Method for manufacturing artificial defects in a cast strand, artificial defect rail and method for analyzing defects

Abstract

The application discloses a kind of casting blank artificial defect manufacturing method, artificial defect rail and defect analysis method, by preparing the casting blank with artificial hole slot defect, and the surface defect of the rail product produced by the casting blank is compared and analyzed with the artificial defect on the surface of casting blank, to determine the surface defect inheritance relationship of artificial defect rail and the casting blank with artificial defect, and using the inheritance relationship successfully trace the defect on rail back to casting blank, to help technical personnel quickly and accurately locate the defect position on casting blank, estimate the defect size on casting blank, and select appropriate defect coping strategy, effectively improve the yield of rolled product.In addition, it is verified that the rolling extension coefficient of rail is basically consistent with the existing theory, and the depth-width ratio standard of casting blank surface defect morphology forming excessive defect on rail surface is also determined, and by using the standard before rail rolling, increasing the defect inspection intensity of casting blank, can further effectively avoid the generation of unqualified products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rail rolling defect analysis, and particularly relates to a cast blank artificial defect manufacturing method, an artificial defect rail and a defect analysis method. BACKGROUND

[0002] With the increase of railway passenger and freight traffic and the continuous improvement of train speed, the requirements for the surface and internal quality of rails are also higher and higher. The main forms of rail surface defects are scabbing, folding, rolling marks, pressed-in iron oxide scale, straightening marks, scratches and cracks. In particular, when a rail has a deep crack, the material damage and stress change caused by the rolling contact of the wheel and rail make the crack worse, so that the crack continuously expands and extends longitudinally and transversely, which not only affects the stability of driving, but also may cause rail breaking and serious accidents in severe cases.

[0003] The generation of cracks is extremely complex, some of which are evolved from cast blank defects, and some of which are generated in the intermediate rolling process, and the occasionality is strong, which brings great difficulty to the source tracing. The cast blank defects mainly include scratches, slag inclusion, pits and scabbing, which all have an impact on the surface quality of the rail product. However, most of the crack defects on the surface of the rail product are derived from the original defects on the cast blank. However, the biggest challenge at present is the lack of clear judgment and inspection of whether these original defects of the cast blank will be reflected on the finished product and how to reflect the judgment basis, so it is not convenient to quickly select the appropriate treatment measures. In the actual production process, technical personnel can only rely on observation of the surface of the finished product to try to guess the possible cause of the defect, which may be an initial casting defect or a blank defect before rolling. Some even make corresponding judgments and measures without detecting and analyzing the finished product defects and the cast blank. However, this treatment method is difficult to accurately determine and requires years of experience in dealing with the relationship between rolling defects and continuous casting defects. Therefore, at the present stage, some measures taken when the surface defect of the rail product is encountered are not appropriate, so it is urgent to thoroughly study the problems such as the extent to which the cast blank defect will be presented on the surface of the rolled rail, the clear corresponding relationship between the structure of the cast blank surface defect and the structure of the finished product surface defect, and the relative positional relationship when the finished product defect of the rail is traced back to the cast blank, so as to ensure that the technical personnel can quickly and accurately select the appropriate treatment measures and effectively improve the yield of the rolled rail. SUMMARY

[0004] The purpose of the present application is to design an artificial defect structure of a cast blank, and to use the structure to test and study the inheritance relationship between the surface defects of the cast blank and the finished product of the rail, successfully deduce the evolution law, thereby providing effective guidance for quickly selecting appropriate rail defect treatment measures, providing scientific traceability basis for the defect control of the finished product surface of the rail and the defect finding in the later rolling stage, and the method also has great popularization value in the production defect research of other profiles.

[0005] To achieve the above object, the present application provides the following technical solutions.

[0006] A method for manufacturing artificial defects in a casting blank, the method comprising,

[0007] Drilling a plurality of holes perpendicular to the surface of the casting blank in the rolling slip area and the rolling stable area of the surface of the casting blank without exceeding defects; the casting blank without exceeding defects includes a casting blank with a flat, smooth, pit-free, slag-free, vibration mark-free, and crack-free surface;

[0008] Filling the holes with refractory material and plugging them to prevent oxidation and bonding of the holes during rolling; thus, a casting blank with artificial defects is obtained.

[0009] As a further improvement of the present application, the plurality of holes in the rolling stable area are distributed on the full section of the middle part of the casting blank and are arranged in a staggered manner.

[0010] The plurality of holes in the rolling slip area are distributed on at least one section of the end of the casting blank.

[0011] The plurality of holes distributed on any section of the middle and end of the casting blank are arranged in a straight line; the straight line is perpendicular to the length direction of the section where the straight line is located, and the spacing between the plurality of holes on the same straight line is set to 50-200mm.

[0012] As a further improvement of the present application, the plurality of straight lines are not connected at the beginning and end and have a staggered spacing of ≥100mm.

[0013] As a further improvement of the present application, the depth of the holes is set to 10-50mm.

[0014] As a further improvement of the present application, the hole diameter of the holes is set to 5-30mm.

[0015] The present application also provides an artificial defect steel rail manufactured according to the aforementioned method for manufacturing artificial defects in a casting blank, the artificial defect steel rail being rolled from the casting blank with artificial defects.

[0016] The present application also provides a method for analyzing defects in a steel rail using the aforementioned artificial defect steel rail, the method comprising,

[0017] Comparatively analyzing the surface structure of the artificial defect steel rail and the casting blank with artificial defects to determine the surface defect inheritance relationship between the artificial defect steel rail and the casting blank with artificial defects.

[0018] Using the surface defect inheritance relationship between the artificial defect steel rail and the casting blank with artificial defects to analyze defects in the steel rail.

[0019] As a further improvement of the present application, the surface defect inheritance relationship of the artificial defect steel rail and the casting billet with artificial defects includes:

[0020] The first correspondence relationship between the surface defect position of the casting billet with artificial defects and the surface defect position of the artificial defect steel rail; the first correspondence relationship includes:

[0021] The first hole groove defect located at the end of the casting billet corresponds to the defect at the waist of the finished rail of the steel rail;

[0022] The second hole groove defect located at the middle of the casting billet corresponds to the defect at the waist of the finished rail of the steel rail;

[0023] The third hole groove defect located at the middle of the casting billet corresponds to the defect at the bottom of the finished rail of the steel rail;

[0024] The fourth hole groove defect located at the middle of the casting billet corresponds to the defect at the head of the finished rail of the steel rail;

[0025] The fifth hole groove defect located at the middle of the casting billet corresponds to the defect at the lower waist of the finished rail of the steel rail;

[0026] The second correspondence relationship between the surface defect position of the casting billet with artificial defects and the surface defect morphology of the artificial defect steel rail; the second correspondence relationship includes:

[0027] The fourth hole groove defect at the middle of the casting billet forms a deep and regular line defect at the head of the artificial defect steel rail;

[0028] The first hole groove defect at the end of the casting billet and the second hole groove defect at the middle of the casting billet form irregular nodular scab defects and / or strip scab defects at the upper waist of the artificial defect steel rail;

[0029] The fifth hole groove defect at the middle of the casting billet forms a line defect with a relatively shallow depth at the lower waist of the artificial defect steel rail;

[0030] The third hole groove defect at the middle of the casting billet forms a line defect at the bottom of the artificial defect steel rail;

[0031] The third correspondence relationship between the surface defect depth of the casting billet with artificial defects and the surface defect depth of the artificial defect steel rail; the third correspondence relationship includes:

[0032] The average compression ratio of the first hole groove defect depth at the end of the casting billet to the surface line defect depth of the steel rail is 18.18;

[0033] The average compression ratio of the second hole groove defect depth at the middle of the casting billet to the surface line defect depth of the steel rail is 17.39;

[0034] The average compression ratio of the first hole defect depth in the middle of the casting blank corresponding to the surface line defect depth of the rail is 15.625;

[0035] The average compression ratio of the first hole defect depth in the middle of the casting blank corresponding to the surface line defect depth of the rail is 15.87;

[0036] The average compression ratio of the first hole defect depth in the middle of the casting blank corresponding to the surface line defect depth of the rail is 20.339;

[0037] The fourth corresponding relationship of the surface defect aperture of the casting blank with artificial defects and the surface defect length of the rail with artificial defects, the fourth corresponding relationship comprising:

[0038] The average extension coefficient of the first hole defect aperture in the end of the casting blank corresponding to the surface line defect length of the rail is 17.077;

[0039] The average extension coefficient of the second hole defect aperture in the middle of the casting blank corresponding to the surface line defect length of the rail is 16.21;

[0040] The average extension coefficient of the third hole defect aperture in the middle of the casting blank corresponding to the surface line defect length of the rail is 14.342;

[0041] The average extension coefficient of the fourth hole defect aperture in the middle of the casting blank corresponding to the surface line defect length of the rail is 14.18;

[0042] The average extension coefficient of the fifth hole defect aperture in the middle of the casting blank corresponding to the surface line defect length of the rail is 13.371.

[0043] As a further improvement of the present application, using the surface defect inheritance relationship of the rail with artificial defects and the casting blank with artificial defects, the analysis of the rail defects comprises:

[0044] According to the defect position on the rail and combining the first corresponding relationship, the defect position on the casting blank is traced back;

[0045] According to the defect morphology on the rail and combining the second corresponding relationship, the defect position on the casting blank is traced back;

[0046] According to the defect specification on the rail, the defect specification on the casting blank is traced back using the third corresponding relationship and the fourth corresponding relationship.

[0047] As a further improvement of the present application, the method comprises,

[0048] According to the surface structure of the rail with artificial defects and the casting blank with artificial defects, the defect extension ratio of different parts of the rail and the defect compression ratio of different parts are determined;

[0049] According to the defect extension ratio of different parts of the steel rail and the defect compression ratio of different parts, a depth-width ratio standard of the surface defect morphology of the casting blank forming an out-of-standard defect on the surface of the steel rail is determined, and the depth-width ratio standard comprises:

[0050] When the depth of the pit defect on the casting blank corresponding to the head, bottom and upper waist positions of the steel rail is less than 4mm or when the depth is less than 5mm and the depth-width ratio is not greater than 1:5, no out-of-standard defect is formed on the finished product of the steel rail;

[0051] When the depth of the pit defect on the casting blank corresponding to the lower waist position of the steel rail is less than 5.5mm or when the depth is less than 5mm and the depth-width ratio is not greater than 1:5, no out-of-standard defect is formed on the finished product of the steel rail.

[0052] The technical effects and advantages of the present application are as follows:

[0053] The casting blank artificial defect manufacturing method, artificial defect steel rail and defect analysis method of the present application drill a plurality of holes perpendicular to the surface of the casting blank in the rolling slip region and the rolling stable region on the surface of the casting blank without out-of-standard defects; then the holes are filled with refractory material and sealed, and the casting blank with artificial defects is prepared. The surface defects of the finished product of the steel rail produced by the casting blank are compared and analyzed with the artificial defects on the surface of the casting blank, so as to determine the surface defect inheritance relationship between the artificial defect steel rail and the casting blank with artificial defects, and the defect on the steel rail is successfully traced back to the casting blank, so as to help the technical personnel to quickly and accurately locate the defect position on the casting blank and estimate the defect size on the casting blank, thereby facilitating the technical personnel to select appropriate defect coping strategies and effectively improving the yield of the rolling product.

[0054] The casting blank artificial defect manufacturing method, artificial defect steel rail and defect analysis method of the present application verify that the rolling extension coefficient of the steel rail is basically consistent with the existing theory, and determine the depth-width ratio standard of the surface defect morphology of the casting blank forming an out-of-standard defect on the surface of the steel rail. By using the standard, the defect inspection of the casting blank can be intensified before the rolling of the steel rail, so that the production of unqualified products can be further effectively avoided.

[0055] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent to those skilled in the art from the description, or can be learned by practice of the present application. The objects and other advantages of the present application can be realized and obtained by the structures indicated in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 It is a structural schematic diagram of the artificial hole defect of the casting blank of the present application;

[0057] Figure 2Corresponding relationship between six artificial hole groove defects A-F on the upper surface of the end of the casting blank and six crack defects A-F on the surface of the finished rail formed after rolling;

[0058] Figure 3 Corresponding relationship between six artificial hole groove defects 1-6 on the upper surface of the middle of the casting blank and six crack defects 1-6 on the surface of the finished rail formed after rolling;

[0059] Figure 4 Corresponding relationship between five artificial hole groove defects 7-11 on the left surface of the middle of the casting blank and five crack defects 7-11 on the surface of the finished rail formed after rolling;

[0060] Figure 5 Corresponding relationship between five artificial hole groove defects 12-16 on the right surface of the middle of the casting blank and five crack defects 12-16 on the surface of the finished rail formed after rolling;

[0061] Figure 6 Corresponding relationship between six artificial hole groove defects 17-22 on the lower surface of the middle of the casting blank and six crack defects 17-22 on the surface of the finished rail formed after rolling;

[0062] Figure 7 Schematic diagram of inheritance relationship fitting between each artificial hole groove defect at four different cross sections of the middle of the casting blank and the position of the finished defect;

[0063] Figure 8 Schematic diagram of inheritance between the defect corresponding positions between the casting blank with artificial defects and the finished rail formed after rolling. DETAILED DESCRIPTION

[0064] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0065] To address the shortcomings of existing technologies, this invention discloses a method for determining the inheritance relationship between artificial defects on the surface of a cast billet and defects on the surface of the finished rail. This method involves creating artificial defect structures on the surface of the cast billet, followed by normal heating, rolling, and straightening processes. Based on the rolling elongation coefficient, samples are taken from each artificial defect location on the finished rail and ground. Crack morphology is analyzed using non-destructive testing equipment such as eddy current flaw detectors. The correspondence between artificial defects on the surface of the cast billet and defects on the surface of the finished rail is determined and summarized. This provides effective guidance for quickly selecting appropriate defect response strategies and offers a scientific basis for tracing the source of defects on the surface of the cast billet and for identifying defects in the later stages of rolling.

[0066] The details are as follows:

[0067] I. Methods and steps for fabricating artificial defects in cast billets used for rolling analysis and for manufacturing rails with artificial defects:

[0068] (1) Selection of casting billet: The selected casting billet should have a flat, smooth surface, free from pits, slag inclusions, vibration marks, cracks and other defects exceeding the standard.

[0069] (2) Drilling marks are made at a custom distance on at least one cross-section of the selected rolling slip region on the billet surface (corresponding to the billet end). For ease of subsequent analysis, such as... Figure 1 As shown, these drill marks can be arranged in a straight line, and the straight line formed by these drill marks can be set perpendicular to the length direction of the cross-section where the straight line is located. Generally, the spacing of these drill marks is 50-200mm. At the same time, drill marks are also made in the same way on the entire cross-section of the selected rolling stable area of ​​the billet surface (corresponding to the middle of the billet), and the spacing of the drill marks is also 50-200mm. In addition, in order to prevent artificial hole and groove defects from affecting the strength of the billet when they are set in the same cross-section of the billet, and causing the billet to break during the rolling process, the artificial hole and groove defects on the four cross-sections of the billet should be arranged in a staggered manner, that is, the straight lines formed by several drill marks arranged in the middle of the billet should not be connected end to end, and the staggered distance should be ≥100mm. Then, a portable suction-type drilling machine or other drilling equipment is used to drill holes along the vertical direction of the billet surface at the drill marks, thereby forming several artificial hole and groove defects on the surface of the billet.

[0070] Specifically, to ensure that the surface of the rolled rail effectively exhibits artificial defects of a certain depth, the drilling depth can be set to 10-50 mm; to ensure that the surface of the rolled rail effectively exhibits artificial defects of a certain length, the drilling diameter can be set to 5-30 mm. This setting of drilling depth and diameter satisfies the requirement of tracking defects after the billet is rolled without causing serious damage to the billet itself or affecting the smooth progress of the rolling process.

[0071] (3) After drilling, in order to prevent the artificial hole groove defects from being oxidized and heated and bonded in the heating furnace, the above problems can be effectively avoided by filling the high-temperature ceramic fiber cotton and other refractory materials in the artificial hole groove defects and performing high-temperature glue sealing.

[0072] (4) The original appearance, size and relative position of the artificial hole groove defects on the cast slab are retained by means of photographing combined with manual recording.

[0073] (5) The cast slab with the artificial hole groove defects is sent to the heating furnace for heating, descaling and rolling, and then the inheritance relationship between the cast slab surface defects and the rail product surface defects is analyzed by sampling.

[0074] II. The cast slab artificial defect manufacturing method, the artificial defect rail and the cast slab surface defect and rail product surface defect inheritance relationship analysis method provided by the present application will be described in detail in combination with a specific embodiment.

[0075] In this embodiment, the 60kg / m rail cast slab is selected as the embodiment, a cast slab surface defect manufacturing method is provided, the rolling evolution rule is tracked, and the problem that the inheritance evolution process of the cast slab surface defect in the prior art is difficult to obtain is solved.

[0076] The selected 60kg / m rail cast slab has a standard blank specification of 280*380*7750mm and a material U75V.

[0077] Before use, the cast slab surface is first cleaned of iron oxide scale and other impurities using compressed air, and the cast slab surface is cleaned of slag and other defects using an acetylene flame, so as to ensure that the cast slab surface is free of excessive defects before drilling.

[0078] In the rolling slip area, as shown in Figure 1 , a first drilling mark 6 is made on the upper surface 100mm away from the front end of the cast slab, that is, the east 100mm cross section of the corresponding upper surface of the steel slab, as shown in Figure 2 .

[0079] In the rolling stable area, a second drilling mark 6 is made on the upper surface 3775mm away from the front end of the cast slab, that is, the east 3775mm cross section of the corresponding upper surface of the steel slab, as shown in Figure 3 ; a third drilling mark 5 is made on the left side surface 3675mm away from the front end of the cast slab, that is, the east 3675mm cross section of the corresponding south side of the steel slab, as shown in Figure 4 ; and a fourth drilling mark 5 is made on the right side surface 3975mm away from the front end of the cast slab, that is, the east 3975mm cross section of the corresponding north side of the steel slab, as shown in Figure 5As shown; on the lower surface 4075mm from the front end of the billet, i.e., at the section 4075mm east of the bottom surface of the billet in the figure, mark the fifth drill hole at point 6. See details. Figure 6 As shown in the figure. The distribution spacing between the artificial slot defects in the aforementioned rolling slip region and rolling stability region is summarized in Table 1 below:

[0080] Table 1 Distribution and Spacing of Artificial Hole and Slot Defects in Cast Billets

[0081]

[0082] Next, attach the portable suction-type drilling machine to the drilling plane and drill along the vertical direction of the billet surface, setting the drilling depth to 20mm and the drilling diameter to 8mm or 6mm.

[0083] After drilling, to prevent the artificial holes and grooves from oxidizing and sticking together during the heating process in the furnace, the artificial holes and grooves were filled with high-temperature ceramic fiber cotton refractory material and sealed with high-temperature adhesive.

[0084] The original shape, dimensions, and relative positions of the artificial hole and groove defects were preserved by taking photos and recording them manually.

[0085] Finally, the artificially created slotted defect billet is sent to a heating furnace for heating, descaling, and rolling. Samples are taken to analyze the inheritance relationship between the defects on the billet surface and the finished product surface. Specifically, this includes the following:

[0086] ① Correspondence between the locations of surface defects on the cast billet and the finished rail:

[0087] like Figure 2 The figure shows the positional correspondence between the six artificial slot defects A to F on the upper surface of the billet end and the six crack defects A to F on the surface of the finished rail after rolling.

[0088] like Figure 3 The figure shows the positional correspondence between the six artificial slot defects 1 to 6 on the upper surface of the middle part of the billet and the six crack defects 1 to 6 on the surface of the finished rail after rolling.

[0089] like Figure 4 The image shows the positional correspondence between the five artificial slot defects 7-11 on the left side surface of the middle part of the billet and the five crack defects 7-11 on the surface of the finished rail after rolling.

[0090] like Figure 5 The image shows the correspondence between the positions of five artificial slot defects 12-16 on the right side surface of the middle part of the billet and the positions of five crack defects 12-16 on the surface of the finished rail after rolling.

[0091] likeFigure 6 As shown in the middle of the figure, the correspondence between the 6 artificial hole groove defects 17-22 on the lower surface of the middle of the casting blank and the 6 crack defects 17-22 on the surface of the finished rail formed after rolling is shown;

[0092] The one-to-one correspondence between the position, morphology and size of each artificial hole groove defect on the surface of the casting blank and the crack defect on the surface of the finished rail is further shown in Table 2 below.

[0093] Table 2: Corresponding position, morphology and size of artificial hole groove defects on the casting blank on the rail

[0094]

[0095] From the above, it can be seen that the artificial hole groove defects on the surface of the rail casting blank are found one by one on the surface defects of the finished product after rolling according to the theoretical rolling extension ratio 13.592, with a defect position error of ±2‰, verifying that the actual rolling extension coefficient of the rail is basically consistent with the theory. Thus, a scientific traceability basis is provided for quickly and clearly locating the defects of the finished rail back to the casting blank.

[0096] Specifically, from the longitudinal position of the defects, the first and last defects of the 6 defects on the rail head are basically consistent; when the 6 defects on the rail waist are at the end, the defects in the direction from the rail head to the rail bottom are offset from west to east, while when they are in the middle, the defects in the direction from the rail bottom to the rail head are slightly offset to the west, indicating that the metal at the head has a tendency to roll to the west; the 5 defects on the rail bottom from the lower leg tip to the upper leg tip are slightly offset to the west, indicating that the metal offset to the defect has a tendency to tilt to the west. From the defect position analysis, the defects on the rail head and the rail bottom are proportional to the relative position of the casting blank defects; but the relative position of the rail waist defects compared to the casting blank defects changes greatly, and the metal flow is more complex. According to past experience, the corner defects should be rolled to the inside of the leg tip, but in fact, the corner defects on the upper and lower surfaces of the casting blank jump over the leg tip to the rail bottom plane 10 mm away from the leg tip after rolling. In the rolling process, the metal is flowing towards the rail bottom. Based on the above facts, the technical solution proposed by the present application provides an extremely accurate basis for defect finding in the later rolling stage.

[0097] The lower Figure 7 The figure in the middle shows the one-to-one inheritance relationship between each artificial hole groove defect at 4 different cross sections of the middle of the casting blank and the finished product defect after rolling into a rail, and the inheritance relationship between the position of each artificial hole groove defect on the casting blank and the finished product surface defect is fitted on the same section. The fitting diagram shows that at the same time, Figure 8 The figure in the middle shows the one-to-one inheritance relationship between each artificial hole groove defect at 4 different cross sections of the middle of the casting blank and the finished product defect after rolling into a rail, and the inheritance relationship between the position of each artificial hole groove defect on the casting blank and the finished product surface defect is fitted on the same section. The fitting diagram shows that at the same time, The relative position relationship of the casting blank rolled into a rail can be quickly determined by technical personnel through the above two figures, and the figure can be used as a reference for finding the corresponding position of the rolling defect in the subsequent production process.

[0098] Further, according to the surface defect morphology of different parts of the steel rail, the corresponding position of the traceable casting billet defect can be defined. Specifically, from the analysis of the position distribution after defect grinding, the head, waist and bottom elongation coefficients of the steel rail casting billet in the rolling process are different, and the same section defects will form micro dislocations in the longitudinal direction due to uneven deformation in the rolling process; the rail head defects cannot be closed by rolling due to small compression ratio, and all form regular linear defects with obvious defect depth and width; the defects in the middle of the rail waist are crushed by vertical pressure due to large single reduction in rough rolling, forming irregular nodular scarring defects, and the stress concentration at the lower jaw tip is also crushed, forming strip scarring defects after rolling; the defects at the arc connection between the bottom waist and the head waist are crushed and rolled into linear defects; the defects in the lower waist of the rail are different from those in the upper waist, with large compression deformation and shallow defect depth, and are all rolled into linear defects; the defects in the rail bottom have large compression deformation and regular deformation, with relatively fixed relative spacing, and all form linear defects. Through the above corresponding relationship between the defect morphology of the billet and the defect position of the casting billet, and the corresponding relationship between the defect position of the casting billet and the defect position of the steel billet, the causes of the defects on the surface of the finished steel rail are traced, ensuring that the technical personnel can quickly and accurately select appropriate treatment measures to effectively improve the yield of the rolled steel rail.

[0099] In addition, according to the estimated situation of the oxide scale of the south side (1.68 mm), the north side (1.66 mm) and the top (1.30 mm) of the steel billet before descaling after tapping, the oxidation loss is about 0.86%. Considering the oxidation loss of the drilled hole after heating, the hole diameter After heating and oxidation, it is about The length of the linear defects on the finished steel rail is the extension of the hole diameter in the longitudinal direction; the hole depth of 20 mm is ignored in the depth direction, and the length of the linear defects on the finished steel rail is the rolling extension of the hole in the radial direction, so the defect extension ratio corresponding to the artificial defect hole diameter of different parts of the casting billet and the linear defects on the corresponding position of the finished steel rail is not the same; and the depth of the linear defects on the finished steel rail is the rolling compression of the hole in the radial direction, so the hole depth of the artificial defect of different parts of the casting billet and the depth of the linear defects on the corresponding position of the finished steel rail correspond to different compression ratios.

[0100] Therefore, according to the defect corresponding information in Table 2, the following conclusions can be obtained: the defect extension ratios of different parts of the rail are as follows: the average length of the web defect of the east 1.359 m rail at the east 100 mm section of the casting blank is 136 mm, and the average extension coefficient is 17.077; the average length of the web defect of the east 49.951 m rail at the east 3675 mm section of the casting blank is 141 mm, and the average extension coefficient is 16.21; the average length of the bottom defect of the east 51.310 m rail at the east 3775 mm section of the casting blank is 124.6 mm, and the average extension coefficient is 14.342; the average length of the head defect of the east 54.028 mm rail at the east 3975 mm section of the casting blank is 124.6 mm, and the average extension coefficient is 14.18; the average length of the lower web defect of the east 55.387 m rail at the east 4075 mm section of the casting blank is 116.2 mm, and the average extension coefficient is 13.371. (The crack extension in the rolling process is considered.)

[0101] The defect compression ratios of different parts of the rail are as follows: the average depth of the web defect of the east 1.359 m rail at the east 100 mm section of the casting blank is 1.1 mm, and the average compression ratio is 18.18; the average depth of the web defect of the east 49.951 m rail at the east 3675 mm section of the casting blank is 1.15 mm, and the average compression ratio is 17.39; the average depth of the bottom defect of the east 51.310 m rail at the east 3775 mm section of the casting blank is 1.26 mm, and the average compression ratio is 15.625; the average depth of the head defect of the east 54.028 mm rail at the east 3975 mm section of the casting blank is 1.26 mm, and the average compression ratio is 15.87; the average depth of the lower web defect of the east 55.387 m rail at the east 4075 mm section of the casting blank is 0.983 mm, and the average compression ratio is 20.339.

[0102] According to the defect extension ratio and defect compression ratio data information of different parts of the rail obtained above, the size of the original defect of the casting blank can be traced according to the size of the defect on the surface of the finished rail, so that the depth-width ratio standard of the casting blank surface defect morphology forming an excessive defect on the rail surface is obtained. According to the current judgment standard of the rail surface defect (the depth of the linear defect is ≤0.3 mm), taking a 60 Kg / m heavy rail as an example, when the depth of the pit defect on the casting blank corresponding to the rail head, bottom and upper web position is <20 / (1.5 / 0.3) = 4 mm, or when the depth is <5 mm and the depth-width ratio is ≯1:5, no excessive defect will be formed on the finished rail. When the depth of the pit defect on the casting blank corresponding to the rail lower web position is <20 / (1.1 / 0.3) = 5.5 mm, or when the depth is <5 mm and the depth-width ratio is ≯1:5, no excessive defect will be formed on the finished rail. However, sometimes the shape of the pit defect on the casting blank surface is irregular, therefore, in the rail rolling process, the casting blank surface defect should be checked more intensively, the measurement accuracy should be improved, and the heating and rolling processes should be combined for judgment.

[0103] III. The application effect of the rail defect analysis method provided by the present application will be specifically described below in combination with application examples:

[0104] In the production of a batch of 60Kg / m heavy rails, a linear defect with a size of 0.6mm (deep) * 0.4mm (wide) * 415mm (long) was found at the east 50m north end of the finished rail. According to the corresponding extension coefficient, compression ratio and defect corresponding position fitting graph, it was deduced that there might be a defect with a size of about 4.761mm (deep) * 5.7368mm (wide) * 27.89mm (long) at east 3.4826m of the billet. Such a defect was indeed found on the actual billet, and the actual position of the defect was at east 3.495m, with a size of 4.86mm (deep) * 5.62mm (wide) * 28.5mm (long). The morphology similarity reached 90%, and the position accuracy reached 98%. The defect was eliminated in time, and the yield was effectively improved.

[0105] In summary, the billet artificial defect manufacturing method, artificial defect rail and defect analysis method of the present application drill a plurality of holes perpendicular to the surface of the billet in the rolling slip region and the rolling stable region on the surface of the billet without exceeding the defect. Then, the holes are filled with refractory material and sealed to obtain a billet with artificial defects. The surface defects of the rail product produced by the billet are compared and analyzed with the artificial defects on the surface of the billet, so as to determine the surface defect inheritance relationship between the artificial defect rail and the billet with artificial defects, and successfully trace the defects on the rail back to the billet, so as to help the technical personnel quickly and accurately locate the defect position on the billet and estimate the defect size on the billet, thereby facilitating the technical personnel to select appropriate defect coping strategies and effectively improve the yield of the rolling product. In addition, the present application verifies that the rail rolling extension coefficient is basically consistent with the existing theory, and also determines the depth-width ratio standard of the billet surface defect morphology forming an exceeding defect on the rail surface. By increasing the defect inspection intensity of the billet before rail rolling, the production of unqualified products can be further effectively avoided.

[0106] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not used to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the scope of the present application shall be included in the protection scope of the present application.

Claims

1. A method for analyzing a rail defect using an artificial defect rail, characterized by, The method comprises, Comparative analysis of the surface structure of the artificial defect rail and the casting blank with artificial defects to determine the surface defect inheritance relationship of the artificial defect rail and the casting blank with artificial defects; the artificial defect rail is rolled from the casting blank with artificial defects; wherein the casting blank with artificial defects is prepared by the following method, comprising drilling a plurality of holes perpendicular to the surface of the casting blank in the rolling slip area and the rolling stable area of the surface of the casting blank without exceeding the standard defects; the casting blank without exceeding the standard defects includes: casting blank with flat, smooth, no pit, no slag inclusion, no vibration mark and no crack surface; fill the holes with refractory material and seal to prevent oxidation and bonding of the holes during rolling; thus the casting blank with artificial defects is obtained; Using the surface defect inheritance relationship of the artificial defect rail and the casting blank with artificial defects to analyze the rail defects; the surface defect inheritance relationship of the artificial defect rail and the casting blank with artificial defects includes: the first correspondence relationship between the surface defect position of the casting blank with artificial defects and the surface defect position of the artificial defect rail; the second correspondence relationship between the surface defect position of the casting blank with artificial defects and the surface defect morphology of the artificial defect rail; the third correspondence relationship between the surface defect depth of the casting blank with artificial defects and the surface defect depth of the artificial defect rail; the fourth correspondence relationship between the surface defect aperture of the casting blank with artificial defects and the surface defect length of the artificial defect rail; analyzing the rail defects, including: according to the defect position on the rail combined with the first correspondence relationship to trace the defect position on the casting blank; according to the defect morphology on the rail combined with the second correspondence relationship to trace the defect position on the casting blank; according to the defect specification on the rail using the third correspondence relationship and the fourth correspondence relationship to trace the defect specification on the casting blank; the first correspondence relationship includes: The first hole defect at the end of the casting blank corresponds to the defect at the waist of the finished rail; The second hole defect in the middle of the casting blank corresponds to the defect at the waist of the finished rail; The third hole defect in the middle of the casting blank corresponds to the defect at the bottom of the finished rail; The fourth hole defect in the middle of the casting blank corresponds to the defect at the head of the finished rail; The fifth hole defect in the middle of the casting blank corresponds to the defect at the lower waist of the finished rail; The second correspondence relationship includes: The fourth hole defect in the middle of the casting blank forms a deep and wide regular line defect at the head of the artificial defect rail; The first hole defect at the end of the casting blank and the second hole defect in the middle of the casting blank form irregular lump scar defects and / or strip scar defects at the rail waist of the artificial defect rail; The fifth hole defect in the middle of the casting blank forms a shallow line defect at the lower waist of the artificial defect rail; The third hole defect in the middle of the casting blank forms a line defect at the bottom of the artificial defect rail; The third correspondence relationship includes: The average compression ratio of the first hole defect depth at the end of the casting blank corresponding to the surface line defect depth of the rail is 18.18; The average compression ratio of the second hole groove defect depth in the middle of the casting blank corresponding to the rail surface line defect depth is 15.625; The average compression ratio of the third hole groove defect depth in the middle of the casting blank corresponding to the rail surface line defect depth is 17.39; The average compression ratio of the fourth hole groove defect depth in the middle of the casting blank corresponding to the rail surface line defect depth is 15.87; The average compression ratio of the fifth hole groove defect depth in the middle of the casting blank corresponding to the rail surface line defect depth is 20.339; The fourth corresponding relationship includes: The average extension coefficient of the first hole groove defect aperture in the end of the casting blank corresponding to the rail surface line defect length is 17.077; The average extension coefficient of the second hole groove defect aperture in the middle of the casting blank corresponding to the rail surface line defect length is 14.342; The average extension coefficient of the third hole groove defect aperture in the middle of the casting blank corresponding to the rail surface line defect length is 16.21; The average extension coefficient of the fourth hole groove defect aperture in the middle of the casting blank corresponding to the rail surface line defect length is 14.18; The average extension coefficient of the fifth hole groove defect aperture in the middle of the casting blank corresponding to the rail surface line defect length is 13.

371.

2. The method for analyzing rail defects according to claim 1, wherein, The several hole grooves in the rolling stable region are distributed on the full cross section of the middle of the casting blank and are arranged staggeredly; The several hole grooves in the rolling slip region are distributed on at least one cross section of the end of the casting blank; The several hole grooves distributed on any cross section of the middle and end of the casting blank are arranged in a straight line, and the interval between the several hole grooves in the same straight line is set to 50-200 mm.

3. The method for analyzing rail defects according to claim 2, wherein, The several straight lines arranged do not connect at the head and tail and the staggered interval is ≥100 mm.

4. The method for analyzing rail defects according to claim 3, wherein, The set depth of the hole groove is 10-50 mm.

5. The method for analyzing rail defects according to claim 3, wherein, The set aperture of the hole groove is 5-30 mm.

6. The method of rail defect analysis of claim 1, wherein, The method includes, According to the surface structure of the artificial defect rail and the casting blank with artificial defects, the defect extension ratio of different parts of the rail and the defect compression ratio of different parts are determined; According to the defect extension ratio of different parts of the rail and the defect compression ratio of different parts, the depth-width ratio standard of the casting blank surface defect morphology forming an out-of-standard defect on the rail surface is determined, and the depth-width ratio standard includes: When the depth of the pit defect on the casting blank corresponding to the head, bottom and upper waist positions of the rail is <4 mm or when the depth is <5 mm and the depth-width ratio is ≯1:5, no out-of-standard defect is formed on the rail product; When the depth of the pit defect on the casting blank corresponding to the lower waist position of the rail is <5.5 mm or when the depth is <5 mm and the depth-width ratio is ≯1:5, no out-of-standard defect is formed on the rail product.

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