Q690D is a high-strength building material steel plate, which is a quenched and tempered steel plate for high-strength structures. Q690D steel plate has high yield strength and tensile strength, and is usually used to manufacture structural and mechanical components with high requirements for strength and stability.
The letter "q" means the yield strength of the steel plate, which is the first letter of the Chinese pinyin of "yield".
690: is the yield value of the steel plate, unit: MPa.
The letter "D": is the grade or quality grade of the steel plate, and the impact of the D grade steel plate is -20°C.
Smelting: The smelting of molten steel is carried out by electric furnace or oxygen converter to remove impurities and ensure the accuracy of composition.
Continuous casting: Molten steel is injected into a continuous caster to solidify into a blank of a certain specification.
Rolling: The continuous casting billet is heated, and then rolled in multiple passes to obtain the steel plate of the required specification.
Quenching and tempering treatment: The rolled steel plate is quenched and tempered to obtain the required comprehensive mechanical properties. This step is a key step in the production of Q690D steel plates, which allows the steel plates to obtain excellent strength and toughness by controlling the temperature and time of quenching and tempering.
In addition, in order to obtain steel plates with finer grains, higher strength and better toughness, rapid, sub-rapid and relatively fast solidification technologies are also used to prepare continuous casting thin strips, continuous casting thin slabs, hot-rolled medium and heavy plates with uniform structure, no segregation or minimal segregation, inclusion or precipitation of fine or maintaining solid solution. Using the method of solid-phase composite-additive manufacturing, the rolling billet is manufactured, and then after hot rolling, the uniform, less segregation, fine and uniform structure of the steel can be obtained, and the performance of the material can be improved.
Delivery status of Q690D board: modulated.
Q690D high-strength plate flaw detection requirements: national standard one exploration, national standard two exploration, national standard three exploration.
The thickness of Q690D high-strength plate can be done for Z performance: Z15, Z25, Z35. The grades are Q690DZ15, Q690DZ25, Q690DZ35
The executive standard of Q690D steel plate is GB T1591-2008. gb/t16270-2009
According to the GB T709 standard, the allowable deviation of the thickness of Q690D steel plate is divided into three categories: A, B and C. Class A deviations are positive, Class B deviations are negative, and Class C deviations are positive and negative deviations. The specific allowable deviation values are as follows:
Class A deviation: The difference between the maximum and minimum allowable values of the thickness specified in the standard, that is, the sum of the upper and lower deviations, varies according to the product specifications.
Category B deviation: Usually refers to the permissible deviation of the thickness of the lighter class, the lower deviation is zero, and the upper deviation varies according to the product specification.
Class C deviation: including positive deviation and negative deviation, which is the upper deviation and lower deviation value specified in the standard, which varies according to the different product specifications.
Yield Strength (MPa): 640MPa
Tensile strength (MPa): 730MPa
Elongation a%: 14
Impact power AKV(J)-20:47