# Introduction to the JIS G3458 Alloy Steel Boiler Tube Standard Specifications
The JIS G3458 standard outlines the requirements for heat-resistant alloy steel pipes that serve as high-temperature fluid conduits in heaters and boiler tubes. This specification ensures that these pipes can withstand the extreme conditions of high temperatures and pressures typically encountered in industrial applications. Below is an overview of the production method, chemical composition, and mechanical properties for the various grades defined under this standard.
## Production Method
The production process for JIS G3458 alloy steel pipes involves specific heat treatments to ensure the material's mechanical properties and durability. These treatments include low-temperature annealing, isothermal annealing, full annealing, normalizing, and combinations thereof, often followed by tempering. The following table summarizes the heat treatment methods applicable to each grade:
| **Grade** | **Heat Treatment** |
|--------------|------------------------------------------------------------------------------------|
| STPA 12 | Low-temperature annealing, isothermal annealing, full annealing, normalizing, or normalizing followed by tempering. |
| STPA 20 | Same as STPA 12 |
| STPA 22 | Same as STPA 12 |
| STPA 23 | Low-temperature annealing, isothermal annealing, full annealing, or normalizing followed by tempering. |
| STPA 24 | Isothermal annealing, full annealing, or normalizing followed by tempering. |
| STPA 25 | Isothermal annealing, full annealing, or normalizing followed by tempering. |
| STPA 26 | Isothermal annealing, full annealing, or normalizing followed by tempering. |
These heat treatments play a crucial role in determining the final mechanical properties of the alloy steel pipes, ensuring they meet the demands of their intended applications.
## Chemical Composition
The chemical composition of the alloy steel directly impacts its performance and suitability for use in high-temperature environments. The following table provides the chemical composition ranges for each grade of the JIS G3458 standard:
| **Grade** | **C** | **Si** | **Mn** | **P** | **S** | **Cr** | **Mo** |
|--------------|--------------|--------------|--------------|--------------|--------------|--------------|--------------|
| STPA 12 | 0.10–0.20 | 0.10–0.50 | 0.30–0.80 | ≤0.035 | ≤0.035 | — | 0.45–0.65 |
| STPA 20 | 0.10–0.20 | 0.10–0.50 | 0.30–0.60 | ≤0.035 | ≤0.035 | 0.50–0.80 | 0.45–0.65 |
| STPA 22 | ≤0.15 | ≤0.50 | 0.30–0.60 | ≤0.035 | ≤0.035 | 0.80–1.25 | 0.45–0.65 |
| STPA 23 | ≤0.15 | 0.50–1.00 | 0.30–0.60 | ≤0.030 | ≤0.030 | 1.00–1.50 | 0.45–0.65 |
| STPA 24 | ≤0.15 | ≤0.50 | 0.30–0.60 | ≤0.030 | ≤0.030 | 1.90–2.60 | 0.87–1.13 |
| STPA 25 | ≤0.15 | ≤0.50 | 0.30–0.60 | ≤0.030 | ≤0.030 | 4.00–6.00 | 0.45–0.65 |
| STPA 26 | ≤0.15 | 0.25–1.00 | 0.30–0.60 | ≤0.030 | ≤0.030 | 8.00–10.00 | 0.90–1.10 |
The controlled levels of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S), chromium (Cr), and molybdenum (Mo) ensure the material's strength, toughness, and corrosion resistance.
## Mechanical Properties
The mechanical properties of JIS G3458 alloy steel pipes are critical for their functionality in high-pressure and high-temperature environments. The following table details the tensile strength, yield point, and elongation percentages for each grade:
| **Grade** | **Tensile Strength (kgf/mm²)** | **Yield Point or Proof Stress (kgf/mm²)** | **Elongation (%)** |
|--------------|---------------------------------|--------------------------------------------|-----------------------------------------------------------------------------------|
| **Test Piece Type** | Longitudinal | Transverse | Longitudinal | Transverse | Longitudinal | Transverse |
| STPA 12 | ≥39 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
| STPA 20 | ≥42 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
| STPA 22 | ≥42 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
| STPA 23 | ≥42 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
| STPA 24 | ≥42 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
| STPA 25 | ≥42 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
| STPA 26 | ≥42 | ≥21 | ≥30 | ≥25 | ≥24 | ≥19 |
These mechanical properties demonstrate the alloy steel's ability to maintain structural integrity under demanding conditions, making it suitable for critical applications such as boilers and heaters.
In conclusion, the JIS G3458 standard provides a comprehensive framework for manufacturing high-quality alloy steel pipes that can operate efficiently in high-temperature environments. The combination of precise chemical compositions and tailored heat treatments ensures that these pipes meet the stringent requirements of modern industrial applications.
MCV-03W Series Direction Valves
Mcv-03W Series Direction Valves,Stacked Check Valve,Hydraulic Stacked Check Valve,Stacked Check Valve Hydraulic
Shanghai Jinhai Hydraulic Co.,Ltd , https://www.shanghaijinhai.com