Improvement and optimization of gating system for metal mold casting balls molding line (1)
(Hunan Hongyu Wear-resistant New Materials Co., Ltd., Changsha, Hunan 410600)
Abstract: The company’s original metal mold casting balls molding line using 1.2tons of medium-frequency induction furnace, the adoption of manual hydraulic control pouring to metal mold, often cast off, pouring dissatisfaction, overflow mold situation, based on the analysis of the pouring situation, the quantitative pouring was realized by controlling the pouring speed in stages, and the qualified rate of ball production was greatly improved.
Key words: Medium frequency furnace; pouring speed; pass rate; casting balls molding line
Chinese Picture Classification: TF775; Document symbol: A; Article number: 2095-2945(2017)22-0058-02
My Company’s original metal mold casting balls molding line to take manual control of hot metal pouring, but in the actual application process, often appear cut-off, pouring dissatisfaction, overflow mold situation, especially, the production line needs to be stopped and overhauled due to the overflow of Molten Iron Mould, which results in low qualified rate and high production cost.
2. Automatic pouring requirements for casting balls molding line
Our company uses medium frequency furnace equipment for metal smelting, pouring mouth using funnel form. The weight of each casting steel mould varies from 10KG to 50KG. When pouring a specification, the pouring amount is basically the same, each pouring cylinder stops at its original position, and the next time, when pouring again starts from here. The weight of the Molten Iron is about 1.2 tons, the longest pouring time is 50 minutes, each pouring period is about 25s, the time of each pouring is different for different models, but the pouring period should be controlled within 25s.
There are three control modes for pouring action
1) using the real-time weighing continuous signal of the electronic scale, detecting the increment, controlling the stop time of each pouring according to the increment, and starting the next pouring again after stopping;
2) the pouring time can be controlled by calculating the time needed for each pouring, and the stop delay can be adjusted on the control panel. Theoretical time and delay time can be optimized after field test and can be adjusted by manual input. There are corresponding control time curves for different models.
3) manual control, manual observation pouring situation, stop and start in progress, pouring finished to restore the original position.
3.Existing problems and improvement scheme of gating system in original casting balls molding line
3.1 The original pouring system has problem
When the medium frequency holding furnace is dumped at different angles, the molten iron flows out at different speeds. In fact, in the process of artificial operation, the operator operates according to his personal experience, often because of the short pouring time; in view of this problem, it is difficult to control the amount of molten iron pouring each time accurately, and it is too early or too late to control the pouring of medium frequency furnace, which leads to the situation of Molten iron running out, pouring dissatisfaction and overflow of the mould, we simulate and analyze the relationship between the quality of molten iron needed for each mould, the speed of Molten Iron pouring out when the holding furnace is dumped at different angles and the time needed.
3.2 Plan improvement
In this paper, the amount of molten iron poured from medium frequency holding furnace at different tilt angles is calculated, the molten iron velocity at different tilt angles is calculated, and the peak deviation of pouring velocity at different tilt angles is up to 20kg/s. Therefore, different pouring formulas are applied in different stages and angles, taking the production of 130mm cast steel ball as an example, eight different pouring formulas are adopted in different stages.
Each pouring formula consists of ten parameters:
- pouring quantity (the amount of molten iron required to fill a mould;
- rapid pouring (amount of molten iron to be poured in 2-3 seconds) ;
- slow pouring (amount of molten iron to be poured in 6-8 seconds) ;
- the amount of lead (the amount of molten iron remaining in the air during the final pouring process) ;
- Upper limit of rapid pouring flow (maximum speed at which rapid pouring can be achieved) ;
- lower limit of rapid pouring flow (minimum speed at which rapid pouring can be achieved) ;
- Upper limit of slow pouring flow (maximum speed at which slow burning is achieved) ;
- lower limit of slow flow (minimum speed at which slow flow can be achieved) ;
- casting period (the time required to fill a steel mold).
The pouring amount is the sum of the rapid pouring amount, the slow pouring amount and the advance amount.
To better calculate the amount of molten iron and the amount of molten iron that has been poured into the metal mould when the intermediate frequency holding furnace is tilting at different angles, a new angle sensor is added to the shaft of the Intermediate Frequency Furnace, and a weight sensor is added to the bottom of the metal mould which needs to be poured under the intermediate frequency furnace