CN118036272A - Diphase stainless steel processing technology based on stress mixing rule - Google Patents

Diphase stainless steel processing technology based on stress mixing rule Download PDF

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CN118036272A
CN118036272A CN202410100617.4A CN202410100617A CN118036272A CN 118036272 A CN118036272 A CN 118036272A CN 202410100617 A CN202410100617 A CN 202410100617A CN 118036272 A CN118036272 A CN 118036272A
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cutting
microhardness
stress
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杨琳
宫福康
张和晴
刘佳良
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Harbin University of Science and Technology
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Harbin University of Science and Technology
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    • G06F30/20—Design optimisation, verification or simulation
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/08—Thermal analysis or thermal optimisation
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
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    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces

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Abstract

The invention discloses a processing technology of duplex stainless steel based on a stress mixing rule, which comprises the following steps: s1: establishing a two-phase stress solving model of the two-phase material, and distinguishing and solving the two-phase stress of the two-phase material; s2: establishing a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount, and revealing the influence rule of the front angle of the cutter and the cutting amount on the two-phase microhardness; s3: and (3) revealing the influence rule of the cutter rake angle and the cutting amount on the distribution characteristics of the two-phase microhardness in the cutting chip, obtaining the matching relation of the cutter rake angle and the cutting amount under the condition that the two-phase microhardness distribution is consistent, and optimizing the processing technology of the duplex stainless steel. According to the invention, through the related knowledge of material mechanics, the influence rule of the two-phase stress distribution of the two-phase material on the two-phase microhardness is revealed. And a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount is established by combining the microhardness and plastic strain relation, so that the problem of uncertain distribution of the two-phase microhardness is solved.

Description

Diphase stainless steel processing technology based on stress mixing rule
The application relates to a split application of 'a duplex stainless steel processing technology based on consistency of two-phase hardness distribution' for application number 202310278952.9, application day 2023, 03 and 21.
Technical Field
The invention belongs to the technical field of cutting duplex stainless steel two-phase microhardness distribution, and particularly relates to a duplex stainless steel processing technology based on a stress mixing rule.
Background
In the cutting S32760 process, two phases of the shearing area are subjected to severe plastic deformation, and the difference and evolution form of the mechanical properties of the materials of the two phases are different, so that the stress distribution of the two phases is uneven. Aiming at the problem that the existing model can not solve the stress of the two-phase material in the cutting process, the model for solving the two-phase stress of the two-phase material is established by considering the inconsistency of the two-phase stress distribution of the two-phase material in the cutting process.
At present, the cutting tool rake angle and the cutting amount have obvious influence on the microhardness of two phases of a processed surface, but a microstructure microhardness resolving model of the cutting processing duplex stainless steel is lacked, and a critical conclusion is lacked on the mapping relation between a microstructure and a cutting process. Therefore, the invention establishes a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount, and reveals the influence of the front angle of the cutter and the cutting amount on the two-phase microhardness, thereby being used as the basis of optimizing the processing technology of the two-phase stainless steel.
The conventional method for improving the machining process only focuses on the modification of the front angle of the cutter or the cutting amount, and does not consider the influence of the matching between the front angle of the cutter and the cutting amount on the two-phase microhardness distribution. Therefore, the invention reveals the rule of influence of the cutter rake angle and the cutting amount on the distribution characteristics of the two-phase microhardness in the cutting chip based on the established two-phase microhardness resolving model, obtains the matching relation of the cutter rake angle and the cutting amount under the condition that the two-phase microhardness distribution is consistent, and optimizes the processing technology of the two-phase stainless steel.
Disclosure of Invention
The invention aims to provide a processing technology of duplex stainless steel based on a stress mixing rule, which aims to solve the problems in the prior art.
In order to achieve the above purpose, the present invention provides the following technical solutions: a processing technology of duplex stainless steel based on stress mixing rule comprises the following steps:
s1: based on a stress mixing rule, a two-phase stress solving model of the two-phase material is established, and the two-phase stress of the two-phase material is distinguished and solved;
S2: establishing a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount, and revealing the influence rule of the front angle of the cutter and the cutting amount on the two-phase microhardness;
S3: based on the established two-phase microhardness resolving model, the influence rule of the cutter rake angle and the cutting amount on the two-phase microhardness distribution characteristics in the cutting chip is revealed, the matching relation of the cutter rake angle and the cutting amount is obtained under the condition that the two-phase microhardness distribution is consistent, and the processing technology of the two-phase stainless steel is optimized.
1. The method for extracting the multi-physical field distribution in the shearing area comprises the following steps:
(1) The schematic diagram of the right-angle cutting shear region is shown in fig. 2, the cutting force is predicted by analyzing the moment balance relation of the shear region and combining with an S32760 biphase constitutive model, and the cutting force is solved by the cutting amount. FEBA and ABCD are the upper and lower halves, respectively, of the bisecting shear zone, AG being the tool-chip contact length, denoted h tc.
(2) Shear plane analysis
Depending on the balance conditions of the shear plane and the tool-chip interface, the individual cutting component and chip thickness t 2 can be found by the following formula:
Ft＝FRsin(λ-α) (1)
Ff＝FRsinλ (2)
Fn＝FRcos(λ) (3)
FN＝FR sinθ (5)
Wherein: alpha is the front angle of the cutter; phi is the included angle between the shearing surface AB and the cutting speed direction, namely the shearing angle; lambda is the friction angle; t1 is the undeformed chip thickness; w is the cutting width; fc and Ft are components of the cutting force in the cutting direction and perpendicular to the cutting direction; ff is the friction of the tool-chip interface; fs is the cutting force on the shear face; FN and FN are the normal forces of the shear plane and the tool-chip interface, respectively; the combined force of the normal force F N at the shear plane and the cutting force F s at the shear plane and the combined force of the normal force F n at the tool-chip interface and the friction force F f at the tool-chip interface are a pair of balanced forces; the chip forming force F R is split into F c and F t in the cutting direction and perpendicular to the cutting direction. θ is the angle between FR and AB; σAB represents the shear plane average rheological stress.
The speed and displacement increment of any point on a to B along the cutting direction and perpendicular to the cutting direction are respectively:
Wherein: v is the cutting speed; Δs 1 is the vertical height between EF and CD.
Any particle velocity in the first deformation zone is related to the average shear strain rate in the shear zone:
substituting the formula (7) and the formula (8) into the above formula (9) can obtain an average shear strain rate expression:
By iteratively calculating the shear angle phi, determining the shear angle phi based on the balance conditions of the shear region, the average equivalent strain and equivalent strain rate of any particle at the shear plane AB can be expressed by:
from the velocity vector relationship of fig. 2, the chip material flow velocity V c and the material flow velocity V s of the shear plane can be found:
based on Oxley cutting theory, average temperature of the shear zone:
Wherein: t r is the temperature of the workpiece, eta is the average temperature coefficient, and 0.9 is taken in analysis; ρ is the material density; c w specific heat capacity, wherein beta is the ratio of the shear deformation heat conduction workpiece materials of the first deformation zone of the shear zone, is calculated as follows:
Wherein: kw is the thermal conductivity.
Since the workpiece plastic deformation results in a high strain, high strain rate, high temperature cutting environment at the shear band, in the Oxley theoretical model, the S32760 bi-phase constitutive model is used to predict the rheological stress in the shear region:
The included angle between F n and F r in the shear zone is the friction angle, which can be used And (5) calculating. According to Oxley theory, it is possible to obtainShear angle/>, calculated from iterationThe included angle theta can be obtained.
The first deformation region strain rate constant C 0, considering the influence of material strain from the material work hardening mechanism, has the expression:
Wherein: c Oxley is the first deformation zone shear band aspect ratio; a JC、BJC and n JC are JC constitutive parameters, respectively.
In an Oxley right angle cutting model under the coupling action of cutting heat and cutting force, for iterative calculation of the temperature of a cutting zone, the rheological stress at the initial temperature of the cutting zone is supposed, the component force in the cutting zone is calculated according to the obtained rheological stress, then the temperature of the cutting zone is updated by using a balance temperature formula of the cutting zone, and the process is repeated until the difference between the updated temperature and the temperature of the cutting zone is smaller than 0.1 ℃, namely the temperature is regarded as the temperature of the cutting zone. And calculating the rheological stress at the shear band AB according to the output shear band temperature, the shear band equivalent strain and the shear band strain rate. F R is finally calculated and other force components are analyzed based on the geometric relationship of the equally divided shearing zones.
(3) Tool-chip interface analysis
The equivalent strain and equivalent strain rate of the tool-chip interface are:
wherein: h tc is the tool-chip contact length.
The average temperature T int of the tool-chip interface is expressed as:
Tint＝Tr+ΔTSZ+ψΔTM (22)
Wherein: psi is a correction coefficient; deltat M is the maximum temperature rise in the chip; deltaT C is the average temperature rise in the chip; deltat SZ is the first deformation zone temperature rise.
(3) Multi-physical field extraction process
Due to the shearing angle of the shearing zoneThe shear region strain rate coefficient C Oxley, the ratio delta of the second deformation region thickness to the chip thickness, changes with the cutting condition, the material property and the tool rake angle, so three variable ranges are set as the iterative ranges of the three, namely delta epsilon [0.005,0.2], C Oxley epsilon [2,10],/>, respectively
From the shear plane geometry analysis, the cutting force (F c) is known:
Fc＝FR cos(λ-α) (25)
The positive stress σ' N at point B in fig. 2 can be found in combination with the average rheological stress at the shear plane:
Assuming that the tool-chip interface stress is uniformly distributed, the resulting tool-chip interface stress τ int and stress σ N are expressed as:
(4) Extraction of shear zone multiple physical field distribution
Extracting shearing angles according to the model of the equally divided shearing area of the right-angle cuttingFirst deformation zone aspect ratio C Oxley, second deformation zone thickness to cut thickness ratio delta, shear zone temperature T AB, shear zone strain ε AB, shear zone strain rate/>Shear stress σ AB.
TABLE 1 Multi-physical field distribution in shear zone at different cutting levels
2. The two-phase stress solving method of the two-phase material comprises the following steps:
In the cutting S32760 process, two phases of the shearing area are subjected to severe plastic deformation, and the difference of mechanical properties of the two phases of materials is different from an evolution form, so that the processing hardening degree of the two phases is greatly different, and therefore, the difference of dynamic mechanical behaviors of the two phases in the cutting process is revealed by analyzing the influence rule between the cutting amount and the microhardness of the two phases.
As can be seen from the microhardness measurement of two phases of the matrix, the matrix has higher ferrite phase microhardness, which accords with the characteristic of higher ferrite hardness in S32760, and the two phases after cutting are subjected to plastic deformation, so that the work hardening degrees are greatly different.
TABLE 2 two-phase work hardening in shear zone at different feed rates
It can be seen from fig. 3 that the micro-hardness of the austenite phase and the ferrite phase of the chip decreases with increasing feed amount, and from table 2 that the work hardening degree of the two phases also decreases with increasing feed amount, the shear strain decreases with it, the average shear strain rate decreases with it, the hardening degree decreases, and the temperature is substantially unaffected, so the temperature-dominated heat softening effect is substantially unchanged, while with increasing feed amount the work hardening effect of the two phases decreases while the temperature-dominated heat softening effect is unchanged, so the work hardening degree of the two phases in the shear zone decreases with it.
S32760 is under the action of external forces such as tool extrusion and friction in the cutting process, and under the action of force thermal coupling, the rheological stress of the workpiece material in the shearing area generally has a strain hardening effect, a strain rate strengthening effect and a thermal softening effect. The strain hardening effect means that the rheological stress of a material increases with increasing strain; the strain rate strengthening effect means that the rheological stress of the material increases with the increase of the strain rate; the heat softening effect is then an indication that the rheological stress of the material will decrease with increasing temperature. The rheological stress is proportional to the microhardness of the material. Therefore, analysis S32760 of the shear zone two-phase rheological stress requires consideration of the relationship between shear zone temperature, strain rate.
Based on the mechanics of the material, the vickers microhardness value is proportional to the rheological stress, and therefore:
HV＝Cσ (28)
Wherein: c is a constant.
Based on the above equation, predicting the microhardness of two phases requires knowing the rheological stress of the two phases, which can be approximated as shear stress.
The precondition of the stress mixing rule is that the strains of two phases in the material deformation process are assumed to be the same, but in a quasi-static stretching experiment or a dynamic compression experiment, the two phases have competitive coupling effect in the plastic deformation process due to the huge difference of mechanical properties of the two phases. Therefore, the general processing method of the multiphase material is adopted, namely, the two-phase strain is expressed in the form of a mixing law on the basis of the two-phase stress mixing rule.
σ(ε)＝F·σ1(ε1)+(1-F)·σ2(ε2) (29)
ε＝F·ε1+(1-F)·ε2 (30)
Wherein: epsilon 1、ε2 is the strain value of the austenite phase and the strain value of the ferrite phase, respectively.
At this time, the two-phase ratio in the S32760 matrix needs to be considered, so that the S32760 matrix is observed by using an SEM scanning electron microscope, and the metallographic structure diagram of the S32760 matrix at 500 times is analyzed (as shown in fig. 23).
Analysis shows that the volume fraction ratio of the austenite phase to the ferrite phase is 23/27, so f=0.46.
The shear strain of the austenitic phase and the shear strain of the ferritic phase are shown in table 3.
TABLE 3 shear zone two-phase shear strain and shear stress
As can be seen from fig. 4, comparing groups 1-3 and 4-6, it can be seen that austenite correspondingly increases with decreasing cutting speed, and ferrite phase strain decreases with increasing cutting speed. As can be seen from fig. 5, the austenitic phase and ferritic phase rheological stresses increase with increasing cutting speed for the comparison of groups 1-3 and 4-6.
3. The construction method of the two-phase microhardness calculation model of the two-phase material comprises the following steps:
(1) Influence rule of cutter rake angle and cutting amount on chip two-phase microhardness
TABLE 4 predicted values of chip two-phase microhardness for different rake angles and different cutting rates
Based on Table 4, FIG. 6 shows the microhardness of austenite phase and ferrite phase at different cutting speeds with a feed rate of 0.3 mm/r.
It can be seen from fig. 6 that the two-phase microhardness increases with increasing cutting speed.
Based on Table 4, FIG. 7 shows the microhardness of the austenite phase and the ferrite phase at different feed rates of 106 m/min.
It can be seen from fig. 7 that the two-phase microhardness decreases with increasing feed rate under the same cutting speed conditions.
Based on table 4, fig. 8 is a graph showing the law of influence of different rake angles on shear strain in the shear zone.
As can be seen from fig. 8, the shear zone strain gradually decreases with increasing rake angle, because the greater the rake angle, the sharper the cutting edge and the less the compression of the cutting layer. Thus, the plastic deformation of the workpiece decreases with increasing tool rake angle.
As can be seen from fig. 9, the average shear strain rate in the shear zone gradually decreases as the tool rake angle increases, and the tool rake angle directly affects the magnitude of the shear strain rate.
As can be seen from fig. 10, as the tool rake angle increases, the average temperature in the shear zone decreases.
As can be seen from fig. 11, as the rake angle increases, the microhardness of the austenite phase and the ferrite phase increases.
(2) Two-phase microhardness prediction model considering cutter rake angle and cutting amount
In the actual machining process, the multi-physical field distribution of the shearing area in the cutting process is difficult to extract, so that the two-phase microhardness prediction model considering the front angle of the cutter and the cutting amount is established by taking the multi-physical field distribution as an independent variable and the two-phase microhardness as a dependent variable from the aspects of the front angle of the cutter and the cutting amount.
An exponential empirical model was established taking into account the S32760 austenitic phase and ferritic phase microhardness of the cutting elements, expressed as:
Wherein: HV * 1 is the predicted value of the microhardness of the austenite phase, and HV * 2 is the predicted value of the microhardness of the ferrite phase; z 1,Z2 is a coefficient related to cutting conditions and the like; and p, q and m are correlation coefficients.
The regression equation of the multi-objective optimization model for obtaining the microhardness values of the austenite phase and the ferrite phase is as follows:
HV* 1＝25.3581v0.1307f -0.1632α0.7030 (33)
HV* 2＝119.152v0.0372f -0.0696α0.3291 (34)
The validity of the regression equation model thus obtained was checked for significance, and the test structure thus obtained was shown in Table 5.
TABLE 5 examination of statistics of two-phase microhardness regression models
The test times are n=8, the number of independent variables m=3, the selected cutting speed, the feed amount and the significance level of the cutter front angle are alpha=0.05, F 0.05 (3, 4) =6.59 can be known according to a query F distribution critical value table, the statistic F value obtained by the regression equation of the two-phase microhardness is larger than the critical value 4.07 through analysis of variance, the corresponding P value is smaller than 0.05, and finally the established regression equation of the two-phase microhardness can be proved to be significant.
4. The processing technology method of the duplex stainless steel based on the consistency of the two-phase hardness distribution comprises the following steps:
(1) Optimization of rough machining process parameters
In combination with the stability of a process system in the actual processing process, the process parameter range in the practical processing is selected by considering that the rough processing feed is larger and the cutting speed is lower, so that the process parameter range is used as a constraint condition of consistency of the two-phase microhardness, and the specific parameter range is as follows:
TABLE 6 optimized cutting volume and tool rake based on two-phase microhardness consistency
As can be seen from fig. 12, when the differential microhardness of the two phases of the chip is minimum, the feeding amount is continuously reduced with increasing cutting speed, probably because the increasing cutting speed leads to increasing shear strain in the shear region, increasing average shear strain rate, continuously increasing average temperature, and increasing feeding amount leads to decreasing shear strain in the shear region, decreasing average shear strain rate, and insignificant temperature change, at which time the average strain rate and average temperature in the shear region are increased, while the shear strain is decreasing, the increasing degree of rheological stress caused by increasing strain rate is almost equal to the decreasing degree of rheological stress caused by decreasing strain and increasing temperature, so as the cutting speed and feeding amount are increased, the ratio of rheological stress of the two phases is unchanged, while the microhardness is proportional to the rheological stress, and therefore the differential microhardness of the two phases is insignificant.
As can be seen from Table 6, the two phases have consistent microhardness distribution, and the difference between the two phases is 1.3596HV 0.05 at maximum under the rough machining process parameters, and the microhardness of the two phases is in the range of 379-390HV 0.05. When the difference in the two-phase microhardness is minimum, the ferrite phase microhardness is continuously reduced with the increase of the cutting speed, while the austenite phase microhardness has no obvious tendency.
TABLE 7 two-phase microhardness values
The two-phase microhardness under various cutting conditions in table 6 is predicted by a two-phase microhardness prediction model, and as shown in table 7, the difference between the two-phase microhardness of 1-6 groups is no more than 16HV 0.05 and 13HV 0.05 at the minimum, so that the cutting amount optimized based on the consistency of the two-phase microhardness in the two-phase microhardness empirical model considering the cutting amount meets the standard of consistency of the two-phase microhardness distribution.
(2) Optimization of finishing process parameters
In combination with the stability of a process system in the actual processing process, the small feeding amount and the high cutting speed of finish machining are considered, so that the process parameter range in the practical processing is selected as a constraint condition of consistency of the two-phase microhardness, and the specific parameter ranges are as follows:
The pre-cutting and cutting amounts of the tools obtained after optimization of consistency of the two-phase microhardness distribution are shown in Table 8. As can be seen from Table 8, the two phases have consistent microhardness distribution, and the difference between the two phases is 0.8892HV 0.05 at maximum under the finishing process parameters, and the microhardness of the two phases is in the range of 352-359HV 0.05.
Table 8S32760 finishing process parameters
Table 9 two-phase microhardness values
The two-phase microhardness under various cutting conditions in table 8 is predicted by a two-phase microhardness prediction model, and as shown in table 9, the difference between the two-phase microhardness of 1-3 groups is not more than 18HV 0.05 at the highest and 16HV 0.05 at the smallest, so that the cutting amount optimized based on the consistency of the two-phase microhardness in the two-phase microhardness empirical model considering the cutting amount meets the consistency standard of the two-phase microhardness distribution.
Unlike the already disclosed technology: the existing solving of rheological stress in cutting two-phase material shearing area is to combine the rheological stress of austenite phase and ferrite phase together, and not solve the two-phase stress of the two-phase material respectively, neglecting the competitive coupling phenomenon of the two-phase material in plastic deformation process, and the invention respectively models the two-phase stress of the two-phase material based on stress mixing rule in consideration of multi-physical field distribution and the competitive coupling phenomenon of the two-phase material in cutting process, and solves the two-phase stress of the two-phase material respectively.
The existing duplex stainless steel processing technology does not consider consistency of microhardness distribution of austenite phase and ferrite phase in chips, and only focuses on modification of the cutting tool rake angle or cutting amount. The invention establishes a two-phase microhardness prediction model considering the cutter front angle and the cutting amount, and reveals the influence rule of the cutter front angle and the cutting amount on microhardness. Based on the established two-phase microhardness prediction model, under the condition of fully considering the consistency of two-phase hardness distribution, the matching relation between the front angle of the cutter and the cutting dosage is obtained, and the processing technology of the two-phase stainless steel is optimized.
Compared with the prior art, the invention has the beneficial effects that: the invention provides a duplex stainless steel processing technology based on consistency of two-phase hardness distribution, which aims at the problem that the microhardness difference between an austenite phase and a ferrite phase in a shearing area in the S32760 cutting process is large. And extracting variables such as strain, strain rate, temperature and the like of a shear band by combining with shear deformation of a shear region, respectively modeling the two-phase stress of the two-phase material based on a stress mixing rule, and solving the two-phase stress of the two-phase material. And the influence rule of the two-phase stress distribution of the two-phase material on the two-phase microhardness is revealed through the related knowledge of the material mechanics. And a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount is established by combining the microhardness and plastic strain relation, so that the problem of uncertain distribution of the two-phase microhardness is solved.
Taking the difference between the micro-hardness of the austenite phase and the micro-hardness of the ferrite phase as an objective function, taking the minimum absolute value of the difference between the micro-hardness of the austenite phase and the micro-hardness of the ferrite phase as a constraint condition, adopting a genetic algorithm to carry out optimizing solution on a model, and finally obtaining the cutter rake angle and the cutting amount with optimal consistency of the micro-hardness of the two phases; during finish machining, the front angle of the cutter ranges from 3 to 20 degrees, the feeding amount ranges from 0.1mm/r to 0.3mm/r, and the cutting speed ranges from 200m/min to 250m/min.
Drawings
FIG. 1 is a logical block diagram of the present invention; FIG. 2 is a schematic view of a right angle cut shear zone according to the present invention; FIG. 3 is a schematic view of the microhardness of the austenitic phase and ferritic phase at varying feed rates of 106m/min for the cutting speed of the present invention; FIG. 4 is a schematic diagram of the strains of the austenitic and ferritic phases of the present invention; FIG. 5 is a schematic view of the shear stresses of the austenitic and ferritic phases of the present invention; FIG. 6 is a schematic representation of the microhardness of the austenitic phase and ferritic phase at different cutting speeds with a feed rate of 0.3mm/r according to the present invention; FIG. 7 is a schematic representation of the microhardness of the austenitic phase and the ferritic phase at varying feed rates of 106m/min for the cutting speed of the present invention; FIG. 8 is a schematic diagram showing the effect of different rake angles on shear strain in the shear zone according to the present invention; FIG. 9 is a graph showing average shear strain rates in the shear zone for different tool rake angles at a cutting speed of 106m/min and a feed rate of 0.3mm/r in accordance with the present invention; FIG. 10 is a graph showing average temperatures in the shearing area for different tool rake angles at a cutting speed of 106m/min and a feed rate of 0.3mm/r in accordance with the present invention; FIG. 11 is a schematic view of the microhardness of the austenite phase and ferrite phase at different tool rake angles for a cutting speed of 106m/min at a feed rate of 0.3mm/r in accordance with the present invention; FIG. 12 is a schematic illustration of two-phase microhardness at different cutting rates for a tool rake angle of 20 according to the present invention; FIG. 13 is a graph showing raw data of cutting force measured by a right angle cutting test with a cutting speed of 214mm/min and a feed rate of 0.3mm in accordance with the present invention; FIG. 14 is a diagram of filtered data according to the present invention; FIG. 15 is a comparative schematic diagram of the cutting force of experimental observation Fcx with a feed rate of 0.3mm/r according to the present invention; FIG. 16 is a comparative schematic diagram of experimental observed Fcy cutting force with feed of 0.3mm/r according to the present invention; FIG. 17 is a comparative schematic diagram of the cutting force of experimental observation Fcx with a feed rate of 0.4mm/r according to the present invention; FIG. 18 is a comparative schematic diagram of experimental observed Fcy cutting force with feed of 0.4mm/r according to the present invention; FIG. 19 is a graphical representation of the microhardness of the austenitic phase and ferritic phase of the square cut S32760 chip of the present invention as a function of cutting speed; FIG. 20 is a graph showing the thickness ratio of the second deformation zone at different cutting speeds of 0.3mm/r at the feed rate according to the present invention; FIG. 21 is a three-dimensional view of a diamond right rectangular pyramid indenter of the present invention; FIG. 22 is a schematic illustration of a microhardness test in accordance with the present invention; FIG. 23 is a diagram showing the metallographic structure of the S32760 matrix at 500 times according to the present invention; FIG. 24 is a gold phase diagram of a two-phase microhardness indentation of chips of Experimental group Nos. 1,2, and 3 of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a duplex stainless steel processing technology based on the consistency of two-phase hardness distribution, which comprises the following steps:
s1: based on a stress mixing rule, a two-phase stress solving model of the two-phase material is established, and the two-phase stress of the two-phase material is distinguished and solved;
S2: establishing a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount, and revealing the influence rule of the front angle of the cutter and the cutting amount on the two-phase microhardness;
S3: based on the established two-phase microhardness resolving model, the influence rule of the cutter rake angle and the cutting amount on the two-phase microhardness distribution characteristics in the cutting chip is revealed, the matching relation of the cutter rake angle and the cutting amount is obtained under the condition that the two-phase microhardness distribution is consistent, and the processing technology of the two-phase stainless steel is optimized.
Example 1. Shear zone multiple physical field distribution extraction method:
(1) Shear plane analysis
The respective cutting force components and chip thickness t 2 are obtained according to the geometrical relationship of the shearing zone and the equilibrium condition of the tool-chip contact zone:
Ft＝FR sin(λ-α) (1)
Ff＝FR sinλ (2)
Fn＝FR cos(λ) (3)
FN＝FR sinθ (5)
wherein: alpha is the front angle of the cutter; Is the included angle between the shearing surface AB and the cutting speed direction, namely the shearing angle; lambda is the friction angle; t 1 is the undeformed chip thickness; w is the cutting width; f c and F t are components of the chip forces in the cutting direction and perpendicular to the cutting direction; f f is the friction of the tool-chip interface; f s is the cutting force on the shear plane; f N and F n are the normal forces of the shear plane and the tool-chip interface, respectively. The combined force of the normal force F N at the shear plane and the cutting force F s at the shear plane and the combined force of the normal force F n at the tool-chip interface and the friction force F f at the tool-chip interface are a pair of balanced forces; the chip forming force F R is split into F c and F t in the cutting direction and perpendicular to the cutting direction. θ is the angle between F R and AB; σ AB represents the shear plane average rheological stress.
The speed and displacement increment of any point on a to B along the cutting direction and perpendicular to the cutting direction are respectively:
Wherein: v is the cutting speed; Δs 1 is the vertical height between EF and CD.
In FIG. 2, the velocity component of any particle in the first deformation zone in the shear zone has the following relationship with the average shear strain rate in the shear zone:
substituting the formula (7) and the formula (8) into the above formula (9) can obtain an average shear strain rate expression:
by iteratively calculating the shear angle Determining shear angle/>, based on a shear zone balance conditionThe average equivalent strain and equivalent strain rate of any particle at the shear plane AB can be expressed by the following formula:
assuming that the shear deformation occurs at the shear plane, the workpiece becomes a chip by the shear deformation, and the workpiece material that would otherwise move with the tool is rapidly passed through the shear zone to become a chip due to the increase in cutting speed, and this abrupt change in speed is referred to as the shear speed. From the velocity vector relationship of fig. 2, the chip material flow velocity V c and the material flow velocity V s of the shear plane can be found:
the rheological stress is temperature dependent, and from the rheological stress the shear stress can be calculated. The temperature at AB is iteratively calculated to a steady state in order to obtain the shear stress. Based on Oxley cutting theory, the average temperature of the shear zone is:
Wherein: t r is the temperature of the workpiece, eta is the average temperature coefficient, and 0.9 is taken in analysis; ρ is the material density; c w specific heat capacity, wherein beta is the ratio of the shear deformation heat conduction workpiece materials of the first deformation zone of the shear zone, is calculated as follows:
wherein: k w is the heat conductivity.
Since the workpiece plastic deformation results in a high strain, high strain rate, high temperature cutting environment at the shear band, the S32760 bi-phasic constitutive model is used to predict the rheological stress in the shear zone:
The included angle between F n and F r in the shear zone is the friction angle, which can be used And (5) calculating. According to Oxley theory, it is possible to obtain/>Shear angle/>, calculated from iterationThe included angle theta can be obtained.
The first deformation region strain rate constant C 0, considering the influence of material strain from the material work hardening mechanism, has the expression:
Wherein: c Oxley is the first deformation zone shear band aspect ratio; a JC、BJC and n JC are JC constitutive parameters, respectively.
In an Oxley right angle cutting model under the coupling action of cutting heat and cutting force, for iterative calculation of the temperature of a cutting zone, the rheological stress at the initial temperature of the cutting zone is supposed, the component force in the cutting zone is calculated according to the obtained rheological stress, then the temperature of the cutting zone is updated by using a balance temperature formula of the cutting zone, and the process is repeated until the difference between the updated temperature and the temperature of the cutting zone is smaller than 0.1 ℃, namely the temperature is regarded as the temperature of the cutting zone. And calculating the rheological stress at the shear band AB according to the output shear band temperature, the shear band equivalent strain and the shear band strain rate. F R is finally calculated and other force components are analyzed based on the geometric relationship of the equally divided shearing zones.
(2) Tool-chip interface analysis
Under the extrusion friction of the rake face, the cutting chips close to one side of the rake face are subjected to shearing deformation again, crystal grains are elongated and fibrillated along the direction of the rake face, and the thickness of a fibrillated area is the thickness (delta S 2) of a second deformation area, as shown in fig. 2.Δs 2＝δt2, δ is the ratio of the second deformation zone thickness to the chip thickness that is deformed after cutting. The equivalent strain and the equivalent strain rate of the knife-chip interface can be known:
wherein: h tc is the tool-chip contact length, which can be calculated using the moment balance formula of the shear plane:
The average temperature T int of the tool-chip interface is expressed as:
Tint＝Tr+ΔTsz+ψΔTM (22)
wherein: psi is a correction coefficient, and is taken as 0.6; deltat M is the maximum temperature rise in the chip; deltaT C is the average temperature rise in the chip; deltat sz is the first deformation zone temperature rise.
And the rheological stress of the knife-chip contact interface is predicted by using an S32760 biphase constitutive model with the characteristics of rheological stress at the shearing band:
The right angle cutting experiments were as follows:
In order to verify the right-angle cutting model, a right-angle cutting test platform is built, and the reliability of the cutting force analysis model of the right-angle cutting S32760 duplex stainless steel is observed.
Right-angle cutting test platform with bar size ofAnd (3) clamping the bar by using a three-jaw clamp, centering, roughly turning a smooth surface according to the feeding amount of 1mm/r, then grooving the bar by using a grooving cutter with the cutter width of 3mm, wherein the groove depth is 3mm, the groove width is 3mm, the interval is 2mm, an annular convex surface with the width of 2mm is reserved between each groove, and a right-angle cutting experiment is carried out on each annular convex surface according to the test parameters shown in the following table. Excircle driving and grooving operations were performed using a C6136HK lathe.
The force measuring instrument used for right angle cutting is a KiSTLER piezoelectric force meter 9139AA, and the force measuring instrument is arranged on the tool rest of the numerical control machine tool. The force measuring instrument can measure cutting force in three directions in the cutting process, and each group of experiments are repeated three times and an average value is obtained in order to ensure the accuracy of the measurement result. To verify the accuracy of the cutting force prediction model, the cutting test parameters are shown in table 10.
Table 10 cutting amount for right angle cutting test
S32760 right angle cuts the parameters required by the shear zone prediction model, as shown in Table 11.
TABLE 11S 32760 Material parameters of cutting model
The cutting amount of table 11 and the S32760 material properties of table 11 were input according to the right angle cutting equally divided shearing area model, and the predicted cutting force values are shown in table 12. The cutting force measured by the right angle cutting test is shown in table 12. Fig. 13 is raw data of cutting force measured by a right angle cutting test with a cutting speed of 214mm/min and a feed amount of 0.3mm, and fig. 14 is data after filtering.
Table 12 test cutting force vs. model predictive cutting force
It can also be seen from fig. 15-18 that the model of the equal cut area for right angle cutting predicts a relatively accurate cutting force, wherein the cutting force F cx has a maximum prediction error of 2.7%, a minimum prediction error of 0.7%, and the cutting force F cy has a maximum prediction error of 10.7% and a minimum prediction error of 1.7% when the feed rate is 0.3 mm/r. When the feed amount was 0.4mm/r, the maximum prediction error of the cutting force F cx was 4.4%, the minimum prediction error was 3.9%, the maximum prediction error of the cutting force F cy was 6.0%, and the minimum prediction error was 0.6%. The average error of cutting force predictions was 2.9% and that of cutting force F cy was 4.6% compared to the test cutting force F cx. As can be seen from fig. 15-18, the cutting force predictions are more accurate with less error than the test data.
As can be seen from comparison of fig. 15 to 18, both the increase in cutting speed and the increase in the feed amount increase the cutting force, but the effect of the feed amount on the cutting force is more remarkable.
(3) The multi-physical field extraction process comprises the following steps:
due to the shearing angle of the shearing zone The shear region strain rate coefficient C Oxley, the ratio delta of the second deformation region thickness to the chip thickness, changes with the cutting condition, the material property and the tool rake angle, so three variable ranges are set as the iterative ranges of the three, namely delta epsilon [0.005,0.2], C Oxley epsilon [2,10],/>, respectivelyAccording to Oxley cutting theory, when the output satisfies three equilibrium conditions, the calculation will terminate: stress balance at the tool-cutting interface, wherein the tool-cutting interface tangential stress (τ int) is equal to the rheological stress (σ chip) in the chip; second, stress balance at the nose, i.e., with a reasonably calculated nose interface normal stress (σ N) equal to a normal stress calculated with nose stress boundary conditions (σ' N); third, the principle of minimum cutting force (F c). Therefore, according to three balance conditions of the Oxley theory, the method is used as the judgment basis of three variable iterations. From this, the tool-cutting interface tangential stress (τ int), the nose interface normal stress (σ N), the nose stress boundary condition calculated normal stress (σ N), and the cutting force (F c) are calculated.
F c can be calculated from the shear zone geometry:
Fc＝FR cos(λ-α) (26)
The positive stress σ' N at point B in fig. 2 can be found in combination with the average rheological stress at the shear plane:
Assuming that the tool-chip interface stress is uniformly distributed, the resulting tool-chip interface stress τ int and stress σ N are expressed as:
based on the absolute value of the difference between the tangential stress (τ int) of the tool-cutting interface and the rheological stress (sigma chip) of the tool-cutting interface, the shearing angle is determined Taking the value nearest to both. At this time, according to the obtained shear angle/>And repeatedly calculating various parameters of the shearing area, then solving the normal stress (sigma N) of the tool tip interface and the normal stress (sigma' N) calculated by the tool tip stress boundary condition, taking the absolute value of the difference value of the normal stress and the normal stress as the basis for judging C Oxley, and taking the closest value of the normal stress and the normal stress by C Oxley. And continuously repeatedly calculating various parameters of the shearing area, comparing the cutting force F c, selecting F c to be the smallest, and determining the delta value. From this, a model of the chip forces under different cutting conditions, material properties and tool geometry is built up and specific values of the three variables can be determined.
(4) Extracting the distribution of multiple physical fields in a shearing area:
Extracting shearing angles according to the model of the equally divided shearing area of the right-angle cutting First deformation zone aspect ratio C Oxley, second deformation zone thickness to cut thickness ratio delta, shear zone temperature T AB, shear zone strain ε AB, shear zone strain rate/>Shear stress σ AB. The multi-physical field distribution in the shear zone is shown in table 2.
Implementation example 2. Two-phase material two-phase stress solving method:
In the cutting S32760 process, two phases of the shearing area are subjected to severe plastic deformation, and the difference of mechanical properties of the two phases of materials is different from an evolution form, so that the processing hardening degree of the two phases is greatly different, and therefore, the difference of dynamic mechanical behaviors of the two phases in the cutting process is revealed by analyzing the influence rule between the cutting amount and the microhardness of the two phases.
The feed amount was 0.3mm/r, and the microhardness and hardening degree of the austenitic phase and the ferritic phase of the chip were shown in Table 13 at various cutting speeds.
TABLE 13 two-phase microhardness in shear zone and thickness ratio in second deformation zone at different cutting speeds
According to comparison of test data, fig. 19 is a graph showing the change of microhardness of austenite phase and ferrite phase of the chip of the right angle cutting S32760 with cutting speed.
TABLE 14 two-phase work hardening degree in shear zone at different cutting speeds
FIG. 20 is a graph showing the variation of the thickness ratio of the second deformation zone at different cutting speeds with a feed rate of 0.3mm/r according to Table 14.
As can be seen from the microhardness measurement of two phases of the matrix, the matrix has higher ferrite phase microhardness, which accords with the characteristic of higher ferrite hardness in S32760, and the two phases after cutting are subjected to plastic deformation, so that the work hardening degrees are greatly different.
It can be seen from fig. 3 that the micro-hardness of the austenite phase and the ferrite phase of the chip decreases with increasing feed amount, and from table 2 that the work hardening degree of the two phases also decreases with increasing feed amount, the shear strain decreases with it, the average shear strain rate decreases with it, the hardening degree decreases, and the temperature is substantially unaffected, so the temperature-dominated heat softening effect is substantially unchanged, while with increasing feed amount the work hardening effect of the two phases decreases while the temperature-dominated heat softening effect is unchanged, so the work hardening degree of the two phases in the shear zone decreases with it.
S32760 is under the action of external forces such as tool extrusion and friction in the cutting process, and under the action of force thermal coupling, the rheological stress of the workpiece material in the shearing area generally has a strain hardening effect, a strain rate strengthening effect and a thermal softening effect. The strain hardening effect means that the rheological stress of a material increases with increasing strain; the strain rate strengthening effect means that the rheological stress of the material increases with the increase of the strain rate; the heat softening effect is then an indication that the rheological stress of the material will decrease with increasing temperature. The rheological stress is proportional to the microhardness of the material. Therefore, analysis S32760 of the shear zone two-phase rheological stress requires consideration of the relationship between shear zone temperature, strain rate.
Based on the mechanics of the material, the vickers microhardness value is proportional to the rheological stress, and therefore:
HV＝Cσ (28)
Wherein: c is a constant.
Based on the above equation, predicting the microhardness of two phases requires knowing the rheological stress of the two phases, which can be approximated as shear stress.
The precondition of the stress mixing rule is that the strains of two phases in the material deformation process are assumed to be the same, but in a quasi-static stretching experiment or a dynamic compression experiment, the two phases have competitive coupling effect in the plastic deformation process due to the huge difference of mechanical properties of the two phases. Therefore, the general processing method of the multiphase material is adopted, namely, the two-phase strain is expressed in the form of a mixing law on the basis of the two-phase stress mixing rule.
σ(ε)＝F·σ1(ε1)+(1-F)·σ2(ε2) (29)
ε＝F·ε1+(1-F)·ε2 (30)
Wherein: epsilon 1、ε2 is the strain value of the austenite phase and the strain value of the ferrite phase, respectively.
At this time, the two-phase ratio in the S32760 matrix needs to be considered, so that the S32760 matrix is observed by using an SEM scanning electron microscope, and the two-phase ratio is analyzed.
The volume fraction ratio of the austenitic phase to the ferritic phase is 23/27, so f=0.46.
The shear strain of the austenitic phase and the shear strain of the ferritic phase are shown in table 3.
As can be seen from fig. 4, comparing groups 1-3 and 4-6, it can be seen that austenite correspondingly increases with decreasing cutting speed, and ferrite phase strain decreases with increasing cutting speed. As can be seen from fig. 5, the austenitic phase and ferritic phase rheological stresses increase with increasing cutting speed for the comparison of groups 1-3 and 4-6.
Implementation example 3. Method for constructing two-phase microhardness calculation model of two-phase material
The test for the microhardness of S32760 chip is as follows:
The chips of the right angle cutting S32760 were collected in groups according to test numbers, and the chips of 6 groups of right angle cutting tests were tested, respectively, and the cutting amounts of the chips are shown in table 14. Because the chip size is small, the shape is required to be kept unchanged in the experimental process, and the surface layer is protected, so that the chip is inlaid with resin, and the chip is convenient to hold. In order to ensure that the embedded sample is free from pollution, the first step is to clean the cuttings to ensure that the cuttings are well adhered with the resin, and also prevent bubbles from influencing the dotting of the microhardness test press head. Cutting chips inlaid in resin are ground from coarse to fine by using No. 80, 320, 600, 1000, 1200, 1500 and 2000 abrasive paper, at least two crosses are ground back and forth by each abrasive paper, the abrasive paper with the size of more than 1000 and 4-5 cross rounds, wherein no grinding mark in the vertical direction can be seen by the naked eye. And spraying a proper amount of polishing agent on the polishing cloth, and polishing the embedded sample which is hand-held and ground according to the cross direction. During polishing, proper amount of water is added to prevent friction overheat and proper amount of polishing agent is also added. After polishing, a new polishing cloth is replaced for water polishing, so as to clean the polishing agent. And heating alcohol in an ultrasonic cleaner to clean the polished sample.
TABLE 15 test of cutting amount of microhardness of S32760 chip
Since the two phases are not seen under a metallographic microscope after the dual-phase stainless steel is polished, corrosion and color dipping are needed, 20ml of distilled water, 20ml of hydrochloric acid and 4g of hydrochloric acid are used for preparing corrosive liquid according to relevant knowledge of materials, a polished sample piece is put into a solution at room temperature to be etched for 30 seconds, and then the surface of the sample is cleaned to prepare for a subsequent microhardness experiment.
The basic principle of the micro Vickers hardness test is that a diamond regular rectangular pyramid pressure head with an included angle of 136 DEG (an included angle of 148 DEG and 6 '42') is formed on two opposite faces, and a three-dimensional diagram of the diamond regular rectangular pyramid pressure head is shown in FIG. 21. FIG. 22 is a schematic diagram showing a microhardness test, wherein the microhardness test is carried out by pressing the surface of a sample under a test force of 50N, holding for 10 seconds, then removing the test force, and measuring the diagonal length of the indentation, and obtaining the quotient of the Vickers hardness HV value (kgf/mm 2) by testing the tapered surface area.
The microhardness of the austenite phase and ferrite phase was measured in the shear band in the chip, and fig. 24 is a measurement chip area and measurement position. The region is a first deformation region of the shearing region, and the strain, the strain rate and the temperature of the first deformation region in the shearing region are extracted according to an analytical model of the shearing region which is equally divided by right-angle cutting, so that the mapping relation between multiple physical fields and two-phase microhardness is constructed.
(1) Influence rule of cutter rake angle and cutting amount on chip two-phase microhardness
TABLE 4 predicted values of chip two-phase microhardness for different rake angles and different cutting rates
It can be seen from fig. 6 that the two-phase microhardness increases with increasing cutting speed.
It can be seen from fig. 7 that the two-phase microhardness decreases with increasing feed rate under the same cutting speed conditions.
As can be seen from fig. 8, the shear zone strain gradually decreases with increasing rake angle, because the greater the rake angle, the sharper the cutting edge and the less the compression of the cutting layer. Thus, the plastic deformation of the workpiece decreases with increasing tool rake angle.
As can be seen from fig. 9, the average shear strain rate in the shear zone gradually decreases as the tool rake angle increases, which directly affects the magnitude of the shear strain rate.
As can be seen from fig. 10, as the tool rake angle increases, the average temperature of the shear zone decreases, and as the extrusion of the cutting layer decreases, the degree of deformation of the workpiece decreases, resulting in a decrease in the amount of heat generated by plastic deformation, the average temperature of the shear zone decreases.
As can be seen from fig. 11, as the rake angle increases, the microhardness of the austenitic phase and the ferritic phase increases.
(2) Two-phase microhardness prediction model considering cutter rake angle and cutting amount
In the actual machining process, the multi-physical field distribution of the shearing area in the cutting process is difficult to extract, so that the two-phase microhardness prediction model considering the front angle of the cutter and the cutting amount is established by taking the multi-physical field distribution as an independent variable and the two-phase microhardness as a dependent variable from the aspects of the front angle of the cutter and the cutting amount.
An exponential empirical model was established taking into account the S32760 austenitic phase and ferritic phase microhardness of the cutting elements, expressed as:
Wherein: HV * 1 is the predicted value of the microhardness of the austenite phase, and HV * 2 is the predicted value of the microhardness of the ferrite phase; z 1,Z2 is a coefficient related to cutting conditions and the like; and p, q and m are correlation coefficients.
The regression equation of the multi-objective optimization model for obtaining the microhardness values of the austenite phase and the ferrite phase is as follows:
HV* 1＝25.3581v0.1307f -0.1632α0.7030 (33)
HV* 2＝119.152v0.0372f -0.0696α0.3291 (34)
The validity of the regression equation model thus obtained was checked for significance, and the test structure thus obtained was shown in Table 5.
The test times are n=8, the number of independent variables m=3, the selected cutting speed, the feed amount and the significance level of the cutter front angle are alpha=0.05, F 0.05 (3, 4) =6.59 can be known according to a query F distribution critical value table, the statistic F value obtained by the regression equation of the two-phase microhardness is larger than the critical value 4.07 through analysis of variance, the corresponding P value is smaller than 0.05, and finally the established regression equation of the two-phase microhardness can be proved to be significant.
Example 4. Duplex stainless steel processing method based on two-phase hardness consistency:
(1) Optimization of rough machining process parameters
And obtaining the change rule of the cutting dosage and the cutting front angle of the micro-hardness value cutter of the austenite phase and the ferrite phase by analyzing the influence factors of the two-phase micro-hardness prediction model.
In combination with the stability of a process system in the actual processing process, the process parameter range in the practical processing is selected by considering that the rough processing feed is larger and the cutting speed is lower, so that the process parameter range is used as a constraint condition of consistency of the two-phase microhardness, and the specific parameter range is as follows:
According to the two-phase microhardness prediction model established above, taking the absolute value of the difference between the two-phase microhardness as a multi-objective optimization function, the optimization function of the cutting element is as follows:
Optimizing by using a genetic algorithm, and programming constraint conditions and an optimizing objective function as follows:
The formula (37) is used as a criterion for judging the consistency of the two-phase microhardness distribution, and is used as a consistency judgment coefficient of the two-phase microhardness distribution. Table 6 shows the cutting tool rake angle and the cutting amount obtained after the consistency optimization of the two-phase microhardness distribution.
As can be seen from fig. 12, when the differential microhardness of the two phases of the chip is minimum, the feeding amount is continuously reduced with increasing cutting speed, probably because the increasing cutting speed leads to increasing shear strain in the shear region, increasing average shear strain rate, continuously increasing average temperature, and increasing feeding amount leads to decreasing shear strain in the shear region, decreasing average shear strain rate, and insignificant temperature change, at which time the average strain rate and average temperature in the shear region are increased, while the shear strain is decreasing, the increasing degree of rheological stress caused by increasing strain rate is almost equal to the decreasing degree of rheological stress caused by decreasing strain and increasing temperature, so as the cutting speed and feeding amount are increased, the ratio of rheological stress of the two phases is unchanged, while the microhardness is proportional to the rheological stress, and therefore the differential microhardness of the two phases is insignificant.
As can be seen from Table 6, the two phases have consistent microhardness distribution, and the difference between the two phases is 1.3596HV 0.05 at maximum under the rough machining process parameters, and the microhardness of the two phases is in the range of 379-390HV 0.05. When the difference in the two-phase microhardness is minimum, the ferrite phase microhardness is continuously reduced with the increase of the cutting speed, while the austenite phase microhardness has no obvious tendency.
The two-phase microhardness under various cutting conditions in table 6 is predicted by a two-phase microhardness prediction model, and as shown in table 7, the difference between the two-phase microhardness of 1-6 groups is no more than 16HV 0.05 and 13HV 0.05 at the minimum, so that the cutting amount optimized based on the consistency of the two-phase microhardness in the two-phase microhardness empirical model considering the cutting amount meets the standard of consistency of the two-phase microhardness distribution.
(2) Optimization of finishing process parameters
In combination with the stability of a process system in the actual processing process, the small feeding amount and the high cutting speed of finish machining are considered, so that the process parameter range in the practical processing is selected as a constraint condition of consistency of the two-phase microhardness, and the specific parameter ranges are as follows:
the optimization process is similar to rough machining and will not be described in detail here.
The cutting tool rake angle and the cutting amount obtained after the consistency optimization of the two-phase microhardness distribution are shown in table 8. As can be seen from Table 8, the two phases have consistent microhardness distribution, and the difference between the two phases is 0.8892HV 0.05 at maximum under the finishing process parameters, and the microhardness of the two phases is in the range of 352-359HV 0.05.
The two-phase microhardness under various cutting conditions in table 8 is predicted by a two-phase microhardness prediction model, and as shown in table 9, the difference between the two-phase microhardness of 1-3 groups is not more than 18HV 0.05 at the highest and 16HV 0.05 at the smallest, so that the cutting amount optimized based on the consistency of the two-phase microhardness in the two-phase microhardness empirical model considering the cutting amount meets the consistency standard of the two-phase microhardness distribution.
In summary, compared with the prior art, the invention aims at the problem that the microhardness difference between the austenite phase and the ferrite phase in the shearing area in the S32760 cutting process is large. And extracting variables such as strain, strain rate, temperature and the like of a shear band by combining with shear deformation of a shear region, respectively modeling the two-phase stress of the two-phase material based on a stress mixing rule, and solving the two-phase stress of the two-phase material. And the influence rule of the two-phase stress distribution of the two-phase material on the two-phase microhardness is revealed through the related knowledge of the material mechanics. And a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount is established by combining the microhardness and plastic strain relation, so that the problem of uncertain distribution of the two-phase microhardness is solved.
Taking the difference between the micro-hardness of the austenite phase and the micro-hardness of the ferrite phase as an objective function, taking the minimum absolute value of the difference between the micro-hardness of the austenite phase and the micro-hardness of the ferrite phase as a constraint condition, adopting a genetic algorithm to carry out optimizing solution on a model, and finally obtaining the cutter rake angle and the cutting amount with optimal consistency of the micro-hardness of the two phases; during finish machining, the front angle of the cutter ranges from 3 to 20 degrees, the feeding amount ranges from 0.1mm/r to 0.3mm/r, and the cutting speed ranges from 200m/min to 250m/min.
Finally, it should be noted that: the foregoing description is only illustrative of the preferred embodiments of the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the present invention.

Claims (2)

1. A processing technology of duplex stainless steel based on stress mixing rule is characterized in that: the method comprises the following steps:
s1: based on a stress mixing rule, a two-phase stress solving model of the two-phase material is established, and the two-phase stress of the two-phase material is distinguished and solved;
the method for extracting the multi-physical field distribution in the shearing area comprises the following steps: predicting cutting force by analyzing the moment balance relation of the shearing area and combining an S32760 bi-phase constitutive model, and solving the cutting force by using the cutting amount; shearing face analysis; analyzing a cutter-chip interface; extracting multiple physical fields; extracting the distribution of multiple physical fields in the shearing area;
The two-phase stress solving method of the two-phase material comprises the following steps: in the cutting S32760 process, two phases of the shearing area are subjected to severe plastic deformation, and the difference of mechanical properties of the materials of the two phases is different from an evolution form, so that the processing hardening degree of the two phases is different, and the difference of dynamic mechanical behaviors of the two phases in the cutting process is revealed by analyzing the influence rule between the cutting consumption and the microhardness of the two phases;
S32760 is under the action of external forces such as tool extrusion, friction and the like in the cutting process, under the action of force thermal coupling, the rheological stress of the workpiece material in a shearing area generally has a strain hardening effect, a strain rate strengthening effect and a thermal softening effect, the rheological stress is in direct proportion to the microhardness of the material,
Based on the mechanics of the material, the vickers microhardness value is proportional to the rheological stress, and therefore:
HV＝Cσ
Wherein: c is a constant;
Based on the above, predicting the microhardness of two phases requires knowing the rheological stress of the two phases, and the rheological stress of the cuttings can be approximately regarded as shear stress;
The precondition of the stress mixing rule is that the strains of two phases in the material deformation process are assumed to be the same, and the two phases have competing coupling effects in the plastic deformation process due to the large difference of mechanical properties of the two phases, so that the general processing method of the multiphase material is adopted, namely, the strain of the two phases is expressed as a form of a mixing law on the basis of keeping the stress mixing rule of the two phases:
σ(ε)＝F·σ1(ε1)+(1-F)·σ2(ε2)
ε＝F·ε1+(1-F)·ε2
Wherein: epsilon 1、ε2 is the strain value of the austenite phase and the strain value of the ferrite phase respectively;
S2: establishing a two-phase microhardness resolving model considering the front angle of the cutter and the cutting amount, and revealing the influence rule of the front angle of the cutter and the cutting amount on the two-phase microhardness;
S3: based on the established two-phase microhardness resolving model, revealing the influence rule of the cutter rake angle and the cutting amount on the two-phase microhardness distribution characteristics in the cutting chip, obtaining the matching relation of the cutter rake angle and the cutting amount under the condition that the two-phase microhardness distribution is consistent, and optimizing the processing technology of the two-phase stainless steel;
the construction method of the two-phase microhardness calculation model of the two-phase material comprises the following steps:
influence rule of cutting tool rake angle and cutting amount on chip two-phase microhardness: the micro-hardness of two phases is continuously improved along with the continuous increase of the cutting speed;
The microhardness of two phases decreases with the increase of the feeding amount under the condition of the same cutting speed;
The strain of the shearing area gradually decreases with the increase of the rake angle, because the larger the rake angle is, the sharper the cutting edge is, and the extrusion of the cutting layer is gradually reduced, so that the plastic deformation of the workpiece decreases with the increase of the rake angle of the tool;
The average shear strain rate of the shearing area gradually decreases along with the increase of the front angle of the cutter, and the front angle of the cutter directly influences the magnitude of the shear strain rate;
As the front angle of the cutter increases, the average temperature of the shearing area is reduced;
As the rake angle increases, the microhardness of the austenitic phase and the ferritic phase increases continuously;
Two-phase microhardness calculation model considering cutter rake angle and cutting amount: from the aspects of the cutting tool rake angle and the cutting dosage, taking the cutting tool rake angle and the cutting dosage as independent variables, and taking the two-phase microhardness as dependent variables, establishing a two-phase microhardness calculation model considering the cutting tool rake angle and the cutting dosage, wherein an exponential empirical model considering the S32760 austenitic phase and the ferritic phase microhardness of the cutting elements is expressed as follows:
Wherein: HV x 1 is the predicted value of the microhardness of the austenite phase, HV x 2 is the predicted value of the microhardness of the ferrite phase; z 1,Z2 is a coefficient related to cutting conditions and the like; and p, q and m are correlation coefficients.
2. Use of a duplex stainless steel processing process based on stress mixing rules according to claim 1 in duplex stainless steel processing.
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