WCA January 2020

parameters in high temperature deformation, and solve the thermal physical properties of copper. The physical properties of bright hypoxic copper are shown in Table 2 . 3.2 Flow field simulation of temperature field in continuous casting Selection of process parameters: Casting temperature 1,120°C, casting speed 12.4m/min, casting angle 40°, wheel groove thickness 43mm. Numerical simulation based on the established mathematical mode, clouds of the temperature field and flow field in the crystallisation zone are shown in Figure 3 .

rod during continuous rolling can be described more accurately. The Johnson-Cook model is used to describe the deformation behaviour of copper rod under large deformation, high strain rate and high temperature rolling [6] .

⎤ ⎦ ⎥ 1 − ⎡ ⎣ ⎢ ⎢

⎤ ⎦ ⎥ ⎥

m

⎡ ⎣ ⎢

⎞ ⎠ ⎟⎟

⎛ ⎝ ⎜⎜

T − T r T M - T r

σ = A + B ε n ( ) 1 + CLn ! ε ! ε 0

❍ ❍ Equation 3

where σ , ε are flow stress and equivalent strain; , are strain rate and reference strain rate; A, B, C are yield strength at strain rate, power pre-exponential coefficient and strain rate sensitivity coefficient; m, n are temperature sensitivity coefficient and work hardening coefficient; and T, T r , T m are reference temperature and melting point of copper rod. Mises yield criterion is used to describe the deformation behaviour of copper rod under thermo-mechanical coupling with the help of the Lagrange deformation displacement formula. The stress-strain field and temperature field of deformation are regarded as independent systems [7] . ! ε ! ε 0

As shown in Figure 3(a) , different colours represent different temperature ranges. The temperature distribution of the temperature field can be observed by the length of colour block interval. The temperature gradient exists in different decreasing speeds of temperature. The casting temperature is 1,120°C and outlet temperature of the crystallisation zone is 1,031°C. It is in accordance with the temperature range of the exit position of the crystallisation zone measured in the production site, and shows that the simulation model is in line with the actual situation. Figure 3b , the flow field nephogram, conforms to the law of solidification and crystallisation of liquid copper in the mould. 3.3 Deformation simulation of copper rod in hot continuous rolling The field process data in Table 3 is collected and the numerical simulation model is established based on the theoretical mathematical model. The simulation results are shown in Figure 4 . In order to facilitate analysis and increase calculation speed, the hot strip mill is divided into four groups (1#+2#, 3#+4#+5#, 6#+7#+8#, 9#+10#). The stress, strain, temperature and damage of each pass of hot strip copper rod will be analysed, which will lay a foundation for studying the deformation law of hot strip copper rod during hot strip rolling. ❍ ❍ Figure 3 : Cloud maps of (a) temperature field and (b) flow field in crystallisation zone

⎧ ⎨ ⎪ ⎪

M T ( ) ∂ 2 U ∂ t 2

+ D T ( ) ∂ U

∂ t + K T ( ) U = F

C T ( ) ∂ T

⎩ ⎪ ⎪ ❍ ❍ Equation 4

∂ t + H T ( ) T = Q + ʹ Q

Through theoretical modelling and analysis of billet forming and deformation mechanism of hot continuous rolling copper rod in the continuous casting and rolling process, its technological principle was discussed, and this laid a foundation for numerical simulation. 3 Numerical simulation 3.1 Parameter selection Combined with the SCR3000 on-site process, simulation parameters are selected separately. The physical and chemical properties of copper determine its physical ❍ ❍ Table 2 : Physical performance parameters of low-oxygen copper bar

Liquidus temperature Friction coefficient

Density (kg/m 3 )

1,083°C

8,960

ν

0.45

0.326

❍ ❍ Table 3 : Technological parameters of SCR3000 continuous mill unit

1H

2V

3H

4V

5H

6V

7H

8V

9H 10V

3,800 2,500 1,320

800 480

480 300 6.00 1.00 6.29

300 195 7.65 1.00 4.05

195 125 3.60 1.00 2.83

125

95 65

65

/mm 2 /mm 2

A A

0

2,500 1,320

800

95

50.27

1

5.35 1.00 1.94

2.80 1.00 1.38

3.50 1.00 1.02

H /mm 11.50 18.75 10.30 12.40

5.80

1.00

1.00 9.82

G /mm 8.20

ƒ

71.69 36.27 15.72

v r /m·s -1 0.329 0.650 1.023 1.664 2.658 4.075 6.411 8.468 12.514 16.441

* A

0 – into rolling area, A 1

– out rolling area, H – pass depth, G – roll gap, f – total transmission ratio, v r

– roll circumferential velocity

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Wire & Cable ASIA – January/February 2020