Method for judging cold-rolled strip breakage and edge cracks based on mechanical properties of strip steel

Abstract

The invention discloses a method for judging cold-rolled strip breakage and edge cracks based on strip steel mechanical properties. The method for judging the cold-rolled strip breakage and the edge crack based on the mechanical property of the strip steel comprises the step of judging whether the strip breakage and the edge crack occur or not during cold rolling of the strip steel on the basis of fully considering the yield strength, the tensile strength and the elongation of the strip steel. According to the method, the cold rolling strip breakage and edge crack defects of the strip steel can be effectively reduced, the rolling strip breakage and edge crack defects of the continuous cold rolling mill can be effectively prevented, the product quality is improved, the production faults are reduced, and the production efficiency of the cold rolling mill is improved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip. Background Art

[0002] The single-stand reversible rolling mill is an important production line in the cold rolling process, which mainly cold-rolls the strip to the target thickness. The production line is mainly composed of uncoiler, rolling mill, coiler, pinch roller, edge alignment device, coil loading and unloading trolley and other equipment. During the operation of the unit, edge cracks or strip breaks may occur due to cold rolling, resulting in strip breakage and shutdown accidents. Therefore, it is expected and needed in this field to determine the occurrence of cold-rolled edge cracks or strip breaks before rolling, and take corresponding measures to reduce production accidents and the occurrence of edge cracks. Summary of the invention

[0003] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip.

[0004] The present invention solves the technical problem by adopting the following technical solutions.

[0005] The present invention provides a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip, which comprises: determining whether the strip breakage and edge cracks occur during cold rolling of the strip on the basis of fully considering the yield strength, tensile strength and elongation of the strip.

[0006] The present invention has the following beneficial effects:

[0007] The present invention provides a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip. The method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip provided by the present invention includes: determining whether the strip breakage and edge cracks occur during cold rolling of the strip on the basis of fully considering the yield strength, tensile strength and elongation of the strip. The method is to effectively reduce the occurrence of cold-rolled strip breakage and edge crack defects of the strip. Through this method, the occurrence of rolling strip breakage and edge crack defects of the cold rolling mill can be effectively prevented, product quality can be improved, production failures can be reduced, and the production efficiency of the cold rolling mill can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0009] Figure 1This is a schematic diagram of the force on the strip during cold rolling;

[0010] Figure 2 Flow chart for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of strip steel. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out under normal conditions. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0012] The following is a detailed description of a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip provided by an embodiment of the present invention.

[0013] The purpose of the present invention is to provide a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip, especially for brittle steel with high strength and poor elongation, aiming to prevent cold-rolled edge crack defects and strip breakage failures, improve product quality, and ensure smooth production.

[0014] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0015] The present invention provides a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip, which comprises: determining whether the strip breakage and edge cracks occur during cold rolling of the strip on the basis of fully considering the yield strength, tensile strength and elongation of the strip.

[0016] Through research, it is found that when the cold-rolled raw material has good elongation and low strength, edge cracks or strip breaks basically do not occur. When the cold-rolled raw material has poor elongation and high strength, it is easy to cause edge cracks or strip breakage during the cold rolling process, which seriously affects product quality and production efficiency. In order to reduce the probability of strip breakage and edge cracks in brittle steel (i.e., steel with poor raw material elongation), the inventor has proposed a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of strip steel after long-term practice. On the basis of fully considering the yield strength, tensile strength and elongation of the strip steel, it is determined whether the strip steel will break or have edge cracks during cold rolling.

[0017] See also Figure 1 Through analysis, it can be known that the force of rolling force acting on the rolled piece can be divided into two parts, one is the compressive stress applied by the roller to the rolled piece along the normal direction of the rolled piece, and the other is the tensile stress along the direction of the rolled piece. When the compressive stress is greater than the yield strength of the rolled piece, the strip only undergoes plastic deformation. When the tensile stress is greater than the tensile strength of the rolled piece, the rolled piece begins to contract in the width direction. At this time, if the strip elongation is good, only crack defects will appear on the edge. If the strip elongation is poor, the strip will break.

[0018] Therefore, the solution provided by the embodiment of the present invention determines the cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip. The specific steps are as follows: Figure 2 :

[0019] The future strip steel is subjected to room temperature tensile test to measure the strip steel yield strength σ q , strip tensile strength σ p , strip elongation ε.

[0020] Obtain the cold rolling friction coefficient μ, the roller radius R, the strip entrance thickness hr and the strip exit thickness hc, the strip cold rolling reduction Δh, and Δh=hr-hc.

[0021] According to the cold rolling theory, the compressive stress σ along the normal direction during cold rolling of the strip is obtained. z :σ z =1.28σ q ; Construct the horizontal stress σ during cold rolling of the strip i The determination equation is:

[0022]

[0023] According to the principle of volume invariance, the determination equation of the strip elongation δ during cold rolling is constructed:

[0024]

[0025] Judgment method: When the strip elongation ε is less than the strip cold rolling deformation elongation δ, and the cold rolling horizontal stress σ i >Strip steel tensile strengthσ p When , it is judged as a broken belt;

[0026] When the strip elongation ε<strip cold rolling deformation elongation δ, and the strip yield strength σ q <Cold rolling horizontal stressσ i <Strip steel tensile strengthσ p When the strip is cracked, it is determined that there is a crack on the edge of the strip;

[0027] When the strip elongation ε is less than the strip cold rolling deformation elongation δ, and the cold rolling horizontal stress σ i <Strip yield strengthσ q When the strip is tested, it is determined that there are no edge cracks or strip breaks;

[0028] When the strip elongation ε> the strip cold rolling deformation elongation δ, it is determined that the strip has no edge cracks and no strip breakage.

[0029] It is worth mentioning that, again, Figure 1The bite angle α refers to the central angle formed by the point where the roll and the workpiece first contact when the workpiece begins to roll into the roll, the connecting line in the roll, and the axis line of the upper and lower rolls. After calculation,

[0030] As can be seen from the above, the embodiment of the present invention proposes a simple and convenient method for determining whether the strip has broken strips and edge cracks during the cold rolling process. Based on the analysis of the rolling principle, the present invention establishes the relationship between mechanical properties and broken strips, and uses the quantitative relationship between the yield strength, tensile strength, and elongation of the strip and the horizontal stress and rolling deformation elongation of the cold rolling strip to accurately determine the situation of cold-rolled strip breakage and edge cracks of the strip through the elongation, yield strength, and tensile strength of the strip.

[0031] The method is to effectively prevent the occurrence of strip breakage and edge crack defects in cold-rolled brittle steel. The method can effectively prevent the occurrence of strip breakage and edge crack defects in cold rolling mills, improve product quality, reduce production failures and improve the production efficiency of cold rolling mills.

[0032] To achieve the above object, the present invention provides the following technical solutions:

[0033] Example 1

[0034] The incoming strip steel with a thickness of 2.3 mm was processed into a specimen with a gauge length of 50 mm and a width of 12.5 mm using a rectangular cross-section non-proportional specimen according to GBT 228.1-2010 "Tensile test of metallic materials Part 1: Test method at room temperature" to measure the yield strength σ of the strip steel. q =409.1MPa, strip tensile strengthσ p =521.6MPa, elongation ε=28.5%.

[0035] The cold rolling friction coefficient μ=0.12, the roller radius R=100 mm, the strip entrance thickness 2.3 mm and the exit thickness 1.5 mm were obtained.

[0036] Calculate the cold rolling horizontal stress σ by following formula 1 i : Calculate σ i =357.6MPa

[0037] The cold rolling elongation δ is calculated according to formula 2: Calculated δ = 53.3%

[0038] According to the strip elongation ε=28.5%<strip cold rolling deformation elongation δ=53.3%, horizontal stress σ i =357.6MPa<strip steel yield strengthσ q=409.1MPa, according to the judgment principle: the strip steel has no edge cracks or broken strips.

[0039] Example 2

[0040] The incoming strip steel with a thickness of 1.9 mm was processed into a specimen with a gauge length of 50 mm and a width of 12.5 mm using a rectangular cross-section non-proportional specimen according to GBT 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method" to measure the yield strength σ of the strip steel. q =609.1MPa, strip steel tensile strengthσ p =723.7MPa, elongation ε=15.5%.

[0041] The cold rolling friction coefficient μ=0.12, the roller radius R=100 mm, the strip entrance thickness 1.9 mm and the exit thickness 1.2 mm were obtained.

[0042] Calculate the cold rolling horizontal stress σ by following formula 1 i : Calculate σ i =624.6MPa

[0043] The cold rolling elongation δ is calculated according to formula 2: Calculated δ = 58.3%

[0044] According to the strip elongation ε=15.5%<strip cold rolling deformation elongation δ=58.3%, the strip yield strength σ q =609.1MPa<horizontal stressσ i =624.64MPa<strip steel tensile strengthσ l =723.7MPa, according to the judgment principle: edge cracks appear on the strip.

[0045] Example 3

[0046] The incoming strip steel with a thickness of 1.6 mm was processed into a specimen with a gauge length of 50 mm and a width of 12.5 mm using a rectangular cross-section non-proportional specimen according to GBT 228.1-2010 "Tensile test of metallic materials Part 1: Test method at room temperature" to measure the yield strength σ of the strip steel. q =712.3MPa, strip tensile strengthσ p =731.6MPa, elongation ε=10.3%.

[0047] The cold rolling friction coefficient μ=0.12, the roller radius R=100 mm, the strip entrance thickness 1.6 mm and the exit thickness 1.05 mm were obtained.

[0048] Calculate the cold rolling horizontal stress σ by following formula 1 i : Calculate σ i =743.76MPa

[0049] The cold rolling elongation δ is calculated according to formula 2: Calculated δ = 52.3%

[0050] According to the strip elongation ε=10.3%<strip cold rolling deformation elongation δ=58.3%, horizontal stress σ i =743.76MPa>strip steel tensile strengthσ l =731.6MPa, according to the judgment principle: the strip is broken during cold rolling.

[0051] Example 4

[0052] The incoming strip steel with a thickness of 1.2 mm was processed into a specimen with a gauge length of 50 mm and a width of 12.5 mm using a rectangular cross-section non-proportional specimen according to GBT 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method" to measure the yield strength σ of the strip steel. q =746.8MPa, strip tensile strength σ p =763.2MPa, elongation ε=8.1%.

[0053] The cold rolling friction coefficient μ=0.12, the roller radius R=100 mm, the strip entrance thickness 1.2 mm and the exit thickness 0.8 mm were obtained.

[0054] Calculate the cold rolling horizontal stress σ by following formula 1 i : Calculate σ i =877.8MPa

[0055] The cold rolling elongation δ is calculated according to formula 2: Calculated δ = 53.3%

[0056] According to the strip elongation ε=8.1%<strip cold rolling deformation elongation δ=53.3%, horizontal stress σ i =877.8MPa>strip steel tensile strengthσ l =763.2MPa, according to the judgment principle: the strip is broken during cold rolling.

[0057] Example 5

[0058] The incoming strip steel with a thickness of 1.0 mm was processed into a specimen with a gauge length of 50 mm and a width of 12.5 mm using a rectangular cross-section non-proportional specimen according to GBT 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method" to measure the yield strength σ of the strip steel. q =419.3MPa, strip steel tensile strength σ p =539.2MPa, elongation ε=24.1%.

[0059] The cold rolling friction coefficient μ=0.12, the roller radius R=100 mm, the strip entrance thickness 1.0 mm and the exit thickness 0.68 mm were obtained.

[0060] Calculate the cold rolling horizontal stress σ by following formula 1 i : Calculate σ i =520.4MPa

[0061] The cold rolling elongation δ is calculated according to formula 2: Calculated δ = 47.7%

[0062] According to the strip elongation ε=24.3%<strip cold rolling deformation elongation δ=47.7%, the strip yield strength σ q =419.3MPa<horizontal stressσ i =520.4MPa<strip steel tensile strengthσ l =539.2MPa, according to the judgment principle: edge cracks appear on the strip.

[0063] Example 6

[0064] The incoming strip steel with a thickness of 0.7 mm was processed into a specimen with a gauge length of 50 mm and a width of 12.5 mm using a rectangular cross-section non-proportional specimen according to GBT 228.1-2010 "Tensile test of metallic materials Part 1: Room temperature test method" to measure the yield strength σ of the strip steel. q =397.2MPa, strip tensile strength σ p =553.6MPa, elongation ε=40%.

[0065] The cold rolling friction coefficient μ=0.12, the roller radius R=100 mm, the strip entrance thickness 0.7 mm and the exit thickness 0.5 mm were obtained.

[0066] Calculate the cold rolling horizontal stress σ by following formula 1 i : Calculate σ i =533.4MPa

[0067] The cold rolling elongation δ is calculated according to formula 2: Calculated δ = 40%

[0068] According to the strip elongation ε=24.3%<strip cold rolling deformation elongation δ=40%, the strip yield strength σ q =397.2MPa<horizontal stressσ i =533.4MPa<strip steel tensile strengthσ l =553.6MPa, according to the judgment principle: edge cracks appear on the strip.

[0069] It can be seen from the above embodiments that the embodiment of the present invention provides a method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip, which can determine cold-rolled strip breakage and edge cracks under different conditions, prevent cold-rolled edge crack defects and strip breakage failures, improve product quality, and ensure smooth production.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining cold-rolled strip breakage and edge cracks based on strip mechanical properties, characterized in that: The method includes: determining whether strip breakage and edge cracks occur during cold rolling of the strip on the basis of fully considering the yield strength, tensile strength and elongation of the strip.

2. The method according to claim 1, characterized in that For brittle steel, the method for determining cold-rolled strip breakage and edge cracks based on the mechanical properties of the strip steel includes the following steps: The future strip steel is subjected to room temperature tensile test to measure the strip steel yield strength σ q , strip tensile strength σ p , strip elongation ε; obtain the cold rolling friction coefficient μ, roller radius R, strip inlet thickness hr and strip outlet thickness hc, strip cold rolling reduction Δh, and Δh = hr-hc; According to the cold rolling theory, the compressive stress σ along the normal direction during cold rolling of the strip is obtained. z :σ z =1.28σ q ; Construct the horizontal stress σ during cold rolling of the strip i The determination equation is: According to the principle of volume invariance, the determination equation of the strip elongation δ during cold rolling is constructed: Judgment method: When the strip elongation ε is less than the strip cold rolling deformation elongation δ, and the cold rolling horizontal stress σ i >Strip steel tensile strengthσ p When , it is judged as a broken belt; When the strip elongation ε<strip cold rolling deformation elongation δ, and the strip yield strength σ q <Cold rolling horizontal stressσ i <Strip steel tensile strengthσ p When the strip is cracked, it is determined that there is a crack on the edge of the strip; When the strip elongation ε is less than the strip cold rolling deformation elongation δ, and the cold rolling horizontal stress σ i <Strip yield strengthσ q When the strip is tested, it is determined that there are no edge cracks or strip breaks; When the strip elongation ε> the strip cold rolling deformation elongation δ, it is determined that the strip has no edge cracks and no strip breakage.

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