CN105975657A - Special-shaped plate part hot precision forging forming mould cavity correction method - Google Patents

Abstract

The invention discloses a special-shaped plate part hot precision forging forming mould cavity correction method. According to the method, a mathematic model, the profile of which deforms in the hot precision forging process on the basis of a force piece and a mould, is established; and the mathematic model comprises mould heat expansion td, force piece cold deflation tw, mould stress elastic expansion ed and force piece mould-out springback ew. The established mathematic model gives full consideration to various deformation factors in the hot precision forging process, so that the factors influencing the precision of the hot precision forging are well revealed; a mathematic functional expression is used for calculating mould cavity correction and the calculation method is simple, rapid and convenient for engineering application; and the correction method is high in correctness, and can be used for effectively improving the hot precision forging forming precision so as to decrease the subsequent precision machining margin and even satisfy the requirement for direct use.

Description

Special-shaped disk-like accessory hot precision forging mold cavity modification method

Technical field

The invention belongs to disk-like accessory finish forge processing technique field, be specifically related to a kind of special-shaped disk-like accessory hot precision forging mold cavity modification method.

Background technology

Disk-like accessory is extensively applied in various industrial products, and such as gear, flange, wheel and belt pulley etc., its design and manufacture level directly influence the quality of industrial products, and be related to the quality of equipment manufacture and the level of development of national economy.Disk-like accessory is due to its widespread demand, and it is machined with following features and requirement: product yield is big, so production cost and stock utilization are had strict demand, the accuracy of manufacture and properties of product is required height, to ensure that part has higher service life simultaneously.The general first hot forging forming blank of disk-like accessory processing technique at present, then complete through multistep Cutting Process, hold facility is many, long processing time, production efficiency are low, production cost is high and stock utilization is low, and metallic fiber is cut-off in cutting process, have impact on product quality performance.

The plasticity that hot finish forge is good when being to utilize metallic high temperature makes forging forming, i.e. utilizes the principle of metal plastic deformation, manufactures part according to metal-pressed machine manufacturing process.There is the features such as production efficiency height, stock utilization height, low cost and energy-conserving and environment-protective with hot forging processing part, variously-shaped and the part of size can be produced, and forging surface metal streamline is continuously and along piece surface contoured profile, part strength is high, the life-span is long, and the hottest study on precision forging technology is a kind of parts industry means of production with development potentiality.

Special-shaped disk-like accessory is complex-shaped, and there is the special-shaped shapes such as asymmetric, in heat forming processes, piece surface deflection everywhere is uneven, cause forming accuracy low, and many disk-like accessories are high to requirement on machining accuracy, as gear drive requires height to noise and transmission stability, therefore Involute gear profile accuracy is required harshness.In hot precision forging process, forging and mould are heated, stress deformation complicated, and machining accuracy is difficult to control to, and present stage, hot finish forge precision was typically at 0.1mm to 0.5mm.

Summary of the invention

The purpose of the present invention is aiming at the deficiency of above-mentioned technology, it is provided that a kind of special-shaped disk-like accessory hot precision forging mold cavity modification method, its accuracy is high, can be effectively improved hot precision forging precision, thus reduce subsequent fine allowance.

For achieving the above object, the special-shaped disk-like accessory hot precision forging mold cavity modification method designed by the present invention, comprise the steps:

1) building based on forging and mould the mathematical model of profile deformation in hot precision forging process, mathematical model includes mould pre-thermal expansion t_d, forging shrinkage t_w, mould stress elastic expansion e_dAnd resilience e after forging depanning_w；And set mold cavity original dimension and be Die cavity profile size and forging surface profile difference in size F, i.e. F=e as r, mold cavity original dimension R with the difference of forging final size r as R, forging final size_d+t_d+e_w-t_w；

2) and take arbitrfary point i on forging surface profile on Die cavity profile, and arbitrfary point i is r to centroid distance_i, try to achieve on Die cavity profile and the deformation values of arbitrfary point i on forging surface profile, i.e. pre-thermal expansion radial deformation value t of arbitrfary point i on Die cavity profile_d=t_d(r_i), the shrinkage of arbitrfary point i radially deformation values t on forging surface profile_w=t_w(r_i), stress elastic expansion radial deformation value e of arbitrfary point i on Die cavity profile_dr=e_dr(r_i) and circumferential deformation value e_{d θ}=e_{d θ}(r_i), on forging surface profile, the resilience of arbitrfary point i expands radial deformation value e_wr=e_wr(r_i) and circumferential deformation value e_{w θ}=e_{w θ}(r_i)；

3) it is about variable r with arbitrfary point i deformation values on forging surface profile on Die cavity profile_iExpression formula, so Die cavity profile size and forging surface profile difference in size F are about variable r_iFunctional expression, wherein radial dimension difference F_r=t_d(r_i)-t_w(r_i)+e_dr(r_i)+e_wr(r_i)=f_r(r_i), circumferential size difference F_θ=e_{d θ}(r_i)+e_{w θ}(r_i)=f_θ(r_i)；

4) set the parametric equation of the former contour line of mold cavity under cylindrical-coordinate system expression formula as

Wherein, g (t) contour line radial component, h (t) be contour line circumferential component, t be equation group parameter, then the Die cavity profile line parametric equation expression formula revised is as follows:

Wherein: radial component part g (t) brings Die cavity profile and forging surface profile radial dimension difference f into variable format_r(r_i), obtain correction term f of the Die cavity profile line parametric equation radial component revised_r[g(t)]；By 180/ π r_iIt is multiplied by f_θ(r_i) obtain correction term 180f of Die cavity profile line parametric equation circumferential component revised_θ(r_i)/πr_i；

5) according to step 4) the middle Die cavity profile line parametric equation processing mold revised.

Further, described step 1) in mould preheating expand t_dFor mold cavity before forging owing to mould preheating will occur thermal expansion the size that increases, mould stress elastic expansion e_dThe elastic expansion amount occurred under forging applies pressure for mold cavity, resilience e after forging depanning_wFor push rod by forging from mold ejection time forging's block dimension resilience swell increment, forging shrinkage t_wThe shrinkage amount occurred being cooled to room temperature from forging temperature for forging.

Further, described mold cavity original dimension R+ mould pre-thermal expansion t_d+ mould stress elastic expansion e_d=deformation rear mold cavity dimension R ', forging final size is resilience e after r+ forging depanning_w-forging shrinkage t_wForging's block dimension r ' after=deformation, and R '=r '.

Further, after described mould stress elastic expansion radial deformation and described forging depanning, the radial deformation of resilience can law and lame formula be expressed all in accordance with Generalized Hu, and after described mould stress elastic expansion circumferential deformation and described forging depanning, the circumferential deformation of resilience can be expressed by law all in accordance with Generalized Hu.

Compared with prior art, the invention have the advantages that

1) special-shaped disk-like accessory hot precision forging mold cavity modification method accuracy provided by the present invention is high, can be effectively improved hot precision forging precision, thus reduce subsequent fine allowance, even meet the requirement directly used；

2) mathematical model that the present invention is set up various deformation factors in taking into full account hot precision forging process, it is possible to well disclose and affect the factor of hot finish forge precision；

3) present invention uses mathematical functional expression to calculate mold cavity correction, computational methods simple and fast, facilitates engineer applied.

Accompanying drawing explanation

Fig. 1 is hot precision forging die die cavity profile and the deformation schematic diagram of forging surface profile in abnormal shape disk-like accessory of the present invention hot precision forging mold cavity modification method；

Fig. 2 is that the embodiment of the present invention hot finish forge double stack mold assembles schematic diagram；

Fig. 3 is the present embodiment Die cavity profile and forging surface profile radial dimension difference F_rResult of calculation figure；

Fig. 4 is the present embodiment Die cavity profile and forging surface profile circumferential size difference F_θResult of calculation figure；

Fig. 5 is the present embodiment hot finish forge forging precision testing result figure.

Detailed description of the invention

The present invention is described in further detail with specific embodiment below in conjunction with the accompanying drawings, it is simple to more clearly understand the present invention, but they do not constitute restriction to the present invention.

The invention discloses a kind of special-shaped disk-like accessory hot precision forging mold cavity modification method in conjunction with Fig. 1, comprise the steps:

1) building based on forging and mould the mathematical model of profile deformation in hot precision forging process, mathematical model includes four parts: mould pre-thermal expansion t_d, forging shrinkage t_w, mould stress elastic expansion e_dAnd resilience e after forging depanning_w, mould pre-thermal expansion t_dFor mold cavity before forging owing to mould preheating will occur thermal expansion the size that increases, mould stress elastic expansion e_dThe elastic expansion amount occurred under forging applies pressure for mold cavity, resilience e after forging depanning_wFor push rod by forging from mold ejection time forging's block dimension resilience swell increment, forging shrinkage t_wThe shrinkage amount occurred being cooled to room temperature from forging temperature for forging；And set mold cavity original dimension as R, forging final size as r, deform rear mold cavity dimension R '=mold cavity original dimension R+ mould pre-thermal expansion t_d+ mould stress elastic expansion e_d, resilience e after forging's block dimension r '=forging final size is r+ forging depanning after deformation_w-forging shrinkage t_w, now R '=r '；The difference of mold cavity original dimension R and forging final size r is Die cavity profile size and forging surface profile difference in size F, can be expressed as formula (1) according to above-mentioned influence factor and vector correlation thereof, i.e. difference in size F:

F=e_d+t_d+e_w-t_w (1)

2) and take arbitrfary point i on forging surface profile on Die cavity profile, and arbitrfary point i is r to centroid distance_i, try to achieve on Die cavity profile and the deformation values of arbitrfary point i on forging surface profile, then in formula (1), change in size t of the pre-thermal expansion radial deformation of arbitrfary point i on Die cavity profile_dFormula (2) can be expressed as according to object thermal expansion formula,

t_d=t_d(r_i) (2)

In formula (1), the shrinkage of arbitrfary point i radially deformation ruler cun change t on forging surface profile_wFormula (3) can be expressed as according to object thermal expansion formula,

t_w=t_w(r_i) (3)

In formula (1), on Die cavity profile, the stress elastic expansion deformation of arbitrfary point i is divided into radial deformation e_drWith circumferential deformation e_{d θ}, wherein radial dimension change can be expressed as formula (4) according to generalized Hooke law and lame formula, and circumferential size change cocoa is expressed as formula (5) according to generalized Hooke law,

e_dr=e_dr(r_i) (4)

e_{d θ}=e_{d θ}(r_i) (5)

In formula (1), on forging surface profile, the resilience dilatancy of arbitrfary point i is divided into radial deformation e_wrWith circumferential deformation e_{w θ}, wherein radial dimension change can be expressed as formula (6) according to generalized Hooke law and lame formula, and circumferential size change cocoa is expressed as formula (7) according to generalized Hooke law,

e_wr=e_wr(r_i) (6)

e_{w θ}=e_{w θ}(r_i) (7)

3), in formula (2) (7), Die cavity profile is about variable r with the expression formula of arbitrfary point i deformation on forging surface profile_iExpression formula, therefore, in formula (1), mold cavity overall size and forging surface profile difference in size F are about variable r_iFunctional expression, wherein radial dimension difference F_rCan be expressed as formula (8), circumferential size difference F_θCan be expressed as formula (9),

F_r=t_d(r_i)-t_w(r_i)+e_dr(r_i)+e_wr(r_i)=f_r(r_i) (8)

F_θ=e_{d θ}(r_i)+e_{w θ}(r_i)=f_θ(r_i) (9)

4) Die cavity profile is modified according to above-mentioned functional expression (8) and (9), if the parametric equation of the former contour line of mold cavity expression formula under cylindrical-coordinate system is

Wherein, g (t) contour line radial component, h (t) be contour line circumferential component, t be equation group parameter, then the Die cavity profile line parametric equation revised is expressed as formula (10),

$\left\{\begin{array}{c}r=g\left(t\right)+f_r\[g\left(t\right)\]\\ \mathrm{\θ}=h\left(t\right)-180f_{\mathrm{\θ}}\left(r_i\right)/{\mathrm{\πr}}_i\end{array}\right.---\left(10\right)$

Wherein radial component part g (t) brings Die cavity profile and forging surface profile radial dimension difference f into variable format_r(r_i), obtain correction term f of the Die cavity profile line parametric equation radial component revised_r[g(t)]；By 180/ π r_iIt is multiplied by f_θ(r_i) obtain correction term 180f of Die cavity profile line parametric equation circumferential component revised_θ(r_i)/πr_i；

5) according to step 4) the middle Die cavity profile line parametric equation processing mold revised.

The special-shaped disk-like accessory hot precision forging mold cavity modification method of the present invention it is further elaborated on below in conjunction with specific embodiment.

The part that the specific embodiment of the invention is forged is automatic gearbox of vehicles gear, and gear parameter is: modulus 2.7185, the number of teeth 26, pressure angle 20 °；Finish forge mould uses double-deck elastic conjunction form, as in figure 2 it is shown, mold cavity mean radius R₁=38.69mm, internal layer outer radius R₂=90mm, outer layer outer radius R₃=130mm, monolateral magnitude of interference 0.17mm, mold materials Young's modulus 198GPa, Poisson's ratio 0.3 between double stack mold；Room temperature 20 DEG C, mold preheating temperature 100 DEG C, forging temperature 1000 DEG C, mould and forging thermal coefficient of expansion 1.2 × 10^-5；Forging material at high temperature Young's modulus 50GPa, Poisson's ratio 0.43, flow stress 180MPa.

Four parts of Die cavity profile and the deformation of forging surface profile are mould pre-thermal expansion t_d, forging shrinkage t_w, mould stress elastic expansion e_d, resilience e after forging depanning_w。

Die cavity profile is calculated by formula (1)-(4), (6) with forging surface profile radial dimension difference, wherein t_dAnd t_wCan be tried to achieve by thermal expansion formula, calculating desired data is room temperature 20 DEG C, mold preheating temperature 100 DEG C, forging temperature 1000 DEG C and mould and forging thermal coefficient of expansion 1.2 × 10^-5；e_wrAnd e_drCan be tried to achieve by the lame formula of thick cyclinder stress deformation and generalized Hooke law, calculating desired data is mold cavity mean radius R₁=38.69mm, internal layer outer radius R₂=90mm, outer layer outer radius R₃Monolateral magnitude of interference 0.17mm, mold materials Young's modulus 198GPa, Poisson's ratio 0.3, forging material at high temperature Young's modulus 50GPa, Poisson's ratio 0.43 and flow stress 180MPa between=130mm, double stack mold.Calculating rolling circle to the higher involute part of tooth top required precision, result of calculation is as it is shown on figure 3, abscissa is r_i, i.e. the i distance away from gear centre (barycenter) in arbitrfary point on involute, vertical coordinate is radial dimension difference F_r.Result shows, total radial dimension difference F_rIt is 0.275mm to 0.322mm from basic circle to tooth top, and with r_iIncrease and be gradually increased.

Die cavity profile is calculated by formula (1), (5), (7) with forging surface profile circumferential size difference, wherein e_{w θ}And e_{d θ}Can be tried to achieve by generalized Hooke law, calculating desired data is module 2.7185, the number of teeth 26, pressure angle 20 °, mold materials Young's modulus 198GPa, Poisson's ratio 0.3, forging material at high temperature Young's modulus 50GPa, Poisson's ratio 0.43 and flow stress 180MPa.As shown in Figure 4, abscissa is r to result of calculation_i, i.e. the i distance away from gear centre (barycenter) in arbitrfary point on involute, vertical coordinate is circumferential size difference F_θ.Result shows, total circumferential size difference F_θFrom basic circle to tooth top be 6 μm to 3 μm, with r_iIncrease and non-linear reduction.

Die cavity profile and forging surface profile radial dimension difference result of calculation fit to formula (8), Die cavity profile and forging surface profile circumferential size difference result of calculation fit to formula (9), owing to standard involute equation is formula (11), therefore, in formula (10), g (t) isH (t) is in ω-arctan ω, formula (8) (9) (11) is brought into formula (10) and tries to achieve revised mould toothed wheel profile parametric equation, expression formula is formula (12), gear thermal finish forge mould is processed by this involute, and carry out gear thermal finish forge, forging is carried out on 10MN double disk friction screw press, and mold preheating temperature is 100 DEG C, and forging temperature is 1000 DEG C.Forging uses gear testing center prototype gear forging precision after terminating, and testing result as it is shown in figure 5, maximum error is 42.2 μm, reaches accuracy of gear national standard 10 grades, substantially increases gear thermal finish forge precision.

$\left\{\begin{array}{c}r=\frac{d_b}{2}\sqrt{1+{\mathrm{\ω}}^2}\\ \mathrm{\θ}=\mathrm{\ω}-\arctan \mathrm{\ω}\end{array}\right.---\left(11\right)$

$\left\{\begin{array}{c}r=\frac{d_b}{2}\sqrt{1+{\mathrm{\ω}}^2}+f_r\left(\frac{d_b}{2}\sqrt{1+{\mathrm{\ω}}^2}\right)\\ \mathrm{\θ}=\mathrm{\ω}-\arctan \mathrm{\ω}-\frac{f_{\mathrm{\θ}}\left(r_i\right)}{r_i}\frac{180}{\mathrm{\π}}\end{array}\right.---\left(12\right)$

Claims (4)

1. a special-shaped disk-like accessory hot precision forging mold cavity modification method, it is characterised in that: comprise the steps:

1) building based on forging and mould the mathematical model of profile deformation in hot precision forging process, mathematical model includes mould pre-thermal expansion t_d, forging shrinkage t_w, mould stress elastic expansion e_dAnd resilience e after forging depanning_w；And set mold cavity original dimension and be Die cavity profile size and forging surface profile difference in size F, i.e. F=e as r, mold cavity original dimension R with the difference of forging final size r as R, forging final size_d+t_d+e_w-t_w；

2) and take arbitrfary point i on forging surface profile on Die cavity profile, and arbitrfary point i is r to centroid distance_i, try to achieve on Die cavity profile and the deformation values of arbitrfary point i on forging surface profile, i.e. pre-thermal expansion radial deformation value t of arbitrfary point i on Die cavity profile_d=t_d(r_i), the shrinkage of arbitrfary point i radially deformation values t on forging surface profile_w=t_w(r_i), stress elastic expansion radial deformation value e of arbitrfary point i on Die cavity profile_dr=e_dr(r_i) and circumferential deformation value e_{d θ}=e_{d θ}(r_i), on forging surface profile, the resilience of arbitrfary point i expands radial deformation value e_wr=e_wr(r_i) and circumferential deformation value e_{w θ}=e_{w θ}(r_i)；

3) it is about variable r with arbitrfary point i deformation values on forging surface profile on Die cavity profile_iExpression formula, so Die cavity profile size and forging surface profile difference in size F are about variable r_iFunctional expression, wherein radial dimension difference F_r=t_d(r_i)-t_w(r_i)+e_dr(r_i)+e_wr(r_i)=f_r(r_i), circumferential size difference F_θ=e_{d θ}(r_i)+e_{w θ}(r_i)=f_θ(r_i)；

4) set the parametric equation of the former contour line of mold cavity under cylindrical-coordinate system expression formula as

Wherein, g (t) contour line radial component, h (t) be contour line circumferential component, t be equation group parameter, then the Die cavity profile line parametric equation expression formula revised is as follows:Wherein: radial component part g (t) brings Die cavity profile and forging surface profile radial dimension difference f into variable format_r(r_i), obtain correction term f of the Die cavity profile line parametric equation radial component revised_r[g(t)]；By 180/ π r_iIt is multiplied by f_θ(r_i) obtain correction term 180f of Die cavity profile line parametric equation circumferential component revised_θ(r_i)/πr_i；

5) according to step 4) the middle Die cavity profile line parametric equation processing mold revised.

The most special-shaped disk-like accessory hot precision forging mold cavity modification method, it is characterised in that: described step 1) in mould preheating expand t_dFor mold cavity before forging owing to mould preheating will occur thermal expansion the size that increases, mould stress elastic expansion e_dThe elastic expansion amount occurred under forging applies pressure for mold cavity, resilience e after forging depanning_wFor push rod by forging from mold ejection time forging's block dimension resilience swell increment, forging shrinkage t_wThe shrinkage amount occurred being cooled to room temperature from forging temperature for forging.

Special-shaped disk-like accessory hot precision forging mold cavity modification method the most according to claim 1 or claim 2, it is characterised in that: described mold cavity original dimension R+ mould pre-thermal expansion t_d+ mould stress elastic expansion e_d=deformation rear mold cavity dimension R ', forging final size is resilience e after r+ forging depanning_w-forging shrinkage t_wForging's block dimension r ' after=deformation, and R '=r '.

Special-shaped disk-like accessory hot precision forging mold cavity modification method the most according to claim 1 or claim 2, it is characterized in that: after described mould stress elastic expansion radial deformation and described forging depanning, the radial deformation of resilience can law and lame formula be expressed all in accordance with Generalized Hu, after described mould stress elastic expansion circumferential deformation and described forging depanning, the circumferential deformation of resilience can be expressed by law all in accordance with Generalized Hu.