Improvement of pickling process for hot-dip galvanized steel wire production line

The annealed steel wire and the non-annealed steel wire are classified and pickled to realize the full use of acid solution; the automatic control of the acidic solution is added according to the DV value; the stepped concentration pickling is used to collect the waste acid solution. By improving the utilization of hydrochloric acid, the consumption of hydrochloric acid produced by electro galvanized steel wire was reduced.

1. Steel wire pickling

Production statistics show that the proportion of high carbon steel wire production is positively correlated with acid consumption, the proportion of annealed steel wire production is positively correlated with acid consumption, and it is found that the amount of scale produced by annealed steel wire has a greater impact on pickling. Therefore, the production line is rearranged according to whether the steel wire is annealed or not. The guide wire was used to separate the annealed steel wire and the non-annealed steel wire into different pickling tanks. After a large number of process tests, the independent hydrochloric acid mass fractions were determined.

2. Accurate addition of pickling solution

The Dv value is an important parameter for the production control of hot dipped galvanized steel wire. The Dv value is determined according to the product of the speed and the corresponding diameter. The real-time wire speed of each steel wire is collected through a wire-over wheel with a rotary encoder. The rotary encoder uses Koyo TRD-2T1000BF, which is synchronized with the linear speed. Pass the information collected by the encoder to the PLC, and manually input the diameter of each wire through the HMI human-machine interface, calculate the Dv value of each wire, and then calculate the surface area of the multiple wires passing through the pickling tank in a unit time. Calculate the amount of scale required for pickling. Under the same heat treatment process, the tolerance range of the scale thickness δ on the surface of the steel wire is small and can also be regarded as a constant. Therefore, according to the real-time Dv value, the frequency of the acid pump drive can be adjusted to control the automatic addition of hydrochloric acid and Consumption synchronization, realizing closed-loop automatic control of acid addition.

3. Full utilization of acid solution and recovery of waste acid

Redesign the pipeline to add new hydrochloric acid to the annealed steel wire pickling tank; add a low-concentration acid tank to collect the overflow and discharged low-concentration hydrochloric acid from the annealed steel wire pickling tank; use the collected low-concentration hydrochloric acid for non-annealing Steel wire pickling tank; collect the waste hydrochloric acid overflowed and discharged from the non-annealed steel wire pickling tank, and wait for recycling by qualified enterprises.

The modified hydrochloric acid washing process mainly consists of an acid removal facility, a new acid storage tank, a waste acid collection tank, an acid addition tank, an acid addition control device, an acid addition pump, and related pipelines. It is unloaded from the tank truck to the new hydrochloric acid storage tank. Quick-release joints are used to remove the acid to prevent acid splashing and hurting people. The new hydrochloric acid storage tank is placed above the ground and the bottom is higher than the working liquid level of the pickling tank. The new hydrochloric acid flows to the annealing steel wire pickling system by means of a pressure difference.

4. Pickling process

Separate acid adding systems are set for the annealed steel wire and the non-annealed steel wire in the workshop. The acid adding tank of the soft black annealed steel wire is controlled by an acid corrosion-resistant floating ball valve, and the liquid level is maintained to meet the requirements. Of stock. The acid adding controller accurately adds hydrochloric acid to the heat-treated steel wire pickling tank according to the Dv value in real time.

The hydrochloric acid overflowing from the annealed steel wire pickling tank was collected into a low-concentration acid solution tank. The acid addition tank of the non-annealed steel wire is provided with a liquid level gauge for controlling the acid pump, and the hydrochloric acid in the low-concentration acid solution tank is used to supplement the acid addition tank of the non-annealed steel wire. Finally, the waste acid liquid overflowed and discharged from the non-annealed steel wire acid pickling tank is collected to the recovery tank, and the waste acid is recovered.