1. Q: What is ASTM B407 Incoloy 800HT, and what distinguishes "large diameter bright annealed tube" from standard 800HT products?
A:
ASTM B407 is the standard specification for seamless nickel-iron-chromium alloy pipe and tube. Incoloy 800HT (UNS N08811) is the premium high-temperature grade within this specification, featuring controlled carbon (0.06–0.10%) and elevated aluminum plus titanium (0.85–1.20%) for enhanced creep strength.
What is "large diameter" for ASTM B407 tube?
While ASTM B407 covers sizes up to 273 mm OD (10.75″ NPS), "large diameter" in the context of seamless tube typically refers to:
| Diameter Category | Size Range | Typical Applications |
|---|---|---|
| Standard tube | 6–76 mm OD (¼″–3″) | Heat exchangers, instrumentation |
| Large diameter tube | 76–219 mm OD (3″–8″) | Transfer lines, furnace headers, manifold piping |
| Extra large pipe | 219–273 mm+ OD (8″–12″+) | Main process piping, reactor nozzles |
Producing seamless tube above 150 mm OD (6″ NPS) in 800HT requires specialized extrusion or rotary piercing capabilities. Large diameter seamless tube is significantly more challenging to manufacture than small-diameter tube.
What is "bright annealing"?
Bright annealing is a heat treatment performed in a controlled atmosphere furnace (typically hydrogen, dissociated ammonia, or vacuum) that prevents oxidation of the tube surface. Unlike conventional solution annealing (which produces a dark, scaled surface), bright annealing leaves the tube with a clean, metallic, oxide-free surface.
Comparison of annealing methods for 800HT:
| Feature | Conventional Annealing (Air) | Bright Annealing (Controlled Atmosphere) |
|---|---|---|
| Atmosphere | Air | Hydrogen, N₂-H₂, or vacuum |
| Surface finish | Dark oxide scale | Bright, metallic, oxide-free |
| Subsequent cleaning | Requires pickling or mechanical descaling | None needed |
| Wall thickness loss | 0.05–0.10 mm (scale formation) | Negligible |
| Surface hardness | May vary | Uniform |
| Cost | Lower (standard) | 15–30% premium |
| Corrosion resistance | Restored by pickling | Immediate (passive film intact) |
Bright annealing process for large diameter 800HT tube:
Cold drawing – The tube is cold drawn to final dimensions (large diameter requires multiple passes with intermediate anneals).
Degreasing – The tube is thoroughly cleaned to remove drawing lubricants (oils, greases, soaps). Any residual carbon would contaminate the bright annealing atmosphere.
Bright annealing – The tube is heated to 1150–1200°C (2100–2190°F) in a protective atmosphere (typically 100% hydrogen or 95% N₂ + 5% H₂). Hydrogen acts as a reducing agent, converting any surface oxides back to base metal. The tube is then rapidly cooled (water quench or forced gas cooling) while still in the protective atmosphere.
Resulting properties:
Grain size: ASTM No. 5 or coarser (required for 800HT)
Surface: Bright, metallic, free of scale and discoloration
Oxide thickness: < 50 nanometers (passive film)
Roughness (Ra): Typically 0.4–0.8 µm (16–32 µin) – much smoother than pickled surfaces
Why bright annealing is important for large diameter 800HT tube:
| Benefit | Explanation |
|---|---|
| Eliminates pickling | Large diameter tubes are difficult to pickle uniformly; bright annealing avoids acid handling entirely |
| No hydrogen embrittlement risk | Unlike pickling (which can introduce hydrogen), bright annealing removes hydrogen |
| Superior surface finish | Smooth surface reduces stress concentrations and improves oxidation resistance |
| Uniform properties | Controlled atmosphere ensures consistent grain structure across the entire tube length |
| Ready for installation | No post-heat-treatment cleaning required |
Typical bright annealed surface finish specifications:
| Parameter | Bright Annealed 800HT | Pickled 800HT |
|---|---|---|
| Surface appearance | Shiny, reflective | Matte, dull gray |
| Ra roughness (µm) | 0.4–0.8 | 1.6–3.2 |
| Oxide thickness (nm) | < 50 (passive) | 100–500 (after passivation) |
| Iron contamination risk | Very low | Moderate (if not properly passivated) |
Applications where bright annealed large diameter 800HT tube is specified:
Ethylene cracking furnace transfer lines – Smooth surface reduces coke deposition.
Hydrogen reformer outlet manifolds – Clean surface ensures uniform oxide formation.
High-temperature thermowells – Smooth surface improves thermal response.
Ultra-high-purity semiconductor furnace components – No pickling residues.
Key takeaway: ASTM B407 Incoloy 800HT large diameter bright annealed tube combines the creep strength of 800HT with a clean, oxide-free surface that eliminates post-anneal pickling. This is essential for high-purity, high-temperature applications where surface contamination cannot be tolerated.
2. Q: How does the bright annealing process affect the microstructure, mechanical properties, and creep strength of large diameter 800HT tube compared to conventionally annealed tube?
A:
The bright annealing process uses the same temperature range (1150–1200°C) as conventional solution annealing. The key difference is the protective atmosphere, which prevents oxidation but does not alter the metallurgical transformations. Therefore, properly bright annealed 800HT tube has identical microstructure and mechanical properties to conventionally annealed (then pickled) tube.
Microstructural effects of bright annealing on 800HT:
| Microstructural Feature | Bright Annealed | Conventionally Annealed (Air + Pickled) |
|---|---|---|
| Grain size | ASTM No. 5–7 (coarse) | ASTM No. 5–7 (coarse) |
| Grain boundary carbides | M₂₃C₆, uniform | M₂₃C₆, uniform |
| Titanium carbonitrides | Ti(C,N), fine dispersion | Ti(C,N), fine dispersion |
| Surface chromium depletion | None (oxide-free) | 1–2 µm (removed by pickling) |
| Internal oxidation | None | < 5 µm (if pickling incomplete) |
Why microstructure is identical:
The solution annealing temperature (1150–1200°C) is well above the recrystallization temperature of 800HT. During annealing:
Recrystallization occurs, forming new, strain-free grains.
Grain growth produces the required coarse grain structure (ASTM No. 5 minimum).
Carbides dissolve then reprecipitate uniformly during cooling.
Ti(C,N) particles remain stable, pinning grain boundaries and preventing excessive coarsening.
The atmosphere (air vs. hydrogen) does not affect these solid-state transformations. The only difference is surface condition.
Mechanical properties comparison (room temperature):
| Property | Bright Annealed | Conventionally Annealed + Pickled | ASTM B407 Minimum |
|---|---|---|---|
| Tensile strength (MPa) | 580–620 | 580–620 | 515 |
| Yield strength (MPa) | 240–270 | 240–270 | 205 |
| Elongation (%) | 40–45 | 40–45 | 30 |
| Hardness (HRB) | 75–85 | 75–85 | Not specified |
Creep strength comparison (800HT, 800°C):
| Property | Bright Annealed | Conventionally Annealed | Code Case 2225 Allowable |
|---|---|---|---|
| 100,000 hr rupture strength (MPa) | 28–32 | 28–32 | 8.6 (design) |
| 1% creep in 10,000 hr (MPa) | 11–13 | 11–13 | Not applicable |
No difference – creep strength is governed by grain size and carbide distribution, which are identical between bright and conventionally annealed material.
Surface property differences (important for certain applications):
| Surface Property | Bright Annealed | Conventionally Annealed + Pickled |
|---|---|---|
| Surface roughness (Ra, µm) | 0.4–0.8 | 1.6–3.2 |
| Residual stress (surface) | Low (compressive if gas quenched) | Low (tensile if pickled) |
| Oxide scale thickness | < 50 nm (passive Cr₂O₃) | 100–500 nm (after passivation) |
| Hydrogen content | Very low (H₂ atmosphere, then degassed) | Possible hydrogen pickup from pickling |
| Cleanliness (particulates) | Excellent (no acid residues) | Good (if properly rinsed) |
Potential pitfalls of bright annealing for large diameter tube:
| Pitfall | Cause | Prevention |
|---|---|---|
| Incomplete recrystallization | Insufficient temperature or time | Verify furnace temperature profile; use proper soak time (1 min/mm wall) |
| Grain size too fine (ASTM 8–10) | Annealing temperature too low (< 1100°C) | Increase to 1150–1200°C |
| Grain size too coarse (ASTM 2–3) | Excessive temperature (> 1220°C) or time | Control soak time; avoid overheating |
| Surface discoloration (blue/purple) | Oxygen leak in furnace atmosphere | Check seals; maintain positive atmosphere pressure |
| Carburization (black surface) | Hydrocarbon contamination in atmosphere | Use pure hydrogen; clean tube before annealing |
| Hydrogen embrittlement (rare) | Hydrogen trapped in lattice | Proper cooling cycle; hydrogen degasses rapidly at 800HT temperatures |
Testing requirements to verify proper bright annealing:
| Test | Purpose | Acceptance |
|---|---|---|
| Grain size (ASTM E112) | Verify ASTM No. 5 minimum | No. 5 or coarser |
| Tensile test (ASTM E8) | Verify mechanical properties | 515 MPa UTS, 205 MPa YS min |
| Surface roughness (profilometer) | Verify bright finish | Ra ≤ 0.8 µm typical |
| Water break test | Verify no hydrophobic contamination | Continuous film |
| Ferroxyl test (optional) | Verify no iron contamination | No blue color |
Key takeaway: Bright annealing produces large diameter 800HT tube with identical bulk mechanical and creep properties to conventionally annealed tube. The advantages are purely surface-related: cleaner, smoother, oxide-free finish with no pickling required. For applications where surface condition is critical (e.g., ultra-high-purity, low-friction, or reduced coke deposition), bright annealing is worth the premium.
3. Q: What are the specific challenges in producing large diameter bright annealed 800HT tube, and how do they affect cost and lead time?
A:
Producing large diameter (≥ 76 mm OD / 3″ NPS) seamless tube in 800HT is challenging. Adding bright annealing requirements increases complexity, cost, and lead time significantly.
Challenge 1: Producing large diameter seamless 800HT tube
| Challenge | Description | Mitigation |
|---|---|---|
| Extrusion/piercing limit | Most seamless tube mills are limited to 150–200 mm OD for nickel alloys | Specialized extrusion presses (e.g., 5000+ ton) required for diameters > 200 mm |
| Cold drawing forces | Large diameter tubes require massive drawing forces | Multiple passes with intermediate anneals; heavy-wall tube may require warm drawing |
| Wall uniformity | Maintaining concentricity is difficult at large diameters | Precision mandrels; slow drawing speeds |
| Straightness | Large diameter tubes tend to bow | Roll straightening after each cold draw pass |
Result: Large diameter seamless 800HT tube is produced by only a few specialty mills worldwide. Lead times are typically 20–30 weeks for large diameters (vs. 10–16 weeks for small diameters).
Challenge 2: Bright annealing large diameter tube
Bright annealing requires the tube to be heated uniformly in a controlled atmosphere. For large diameters, this is challenging:
| Challenge | Description | Solution |
|---|---|---|
| Furnace size | Large diameter tubes require wide muffle furnaces | Investment in large horizontal bright annealing furnaces (capital intensive) |
| Atmosphere purity | Maintaining low oxygen/hydrogen dew point across large cross-section | High flow rates of purified hydrogen; continuous monitoring |
| Temperature uniformity | Temperature variation across tube diameter affects grain size | Multi-zone heating; slow traverse speeds |
| Cooling rate | Rapid cooling (required to prevent carbide precipitation) is difficult for large diameters | Water-cooled cooling sections; forced hydrogen convection |
| Surface marking | Tube contact with furnace rollers can mark bright surface | Non-marking roller materials (ceramic, quartz) |
Furnace types for bright annealing large diameter tube:
| Furnace Type | Max Tube Diameter | Atmosphere | Capital Cost | Operating Cost |
|---|---|---|---|---|
| Horizontal continuous (roller hearth) | 300 mm | H₂ or N₂-H₂ | High | Moderate |
| Vertical continuous | 150 mm | H₂ | Very high | Moderate |
| Batch (retort) | 500 mm | H₂ or vacuum | Moderate | High (long cycle times) |
| Vacuum furnace | 250 mm | Vacuum (10⁻⁵ torr) | Very high | High (slow heating/cooling) |
For large diameter tube (150–250 mm OD), horizontal continuous roller hearth furnaces with hydrogen atmosphere are most common.
Challenge 3: Surface protection and handling
| Issue | Description | Prevention |
|---|---|---|
| Scratching | Large tubes are heavy; movement causes scratches | Protective sleeves; soft roller coatings; careful handling |
| Fingerprints (acid contamination) | Human contact leaves chlorides | Gloves; automated handling |
| Storage corrosion | Bright surface is active; will rust in humid conditions | Store in low-humidity environment; apply temporary protective coating |
| End damage | Tube ends are vulnerable during transport | Plastic end caps; padded supports |
Cost comparison (relative to small diameter standard annealed tube):
| Tube Type | Relative Cost per kg | Typical Lead Time |
|---|---|---|
| Small diameter (25 mm OD) standard annealed | 1.0× (baseline) | 8–12 weeks |
| Small diameter bright annealed | 1.2–1.3× | 10–14 weeks |
| Large diameter (150 mm OD) standard annealed | 1.5–1.8× | 16–24 weeks |
| Large diameter bright annealed | 2.0–2.5× | 24–36 weeks |
Example pricing (indicative, 2025):
| Product | 800HT, 150 mm OD × 6 mm wall, 6 meters | Cost |
|---|---|---|
| Standard annealed + pickled | $8,000–10,000 | |
| Bright annealed | $12,000–16,000 |
Lead time breakdown for large diameter bright annealed 800HT tube:
| Step | Duration |
|---|---|
| Mill order processing | 2–4 weeks |
| Billet procurement (if not in stock) | 4–8 weeks |
| Hot extrusion to hollow | 2–3 weeks |
| Cold drawing (multiple passes) | 6–10 weeks |
| Intermediate anneals (if required) | Included in cold drawing |
| Bright annealing | 1–2 weeks (furnace scheduling) |
| Cutting, straightening, end finishing | 1 week |
| Inspection and testing | 1–2 weeks |
| Packaging and shipping | 1 week |
| Total | 18–32 weeks |
When is the premium justified?
| Application | Justification for Bright Annealed |
|---|---|
| Ethylene cracking TLEs | Smooth surface reduces coke deposition, extending run length |
| Semiconductor furnace components | No pickling residues; ultra-clean surface |
| Hydrogen reformer manifolds | Uniform oxide formation; no pickling required (reduces turnaround time) |
| High-purity chemical reactors | No surface contamination; no hydrogen embrittlement risk |
| Standard heat exchanger tubes | Not justified (pickled tube is sufficient) |
Key takeaway: Large diameter bright annealed 800HT tube is a specialty product with long lead times (24–36 weeks) and significant cost premium (2–2.5× baseline). Order well in advance of project requirements. For most applications, standard annealed and pickled tube is sufficient and more economical.
4. Q: What are the critical applications in petrochemical and power generation that require ASTM B407 Incoloy 800HT large diameter bright annealed tube?
A:
Large diameter bright annealed 800HT tube is specified for applications where surface condition directly impacts service life, product purity, or maintenance frequency. The bright annealed finish eliminates pickling residues and provides the smoothest possible surface.
Application 1: Ethylene Cracking Furnace Transfer Line Exchangers (TLEs)
| Parameter | Value |
|---|---|
| Diameter | 100–200 mm OD (4″–8″ NPS) |
| Temperature | 800–900°C |
| Pressure | 5–10 bar |
| Atmosphere | Hydrocarbons (C₂–C₄), H₂, steam |
| Critical requirement | Smooth ID surface to minimize coke deposition |
Why bright annealed is preferred:
Coke (carbon) deposits on rough surfaces or surfaces with iron contamination. The bright annealed surface (Ra ≤ 0.8 µm) is significantly smoother than pickled surfaces (Ra 1.6–3.2 µm). Smoother surfaces:
Reduce coke adhesion, extending run length between decokes.
Allow easier mechanical or chemical decoking when deposits occur.
Provide more uniform heat transfer.
Application 2: Steam Methane Reformer (SMR) Outlet Manifolds
| Parameter | Value |
|---|---|
| Diameter | 150–250 mm OD (6″–10″ NPS) |
| Temperature | 750–850°C |
| Pressure | 15–35 bar |
| Atmosphere | H₂, CO, CO₂, H₂O, CH₄ |
| Critical requirement | No pickling residues that could catalyze carburization |
Why bright annealed is preferred:
Pickling can leave fluoride or chloride residues in surface crevices. At high temperature, these residues can catalyze carburization, accelerating carbon ingress and embrittlement. Bright annealing leaves no such residues.
Application 3: High-Temperature Thermowells and Sensor Sheaths
| Parameter | Value |
|---|---|
| Diameter | 25–50 mm OD (1″–2″ NPS) |
| Temperature | 800–1000°C |
| Pressure | Up to 100 bar |
| Atmosphere | Variable (process-dependent) |
| Critical requirement | Smooth surface for accurate temperature measurement |
Why bright annealed is preferred:
Rough or oxidized surfaces have variable emissivity, affecting radiation heat transfer and temperature measurement accuracy. The bright, oxide-free surface provides consistent thermal response.
Application 4: Ultra-High-Purity Semiconductor Furnace Components
| Parameter | Value |
|---|---|
| Diameter | 50–150 mm OD |
| Temperature | 900–1100°C |
| Atmosphere | High-purity N₂, H₂, or Ar |
| Critical requirement | No metallic contamination (Fe, Ni, Cr particles) |
Why bright annealed is required:
Semiconductor wafers are extremely sensitive to metallic contamination (parts-per-billion levels). Pickled surfaces can have embedded iron particles or acid residues. Bright annealing produces a clean, passive surface without contamination risk.
Application 5: Hydrogen Reformer Primary Outlet Pigtails
| Parameter | Value |
|---|---|
| Diameter | 50–100 mm OD (2″–4″ NPS) |
| Temperature | 850–950°C |
| Pressure | 20–40 bar |
| Atmosphere | H₂, CO, steam |
| Critical requirement | Uniform oxide formation; no localized spalling |
Why bright annealed is preferred:
Bright annealed tubes form a uniform, adherent Cr₂O₃ scale during initial service. Pickled tubes may have residual scale or surface roughness that leads to localized spalling. Spalled areas carburize rapidly, leading to premature failure.
Performance comparison: Bright annealed vs. pickled in ethylene TLE service:
| Parameter | Bright Annealed | Pickled |
|---|---|---|
| Initial surface roughness (Ra, µm) | 0.4–0.8 | 1.6–3.2 |
| Coke deposition rate (relative) | 1.0× | 1.5–2.0× |
| Time between decokes | 12–18 months | 6–12 months |
| Oxide spalling after 1 year | Minimal | Moderate |
| Tube life (typical) | 8–12 years | 6–10 years |
Material selection matrix for high-temperature petrochemical tube:
| Service Condition | Recommended Product | Justification |
|---|---|---|
| Ethylene TLE, < 850°C, large diameter | Bright annealed 800HT | Coke reduction |
| Ethylene TLE, < 850°C, small diameter | Pickled 800HT (or bright annealed) | Both acceptable |
| SMR manifold, > 800°C, large diameter | Bright annealed 800HT | No pickling residues |
| SMR manifold, < 750°C | Pickled 800H | Lower cost, acceptable |
| Ammonia reformer, any diameter | Pickled 800H | Nitridation is primary concern, not surface finish |
| Semiconductor furnace | Bright annealed 800HT (or better) | Ultra-high-purity requirement |
Key takeaway: Bright annealed large diameter 800HT tube is not required for all applications. It is specifically indicated when:
Coke deposition is a operational concern (ethylene, olefins)
Pickling residues cannot be tolerated (high-purity, semiconductor)
The tube will be used as-supplied without post-anneal cleaning
Surface roughness directly affects performance (thermowells, flow sensors)
For standard high-temperature pressure vessel applications (reformer shells, heat exchanger shells), pickled 800HT is sufficient and more economical.
5. Q: What are the inspection, testing, and certification requirements for ASTM B407 Incoloy 800HT large diameter bright annealed tube for critical service?
A:
For critical petrochemical, power generation, or semiconductor applications, bright annealed 800HT tube must meet rigorous inspection and testing requirements beyond the base ASTM B407 specification.
Mandatory tests per ASTM B407 (all tube):
| Test | ASTM Method | Frequency | Acceptance |
|---|---|---|---|
| Chemical analysis (heat) | E1473 | Per heat | Per UNS N08811 composition |
| Tension test (RT) | E8 | Per heat/lot | 515 MPa UTS, 205 MPa YS, 30% elongation |
| Flattening test | B407 | Each tube | No cracking |
| Hydrostatic test | B407 | Each tube | No leakage at 60–80% of YS |
| Eddy current (optional alternative to hydrostatic) | E426 | Each tube | No defect signals |
Additional requirements for bright annealed tube:
| Test | Method | Frequency | Acceptance |
|---|---|---|---|
| Grain size | ASTM E112 | Per heat | ASTM No. 5 or coarser |
| Surface roughness (Ra) | Profilometer | Sample per lot | ≤ 0.8 µm (32 µin) typical |
| Visual inspection (bright finish) | Naked eye (with adequate lighting) | 100% | Uniform metallic appearance; no scale, discoloration, or pitting |
| Water break test | Immerse, observe | Sample per lot | Continuous water film; no beading |
| Ferroxyl test (iron contamination) | Ferroxyl solution | Sample per lot | No blue color |
| Dye penetrant (PT) | E165 | 100% (critical service) | No cracks or linear indications |
| PMI (Positive Material Identification) | XRF | 100% of tube ends | Within ±5% of specified composition |
Grain size verification (critical for 800HT):
For 800HT, the coarse grain structure (ASTM No. 5 or coarser) is essential for creep strength. Verification requires:
Sample preparation: Mount, grind, polish, and etch (electrolytic oxalic acid or glyceregia).
Examination per ASTM E112: Compare to standard charts or use intercept method.
Acceptance: Minimum ASTM No. 5 (64–128 µm average grain diameter).
Typical grain size report for bright annealed 800HT:
| Location | Grain Size (ASTM) | Intercept Count (grains/mm) |
|---|---|---|
| Tube ID surface | 5.5 | 90 |
| Tube OD surface | 5.0 | 85 |
| Mid-wall | 5.0 | 85 |
| Result | Pass (≥ No. 5) |
Surface finish requirements for bright annealed tube:
| Parameter | Typical Specification | Measurement Method |
|---|---|---|
| Ra (arithmetic average roughness) | ≤ 0.8 µm (32 µin) | Profilometer (stylus or optical) |
| Rz (average peak-to-valley) | ≤ 5.0 µm | Profilometer |
| Surface defects (scratches, dents) | Depth ≤ 0.05 mm | Visual with magnification |
| Discoloration | None (uniform metallic) | Visual |
| Pitting | None | Visual + dye penetrant |
Water break test procedure (for bright annealed surfaces):
Degrease the tube surface with a non-ionic detergent.
Rinse thoroughly with deionized water.
Immerse vertically in deionized water for 10–15 seconds.
Withdraw slowly and observe.
Interpretation:
Pass: Water film is continuous and drains uniformly.
Fail: Water beads or forms discrete droplets (indicates residual oil, grease, or scale).
Ferroxyl test procedure (iron contamination detection):
Solution preparation:
10 g potassium ferricyanide + 30 mL nitric acid (70%) + 100 mL distilled water.
Procedure:
Apply 2–3 drops of ferroxyl solution to the bright annealed surface.
Allow to react for 30–60 seconds.
Observe for color change.
Interpretation:
Pass: No color change or faint yellow (no free iron).
Fail: Blue color develops (free iron present; will cause pitting).
NDE requirements for large diameter tube:
| NDE Method | Extent | Acceptance Criteria |
|---|---|---|
| Ultrasonic (UT) – longitudinal defects | 100% | No echo amplitude > 50% of reference standard |
| Ultrasonic (UT) – transverse defects | 100% (when specified) | No echo amplitude > 50% of reference standard |
| Eddy current (ET) – surface defects | 100% (alternative to UT) | No defect signal > reference notch |
| Radiography (RT) – ends only | 50 mm from each end (when specified) | No cracks or inclusions |
Certification requirements for critical service:
| Certificate | Content | Required For |
|---|---|---|
| Mill Test Certificate (MTC) per EN 10204 3.1 | Chemical analysis, mechanical properties, heat treatment details | All orders |
| MTC per EN 10204 3.2 | Above + independent inspection body witness | Pressure vessels, ASME stamping |
| NDE reports | RT film, UT logs, PT reports | All critical service |
| PMI report | Alloy verification for each tube | Petrochemical, nuclear |
| Bright annealing certificate | Furnace atmosphere, temperature profile, cooling rate | High-purity applications |
| Surface finish certificate | Ra measurements, water break test, ferroxyl test | Bright annealed specification |
Example bright annealing certificate content:
| Parameter | Value |
|---|---|
| Furnace type | Horizontal roller hearth, hydrogen atmosphere |
| Annealing temperature | 1175 ± 10°C |
| Soak time | 30 minutes |
| Atmosphere | 100% H₂, dew point ≤ -60°C |
| Cooling method | Water-cooled section + forced H₂ convection |
| Cooling rate (800–500°C) | > 50°C/min |
| Date of heat treatment | [Date] |
| Operator signature | [Signature] |
Acceptance criteria for bright annealed surface (typical customer specification):
| Defect | Acceptance |
|---|---|
| Scale (any) | Not allowed |
| Discoloration (blue, purple, brown) | Not allowed |
| Pitting (any) | Not allowed |
| Scratches > 0.1 mm deep | Not allowed |
| Iron contamination (ferroxyl positive) | Not allowed |
| Water break failure | Not allowed |
| Ra > 0.8 µm | Not allowed |
Documentation package for large diameter bright annealed 800HT tube (critical service):
Cover page (mill name, PO number, heat numbers)
EN 10204 3.1 or 3.2 certificate
Chemical analysis (heat and product)
Tensile test results (RT, elevated temperature if specified)
Grain size report (ASTM E112, with micrographs)
Flattening and hydrostatic test reports
NDE reports (UT, PT, RT as applicable)
PMI report (each tube)
Bright annealing certificate (atmosphere, temperature, cooling)
Surface finish certificate (Ra, water break, ferroxyl)
Dimensional report (OD, wall, length, straightness)
Visual inspection report
Key takeaway for purchasers:
When ordering ASTM B407 Incoloy 800HT large diameter bright annealed tube for critical service, specify:
"Tube shall be manufactured per ASTM B407, Grade UNS N08811 (800HT), seamless, bright annealed in hydrogen atmosphere. Surface finish shall be bright, metallic, free of scale and discoloration. Surface roughness (Ra) shall not exceed 0.8 µm. Water break test and ferroxyl test shall be negative. Grain size shall be ASTM No. 5 or coarser per ASTM E112. 100% ultrasonic examination per ASTM E213. Certification per EN 10204 3.2 with independent witness."
This ensures that the tube will meet the demanding requirements of ethylene cracking, hydrogen reformer, or high-purity semiconductor service.
