CN108687134B - Method for reducing thermal stress spalling of roller oxide film - Google Patents
Method for reducing thermal stress spalling of roller oxide film Download PDFInfo
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- CN108687134B CN108687134B CN201810643883.6A CN201810643883A CN108687134B CN 108687134 B CN108687134 B CN 108687134B CN 201810643883 A CN201810643883 A CN 201810643883A CN 108687134 B CN108687134 B CN 108687134B
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- thermal stress
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/06—Lubricating, cooling or heating rolls
- B21B27/10—Lubricating, cooling or heating rolls externally
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/06—Lubricating, cooling or heating rolls
- B21B27/10—Lubricating, cooling or heating rolls externally
- B21B2027/103—Lubricating, cooling or heating rolls externally cooling externally
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B2201/00—Special rolling modes
- B21B2201/06—Thermomechanical rolling
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Abstract
The invention discloses a method for reducing the thermal stress spalling of a roller oxide film, belonging to the technical field of steel rolling processes. The invention provides a method for reducing the thermal stress spalling of an oxide film of a roller, which aims to reduce the heat transfer when strip steel is in contact with the roller, reduce the temperature of the roller, reduce the thermal stress crack of the roller and improve the surface quality of a product, and comprises the following steps: when the strip steel is rolled, controlling the F1 biting rolling speed to be not less than 1 m/s; controlling the spray angle and the spray pressure of the anti-peeling falling water on the inlet side of the roller; the spraying angle takes 45 degrees as the lower limit and the spraying water flow is not blocked by the roller as the upper limit; the injection pressure is 8-12 bar. The method reduces the heat transfer when the strip steel is in contact with the roller by reasonably controlling the injection angle and the injection pressure of the anti-stripping falling water on the inlet side of the working roller on the lower side of the finish rolling, thereby reducing the temperature of the roller and the thermal stress cracking defect of the roller and improving the surface quality of the product.
Description
Technical Field
The invention belongs to the technical field of steel rolling processes, and particularly relates to a method for reducing the thermal stress spalling of a roller oxide film.
Background
The hot rolling roller is in a high-temperature and high-pressure working environment for a long time, and bears a large load, and various roller defects are easily formed, so that the hot rolling roller becomes a factor for restricting the improvement of the product quality and the improvement of the dimensional precision. The control of the roll temperature is the most influential of all factors and is also the most operable. For a long time, engineers have focused on improving the efficiency and uniformity of roll cooling.
CN 105598172 a discloses a method for preventing oxide film peeling of hot strip tandem mill roll, which sprays cooling liquid (mist) into the roll nip at the inlet side of the mill to keep the roll nip wet; the method is used for isolating the heat of the high-temperature strip steel from being transferred to the roller and simultaneously taking away the heat on the surface of the roller, and the method for reducing the peeling of the oxide film on the surface of the roller is achieved in a water lubrication mode. CN 105710131A discloses a method for axially distributing water quantity of a cooling water outlet of a hot continuous rolling roller, which is used for preparing the cooling water quantity of the roller according to the rolling width so as to achieve the purpose of increasing the temperature uniformity of the roller. CN 105817480 a discloses a device for inhibiting oxidation rate of a roller and a method for using the same, which utilize a gas nozzle to realize gas protection after the roller is separated from a roller nip, and reduce the probability of contact with air at a high temperature stage of the roller surface, thereby inhibiting the oxidation rate of the roller and forming a uniform and dense oxide film on the roller surface. However, these studies neglect the thermal stress problem associated with the roll cooling process. The roller cooling process generates thermal stress, the higher the temperature is, the higher the cooling speed is, the higher the stress is, the alternating load effect is generated in the roller in the circulating heating and cooling process, and finally, thermal cracks are generated to influence the surface quality of products.
Disclosure of Invention
The invention aims to solve the technical problems of reducing the heat transfer when the strip steel is in contact with the roller, achieving the purposes of reducing the temperature of the roller and reducing the thermal stress crack of the roller, thereby improving the surface quality of products.
The technical scheme adopted by the invention for solving the technical problems is to provide a method for reducing the thermal stress spalling of the oxide film of the roller, and the method controls the spray angle and the spray pressure of the anti-spalling water falling on the inlet side of the roller when strip steel is rolled; the spray angle is defined as an included angle of less than 90 degrees between the spray direction and the vertical direction, the included angle takes 45 degrees as a lower limit, and the included angle takes the spray water flow which is not blocked by the roller as an upper limit; the injection pressure is 8-12 bar.
Preferably, in the method for reducing the thermal stress spalling of the oxide film of the rolling roll, the rolling roll is a lower working roll of a frame of a finishing mill group F1-F3.
In the method for reducing the thermal stress spalling of the roller oxide film, the flow rate of the anti-spalling falling water is 7.0-7.2L/(mm & min).
In the method for reducing the thermal stress spalling of the oxide film of the roller, the F1 bite rolling speed of the strip steel is not less than 1.0 m/s.
In the method for reducing the thermal stress spalling of the oxide film of the roller, the rolling is finished within 1s after the surface of the strip steel is cooled.
The invention has the beneficial effects that:
according to the method, the injection angle and the injection pressure of the anti-stripping falling water on the inlet side of the lower working roll are reasonably controlled, so that the surface layer of the strip steel is rapidly and rapidly cooled, the cooling amplitude of the strip steel is controlled to be 80-120 ℃, the heat transfer of the strip steel in contact with the roll is reduced, the strip steel is in contact deformation with the roll before the strip steel turns red, the purpose of reducing the temperature of the roll is achieved, the thermal stress cracking defect of the roll is reduced, the surface quality of a product is improved, and the rolling fraction defective of the strip steel is not more than 3.; the method can also reduce the consumption of cooling water, and has the advantages of simple operation, strong feasibility and wide application value.
Drawings
FIG. 1 is a schematic view of the anti-peeling water adjustment and relative positions of various components of the present invention.
Detailed Description
Specifically, the method for reducing the thermal stress spalling of the oxide film of the roller comprises the steps of controlling the spray angle and the spray pressure of the anti-spalling water on the inlet side of the roller when strip steel is rolled; the spray angle is defined as an included angle of less than 90 degrees between the spray direction and the vertical direction, the included angle takes 45 degrees as a lower limit, and the included angle takes the spray water flow which is not blocked by the roller as an upper limit; the injection pressure is 8-12 bar.
Because the lower working rolls of the frames of the finishing mill groups F1-F3 have poor cooling conditions and are easy to have defects, the injection angle and the injection pressure of the anti-peeling water falling on the inlet side of the lower working rolls of the frames of the finishing mill groups F1-F3 are controlled in an important way.
The surface temperature of the strip steel before cooling is about 900-1050 ℃, the method reasonably controls the spray angle (such as the included angle beta between a spray gun and the vertical direction) and the spray pressure of the anti-peeling falling water at the inlet side of the roller, the spray angle of the anti-peeling falling water is controlled on the basis of the principle that the time from the cooling of the surface layer of the strip steel to the entering of the strip steel is short (in the prior art, the spray angle of the anti-peeling falling water is controlled on the basis of the principle that the distance from the spray gun to the strip steel is short, such as an included angle alpha between a spray gun and the vertical direction in figure 1), the short and sharp temperature reduction of the surface layer of the strip steel is achieved, the surface temperature reduction range of the strip steel is 80-120 ℃ (the contact time of the strip steel and a roller is short, and the roller is cooled after each contact, so the temperature of, and the deformation of the strip steel after contacting with the roller is finished before the strip steel is re-reddened, so that the purpose of reducing the temperature of the roller is achieved, and the defect of thermal stress cracking of the roller is reduced.
According to the method, the water pressure and the water quantity are controlled, the flow of the peeling-proof falling water is 7.0-7.2L/(mm.min), the cooling depth of the strip steel is 1/20-1/10 of the thickness of the strip steel before biting, so that the red return time is controlled, then the rolling speed of the strip steel is controlled to be not less than 1.0m/s, the strip steel is in contact deformation with a roller before red return, rolling is completed within 1s after the surface of the strip steel is cooled, the temperature is relatively low when the strip steel is in contact with the roller, and therefore the biting rolling process is completed by keeping enough surface low-temperature time under the condition that the integral temperature of the strip steel is not reduced too much to influence the organization.
Preferably, the method for reducing the thermal stress spalling of the roll oxide film comprises the following steps: when the strip steel is rolled, controlling the spray angle and the spray pressure of the anti-stripping falling water on the inlet side of the lower working roll of the frames F1-F3 of the finishing mill group; the spray angle is defined as an included angle of less than 90 degrees between the spray direction and the vertical direction, the included angle takes 45 degrees as a lower limit, and the included angle takes the spray water flow which is not blocked by the roller as an upper limit; the injection pressure is 8-12 bar; controlling the flow rate of the anti-peeling falling water to be 7.0-7.2L/(mm & min); controlling the F1 bite rolling speed of the strip steel to be not less than 1.0m/s, and finishing rolling within 1s after the surface of the strip steel is cooled.
The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.
Example 1
The embodiment reduces the thermal stress spalling of the roll oxide film by the following operations:
when the strip steel is rolled, the surface temperature (namely the finish rolling inlet temperature) before the strip steel is cooled is 950 ℃, the injection angle of the anti-stripping falling water on the inlet side of the lower working roll of a rack of a finishing mill group F1-F3 is controlled to be 56 degrees, the flow rate of the anti-stripping falling water is 7.0L/(mm & min), the injection pressure is 10bar, the surface temperature of the strip steel is reduced to 870 ℃, the cooling depth of the strip steel is subjected to analog calculation, and the cooling depth of the strip steel is 7% of the thickness of the strip steel before the strip steel bites into the rack; controlling the F1 biting rolling speed of the strip steel to be not less than 1.0m/s, and finishing rolling within 1s after the surface of the strip steel is cooled; the rolling condition of the strip steel is shown in Table 1.
Example 2
The embodiment reduces the thermal stress spalling of the roll oxide film by the following operations:
when the strip steel is rolled, the surface temperature (namely the finish rolling inlet temperature) before the strip steel is cooled is 1050 ℃, the injection angle of the anti-stripping falling water on the inlet side of the lower working roll of a rack of a finishing mill group F1-F3 is controlled to be 56 degrees, the flow rate of the anti-stripping falling water is 7.0L/(mm & min), the injection pressure is 10bar, the surface temperature of the strip steel is reduced to 950 ℃, the cooling depth of the strip steel is subjected to analog calculation, and the cooling depth of the strip steel is 10% of the thickness of the strip steel before the strip steel is bitten; controlling the F1 biting rolling speed of the strip steel to be not less than 1.0m/s, and finishing rolling within 1s after the surface of the strip steel is cooled; the rolling condition of the strip steel is shown in Table 1.
Comparative example 1
When the strip steel is rolled, the surface temperature (namely the finish rolling inlet temperature) before the strip steel is cooled is 950 ℃, the injection angle of the anti-stripping falling water at the inlet side of the lower working roll of the finishing mill group F1-F3 rack is 40 degrees, the flow rate of the anti-stripping falling water is 6.8L/(mm & min), the injection pressure is 6bar, the time from the cooling completion position to the biting position is relatively long, the speed of the strip steel is not required, the strip steel returns red, and the surface temperature of the strip steel is about 910 ℃ during biting; the rolling condition of the strip steel is shown in Table 1.
Comparative example 2
When the strip steel is rolled, the surface temperature (namely the finish rolling inlet temperature) before the strip steel is cooled is 1050 ℃, the injection angle of the anti-stripping falling water at the inlet side of the lower working roll of the frames of the finishing mill group F1-F3 is 40 degrees, the flow rate of the anti-stripping falling water is 6.8L/(mm & min), the injection pressure is 6bar, the time from the cooling completion position to the biting position is relatively long, the speed of the strip steel is not required, the strip steel returns to red, and the surface temperature of the strip steel is about 990 ℃ during the biting; the rolling condition of the strip steel is shown in Table 1.
TABLE 1 strip Rolling situation
| Roll temperature/. degree.C | Production quantity/volume | Percent defective% | |
| Example 1 | 550 | 200 | 2 |
| Example 2 | 580 | 200 | 3 |
| Comparative example 1 | 620 | 200 | 13 |
| Comparative example 2 | 640 | 200 | 11.2 |
Therefore, the method can ensure that the cooling amplitude of the strip steel surface is 80-120 ℃, so that the temperature is relatively low when the strip steel is in contact with the roller, and the temperature of the roller is reduced; the defect rate of the scale on the surface of the strip steel is obviously reduced compared with that of the comparative example.
Claims (1)
1. The method for reducing the thermal stress spalling of the roller oxide film is characterized by comprising the following steps: when the strip steel is rolled, controlling the injection angle and the injection pressure of the anti-stripping falling water on the inlet side of the roller; the spray angle is defined as an included angle of less than 90 degrees between the spray direction and the vertical direction, the included angle takes 45 degrees as a lower limit, and the included angle takes the spray water flow which is not blocked by the roller as an upper limit; the injection pressure is 8-12 bar; the flow rate of the anti-peeling falling water is 7.0-7.2L/(mm & min); controlling the cooling amplitude of the surface of the strip steel to be 80-120 ℃, wherein the cooling depth of the strip steel is 1/20-1/10 of the thickness of the strip steel before biting; the roller is a lower working roller of a frame of a finishing mill group F1-F3; the F1 biting rolling speed of the strip steel is not less than 1.0 m/s; and finishing rolling within 1s after the surface of the strip steel is cooled.
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| CN201810643883.6A CN108687134B (en) | 2018-06-21 | 2018-06-21 | Method for reducing thermal stress spalling of roller oxide film |
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| CN201810643883.6A CN108687134B (en) | 2018-06-21 | 2018-06-21 | Method for reducing thermal stress spalling of roller oxide film |
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| CN108687134B true CN108687134B (en) | 2020-10-09 |
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| EP2025423B1 (en) * | 2006-07-27 | 2013-11-20 | JFE Steel Corporation | Cooler and cooling method of hot rolled steel band |
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| JP2010158690A (en) * | 2009-01-07 | 2010-07-22 | Jfe Bars & Shapes Corp | Apparatus for cooling rolling mill roll |
| CN205020515U (en) * | 2015-08-24 | 2016-02-10 | 江苏省冶金设计院有限公司 | Roll aqueous vapor cooling nozzle assembly |
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