A surface reagent for detecting fatigue layer on hot rolling rolls and its application method

Abstract

This invention discloses a surface reagent for detecting fatigue layers on hot-rolled rolls and its application method, used to detect whether a fatigue layer exists on the surface of the hot-rolled roll body. The reagent comprises, by volume percentage: 0.4%–0.6% hydrochloric acid, 0.05%–0.15% phosphoric acid, 10%–12% 30% hydrogen peroxide, 50%–60% ethanol, 20%–30% water, 8%–10% sodium carboxymethyl cellulose, 0.20%–0.40% P420 leveling agent, 0.05%–0.15% Lan826 corrosion inhibitor, and 0.1%–0.2% AMP-95. During testing, the ground roller body is first wiped clean. The reagent is then applied near the midpoint of the roller body. After 120 seconds, if no patchy color difference appears, the fatigue layer is completely removed. If the patchy color difference area is less than 20%, a small area fatigue layer exists, requiring further grinding of 50 μm. If the patchy color difference area is greater than 20%, a medium area fatigue layer exists, requiring further grinding of 100 μm. This invention can determine the presence of a fatigue layer based on the color change of the roller body surface, making the detection fast, accurate, and cost-effective.

Description

Technical Field

[0001] This invention belongs to the field of testing, and mainly relates to reagents and testing methods for detecting whether a fatigue layer exists on the surface of a hot rolling roll. Background Technology

[0002] When hot rolling mill rolls are put into service, defects such as cracks, oxide layers, and fatigue layers inevitably develop on the roll surface (with the fatigue layer being the deepest). Before re-entering the mill, these defects must be completely removed by grinding; otherwise, the roll surface layer may peel off, and in severe cases, it may even cause rolling accidents, leading to scrapped rolled stock, production line shutdowns, and huge losses for the company. Although a large amount of grinding can ensure the removal of the fatigue layer, it will cause wear on the working layer of the roll. In actual production, the amount of grinding is usually controlled by rolling experience. This experience-based control method may leave fatigue layer residue, thus creating safety hazards and even potentially causing major accidents. The depth of the fatigue layer remaining on the roll after grinding is usually about 30μm, and currently it can only be detected by hardness testing or ultrasonic testing. Hardness testing uses a portable hardness tester and a Φ20mm probe to test point by point, taking 4 hours to complete the test of a roll, which is both time-consuming and labor-intensive. Ultrasonic testing requires increased instrument sensitivity and slow testing in sections, taking 2 hours to complete the test of a roll, which is also time-consuming and labor-intensive. Currently, the cost of non-destructive testing of such shallow fatigue layers is high. Therefore, steel companies urgently need a fast, effective and low-cost method for detecting fatigue layers in rolls to confirm whether the fatigue layer has been completely removed after grinding under non-destructive conditions. Summary of the Invention

[0003] The technical problem this invention aims to solve is to provide a surface reagent for detecting fatigue layers on the surface of hot-rolled rolls. After the rolls are ground, they do not need to be removed from the mill; the reagent can be applied to a designated area of ​​the roll body on the grinding machine. The presence of a fatigue layer can be determined based on the color change of the roll surface. This invention provides a fast, accurate, and low-cost detection method.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A surface reagent for detecting fatigue layers in hot rolled rolls comprises, by volume percentage: 0.4%–0.6% hydrochloric acid, 0.05%–0.15% phosphoric acid, 10%–12% 30% hydrogen peroxide, 50%–60% ethanol, 20%–30% water, 8%–10% sodium carboxymethyl cellulose, 0.20%–0.40% P420 leveling agent, 0.05%–0.15% Lan826 corrosion inhibitor, and 0.1%–0.2% AMP-95.

[0005] A further improvement of the technical solution of the present invention is that its chemical composition by volume is as follows: 0.50% hydrochloric acid, 0.10% phosphoric acid, 10% 30% hydrogen peroxide, 25% water, 10% sodium carboxymethyl cellulose, 0.30% P420 leveling agent, 0.10% Lan826 corrosion inhibitor, 0.1% AMP-95, and the balance is ethanol.

[0006] A further improvement of the technical solution of the present invention is that the pH value of the reagent is 2 to 3.

[0007] A further improvement to the technical solution of this invention is as follows: First, the hot-rolled roll body after grinding is wiped clean. Then, the reagent is applied to a certain area near the midpoint of the roll body. After waiting for 120 seconds, the changes in the coated area of ​​the roll body are observed: If no patchy color difference appears, it indicates that the fatigue layer has been completely removed and the roll can proceed directly to the machine stage; if the area of ​​patchy color difference is less than 20%, it indicates that there is a small area fatigue layer, and grinding is added for 50 μm; if the area of ​​patchy color difference is greater than 20%, it indicates that there is a medium area fatigue layer, and grinding is added for 100 μm.

[0008] A further improvement of the technical solution of the present invention is that: a certain area near the midpoint of the roller body refers to a range of 300mm to the left and right of the middle position in the length direction of the roller body.

[0009] The technological advancements achieved by this invention due to the adoption of the above technical solutions are as follows: The 300mm area on either side of the midpoint of the hot rolling roll body is the most severely worn part, and the fatigue layer depth is also the greatest. If the fatigue layer in this area can be completely removed, then the fatigue layer of the entire roll body can also be completely removed. Therefore, when using this reagent to check whether there is a fatigue layer on the surface of the ground roll, it is only necessary to test the 300mm area on either side of the midpoint of the hot rolling roll body. Compared with a comprehensive test of the entire roll body, this method is not only cheaper but also faster. The entire test process is completed within 5 minutes, with almost no impact on the company's production. The cost of the reagent used in this invention is no more than 50 yuan / L, and each test requires the application of about 20-50ml, with a single test cost of only 1 to 2.5 yuan, making the test cost inexpensive. The operation is simple and can be completed by ordinary grinding machine operators without the need for additional manpower. The test results are accurate and reliable, which can prevent accidents during the rolling process and ensure safe production. Attached Figure Description

[0010] Figure 1 This is a photograph of the color difference formed on the surface of the roll after the first application of the reagent of the present invention at the test site of Example 1. Detailed Implementation

[0011] A surface reagent for detecting fatigue layers in hot-rolled rolls comprises hydrochloric acid, phosphoric acid, hydrogen peroxide (30% concentration), ethanol, water, sodium carboxymethyl cellulose, leveling agent P420, corrosion inhibitor Lan826, and AMP-95. Ethanol, hydrochloric acid, and phosphoric acid are all analytical grade; water conforms to the requirements for experimental water in GB / T6682. By volume percentage, the contents of each substance are: hydrochloric acid 0.4%–0.6%, phosphoric acid 0.05%–0.15%, 30% hydrogen peroxide 10%–12%, ethanol 50%–60%, water 20%–30%, sodium carboxymethyl cellulose 8%–10%, P420 leveling agent 0.20%–0.40%, Lan826 corrosion inhibitor 0.05%–0.15%, and AMP-95 0.1%–0.2%, totaling 100%. In practice, the chemical composition of the above substances can be prepared by volume ratio as follows: 0.50% hydrochloric acid, 0.10% phosphoric acid, 10% 30% hydrogen peroxide, 25% water, 10% sodium carboxymethyl cellulose, 0.30% P420 leveling agent, 0.10% Lan826 corrosion inhibitor, 0.1% AMP-95, and the balance being ethanol, so that the pH value of the reagent is controlled at 2-3.

[0012] The above-mentioned method for using the reagent to detect the surface fatigue layer of hot-rolled rolls involves first cleaning the ground hot-rolled roll body, then applying the reagent to a certain area near the midpoint of the roll body. After waiting 120 seconds, observe the changes in the coated area: if no patchy color difference appears, it indicates that the fatigue layer has been completely removed and the roll can proceed directly to the machine stage; if the area of ​​patchy color difference is less than 20%, it indicates the presence of a small area fatigue layer, requiring further grinding of 50 μm; if the area of ​​patchy color difference is greater than 20%, it indicates the presence of a medium area fatigue layer, requiring further grinding of 100 μm. The certain area near the midpoint of the roll body refers to a range of 300 mm to the left and right of the midpoint along the length of the roll body.

[0013] This reagent is applied after the hot rolling mill rolls have been refurbished. It reacts chemically with alloying elements such as iron, chromium, nickel, molybdenum, vanadium, and tungsten on the roll surface, causing a color change and forming a thin film. The main reaction is: Fe + 2H⁺ + →Fe 2+ +H2↑, H2O2 + 2Fe + 6H+ + → 2Fe 3+ +2H2O+2H2↑, the reaction of other alloying elements with this reagent is similar to this reaction.

[0014] Ethanol primarily serves as a diluent and corrosion inhibitor; phosphoric acid generates ferric phosphate colloids to fill pores and improve film density; sodium carboxymethyl cellulose (CMC-Na), as a multifunctional additive, mainly functions through its thickening, stabilizing, and water-retaining properties. Furthermore, CMC-Na can enhance coating density and smoothness, reduce cracking, and is relatively economical and environmentally friendly; Lan826 corrosion inhibitor inhibits excessive dissolution of carbides and reduces surface roughness; leveling agent P420 is a polyether-modified polydimethylsiloxane, a highly active, water-soluble surfactant that can quickly and effectively reduce the surface tension of aqueous systems, improve coating spreading ability, enhance leveling, flowability, and substrate wettability, prevent pinholes, eliminate brush marks, resist high temperatures, and improve anti-adhesion; AMP-95, a multifunctional organic amine additive, has the chemical name 2-amino-2-methyl-1-propanol (C4H4H4O7), and the molecular formula is C4H4H4O7. 11 No, it can adjust the pH of the reagent and can be added as needed.

[0015] The materials used for hot rolling rolls are high-alloy steel or cast iron. During the rolling process after hot rolling rolls are put into service, the fatigue layer is the result of the coupled effects of multiple factors, including cyclic heating (the temperature of high-temperature rolled parts can reach over 1000℃) and cooling, alternating thermal stress, and superposition of mechanical stresses (rolling force, friction, and shear stress, etc.). In terms of chemical composition, Cr, Mo, and W in hot rolling rolls mainly improve high-temperature strength, wear resistance, and hardenability, and the carbides they form also contribute to wear resistance; V, Nb, and Ti can generate fine, high-hardness carbide particles, which are dispersed in the matrix and can significantly improve resistance to thermal fatigue.

[0016] After applying this reagent to a refurbished hot-rolled roll, taking a high-speed steel roll as an example, a uniform light yellow film will form on the normal area of ​​the roll surface coated with this reagent. W and V elements on the roll surface preferentially oxidize to form WO3 and V2O5, iron is oxidized to form the main phase Fe3O4, and Cr and Mo undergo selective oxidation (passivation effect) to form Cr2O3 and MoO2. Carbides on the surface of the hot-rolled roll will also oxidize to form products. These oxidized structures form a continuous nanoscale film, which is generally yellow. If a residual fatigue layer exists on the roll surface, under cyclic stress, the microstructure will undergo drastic changes, including grain fragmentation, dislocation entanglement, and phase transformation, forming nanocrystalline structures. These nanocrystalline regions resist corrosion and appear white, i.e., spots visible to the naked eye. The extent of fatigue layer removal can be determined by the proportion of the spotted color difference area to the entire roll surface. Compared with hardness testing and ultrasonic non-destructive testing, this testing method is fast, accurate, and low-cost.

[0017] Similar discoloration can also occur in other materials besides high-speed steel, such as high-chromium steel and high-chromium iron.

[0018] When using the reagent of this invention, first wipe the ground hot rolling roll body clean, and then apply the reagent to an area 300mm to the left and right of the midpoint of the roll body. After waiting for 120 seconds, observe the changes on the surface of the roll body in the designated coating area. If no patchy color difference appears, it indicates that the fatigue layer has been completely removed and the roll can directly enter the rolling process for continued rolling service; if the area of ​​patchy color difference is less than 20%, it indicates that there is a small area fatigue layer, and grinding is required for an additional 50μm; if the area of ​​patchy color difference is greater than 20%, it indicates that there is a medium area fatigue layer, and grinding is required for an additional 100μm. Example 1

[0019] A high-speed steel roll on a hot-rolling line at a domestic steel mill, with a roll diameter of Φ500, after rolling a certain quantity of steel, is removed from the mill and ground down to remove a thickness of 150μm. The roll is then dried, and this reagent is applied to an area 300mm to the left and right of the midpoint along the roll's length. After waiting 120 seconds, patchy color differences are observed, with the area of ​​these patches less than 20% (see attached). Figure 1 Then, it was ground to a depth of 50μm. Upon re-inspection, no patchy color difference was found in the coated area. Ultrasonic testing also revealed no fatigue layer, indicating that the roll surface is free of fatigue layer. A total of 40ml of reagent was used, costing 2 yuan. Example 2

[0020] A high-chromium iron roll on a hot-rolling line at a domestic steel mill, with a roll diameter of Φ650, was ground to 180μm after rolling. The roll was then dried, and this reagent was applied to a 300mm area to the left and right of the roll's midpoint. After 120 seconds, patchy color differences appeared, covering more than 20% of the area. After grinding an additional 100μm, the coated area no longer showed patchy color differences, and hardness testing revealed no fatigue layer. A total of 52ml of reagent was used, costing 2.6 yuan. Because the main components are similar, the photograph is not significantly different from that of Example 1. Example 3

[0021] A domestic steel mill's hot-rolling line produced high-chromium steel rolls with a diameter of Φ800. After the rolls came off the mill, they were ground to a thickness of 170μm, dried, and coated with this reagent in a 300mm area to the left and right of the roll's midpoint. After 120 seconds, no patchy color difference was observed, and ultrasonic testing revealed no fatigue layer. A total of 32ml of reagent was used, costing 1.6 yuan.

Claims

1. A surface reagent for detecting fatigue layers in hot-rolled rolls, characterized in that... It includes, by volume percentage: 0.4%–0.6% hydrochloric acid, 0.05%–0.15% phosphoric acid, 10%–12% 30% hydrogen peroxide, 50%–60% ethanol, 20%–30% water, 8%–10% sodium carboxymethyl cellulose, 0.20%–0.40% P420 leveling agent, 0.05%–0.15% Lan826 corrosion inhibitor, and 0.1%–0.2% AMP-95.

2. The surface reagent for detecting fatigue layers in hot-rolled rolls according to claim 1, characterized in that: Its chemical composition by volume is as follows: 0.50% hydrochloric acid, 0.10% phosphoric acid, 10% 30% hydrogen peroxide, 25% water, 10% sodium carboxymethyl cellulose, 0.30% P420 leveling agent, 0.10% Lan826 corrosion inhibitor, 0.1% AMP-95, and the balance is ethanol.

3. The reagent for detecting the surface fatigue layer of hot-rolled rolls according to any one of claims 1 or 2, characterized in that: The pH value of the reagent is 2 to 3.

4. A method for using the reagent for detecting the surface fatigue layer of a hot-rolled roll as described in claim 1 or 2, characterized in that: First, wipe the ground hot-rolled roll body clean. Then, apply this reagent to a certain area near the midpoint of the roll body. After waiting for 120 seconds, observe the changes in the coated area of ​​the roll body: if no patchy color difference appears, it means that the fatigue layer has been completely removed and the roll can proceed directly to the machine stage; if the area of ​​patchy color difference is less than 20%, it means that there is a small area fatigue layer, and grinding is required for an additional 50 μm; if the area of ​​patchy color difference is greater than 20%, it means that there is a medium area fatigue layer, and grinding is required for an additional 100 μm.

5. The method for using a reagent for detecting the surface fatigue layer of a hot-rolled roll according to claim 4, characterized in that: The certain area near the midpoint of the roller body refers to a range of 300mm to the left and right of the midpoint in the length direction of the roller body.

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