CN105057364A

CN105057364A - Magnesium alloy sheet rolling edge crack pre-judgment and control method

Info

Publication number: CN105057364A
Application number: CN201510513491.4A
Authority: CN
Inventors: 黄志权; 黄庆学; 马立峰; 韦建春; 楚志兵; 朱艳春
Original assignee: Taiyuan University of Science and Technology
Current assignee: Taiyuan University of Science and Technology
Priority date: 2015-08-20
Filing date: 2015-08-20
Publication date: 2015-11-18
Anticipated expiration: 2035-08-20
Also published as: CN105057364B

Abstract

The invention relates to a magnesium alloy sheet rolling edge crack pre-judgment and control method and belongs to the field of metal material machining. Firstly, according to magnesium alloy of a specific brand, the critical fracture strain of the magnesium alloy under hot rolling conditions, a Zener-Hollomon expression for reflecting material performance and a basic model between the critical fracture strain, and a deformation temperature and a strain rate are determined; and then a hot rolling edge crack pre-judgment model containing material deformation activation energy and a basic rolling process parameter is determined. Accordingly, an edge crack is pre-judged, process optimization is conducted, and edge crack control is achieved. The hot rolling edge crack pre-judgment model contains factors such as the deformation activation energy Q for reflecting the material performance, the roll diameter r of the major parameter of rolling equipment, the rolling speed v of the rolling process parameter, the pre-rolling thickness H of a rolled piece, the post-rolling thickness h of the rolled piece, and the press quantity delta h=H-h. Through the magnesium alloy sheet rolling edge crack pre-judgment and control method, the magnesium alloy rolling edge crack can be pre-judged effectively, guidance is provided for process optimization, and then the purposes of retarding or controlling the edge crack, increasing the finished product ratio, improving the material performance and reducing cost are realized.

Description

A kind of magnesium alloy plate rolled edge splits anticipation and control method

Technical field

The invention belongs to metal material processing field, be specifically related to a kind of magnesium alloy plate rolled edge and split anticipation and control method.

Background technology

Magnesium alloy is at present can the lightest structural metallic materials of industrial applications, and its proportion is only 1/4 of steel; Have lower elastic modelling quantity and larger antidetonation coefficient and superior shock resistance, damping effect is obvious; Pyroconductivity height and not magnetic conductivity, therefore have good heat dispersion and function of shielding; Compared with aluminium alloy, magnesium alloy has higher specific strength and rigidity, and thus application is more more extensive than aluminium alloy; Production process energy consumption is low and easily reclaim, and is described as following green metal structural material.

Magnesium alloy plate is widely used in Aero-Space, track traffic, automobile, 3C industry and daily necessities.But the factor such as poor, rapid heat dissipation of plasticity under its special Patterns for Close-Packed Hexagonal Crystal structure, room temperature condition, make its fracture toughness lower, in roll forming process, very easily occur that limit is split, greatly reduce the lumber recovery of magnesium alloy plate, thus significantly add its production cost, become one of major technology bottleneck hindering the fast development of magnesium alloy plate industry to face.At present, magnesium alloy plate is mainly taked to extrude the rolling mill practice that base adds the little pressure of multi-pass and is produced, the wide limited and inefficiency of the plate produced of this mode.Adopt ingot casting to carry out the technology pattern of hot rolling, split due to limit and be seriously mostly in experiment or trial production stage.Therefore, can to split magnesium alloy plate rolled edge according to equipment and blank performance parameter and make anticipation and realize controlling, to optimization magnesium alloy rolling technique, improve lumber recovery and material property, the industrialization production of promotion magnesium alloy plate and application have great importance.

Summary of the invention

The object of this invention is to provide and a kind ofly can make the method for anticipation according to equipment and blank performance parameter to magnesium alloy hot-rolling edge cracking, and guide process optimization to realize limit and split control, improve lumber recovery and material property, reduce costs.

The present invention includes: for AZ31B magnesium alloy, determine its Critical fracture strain under hot-rolled condition and embody Zener-Hollomon expression formula of this material property, and Critical fracture strain and basic model between deformation temperature and strain rate, determine the hot-rolling edge cracking anticipation model containing this material modification activation energy and basic rolling technological parameter.Opposite side splits and makes anticipation accordingly, and guides process optimization, realizes limit and splits control, and concrete invention process is as follows.

First, for AZ31B casting of magnesium alloy strip plate, determine its Critical fracture strain under hot-rolled condition and embody Zener-Hollomon expression formula of this material property.By Gleeble thermal simulation machine, adopt equal-pressure method, acquisition deformation temperature and strain rate are respectively at 473-673K and 0.005-5s ^-1critical fracture strain under condition, is designated as in table 1; Zener-Hollomon expression formula of this material can be obtained simultaneously in deformation activation energy , in this formula for gas constant , for strain rate, for deformation temperature, thus the hot worked Critical fracture strain of AZ31B magnesium alloy can be set up with between relation such as formula (1), reflect with this impact that deformation temperature and strain rate strain Critical fracture.

critical slope langth value under table 1AZ31B magnesium alloy different condition

Tab1CriticaldamagevalueofAZ31Bmagnesiumalloybydifferentconditions

。

(1)。

Secondly, the hot-rolling edge cracking anticipation model containing this material modification activation energy and basic rolling technological parameter is determined.The Basic Mechanism of generation is split: in the operation of rolling according to magnesium alloy rolling limit, when maximum tension stress-strain suffered by edge reaches the critical slope langth value of material, namely produce fracture, conform to the service condition of Cockcroft & Latham fracture criterion.Cockcroft & Latham criterion is such as formula (2).

(2)。

In formula for the critical slope langth value of material, be also referred to as damage threshold, affect by the factor such as temperature, rate of deformation; Because Deform-3D finite element software acquiescence Cockcroft & Latham criterion is as impairment parameter calculation criterion, therefore utilizes this finite element software to carry out analog rolling process, thus obtain the critical slope langth value under each respective conditions .The critical slope langth value obtained will be simulated with compare, if , then must there occurs limit and split, on the contrary time, crackle should do not had to produce, come in anticipation magnesium alloy rolling process, whether to produce limit with this and split.Thus, simultaneous formula (1) and (2), namely contained cockcroft & Latham anticipation model is split on the AZ31B magnesium alloy rolling limit of the factor.

(3)。

Meanwhile, namely have based on rolling therory.

(4)。

Simultaneous (3) formula and (4) formula can determine that AZ31B magnesium alloy hot-rolling edge cracking anticipation model containing sex change activation energy and basic rolling technological parameter is as (5) formula.

(5)。

In formula (5), for the critical slope langth value of material, be also referred to as damage threshold; for equivalent plastic strain during Materials Fracture; for equivalent stress; for equivalent strain incresment; for maximum tension stress during Materials Fracture, for mill speed, for rolling front rolled piece thickness, for rolling rear rolled piece thickness, for drafts, for roller radius.

Finally, process optimization, realizes limit and splits control.Through type (5) just sets up basic rolling technological parameter: the qualitative anticipation between rolling temperature, drafts, mill speed, roller footpath etc. and rolled edge split, and thus can realize improving by optimizing rolling technological parameter the object split on magnesium alloy rolling limit.

The present invention has the following advantages and good effect.

(1). whether the present invention can be split and occur in Accurate Prediction limit, and can instruct process parameter optimizing accordingly, effectively controls limit and splits, improve lumber recovery and plate property, thus significantly reduces production cost, improves productivity effect.

(2). process of the present invention is carried out for AZ31B magnesium alloy, but the method is applied widely, can be applicable to the anticipation that the difficult deformable metal gold copper-base alloy rolled edges such as the magnesium alloy of other trades mark, titanium alloy, molybdenum alloy split.

(3). the present invention is simple and easy to do, safe and reliable, is specially adapted to industrialized producing technology optimization.

Detailed description of the invention

embodiment 1:blank is AZ31B cast-rolled strip, and thickness is 6.8mm, and width is 500mm, and roller diameter is 380mm, and deformation temperature 300 DEG C, drafts 30%, mill speed are 0.5m/s.The maximum impairment value of rolled piece in the operation of rolling under this condition is obtained by finite element modelling =0.287, and calculated by (1) formula , then learnt by anticipation model (5) formula: , crackle should do not had to produce, and namely this rolling condition is suitable for the rolling of magnesium alloy AZ31B cast-rolled strip.

embodiment 2:blank is AZ31B cast-rolled strip, and thickness is 6.8mm, and width is 500mm, and roller diameter is 380mm, and deformation temperature 400 DEG C, drafts 60%, mill speed are 0.5m/s.The maximum impairment value of rolled piece in the operation of rolling under this condition is obtained by finite element modelling =0.597, and calculated by (1) formula , then learnt by anticipation model (5) formula: , crackle must be had to produce, need be optimized technological parameter, can deformation temperature be improved according to formula (5) within the scope of hot-rolled condition, reduce drafts etc. and make .

Claims

1. a magnesium alloy plate rolled edge splits anticipation and control method, comprise: for AZ31B magnesium alloy, determine its Critical fracture strain under hot-rolled condition and embody Zener-Hollomon expression formula of this material property, and Critical fracture strain and the basic model between deformation temperature and strain rate; Determine the AZ31B magnesium alloy hot-rolling edge cracking anticipation model containing this material modification activation energy and basic rolling technological parameter:

In formula: for the critical slope langth value of material, be also referred to as damage threshold, for the Critical fracture of material strains, for equivalent plastic strain during Materials Fracture, for equivalent stress, for equivalent strain incresment, for maximum tension stress during Materials Fracture, for mill speed, for rolling front rolled piece thickness, for rolling rear rolled piece thickness, be drafts, for roller radius, if , then must there occurs limit and split, on the contrary time, crackle should do not had to produce, and opposite side splits and makes anticipation accordingly, and guides process optimization, realizes limit and splits control.