EuroWire November 2019

Technical Article

n(r/ min)

Production speed 25.03 t/h Casting bar speed(m/s)

0.216

v(m/s)

16.349

1037

Motor speed(r/min)

Elongation coefficient

Roll speed(n)

Roll speed(v)

Frame D/mm Forward slip 1H 304.80 1.050

Theoretical

Actual

Theoretical

Actual

1496 1508 1510 1566 1525 1529 1630 1496 1542 1476

1533 1583 1560 1611 1578 1580 1681 1538

21.38 43.64 99.26

0.331 0.644 1.027 1.688 2.717 4.176 6.501 8.523

--

--

2V

304.80 1.055

1.899 1.620 1.650 1.600 1.539 1.560 1.315 1.462 1.293

1.945 1.594 1.643 1.610 1.537 1.557 1.311 1.417 1.234

3H 204.50 1.075

4V

204.50 1.094

164.00 251.03 390.32 594.83 792.38

5H 204.50 1.074

6V

204.50 1.080

7H 204.50 1.058

8V

204.50 1.060

9H 204.50 1.040 10V 204.50 1.047

1536 1114.66 12.073 1404 1376.47 14.903

*D – Diameter of roll body, n – Rotational speed of crystallisation wheel, v – Copper rod conveying speed ▲ ▲ Table 4 : Matching table for extension coefficient of stands of continuous rolling mill in SCR3000 production line

more intense flow will generate a vortex in the upper part of the crystallising region. 4.2 Deformation simulation analysis of copper rod rolled by hot continuous rolling The stress and strain of ten-stand copper rod during hot rolling were simulated and analysed. The deformation of roughly rolled copper rod mainly concentrates on the surface and the equivalent strain at the edge and corner is relatively large, which can easily cause processing damage. The equivalent strain of roll gap in an elliptical pass system of finishing copper rod is larger than that of roll contact in circular pass system. As rolling proceeds, the equivalent strain shifts from the surface to the centre of the copper rod. Temperature is the most important process parameter in the hot rolling process. Reasonable temperature control is the key to ensure the mechanical properties of products. Evolution of the temperature field during continuous rolling of copper rod was obtained by extracting temperature changes of rolling

The spray heat transfer coefficient increases with the increase of casting depth, and the heat transfer between the mould and the slab increases accordingly. The numerical simulation of temperature field and flow field with variable heat transfer coefficient and average heat transfer coefficient in spray heat transfer coefficient is studied. When the heat transfer coefficient changes along the crystal wheel, the upper part of the crystallisation zone has a darker colour, indicating that the temperature of the region is higher, while the colour of the exit part near the crystallisation zone is lighter, indicating that the temperature of the region is relatively low. When the heat transfer coefficient is average, the fluctuation of free liquid surface has little effect on the surface. When the heat transfer coefficient changes along the crystallising wheel, the flow of liquid copper from the nozzle into the cavity can not be fully expanded due to the geometrical structure of the cavity. When it impacts on the wall of the crystallising wheel, there will be a recirculation and the

crystallisation zone, and the vortex recirculation zone remained basically unchanged, but the recirculation velocity increased. At the same time, the viscosity of liquid copper decreases; the fluidity of liquid copper enhances the impact depth of the mainstream strand, which leads to gas and inclusions in-depth. This is not conducive to the removal of upward flotation and makes gas and impurities stay in the slab to form defects. The numerical simulation of heat-flow coupling in the mould cavity crystallisation zone was carried out with different casting speeds (11.4m/min, 12.4m/min, 13.4m/ min, 14.4m/min). With the increase in casting speed, the overall temperature of the crystallisation zone increases, the length of liquid phase zone increases, and the temperature at the outlet increases significantly. Because of the difference between the material of the crystal wheel and the steel strip and the air layer on the side of the crystal wheel, the minimum temperature on the side of the crystal wheel at the outlet side is always slightly higher than that on the side of the steel strip. With the increase of billet drawing speed, the impact depth of the main stream of copper melt increases, and the swirl recirculation region becomes narrow, extending to the direction of the crystallisation wheel rotation, and the recirculation velocity also increases. Increasing the casting speed will deepen the flow depth of bubbles and inclusions, and reduce the escape time of bubbles, which is not conducive to controlling the porosity and inclusion defects.

▼ ▼ Figure 5 : 2# Frame spraying device structural optimisation scheme

▲ ▲ (b) Structural optimisation of spraying device for 2# rack

▲ ▲ (a) 2# Frame spraying device and structural diagram

54

www.read-eurowire.com

November 2019