Method for improving control of post-quenching back defects in giga-grade martensitic wear-resistant steel

Abstract

The application discloses a control method for improving the backboard shape defect of giga-grade martensitic wear-resistant steel after quenching, and belongs to the technical field of steel production. The main production mode of the giga-grade martensitic wear-resistant steel is to complete a quenching cooling process through a roller bottom heating furnace and a roller quenching machine. The backboard shape defect control method comprises the following steps in sequence: backboard shape flatness measurement, backboard shape defect characteristic calculation, backboard shape defect characteristic determination, backboard shape process parameter adjustment aiming at the middle transverse bending defect characteristic quantity, backboard shape process parameter adjustment aiming at the head and tail defect deformation difference quantity, and backboard shape flatness characteristic detection determination after adjustment. Through the method, the process parameter adjustment problem of the backboard shape back defect after quenching caused by complex and changeable actual working conditions, such as environmental water temperature, temperature change, heating furnace combustion temperature change and quenching machine pinch roll wear and the like, is effectively solved, and the effectiveness of the backboard shape process parameter setting, the backboard shape qualified rate and the production efficiency of the production line are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel quenching production, and particularly relates to a control method for back defect of gigapascal grade martensite wear-resistant steel after quenching.

[0002] The control method for back defect of gigapascal grade martensite wear-resistant steel after quenching. BACKGROUND

[0003] With the continuous development and improvement of the industrial technology level in China, the overall demand for medium plates in the shipbuilding industry, the mechanical processing industry, the petroleum chemical industry, bridge construction and other industries is increasing, and the demand for high-grade high-strength steel plates is also increasing.

[0004] The production mode of the high-grade high-strength quenched and tempered wear-resistant steel is mainly to use a roller bottom heating furnace and a roller quenching machine to produce the high-grade high-strength quenched and tempered wear-resistant steel. The setting of quenching process parameters is an important process for producing the gigapascal grade quenched and tempered wear-resistant steel, and is generally manually set by an operator. In the actual production process, the changes of the daily ambient temperature, the cooling water temperature, the cooling water pressure and the combustion state of the heating furnace affect the setting of the quenching process parameters, so that the plate shape of the quenched steel plate is prone to various complex flatness defects. The back defect is a plate shape defect (as shown in the attached figure) that often occurs in the quenching and cooling production process of the high-strength steel plate, and the main feature is that the middle part of the steel plate presents a transverse bend (or a reverse transverse bend), the head and tail are coupled with a certain downward buckling or upward bending (for the case of reverse transverse bend), and the defect deformation amount of the tail is greater than that of the head. At present, there is no clear way to determine the defect and adjust the process parameters, which seriously affects the plate shape of the subsequent produced steel plate, reduces the yield and the qualification rate, affects the production and delivery rhythm and the use of downstream customers, and causes certain economic losses. Figure 6 、 7 SUMMARY

[0005] The present application aims at the above technical problems, overcomes the deficiencies of the prior art, and provides a control method for improving the back plate shape defect of the gigapascal grade martensite wear-resistant steel after quenching. Specifically, the method comprises the following steps: measuring the plate shape flatness, determining the plate shape defect characteristics, adjusting the plate shape process parameters according to the characteristic amount of the transverse bend defect in the middle part of the steel plate, adjusting the plate shape process parameters according to the defect deformation difference amount of the head and tail, and measuring and determining the flatness characteristics of the adjusted plate shape. The back deformation characteristics of the gigapascal grade martensite wear-resistant steel in different regions after quenching are measured, characterized and determined, and the corresponding process parameters are adjusted, so that the plate shape quality is effectively optimized.

[0006] A control method for improving the back plate shape defect of gigapascal grade martensite wear-resistant steel after quenching, the gigapascal grade martensite wear-resistant steel is produced by a quenching process of a roller quenching machine, and the control method comprises the following steps: Figure 10

[0007] (1) measuring the plate shape flatness;​​

[0008] (2) Plate shape defect feature calculation;

[0009] (3) Plate shape defect feature determination;

[0010] (4) Plate shape process parameter adjustment for middle transverse bend defect feature quantity;

[0011] (5) Plate shape process parameter adjustment for head and tail defect deformation difference quantity;

[0012] (6) Measurement and calculation determination of plate shape flatness feature after adjustment.

[0013] Further, in step (1), in the plate shape flatness measurement link, 12 measurement positions are set at the four corners and the middle position of the steel plate, respectively marked as measurement points 1-12 (see Figure 1 , the number of measurement points can be changed according to the size and deformation degree of the steel plate) ; first, place the ruler at the corresponding edge or middle measurement position of the steel plate, then insert the caliper into the gap between the ruler and the upper surface of the steel plate to read the indication h 1A , h 1B

[0014] , etc. (see Figure 2 , Figure 3 ).

[0015] Further, the plate shape data recorded in step (1) are calculated for defect features:

[0016] 1) Calculate the feature quantity of the middle transverse bend defect (see Figure 4 )

[0017]

[0018] 2) Calculate the upwarp or downwarp amplitude of the head and tail of the steel plate respectively, i.e. the comprehensive deformation amplitude Δh 头 and Δh 尾 and the head-tail deformation difference quantity Δh; the specific calculation method is (see Figure 5 ) :

[0019] Taking measurement point 1 as an example, the deformation amplitude Δh1 at 1 is calculated as follows:

[0020] Δh1 = h 1A -h 1B

[0021] Similarly, Δh2, Δh3, Δh4, Δh5 are calculated accordingly;

[0022] Calculate the head comprehensive deformation amplitude Δh 头

[0023]

[0024] Similarly, the comprehensive deformation amplitude Δh of the tail part is calculated 尾 ; and finally the head-tail deformation difference Δh is calculated

[0025] Δh = Δh 尾 - Δh 头 .

[0026] Further, the defect characteristic value calculated in step (2) is subjected to defect characteristic determination:

[0027] 1) If the middle transverse bending characteristic quantity w, the comprehensive deformation amplitude Δh of the head part of the steel plate, and the comprehensive deformation amplitude Δh of the tail part of the steel plate are all positive, 头 and

[0028] Δh 尾 and the head-tail deformation difference Δh are all positive, it is determined that the plate shape defect is a positive turtleback;

[0029] 2) If the middle transverse bending characteristic quantity w, the comprehensive deformation amplitude Δh of the head part of the steel plate, and the comprehensive deformation amplitude Δh of the tail part of the steel plate are all negative, 头 and

[0030] Δh 尾 and the head-tail deformation difference Δh are all negative, it is determined that the plate shape defect is a negative turtleback;

[0031] 3) Other cases are non-turtleback defects, and other plate shape control methods are used for regulation.

[0032] Further, the plate shape process parameter adjustment for the transverse bending defect characteristic quantity in the middle part of the steel plate: the transverse bending characteristic in the middle part of the steel plate is due to the improper adjustment of the cooling water ratio parameters on the upper and lower surfaces of the roller quenching machine, resulting in the different synchronization of the cooling rates of the upper and lower surfaces in the thickness direction during the cooling process of the steel plate, so that the transverse bending occurs on the side with faster cooling rate. The adjustment method is to adjust the cooling water ratio of the upper and lower surfaces. If the middle transverse bending characteristic quantity w is positive, that is, the transverse bending occurs on the upper surface of the steel plate, it indicates that the cooling rate of the upper surface is large and the cooling rate of the lower surface is small, so it is necessary to increase the cooling water ratio b of the original lower surface. Through actual production, it can be obtained that the function relationship between the water ratio adjustment improvement utility value a and the thickness d of the steel plate satisfies: a = 0.002d - 0.011; the actual meaning of a is that for a steel plate with a thickness of d mm, to improve 1 mm of transverse bending defect quantity, the cooling water ratio needs to be adjusted by a magnitude; therefore, the cooling water ratio needs to be adjusted by a magnitude of a x w, and the adjusted cooling water ratio is b + (0.002d - 0.011) x w.

[0033] Further, the plate shape process parameter adjustment for the head-tail deformation difference: the deformation difference of the head and tail of the steel plate is mainly caused by the difference in the cooling temperature of the head and tail of the steel plate; the temperature of the head of the steel plate is higher during cooling, and the temperature of the tail is obviously lower than that of the head due to heat dissipation during the forward movement of the steel plate along the roller; therefore, the moving speed v of the original steel plate can be adjusted, for the steel plate with a thickness of less than 12 mm, in order to ensure the hardenability, the speed cannot be higher than V m / s, and the adjustment improvement effect of the roller moving speed is e = 0.015 m -1 ·s -1 ·mm -1 that is, to improve the flatness difference of 1 mm, the roller running speed needs to be increased by 0.015 m / s, and therefore the moving speed of the adjusted steel plate is v + e x Δh.

[0034] Further, after the process parameter setting is completed, the flatness of the newly discharged steel plate is measured again.

[0035] Further, after the flatness measurement of the newly discharged steel plate is completed, the flatness defect feature calculation is performed on the recorded flatness data of the newly discharged steel plate.

[0036] Further, the flatness standard judgment is performed on the defect feature value calculated in step (6), and the limited standard of the middle transverse bending defect is W, and the limited standard of the head-tail deformation difference is Y:

[0037] 1) if |w| < W and |Δh| < Y, it is judged that the flatness condition meets the standard, the tortoise back defect is improved well, and thus the flatness defect control of the tortoise back is completed;

[0038] 2) if the parameter condition does not meet the judgment condition 1), it is judged that the flatness does not meet the standard, and the defect feature judgment of step (3) is returned to, and a new round of process parameter adjustment process is performed;

[0039] Thus, the design of the control method for improving the tortoise back flatness defect of the gigapascal grade martensitic wear-resistant steel after quenching is completed.

[0040] Through the method, the process parameter adjustment problem of the flatness tortoise back defect after quenching caused by various factors such as complex and changeable actual working conditions, for example, environmental water temperature, temperature change, heating furnace combustion temperature change, and quenching machine pinch roller wear, is effectively solved, and the effectiveness of the flatness process parameter setting, the flatness qualified rate, and the production efficiency of the production line are improved.

[0041] By using the method, the maximum flatness of the gigapascal grade wear-resistant steel after quenching can be controlled within 1 mm, the flatness difference of the head and tail is controlled to the minimum level, the tortoise back flatness problem in production is improved, the qualified rate and the production efficiency are improved, and the economic loss of the enterprise caused by the flatness not meeting the standard is reduced. Attached Figure Description

[0042] Figure 1 Schematic diagram of the steel plate straightness measurement location.

[0043] Figure 2 Diagram of feeler gauge measurement.

[0044] Figure 3 Diagram showing the placement of the ruler and the measurement position of the feeler gauge.

[0045] Figure 4 Schematic diagram for calculating transverse bending defects in the middle section.

[0046] Figure 5 Schematic diagram for calculating the difference in deformation between the head and tail.

[0047] Figure 6 Facing the turtle's back,

[0048] Figure 7 Reverse turtle back,

[0049] Figure 8 Actual measured plate shape data,

[0050] Figure 9 The shape data of the newly produced steel plates.

[0051] Figure 10 Process flow diagram. Detailed Implementation

[0052] The present invention will be further described below with reference to specific embodiments:

[0053] Measurement data of a 10mm thick NM400 martensitic steel plate from a heat treatment production line at a certain factory are attached. Figure 8 The current process parameters are set with a lower surface water ratio of b = 1.3 and a steel plate moving speed of v = 0.24 m / s on the roller conveyor. In order to ensure the hardenability of the steel plate, the speed cannot exceed 0.36 m / s.

[0054] The standard requirement for the straightness of the middle part of the product is less than W = 1.5 mm / m, and the difference in deformation between the head and tail defects is not higher than Y = 2 mm / m.

[0055] 1. Calculate defect features based on the obtained plate shape data:

[0056] (1) Calculate the characteristic quantity w of the transverse bending defect in the middle.

[0057]

[0058] (2) Calculate the combined deformation amplitude Δh of the head and tail of the steel plate. 头 and Δh 尾and the head-tail deformation difference Δh

[0059] The deformation amplitude Δh1 at 1 is:

[0060] Δh1 = h 1A -h 1B = 4

[0061] Similarly, Δh2 = 2, Δh3 = 3, Δh4 = 3, Δh5 = 3 are calculated accordingly;

[0062] The head comprehensive deformation amplitude Δh is calculated 头

[0063]

[0064] The tail comprehensive deformation amplitude Δh is calculated accordingly 尾 = 4.4; and the head-tail deformation difference Δh

[0065] Δh = Δh 尾 - Δh 头 = 1.3

[0066] 2. Defect feature judgment is performed on the calculated defect feature values:

[0067] Since the middle transverse bend feature value w, the head and tail comprehensive deformation amplitudes Δh 头 and Δh 尾 and the head-tail deformation difference Δh are all positive, it can be determined that the plate shape defect is a positive turtleback;

[0068] 3. Plate shape process parameter debugging for the middle transverse bend defect feature value:

[0069] The middle transverse bend feature value w is positive, that is, the upper surface of the steel plate appears transverse bending, indicating that the cooling rate of the upper surface is large and the cooling rate of the lower surface is small, so the cooling water ratio of the original lower surface needs to be increased. The improvement effect value a of the water ratio adjustment is 0.002d-0.01 = 0.019. Therefore, the adjusted cooling water ratio here is

[0070] b + a x w = 1.36

[0071] 4. Plate shape process parameter debugging for the head-tail defect deformation difference:

[0072] Δh = 1.3, so the moving speed v of the original steel plate is debugged. In order to ensure the hardenability, the speed cannot be higher than 0.36 m / s, and the adjusted steel plate moving speed v + e x Δh = 0.26 m / s can be calculated. Figure 9 5. After completing the process parameter setting, the plate shape of the newly discharged steel plate is measured again, and the plate shape measurement data as shown in the attached Figure 9 is obtained.

[0073] 6. Perform the same defect feature calculation as step 2 on the recorded new as-rolled strip shape data; obtain

[0074] w 新 = 1, Ah 新 = 0.8

[0075] 7. Perform the strip shape standard judgment for the calculated defect feature values:

[0076] |w 新 | < W, | Ah 新 |

Claims

1. A method for controlling the tortoise-shell pattern defect in quenched Gibbs-grade martensitic wear-resistant steel, characterized in that, The GPa - grade martensitic wear - resistant steel is produced by the quenching process of a roller quenching machine. The control method includes the following steps: (1) Plate straightness measurement; In the plate straightness measurement process, 12 measurement positions are set at the four corners and the middle of the steel plate and marked as measurement points 1 to 12 respectively; First, the scale is placed at the corresponding measurement position on the edge or middle of the steel plate, and then the feeler gauge is inserted into the gap between the scale and the upper surface of the steel plate to read the reading h of the feeler gauge at the corresponding position. 1A h 1B ; Calculate the defect characteristics based on the plate shape data recorded in step (1): 1) Calculate the characteristic quantity w of the central transverse bending defect: 2) Calculate the upward or downward curvature of the head and tail of the steel plate, i.e., the comprehensive deformation amplitude Δh. 头 and Δh 尾 And the difference in deformation between the head and tail, Δh; the specific calculation method is as follows: Taking measurement point 1 as an example, the calculation method of the deformation amplitude Δh1 at point 1 is: Δh1=h 1A -h 1B Similarly, Δh2, Δh3, Δh4, and Δh5 are calculated accordingly; Calculate the overall head deformation amplitude Δh 头 Similarly, the overall deformation amplitude Δh at the tail is calculated. 尾 Finally, the difference in deformation between the head and tail, Δh, is calculated. Δh=Δh 尾 -Δh 头 ; (2) Calculate the plate shape defect characteristics; (3) Determine the plate shape defect characteristics; (4) Adjust the plate shape process parameters for the characteristic quantity of the central transverse bending defect of the steel plate; Adjust the plate shape process parameters for the characteristic quantity of the central transverse bending defect of the steel plate: The transverse bending characteristic that appears in the middle of the steel plate is caused by the inappropriate adjustment of the water ratio parameter of the cooling water on the upper and lower surfaces of the roller quenching machine, resulting in asynchronous cooling rates of the upper and lower surfaces in the thickness direction during the cooling process of the steel plate, so that transverse bending appears on the side with a faster cooling rate; The adjustment method is to adjust the water ratio of the cooling water on the upper and lower surfaces; If the characteristic quantity w of the central transverse bending is positive, that is, the upper surface of the steel plate has transverse bending, it indicates that the cooling rate of the upper surface is large and the cooling rate of the lower surface is small. Therefore, it is necessary to increase the original water ratio b of the lower surface cooling water; Through actual production, the function relationship between the water ratio adjustment improvement utility value a and the steel plate thickness d is obtained: a = 0.002d - 0.011; The practical significance of a is that for a steel plate with a thickness of d mm, to improve the transverse bending defect amount of 1 mm, it is necessary to adjust the cooling water ratio by an amplitude of a; Therefore, here it is necessary to adjust the cooling water ratio by an amplitude of a×w, and the adjusted cooling water ratio is b+(0.002d - 0.011)×w; (5) Adjust the plate shape process parameters for the deformation difference amount of the head and tail defects; Adjust the plate shape process parameters for the deformation difference amount of the head and tail defects: The deformation difference amount at the head and tail of the steel plate is mainly caused by the difference in the cooling temperature at the head and tail of the steel plate; The temperature of the steel plate is higher at the head during cooling, while the temperature at the tail is significantly lower due to heat dissipation as the steel plate moves along the roller conveyor. Therefore, by adjusting the original moving speed v of the steel plate, for steel plates with a thickness of less than 12mm, the speed cannot exceed V m / s to ensure hardenability. Actual production results show that the improvement effect of adjusting the roller conveyor moving speed is e = 0.015m. -1 ·s -1 ·mm -1 To improve the flatness difference by 1mm, the running speed of the roller conveyor needs to be increased by 0.015m / s. Therefore, the steel plate moving speed after adjustment is v+e×△h. (6) Measure, calculate, and determine the flatness characteristics of the plate shape after debugging; Based on the defect characteristic values calculated in step (6), conduct plate shape standard determination. The limit standard for the central transverse bending defect is W, and the limit standard for the head - tail deformation difference is Y: 1) If |w| < W and |Δh| < Y, it is determined that the plate shape meets the standard and the turtle - back defect is well improved. Thus, the control of the turtle - back plate shape defect is completed; 2) If the parameter situation does not meet the determination condition 1), it is determined that the plate shape does not meet the standard, and return to the defect characteristic determination in step (3) to conduct a new round of process parameter debugging process; Thus, the design of the control method for improving the turtle - back plate shape defect after quenching of the GPa - grade martensitic wear - resistant steel is completed.

2. The method for controlling the tortoise-shell plate-like defect in quenched martensitic wear-resistant steel according to claim 1, characterized in that: Based on the defect characteristic values calculated in step (2), conduct defect characteristic determination: 1) If the transverse bending characteristic w in the middle, and the combined deformation amplitude Δh of the head and tail of the steel plate. 头 and Δh 尾 If the head-to-tail deformation difference Δh is positive, then the plate shape defect can be determined to be a positive turtleback. 2) If the mid-section transverse bending characteristic w, and the combined deformation amplitude Δh of the steel plate head and tail, 头 and Δh 尾 Furthermore, since the head-to-tail deformation difference Δh is negative, the plate shape defect can be determined to be a reverse turtle back. 3) Other situations are non - turtle - back defects, and other plate shape control methods are used for regulation.

3. The method for controlling the tortoise-shell pattern defect after quenching of Gipa-grade martensitic wear-resistant steel according to claim 1, characterized in that: After completing the process parameter setting, measure the flatness of the plate shape of the newly - produced steel plate again.

4. The method for controlling the tortoise-shell plate-like defect in quenched martensitic wear-resistant steel according to claim 1, characterized in that: After measuring the plate shape of the newly - produced steel plate, calculate the plate shape defect characteristics based on the recorded plate shape data of the newly - produced steel plate.

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