WO2023000525A1 - Hot-rolled stainless steel annealing pickling process and pickling device - Google Patents

Abstract

A hot-rolled stainless steel annealing pickling process and pickling device. In the pickling process, by controlling the temperature of strip steel at an outlet of an annealing furnace, the high-temperature strip steel is in direct contact with a low-temperature pickling solution, such that a strong physical and chemical reaction occurs on the surface of the high-temperature strip steel to quickly pickle and strip a thick oxide scale on the surface layer; and by regulating and controlling redox characteristics of the pickling solution in a cascade overflow continuous pickling system, the pickling efficiency is improved, thereby efficiently removing residual austenite and ferrite oxide scales on stainless steel. The process makes full use of the residual temperature of the annealing furnace (4), reduces the temperature of an acid liquor, saves the energy consumption, and achieves the purpose of low-consumption and high-efficiency pickling of hot-rolled stainless steel strips.

Description

A hot-rolled stainless steel annealing and pickling process and pickling equipment technical field

The invention relates to the technical field of steel strip surface cleaning, in particular to a hot-rolled stainless steel annealing pickling process and pickling equipment.

Background technique

The surface quality of stainless steel is one of the key factors affecting the improvement of product performance. The hot-rolled austenitic and some ferritic stainless steels are generally carried out in a horizontal annealing furnace. The strip steel is preheated in the furnace by using the waste heat of the flue gas and then enters the heating section. When the temperature of the strip reaches 1180°C, water is used for rapid cooling to achieve solid solution, which reduces the yield strength of the strip and facilitates subsequent hot rolling. Since a large amount of scale is formed on the surface of the strip during the hot rolling and annealing process, in order to reduce the subsequent pickling consumption, the existing technology usually adds a scale breaking machine and a shot blasting machine to clean the surface of the strip before pickling. Iron oxide scale is processed. The pickling process adopts the combination of sulfuric acid and mixed acid, and the acid tank adopts a shallow tank design to form a turbulent flow effect and improve the pickling effect.

In view of the current situation that surface scale treatment is difficult, mechanical treatment processes such as scale breaking and shot blasting have become standard equipment for pickling units. The mechanical treatment process can remove the coarse iron oxide scale on the surface. However, it has significant disadvantages such as high investment cost, large floor space, high energy consumption for operation, large amount of maintenance, and large environmental pollution. Pickling conditions are relatively harsh, and pickling takes a long time. Therefore, it is urgent to develop high-efficiency pickling equipment and processes to slow down the pollution of high-temperature and high-concentration chemical reagents to the environment, speed up cleaning and obtain strips with high surface quality.

Contents of the invention

The invention aims to provide a low-consumption and high-efficiency hot-rolled stainless steel annealing and pickling process.

The specific plan is as follows:

A hot-rolled stainless steel annealing and pickling process, comprising the following steps:

Step 1), after the hot-rolled stainless steel enters the annealing furnace to regulate the composition, by adjusting the cooling capacity of the annealing furnace cooling section, the temperature of the hot-rolled stainless steel strip at the outlet of the annealing furnace cooling section is controlled to be 60 to 200°C;

Step 2), the hot-rolled stainless steel strip output from the outlet of the cooling section of the annealing furnace directly enters the cascade overflow continuous pickling system formed by a plurality of sub-troughs connected in series for pickling after being regulated by heat preservation, wherein The cascade overflow continuous pickling system includes a pre-pickling tank located in the front section and a multi-stage low-temperature pickling tank located in the rear section of the pre-pickling tank; the pickling medium of the pre-pickling tank is HCl, and the concentration of HCl is 20-60g/ L, while the pickling medium contains Fe ²⁺ and Fe ³⁺ ; the pickling medium of the low-temperature pickling tank is HCl, the concentration of HCl is 20-150g/L, and the pickling solution contains Fe ²⁺ and Fe ³⁺ ;

Step 3) The hot-rolled stainless steel strip after being pickled by the cascade overflow continuous pickling system enters the multi-stage rinsing system for rinsing and then drying and coiling.

Further, in step 2), the temperature of the hot-rolled stainless steel strip entering the pre-pickling tank is higher than 100°C.

Further, in step 2), the method of online dosing of multi-component weak acid and circulating filtration and separation is used to control the total iron content of Fe ²⁺ and Fe ³⁺ in the cascade overflow continuous pickling system.

Further, the concentration of acid solution in each sub-tank of the cascade overflow continuous pickling system increases sequentially, and the total iron content decreases sequentially.

Further, the cascaded overflow continuous pickling system in step 2) has at least two stages of low-temperature pickling tanks, wherein the pickling medium in the first stage is a reducing system, and the pickling medium in the last stage is a strong oxidizing system.

Further, in step 2), the ratio of Fe ²⁺ and Fe ³⁺ is regulated by adding an oxidizing agent, so as to control the oxidation-reduction characteristics of the pickling solution.

Further, the multi-stage rinsing system in step 3) is composed of 3-6 cascaded overflow rinsing systems, wherein the pressure of the last stage of rinsing water is 5-10 kg, and the pressure of the remaining stages of rinsing water is 2-6 kg.

Further, in step 1), the temperature of the hot-rolled stainless steel strip coming out of the cooling section of the annealing furnace is controlled by means of temperature control in the heat preservation chamber.

The present invention also provides a hot-rolled stainless steel annealing and pickling equipment, including a strip steel transmission device and an uncoiler, a welding machine, a looper, an annealing furnace, a heat preservation chamber, a temperature control device, Cascade overflow continuous pickling system, rinse tank and dryer.

Further, it also includes a control system and oxidation potential detection, the control system is connected with each acid tank of the cascade overflow continuous pickling tank, and the oxidation-reduction characteristics of the pickling medium in the cascade overflow continuous pickling tank and the dosage The automatic valve chain setting of the oxidant, the oxidation potential detection determines the oxidation-reduction characteristics of the pickling medium by detecting the oxidation-reduction potential of the acid solution in the continuous pickling tank with cascade overflow, and uses this to control the regulation system to continuously pickle the cascade overflow The oxidant is added to the pickling tank corresponding to the tank.

Compared with the prior art, the hot-rolled stainless steel annealing and pickling process provided by the invention has the following advantages: the hot-rolled stainless steel annealing and pickling process provided by the invention cancels the mechanical descaling process at the annealing furnace outlet, and adopts nitric acid-free, hydrogen-free The cascade overflow continuous pickling process system of hydrofluoric acid realizes the rapid cleaning of the steel strip, and at the same time controls the temperature of the strip steel at the exit of the annealing furnace, so that the high-temperature strip steel directly contacts with the low-temperature pickling solution, so that strong corrosion occurs on the surface Physical and chemical reactions, quick pickling to peel off the coarse iron oxide scale on the surface, and improve the pickling efficiency by adjusting the oxidation-reduction characteristics of the pickling solution in the cascade overflow continuous pickling system, so as to efficiently remove the residual austenite and iron on the stainless steel Plain body oxide scale, this process makes full use of the residual temperature of the annealing furnace, reduces the temperature of the acid solution, saves energy consumption, and realizes the purpose of low-consumption and high-efficiency pickling of hot-rolled stainless steel strip.

Description of drawings

Figure 1 shows a schematic diagram of annealing and pickling equipment for hot-rolled stainless steel.

detailed description

To further illustrate the various embodiments, the present invention is provided with accompanying drawings. These drawings are a part of the disclosure of the present invention, which are mainly used to illustrate the embodiments, and can be combined with related descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, those skilled in the art should understand other possible implementation modes and advantages of the present invention. Components in the figures are not drawn to scale, and similar component symbols are generally used to denote similar components.

The present invention will be further described in conjunction with the accompanying drawings and specific embodiments.

Example 1

The invention provides a hot-rolled stainless steel annealing and pickling process. The pickling process allows the high-temperature strip to directly enter the pickling tank for pickling by controlling the temperature of the strip steel at the exit of the annealing furnace or the heating at the entrance, and cancels the mechanical process at the exit of the annealing furnace. Descaling process, and through the nitric acid-free, hydrofluoric acid-free cascade overflow continuous pickling process system to achieve rapid cleaning of the strip, while reducing energy consumption and acid consumption, in order to obtain high surface quality strip steel, specifically including the following step:

Step 1), after the hot-rolled stainless steel enters the annealing furnace to adjust the composition, the temperature of the hot-rolled stainless steel strip at the exit of the cooling section of the annealing furnace is controlled to be 60-200° C. by adjusting the cooling capacity of the cooling section of the annealing furnace. In this embodiment, the hot-rolled stainless steel strip coming out of the cooling section of the annealing furnace realizes the control of the temperature of the hot-rolled stainless steel strip entering the tank by means of temperature control in the heat preservation chamber, so that the hot-rolled stainless steel strip enters the tank at a high temperature. Pickling in the pre-pickling tank.

Step 2), the hot-rolled stainless steel strip directly enters the cascade overflow continuous pickling system formed by multiple sub-troughs in series at high temperature after passing through the heat preservation chamber for pickling, wherein the cascade overflow continuous pickling system includes the The pre-pickling tank and the multi-stage low-temperature pickling tank located in the back section of the pre-pickling tank, the pre-pickling tank has a large cone-bottom structure, the pickling medium of the pre-pickling tank is HCl, and the concentration of HCl is 20-60g/L. At the same time, the pickling medium contains Fe ²⁺ and Fe ³⁺ . When the high-temperature hot-rolled stainless steel strip is in contact with the low-temperature pickling solution, a strong physical and chemical reaction can occur on the surface to quickly pickle and peel off the coarse iron oxide scale on the surface. Preferably, the temperature of the hot-rolled stainless steel strip entering the tank is higher than 100°C, so that when the hot-rolled stainless steel strip contacts the pickling solution, a strong physical and chemical reaction can occur on the surface to quickly pickle and peel off the coarse iron oxide scale on the surface.

The pickling medium of the low-temperature pickling tank is HCl, the concentration of HCl is 20-150g/L, and the pickling liquid contains Fe ²⁺ and Fe ³⁺ .

In the present embodiment, step 2) adopts online dosing polybasic weak acid, the mode of circulating filtration separation to regulate and control Fe ²⁺ and Fe ³⁺ total iron content in the cascade overflow continuous pickling system; Adjust the ratio of Fe ²⁺ and Fe ³⁺ to control the redox characteristics of the pickling solution to ensure the effect of pickling.

In this embodiment, the sub-tanks of the cascade overflow continuous pickling system realize cascade overflow through connecting pipes, the concentration of the acid solution increases sequentially, and the total iron content decreases sequentially.

Preferably, the multi-stage low-temperature pickling tanks in the cascade overflow continuous pickling system are 2-4 stages of low-temperature pickling tanks, and the oxidizing properties of the pickling medium gradually increase, and it is more preferable that the pickling medium in the second stage is reduced Strong oxidizing system, the last pickling medium is a strong oxidizing system.

Step 3) The hot-rolled stainless steel strip after being pickled by the cascade overflow continuous pickling system enters the multi-stage rinsing system for rinsing and then drying and coiling.

The multi-stage rinsing system is composed of 3-6 cascade overflow rinsing systems, and the pH meter and conductivity are set to monitor the rinsing liquid. The pressure of the first few stages of rinsing water is 2-6 kg, and the pressure of the last stage of rinsing water is 5-10 kg, thus achieving a better rinsing effect.

The hot-rolled stainless steel annealing and pickling process provided in this example cancels the mechanical descaling process at the exit of the annealing furnace, and adopts a nitric acid-free, hydrofluoric acid-free cascade overflow continuous pickling process system to realize rapid cleaning of the strip. Control the temperature of the steel strip at the exit of the annealing furnace, so that the high-temperature steel strip is in direct contact with the low-temperature pickling solution, allowing it to undergo a strong physical and chemical reaction on the surface, quickly pickling and peeling off the coarse iron scale on the surface, and controlling the cascade overflow The oxidation-reduction characteristics of the pickling solution in the continuous pickling system are used to improve the pickling efficiency and efficiently remove the residual austenite and ferrite oxide scales on the stainless steel. This process makes full use of the residual temperature of the annealing furnace and reduces the acid The liquid temperature is lowered, energy consumption is saved, and the purpose of low-consumption and high-efficiency pickling of hot-rolled stainless steel strip is realized.

Example 2

With reference to Fig. 1, it is a kind of pickling equipment that is used to realize the hot-rolled stainless steel annealing pickling process of above-mentioned embodiment 1, comprises strip steel conveying device (not shown in the figure) and along the travel direction of strip steel 22 sequentially Set uncoiler 1, welding machine 2, looper 3, annealing furnace 4, heat preservation chamber 5, temperature control device, pre-cleaning tank 9, 1# acid tank 11, 2# acid tank 15, 3# acid tank 17, rinse tank 19 and dryer 21.

Among them, the temperature control device is provided with a fan 6 and a heater 7, and the temperature of the strip steel can be regulated by controlling the power of the fan 6 and the heater 7, and a plate temperature instrument 8 is also installed on the temperature control device for detection and regulation. Strip temperature; pre-cleaning tank 10 is connected with pre-cleaning tank 9, 1# acid tank 12 is connected with 1# acid tank 11 through circulation pump 14, 2# acid tank 16 is connected with 2# acid tank through circulation pump 14 15, the 3# acid tank 18 is connected with the 3# acid tank 17 through the circulation pump 14, and the rinse tank 20 is connected with the rinse tank 19 through the circulation pump. It should be explained here that although only three acid tanks of 1 # acid tank 11, 2 # acid tank 15, and 3# acid tank 17 are shown in Fig. The number of pickling segments is increased or decreased. A heat exchanger 13 is also arranged between each acid tank and the acid tank to ensure that the pickling solution in the acid tank can maintain a low temperature after pickling.

The strip steel 22 is uncoiled through the uncoiler 1, and is transported by the transmission device to the direction of the subsequent process after being operated by the welding machine 2 and the looper 3. It first passes through the annealing furnace 4 for heat treatment, and after the heat treatment is completed, it is cooled from the annealing furnace 4 The strip output from the cooling section of the annealing furnace passes through the annealing furnace to adjust the circulation of the water jacket and control the temperature of the heat preservation chamber 5 to maximize the use of the residual temperature of the annealing furnace to keep the strip steel at a certain high temperature, and through the control After the temperature device is adjusted, a strong physical and chemical reaction can occur on the contact surface between the high-temperature strip steel and the low-temperature pickling solution to quickly pickle and peel off the coarse iron oxide scale on the surface.

The hot high-temperature steel strip enters into the rinsing tank 19 and the dryer 21 for rinsing and air-drying after passing through the pickling of the pre-cleaning tank 9, 1 # acid tank 11, 2 # acid tank 15, and 3# acid tank 17 in sequence. High surface quality strip steel.

In this embodiment, it also includes a control system 23 and an oxidation potential detection 24. The control system is connected to each acid tank of the cascade overflow continuous pickling system. The redox characteristics of the pickling medium in each pickling tank are related to the input The automatic valve chain setting of adding oxidant, the oxidation potential detection judges the oxidation-reduction characteristics of the pickling medium by detecting the oxidation-reduction potential of the acid solution in each pickling tank, and uses this to control the regulation system to control the pickling corresponding to the multi-stage pickling tank The oxidant is added to the tank to realize the automatic control of the oxidation-reduction characteristics of the pickling medium in each pickling tank in the multi-stage pickling tank, thereby ensuring the effect and consistency of strip cleaning.

Although the present invention has been particularly shown and described in conjunction with preferred embodiments, it will be understood by those skilled in the art that changes in form and details may be made to the present invention without departing from the spirit and scope of the invention as defined by the appended claims. Making various changes is within the protection scope of the present invention.

Claims (10)

1. A kind of hot-rolled stainless steel annealing and pickling process is characterized in that, comprises the following steps:

   Step 1), after the hot-rolled stainless steel enters the annealing furnace to adjust the composition, by adjusting the cooling capacity of the cooling section of the annealing furnace, the temperature of the hot-rolled stainless steel strip at the outlet of the cooling section of the annealing furnace is controlled to be 60-200°C;

   Step 2), the hot-rolled stainless steel strip output from the outlet of the cooling section of the annealing furnace directly enters the cascade overflow continuous pickling system formed by a plurality of sub-troughs connected in series for pickling after being regulated by heat preservation, wherein The cascade overflow continuous pickling system includes a pre-pickling tank located in the front section and a multi-stage low-temperature pickling tank located in the rear section of the pre-pickling tank; the pickling medium of the pre-pickling tank is HCl, and the concentration of HCl is 20-60g/ L, while the pickling medium contains Fe ²⁺ and Fe ³⁺ ; the pickling medium of the low-temperature pickling tank is HCl, the concentration of HCl is 20-150g/L, and the pickling solution contains Fe ²⁺ and Fe ³⁺ ;

   Step 3) The hot-rolled stainless steel strip after being pickled by the cascade overflow continuous pickling system enters the multi-stage rinsing system for rinsing and then drying and coiling.
2. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: in step 2), the temperature at which the hot-rolled stainless steel strip enters the pre-pickling tank is higher than 100°C.
3. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: in step 2), the mode of online dosing of multi-component weak acid and circulation filtration separation is used to regulate and control the Fe in the continuous pickling system with cascade ^overflow and Fe ³⁺ total iron content.
4. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: the concentration of acid solution in each sub-tank of the cascade overflow continuous pickling system increases sequentially, and the total iron content decreases sequentially.
5. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: the step overflow continuous pickling system in step 2) has at least two sections of low-temperature pickling tanks, wherein the first section of pickling medium is reducing system, the last pickling medium is a strong oxidizing system.
6. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: in step 2), by adding an oxidizing agent, the ratio of Fe ²⁺ and Fe ³⁺ is adjusted to control the oxidation of the pickling solution Restore properties.
7. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: the multi-stage rinsing system in step 3) is composed of 3-6 steps of overflow rinsing system, wherein the pressure of the last stage of rinsing water is 5- 10 kg, and the rinse water pressure of the remaining stages is 2-6 kg.
8. The hot-rolled stainless steel annealing and pickling process according to claim 1, characterized in that: in step 1), the hot-rolled stainless steel strip coming out of the cooling section of the annealing furnace realizes the temperature control of the hot-rolled stainless steel strip entering the tank by means of temperature control in the heat preservation chamber control.
9. A hot-rolled stainless steel annealing and pickling equipment, characterized in that it includes a strip steel transmission device and an uncoiler, a welding machine, a looper, an annealing furnace, a heat preservation chamber, a temperature control device, and a step Overflow continuous pickling system, rinse tank and dryer.
10. The hot-rolled stainless steel annealing and pickling equipment according to claim 9, characterized in that: it also includes a control system and oxidation potential detection, the control system is connected to each acid tank of the cascade overflow continuous pickling tank, and the cascade overflow The oxidation-reduction characteristics of the pickling medium in the flow continuous pickling tank are interlocked with the automatic valve for adding oxidants. The oxidation potential detection determines the oxidation-reduction potential of the pickling medium by detecting the oxidation-reduction potential of the acid liquid in the continuous pickling tank with cascade overflow. characteristics, and use this to control the regulation system to add oxidant to the pickling tank corresponding to the cascade overflow continuous pickling tank.

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