SA573 Grade 70 structural carbon steel angle bar for coil steel

Q370qDNH steel plate atmospheric corrosion resistance steel grade: Q—The first letter of the Chinese pinyin of "qu" for the yield strength of steel used in bridges; 370-a specified value of small yield strength, unit MPa; q-the first letter of the Chinese pinyin of the word "bridge" for bridge steel; D—The quality level is D level; N——The first letter of the Chinese phonetic alphabet of the word "Nei"; H——The first letter of Pinyin of "hou"; Q370qDNH steel standard: GB/T 714-2015.

Composition characteristics of low alloy structural steel, SA573 Grade 70 structural carbon steel angle bar: (1) Low carbon: the carbon content of low alloy structural steel is less than 0.20% due to the high requirements of toughness, weldability and cold formability. (2) The alloy elements such as manganese are added. (3) The addition of Nb, Ti or V and other auxiliary elements: a small amount of Nb, Ti or V forms fine carbides or carbonitrides in the steel, which is beneficial to obtain fine ferrite grains and improve the strength and toughness of low alloy structural steel. In addition, adding a small amount of copper (≤ 0.4%) and phosphorus (about 0.1%) can improve the corrosion resistance. The addition of a small amount of rare earth elements can remove sulfur and gas, purify the steel, and improve the toughness and process performance of low alloy structural steel.

S355J2 steel plate rolling process is controlled rolling process. In the rolling process, the ingot rolling temperature is 1000-1050℃; in the first stage, the low-speed and large reduction rolling process is adopted, the high-temperature stage is 950-1000℃, the SA573 Grade 70 structural carbon steel angle bar rolling speed is 1.6-2.0m/s, the single reduction rate is 15-20%, and the cumulative reduction rate is 40-45%, so as to ensure sufficient deformation of ingot. In the first stage, the start rolling temperature is 910-930℃, and the finish rolling temperature is ≤ 870℃.As a basic building material, steel plates are currently widely used in automobiles, shipbuilding, chemical industry, aerospace and other fields. Reasonable selection of flaw detection methods to ensure the quality of SA573 Grade 70 structural carbon steel angle bar steel plates is of great significance to safe production. Common defects of steel plates are folding, inclusion, shrinkage, air bubbles, delamination and cracks. These problems can be discovered in time through flaw detection.

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