JPS6033173B2 - Steel plate surface activity control device during continuous annealing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an activity control device for the surface of a steel plate in Rentsugi yakimei, which is used to produce a steel plate with excellent coating surface treatment properties such as phosphate chemical conversion treatment properties. Regarding.

Generally, cold-rolled steel sheets are subjected to phosphate chemical conversion treatment as a base treatment for painting.

Corrosion resistance after painting is largely determined by the quality of this base film. A high quality phosphate coating is one that is dense and has good adhesion. By the way, the phosphate precipitation reaction is an electrochemical phenomenon that depends on the properties of the steel plate surface, and from a microscopic perspective, it is a microcell in which Fe++ is generated at the local anode and second at the local cathode. It has been confirmed that a precipitation reaction occurs from the local cathode due to the formation of a so-called couple reaction.

In other words, the phosphate crystal nuclei first precipitate in the most inactive part, then in the most inactive part among the remaining parts, and so on, and their positions change sequentially, filling in the gaps until the phosphate crystal nuclei precipitate. , delicate phosphate crystal nuclei are precipitated all over the surface,
It continues to grow. However, phosphate crystal nuclei are difficult to precipitate in areas where the steel plate surface is active, and although a small number of phosphate crystal nuclei may precipitate in relatively inactive areas, the majority of phosphate crystal nuclei precipitate in inactive areas. It becomes covered with crystals. Such grown crystals are coarse and have weak adhesion to iron, resulting in poor corrosion resistance after coating. As is clear from these, in order to make the surface of a steel sheet excellent in phosphate chemical conversion treatment, it is necessary to form an appropriate active state, that is, an appropriate oxide film, which leads to the formation of microcells. It is an oxide film with a balanced characteristic of local anode and local cathode.

In Renzutsu annealing, the gas used in the protective atmosphere is generally N2 per day, which is the same as in all the old anchor operations, including tight coil Akatsuki, but for the purpose of Kouki lie inscription, the gas used in the protective atmosphere is mainly N2 per day. It is a weakly reducing gas.

The entire surface of the steel plate comes into contact with this weakly reducing gas while it is in the Rentsugi annealing furnace, so when it leaves the Rentsugi annealing furnace, there is almost no inert part on the surface of the steel plate. Almost the entire surface is a reduced surface, that is, an active part. In this regard, since the steel plates are in close contact with each other in tight coil Akatsuki, the oxide film on the surface of the steel plate from the previous process tends to remain as it is, and the moisture that adheres to the surface of the steel plate and is brought in during annealing. An extremely thick oxide film is formed on the surface of the steel sheet, thereby ensuring an inert area on the surface of the steel sheet that is favorable for the generation of dense phosphate crystal nuclei. In contrast, it can be said that the Renzutsu-yaki Kintun steel plate has an unfavorable steel plate surface condition. As mentioned above, phosphate crystal nuclei are not sufficiently precipitated on the surface of the steel sheet in an active state, and the few phosphate crystal nuclei form into coarse crystals, resulting in poor corrosion resistance after painting. .

Furthermore, even if the material undergoes a certain oxidation reaction in a lotus continuation annealing equipped with a direct-fired non-oxidizing heating furnace, it will exhibit an active surface due to the reduction reaction during the soaking, over-aging, and cooling processes. As described above, the entire surface of the continuous annealing steel sheet is in an active state, and the phosphate chemical conversion treatment is disadvantageous.

On the other hand, as the demand for paint corrosion resistance is increasing in the future for automobile exterior panels, etc., it is necessary to manufacture steel sheets with excellent phosphate chemical conversion treatment properties, and it is necessary to manufacture steel sheets with excellent phosphate chemical conversion treatment properties. It is necessary to develop a device that can control this.

In view of the above circumstances, the present invention provides a device for controlling the activity of a steel plate surface in a Rentsugi hammer, and its gist is to provide a fog point in a conduit pipe connecting a cooling zone and a quench tank in a Rentsugu refining furnace. a fog point detector that detects the temperature of the steel strip sent to the conductive pipe, a thermometer that detects the temperature of the steel strip sent to the conduction pipe, and a fog point detector that detects the temperature of the steel strip that is sent to the conductive pipe; A lotus-continuous annealing device comprising a fog point control recorder that outputs a control signal for controlling the amount of water vapor discharged so as to compare it with a target fog point value to be set and eliminate the deviation, and a device for discharging water vapor from the conduction pipe in accordance with the control signal for the amount of water vapor discharged. This is an activity control device for the surface of a steel plate.

According to the present invention, the flow rate of water vapor discharged to the outside can be controlled to control the amount of water vapor in the conduction pipe to a target value, and a steel plate surface with appropriate activity can be obtained by oxidation reaction.

In Rentsugi annealing, as a conventional control device to form an oxide film on the surface of the steel sheet, water vapor is brought in from the outside into the reducing atmosphere gas before being supplied into the furnace, and mixed to create a moderately weakly oxidizing atmosphere gas. There is a device that draws steam into the furnace on the outlet side of the Rentsugi sintering furnace, but the device of the present invention does not require such an external steam source, mixing control device, heat insulation equipment, etc. This is a very effective device that uses the steam generated by

Hereinafter, the present invention will be explained in detail based on the drawings.

The drawings are explanatory diagrams showing embodiments of the present invention.

When the steel strip 1 that has passed through the cooling zone 2 is cooled by the spray header 4 and the quench tank 5, a large amount of water vapor is generated. This water vapor tries to rise through the conduction pipe 3, but immediately after its generation, a part of it is forcibly discharged outside the pipe, and the remaining water vapor rises inside the conduction pipe 3 and comes out from the cooling zone 2. The steel strip 1 is brought into contact with the steel strip 1 to cause an oxidation reaction, thereby forming an oxide film with a target thickness. The oxidation reaction at this time is carried out as follows. 3/Misaki e Toka 2011/Misaki e
304 10th 2 is e304 10th 201 is e203 10th 2 The forced discharge of water vapor is performed by a discharge device such as a blower 6 through an outlet 7, a discharge pipe 8, and an eliminator 11.

The outlet 7 is installed directly above the quench tank 5 and the spray header 4, which are water vapor sources, and is connected to an eliminator 11.
is for converting water vapor into water droplets and removing them. A fog point detector 14 provided in the conduction tube determines whether the amount of water vapor rising through the conduction tube 3, which forms an oxide film on the steel plate, is the target amount of steam. Since the target amount of water vapor varies depending on the temperature of the steel strip, the temperature of the steel strip is detected by the thermometer 17, and the dew point target value DPs of the fog point recording controller 16 is set manually or automatically if an automatic circuit is installed. Make corrections to the settings. The pump 15 samples the atmospheric gas in the conduction pipe so that it passes through the fog point detector 14. The fog point is a measure of the amount of water vapor in the atmospheric gas by the temperature at which it condenses.The principle of detection is generally that the atmospheric gas is sucked into a pot containing a bobbin to which a moisture absorbent is attached, and the moisture is absorbed by the moisture absorbent. This is done by measuring the electrical conductivity of a bobbin that has absorbed moisture, or by measuring the temperature inside the bath due to changes in electrical conductivity using a resistor. The position of the fog point detector 14 is such that the temperature of the steel strip 1 is the highest;
The most preferable location is immediately after leaving the cooling zone 2, where the oxidation reaction is likely to be promoted, that is, at the top of the conduit tube 3. The output signal from fog point detector 14 is sent to fog point recording controller 16. The dew point recording controller 16 records the fog point detection value and compares it with a fog point target value DPs set in advance according to the temperature, outputs a discharge water vapor amount control signal to eliminate the deviation, and adjusts the discharge steam flow rate. Control valve 9. By controlling the flow rate of the discharged water vapor, the amount of water vapor remaining in the conductive pipe 3 and rising is maintained at the fog point, which is the target value. The exhaust water vapor flow rate is measured through the orifice 10 and the differential pressure transmitter 12, and the signal is sent to the exhaust gas flow rate recording controller 13.
recorded. The discharge steam flow rate adjustment is as shown in Figure 1.
Directly based on the deviation correction command from the fog point recording controller 16,
The exhaust steam flow rate control valve 9 is opened and closed, and as shown in FIG. There are two methods: a two-stage control method in which the flow rate set value Qso is corrected and the discharge steam flow rate control valve is opened and closed so that the discharge steam flow rate becomes the corrected set value Qs, that is, a cascade control method. However, either one may be adopted depending on the actual situation. As stated above, by using the steel sheet surface activity control device of the present invention, a large amount of oxide film is formed on the surface of the steel strip coming out of the furnace part of the Rentsugi sintering anchor equipment in the conduit to the quench tank. It is possible to obtain a steel plate having a moderately active surface.

The thus obtained steel plate has a good balance between the local anode and the local cathode on the surface, and has excellent phosphate chemical conversion treatment properties and corrosion resistance after painting. still,
The present invention is effective not only for rolling steel sheets intended for painting, but also for turn plating and galvanizing.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of the invention, and FIG. 2 is an explanatory diagram showing another embodiment of the invention. 1... Steel strip, 2... Cooling zone, 3...
... Conduction pipe, 4 ... Spray header, 5 ... Quench tank, 6 ... Blower, 7 ... Outlet port, 8 ... Discharge pipe, 9 ... Exhaust steam flow rate control valve, 10...
Orifice, 11... Eliminator, 12...
... Differential pressure transmitter, 13 ... Exhaust steam flow rate recording controller, 14 ... Fog point detector, 15 ...
...Pump, 16...Fog point recording controller, 17...
···thermometer. Tano diagram Figure 2

Claims (1)

[Claims] 1. A dew point detector that detects the dew point in the conduit pipe that connects the cooling zone of the continuous annealing furnace and the quench tank, a thermometer that detects the temperature of the steel strip sent to the conduit pipe, and dew point detection from the dew point detector. a dew point control recorder that compares the value with a dew point target value set in advance according to the steel strip temperature from the thermometer and outputs a discharge water vapor amount control signal to eliminate the deviation; A device for controlling the activity of a steel plate surface during continuous annealing, consisting of a discharge device for discharging water vapor from a conduction pipe.