In 2019, the output of pig iron in the world was 1.265 billion tons, with China accounting for 64%; the overseas output accounted for 36% (460 million tons), ranking 86.982 million tons of EU 28 countries, 74.907 million tons of Japan, 74.099 million tons of India, 73.264 million tons of CIS, and Q345B, S355J0, S355N structural alloy steel 47.521 million tons of South Korea. In the first quarter, the global output was 311 million tons, with a year-on-year decrease of 0.5%, with China Q345B, S355J0, S355N structural alloy steel increasing by 2.4%; the overseas output decreased by 5.4%, Among them, EU decreased by 9.2%, Japan increased by 1.3%, India decreased by 7.7%, CIS increased by 2.1%, and South Korea decreased by 4%.
During cladding welding of hardfacing wear-resistant steel plate, Q345B, S355J0, S355N structural alloy steel, preheating and slow cooling should not be adopted. Sometimes, forced cooling measures are even taken to reduce the residence time of weld in the temperature range of 400-850℃ to prevent local chromium deficiency in austenite grain boundary and σ brittle phase in the plate, resulting in 475℃ brittleness, so as to ensure that the weld metal has good mechanical properties and intergranular corrosion resistance.
Chemical composition differences between the Q345B, S355J0, S355N structural alloy steel, Q345 steel grades (Q345A / Q345B / Q345C / Q345D / Q345E):Q345A steel：C≤0.20，Mn ≤1.70，Si≤0.50，P≤0.035，S≤0.035； Q345B steel：C≤0.20，Mn ≤1.70，Si≤0.50，P≤0.035，S≤0.035； Q345C steel：C≤0.20，Mn ≤1.70，Si≤0.50，P≤0.030，S≤0.030，Al≥0.015； Q345D steel：C≤0.18，Mn ≤1.70，Si≤0.50，P≤0.030，S≤0.025，Al≥0.015； Q345E steel：C≤0.18，Mn ≤1.70，Si≤0.50，P≤0.025，S≤0.020，Al≥0.015； All the Q345 steel grades contain Nb≤0.07，V≤0.15，Ti≤0.20，Cr≤0.30，Ni≤0.012，Mo≤0.10。
Integrity, cooperation and innovation, positive and competitive, healthy and abundant are the company's core values. The company Q345B, S355J0, S355N structural alloy steel always adhere to the "people-oriented", pay attention to improve the production skills and cultural quality of employees, by cultivating employees to carry forward excellent cultural traditions, set up the correct values, ethics and codes of conduct to improve employees' loyalty and work enthusiasm.