A method for grinding the post-weld working edge of a side-grinding rail aluminum thermite welded joint

Abstract

The application discloses a kind of side grinding rail aluminum thermal welding joint post-weld working edge grinding method, wherein the two rails to be welded, the relatively light side grinding degree or new rail is rail 1, and the relatively serious side grinding degree is rail 2, and rail 1 and rail 2 are aligned using non-working edge alignment mode before aluminum thermal welding;The method comprises the following steps: I.Measuring the arching amount of one side of the non-working edge of rail 1;II.Determine the grinding length and depth of the working edge of rail 1;III.Grinding joint and rail 1 near-end rail;IV.Grinding rail 1 far-end rail;V.Determine the grinding effect of rail 1;VI.Grinding the working edge of rail 2.For the convenience of on-site repair, the application also provides a side grinding rail working edge grinding quick-check table.The method of the application provides post-weld working edge grinding data support for aluminum thermal welding joints under different side grinding conditions, which is of great significance for reducing operation difficulty, standardizing on-site operation, improving post-weld joint quality and improving rail working edge smoothness.

Description

Technical Field

[0001] This invention belongs to the field of rail welding technology, specifically relating to a method for grinding the working edge of a thermite welded joint of a side-grinding rail after welding. Background Technology

[0002] The working edge is the part of the rail that directly contacts the train wheel flange. On existing railway lines, especially those with small curve radii, rails will experience wear on their working edges during service, a phenomenon known as "rail side wear." Rails with this wear on their working edges are called "side-wearing rails." The inventors investigated rail wear at different curve radii and measuring points on various railway lines in China. The results show that for rails with small curve radii, even when the top surface shows little or no wear, significant wear is already present on the side. Furthermore, rail side wear is related to the curve radius, rail strand number, and position on the curve: as the curve radius decreases, the amount of rail side wear increases; side wear mainly occurs on the upper strands of the curve; and the three measuring points with the largest wear are the gentle curve, the middle of the curve, and the curve-gentle curve.

[0003] The "Rules for Repairing Conventional Speed ​​Railway Lines" specifies the following standard for rail wear and damage at 60 kg / m: (The standard is based on the line design speed v). max For mainline sections with a design speed >160km / h, side wear of 10mm is considered minor damage, and 12mm is considered severe damage; for lines with a design speed ≥160km / h, v max For mainline road sections with speeds exceeding 120 km / h, side wear of 12 mm is considered minor damage, and 16 mm is considered severe damage; max For mainline and arrival / departure sections with speeds ≤120km / h: side wear of 14mm is considered minor damage, and 19mm is considered severe damage. Preliminary survey results also indicate that most significant side wear occurs due to v... max For conventional speed lines with a speed of ≤160km / h, the rail side wear during the survey period ranged from 0-10mm, which is related to various factors such as train axle load, annual total weight, track condition, and rail replacement cycle.

[0004] When a rail is damaged by side grinding, the insertion welding method is usually used to repair the track during the maintenance window. That is, the damaged part of the rail is cut off and a pre-matched rail section is inserted, and aluminothermic welding is performed at both ends. The current welding process is: when the rail is aligned, it is aligned with the non-working side. After the sand mold is installed, the gap on the working side is filled with cardboard and then the box is sealed. Due to the existence of rail side grinding, the following three situations will occur: (1) the rail on the line has no side grinding or basically no side grinding, and the inserted rail has side grinding; (2) the rail on the line has side grinding, and the inserted rail has no side grinding or basically no side grinding; (3) both the rail on the line and the inserted rail have side grinding, but the amount of side grinding is inconsistent. In any case, there will be a dimensional difference in the width direction of the rail on both sides of the working side of the welded joint. If it is not treated, it will destroy the smoothness of the rail on both sides of the aluminothermic welded joint within a certain range, thereby affecting the stability of train operation, reducing the service performance of the welded joint and the rail, and increasing the probability of the joint being damaged again. Therefore, after aluminothermic welding, the working edge of the aluminothermic weld joint of the side-grinding rail must be ground.

[0005] TB / T 1632.1—2014 "Rail Welding Part 1: General Technical Conditions" specifies the following requirements for the straightness of the welded joint after aluminothermic welding: No low joints should appear within a 1m length of the working surface of the rail head. When the track design speed v... max When the speed is ≤160km / h, 0.1≤a1≤0.4, 0≤b1≤0.3 or 0≤b2≤0.3 (a1 represents the straightness of the top surface of the rail head, b1 and b2 represent the straightness of the working edge of the side, where a positive value of b1 indicates that the gauge is widened, and a positive value of b2 indicates that the gauge is reduced, the unit is mm / m); the grinding depth of the base material should be less than 0.5mm.

[0006] Currently, there are almost no specific process requirements for grinding worn rails after aluminothermic welding within railway bureaus and stations. The process mainly relies on the experience of on-site workers, following the grinding methods used when welding new rails. The inventors previously proposed a method for grinding the rail top surface after aluminothermic welding of vertically ground rails with worn top surfaces. This method is significant for providing data support for post-weld grinding, reducing operational difficulty, standardizing on-site operations, improving the quality of welded joints, and enhancing the smoothness of the rail top surface. However, there has been little research and reporting to date on methods for grinding the working edge of aluminothermic welded joints of side-ground rails. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this paper proposes a method for grinding the working edge of aluminothermic welded joints after side grinding, based on survey data and requirements in relevant standards and specifications. This method provides data support for grinding the working edge of aluminothermic welded joints under different side grinding conditions, which is of great significance for reducing operational difficulty, standardizing on-site operations, improving the quality of post-weld joints, and enhancing the smoothness of the working edge of the rail.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A method for grinding the working edge of an aluminothermic welded joint of a side-ground steel rail; wherein the two rails to be welded are, respectively, rail 1 (with relatively minor side grinding or a new rail) and rail 2 (with relatively severe side grinding). Before aluminothermic welding, rail 1 and rail 2 are aligned using a non-working edge alignment method; the post-weld grinding method includes the following steps:

[0010] I. Measurement of camber on the non-working side of track 1

[0011] Place a 1m notched straightedge on the longitudinal line 16mm from the top surface of the rail on the non-working side, aligning the 0 mark with the center of the weld. Use a feeler gauge or gap gauge to measure the camber B on the non-working side of rail 1, in mm / m. When the camber appears at the center of the 1m straightedge, B is recorded as a negative value; when the camber appears at the edge of the 1m straightedge, B is recorded as a positive value.

[0012] II. Determine the grinding length and depth of the working edge of rail 1.

[0013] If B≤0mm / m, use formula (1)-1 to calculate the grinding depth C of rail 1, and use formula (1)-2, (1)-3 or (1)-4 to calculate the grinding length L of the working edge of rail 1:

[0014] C = C0 + Q(b) f -B)(1)-1,

[0015] When b f When <0, Or when b f When = 0, Or when b f When >0,

[0016] If B > 0 mm / m, use formula (2)-1 to calculate the grinding depth C of rail 1, and use formula (2)-2, (2)-3 or (I)-4 to calculate the grinding length L of the working edge of rail 1:

[0017] C = C0 + Q(0.5Bb) f (2)-1

[0018] When b f When = 0,

[0019] Or when b f When >0,

[0020] In the above formulas (1)-1, (1)-2, (1)-3, (2)-1, (2)-2, and (2)-3,

[0021] C0 represents the dimensional difference in the side grinding between rail 1 and rail 2 before welding, in mm.

[0022] Q is a constant, taken as a fixed value of 1m.

[0023] B represents the camber of the non-working side of rail 1, in mm / m.

[0024] b f The target straightness of the joint and near end after grinding of rail 1 is set, in mm / m, and -0.3≤b f ≤0.3mm / m,

[0025] t is the target smoothness of the far end after the track 1 is polished, in mm / m, and t = 1 mm / m;

[0026] In the above formulas (1)-2, (1)-3 and (1)-4, Grinding length L at the far end of the working edge of rail 1 远 The other item is the near-end grinding length L of the working edge of rail 1. 近 ;

[0027] In the above formulas (2)-2 and (2)-3, Grinding length L at the far end of the working edge of rail 1 远 The other item is the near-end grinding length L of the working edge of rail 1. 近 ;

[0028] III. Grinding the joint and the near end of rail 1.

[0029] First, based on the calculated grinding depth C and proximal grinding length L... 近 Mark the end point of the grinding depth and the end point of the grinding near the working edge respectively. Then use a grinder to grind the center of the weld and the near end of the working edge of rail 1 to the end point of the grinding depth and the end point of the grinding near the working edge.

[0030] IV. Grinding rail 1, far end rail

[0031] First, based on the calculated distal grinding length L... 远 Mark the end point of the far end grinding, and then use a grinder to grind from the end point of the near end grinding towards the end point of the far end grinding of rail 1.

[0032] V. Determine the grinding effect of rail 1

[0033] During and after grinding, the straightness of the weld and rail 1 is continuously measured using a 1m straightedge, SRC electronic straightedge or rail wear gauge until the straightness meets the standard requirements.

[0034] VI. Working edge of grinding rail 2

[0035] The working edge of rail 2 is ground using conventional methods until it meets the standard requirements for straightness.

[0036] In step I, the actual measured camber amount B is retained to one decimal place, for example, -0.3mm / m, -0.2mm / m, -0.1mm / m, 0mm / m, 0.1mm / m, 0.2mm / m, 0.3mm / m, 0.4mm / m, 0.5mm / m, 0.6mm / m, 0.7mm / m, 0.8mm / m, etc.

[0037] In step I, when measuring the camber of the non-working side of rail 1, the following three situations may occur:

[0038] (1) As Figure 4 As shown in Figure A, the camber is located at the center of the weld on the non-working side of rail 1 or at the center of a 1m straightedge. B is marked as a negative value, indicating that the working side of rail 1 is in a state of reduced gauge.

[0039] (2) Figure 4 As shown in Figure B, the arching occurs at the edge of a 1m straightedge. B is marked as a positive value, indicating that the working side of rail 1 is in a state of increased gauge.

[0040] (3) Figure 4 As shown in Figure C, the non-working side of track 1 does not arch, and B is recorded as 0.

[0041] b f A negative value also indicates a decrease in track gauge, b f A positive value indicates an increase in track gauge.

[0042] Preferably, in steps IV and VI, a contour grinder or a circumferential grinder is used for grinding.

[0043] Preferably, the specific operation for aligning rails 1 and 2 before aluminothermic welding is as follows:

[0044] Place a 1m straightedge 10-16mm below the top of the rail on the non-working side of the rail head, with the 0 mark at the center of the rail gap. Use a special rail alignment device such as an A-frame, iron wedge, or rail lifter to adjust the width angle of the rails on both sides until the non-working sides of both rails are in close contact with the straightedge.

[0045] Preferably, in steps V and VI, the standard is TB / T 1632.1-2014 "Rail Welding Part 1: General Technical Conditions".

[0046] The specific requirements in the above standard are: No low joints should appear within a 1m length of the working surface of the rail head of the welded rail joint. When the design speed of the line v≤160km / h, 0.1≤a1≤0.4, 0≤b1≤0.3 or 0≤b2≤0.3. (a1 represents the straightness of the top surface of the rail head, b1 and b2 represent the straightness of the working edge of the side, where a positive value for b1 indicates a wider track gauge, and a positive value for b2 indicates a smaller track gauge; the unit is mm / m). The grinding depth of the base material should preferably be less than 0.5mm.

[0047] As a preferred embodiment, in step II, when C0 = 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, and -0.3mm / m ≤ B ≤ 0.8mm / m, the grinding depth and length of the working edge of rail 1 are determined according to Table 1 below; otherwise, the grinding length and depth of the working edge of rail 1 are calculated according to formula (1)-1 and one of (1)-2, (1)-3 or (1)-4, or formula (2)-1 and one of (2)-2 or (2)-3 respectively:

[0048] Table 1 Quick Reference Table for Grinding the Working Edge of Side-Grinding Steel Rails

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056] During on-site operations, due to numerous variables such as the actual amount of rail side grinding, the amount of camber on the non-working edge after welding, and the target straightness, coupled with the precious time and harsh conditions during maintenance windows, calculating the grinding depth and length on-site would affect work efficiency. However, by referring to Table 1 above, the grinding depth and length can be determined quickly and conveniently.

[0057] When the total grinding length exceeds half the length of rail 1 due to excessive side grinding difference, it is advisable to pre-assemble or prefabricate rails with small side grinding difference before welding.

[0058] In this specification, "existing line" refers to a concept relative to newly constructed lines, namely, railway lines that have already borne a certain amount of traffic and load. Existing lines are in operation, and maintenance and repair time is limited.

[0059] The term "side-wearing rail" refers to the wear that occurs along the width of the rail head at the contact point between a standard profile rail and the train wheel after a period of service.

[0060] In this specification, "aluminothermic welding" refers to a method of welding two rail sections together by mixing aluminum powder, iron oxide powder, and ferroalloys in a certain proportion to form an aluminothermic welding flux, igniting it with a high-temperature match to produce molten steel and slag. The high-temperature molten steel is then poured into a mold to weld the rails together. Therefore, aluminothermic welding is also called cast welding. The main steps of aluminothermic welding are generally: preparation, drying the rails, rust and dirt removal, rail alignment, sand mold installation, clamp installation, sealing the mold, preheating, crucible flux preparation, reaction casting, mold removal, slag removal, and grinding. The grinding method described in this invention is the final step in the aluminothermic welding process.

[0061] The term "joint grinding" or "joint grinding" refers to the use of a grinding machine to repair the aluminothermic welded joint and the steel rail base material on both sides so that its surface quality meets the standard requirements.

[0062] In this specification, "longitudinal" refers to the length direction of the rail.

[0063] In this manual, the terms "near end" or "far end" for rails refer to those relative to the weld center. Rails closer to the weld center are considered "near end," while those farther away are considered "far end."

[0064] The term "straightness" refers to the center of the weld and the rails near it, while "smoothness" refers to the rails at the far end. Attached Figure Description

[0065] The present invention will be further described below with reference to the accompanying drawings.

[0066] Figure 1 The image shown is a photograph of rails 1 and 2 aligned with their non-working edges in Example 1. In the figure, 1: rail 1; 2: rail 2.

[0067] Figure 2 The photograph shows the sand mold being installed after rails 1 and 2 are aligned in Example 1. In the figure, 2: rail 2; 3: high-temperature asbestos; 4: sand mold.

[0068] The photo shows that there is a large gap between the rail head of rail 2 and the sand mold, so high-temperature asbestos is pasted to fill the gap.

[0069] Figure 3The photograph shows the working edge of the welded joint after welding in Example 1. In the figure: 1: rail 1; 2: rail 2.

[0070] Figure 4 This is a schematic diagram for measuring the camber on the non-working side, where:

[0071] A: When the gauge on the working side decreases, the arching of the non-working side of rail 1 is at the center of the weld or straightedge.

[0072] B: When the gauge increases on the working side, the arching of the non-working side of rail 1 is at the edge of the straightedge.

[0073] C: The gauge on the working side remains unchanged, and the non-working side of rail 1 fits tightly with the straightedge, with no or virtually no gaps.

[0074] In the diagram, 1: track 1; 2: track 2.

[0075] Figure 5 This is a diagram of the grinding process, where A represents an end face grinding machine and B represents a circumferential surface grinding machine.

[0076] In the diagram: 1: Rail 1; 2: Rail 2.

[0077] Figure 6 This is a schematic diagram showing the overall trend of the rail grinding area and the working edge of the rail after grinding. Figure 6 As shown in the figure. The dashed box indicates the area that needs to be ground; the upper line segment is a projection of the overall trend of the working edge of the rail: point -1 is the grinding end point of one end of rail 2, point 0 is the weld center, point 1 is the grinding end point of the near end of rail 1, and point 2 is the grinding end point of the far end of rail 1.

[0078] Figure 7 This is a photo of the working edge of track 1 after grinding in Example 1.

[0079] In the diagram, 1: track 1; 2: track 2. Detailed Implementation

[0080] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0081] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available products.

[0082] In the following embodiments, ZTK-1 type aluminothermic welding material (Beijing CRRC New Material Technology Co., Ltd.) was used, with flux type T3. Both sections of rail being welded were 60kg / m U71Mn H rails, one being a new rail (hereinafter referred to as "Rail 1") and the other a side-ground rail (hereinafter referred to as "Rail 2"). Welding tools included a dedicated preheating device, sand mold clamps, alignment equipment, rail saw, buttress pusher, and grinder.

[0083] All welding process parameters follow the specifications in the aluminothermic welding operation manual provided by the manufacturer, with a rail gap of 28-30mm reserved. Using the non-working edge alignment method, there is no difference in profile between the two ends of the rail to be welded in the height direction; therefore, standard profile sand molds can be used for welding.

[0084] During rail alignment, align the non-working edges and adjust them to a smooth state. The specific method is as follows: Place a 1m straightedge on one side of the non-working edge of the rail head, 10-16mm below the top surface of the rail, with the 0 mark at the center of the rail gap. Use a specialized rail alignment device such as an A-frame, wedges, or rail lifters to adjust the width angle of both rails until the non-working edges of both rails are tightly fitted with the straightedge. See [link to relevant documentation]. Figure 1 ...

[0085] After the rails are aligned, install the clamping sand mold. See also Figure 2 After installing the standard profile sand mold, if there is a large gap between the rail head and the sand mold at one end of rail 2 (side-grinding steel rail), the gap is filled by locally bonding high-temperature asbestos. The preheater support is placed at one end of rail 1, with a height of 50mm. The preheating gas pressure is 0.3MPa oxygen gas and 0.1MPa propane gas. The preheater height is 50mm, and the preheating time is 4 minutes. After pouring, the mold is removed after 6 minutes and 30 seconds, and the slag is pushed out after 8 minutes and 30 seconds. No overflow or flash was generated at any part of the welded joint. See [reference needed]. Figure 3 .

[0086] A schematic diagram of the rail grinding area and the overall trend of the working edge of the rail after grinding is shown below. Figure 6 As shown. Figure 6 In the diagram, the dashed box indicates the area requiring grinding, and the upper line segment represents the overall trend projection of the working edge of the rail: Point -1 is the grinding endpoint at one end of rail 2, point 0 is the weld center, point 1 is the near-end grinding endpoint at one end of rail 1, and point 2 is the far-end grinding endpoint. The overall effect is a certain amount of camber on both sides of the weld. This camber can increase the track gauge (as shown by the solid line at the top), keep the track gauge unchanged (as shown by the dashed line in the middle), or decrease the track gauge (as shown by the dotted line at the bottom). The rail on one side of rail 1 transitions from the far end to the near-end grinding endpoint with a certain slope.

[0087] Example 1: Grinding method for the working edges of rails 1 and 2 after aluminothermic welding with a side grinding difference of 6mm.

[0088] During aluminothermic welding, rails 1 and 2 are aligned with their non-working edges. See the completed image for a sample. Figure 1 After the rails are aligned, a standard profile sand mold is installed. There is a large gap between the rail head of rail 2 (side-ground rail) and the sand mold. This gap is filled by locally applying high-temperature asbestos. Figure 2 As shown. The working edge of the joint after welding is as follows. Figure 3 As shown, no overflow burrs were generated at any part of the welded joint. Grinding of the working edge of rail 1 after welding was performed according to the following steps:

[0089] I. Measurement of camber on the non-working side of track 1

[0090] Place a 1m notched straightedge on the non-working side of rail 1, 16mm from the top surface of the rail, along the longitudinal line. Align the 0 mark with the center of the weld. The camber should be at the edge of the straightedge. Figure 4 As shown in B, the camber on the non-working side of rail 1 is measured using a feeler gauge or gap gauge, and the camber B = 0.4 mm / m.

[0091] II. Determine the grinding length and depth of the working edge of rail 1.

[0092] Because the measured B = 0.4 mm / m, b is set. f =0.2mm / m, the grinding depth C of rail 1 is calculated using formula (2)-1, and the grinding length L of rail 1 is calculated using formula (2)-3:

[0093] C = C0 + Q(0.5Bb) f (2)-1,

[0094]

[0095] Where C0 represents the difference in side grinding dimensions between the working edges of rail 1 and rail 2 before welding, in mm; here C0 = 3 mm.

[0096] B represents the camber of the non-working side of rail 1, in mm / m; here, B = 0.4 mm / m.

[0097] b f The target straightness of the joint and near end after grinding of rail 1 is set, in mm / m, where b f =0.2mm / m,

[0098] t is the target smoothness of the far end after the track 1 is polished, in mm / m, and t = 1 mm / m;

[0099] In the above formulas (2)-3, Grinding length L at the far end of the working edge of rail 1 远The other item is the near-end grinding length L of the working edge of rail 1. 近 ;

[0100] Calculations show that C = 6 mm, L 近 =1m, L 远 =6m, total polishing length L =7mm.

[0101] Referring to Table 1, we can quickly determine: C = 6 mm, L 近 =1m, L 远 =6m, total polishing length L =7mm.

[0102] III. Grinding the joint and the near end of rail 1.

[0103] First, based on the calculated grinding depth C and proximal grinding length L... 近 Mark the grinding depth endpoint and the grinding endpoint near the working edge, respectively, and then... Figure 5 As shown, use a grinder to grind the center of the weld and the near end of the working edge of rail 1 to the end of the grinding depth and the near end of the grinding.

[0104] IV. Grinding rail 1, far end rail

[0105] First, based on the calculated distal grinding length L... 远 Mark the end point of the far end grinding, and then use a grinder to grind from the end point of the near end grinding towards the end point of the far end grinding of rail 1.

[0106] V. Determine the grinding effect of rail 1

[0107] During and after grinding, the straightness of the weld and rail is continuously measured using a 1m straightedge, SRC electronic straightedge, or rail wear gauge until the straightness meets the standard requirements.

[0108] VI. Working edge of grinding rail 2

[0109] The working edge of rail 2 is ground using conventional methods until it meets the standard requirements for straightness.

[0110] After the working edge of rail 1 is ground, as follows Figure 7 As shown in the photo.

[0111] Example 2: Grinding method for the working edges of rails 1 and 2 after aluminothermic welding with a side grinding difference of 12mm.

[0112] The post-weld grinding was performed following the same steps as in Example 1, except that in step I, the camber B on one side of rail 1 was measured to be 0 mm / m (i.e., Figure 4 (As shown in C), set b f =0mm / m, using formulas (1)-1 and (1)-3:

[0113] C = C0 + Q(b) f -B)(1)-1,

[0114]

[0115] Where C0 represents the difference in side grinding dimensions between the working edges of rail 1 and rail 2 before welding, in mm; here C0 = 12 mm.

[0116] B represents the camber of the non-working side of rail 1, in mm / m; here, B = 0 mm / m.

[0117] b f The target straightness of the joint and near end after grinding of rail 1 is set, in mm / m, where b f =0mm / m,

[0118] t is the target smoothness of the far end after the track 1 is polished, in mm / m, and t = 1 mm / m;

[0119] In the above formulas (1)-3, Grinding length L at the far end of the working edge of rail 1 远 The other item is the near-end grinding length L of the working edge of rail 1. 近

[0120] Calculations show that C = 12 mm, L 近 =12m, L 远 =13m, total polishing length L=13mm.

[0121] Because the difference in side grinding dimensions between rail 1 and rail 2 is C0 = 12mm, which exceeds the range listed in Table 1, the grinding parameters can only be calculated using formulas.

[0122] In summary, this invention provides a method for grinding the working edge of an aluminothermic welded joint after side grinding. This method provides data support for grinding the working edge of the aluminothermic welded joint under different side grinding conditions, which is of great significance for reducing operational difficulty, standardizing on-site operations, improving the quality of the welded joint, and improving the smoothness of the working edge of the rail.

Claims

1. A method for grinding the working edge of an aluminothermic welded joint of a side-ground steel rail; wherein the two rails to be welded are, respectively, rail 1 being the one with relatively minor side grinding or a new rail, and rail 2 being the one with relatively severe side grinding; before aluminothermic welding, rail 1 and rail 2 are aligned using a non-working edge alignment method; the grinding method includes the following steps: I. Measure the camber on the non-working side of track 1 Place a 1-meter notched straightedge on the longitudinal line 16mm from the top surface of the rail on the non-working side, aligning the 0 mark with the center of the weld. Use a feeler gauge or gap gauge to measure the camber B on the non-working side of rail 1, in mm / m. When the camber appears at the center of the 1-meter straightedge, B is recorded as a negative value; when the camber appears at the edge of the 1-meter straightedge, B is recorded as a positive value. II. Determine the grinding length and depth of the working edge of rail 1. If B≤0 mm / m, the grinding depth C of rail 1 is calculated using formula (1)-1, and the grinding length L of the working edge of rail 1 is calculated using formula (1)-2, (1)-3 or (1)-4: （1）-1， When b f When <0, (1) -2, or When b f When =0, (1) -3, or When b f When >0, (1) -4; If B > 0 mm / m, use formula (2)-1 to calculate the grinding depth C of rail 1, and use formula (2)-2, (2)-3 or (I)-4 to calculate the grinding length L of the working edge of rail 1: （2）-1 When b f When =0, (2) -2, or When b f When >0, (2) -3; In the above formulas (1)-1, (1)-2, (1)-3, (I)-4, (2)-1, (2)-2 and (2)-3, C0 represents the dimensional difference in the side grinding between rail 1 and rail 2 before welding, in mm. Q is a constant, taken as a fixed value of 1 m. B represents the camber of the non-working side of rail 1, in mm / m. b f The target straightness of the joint and near end after grinding of rail 1 is set, in mm / m, and -0.3≤b f ≤0.3 mm / m, t is the target smoothness of the far end after the track 1 is polished, in mm / m, and t = 1 mm / m; In the above formulas (1)-2, (1)-3 and (1)-4, Grinding length of the far end of the working edge of rail 1 The other item is the near-end grinding length of the working edge of rail 1. ; In the above formulas (2)-2 and (2)-3, Grinding length of the far end of the working edge of rail 1 The other item is the near-end grinding length of the working edge of rail 1. ; III. Grinding the joint and the near end of rail 1 First, based on the calculated grinding depth C and proximal grinding length... Mark the end point of the grinding depth and the end point of the grinding near the working edge respectively. Then use a grinder to grind the center of the weld and the near end of the working edge of rail 1 to the end point of the grinding depth and the end point of the grinding near the working edge. IV. Grinding rail 1 at the far end of the rail First, based on the calculated distal grinding length... Mark the end point of the far end grinding, and then use a grinder to grind from the end point of the near end grinding towards the end point of the far end grinding of rail 1. V. Determine the grinding effect of rail 1 During and after grinding, the straightness of the weld and rail 1 is continuously measured using a 1 m straightedge, SRC electronic straightedge or rail wear gauge until the straightness meets the standard requirements. VI. Working edge of grinding rail 2 The working edge of rail 2 is ground using conventional methods until it meets the standard requirements for straightness.

2. The polishing method according to claim 1, characterized in that, In steps IV and VI, a contour grinder or a circumferential grinder is used for grinding.

3. The polishing method according to claim 1, characterized in that, Before aluminothermic welding, the specific steps for aligning rails 1 and 2 are as follows: Place a 1-meter straightedge on the non-working side of the rail head, 10-16 mm below the top surface of the rail, with the 0 mark at the center of the rail gap. Use a special rail alignment device such as an A-frame, iron wedge, or rail lifter to adjust the width angle of the rails on both sides until the non-working sides of both rails are in close contact with the straightedge.

4. The polishing method according to claim 1, characterized in that, In steps V and VI, the standard is TB / T1632.1-2014 "Rail Welding Part 1: General Technical Conditions".

5. The polishing method according to claim 4, characterized in that, The specific requirements in the standard are as follows: low joints should not appear within a 1m length of the working surface of the rail head of the rail welded joint; when the design speed of the line is v≤160km / h, 0.1≤a1≤0.4, 0≤b1≤0.3 or 0≤b2≤0.3; a1 represents the straightness of the top surface of the rail head, b1 and b2 represent the straightness of the working side edge, where a positive value of b1 indicates that the gauge is widened, and a positive value of b2 indicates that the gauge is reduced, with the unit being mm / m; the grinding depth of the base material should be less than 0.5 mm.

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