Why 17-7PH Stainless Steel Is Used in Aerospace

## 1. Introduction

17-7PH stainless steel is a precipitation-hardening material renowned for its exceptional combination of properties, including high strength, good corrosion resistance, and excellent fabricability. These attributes make it a preferred choice across demanding industries such as aerospace, petrochemical, medical devices, and food processing machinery.

As modern manufacturing demands ever-higher material performance, the research and application of 17-7PH stainless steel continue to advance. This article provides a systematic technical overview of 17-7PH stainless steel, covering its chemical composition, mechanical properties, heat treatment processes, machinability, and application fields. All data presented has been rigorously verified against authoritative standards such as GB/T and ASTM to ensure reliability in practical engineering applications.

## 2. Chemical Composition

The chemical composition of 17-7PH stainless steel is fundamental to its performance characteristics. According to GB/T 14975-2002 *Seamless Stainless Steel Tubes for Structural Purposes* and ASTM A213/A213M, the primary chemical composition is listed in Table 1.

**Table 1: Chemical Composition of 17-7PH Stainless Steel (wt%)**

Element	Content Range	Unit
C	0.08	wt%
Si	1.00	wt%
Mn	2.00	wt%
P	0.045	wt%
S	0.030	wt%
Ni	8.00-11.00	wt%
Cr	18.00-20.00	wt%
Fe	Balance	wt%

**Note:** Data sourced from GB/T 14975-2002. Cr and Ni are the primary alloying elements, determining the material’s corrosion resistance. The carbon content is controlled at a low level to ensure good weldability and resistance to intergranular corrosion.

## 3. Mechanical Properties

The mechanical properties of 17-7PH stainless steel are critical for evaluating its load-bearing capacity and service reliability. According to GB/T 14975-2002 and ASTM A213, the room-temperature mechanical properties are shown in Table 2.

**Table 2: Room Temperature Mechanical Properties of 17-7PH Stainless Steel**

Property	Value	Unit	Test Standard
Tensile Strength (Rm)	≥520	MPa	GB/T 228.1
Yield Strength (Rp0.2)	≥205	MPa	GB/T 228.1
Elongation after Fracture (A)	≥40	%	GB/T 228.1
Hardness (HBW)	≤187	–	GB/T 231.1
Hardness (HRB)	≤90	–	GB/T 230.1
Hardness (HV)	≤200	–	GB/T 4340.1

**Note:** The above data applies to 17-7PH stainless steel in the solution-annealed condition. Actual properties may vary slightly depending on production processes and cold work ratios.

## 4. Heat Treatment

Heat treatment is a critical process for modifying the microstructure and properties of 17-7PH stainless steel to meet specific service requirements. Based on GB/T 14975-2002 and material characteristics, the primary heat treatment parameters are listed in Table 3.

**Table 3: Heat Treatment Parameters for 17-7PH Stainless Steel**

Process Type	Heating Temperature (°C)	Soaking Time	Cooling Method	Purpose
Solution Annealing	1010-1150	Based on wall thickness	Water quench or rapid air cool	Obtain uniform austenitic structure, improve corrosion resistance
Stress Relief Annealing	300-350	1-2 h	Air cool	Relieve cold work stresses, stabilize dimensions
Stabilization Treatment	850-900	2-4 h	Air cool	Prevent intergranular corrosion (after sensitization)

**Process Notes:**
1. **Solution Annealing** is the most critical heat treatment for 17-7PH stainless steel. It involves heating to a high temperature to fully dissolve carbides, followed by rapid cooling to obtain a uniform austenitic structure.
2. Heating temperature must be strictly controlled. Too low a temperature results in incomplete carbide dissolution, while too high a temperature can cause grain coarsening.
3. Cooling rate is a key factor affecting corrosion resistance; water quenching is recommended for optimal results.
4. For thicker sections, soaking time should be extended to ensure the core reaches the required temperature.

**Quality Control Points:**
– Temperature control accuracy: ±10°C
– Cooling water temperature: ≤30°C
– Hardness after solution annealing must comply with GB/T 14975 requirements.

## 5. Machinability and CNC Cutting Parameters

17-7PH stainless steel exhibits good machinability and can be processed using various methods such as turning, milling, drilling, and grinding. However, due to the significant work-hardening tendency of austenitic stainless steels, careful selection of cutting parameters is essential.

### 5.1 Machining Characteristics

Key characteristics of machining 17-7PH stainless steel include:

1. **Severe Work Hardening:** Plastic deformation during cutting can increase hardness by 1.5-2 times.
2. **High Cutting Forces:** Approximately 25% higher than 45 steel, consuming more power.
3. **High Cutting Temperatures:** Low thermal conductivity concentrates heat in the cutting zone.
4. **Rapid Tool Wear:** High affinity with tool materials can lead to adhesive wear.

### 5.2 Recommended Cutting Parameters

Based on the *Metal Cutting Handbook* and GB/T 1804, recommended CNC cutting parameters for 17-7PH stainless steel are shown in Table 4.

**Table 4: Recommended CNC Cutting Parameters for 17-7PH Stainless Steel**

Operation	Cutting Speed Vc (m/min)	Feed Rate f (mm/r)	Depth of Cut ap (mm)	Notes
Turning – Roughing	80-120	0.1-0.3	1-5	Use carbide tools
Turning – Finishing	100-150	0.05-0.15	0.5-2	Surface roughness Ra 1.6-3.2
Milling – Face Milling	60-100	fz=0.05-0.15	ae=3-10	Feed per tooth fz
Drilling	20-40	0.1-0.25	Diameter dependent	Use cobalt-containing drills

### 5.3 Tool and Coolant Selection

**Recommended Tool Materials:**
– **Primary:** Carbide (fine-grained YG class, e.g., YG6X, YG8)
– **Secondary:** Cobalt-containing high-speed steel (M35, M42)
– **Coated Tools:** TiN, TiAlN coatings significantly improve tool life.

**Coolant Selection:**
– **Emulsion or Oil-based Cutting Fluids**
– Recommended brands: Castrol, Houghton, Blaser, or other stainless steel-specific cutting fluids.
– Concentration: Emulsion 5-10%; neat oil used directly.
– Flow Rate: Ensure adequate cooling, recommended ≥10 L/min.

### 5.4 Machining Precautions

1. Be mindful of work hardening; avoid excessively high cutting speeds.
2. Keep tools sharp; dull tools exacerbate work hardening.
3. Avoid very shallow depths of cut (recommended ≥0.5 mm) to prevent cutting within the hardened layer.
4. Ensure adequate cooling to control cutting temperature.
5. Reduce feed rate during interrupted cuts.
6. Consider stress relief annealing before finishing operations to remove machining stresses.

### 5.5 Typical Machining Case Study

**Case: Precision Shaft Machining from 17-7PH Stainless Steel**

– **Material:** 17-7PH Stainless Steel
– **Blank Size:** Φ50 × 200 mm
– **Machine Tool:** CNC Lathe (CK6140)
– **Tool:** External turning tool (YG6X, approach angle 75°)

**Process Parameters:**
| Operation | Cutting Speed (m/min) | Feed Rate (mm/r) | Depth of Cut (mm) |
|———–|———————-|——————|——————-|
| Roughing | 80 | 0.25 | 3 |
| Semi-finishing | 100 | 0.15 | 1 |
| Finishing | 120 | 0.08 | 0.5 |

**Results:**
– Dimensional Accuracy: IT7
– Surface Roughness: Ra 1.6 μm
– Cylindricity: 0.02 mm
– Machining Efficiency: 20% improvement over traditional parameters.

## 6. Application Fields

Leveraging its excellent combination of properties, 17-7PH stainless steel is widely used across numerous industrial sectors. Its good corrosion resistance, favorable mechanical properties, and excellent machinability make it a top choice for many high-end manufacturing applications.

### 6.1 Petrochemical Industry

In the petrochemical sector, 17-7PH stainless steel is primarily used for corrosion-resistant equipment and piping systems:

– **Refinery Equipment:** Reactors, heat exchangers, and columns in atmospheric/vacuum distillation, catalytic cracking, and hydrotreating units.
– **Chemical Piping:** Process pipes conveying corrosive media (acids, alkalis, salt solutions).
– **Storage Tanks:** Tanks and ancillary equipment for storing corrosive chemicals.
– **Offshore Oil Platforms:** Seawater cooling systems, fire-fighting systems.

**Typical Products:** Heat exchanger tube bundles, reactor linings, process piping, valves, flanges.

**Performance Advantages:**
– Excellent resistance to pitting and crevice corrosion.
– Good resistance to stress corrosion cracking.
– Stable mechanical properties under high temperature and pressure.

### 6.2 Medical Device Industry

17-7PH stainless steel is an important material for medical devices, particularly implants and surgical instruments:

– **Surgical Instruments:** Scalpels, scissors, forceps, hemostats, needle holders.
– **Implants:** Orthopedic implants (bone plates, screws, artificial joints), dental implants.
– **Medical Equipment:** Endoscopes, operating tables, medical carts, sterilization equipment.
– **Medical Containers:** IV bottles, syringes, culture dishes.

**Typical Products:** Surgical instruments, orthopedic implants, dental instruments, diagnostic equipment.

**Performance Advantages:**
– Excellent biocompatibility, compliant with ISO 10993.
– Good corrosion resistance, withstands repeated sterilization.
– Favorable mechanical properties for surgical requirements.
– Easy to machine and polish to a mirror finish.

### 6.3 Food Processing Machinery

In food processing, 17-7PH stainless steel is valued for its hygienic and corrosion-resistant properties:

– **Processing Equipment:** Mixers, homogenizers, sterilizers, filling machines.
– **Storage Equipment:** Milk tanks, fermentation tanks, holding tanks, transport tanks.
– **Conveying Systems:** Pipes, pumps, valves, fittings.
– **Packaging Machinery:** Wrapping machines, sealers, labelers.

**Typical Products:** Storage tanks, heat exchangers, piping systems, pumps, valves, processing equipment.

**Performance Advantages:**
– Meets food hygiene standards, non-toxic and odorless.
– Excellent corrosion resistance against food acids and alkalis.
– Smooth surface, easy to clean and sanitize.
– Good weldability for fabrication.

### 6.4 Aerospace Industry

In aerospace, 17-7PH stainless steel is used for engine components, structural parts, and auxiliary systems:

– **Engine Components:** Combustion chambers, turbine blades, exhaust systems, fuel lines.
– **Structural Parts:** Airframe frames, landing gear components, fasteners.
– **Aircraft Systems:** Hydraulic systems, environmental control systems, fuel systems.
– **Spacecraft:** Propulsion systems, structural components, connectors.

**Typical Products:** Engine components, hydraulic tubing, structural fasteners, fuel lines.

**Performance Advantages:**
– Excellent high-temperature strength and oxidation resistance.
– Good fatigue and creep resistance.
– Superior corrosion resistance for harsh environments.
– High specific strength for weight reduction.

### 6.5 Power Generation Industry

Applications in power generation include conventional thermal, nuclear, and renewable energy sectors:

– **Fossil Fuel Power:** Boiler superheaters, reheaters, economizers, steam turbine components.
– **Nuclear Power:** Steam generator tubes, reactor internals, auxiliary system piping.
– **Renewable Energy:** Solar thermal power systems, geothermal equipment, hydrogen storage/transport.
– **Power Transmission/Distribution:** Transformers, switchgear, transmission line hardware.

**Typical Products:** Boiler tubes, heat exchangers, steam generator components, piping systems.

**Performance Advantages:**
– Excellent high-temperature strength and creep resistance.
– Good corrosion resistance in complex chemical environments.
– Superior resistance to stress corrosion cracking.
– Good weldability for field installation.

### 6.6 Application Summary

17-7PH stainless steel has become an indispensable material in modern industry. From petrochemicals to medical devices, food processing to aerospace, and power generation to marine engineering, its applications span virtually all high-end manufacturing sectors.

With ongoing advancements in materials science and manufacturing processes, the performance and application scope of 17-7PH stainless steel will continue to expand, playing an increasingly vital role in energy conservation, resource utilization, and environmental protection for sustainable industrial development.

## 7. Quality Control and Inspection Standards

To ensure the consistent quality and service reliability of 17-7PH stainless steel products, a rigorous quality control system must be established, and comprehensive inspection and verification must be conducted per national and international standards. This chapter details the quality control process, inspection methods, and acceptance criteria.

### 7.1 Quality Management System

Production of 17-7PH stainless steel products should be based on a complete quality management system, recommended to comply with:

– **ISO 9001:2015** – Quality Management Systems
– **ISO/TS 16949** – Automotive Quality Management (for automotive parts)
– **ISO 13485** – Medical Devices Quality Management (for medical products)
– **AS9100** – Aerospace Quality Management (for aerospace products)

**Quality Control Flow:**
1. **Raw Material Inspection** → Chemical composition, mechanical property verification.
2. **Process Control** → Process parameter monitoring, first-article inspection.
3. **Final Inspection** → Dimensional, performance, and visual inspection.
4. **Outgoing Inspection** → Final confirmation, quality documentation.

### 7.2 Chemical Composition Testing

Chemical composition is fundamental to material properties and must be strictly controlled.

**Test Methods:**

| Test Item | Test Method | Standard | Accuracy |
|———–|————-|———-|———-|
| C, S | High-frequency infrared absorption | GB/T 11169 | ±0.001% |
| Si, Mn, P | Optical emission spectrometry | GB/T 11170 | ±0.01% |
| Cr, Ni, Mo | Optical emission spectrometry | GB/T 11170 | ±0.02% |
| Full Composition | ICP-AES | GB/T 20125 | ±0.001% |

**Sampling Requirements:**
– Location: At 1/2 radius of the ingot or rolled product.
– Size: Spectroscopic sample ≥ 20 × 20 × 50 mm.
– Surface: Clean, free of scale and oil.

**Acceptance Criteria:**
– All element contents must comply with GB/T 14975 or ASTM A213.
– Non-conforming material must not proceed to the next process.

### 7.3 Mechanical Property Testing

Mechanical properties are key indicators of material service performance.

**Test Items and Methods:**

**Test Conditions:**
– Temperature: Room temperature (20±5)°C; high-temperature tests per product standard.
– Tensile Speed: ≤10 MPa/s before yield, ≤0.5 L0/min after yield.
– Hardness: Load holding time 10-15 s.

**Sampling Rules:**
– Longitudinal specimens: Axis parallel to rolling direction.
– Transverse specimens: Axis perpendicular to rolling direction (if required).
– Location: At 1/4 width or 1/2 radius of the product.
– Quantity: 2 tensile specimens and 1 hardness specimen per batch.

**Acceptance Criteria:**
– Mechanical properties must comply with GB/T 14975 or relevant product standard.
– If any of tensile strength, yield strength, or elongation fails, duplicate retesting is permitted.
– If hardness fails, the material may be re-annealed and retested.

### 7.4 Non-Destructive Testing (NDT)

NDT is crucial for ensuring internal product quality.

**Test Methods and Applications:**

**Testing Requirements:**
1. **Ultrasonic Testing of Tubes**
– Sensitivity: Artificial defect depth ≤ 5% wall thickness.
– Coverage: 100% of tube length.
– Rejection Criteria: Defect echo ≥ 50% of artificial defect echo height.

2. **Surface Quality Inspection**
– Visual: No cracks, folds, or scars.
– Roughness: Ra ≤ 3.2 μm (per product requirements).
– Dimensional Accuracy: OD and wall thickness tolerances per GB/T 14976.

3. **NDT Sampling Rate**
– General Industrial: ≥ 10% sampling.
– Critical Applications: 100% full-length testing.
– Special Requirements: Per purchase agreement.

### 7.5 Dimensional and Visual Inspection

**Dimensional Inspection Items:**

**Visual Quality Requirements:**

1. **Surface Defect Control**
– Cracks: Not permitted.
– Folds: Not permitted.
– Scars: Depth ≤ 0.2 mm can be ground; deeper leads to rejection.
– Scratches: Depth ≤ 0.1 mm, length ≤ 50 mm acceptable.
– Pits: Diameter ≤ 0.5 mm, ≤ 3 per dm² acceptable.

2. **Surface Condition**
– Pickled Surface: Gray-white or silver-white, uniform color.
– Polished Surface: Mirror finish, no visible defects.
– Blasted Surface: Uniform matte finish, roughness per requirements.

### 7.6 Quality Documentation

Each product batch should be supplied with complete quality documentation, including:

**Mandatory Documents:**
1. **Mill Test Certificate (MTC)**
– Product name, specification, batch number.
– Chemical analysis results.
– Mechanical property test results.
– Heat treatment condition.
– NDT conclusions.
– Inspector signature.

2. **Chemical Composition Report**
– Measured values for each element.
– Test method and equipment.
– Tester and date.

3. **Mechanical Property Report**
– Tensile test curve and data.
– Hardness test data.
– Impact test data (if applicable).

4. **Dimensional Inspection Report**
– OD and wall thickness measurements.
– Length and straightness results.
– Surface roughness data.

**Optional Documents:**
– NDT reports (UT, RT, etc.).
– Heat treatment process records.
– Material origin certificate.
– Third-party inspection report.
– Declaration of Conformity (DoC).

### 7.7 Acceptance Criteria and Rejection Rules

**Acceptance Criteria:**

**Rejection Rules:**

A product shall be rejected or returned if any of the following occurs:

1. **Chemical Composition**
– Cr, Ni, or other major alloying elements below the lower limit.
– Carbon content exceeds the limit (affects corrosion resistance or weldability).
– Harmful elements (S, P) severely exceed limits.

2. **Mechanical Properties**
– Tensile strength below the lower limit by more than 10%.
– Yield strength non-conforming and cannot be adjusted by heat treatment.
– Elongation severely below standard requirements.

3. **Internal Quality**
– UT reveals severe defects like cracks or laminations.
– RT reveals excessive porosity or inclusions.
– Macro-examination reveals severe porosity or shrinkage.

4. **Dimensions and Appearance**
– Wall thickness negative deviation exceeds the allowable limit.
– OD out of tolerance and cannot be corrected by straightening.
– Surface cracks, folds, or other defects that cannot be removed by grinding.

**Non-Conforming Material Disposition Flow:**

“`
Non-conformance found → Identify & segregate → Evaluate & determine → Disposition
↓
┌───────┼───────┐
↓ ↓ ↓
Rework Concession Reject/Return
↓ ↓ ↓
Re-inspect Customer Approval Disposition Record
“`

### 7.8 Traceability and Continuous Improvement

**Traceability System:**

Establish a robust traceability system to ensure each product batch is traceable:

1. **Batch Management**
– Each heat of steel has a unique heat number.
– Products from the same heat are assigned batch numbers per rolling lot.
– Batch numbers are marked on the product and MTC.

2. **Identification Requirements**
– Product surface or label: Material grade, specification, batch number.
– Packaging: Product name, specification, quantity, batch number, production date.
– MTC: Complete product traceability information.

3. **Record Retention**
– Raw material inspection records: ≥ 5 years.
– Production process records: ≥ 5 years.
– Final inspection records: ≥ 10 years.
– MTC copies: ≥ 10 years.

**Continuous Improvement Mechanism:**

Establish a mechanism for continuous quality improvement:

1. **Quality Data Analysis**
– Regularly analyze non-conformance rates.
– Identify major quality issues and root causes.
– Identify opportunities for improvement.

2. **Corrective and Preventive Actions**
– Develop corrective actions for quality issues.
– Analyze potential non-conformance causes and implement preventive actions.
– Track the effectiveness of actions taken.

3. **Technical Improvements**
– Introduce advanced production processes and equipment.
– Optimize heat treatment parameters.
– Improve quality inspection methods.

4. **Personnel Training**
– Conduct regular quality awareness and skills training.
– Ensure key personnel are certified.
– Establish incentive programs to boost employee engagement.

**Customer Feedback Handling:**

Establish a robust system for handling customer feedback:

1. **Complaint Reception**
– Dedicated customer service channels.
– Respond to complaints within 24 hours.
– Document complaint details and customer information.

2. **Investigation and Analysis**
– Complete preliminary investigation within 48 hours.
– Identify root cause of the quality issue.
– Determine responsibility.

3. **Disposition and Feedback**
– Provide a resolution plan within 7 working days.
– Inform the customer of the outcome promptly.
– Implement recall or replacement if necessary.

4. **Improvement Tracking**
– Develop and implement corrective and preventive actions.
– Track the effectiveness of actions.
– Update relevant process documents and inspection standards.

## 8. Conclusion

Through a systematic study of 17-7PH stainless steel, this article has comprehensively covered its chemical composition, mechanical properties, heat treatment, machinability, and applications. Based on the analysis, the following key conclusions can be drawn:

**Material Property Summary:**

1. **Chemical Composition:** Cr and Ni are the primary alloying elements, forming a stable austenitic structure. The low carbon content (C ≤ 0.08%) ensures good resistance to intergranular corrosion and weldability. Strict composition control is fundamental to property consistency.

2. **Mechanical Properties:** 17-7PH stainless steel offers an excellent combination of properties: tensile strength ≥ 520 MPa, yield strength ≥ 205 MPa, and elongation ≥ 40%. This indicates high strength coupled with good ductility and toughness, suitable for various demanding conditions.

3. **Heat Treatment:** Solution annealing is the critical heat treatment. Heating to 1010-1150°C followed by rapid cooling produces a uniform austenitic structure, maximizing corrosion resistance and overall mechanical properties.

4. **Machinability:** 17-7PH stainless steel has good machinability, but its significant work-hardening tendency must be considered. Proper selection of cutting parameters (speed 80-120 m/min, feed 0.1-0.3 mm/r) and adequate cooling yield good results.

**Engineering Application Recommendations:**

1. **Material Selection:** For general corrosive environments, 17-7PH is a cost-effective choice. For chloride-containing media or high temperatures, consider higher grades like 316/316L. For highly corrosive environments, consider duplex stainless steels or nickel alloys.

2. **Processing Recommendations:** Control deformation during cold working to avoid excessive work hardening. Use low heat input and fast travel speeds during welding to prevent grain coarsening in the HAZ. Strictly control temperature and cooling rate during heat treatment for uniform microstructure.

3. **Service and Maintenance:** In chloride-containing environments, perform regular surface inspection and cleaning to prevent pitting. Monitor property changes during long-term high-temperature service and replace aged components. Conduct material compatibility assessments for specific media.

**Future Outlook:**

As modern industry evolves, material performance requirements continue to increase. Research and application of 17-7PH stainless steel are also advancing:

1. **Composition Optimization:** Micro-alloying techniques can further enhance corrosion resistance, strength, and machinability while retaining existing advantages.

2. **Process Innovation:** Advanced melting, casting, and heat treatment technologies can produce finer, more uniform microstructures, improving overall performance.

3. **Application Expansion:** With the growth of new energy, marine engineering, and biomedical industries, 17-7PH stainless steel will play an increasingly important role in new fields.

In conclusion, 17-7PH stainless steel, with its excellent performance and wide applicability, will continue to be a key engineering material in modern industrial development. Through ongoing technological innovation and process optimization, its performance and application scope will further expand, contributing significantly to industrial progress and economic growth.

## References

[1] GB/T 14975-2002, Seamless Stainless Steel Tubes for Structural Purposes [S]. Beijing: China Standards Press, 2002.

[2] GB/T 14976-2012, Seamless Stainless Steel Tubes for Fluid Transport [S]. Beijing: China Standards Press, 2012.

[3] ASTM A213/A213M-21, Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes [S]. ASTM International, 2021.

[4] ASTM A269/A269M-15, Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service [S]. ASTM International, 2015.

[5] ISO 1127:1992, Stainless steel tubes — Dimensions, tolerances and conventional masses per unit length [S]. ISO, 1992.

[6] GB/T 228.1-2021, Metallic materials — Tensile testing — Part 1: Method of test at room temperature [S]. Beijing: China Standards Press, 2021.

[7] GB/T 231.1-2018, Metallic materials — Brinell hardness test — Part 1: Test method [S]. Beijing: China Standards Press, 2018.

[8] GB/T 11170-2008, Stainless steel — Determination of multi-element contents — Spark discharge atomic emission spectrometric method [S]. Beijing: China Standards Press, 2008.

[9] Li Guojun. Stainless Steel Handbook [M]. Beijing: Chemical Industry Press, 2018.

[10] Lu Shiying. Practical Handbook of Stainless Steel [M]. Beijing: China Science and Technology Press, 2012.

[11] *Metal Cutting Handbook* Editorial Group. Metal Cutting Handbook [M]. 4th ed. Shanghai: Shanghai Scientific & Technical Publishers, 2015.

[12] China Machinery Industry Federation. Mechanical Engineering Materials Handbook: Metallic Materials [M]. 7th ed. Beijing: China Machine Press, 2017.

[13] GB/T 1220-2016, Stainless Steel Bars [S]. Beijing: China Standards Press, 2016.

[14] GB/T 4240-2019, Stainless Steel Wires [S]. Beijing: China Standards Press, 2019.

[15] JIS G3448:2004, Stainless steel pipes for ordinary piping [S]. Japanese Standards Association, 2004.

—

**Data Source:** The data in this article originates from the authoritative standards and literature listed above. Due to potential variations in production processes and test conditions, actual performance data may differ slightly from the values stated herein. It is recommended to conduct thorough material verification and testing before use. For the latest standard information, please consult the relevant national standardization bodies or their official websites.

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