A method for determining cold-rolling strip breakage and edge crack based on strip mechanical properties

Abstract

The application discloses a method for judging strip breakage and edge crack in cold rolling based on mechanical properties of strip steel. The method provided by the application for judging strip breakage and edge crack in cold rolling based on mechanical properties of strip steel comprises the following steps: on the basis of fully considering the yield strength, tensile strength and elongation of the strip steel, whether the strip breakage and edge crack occur in the cold rolling of the strip steel is judged. The method can effectively reduce the generation of the strip breakage and edge crack defects in the cold rolling of the strip steel, can effectively prevent the occurrence of the strip breakage and edge crack defects in the rolling of the cold continuous rolling mill, can improve the product quality, can reduce the production failure, and can improve the production efficiency of the cold rolling mill.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, in particular to a method for determining cold rolling strip breakage and edge cracks based on strip mechanical properties. BACKGROUND

[0002] Single stand reversing mill is an important production line in the cold rolling process, which mainly cold-rolls the strip to the target thickness. The production line mainly consists of an uncoiler, a rolling mill, a coiler, pinch rolls, an edge alignment device, a loading and unloading trolley and other equipment. The mill is prone to edge cracks or strip breakage during operation, resulting in strip breakage downtime accidents. Therefore, it is desirable and necessary in the field to determine the occurrence of edge cracks or strip breakage before rolling and take corresponding measures to reduce production accidents and the occurrence of edge cracks. SUMMARY

[0003] The present application relates to the technical field of metallurgy, in particular to a method for determining cold rolling strip breakage and edge cracks based on strip mechanical properties.

[0004] The present application solves the technical problem by adopting the following technical solution.

[0005] The present application provides a method for determining cold rolling strip breakage and edge cracks based on strip mechanical properties, which comprises: determining whether strip breakage and edge cracks occur during cold rolling of the strip based on sufficient consideration of the yield strength, tensile strength and elongation of the strip.

[0006] The present application has the following advantages:

[0007] The present application provides a method for determining cold rolling strip breakage and edge cracks based on strip mechanical properties, which comprises: determining whether strip breakage and edge cracks occur during cold rolling of the strip based on sufficient consideration of the yield strength, tensile strength and elongation of the strip. This method effectively reduces the occurrence of cold rolling strip breakage and edge cracks in the strip, prevents the occurrence of rolling strip breakage and edge cracks in the cold continuous rolling mill, improves product quality, reduces production failures and improves the production efficiency of the cold rolling mill. BRIEF DESCRIPTION OF DRAWINGS

[0008] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0009] Figure 1It is a force schematic diagram of the strip steel in cold rolling;

[0010] Figure 2 It is a flow chart for judging the cold rolling strip break and edge crack based on the mechanical properties of the strip steel. DETAILED DESCRIPTION

[0011] To make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely. If the specific conditions are not specified in the embodiments, the conventional conditions are adopted. If the manufacturers of the reagents or instruments are not specified, the conventional products that can be purchased in the market are adopted.

[0012] The method for judging the cold rolling strip break and edge crack based on the mechanical properties of the strip steel provided by the embodiments of the present application will be described in detail.

[0013] The purpose of the present application is to provide a method for judging the cold rolling strip break and edge crack based on the mechanical properties of the strip steel, especially for brittle steel, which has higher strength and poorer elongation, aiming at preventing the edge crack defect and strip break failure in cold rolling, improving the product quality and ensuring the smooth production.

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

[0015] The present application provides a method for judging the cold rolling strip break and edge crack based on the mechanical properties of the strip steel, which comprises: judging whether the strip break and edge crack occur in the cold rolling of the strip steel on the basis of fully considering the yield strength, tensile strength and elongation of the strip steel.

[0016] Through research, it is found that when the elongation of the cold rolling raw material is good and the strength is low, the edge crack or strip break basically does not occur, when the elongation of the cold rolling raw material is poor and the strength is high, the edge crack or strip break easily occurs in the cold rolling process, which seriously affects the product quality and production efficiency. In order to reduce the occurrence probability of the strip break and edge crack of brittle steel (i.e. the steel with poor elongation), the inventors propose a method for judging the cold rolling strip break and edge crack based on the mechanical properties of the strip steel, which judges whether the strip break and edge crack occur in the cold rolling of the strip steel on the basis of fully considering the yield strength, tensile strength and elongation of the strip steel.

[0017] Referring to Figure 1 Through analysis, it is known that the force of the rolling force acting on the rolled piece can be divided into two parts, one part is the pressure stress applied by the roller to the rolled piece along the normal direction of the rolled piece, and the other part is the tensile stress along the direction of the rolled piece. When the pressure stress > the yield strength of the rolled piece, the strip steel only produces plastic deformation. When the tensile stress > the tensile strength of the rolled piece, the width direction of the rolled piece begins to shrink. At this time, if the elongation of the strip steel is good, only the edge crack defect will occur, and if the elongation of the strip steel is poor, the strip steel will break.

[0018] Therefore, the scheme provided by the embodiment of the present application determines the cold rolling strip breakage and edge crack on the basis of the mechanical properties of the strip steel, and the specific steps are as follows, see Figure 2 :

[0019] The raw strip steel is subjected to a room temperature tensile test, and the yield strength σ q , the tensile strength σ p and the elongation of the strip steel ε are measured.

[0020] The cold rolling friction coefficient μ, the roll radius R, the strip steel inlet thickness hr and the strip steel outlet thickness hc, the strip steel cold rolling reduction amount Δh, and Δh = hr-hc are obtained.

[0021] According to the cold rolling theory, the normal direction compression stress σ z of the strip steel during cold rolling is obtained: σ z = 1.28σ q , and a determination equation of the horizontal direction stress σ i of the strip steel during cold rolling is constructed.

[0022]

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

[0024]

[0025] The determination method is as follows: when the strip steel elongation ε is less than the cold rolling deformation elongation δ of the strip steel, and the cold rolling horizontal direction stress σ i is greater than the tensile strength σ p of the strip steel, it is determined that the strip steel is broken;

[0026] When the strip steel elongation ε is less than the cold rolling deformation elongation δ of the strip steel, and the strip steel yield strength σ q is less than the cold rolling horizontal direction stress σ i , and the tensile strength σ p of the strip steel, it is determined that the edge of the strip steel appears a crack;

[0027] When the strip steel elongation ε is less than the cold rolling deformation elongation δ of the strip steel, and the cold rolling horizontal direction stress σ i is less than the strip steel yield strength σ q , it is determined that the edge of the strip steel does not appear a crack and the strip steel is not broken;

[0028] When the strip steel elongation ε is greater than the cold rolling deformation elongation δ of the strip steel, it is determined that the edge of the strip steel does not appear a crack and the strip steel is not broken.

[0029] It is worth mentioning that, again referring to Figure 1The bite angle a refers to a central angle formed by a line connecting a point where the rolled piece starts to roll into the roll and the roll center and the upper and lower roll center lines when the roll and the rolled piece first contact each other.

[0030] It can be seen that the embodiment of the present application provides a simple and convenient method for determining whether the strip appears to be broken or the edge cracks in the cold rolling process. Based on the rolling principle analysis, the present application establishes the relationship between the mechanical properties and the broken strip, and uses the quantitative relationship between the yield strength, tensile strength, elongation of the strip, the horizontal stress of the cold rolling and the elongation of the rolling deformation, and accurately determines the cold rolling broken strip and the edge crack of the strip through the elongation, yield strength and tensile strength of the strip.

[0031] The method can effectively prevent the occurrence of the broken strip and the edge crack defects of the cold rolling mill, improve the product quality, reduce the production failure and improve the production efficiency of the cold rolling mill.

[0032] To achieve the above object, the present application provides the following technical scheme:

[0033] Example 1

[0034] The strip with a thickness of 2.3mm is processed into a sample with a gauge of 50mm and a width of 12.5mm according to GBT 228.1-2010 'Metallic Materials Tensile Test Part 1: Room Temperature Test Method' using a rectangular cross-section non-proportional sample, and the yield strength σ q of the strip is measured as 409.1MPa, the tensile strength σ p of the strip is measured as 521.6MPa, and the elongation ε is measured as 28.5%.

[0035] The cold rolling friction coefficient μ is 0.12, the roll radius R is 100mm, the strip inlet thickness is 2.3mm, and the outlet thickness is 1.5mm.

[0036] The cold rolling horizontal stress σ i is calculated according to the following formula 1: The σ i is calculated as 357.6MPa

[0037] The cold rolling elongation δ is calculated according to the following formula 2: The δ is calculated as 53.3%

[0038] According to the elongation ε of the strip, i.e. 28.5% < the elongation δ of the strip cold rolling deformation, i.e. 53.3%, the horizontal stress σ i is 357.6MPa < the yield strength σ q of the strip is 409.1MPa, and according to the determination principle, the strip does not appear to be broken or cracked.

[0039] Example 2

[0040] The strip steel with a thickness of 1.9 mm is processed into a sample with a gauge length of 50 mm and a width of 12.5 mm according to GBT 228.1-2010 "Metallic Materials Tensile Testing Part 1: Room Temperature Testing Methods" using a rectangular cross-section non-proportional sample, and the yield strength σ q = 609.1 MPa, the tensile strength σ p = 723.7 MPa, and the elongation ε = 15.5% of the strip steel are measured.

[0041] The cold rolling friction coefficient μ = 0.12, the roll radius R = 100 mm, the strip steel inlet thickness 1.9 mm, and the outlet thickness 1.2 mm are obtained.

[0042] The cold rolling horizontal stress σ i is calculated according to the following formula 1: The calculation result is σ i = 624.6 MPa

[0043] The cold rolling elongation δ is calculated according to the following formula 2: The calculation result is δ = 58.3%

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

[0045] Example 3

[0046] The strip steel with a thickness of 1.6 mm is processed into a sample with a gauge length of 50 mm and a width of 12.5 mm according to GBT 228.1-2010 "Metallic Materials Tensile Testing Part 1: Room Temperature Testing Methods" using a rectangular cross-section non-proportional sample, and the yield strength σ q = 712.3 MPa, the tensile strength σ p = 731.6 MPa, and the elongation ε = 10.3% of the strip steel are measured.

[0047] The cold rolling friction coefficient μ = 0.12, the roll radius R = 100 mm, the strip steel inlet thickness 1.6 mm, and the outlet thickness 1.05 mm are obtained.

[0048] The cold rolling horizontal stress σ i is calculated according to the following formula 1: The calculation result is σ i = 743.76 MPa

[0049] The cold rolling elongation δ is calculated according to the following formula 2: The calculation result is δ = 52.3%

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

[0051] Example 4

[0052] The strip steel with a thickness of 1.2 mm is processed into a sample with a gauge length of 50 mm and a width of 12.5 mm by using a rectangular cross-section non-proportional sample according to GBT 228.1-2010 "Metallic Materials Tensile Testing Part 1: Room Temperature Testing Methods", and the yield strength σ q = 746.8 MPa, the tensile strength σ p = 763.2 MPa, and the elongation ε = 8.1% of the strip steel are measured.

[0053] The cold rolling friction coefficient μ = 0.12, the roll radius R = 100 mm, the strip steel inlet thickness 1.2 mm, and the outlet thickness 0.8 mm are obtained.

[0054] The cold rolling horizontal stress σ i is calculated according to the following formula 1: The calculation result is σ i = 877.8 MPa

[0055] The cold rolling elongation δ is calculated according to the following formula 2: The calculation result is δ = 53.3%

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

[0057] Example 5

[0058] The strip steel with a thickness of 1.0 mm is processed into a sample with a gauge length of 50 mm and a width of 12.5 mm by using a rectangular cross-section non-proportional sample according to GBT 228.1-2010 "Metallic Materials Tensile Testing Part 1: Room Temperature Testing Methods", and the yield strength σ q = 419.3 MPa, the tensile strength σ p = 539.2 MPa, and the elongation ε = 24.1% of the strip steel are measured.

[0059] The cold rolling friction coefficient μ = 0.12, the roll radius R = 100 mm, the strip steel inlet thickness 1.0 mm and the outlet thickness 0.68 mm are obtained.

[0060] The cold rolling horizontal stress σ is calculated according to the following formula 1 i : The σ is calculated to be 520.4 MPa i

[0061] The cold rolling elongation δ is calculated according to the following formula 2: The δ is calculated to be 47.7%

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

[0063] Example 6

[0064] The strip steel with a thickness of 0.7 mm is processed into a sample with a gauge length of 50 mm and a width of 12.5 mm according to GBT 228.1-2010 "Metallic Materials Tensile Test Part 1: Room Temperature Test Method" using a rectangular cross-section non-proportional sample. The strip steel yield strength σ q = 397.2 MPa, the strip steel tensile strength σ p = 553.6 MPa, and the elongation ε = 40%.

[0065] The cold rolling friction coefficient μ = 0.12, the roll radius R = 100 mm, the strip steel inlet thickness 0.7 mm and the outlet thickness 0.5 mm are obtained.

[0066] The cold rolling horizontal stress σ is calculated according to the following formula 1 i : The σ is calculated to be 533.4 MPa i

[0067] The cold rolling elongation δ is calculated according to the following formula 2: The δ is calculated to be 40%

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

[0069] From the above embodiments can be seen: adopt the embodiment of the present application provides a kind of based on strip steel mechanical property determination cold rolling strip break and edge crack method, can judge the cold rolling strip break and edge crack under different conditions, can prevent the edge crack defect of cold rolling and the break fault of occurrence, improve product quality, guarantee the smooth progress of production.

[0070] The above only for the preferred embodiments of the present application, and is not used to limit the present application, for the person skilled in the art, the present application can have various changes and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for determining cold-rolled strip fracture and edge cracks based on the mechanical properties of strip steel, characterized in that, Includes the following steps: The strip steel was subjected to a room temperature tensile test to determine its yield strength. Tensile strength of strip steel strip elongation ; Obtain the cold rolling friction coefficient μ, roll radius R, strip inlet thickness hr and strip outlet thickness hc, and strip cold rolling reduction Δh, where Δh = hr - hc; The compressive stress along the normal direction during cold rolling of strip steel is obtained based on cold rolling theory. : =1.28 ; Constructing horizontal stress during cold rolling of strip steel The determination equation: (1) The elongation of strip during cold rolling is constructed based on the principle of constant volume. The determination equation: (2)； Judgment method: When the strip elongation <Extension of cold-rolled strip And cold rolling horizontal stress >Tensile strength of strip steel At that time, it was determined to be a broken band; When the strip elongation <Extension of cold-rolled strip And the yield strength of the strip steel Cold rolling horizontal stress <Tensile strength of strip steel At that time, it was determined that a crack had appeared on the edge of the strip steel; When the strip elongation <Extension of cold-rolled strip And cold rolling horizontal stress <Strip yield strength At that time, it was determined that the strip steel did not have edge cracks or breakage; When the strip elongation >Extension of cold-rolled strip At that time, it is determined that the strip does not have edge cracks or breakage.

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