CN-116727506-B - Roll bending forming fracture prevention control method for ultra-high strength steel thin-wall component with complex section

CN116727506BCN 116727506 BCN116727506 BCN 116727506BCN-116727506-B

Abstract

The invention provides a roll bending forming fracture prevention control method of a complex-section ultra-high-strength steel thin-wall member, and relates to the technical field of roll bending forming. The roll bending forming fracture prevention control method specifically comprises the steps of taking Oyane toughness fracture criteria as a judgment standard of fracture generation in a roll bending forming complete process, fusing roll bending forming strategies and roll bending forming technological parameters to comprehensively consider fracture prevention control, solving through a fracture prevention mathematical model according to the differences of different unit parameter ranges when configuring unit technological parameters, adopting a technological parameter adjustment method in an adjustable interval, and setting a technological parameter value range and an optimal trend value according to on-site actual production conditions so as to solve an optimal technological parameter combination. The invention can effectively prevent the defect of fracture of the roll forming bent angle of the ultra-high strength steel thin-wall component with the complex section, saves the production cost, improves the quality and the yield of the ultra-high strength steel thin-wall component with the complex section, and is beneficial to industrial mass production and popularization.

Inventors

CAO JIANGUO
WANG XUESONG
ZHAO RONGGUO
WEI ZHIDONG
ZHU HAO
CHENG JIAOJIAO
LIU JIANG
LI YANLIN
ZHU XUDONG

Assignees

北京科技大学
江苏帝尔保机械有限公司

Dates

Publication Date: 20260512
Application Date: 20230619

Claims (5)

1. A roll bending forming fracture prevention control method for a complex-section ultra-high-strength steel thin-wall component is characterized in that the ultra-high-strength steel material adopts martensitic steel with tensile strength exceeding 980MPa, and comprises the steps of taking Oyane toughness fracture criteria as judgment criteria for fracture generation in a roll bending forming complete process, fusing roll bending forming strategies and roll bending forming process parameters to comprehensively consider fracture prevention control, solving through a fracture prevention mathematical model according to the differences of different unit process parameter ranges when the process parameters are configured, adopting a process parameter adjustment method in an adjustable range, setting a process parameter value range and an optimal trend value according to on-site actual production conditions, and solving an optimal process parameter combination; the comprehensive consideration of fracture prevention control is a forming strategy design method which is formed by adopting a fixed arc length and bent angle forming mode, an average five boundary condition forming angle distribution mode and increasing the number of times of effectively realizing fracture prevention forming channels in the roll bending forming complete process when the roll-finishing process is designed; The roll bending forming strategy is to select a fixed arc length corner forming mode from corner forming modes; the angle distribution mode of forming under the five boundary conditions is selected from the angle distribution modes, and the formula is as follows: ; wherein: in order to form the pass of the mold, Is the first The angle of the pass bend, In order to achieve a final bending angle, the bending angle, Is the complementary angle; the number of effective forming channels is properly increased during the distribution of the number of the channels; the fixed arc length bent angle forming mode, the average five boundary condition forming angle distribution mode and the integral roll bending forming process can be used for effectively reducing the equivalent plastic strain and stress triaxial peak value at the dangerous node of the broken bent angle, so that the damage value of the final pass is smaller than the breaking threshold value; The technological parameter adjusting method specifically adopts a response curved surface method to explore the influence rule of roll bending forming technological parameters on fracture, increases the distance between frames, increases the distance between roll shafts, reduces the forming speed, reduces the friction coefficient to reduce fracture damage values, sets the distance between frames, the friction coefficient, the forming speed and the distance between the roll shafts as influence factors, sets the damage values as response, and fits a quadratic nonlinear regression mathematical model of the damage values about the four influence factors, wherein the formula is as follows: ; wherein: in response to this, the control unit, 、 And As the coefficient of regression of the coefficient of the data, And Is the first And (b) The number of influencing factors is one, The number of parameters is represented and the number of parameters is represented, Is an error term; According to the on-site actual production condition, a mathematical model is adopted to consider the weight ratio of the influence factors, namely, the frame spacing, the roll shaft spacing, the forming speed and the friction coefficient, and the trend values of the four influence factors, namely, the frame spacing trend to be smaller, the friction coefficient trend to be larger, the forming speed trend to be larger and the roll shaft spacing trend to be smaller.
2. The roll bending forming fracture prevention control method for the ultra-high strength steel thin-wall component with the complex cross section according to claim 1, further comprising the steps of selecting a Swift-Voce mixed hardening model to represent the large-range true stress and true strain relation of the ultra-high strength steel, wherein the formula is as follows: ; wherein: In order to be a plastic strain, In order to be a yield strain, For the work hardening index of the material, , 、 And As a matter of material parameter(s), In order to adjust the weight coefficient of the light-emitting diode, Is true stress.
3. The method for preventing and controlling roll bending forming fracture of a thin-walled member of ultra-high strength steel with a complex cross section according to claim 1, wherein the Oyane ductile fracture criterion is as follows: ; wherein: For an equivalent plastic strain at break, For equivalent plastic strain, a is a material parameter, In order to be a fracture threshold value, In the presence of a hydrostatic pressure, the fluid, Is Von Mises equivalent stress.
4. The roll bending forming fracture prevention control method for the ultra-high-strength steel thin-wall component with the complex section according to claim 1, wherein the Oyane toughness fracture criterion is used for obtaining a fracture threshold value of the ultra-high-strength steel material through a basic experiment and numerical simulation combination mode, the stress triaxial relation at the dangerous bent angle is integrated with the plastic strain to obtain a fracture damage value, and the threshold value is compared with the damage value to judge whether the fracture occurs during roll bending forming.
5. The method for preventing and controlling the breakage of the roll bending forming of the ultra-high-strength steel thin-wall component with the complex cross section according to claim 1, wherein the breakage damage value obtained by the optimal process parameter combination is reduced by more than 37.98% compared with the original breakage damage value, and the damage value of the non-breakage damage angle is further improved to be reduced by more than 19.63%.

Description

Roll bending forming fracture prevention control method for ultra-high strength steel thin-wall component with complex section Technical Field The invention relates to the technical field of roll bending forming, in particular to a roll bending forming fracture prevention control method for a thin-wall component of ultra-high-strength steel with a complex section. Background In the world, the development of the automobile industry is not yet advanced, the automobile industry is one of important pillar industries for national economy development, the world energy and environmental crisis are still severely restrained, and the automobile weight reduction is a necessary path for sustainable development of the automobile industry. The ultrahigh-strength steel has the advantages of low cost and high performance, so that the application range of the ultrahigh-strength steel in the production and manufacture of automobile lightweight products is wider and wider. The roll bending forming process for the ultra-high strength steel has the advantages of high production efficiency, low manufacturing cost, uniform product section shape, high dimensional accuracy, multiple varieties, complex section and the like, ensures the product strength as much as possible, and becomes one of the important forming processes for processing the metal products of the thin-wall components with the complex section at present. However, in the process of improving the light weight level of the roll bending section by adopting the ultra-high strength steel material, a series of technical problems occur in processing and manufacturing due to the characteristics of high yield ratio, low elongation, poor plasticity, more complex mechanical properties and the like of the ultra-high strength steel material at room temperature and the technical requirements of more and more complicated product section design, wherein roll bending forming fracture failure of the ultra-high strength steel complex section thin-wall member is one of the most outstanding problems. The occurrence of fracture phenomenon in the roll bending forming process can reduce the yield of products, so that the production cost is increased, the enterprise benefit is not guaranteed, and the application of the ultra-high strength steel roll bending forming in the field of automobile light weight is seriously affected. In the roll bending forming process, the phenomenon of corner crack occurs when a rectangular tube is produced by 'round square transformation' of common carbon steel materials, and the more traditional mode is to adopt the 'square transformation' to change the technological process, namely, a longitudinal shearing belt is used, the whole-process roll bending forming of which the forming is performed firstly and then the welding is performed and then the sizing is performed according to the cross section shape of the product, so that the stress concentration at a corner can be obviously reduced, the metal flow at the corner part is promoted, and the phenomenon of corner crack is avoided. On the basis, for solving the corner fracture phenomenon in the simple special-shaped tube, a composite process combining square and round square is adopted to replace a single round square or square process, namely, in the sizing stage, the straight line section of the upper bottom, the two side edges and the two small corners of the upper bottom are sized to the final size by adopting the square process, and the large arc corner is rolled to the final size by adopting the round square process, so that the corner fracture problem of the trapezoid-section special-shaped tube can be well solved. However, the solution is directed to a plain carbon steel rectangular pipe or special-shaped pipe with a simple cross section, and the solution to the fracture problem of a non-tubular high-strength steel product with a complex cross section is difficult to be applied. In addition, the problem of cracking of a small bending radius fillet or sharp corner can be solved by adopting a roll bending forming local heating forming method, a heating device is adopted to carry out local high-frequency heating on the fillet part of the strip steel, so that blanks at the fillet part are converted into austenite structures, the heating temperature is dependent on the austenite transformation temperature of various steels, thus the deformation part and the dangerous part can be heated and softened, the plasticity and the fluidity of the deformation part and the dangerous part can be improved, the yield strength and the internal stress of the strip steel are reduced, the possibility of cracking of the forming work and the fillet is effectively reduced, but the method has the advantages of complex operation, higher production and maintenance cost, and difficult control on the relation between the heating temperature and the materials, so that the application range is greatly limited, the method is not well popu