The differences between gray cast iron valves, ductile iron valves, and cast steel valves are indeed significant, mainly in terms of material composition, mechanical properties, application scenarios, and manufacturing costs. The following is a detailed analysis of the main differences between these three types:

I. Material Composition
Gray Cast Iron Valves:
Material: Gray cast iron is an iron-carbon alloy with a carbon content greater than 2%, and its graphite is in flake form.
Characteristics: Gray cast iron has good casting performance and shock absorption performance, but its strength and toughness are relatively low.
Ductile Cast Iron Valves:
Material: Ductile cast iron is also an iron-carbon alloy with a carbon content greater than 2%, but its graphite is in spherical or nodular form.
Characteristics: By changing the graphite morphology, the mechanical properties of ductile cast iron are significantly improved. Its strength, toughness, and wear resistance are superior to gray cast iron, and even comparable to cast steel.
Cast Steel Valves:
Material: Cast steel is an iron-carbon alloy with a carbon content less than 2%, and usually also contains small amounts of silicon, manganese, sulfur, phosphorus, etc.
Characteristics: Cast steel has high strength and toughness, good plasticity and weldability, and high resistance to stress. II. Mechanical Properties and Strength: Cast steel valves > Ductile iron valves > Gray cast iron valves. Toughness: Cast steel valves > Ductile iron valves > Gray cast iron valves. Wear Resistance: Ductile iron valves > Cast steel valves > Gray cast iron valves (but cast steel also has relatively high wear resistance, depending on the material and heat treatment process). Heat Resistance and Corrosion Resistance: Ductile iron valves are generally superior to gray cast iron valves, while cast steel valves vary depending on the specific material and alloying elements.

III. Application Scenarios: Gray cast iron valves: Primarily used in low-pressure, low-temperature, non-corrosive media applications such as chilled water, cooling water, and hot water in HVAC systems. Lower cost, suitable for applications where high strength and toughness requirements are not critical. Ductile iron valves: Suitable for medium and low-pressure valves with operating temperatures between -30~350℃ and nominal pressure PN≤4.0MPa. Suitable for various media such as water, seawater, steam, air, gas, and oil. Due to their excellent mechanical properties, ductile iron valves are widely used in the petroleum, chemical, and power industries. Cast steel valves are primarily used in petrochemical, power, and metallurgical industries, handling high-pressure, high-temperature, corrosive media, or applications requiring significant stress. Cast steel valves have a wide range of applications, including various valve types such as gate valves, globe valves, and check valves.

IV. Manufacturing Costs: Gray cast iron valves have relatively low manufacturing costs due to their good casting and vibration damping properties and lower overall cost. Ductile iron valves, while possessing high strength and toughness, have relatively high manufacturing costs because they require specialized casting and heat treatment processes to ensure material performance. Cast steel valves' manufacturing cost depends on the specific material and alloying elements chosen, as well as the requirements of the casting and heat treatment processes. Generally, the manufacturing cost of cast steel valves is higher than that of gray cast iron and ductile iron valves.

V. Forming Process Difficulty of Gray Cast Iron Casting Performance: Gray cast iron has good casting performance, good fluidity, easy mold filling, and relatively small solidification shrinkage, which helps reduce casting defects. Graphite Morphology: The graphite in gray cast iron is in flake form, which affects its mechanical properties to some extent. However, the formation of flake graphite is relatively easy to control during casting and does not significantly increase the process difficulty. Heat Treatment: The heat treatment process of gray cast iron is relatively simple, usually not requiring complex quenching and tempering. Annealing is mainly used to improve its microstructure and properties. Process Difficulties: The main process difficulty of gray cast iron valves lies in controlling its chemical composition and cooling rate during casting to ensure ideal graphite morphology and microstructure. In addition, gray cast iron is highly sensitive to casting defects (such as porosity, shrinkage cavities, etc.), requiring strict control of casting process parameters. VI. Forming Process Difficulty of Ductile Iron Graphite Morphology Control: The graphite in ductile iron is in spherical or nodular form, which is achieved by adding spheroidizing agents and performing spheroidizing treatment. The spheroidizing process is relatively complex, requiring precise control of chemical composition, temperature, and the amount of spheroidizing agent added to ensure the ideal graphite morphology is obtained. Improved Mechanical Properties: By altering the graphite morphology, ductile iron significantly improves its mechanical properties, such as strength, toughness, and wear resistance. However, this also increases the difficulty of its forming process, as it is necessary to ensure that new casting defects are not introduced while improving mechanical properties. Heat Treatment: The heat treatment process for ductile iron is relatively complex, typically requiring quenching and tempering to obtain the desired mechanical properties and microstructure. Process Challenges: The main process challenges for ductile iron valves lie in controlling the graphite morphology, ensuring the stability of the chemical composition, and performing precise heat treatment. Furthermore, ductile iron is relatively sensitive to casting defects, requiring strict control of casting process parameters and subsequent processing.

VII. Forming Process Challenges of Cast Steel: Chemical Composition Control: The chemical composition of cast steel is relatively complex, requiring precise control of the content of various alloying elements to ensure the desired mechanical properties and corrosion resistance are obtained. Casting Performance: Cast steel has relatively poor casting performance, with poor fluidity, making it prone to casting defects (such as porosity and inclusions). Therefore, a series of measures need to be taken during the casting process to improve its casting performance, such as increasing the pouring temperature and optimizing mold design. Heat Treatment: The heat treatment process for cast steel is relatively complex, typically requiring quenching, tempering, and surface treatment to obtain the desired mechanical properties and microstructure. Process Challenges: The main process challenges for cast steel valves lie in controlling chemical composition, improving casting performance, ensuring effective heat treatment, and preventing casting defects. Furthermore, cast steel has a high shrinkage rate, making it prone to cracks and deformation, requiring strict control of process parameters during casting and heat treatment. The forming processes for gray cast iron valves, ductile iron valves, and cast steel valves each have their own unique characteristics and difficulties. The manufacturing process of gray cast iron valves is relatively simple, but attention must be paid to the control of chemical composition and cooling rate during casting. The manufacturing process of ductile iron valves is moderately difficult, but precise control of graphite morphology and complex heat treatment are required. The manufacturing process of cast steel valves is relatively difficult, requiring strict control of chemical composition, improvement of casting performance, ensuring heat treatment effect, and prevention of casting defects.