Characteristics, Corrosion Resistance, and Applications of 09CrCuSb Straight Seam Steel Pipe

09CrCuSb straight seam steel pipe, as a type of steel resistant to sulfuric acid dew point corrosion, has significant application value in industries such as power, chemical, and metallurgy. The name of this steel originates from its chemical composition: 09 represents a carbon content ≤0.09%, with Cr, Cu, and Sb being its main alloying elements. This unique composition ratio gives it excellent corrosion resistance in sulfur-containing flue gas environments. 09CrCuSb straight seam steel pipe, manufactured using the straight seam welding process, has become a key material for equipment such as flue gas desulfurization systems and boiler air preheaters due to its stable quality and relatively low cost.

First, the material characteristics and corrosion resistance mechanism of 09CrCuSb straight seam steel pipe.
The core advantage of 09CrCuSb steel lies in its special resistance to sulfuric acid dew point corrosion. When sulfur in fuel burns, it forms sulfur dioxide, which, in low-temperature areas (such as chimneys and air preheaters), reacts with water vapor to form sulfuric acid dew, causing severe corrosion to ordinary carbon steel. 09CrCuSb steel forms a dense passivation film through the synergistic effect of alloying elements: copper promotes the formation of a stable protective layer on the steel surface, chromium improves the corrosion resistance of the substrate, and antimony further inhibits localized corrosion. Experimental data show that in a 50% sulfuric acid solution at 60℃, the corrosion rate of 09CrCuSb steel is only 1/5 to 1/8 that of ordinary Q235 steel, and its service life can be extended by more than 3 times.

Second, the production process and key technical points of 09CrCuSb straight seam steel pipes.
The production process of straight seam welded pipes includes key processes such as strip slitting, forming, welding, and sizing. For 09CrCuSb steel, the following aspects require special attention:
1. Slab control: A controlled rolling and cooling process (TMCP) is adopted to ensure the uniform distribution of elements such as copper and antimony, avoiding segregation. The thickness tolerance of hot-rolled coils must be controlled within ±0.2mm to ensure the quality of subsequent welding.
2. Welding process: High-frequency resistance welding (HFW) or submerged arc welding (SAW) is commonly used. During welding, the temperature of the heat-affected zone must be controlled between 900 and 1100℃ to avoid oxidation of alloying elements. Post-weld online heat treatment, such as induction annealing, is required to eliminate welding stress.
3. Non-destructive testing: 100% eddy current testing (ECT) and ultrasonic testing (UT) are essential to ensure the pipe body is defect-free, paying particular attention to cracks and lack of fusion in the weld area.

Third, Industry Applications and Typical Cases of 09CrCuSb Straight Seam Steel Pipes.
In the desulfurization system of thermal power plants, 09CrCuSb straight seam steel pipes are mainly used as components such as the GGH (flue gas heat exchanger) shell and flue expansion joints. A 600MW unit renovation project showed that after replacing traditional ND steel with 8mm thick 09CrCuSb straight seam steel pipes, the flue life increased from 2 years to 6 years, and maintenance costs decreased by 40%. In refinery sulfur recovery units, pipes made of this material can withstand corrosion from wet flue gas containing H₂S and SO₂, with a maximum operating temperature of 150℃. It is worth noting that its resistance to chloride ion corrosion is relatively weak; therefore, it needs to be used in conjunction with an anti-corrosion coating when applied in coastal power plants.

Fourth, Market Status and Development Trends of 09CrCuSb Straight Seam Steel Pipes. 
Major domestic manufacturers have achieved an annual production capacity of over 100,000 tons. According to a 2024 industry report, the price of 09CrCuSb straight seam steel pipes is 20%–30% higher than that of ordinary weathering steel, but its life-cycle cost advantage is significant. Current technological improvement directions include:
- Composite Process: Developing 09CrCuSb/carbon steel double-layer composite pipes to reduce material costs;
- Intelligent Production: Using laser vision-guided welding robots to control the weld defect rate below 0.1%;
- Green Standards: The newly revised GB/T 29732-2024 sets higher requirements for the recyclability of steel, prompting manufacturers to optimize alloy ratios.

Fifth, Recommendations and Precautions for the Use of 09CrCuSb Straight Seam Steel Pipes
1. Selection Guidance: For flue gas environments with flow velocities >15m/s, it is recommended to select steel pipes with a wall thickness ≥10mm to prevent erosion corrosion; in low-temperature environments (<60℃), the alloy content can be appropriately reduced to save costs.
2. Installation Specifications: ER55-CuSb welding wire must be used for welded joints to avoid electrochemical corrosion caused by welding dissimilar steels. The spacing between pipe supports should not exceed 80% of the standard value to prevent vibration wear.
3. Maintenance Strategy: During annual shutdown maintenance, the wall thinning of the steel pipe should be inspected with an endoscope, with a focus on monitoring the heat-affected zone of the weld. When the local corrosion depth exceeds 30% of the wall thickness, repair by overlay welding or partial replacement is required.

The technical maturity of 09CrCuSb straight seam steel pipes has been verified by engineering projects. However, with increasingly stringent environmental standards (such as SO₂ emission limits being reduced to 35mg/m³), it may be necessary to develop high-end variant materials containing Mo and Ni in the future. At the current stage, proper material selection, standardized construction, and scientific maintenance remain key to maximizing its performance advantages.