Abstract

Due to their excellent high-temperature strength, oxidation resistance, and thermal fatigue resistance, heat-resistant steels are widely used in energy, chemical, aerospace, and other industries. The article provides a detailed analysis of material selection, smelting processes, casting methods, and heat treatment technologies in heat-resistant steel casting, and discusses current challenges and future development trends.

1. Overview of Heat-Resistant Steels

Heat-resistant steels refer to special steels that maintain good mechanical properties and chemical stability in high-temperature environments. According to different alloy compositions, heat-resistant steels can be divided into three main categories: ferritic heat-resistant steels, austenitic heat-resistant steels, and martensitic heat-resistant steels. These steels typically contain alloying elements such as chromium (Cr), nickel (Ni), molybdenum (Mo), tungsten (W), and vanadium (V) to enhance their high-temperature performance.

2. Heat-Resistant Steel Casting Process Flow

2.1 Material Selection and Proportioning

The primary step in heat-resistant steel casting is selecting the appropriate material formulation based on the service environment. Chromium content usually ranges between 12-30%, while nickel content can exceed 20%. Precise control of carbon content (0.1-0.4%) is crucial for balancing high-temperature strength and weldability.

2.2 Smelting Process

Heat-resistant steels are typically smelted in electric arc furnaces or induction furnaces, with smelting temperatures controlled between 1550-1650°C. To reduce gas inclusions, vacuum smelting or inert gas protection technologies are often employed. The sequence and timing of alloy element additions significantly affect the final material properties.

2.3 Casting Methods

Common heat-resistant steel casting methods include:

Sand casting: Suitable for large, complex parts

Investment casting (lost-wax method): Used for high-precision components

Centrifugal casting: Applicable for tubular parts

Continuous casting: Used for mass production

2.4 Heat Treatment

Heat-resistant castings usually require solution treatment and aging treatment to optimize microstructure and mechanical properties. Heat treatment temperature and time must be precisely controlled according to specific alloy compositions.

3. Technical Challenges and Solutions

3.1 Hot Crack Control

Heat-resistant steel casting is prone to hot cracking. Solutions include:

Optimizing gating system design

Controlling cooling rates

Using appropriate mold materials

3.2 Microstructure Control

By adding trace alloying elements (such as Nb, Ti) and precisely controlling heat treatment processes, the high-temperature performance of heat-resistant steels can be improved.

3.3 Surface Quality Control

Advanced surface treatment technologies, such as hot-dip aluminizing or chromizing, can further enhance the oxidation resistance of heat-resistant steels.

4. Application Fields

Heat-resistant steel castings are widely used in:

Power generation equipment: Turbine blades, boiler components

Petrochemical industry: Cracking furnace tubes, reactors

Aerospace: Engine components

Automotive industry: Turbocharger housings

5. Future Development Trends

Future directions for heat-resistant steel casting technology include:

Developing new heat-resistant alloys with higher temperature grades

Adopting additive manufacturing technologies to produce complex heat-resistant components

Intelligent casting process control

Environmentally friendly production processes

Conclusion

Heat-resistant steel casting is a manufacturing process with high technical requirements and complex procedures. With advancements in materials science and manufacturing technologies, the performance of heat-resistant steel castings will continue to improve, and their application fields will further expand. Continuous optimization of casting processes and development of new alloys remain key research directions for the future.