High plastic-strain ratio galvanized steel sheet and production method

Abstract

The invention relates to a hot galvanizing sedan plate and the production method thereof, which solves the following problems: P and S in steel are difficult to control because of being lowly required; as to a horizontal Sendzimir hot galvanizing machine, the recrystallization temperature of a steel plate is slightly high, and the plastic strain ratio and extension are low. The high-plastic-strain-ratio galvanizing plate is composed of no more than 0.004% by weight of C, no more than 0.020% by weight of Si, 0.05% to 0.20% by weight of Mn, no more than 0.016% by weight of 0.016, no more than 0.015% by weight of S, 0.04% to 0.07% by weight of Ti, 0.02% to 0.06% by weight of Als, no more than 0.003% by weight of N, and the balance Fe and unavoidable impurity. The production steps are as follows: smelting by hot metal desulphurization and secondary refining process; hot rolling; cold rolling with a total reduction of 80%; and galvanizing. The invention has the characteristics that the method is pure Ti processing; the control scopes of S and P are wide; the plastic strain ratio is r90 DEG C >=2.5, the extension A80mm is 45% to 50%; and the current process route and equipment is unchanged.

Description

technical field [0001] The invention relates to an automobile sheet and a production method, in particular to a hot-dip galvanized automobile sheet and a production method thereof. Background technique [0002] Due to the fact that the annealing line of a large number of existing horizontal Sendzimir hot-dip galvanizing units in China is too short (the length of the annealing line of the heating section and the soaking section is not as long as that of the modern vertical US steel hot-dip galvanizing unit heating section and the annealing line of the soaking section 1 / 7 of the length), the low production capacity of ultra-deep drawn car sheets, and the production of deep-drawn galvanized car sheets according to the conventional IF steel composition design, rolling and annealing process, due to the morphology and size of secondary precipitates , the distribution is not ideal, the recrystallization temperature of the steel plate is high, and in the continuous annealing furnace...

AI Technical Summary

Problems solved by technology

[0002] Due to the fact that the annealing line of a large number of existing horizontal Sendzimir hot-dip galvanizing units in China is too short (the length of the annealing line of the heating section and the soaking section is not as long as that of the modern vertical US steel hot-dip galvanizing unit heating section and the annealing line of the soaking section 1 / 7 of the length), the low production capacity of ultra-deep drawn car sheets, and the production of deep-drawn galvanized car sheets according to the conventional IF steel composition design, rolling and annealing process, due to the morphology and size of secondary precipitates , the distribution is not ideal, the recrystallization temperature of the steel plate is high, and in the continuous annealing furnace of this type of galvanizing unit, the holding time of high temperature annealing in the soaking section is very short, and the plastic strain ratio (r) value of the produced physical steel plate is low ( general r 90° All ≤ 2.5), the elongation value is also low (generally A 80mm value below 45%), it is not possible to punch ultra-deep drawing parts such as car tailgate, door inner panel, side door, oil pan and so on with large deformation

[0003] At present, there is a means to improve the deep drawing performance of hot-dip galvanized car sheet in the world, which is to use ferrite phase zone rolling during hot rolling production, and to use vertical hot-dip galvanizing unit for production. r value of the finished steel plate, but its disadvantages are: ①The rolling torque of the hot continuous rolling mill increases sharply, and the load level of the rolling mill is required to be greatly increased; ③The rolling process requires a large amount of lubricating oil, which is very polluting and costly, and it is difficult to popularize large-scale production; ④Generally, only medium and low temperature coiling can be used. For continuous annealing, the elongation value of the final finished steel plate Generally lower, although the plastic strain ratio of the steel plate is higher than the r value, the ability to resist plate thickness reduction when punching car parts is strong, but the deep drawing performance is poor

[0004] On the other hand, the current internationally accepted ultra-deep drawing grade hot-dip galvanized car steel sheet has very strict composition requirements. Taking a foreign steel company as an example, the target values ​​of S and P content are required to be controlled as S≤0.008%, P≤0.010 %, it is difficult to control the chemical composition during smelting