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30 กรกฎาคม 2026

หน้าแปลน ASTM A182 F91 สำหรับระบบท่ออุณหภูมิสูง

Technical guideReviewed: 30 กรกฎาคม 2026Prepared by SASA FLANGE Technical Content Team

Direct answer

An ASTM A182 F91 flange does not have one universal “temperature range.” Its permitted pressure at temperature depends on the adopted ASME B16.5 edition, กลุ่มวัสดุ, flange class, governing piping code and project limits. F91 is intended for elevated-temperature Grade 91 systems, but both lower-temperature toughness and upper-temperature creep behaviour must be checked by the designer.

Key takeaways

  • Never convert flange Class directly into psi without the material-specific pressure-temperature table.
  • Chemical composition alone cannot prove that an F91 forging has the correct normalized-and-tempered condition.
  • ระดับ 91 reliability depends heavily on welding, PWHT and hardness control across the complete joint.

Why there is no single F91 maximum temperature

Flange ratings decrease as temperature changes, and each pressure class follows the material group assigned by the standard. The piping code may impose additional allowable-stress, creep-life, ความเหนียว, cyclic or service restrictions. Plant owners can also set limits that are more conservative than the published standard.

ดังนั้น, a supplier should not approve a design from temperature alone. A technical enquiry needs design pressure, อุณหภูมิการออกแบบ, ขนาด, ระดับ, pipe wall, service, design code and required standard edition.

What makes Grade 91 different?

F91 is a modified 9Cr-1Mo steel strengthened through controlled composition and heat treatment. Its elevated-temperature properties depend on achieving and preserving the intended microstructure. Improper heat treatment or field welding can reduce performance even if PMI confirms chromium and molybdenum content.

Documentation should show the required heat-treatment route and mechanical results. Project controls frequently address hardness before welding, after PWHT and across repaired areas.

Pressure class and temperature must be checked together

ASME Class 150, 300, 600, 900, 1500 และ 2500 are rating designations, not fixed pressure values. A Class 600 F91 flange can have a different allowable pressure from another material at the same temperature, and its rating changes as temperature changes.

Use the exact table in the purchased standard. Do not design from an online summary table, a catalogue nominal value or a room-temperature pressure label.

What buyers should request from an F91 flange supplier

  • Original or traceable ASTM A182 F91 material certificate
  • Heat-treatment temperatures and mechanical-property results
  • Hardness readings and test-location plan where required
  • PMI method appropriate to the elements being verified
  • Dimensional report, NDE records and heat-number marking
  • Protected weld ends and sealing faces for export shipment

The flange certificate must be reviewed together with the approved welding procedure and the adjoining P91 material records.

คำถามที่พบบ่อย

Can a supplier state an exact F91 maximum temperature?

A supplier can identify published rating data for a stated standard edition, ขนาดและชั้นเรียน, but the project engineer must approve the actual design limit under the governing code.

Does PMI confirm correct F91 heat treatment?

เลขที่. PMI identifies alloy chemistry. Heat-treatment records, mechanical tests, hardness and—where required—additional metallurgical examination address material condition.

Why is PWHT important for an F91 joint?

A qualified PWHT cycle helps establish the required weld and heat-affected-zone condition. Incorrect temperature, hold time or heating control can create unacceptable properties.

Related alloy flange guides

Match P91 Pipe With F91 Flanges Flange Hardness Testing F11 F22 F91

Primary standards referenced

Always verify the edition specified by the purchase order and obtain the complete controlled standard for design and acceptance.

Request an alloy steel flange quotation

Send the material grade, มาตรฐาน, กรมอุทยานฯ, ระดับความดัน, ประเภทหน้าแปลน, หันหน้าไปทาง, pipe schedule, ข้อกำหนดด้านปริมาณและการตรวจสอบ. SASA FLANGE will review the technical description before quotation.

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