high strength of HT400 gray cast iron provides reliable support and ensures structural stability.

Automotive parts castings safeguard driving safety. Brake drums and brake discs: When working, automotive brake drums and brake discs must withstand frictional heat and friction. HT400 gray cast iron has excellent wear resistance and high strength, which can ensure that brake components do not fail in long-term use and safeguard driving safety.

Engine cylinder block: The engine cylinder block of some heavy-duty vehicles or specific industrial vehicles needs to withstand high temperatures, high pressures, and mechanical forces. HT400 gray cast iron has high strength, good heat resistance, and excellent casting performance, and can be cast into complex cylinder structures.

Composition and Properties of HT400 Grey Cast Iron

The "hard core" performance of HT400 gray cast iron is due to precise composition control: carbon content of 2.8% to 3.3%, silicon content of 1.2% to 1.8%, manganese content of 0.8% to 1.2%, phosphorus<0.15%, sulfur<0.12%, and alloy elements such as copper and chromium can be added according to demand. This combination of ingredients gives it a "steel rib and iron bone" with a tensile strength of ≥ 400MPa, while also possessing good shock absorption, wear resistance, and casting processability, making it an ideal choice for heavy-duty, high-precision castings.

HT400 gray cast iron smelting production process

The raw materials for HT400 gray cast iron can be called the "iron triangle" combination, consisting of pig iron, scrap steel, and recycled materials.

Among them, high-quality pig iron with low sulfur and phosphorus is the main provider of carbon and other trace elements;

Scrap steel can not only regulate the carbon content of molten iron and reduce its carbon content, but also reduce shrinkage defects in castings;

The recycled material comes from castings or sprues of the same material previously produced in the workshop, and recycling can effectively reduce costs.

In addition, according to the composition standards of HT400 gray cast iron, each raw material must be accurately calculated and weighed before melting to ensure precise proportioning and lay the foundation for high-quality molten iron.

HT400 gray cast iron is not only a "steel that can be cast", but also a "cornerstone material" for high-end equipment manufacturing. From precision machine tools to heavy machinery, from automotive safety to mold accuracy, it demonstrates with its strength that 'even cast iron can be very advanced'! Mastering the melting essence and application password of HT400 can seize the opportunity in the high-end casting field and win the trust of customers.