GB 20G Pressure Vessel Steel: Properties, Uses & Manufacturing Guide

If you work on Chinese medium-pressure, medium-temperature projects—like industrial boilers, chemical storage vessels, or municipal pressure tanks—you need a steel that meets China’s GB/T 713 standard for reliability and cost-effectiveness. GB 20G pressure vessel steel is the go-to solution: as a carbon-manganese steel tailored for pressure service, its balanced strength, weldability, and affordability make it ideal for China’s industrial infrastructure. This guide breaks down its properties, real-world applications, manufacturing process, and material comparisons to help you solve mid-range pressure equipment challenges.

1. Material Properties of GB 20G Pressure Vessel Steel

GB 20G’s performance comes from its optimized carbon-manganese composition and strict quality control—engineered to handle medium temperatures (up to 450 °C) and pressures (up to 8,000 psi) while remaining easy to fabricate. Let’s explore its key properties in detail.

1.1 Chemical Composition

GB 20G adheres to China’s GB/T 713 standard, with elements controlled to avoid brittleness and ensure compatibility with domestic manufacturing processes. Below is its typical composition (for plates ≤ 60 mm thick):

1.2 Physical Properties

These traits make GB 20G suitable for China’s diverse industrial environments:

• Density: 7.85 g/cm³ (consistent with carbon steels)—simplifies weight calculations for large vessels (e.g., 15-meter diameter storage tanks)
• Melting Point: 1,420 – 1,460 °C (2,588 – 2,660 °F)—compatible with domestic welding processes (MIG, TIG, submerged arc welding)
• Thermal Conductivity: 45.0 W/(m·K) at 20 °C—ensures even heat distribution in boilers, reducing thermal stress in cyclic use
• Coefficient of Thermal Expansion: 11.7 × 10⁻⁶/°C (20 – 100 °C)—minimizes expansion/contraction damage in China’s seasonal temperature shifts (e.g., -20 °C to 35 °C)
• Magnetic Properties: Ferromagnetic—enables non-destructive testing (NDT) like magnetic particle inspection to detect hidden weld defects.

1.3 Mechanical Properties

GB 20G’s mechanical performance meets GB/T 713 requirements for medium-pressure service. Below are typical values:

1.4 Other Properties

GB 20G’s traits solve key challenges for Chinese industrial projects:

• Weldability: Excellent—even novice welders can join it without preheating (saves time on rural construction sites with limited equipment)
• Formability: Good—can be bent into curved boiler shells or tank walls (common in Chinese small-to-medium factories) without losing strength
• Corrosion Resistance: Moderate—resists water and mild chemicals; for harsh conditions (e.g., coastal Guangdong), add epoxy coatings or zinc plating
• Ductility: High—absorbs sudden pressure spikes (e.g., in chemical reactors) without fracturing, a key safety feature for Chinese industrial sites
• Toughness: Reliable—maintains strength at 0 °C, suitable for cold regions like Heilongjiang and Inner Mongolia.

2. Applications of GB 20G Pressure Vessel Steel

GB 20G’s versatility and GB compliance make it a staple in China’s industrial sector. Here are its key uses:

• Pressure Vessels: Medium-pressure chemical reactors and gas cylinders (≤ 8,000 psi)—compliant with China’s GB 150 pressure vessel standard.
• Boilers: Industrial boilers for factories and district heating systems—tolerates temperatures up to 450 °C, perfect for China’s northern winter heating needs.
• Storage Tanks: Large oil, water, and chemical storage tanks—its formability allows for seamless curved walls, and its low cost fits budget-conscious projects.
• Petrochemical Plants: Low-to-medium pressure process equipment like heat exchangers and small distillation columns—resists mild chemical corrosion and cyclic temperatures.
• Industrial Equipment: Hydraulic reservoirs and compressor housings—used in China’s manufacturing hubs (e.g., Guangdong, Jiangsu) for reliable pressure containment.
• Construction and Infrastructure: Municipal water pressure tanks and wastewater treatment reactors—affordable for public projects in small-to-medium cities.

3. Manufacturing Techniques for GB 20G Pressure Vessel Steel

Producing GB 20G requires strict compliance with GB/T 713 to ensure compatibility with Chinese industrial needs. Here’s the step-by-step process:

1. Steelmaking:
   • GB 20G is made using an Electric Arc Furnace (EAF) (aligns with China’s “dual carbon” goals, recycling scrap steel) or Basic Oxygen Furnace (BOF). Workers control carbon (0.17–0.24%) and manganese (0.35–0.65%) to meet GB standards.
2. Rolling:
   • The steel is Hot Rolled (1,100 – 1,200 °C) into plates of varying thicknesses (6 mm to 100+ mm). Hot rolling refines the grain structure, enhancing toughness for medium-temperature service.
3. Heat Treatment (Optional Normalization):
   • For thick plates (> 30 mm) or cold-climate projects: Plates are heated to 880 – 920 °C, held for 30–60 minutes, then air-cooled. This process uniformizes the microstructure and boosts impact toughness.
4. Machining & Finishing:
   • Plates are cut with plasma or laser tools to fit vessel sizes. Workers drill holes for nozzles and manholes, then grind edges smooth for tight welds (no leaks allowed, per GB 150).
5. Surface Treatment:
   • Coating: To protect against Chinese environmental conditions:
     • Epoxy Liners: For chemical tanks—resists acids and alkalis for 15+ years, compliant with China’s environmental regulations.
     • Zinc Plating: For coastal projects (e.g., Zhejiang, Fujian)—stops saltwater corrosion from the East China Sea.
     • CRA Cladding: For sour gas equipment—adds a thin stainless steel layer (e.g., 304L) to prevent sulfide stress cracking.
   • Painting: For boilers and outdoor tanks—uses cold-flexible, weather-resistant paint that remains durable at -20 °C (for Northern China).
6. Quality Control:
   • Chemical Analysis: Use spectrometry (per GB/T 223) to verify element levels.
   • Mechanical Testing: Tensile, impact (at 0 °C), and hardness tests on every heat of steel (GB/T 228.1, GB/T 229).
   • NDT: Ultrasonic testing (100% of plate area) finds internal defects; radiographic testing checks all welds (per GB/T 11345).
   • Hydrostatic Testing: Finished vessels are filled with water and pressed to 1.5× their design pressure for 30–60 minutes—no leaks mean they pass GB 150 standards.

4. Case Studies: GB 20G in Action

Real Chinese projects demonstrate GB 20G’s reliability in medium-pressure applications.

Case Study 1: Industrial Boiler (Heilongjiang, China)

A textile factory in Harbin needed a boiler to generate steam for production and heat for winter (ambient temperature -20 °C). They chose GB 20G plates (12 mm thick, normalized) for its weldability and cold toughness. The boiler operates at 400 °C and 4,000 psi daily. After 7 years, it has no cracks or corrosion—even in Harbin’s harsh winters. The factory saved 25% on material costs vs. using alloy steel.

Case Study 2: Chemical Storage Tank (Jiangsu, China)

A chemical company in Suzhou needed a 10-meter diameter tank to store 300,000 liters of dilute sulfuric acid. They used GB 20G plates (10 mm thick) with an epoxy liner for corrosion protection. The tank was fabricated on-site in 2 weeks and has operated for 5 years with zero leaks. This project saved the company ¥500,000 vs. using stainless steel.

5. GB 20G vs. Other Materials

How does GB 20G compare to other pressure vessel steels, including international and Chinese grades?

Yigu Technology’s Perspective on GB 20G

At Yigu Technology, GB 20G is our top recommendation for Chinese medium-pressure, medium-temperature projects. It meets GB/T 713 and GB 150 standards, making it fully compatible with domestic industrial needs—from Northern China’s cold boilers to Southern China’s chemical tanks. We supply custom-thickness plates (6–100 mm) with epoxy, zinc, or CRA treatments, tailored to regions (e.g., Heilongjiang projects get normalized plates for cold toughness). For clients transitioning from low-grade steels, GB 20G offers the right balance of performance and cost, avoiding the premium of alloy or stainless steels.

FAQ About GB 20G Pressure Vessel Steel

1. Can GB 20G be used for sour gas pressure vessels in China?
   Yes—with extra protection. Add a CRA cladding (e.g., 316L stainless steel) or thick epoxy liner to resist sulfide stress cracking. Ensure the steel’s sulfur content is ≤ 0.025% (meets China’s GB/T 713 sour service requirements).
2. What’s the maximum temperature GB 20G can handle?
   GB 20G safely operates at temperatures up to 450 °C for long-term service. For temperatures above 450 °C (e.g., large power plant boilers), choose GB 15CrMoR (alloy steel) which offers better creep resistance.
3. Is GB 20G compatible with Chinese welding standards?
   Yes—fully compatible with China’s GB/T 985 (welding procedures) and GB/T 5117 (carbon steel electrodes). Most domestic fabricators are familiar with welding GB 20G, reducing on-site construction time and costs.