Automobile beam steel with tensile strength of 550MPa and preparation method for automobile beam steel

Abstract

The invention provides automobile beam steel with tensile strength of 550MPa and a preparation method for the automobile beam steel. The automobile beam steel comprises the following chemical components in percentage by mass: 0.04-0.12% of C, 0.05-0.35% of Si, 0.5-1.2% of Mn, less than and equal to 0.015% of S, less than and equal to 0.02% of P, 0.02-0.05% of Als, 0.02-0.06% of Ti, and the balance of Fe and inevitable impurities. The tissue of the automobile beam steel is quasi-polygonal ferrite and pearlite, wherein the volume fraction of the quasi-polygonal ferrite is 82-96%, the volume fraction of the pearlite is 4-18%, and the mean grain size is 5-9 microns. The invention further provides a preparation method for the automobile beam steel. A steel billet adopting the chemical component proportion is subjected to a reasonable process design, cheap micro alloy titanium is used to replace noble micro alloy niobium and vanadium, the production cost is reduced while load of a rolling mill and a rolling machine is reduced, the production efficiency is improved, and the automobile beam steel with tensile strength of 560 MPa to 590 MPa is obtained.

Description

technical field [0001] The invention belongs to the technical field of metallurgy, in particular to an automobile frame steel with a tensile strength of 550MPa and a preparation method thereof. Background technique [0002] With the development of the automobile industry and the automobile industry, the demand for automobile steel is increasing year by year. At the same time, the need for lightweight vehicles has also accelerated the demand for high-strength automotive steel. As a kind of high-strength automobile steel, the automobile frame steel with a tensile strength of 550MPa is more and more widely used and has gradually replaced the automobile frame steel with a tensile strength of 320MPa, 420MPa and 510MPa. The longitudinal beams and beams of the automobile are connected together by riveting, bolting or welding to form the automobile frame, which is supported on the wheels through the suspension device and the front and rear axles. In order to ensure the safety of ...

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Problems solved by technology

[0003] Patent CN200810201495.9 discloses a hot-rolled automobile steel plate with a tensile strength of 550MPa, which adds 0.021-0.091% niobium (Nb) or 1.78% manganese (Mn) in the composition design, the cost is relatively high, and the final rolling The temperature is 832-895°C, and the coiling temperature is 563-658°C, both of which are relatively low, resulting in an increase in the load on the rolling mill and coiler; patent CN201010512841.2 discloses a micro-niobium 510MPa grade automobile frame steel plate and its manufacturing method. A certain amount of niobium (Nb) is added in the composition design, and the cost is high. At the same time, the final rolling temperature is 820~870°C, and the coiling temperature is lower than 590°C, resulting in a large load on the rolling mill and coiler; patent CN201010242976.1 published Niobium-titanium composite heavy-duty truck and automobile beam steel and its preparation method, its composition design adds 0.03~0.06% niobium (Nb), the cost is high, the finish rolling temperature and coiling temperature are low, resulting in the load of the rolling mill and the coiling machine The load is relatively large; patent CN201310641525.9 discloses a hot-rolled high-strength thin steel plate with a tensile strength of 510MPa and its production method. Increase; patent CN201210198193.7 discloses a 590L automobile frame steel and its CSP preparation method, in which 0.025~0.06% niobium (Nb) and 0.07~0.12% vanadium (V) are added in the composition design, and the microalloy cost Higher; Patent CN200580027658.0 discloses high-strength steel with excellent weldability and toughness with a tensile strength of 550 MPa or more and its manufacturing method. The composition design includes 0.01-0.08% niobium (Nb) % vanadium (V), the cost of microalloying is higher

[0004] With the wide application of automobile frame steel with a tensile strength of 550MPa, some problems have gradually emerged. For example, the automobile frame steel with a tensile strength of 550MPa generally uses niobium-vanadium-titanium (Nb-V-Ti), - Composition design of vanadium (Nb-V) or niobium-titanium (Nb-Ti) microalloying, the cost of microalloying per ton of steel increases by as much as 70~110 yuan

In the fierce market competition, the cost of this microalloy has almost no profit for steel companies; at the same time, automobile frame steel with a tensile strength of 550MPa generally adopts a lower final rolling temperature (820~860°C) combined with a lower coil The temperature (530~620℃) is used for production, which increases the load of the rolling mill and coiler and reduces the production efficiency. At the same time, the relatively high yield ratio (0.86~0.9) is easy to cause cracking at the bend during the stamping process. Affect the product yield

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