Description：Aiming at the common problem of copper tube blackening in the mold of continuous casting machine, the influencing factors of copper tube blackening caused by the cooling water system of the mold were analyzed, and a solution to the problem was put forward in a targeted manner. The service life of the copper pipe is improved, and the quality of the billet product is also improved.
Keyword:Billet continuous casting; Mold copper tube; Blackened copper tube
Foreword
The high-temperature molten steel of about 1500 ℃ produced by steelmaking and smelting needs to be rapidly cooled by the continuous casting machine to form a billet. The mold is a key component in the continuous casting equipment and is called the heart of the continuous casting machine. The key equipment of the billet is the copper tube of the mold of the continuous casting machine. The heat transfer effect of the copper tube directly affects the quality of the billet product. Affected by various factors such as copper pipes, it is easy to appear blackening and scaling on the surface. Blackening and scaling of copper tubes will inevitably affect the heat transfer effect and affect the quality of cast billet products. By analyzing and eliminating the reasons for the blackening and scaling of the copper tubes of the crystallizer, the causes of the blackening and scaling of the copper tubes of the crystallizer are analyzed and found in practice, and measures are taken to control and slow down the blackening and scaling of the copper tube surface, so as to Meet billet cooling requirements.
Brief Introduction of Mold Copper Tube Cooling Water System (h2)
Huaigang Company has a total of 6 billet continuous casting machines. The billet section is mainly 150×150 and 200×200. The molds of the 6 continuous casting machines are cooled by open circulation of demineralized water. The water process is basically the same, that is, the pressure of qualified cooling water can reach 1.2~1.3 MPa through the water pump, and the water flow rate is different according to the flow number of the casting machine. After that, it is sent to the continuous casting machine distributor and distributed to the crystallizer copper tubes of each flow. After the cooling water passes through the copper tubes for heat exchange, the high-temperature return water enters the cooling tower to cool down with the residual pressure, and then returns to the pool. There is an automatic dosing system and a water quality testing and sampling device near the pool. The pool is equipped with a lift pump for closed-circuit cleaning and filtration, and the treated water passes through the pump again for cooling and recycling of the crystallizer. Among them, the circulating water volume of the 1# billet casting machine system is 1300m3/h, the retained water volume is about 800 m3, the water gap width of the mold copper pipe is 4 mm, the copper pipe outlet water flow rate is 127~135 m3/h, and the cooling water flow rate is 11.6~12.3 m/s , the copper pipe cooling water inlet temperature is less than 34 ℃, the water outlet temperature is 43 ℃, the number of heterotrophic bacteria in the system circulating water is controlled at less than 5×104/mL, and the indicators are strictly controlled within the standard range during the operation of the water system. Table 1 is Operational control index of copper pipe water system of 6 sets of continuous casting machines.
Table 1 Operation indicators of water quality data in soft water system
| system name | pH | Turbidity/(mg/L) | Hardness/(mg/L) | Total alkali(mg/L) | Cl-/(mg/l) | Total iron/(mg/L) | Conduc ivity/(uS/cm) | oil content/(mg/L) |
| Softened water requirement index | 7~9 | ≤10 | <20 | <300 | <150 | <1.0 | <1000 | 0 |
| Supplemental Water Requirement Index | 7~9 | ≤10 | <3 | <200 | <150 | <1.0 | <300 | 0 |
| Actual index of softened water | 8.61 | 5.37 | 6.5 | 216 | 92 | 0.65 | 853 | 0 |