Method for analyzing segregation condition of special-shaped casting blank

Abstract

The invention discloses a method for analyzing the segregation condition of a special-shaped casting blank, belongs to the technical field of ferrous metallurgy, and mainly aims at the solidification characteristics of the section of the special-shaped casting blank and the condition that the solidification structure of the casting blank is complex, the sampling positions of a fine grain area, a columnar crystal area and an equiaxed crystal area on the surface of the cross section of the casting blank are designed; after sample drilling, the chemical composition condition of each point is analyzed by adopting a chemical method, the segregation condition of the special-shaped casting blank is analyzed, a technical reference is provided for evaluating the internal quality of the special-shaped casting blank, and meanwhile, basic theoretical data is provided for the rolling process of the special-shaped casting blank.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for analyzing segregation of special-shaped castings. Background Art

[0002] Defect-free billet production is the desired goal of continuous casting steel mills. However, due to the limitations of production conditions and other factors, it is actually difficult to achieve completely defect-free billet continuous casting. To ensure the quality of rolled products, the surface of defective billets must be cleaned, which increases the stacking space and labor workload of billets and increases production costs. Therefore, understanding the causes of surface defects of continuous casting billets and their evolution during the rolling process, and rationally adjusting and optimizing the process are of great practical significance for reducing the amount of billet cleaning, optimizing the process flow, and improving production efficiency.

[0003] Due to the complex cross-section of the special-shaped billet, the heat dissipation conditions at each point on the cross-section are quite different. The web is a one-dimensional heat transfer, and the top of the flange is a two-dimensional heat transfer. The temperature difference at each point on the cross-section is large. With the formation of the primary billet shell, the conduction of heat to the wall of the crystallizer is slowed down, and the temperature difference inside and outside the billet shell promotes the incubation and growth of columnar crystals. Due to the large specific surface area of ​​the special-shaped billet and the relatively thin thickness of the flange and web, the temperature gradient inside and outside the billet shell is increased, which further aggravates the development of columnar crystals. Compared with conventional square and round billets, columnar crystals are more developed. Due to the dendrite bridging, the shrinkage compensation at the end of solidification is insufficient, which affects the flow of the enriched elements that have not yet solidified at the end of solidification, resulting in the segregation of the billet. Therefore, according to the solidification characteristics of the cross-section of the special-shaped billet and the complex solidification structure of the billet, the sampling positions of the fine grain area, columnar grain area and equiaxed grain area on the cross-section surface of the billet are designed. After drilling the sample, the chemical composition of each point is analyzed by chemical method, and the segregation of the special-shaped billet is analyzed, so as to provide technical reference for evaluating the internal quality of the special-shaped billet and provide basic theoretical data for the rolling process of the special-shaped billet.

[0004] Chinese patent application number 202211375602.6 discloses a method for evaluating carbon segregation of a billet, comprising sawing a cross section or a longitudinal section of the billet to take a sample, milling and grinding the surface to be inspected to obtain a smooth and clean sample surface; performing surface dendrite erosion on the cross-section or longitudinal section of the billet sample surface; cleaning and drying the eroded surface of the billet; performing a planar scanning of the dendrite erosion surface of the billet by a scanner to obtain a uniform dendrite structure image of the billet; performing grayscale identification on the billet area by using image processing software; obtaining the apparent density of the defective area and comparing it with a set critical value, and eliminating the area less than the critical value; obtaining a grayscale matrix by using Mat l ab software, and converting it into a carbon content matrix; obtaining a segregation contour distribution map and index value according to the carbon content matrix by using Mat l ab software.

[0005] Chinese patent application number 201210236416.4 discloses a method for drilling sampling of component segregation of ingots, the sampling method comprising the following steps: marking the center line and two diagonals of the sample along the width direction; dividing the sample into n-1 equal parts along the two edges of the sample in the length direction and the center line in the width direction respectively; dividing the sample into n-1 equal parts along the two diagonals of the sample; using a drill bit to drill chip samples at the marked sampling points, and marking and collecting them, wherein n is an odd number, and n≥5.

[0006] The Chinese patent application number 202210590872.2 discloses a method for controlling the center segregation of a casting billet, which is particularly suitable for controlling the center segregation of a marine corrosion-resistant steel bar casting billet. The control method includes a secondary cooling process and a light reduction process in continuous casting, wherein the secondary cooling process adopts weak cooling, and the specific water volume is 0.4L / kg-1.2L / kg; the solid phase ratio in the reduction interval of the light reduction process is 0.3-0.8, and the reduction amount is 8mm-14mm. The control method can significantly reduce the segregation of sulfur and manganese elements in the casting billet, and through inspection, the center segregation level reaches level 1.0, and the center segregation index is less than 1.10. Summary of the invention

[0007] The purpose of the present invention is to provide a method for analyzing the segregation of special-shaped billets. In view of the technical problems in the background, according to the characteristics of the cross-section of the special-shaped billet, the sampling positions of the cross-section of the billet are designed, and the chemical composition of each point is analyzed by chemical method after drilling the sample, and the segregation results at different positions are calculated, so as to provide a technical reference for evaluating the internal quality of the special-shaped billet and solve the above-mentioned problems.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for analyzing segregation of special-shaped castings, comprising:

[0010] 1) Analyze the segregation of the special-shaped billet with a cross section of 555×440×105mm;

[0011] 2) According to the characteristics of the 555×440×105mm section of the special-shaped billet, the sampling positions of the fine grain area, columnar grain area and equiaxed grain area on the surface of the billet cross section are designed. Due to the symmetry of the billet on the left and right sides, the segregation conditions of the inner arc, outer arc, web and flange at different positions of the special-shaped billet are comprehensively analyzed to design the sampling positions of the billet cross section.

[0012] 3) Focus on analyzing the segregation of carbon and manganese elements

[0013] 4) According to the sampling position of the designed cross section of the ingot, a drill is used to drill the sample to remove the surface oxides to ensure that the sample is not contaminated. The sample volume of two elements is taken at each position;

[0014] 5) Use chemical method to analyze the chemical composition of carbon and manganese in each sample;

[0015] 6) According to the chemical composition results of each sample, the segregation index is calculated by the formula. The segregation index of each point of the ingot is the content of the segregation element at the drilled sample position divided by the average content of the segregation element at all drilled sample points of the ingot;

[0016] 7) Comprehensively analyze the segregation of carbon and manganese elements in the cross-section of the special-shaped casting billet 555×440×105mm.

[0017] Furthermore, the test steel type for the special-shaped casting is Q355C.

[0018] Furthermore, a Φ6 mm drill bit was used for drilling samples.

[0019] Furthermore, the maximum segregation point of the special-shaped billet from the inner arc to the outer arc is at 1 / 4, the minimum segregation point is on the billet surface, the maximum segregation point of the web is at the center, the minimum segregation point is close to the center, the segregation index at the flange is relatively small, the carbon segregation of the entire billet is less than 1.05, the manganese segregation is less than 1.02, and the overall internal quality of the special-shaped billet is good.

[0020] Furthermore, the analysis method is simple and effective.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are:

[0022] The invention designs the sampling position of the cross section of the billet according to the characteristics of the cross section of the special-shaped billet, uses a chemical method to analyze the chemical composition of each point after drilling the sample, calculates the segregation results at different positions, analyzes the solidification characteristics and segregation of the special-shaped billet, evaluates the internal quality of the special-shaped billet, and provides a technical reference for formulating the rolling process to reduce the scrap rate. The analysis method is simple and effective, low in cost, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below in conjunction with the accompanying drawings.

[0024] Figure 1 It is the sampling position of the segregation point of the special-shaped casting billet;

[0025] Figure 2 It is the segregation result from inner arc to outer arc of special-shaped casting;

[0026] Figure 3 It is the result of segregation from the edge to the center of the special-shaped billet. DETAILED DESCRIPTION

[0027] Case 1:

[0028] A method for analyzing segregation of a special-shaped casting, comprising:

[0029] 1. Analyze the segregation of special-shaped billet with a cross section of 555×440×105mm.

[0030] 2. According to the characteristics of the 555×440×105mm section of the special-shaped billet, the sampling positions of the fine grain area, columnar grain area, and equiaxed grain area on the surface of the billet cross section are designed. Due to the symmetry of the billet on the left and right, the segregation of the inner arc, outer arc, web, flange and other positions of the special-shaped billet is fully analyzed, and the sampling positions of the billet cross section are designed. The specific sampling positions are as follows: Figure 1 shown.

[0031] 3. The test steel type for special-shaped castings is Q355C, and the segregation of carbon and manganese elements is analyzed in detail.

[0032] 4. According to the designed sampling position of the cross section of the ingot, a Φ6mm drill bit is used to drill the sample to remove the surface oxides to ensure that the sample is not contaminated. The sample quantity of two elements is taken at each position.

[0033] 4. Use chemical methods to analyze the chemical composition of carbon and manganese in each sample.

[0034] 5. According to the chemical composition results of each sample, the segregation index is calculated by the formula. The segregation index of each point of the ingot is the content of the segregation element at the drilled sample position divided by the average content of the segregation element at all drilled sample points of the ingot. Figure 2 It is the segregation result from inner arc to outer arc of special-shaped casting. Figure 3 It is the result of segregation from the edge to the center of the special-shaped billet.

[0035] 6. Comprehensive analysis of the segregation of carbon and manganese elements in the special-shaped billet 555×440×105mm section Q355C. The maximum segregation point from the inner arc to the outer arc of the special-shaped billet is at 1 / 4, the minimum segregation point is at the billet surface, the maximum segregation point of the web is at the center, the minimum segregation point is close to the center, the segregation index at the flange is relatively small, the carbon segregation of the whole billet is less than 1.05, the manganese segregation is less than 1.02, and the overall internal quality of the special-shaped billet is good.

[0036] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for analyzing the segregation of special-shaped castings, characterized in that: include: 1) Analyze the segregation of the special-shaped billet with a cross section of 555×440×105mm; 2) According to the characteristics of the 555×440×105mm section of the special-shaped billet, the sampling positions of the fine grain area, columnar grain area and equiaxed grain area on the surface of the billet cross section are designed. Due to the symmetry of the billet on the left and right sides, the segregation conditions of the inner arc, outer arc, web and flange at different positions of the special-shaped billet are comprehensively analyzed to design the sampling positions of the billet cross section. 3) Focus on analyzing the segregation of carbon and manganese elements 4) According to the sampling position of the designed cross section of the ingot, a drill is used to drill the sample to remove the surface oxides to ensure that the sample is not contaminated. The sample volume of two elements is taken at each position; 5) Use chemical method to analyze the chemical composition of carbon and manganese in each sample; 6) According to the chemical composition results of each sample, the segregation index is calculated by the formula. The segregation index of each point of the ingot is the content of the segregation element at the drilled sample position divided by the average content of the segregation element at all drilled sample points of the ingot; 7) Comprehensively analyze the segregation of carbon and manganese elements in the cross-section of the special-shaped casting billet 555×440×105mm.

2. The method for analyzing segregation of special-shaped castings according to claim 1, characterized in that: The test steel grade for special-shaped castings is Q355C.

3. The method for analyzing segregation of special-shaped castings according to claim 1 or 2, characterized in that: Use a Φ6mm drill bit to drill the sample.

4. The method for analyzing segregation of special-shaped castings according to claim 2, characterized in that: The maximum segregation point of the special-shaped billet from the inner arc to the outer arc is at 1 / 4, the minimum segregation point is on the billet surface, the maximum segregation point of the web is at the center, the minimum segregation point is close to the center, the segregation index at the flange is relatively small, the carbon segregation of the entire billet is less than 1.05, the manganese segregation is less than 1.02, and the overall internal quality of the special-shaped billet is good.

5. The method for analyzing segregation of special-shaped castings according to claim 1, characterized in that: The analytical method is simple and effective.

Images