Study on Heat Treatment Process of ASTM A565 XM-32 Stainless Steel

Abstract

This study investigates the effect of heat treatment processes on the mechanical properties of ASTM A565 XM-32 stainless steel at room temperature. The results show that when the quenching temperature is 1030°C, the tensile strength and impact toughness reach their peak values. However, the tempering holding time should not be excessively prolonged.

Keywords: ASTM A565 XM-32, quenching temperature, tempering time

Introduction

ASTM A565 XM-32 stainless steel is used for manufacturing turbine wheels in gas turbines. Due to the demanding working environment, the steel must exhibit high strength and impact toughness at room temperature (A_k ≥ 100 J, as per ASTM A565 standards). Additionally, it must withstand a specified temperature (595°C) and load (240 MPa) for 30 hours without fracture in notched composite specimens. To ensure the success of the heat treatment process and avoid repeated treatments, a series of experiments were conducted to determine the optimal parameters.

Technical Requirements

1. Chemical Composition

The chemical composition requirements (mass fraction, %) are listed in Table 1.

Table 1: Chemical composition requirements

Residual elements: Al ≤ 0.05%, As ≤ 0.15%, Sn ≤ 0.10%, Sb ≤ 0.003%.

2. Mechanical Properties at Room Temperature

The mechanical property requirements are listed in Table 2.

Table 2: Mechanical property requirements

Experimental Procedure

1. Material Preparation

The steel was produced using the EAF + LHF + VCD + ESR process. The melting analysis is shown in Table 3.

Table 3: Melting analysis (mass fraction, %)

2. Forging and Processing

• Forging temperature: 880°C–1180°C.
• Samples were forged into Φ60 mm billets and then machined into Φ30 mm specimens.

3. Heat Treatment Schemes

Five heat treatment schemes were tested:

1. Quenching at 990°C (1 h, oil cooling), tempering at 560°C (3 h, oil cooling).
2. Quenching at 1010°C (1 h, oil cooling), tempering at 560°C (3 h, oil cooling).
3. Quenching at 1030°C (1 h, oil cooling), tempering at 560°C (3 h, oil cooling).
4. Quenching at 1040°C (1 h, oil cooling), tempering at 560°C (3 h, oil cooling).
5. Quenching at 1050°C (1 h, oil cooling), tempering at 560°C (3 h, oil cooling).

Results and Discussion

1. Effect of Quenching Temperature:

   • At 1030°C, tensile strength and impact toughness peaked.
   • Higher temperatures (>1030°C) led to grain coarsening, reducing strength and toughness.

2. Effect of Tempering Time:

   • Extending tempering time to 5 hours caused carbides to coarsen, reducing strength and toughness.

Conclusion

1. The optimal quenching temperature for ASTM A565 XM-32 is 1030°C.
2. Tempering time should not exceed 3 hours to avoid performance degradation.
3. The recommended heat treatment process is:
   • Quenching: 1030°C for 1 hour, oil cooling.
   • Tempering: 580°C for 3 hours, oil cooling.

References

1. Tanaka, T. Ferritic Stainless Steels. Translated by Zhang Jiayuan, Zhang Shaolin. Beijing: Metallurgical Industry Press, 2003.
2. China Materials Engineering Canon (Vol. 3): Iron and Steel Materials Engineering (Part 2). Beijing: Chemical Industry Press, 2005.
3. Cui Zhiwu, Cao Zhenchun. Metallurgy and Heat Treatment, 2nd Edition. Beijing: Mechanical Industry Press, 2007.

SEO Optimization Notes:

• Title: Includes key terms like "ASTM A565 XM-32" and "heat treatment" for searchability.
• Keywords: Highlighted for SEO.
• Structured Content: Clear sections (Abstract, Introduction, Results, Conclusion) improve readability and indexing.
• Technical Details: Tables and specific parameters enhance relevance for technical searches.
• Citations: References add credibility and depth.