The outer diameter of the hot-rolled seamless pipe is generally larger than 32mm, and the wall thickness is 2.5-75mm. The diameter of the cold-rolled seamless pipe can be 6mm, the wall thickness can be 0.25mm, the outer diameter of the thin-walled pipe can be 5mm, and the wall thickness is less than 0.25mm. The size accuracy of the cold-rolled seamless pipe is higher than that of the hot-rolled seamless pipe, SA572 high-strength structural steel grade 60.
The effect of nitrogen (N) on the properties of SA572 high-strength structural steel grade 60 and so on steel is similar to that of carbon and phosphorus. With the increase of nitrogen content, the strength of steel can be significantly improved, especially the plasticity, especially toughness, and the weldability will be decreased, and the cold brittleness will be intensified. At the same time, aging tendency, cold brittleness and hot brittleness will be increased, which will damage the weldability and cold bending property of steel. Therefore, the nitrogen content in SA572 high-strength structural steel grade 60 and so on steel should be reduced and limited as much as possible. Generally, nitrogen content should not be higher than 0.018%.
At the same time, the company operates a variety of products of related iron and SA572 high-strength structural steel grade 60 steel enterprises. Annual sales of steel 3.6 million tons, standing stock of 400000 tons, has developed more than 10000 users. The company has a first-class marketing service system, strong storage and transportation capacity and supporting supply, cutting distribution capacity, and gradually build it into an important marketing channel. The company has obtained SA572 high-strength structural steel grade 60 ISO9001:2000 quality system certification, A-level credit unit of the people's Bank of China, and is an excellent supplier of many large state-owned enterprises.
S355J2 is a low-alloy high-strength steel, which can be treated to meet the requirements of Z-15, Z-25, Z-35 and level I, level II and level III flaw detection.The extension grades of S355J2 are S355J2, S355J2-Z35 and S355J2 + N-Z35, SA572 high-strength structural steel grade 60. On the basis of S355J2, S355J2-Z35 increases the requirement of S355J2 steel plate thickness direction performance, namely Z-direction performance. S355J2 + N-Z35 is a heat treatment process which increases Z-direction properties and normalizing rolling (or normalizing).