13CrMo44 (material number 1.7335, also known as SIQUAL 7335) is a chromium-molybdenum low-alloy pearlitic heat-resistant steel designed for elevated-temperature service in boiler and pressure vessel applications. The material finds extensive use in water boilers, collectors, superheater tubes, and steam pipes in power generation facilities.
The maximum working temperature for 13CrMo44 boiler tubes depends on the specific service conditions and application requirements. For low and medium-pressure boiler applications with working pressures generally not exceeding 5.88 MPa, the maximum operating temperature is typically below 450°C. For high-pressure boiler applications operating at pressures above 9.8 MPa, the material can be used at temperatures ranging from 450°C to 650°C for heating surface tubes, economizers, superheaters, and reheaters.
Multiple sources provide slightly varying maximum temperature specifications. Some references indicate a maximum service temperature of 530°C for collectors, water boilers, and superheater tubes. Others cite 550°C as the upper limit for continuous service, while certain patents reference an admissible maximum temperature of approximately 515°C for evaporator tubes in once-through steam generators. The material is also noted for use in superheaters within the 450–750°C range alongside other advanced alloys. The heat treatment regime for 13CrMo44 typically involves normalizing at 900–940°C followed by tempering at 650–720°C, which develops the optimal creep strength and oxidation resistance for high-temperature service. In practice, the maximum working temperature should be determined based on the specific design code, pressure conditions, and required service life, with 550–600°C generally considered the practical upper limit for most boiler tube applications.
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