Performance, Corrosion Resistance, and Weldability of 07Cr25Ni21 Seamless Stainless Steel Pipe

07Cr25Ni21 seamless stainless steel pipe, as a high-performance special steel, plays a crucial role in many industrial fields. In particular, its unique material properties and wide range of applications make it an indispensable material in numerous engineering projects.

Details of 07Cr25Ni21 Seamless Stainless Steel Pipe

Production methods include: cold-rolled seamless steel pipe, cold-drawn seamless steel pipe, heat treatment + rinsing delivery.

Chemical composition %: Nickel: 19.00~22.00, Chromium: 24.00～26.00, Silicon ≤0.75, Manganese: ≤2.00, Carbon: 0.040~0.10, Sulfur: ≤0.015, Phosphorus: ≤0.030

First, the chemical composition and physical properties of the 07Cr25Ni21 seamless stainless steel pipe

07Cr25Ni21 stainless steel, according to its chemical composition, mainly contains about 25% chromium and 21% nickel, and may also contain small amounts of carbon, silicon, manganese, phosphorus, and sulfur. The high content of chromium and nickel gives this stainless steel excellent corrosion resistance and high-temperature strength. Chromium forms a dense oxide film on the surface of steel, effectively preventing corrosion from oxygen and other corrosive media, while nickel enhances the structural stability of the steel and improves its creep resistance at high temperatures.

In terms of physical properties, 07Cr25Ni21 stainless steel has high density, good thermal conductivity, and a low coefficient of linear expansion. Its density is approximately 8.0 g/cm³, meaning that for the same volume, it is heavier than some other stainless steels, but this also results in better wear resistance. Good thermal conductivity makes this material perform excellently in heat exchange equipment, while the low coefficient of linear expansion ensures dimensional stability in both high and low temperature environments.

Second, the corrosion resistance and weldability of 07Cr25Ni21 seamless stainless steel pipes.

07Cr25Ni21 stainless steel is renowned for its excellent corrosion resistance, especially in both oxidizing and reducing media. While its corrosion resistance is slightly inferior to some super stainless steels in chloride-containing environments, it is sufficient for most conventional chemical media. Furthermore, this material exhibits good corrosion resistance to organic acids such as nitric acid and acetic acid, making it suitable for manufacturing chemical containers and pipelines.

Regarding weldability, 07Cr25Ni21 seamless stainless steel pipe belongs to austenitic stainless steel and has good weldability. However, due to its high nickel and chromium content, it is prone to hot cracking during welding, especially in the welding of thick-walled materials. Therefore, in practical operation, measures such as preheating, interpass temperature control, and slow cooling after welding are necessary to reduce crack formation. In addition, selecting suitable welding materials is crucial to ensuring weld quality; it is generally recommended to use welding wire or electrodes with a composition similar to the base metal.

Third, Application Areas of 07Cr25Ni21 Seamless Stainless Steel Pipe.

Due to its unique properties, 07Cr25Ni21 seamless stainless steel pipe is widely used in multiple fields:

1. Chemical Industry: Due to its excellent corrosion resistance, 07Cr25Ni21 seamless stainless steel pipe is particularly suitable for manufacturing pipelines, reaction vessels, heat exchangers, and other components in chemical equipment.

2. Power Industry: In nuclear power plants and thermal power plants, 07Cr25Ni21 seamless stainless steel pipes are used in critical components such as high-temperature and high-pressure steam pipelines, condensers, and feedwater heaters.

3. Oil and Gas Industry: Due to its excellent corrosion resistance and high-temperature strength, 07Cr25Ni21 seamless stainless steel pipes are suitable for pipelines handling corrosive media during oil and gas extraction and transportation.

4. Food Processing Industry: 07Cr25Ni21 seamless stainless steel pipes, meeting food-grade standards, can be used to manufacture conveying pipelines and storage tanks in food production equipment, ensuring food safety.

5. Environmental Protection and Water Treatment: In environmental protection projects such as wastewater treatment and seawater desalination, 07Cr25Ni21 seamless stainless steel pipes are highly favored due to their corrosion resistance.

Fourth, Production Process and Quality Control of 07Cr25Ni21 Seamless Stainless Steel Pipes.

The production of 07Cr25Ni21 seamless stainless steel pipes mainly involves the following steps: raw material preparation, heating and piercing, rolling and stretching, heat treatment, pickling and passivation, inspection and testing, and finished product packaging.

- Raw Material Preparation: High-quality 07Cr25Ni21 stainless steel billets are selected, ensuring uniform chemical composition and freedom from inclusions.

- Heating and Piercing: After heating the billet to a suitable temperature, it is pierced through a piercing mill to form a preliminary tube blank.

- Rolling and Extending: The pierced tube blank is rolled in multiple passes, gradually reducing the diameter and increasing the wall thickness until the required dimensions are achieved.

- Heat Treatment: The rolled 07Cr25Ni21 seamless stainless steel tube undergoes solution treatment and aging treatment to eliminate internal stress and improve microstructure uniformity and performance stability.

- Pickling and Passivation: Pickling removes oxide scale and impurities from the surface of the 07Cr25Ni21 seamless stainless steel tube, followed by passivation treatment to enhance surface corrosion resistance.

- Inspection and Testing: The finished 07Cr25Ni21 seamless stainless steel tube undergoes visual inspection, dimensional measurement, mechanical property testing, and hydrostatic testing to ensure product quality meets standards.

- Finished Product Packaging: Qualified 07Cr25Ni21 seamless stainless steel pipes undergo rust-proofing treatment and are packaged using suitable packaging materials for transportation and storage.

Regarding quality control, in addition to the strict monitoring of the production process mentioned above, rigorous chemical composition analysis of raw materials is required, along with regular sampling inspections of finished 07Cr25Ni21 seamless stainless steel pipes. A comprehensive quality traceability system is also established to ensure the traceability and quality stability of each batch of products.

In summary, 07Cr25Ni21 seamless stainless steel pipes, with their excellent performance, wide range of applications, and strict production quality control, have become an indispensable material in the industrial field. With continuous technological advancements and accelerated industrialization, the demand for 07Cr25Ni21 seamless stainless steel pipes will continue to grow, and its development prospects are promising.