effects of heating temperatures on hot spinning of tals
TRANSCRIPT
Effects of Heating Temperatures on Hot Spinning of TAlS Alloy Thin-walled Shell
Mei Zhan, Tian Li, He Yang, Qiaoling Wang, Hu Li
State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University ,P. 0. Box 520 ,Xi' an 710072 ,China
Titanium alloy thin-walled shells, formed by hot spinning, have been attracting more and more applications in aerospace, aviation, military and
other technical industries, due to its highly forming precision and satisfyingly increasing needs for thin-walled and high strength/weight ratio
products. The hot spinning of titanium alloy thin-walled shells is a complex multi-physics problem with multi-factor coupling interactive effects,
and the heating temperatures have significant influences on the spinning qualities of workpieces. Therefore, in this study, using a 3D elastic-plas
tic finite element (FE) model for the hot spinning of TAI 5 alloy thin-walled shell. the influence laws of preheating temperature of mandrel and
heating temperature of blank on forming qualities are revealed. The results show that: preheating temperature of mandrel and heating tempera
ture of blank have significant influence on maximum tangential tensile stress. With the increasing of preheating temperature of mandrel and heat
ing temperature of blank, the tangential tensile stress first decreases then increases The reasonable preheating temperature and the heating tem
perature are about 400"C and 750"C , respectively. Finally, the satisfied workpieces are obtained with the above parameters. The results may pro
vide a theoretical guide for the determination and optimization of forming temperature of relative spinning process.
Keywords: Titanium alloy thin-walled shell .hot spinning ,coupled thennal-mecha11ical ,heating temperature, preheating temperature
1. Introduction
Due to the inherent advantages and flexibility of the process such as simple tooling and low forming loads, plus the rapid emerging trend in modern indus
tries towards near net shape manufacturing of thin sectioned lightweight parts, metal spinning has been attracting more attentions)). With the development of
aerospace, aviation, weapon and other high technology industries, metals with light weight and high strength under high temperature are being used widely. As one kind of lightweight alloys in the wide applications, TA15 alloy, for its fine thermal stability, weldability, high creep resistance and strength, is used to be vital candidate for components of aero-engine, which works at temperature above 500°C 2>. In order to reduce its de
form resistance and improve its plasticity, the TA15 alloy workpiece should be spun at elevated temperature.
According to the research on TA15 alloy, the flow stress decrease gradually with increasing temperature at given strain rate3>. The investigation by Hong Quan et al1>
indicated that when heated below 600°C, the plasticity of
TA15 is poor due to work-hardening, so a little larger deformation would lead to cracks. When heated above 600°C ,due to the obviously dynamic recovery and dynamic
recrystallization, the plasticity can be improved. Hence, the
heating temperature is a vital factor for hot spinning. The investigation by Xu Wenchen et al5> indicated that the optimum temperature of hot spinning of TA15 alloy is in the range of 600-700°C . The spinning temperature should
keep higher relatively to avoid crack when tube wall is a little thicker, and the temperature should be decreased to
control pileup of metal before the rollers when tube wall
becomes thinner.
The hot spinning of T Al 5 alloy thin-walled shells
is a complex multi-physics problem with multi-factor
coupling interactive effects. Due to the limitation of ex-
perimental study and theoretical analysis, FE method is becoming a very important tool for the research on the effects of parameters and forming quality of structural component6
"1 ll. Based on the FE software ABAQUS/
Explicit, Li Hu et aJ7>, Sun Linlin et al8> studied temper
ature, stress and strain distribution of the power spinning for titanium alloy thin-walled shell and Ni-Cr-WMo superalloy workpiece with curvilinear shape, respectively. External thermal sources were transformed to internal thermal sources by dividing the blank into several
annulations according to the feed rate of rollers and heating area. However, neither one analyzed the effect of
temperatures on hot spinning. By means of FE software Ansys/Ls-dyna, Li Qijun et al9> analyzed the stress
strain status of different areas at different step and causes of drawback occurring. But the temperature distribution was not analyzed. Shan Debin et al1°> used FEM to analyze the effect of roller path, flanged length and feed ratio on spinning. The temperature was assumed to be constant during spinning process. Chen Yu et al1 ll established a 3D rigid-plastic FEM simulation coupled ther
mal model for TC4 titanium alloy by warm shear spin
ning. The model can not be used to analyze springback due to the assumption of rigid-plasticity model.
In this paper, using FEM, temperature field distri
butions under different paths are obtained. And the in
fluencing laws of different heating temperatures of blank and preheating temperature of mandrel on the tangential tensile and compressive stress, and shear stress (along circumferential direction in tangential plane) are investigated. Then, optimum heating tem
perature and preheating temperature are obtained. With
the simulation results, satisfied workpiece is obtained
by experiment.
2. Finite Element Model and Computational Conditions
The FE model used in the study is the same as the
• 1784 • Proceedings of the 12'h World Conference on Titanium
model in the published paper by Li Hu et aln , as shown in Figure 1. Blank and mandrel are defined as 3D deformable solid bodies, rollers are defined as analytical rigid bodies, and spindle is defined as a discrete rigid body. Blank is partitioned into several annuluses in response to the heating area and feed rate of rollers. Body heat flux is applied to each annulus following the movement of roller. The model has been proved to be stable in reference7>.
The thermo-physical parameters of workpiece and mandrel are taken from reference12
•13>. The true stress
strain curve is taken from reference15>. The process pa
rameters of hot spinning are shown in Table 1.
Figure 1. FE model of hot spinning Cfor meshing) n
Table 1. Process parameters of hot spinning
Initial diameter of blank/ mm
Initial thickness of blank/ mm
Diameter o f roller/ mm
Nose radius of roller/ mm
Setting angle of roller/ degree
Larger diameter of mandrel/mm
Smaller diameter of mandrel/mm
H alf cone angle/ degree
Radius of corner of mandrel/ mm
Rotational speed of mandrel/ rad s- 1
Distance between roller and mandrel/ mm
Feed ratio of rolle r/ mm r- 1
Gap conductance (blank-mandrel) / W ( m2 "C) - i
Heat transfer coeffi cient
( blank-envi ronment) / W(m2 °C) - 1
Heat transfer coeffi cient
(mandrel-environment) / W(m2 "C ) - 1
Radiation coefficient of blank
Radiation coeffi cient of mandrel
Preheating temperatu re/ "C
H eating temperature/ "C
3. Results and Discussion
260
4
170
4
30
280
80
45
10
20.944
2.828
1450
16. 5
20
o. 6
0. 8
350,400,450
700 ,750 , 800
Two paths are established to analyze the temperature distribution in workpiece during spinning process, as shown in Figure 2. Path-1 is along the radial direction, while path-2 is along the circumferential direction.
Figure 3 shows the temperature distributions along different paths during spinning process. As seen from
Figure 3 a) , the temperature is about 750°C at the de-
Figure 2. Definitions of two paths
forming area. After being deformed, the temperature in the current area decreases sharply, and large temperature difference of deformed area can be seen from Figure 3(a) ,about 320°C . This is because of the long contact between mandrel and deformed area and low temperature of mandrel. There are much longer time for thermal conductance between mandrel and top of blank, which lead to the lowest temperature of blank on the top area, about 420°C. According to Figure 3 ( b), the tempera
ture distribution is nearly even along path-2.
800
700
~ 600 ~ 500
g 400 0.
~ 300 r 200 ....... _fo_n_n-in-g-ra--..tio_=_,2-5°,...Yo_,1
+ forming ratio=50% 1 OO ..... formi ng ratio=75%
0 '*forming ratio= I 00% .t::::c0=5:c::O::i':::ll O=O=l=r=5=0 =20:c:.0_2__,5_0~3_.._00~3 5._0_4__,0_0~4......J50 ( a) Path- I
True distance along path-I /mm
7QQ e • e 8 I •I I I I I I I I I I I I I I e I I
600 p ~ 500
~ 400 g_ E 300 ~
200
100
........ forming ratio=25% --+- forming ratio=50%
_..._forming ratio=75% _.... forming ratio= 100%
Lll::: ___ t:tt:! ___ !::lt::j1::t1::-::lt:!l~LJ ( b ) Path-I 0 I 00 200 300 400 500
True distance along path-2/mm
Figure 3. Temperature distributions at different time along
different paths
3. I Effects of Preheating Temperature of Mandrel As estimated above, heating temperatures have
the important effects on the forming quality and precision of deformed workpiece, so the corresponding influencing laws should be investigated3>. According to ref. is-m , cracks, bulge and warping defects are easy to
occur during hot spinning process. Tangential tensile stress can predict the tendency of cracks, while tangential compressive stress can predict the tendency of bulge, and shear stress can predict the degree of war
ping. Therefore, in this paper, these three factors are
taken into considerations.
7. ear Net Shape Processing • 1785 •
Figure 4 shows the influencing laws of preheating temperature of mandrel on maximum tangential compressive stress, tangential tensile stress and shear
stress. As seen from this Figure , with the increasing of preheating temperature, the maximum tangential compressive stress increases , and the tangential tensile stress first decreases then increases , but the shear stress is in the opposite tendency. When the preheating temperature increases , the temperature difference in thickness directions decreases , and the deformation of blank becomes more even and easier, thus the required tangential tensile stresses decreases , but tangential compressive
stress increases, and bulging is likely to occu r. At the same time , the shear stress increases, which means warping would be easy to occur. However, if the preheating temperature increases continually, above 400°C , the
maximum distance between inner surface of workpiece and mandrel would increases due to the expanded diameter, and the required deformation stress increases , thus the tensile stress increases. At the same time , the com
pressive stress increases a little due to the decreases of deform resistance with the increasing of temperature. Furthermore , the shear stress decreases because of the homogeneous temperature dist ribution.
800 -0- Shear stress 216
790 -+-Tangential 212 "' 780 tens il e stress "' 0...
208 ~ ~ 770 ~
~ 760 204 "' 750 ~
~ 200 ~
740 "' 5
OJ
Oll 730 196 65 = ~ 720 192
710 700 188
350 400 450
Preheating temperature/ ·c
Figure 4. Influencing laws of preh ating temperature of mandrel
According to the above analysis, prehea ting temperature has a great influence on the tangential tensi le
stress , lower or higher preheating temperature would
cause large tensile stress, and the optimum preheating
temperature of mandrel is about 400°C .
3. 2 Effects of Heating Temperature of Workpiece Figure 5 shows the influencing laws of heating
temperature of blank on maximum tangential tensile and compressive stress and shea r stress. According to
this Figure , with the increasing of hea ting tempera
ture , the compressive stress first increases then decreases , but the opposite tendency are with the tangential
tensile stress and shear stress. The reason is when
temperature increases , metal becomes soft and easy to
flow, and the tensile stress and shear stress decrease, at
the same time, bulge would arise in front of rollers, and
more compressive stress is needed for rollers to pass
through the workpiece, thus the compressive stress increases. With the temperature increases continually, due to the
dynamic crystallization and dynamic recovery, the plasticity of workpiece increases sharply, which makes it easier to be deformed, and the required compressive stress decreases. However, tangential tensile and shear stress increases due to the low hardness. The higher the temperature in a reasonable range, the easier metal can be deformed by hot spinning.
900 Shear stress 270
--+-- Tangentia l compressive 260
"' 850 -+- Tangential tensile stress 250 0...
240 cl:: ~ stress ~ 800 230 ~ ~ "' ;;; 220 ~ ~ 750 "' 210 ~
~ "' <I.I 00 200 ei ~ 700
190
650 180 750 800
Heating temperature/ ·c
Figure 5. Influencing laws of hea ting tempera ture of blank
According to the above analysis, heating temperature of workpiece has great influence on tangential tensile stress. The temperature should be appropriate, neither too
low nor too high, to avoid the larger tensile stress , and the optimum heating temperature is about 750°C
4. Experiment
With the heating temperature of the blank of nea rly 400°C and the prehea ting tempera ture of the mandrel of about 750°C, the experiments are carri ed out by PT30501 spinning machine (shown in Figure 6) , and
the satisfi ed workpiece is gained , as shown in Figure 7.
.. -
Figure 6. Power spinning machine CNC PT30501
Figure 7. Workpiece obtained by expe riment
5. Conclusions
In thi s study, using FEM and experimental methods, the influencing laws of heating tempera tures on
spinning are obtained, the results are as fo llows :
(1) The temperature distribution along the tangen
tial direction isn' t even , and the highest temperature
distributes nea r the contact areas of workpiece and roll-
• 1786 • Proceedings of the 12'h World Conference on Titanium
er. The temperature distribution along the circumferential direction is nearly even during spinning process.
( 2) The preheating temperature of mandrel and heating temperature of blank have significant influences on maximum tangential tensile stress. With the increasing of preheating temperature of mandrel and heating temperature of workpiece, the maximum tangential tensile stress first decreases then increases, and the reasonable preheating temperature and heating temperature are about 400°C and 750°C, respectively.
Acknowledgements This research 1s supported by the National High.
Technology Research and Development Program of China (No. 2008AA04Zl22), the National Natural Science Foundation of China (No. 50405039), and the authors wish to express their gratitude.
REFERENCES 1) C. C. Wong and T. A. Dean, J. Lin. International Journal of Ma
chine Tools & Manufacture. 2003;43,pp.1419-1435. 2) Li Xiong, Pang Kechang,Ji Bo,et al. Material for Mechanical En
gineering. 2007; 31 ( 7) : pp. 54-56 (in Chinese). 3) Liang Ye and Guo Hongzhen, Liu Ming, et al. Journal of Plastici
ty Engineering. 2008; 15 ( 4): pp. 150-154 (in Chinese).
4) Hong Quan and Zhang Zhenqi. Transaction of Aerial Materials. 2001;21(1),pp.10-12 (in Chinese).
5) Xu Wenchen and Shan Debin, Chen Yu, et al. Forging & Stamping Technology. 2008; 33(3): pp. 56-59 (in Chinese).
6) He Yang and Liang Huang, Mei Zhan. Computational Materials
Science. 2010;47: pp. 857-866. 7) Li Hu and Zhan Mei, Yang He, et al. Chinese Journal of Mechani
cal Engineering. 2008;44(6) :PP· 187-193 (in Chinese). 8) Sun Linlin and Kou Hongchao, Hu Rui,et al. Journal of Plasticity
Engineering. 2010; 17(2) :PP· 33-38 (in Chinese). 9) Li Qijun and Lv Hongjun, Wang Qi, et al. Journal of Tianjin Pol
ytechnic University. 2008;27(2),pp. 61-65 (in Chinese).
10) Shan Debin and Xu Wenchen, Zhou Xiang. Astronavigation manufacturing technology. 2010;(5),pp. 91-95 (in Chinese).
11 ) Chen Yu and Kang Dachang, Jin Xiaoou. Materials Science & Technology. 2006; 14(1): pp. 18-21 (in Chinese).
12) Chen Furong and Huo Lixing,Zhang Yufeng,et al. Transactions of the China Welding Institution. 2004; 25 ( 1): pp. 61-64 (in
Chinese). 13) Li Chunsheng and Huang Debin. Metallic materials manual.
(Chemical Industry Press,Beijing,2005). pp. 23-25 (in Chinese).
14) Xu Wenchen and Shan Debin, Li Chunfeng, et al. Journal of Aeronautical Materials. 2005;25(4),pp. I0-15 (in Chinese).
15) Xu Wenchen and Yang Guoping,Chen Yu, et al. Precise Sheet
Metal Forming Technology. 2007; (supplement): pp. 466-469 (in Chinese).
16) Xu Honglie. Power spinning technology. (National Defense Industry Press,Beijing,1983) pp. 169-178 (in Chinese).
17) Zhao Yunhao and Li Yanli. Spinning technology and applica
tions. (China Machine Press, Beijing, 2008) pp. 109-121 (in
Chinese).