According to the data released by the Japan iron and Steel Union (JISF), the export volume of Japanese steel in the second quarter of 2020 A514 grade P quenched and tempered steel is about 4.959 million tons, a year-on-year decrease of 14.2%; the export volume in the first half of 2020 is about 11.07 million tons, with a year-on-year growth of 1.8%. It has been revealed that the year-on-year increase in export volume does not mean that Japan's export A514 grade P quenched and tempered steel situation of Pugang is better in the first half of the year, but only because the base number of the same period last year is too low.
The final heat treatment of quenched and tempered alloy steel, A514 grade P quenched and tempered steel is quenching and high temperature tempering. The hardenability of quenched and tempered alloy steel is high, and oil is generally used. When the hardenability is very high, it can even be air cooled, which can reduce the defects of heat treatment. The final properties of quenched and tempered alloy steel depend on tempering temperature. Generally, it is tempered at 500 ℃ - 650 ℃. The required properties can be obtained by selecting tempering temperature. In order to prevent the second kind of temper brittleness, fast cooling (water cooling or oil cooling) after tempering is beneficial to the improvement of toughness.
Chemical composition of Q420 steel: C ≤ 0.20, Si ≤ 0.50, Mn ≤ 1.70, P ≤ 0.035, S ≤ 0.035, Nb ≤ 0.07, V ≤ 0.20, Ti ≤ 0.20, Cr ≤ 0.30, Ni ≤ 0.80, Cu ≤ 0.30, N ≤ 0.015, Mo ≤ 0.20. The mechanical properties of Q420 steel are: yield strength ≥ 340 MPa, tensile strength 500-680 MPa, elongation after fracture ≥ 18%, impact energy 34J. A514 grade P quenched and tempered steel, Q420 steel has good mechanical properties and weldability, good cold and hot workability. Q420 steel is mainly used for manufacturing mining machinery, heavy vehicles, ships, bridges, medium and high pressure boilers, vessels and other large welding and structural parts.
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