JP2012196704A - Gas pressure welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas pressure welding method in which the oxide that causes the generation of defects of cracks, wounds or the like is decreased enough.SOLUTION: In the gas pressure welding method, at first, recessed parts 5 are each formed at end faces 2, 2 of two railway rails 1, 1 (step 101). Next, the two railway rails 1, 1 are butted by those end faces 2, 2 (step 102). Thus, the end faces 2, 2 of the railway rails 1, 1 are mutually touched at the centers 3, 3, and are mutually spaced at the peripheral edges 4, 4, and a gap 11 in which the recessed parts 5, 5 are combined is formed in a groove shape between the peripheral edges 4, 4. Next, those butting parts are heated by the combustion flame consisting of oxygen gas and acetylene gas while making the pressurizing force of a material axial compression direction act on the railway rails 1, 1. In the heating, the combustion flame is blown into the gap 11 between the end faces 2, 2 (step 103).

Description

  The present invention relates to a gas pressure welding method applied when joining structural steel materials such as rails and reinforcing bars, in particular railroad rails.

  In laying rails, many long rails that are several hundred meters long have been used to weld noise to reduce noise and improve riding comfort. Uses welding techniques such as gas pressure welding, thermite welding, and flash welding.

  Among these, gas pressure welding is a method in which two rails to be joined are butted at a ground end face, and in this state, a pressure is applied in the compression direction of the material shaft, and the butted portion is heated and softened with an oxygen acetylene flame. However, it is classified as a so-called solid-phase joining method that joins by applying mechanical pressure without melting the surfaces to be joined, and the rails can be joined with strength close to the base material. It is widely used as a welding technique.

  On the other hand, in gas pressure welding, if excessive oxide remains on the end surface of the rail, the metal bond is hindered and the strength of the joint is lowered, and when the bulge of the pressure welding portion is sheared away by hot punching, shearing occurs. The accompanying plastic deformation causes defects such as cracks and flaws in the remaining portions of the oxide.

  Under such a background, a combustion flame in which the amount of acetylene gas is larger than the amount of oxygen gas is used as an oxygen acetylene flame for performing gas pressure welding.

JP 2005-238250 A JP 2001-152290 A JP-A-7-227684

  In gas pressure welding using such a combustion flame, acetylene that does not react with oxygen during combustion is present in the combustion flame as a surplus, and the carbon contained in this acetylene reduces the oxide, so that an oxide is present in the vicinity of the rail junction. Even if this occurs, the oxide is decomposed and removed by the carbon of acetylene, and it is possible to avoid the occurrence of defects such as cracks.

  However, when the present applicant examined the vicinity of the joint portion of the rail gas-welded with the above-mentioned combustion flame by the magnetic particle flaw detection test, the occurrence of defects (scratches) in the vicinity of the joint portion was slightly confirmed, and the excess acetylene was caused by carbon. It has been found that it is difficult to completely suppress the amount of oxide remaining in the vicinity of the junction by only the reducing action of the oxide.

  Therefore, when the skill level of the worker in the pressure welding operation is low, there is a concern that the amount of oxide remaining in the vicinity of the joint cannot be sufficiently reduced, and the technology capable of more reliably removing the oxide. The development of was urgent.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a gas pressure welding method capable of sufficiently reducing oxides that cause defects such as cracks and scratches. .

In order to achieve the above object, the gas pressure welding method according to the present invention, as described in claim 1, butts two structural steel materials at their end faces, and applies pressure in the axial direction to the structural steel material. In the gas pressure welding method in which the two structural steel materials are joined to each other by heating the butted portions with a combustion flame made of oxygen gas and acetylene gas while acting,
When the structural steel materials are abutted at their end faces, a concave portion is formed on the end face of at least one of the structural steel materials so that the end faces are in contact with each other at the center and separated from each other at the peripheral edge. Provided,
The combustion flame is adjusted so that the amount of acetylene gas is larger and the amount of oxygen gas is larger than the amount of oxygen gas before the heat deformation of the butt portion due to the combustion flame is started, and the pressure is increased. Is set smaller before heating deformation start than after heating deformation start,
In the heating step, the combustion flame is blown into the gaps between the end faces formed by the recesses.

  In the gas pressure welding method according to the present invention, the end surface of each structural steel material is formed so that the peripheral edge recedes in a taper shape from the center to form the concave portion.

  In the gas pressure welding method according to the present invention, the structural steel material is a rail for rail.

  In the gas pressure welding method according to the present invention, the rail for rail is a bainite rail, the gap dimension W of the gap is 1 to 5 mm at the end face edge, and the depth D from the end face edge of the gap is 5 The said recessed part is comprised so that it may be set to -15mm.

  In the gas pressure welding method according to the present invention, the rail for rail is a bainite rail, and the applied pressure is set to 15 to 20 MPa before the start of heat deformation and 22 to 25 MPa after the start of heat deformation.

  Further, the gas pressure welding method according to the present invention is such that the rail for railroad is a bainite rail, and the amount of acetylene gas in the combustion flame is 1.1 to 1.3 times the amount of oxygen gas before the heat deformation starts. 1.0 to 1.05 times after the start.

  In performing gas pressure welding, it has been conventionally known that the oxide formed at the butt portion can be decomposed and removed by the reduction action of carbon in the structural steel material or carbon of acetylene, but on the other hand, the amount of acetylene gas As described above, the oxide remains in the vicinity of the joint even when a combustion flame having a larger amount of oxygen gas than that is used, and as a result, it has been difficult to sufficiently suppress defects such as cracks.

  This is because the carbon supply to the vicinity of the butt is not sufficient, and it seems that the decomposition reaction of the oxide by the supplied carbon has not progressed to a sufficient extent. As a result of research and development focusing on how carbon can be supplied at a sufficient concentration and the decomposition reaction of the oxide can proceed to a sufficient extent, This is a new finding that the residual amount of oxide in the vicinity can be greatly reduced.

  That is, in the gas pressure welding method according to the present invention, when the structural steel materials are abutted at their end surfaces, at least one of the structural steel materials so that the respective end surfaces abut on the center and are separated from each other at the center. A concave portion is provided on the end surface of one structural steel material, and before the heat deformation of the butt portion by the combustion flame starts, the amount of acetylene gas becomes larger than after the heat deformation starts and becomes larger than the amount of oxygen gas. The combustion flame is adjusted as described above, and in the heating step, the combustion flame is blown into the gaps between the end faces formed by the recesses described above.

  In this way, before the start of heat deformation, the combustion flame spreads widely in the gap, and surplus acetylene carbon contained in the combustion flame is supplied in the vicinity of the butt portion at a high concentration.

  In addition, when heating with the combustion flame, the pressure in the material axis compression direction applied to the structural steel material is set to be smaller before the start of heating deformation than after the start of heating deformation.

  In this case, since the pressure applied to the structural steel material is small, the start of heat deformation in the vicinity of the butt location is delayed, and accordingly, the heating time becomes longer and the temperature in the vicinity of the butt location increases.

  Therefore, even if an oxide is generated in the vicinity of the butt portion in the heating process, such an oxide is reliably and in a short time due to a synergistic effect of carbon supply at a high concentration through the gap and acceleration of the reaction due to temperature increase. Reduced and promptly decomposed and removed.

  In addition, by reducing the pressure applied to the structural steel material before the start of heat deformation, it becomes possible to delay the timing at which the structural steel materials adhere to each other at each end face, so that the oxide is decomposed and removed in the vicinity of the butted portion This time can be secured sufficiently.

  On the other hand, after the start of the heat deformation, the heat deformation in the vicinity of the abutting portion is promoted by increasing the pressure force before the start of the heat deformation.

  In this way, the heating time after the start of the heat deformation is shortened by the amount that the speed of the heat deformation is increased, and it is possible to avoid the surface melting of the butted portion due to an excessive temperature rise.

  The concave portion provided on the end surface of the structural steel material does not necessarily have to be provided over the entire circumference of the end surface, and may be provided only in part.

  Further, such a recess has any configuration as long as a gap is formed between each end surface of the structural steel material when the two structural steel materials are brought into contact with each other. It may be provided only on steel.

  As a specific example of the concave portion provided on the end surface of the structural steel material, for example, the end surface of each structural steel material can be formed so that the peripheral edge recedes in a taper shape from the center, and this can be used as the concave portion.

  Although structural steel materials include rails and reinforcing bars, especially when these structural steel materials are railroad rails, a safer track is constructed regardless of the level of proficiency of workers engaged in gas pressure welding. It becomes possible to do.

  When the end surface of each structural steel material is formed so that the peripheral edge recedes in a taper shape from the center, and this is used as a recess, the separation size and depth of the gap formed by the recess are arbitrary, and What is necessary is just to determine suitably according to the steel grade and cross-sectional shape of the structural steel material which becomes, If the rail for railroads is a bainite rail, the separation dimension W of the gap between each end surface formed by the concave portion is 1 to 1 at the end surface edge. What is necessary is just to comprise a recessed part so that 5 mm and the depth D from the edge surface edge part of a space | gap may be 5-15 mm.

  The clearance dimension and depth of the gap are set in the above-mentioned range because when the gap separation dimension W exceeds 5 mm or when the gap depth D exceeds 15 mm, the concave portion becomes excessive, and the end surface provided with the concave portion is provided. In this case, the degree of compressive deformation of the bainite rail is insufficient, and if the gap separation dimension W is less than 1 mm or the gap depth D is less than 5 mm, the space for injecting the combustion flame becomes too small, and the sufficient concentration. This is because it becomes difficult to supply carbon to the butted portion.

  The amount of pressure reduction before the start of heat deformation relative to the start of heat deformation increases the temperature at the butt portion as the heating time of the process becomes longer, and the temperature increase promotes the decomposition reaction of oxides by carbon. As long as it is set, the size is arbitrary and may be determined as appropriate according to the steel type and cross-sectional shape of the target structural steel material. The applied pressure may be 15 to 20 MPa before the start of heat deformation and 22 to 25 MPa after the start of heat deformation.

  The reason why the pressure applied before the start of the heat deformation is 15 to 20 MPa is that if it is less than 15 MPa, the start of the heat deformation is too late and may cause an excessive temperature rise, and if it exceeds 20 MPa, the start of the heat deformation is too early. This is because the temperature suitable for promoting the decomposition reaction of the oxide is not reached.

  Moreover, the reason why the applied pressure after the start of the heat deformation is set to 22 to 25 MPa is that if it is less than 22 MPa, the heat deformation speed is too slow, and there is a concern that the temperature rises excessively and consequently the surface melts at the butt portion. If it exceeds, the heating deformation speed is too fast and good pressure welding is not performed.

  As long as the acetylene gas amount in the combustion flame is configured so as not to cause an excessive temperature rise after the start of the heat deformation so that a sufficient concentration of carbon is supplied to the abutting location before the start of the heat deformation. The value to be set is arbitrary and may be appropriately determined according to the steel type and cross-sectional shape of the target structural steel material. If the rail for rail is a bainite rail, acetylene in the combustion flame The gas amount is preferably 1.1 to 1.3 times the amount of oxygen gas before the start of heat deformation and 1.0 to 1.05 times after the start of heat deformation.

  The reason why the amount of acetylene gas before the start of heat deformation is 1.1 to 1.3 times the amount of oxygen gas is that if the amount is less than 1.1 times, sufficient concentration of carbon cannot be supplied to the butted portion. If it exceeds 1.3 times, the flame tip of the combustion flame approaches the surface of the structural steel material and there is a concern that the temperature rises excessively and consequently the surface of the butted portion is melted.

  The reason why the amount of acetylene gas after the start of heat deformation is set to 1.0 to 1.05 times the amount of oxygen gas is that when less than 1.0, a flashback phenomenon occurs, exceeding 1.05 times. This is because there is a concern of causing significant surface melting in the final stage of the gas pressure welding operation.

The flowchart which showed the implementation procedure of the gas pressure welding method which concerns on this embodiment. It is the figure which showed the rails 1 and 1 which are joining objects, (a) is a whole side view, (b) is an arrow view seen from the AA line direction, (c) is seen from the BB line direction. Arrow view. It is the figure which showed the state which matched the rails 1 and 1 by the end surfaces 2 and 2, (a) is a side view, (b) is a detailed figure.

  Embodiments of a gas pressure welding method according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a flowchart showing an implementation procedure of the gas pressure welding method according to the present embodiment. As shown in the figure, in the gas pressure welding method according to this embodiment, first, as shown in FIG. 2, the end surfaces 2 and 2 of the two rails 1 and 1 as the structural steel materials to be joined to each other are formed. Recesses 5 are respectively formed (step 101).

  The recess 5 is formed so that the end surface 2 of the rail 1 for railroads recedes in a taper shape from the center 3 where the peripheral edge 4 extends inward, and when forming the recess 5, for example, when performing a grinding operation The peripheral edge 4 may be tapered while finishing the center 3 smoothly.

  Next, as shown in FIG. 3, the two rails for rails 1, 1 are butted at their end surfaces 2, 2 (step 102).

  In this way, the end surfaces 2 and 2 of the rails 1 and 1 are brought into contact with each other at the centers 3 and 3 and are separated from each other at the peripheral edges 4 and 4. A gap 11 in which 5 and 5 are integrated is formed in a groove shape.

  When the rails 1 and 1 for railway are bainite rails, the clearance 11 is preferably 1 to 5 mm at the end edge and a depth D from 5 to 15 mm from the end edge. The recesses 5 and 5 are formed so as to have such dimensions.

  Next, while applying a pressing force in the material axis compression direction to the rails 1 and 1 for railroads, those butt portions are heated with a combustion flame composed of oxygen gas and acetylene gas. During heating, a combustion flame is blown into the gap 11 between the end surfaces 2 and 2 formed by the recesses 5 and 5 (step 103).

  Here, the combustion flame is adjusted so that the amount of acetylene gas is larger and the amount of oxygen gas is larger than the amount of oxygen gas before the start of the heat deformation of the butted portion by the combustion flame, If the rail 1 is a bainite rail, the amount of acetylene gas in the combustion flame is preferably 1.1 to 1.3 times the amount of oxygen gas before the start of heat deformation.

  Further, the pressing force in the material axis compression direction to be applied to the rails 1 and 1 is set to be smaller than after the start of the heat deformation before the start of the heat deformation, and if the rail 1 for the rail is a bainite rail, It is good to set it as 15-20 Mpa before a heat deformation start.

  When the combustion flame is blown into the gap 11 with the conditions set in this manner, the combustion flame spreads widely in the gap 11 before the start of heat deformation, and the excess acetylene carbon contained in the combustion flame has a high concentration. Since it is supplied to the vicinity of the butt location and the applied pressure is small, the start of heating deformation in the vicinity of the butt location is delayed, and accordingly, the heating time becomes longer and the temperature near the butt location increases.

  On the other hand, after starting the heat deformation, the pressure is increased and the amount of acetylene gas is reduced. If the rail 1 for rail is a bainite rail, the pressure is 22 to 25 MPa, and the amount of acetylene gas in the combustion flame is oxygen gas. The amount is preferably 1.0 to 1.05 times the amount.

  In this way, the applied pressure becomes larger than before the start of the heat deformation, so that the heat deformation near the butt location is promoted, the speed of the heat deformation is increased, the heating time is shortened, and the excessive temperature rise The surface melting of the butt portion is avoided in advance.

  As described above, according to the gas pressure welding method according to the present embodiment, the excess acetylene carbon contained in the combustion flame is supplied at a high concentration in the vicinity of the butted portion before the heating deformation starts, and the heating time is long. Thus, the temperature in the vicinity of the butt increases.

  Therefore, even if an oxide is generated in the vicinity of the butt portion in the heating process, the oxide is reliably and for a short time due to the synergistic effect of the carbon supply at a high concentration through the gap 11 and the promotion of the reaction due to the temperature rise. Thus, it is possible to quickly decompose and remove, and thus it is possible to reliably prevent the occurrence of defects such as cracks at the gas pressure welded joint.

  Further, by reducing the pressure applied to the rails 1 and 1 before the start of heat deformation, the timing at which the rails 1 and 1 are brought into close contact with each other at the end surfaces 2 and 2 is delayed. It is possible to secure a sufficient time for decomposing and removing the object.

  In addition, according to the gas pressure welding method according to the present embodiment, since the applied pressure is increased after the start of the heat deformation, the heat deformation in the vicinity of the butt portion is promoted, and the heating deformation speed is increased, so that the heating time is increased. In combination with the reduction in the amount of acetylene gas, it becomes possible to avoid the surface melting of the butt portion due to an excessive temperature rise.

  Next, since the verification test of the gas pressure welding method according to the present invention was conducted, an outline thereof will be described below.

  First, a JIS-60kg bainite rail gas pressure test specimen was prepared, and a magnetic particle flaw detection test using an interpolar magnetizer and fluorescent magnetic powder was performed on the test specimen, so that flaws (defect magnetic powder pattern) were generated. investigated.

Table 1 shows the production conditions of the gas pressure contact specimen and the results of the magnetic particle flaw detection test.

  As can be seen from the table, the test body No. 1 is a conventional gas which is heated without changing the amount of acetylene gas and the applied pressure in the combustion flame before and after the start of heating deformation and without forming a gap on the end face. It is a pressure contact test body (comparative example).

  As a result of the test, a defective magnetic powder pattern was confirmed at a portion from the upper corner of the rail to the head side. Here, the upper corner of the head is the upper corner of the rail head, the head side is the side of the rail head, the top of the rail head described later is the upper surface of the rail head, and the chin of the rail head is It means the lower corner of the rail head (see FIG. 2 (b)).

  Specimen No. 2 uses 1.14 times the amount of acetylene gas relative to the amount of oxygen gas in the combustion flame before the start of heat deformation, 1.04 times after the start of heat deformation, and the applied pressure is 16.8 MPa before the start of heat deformation. This is a test body in which gas pressure welding is performed by providing a gap of 24 MPa after the start of heat deformation, a separation dimension W of 2 mm, and a depth D from the end surface edge of 10 mm on the end surface. Hereinafter, the production conditions of the specimen No. 2 are referred to as Example 1.

  Based on the results of the comparative example, the gap was formed in a region from the chin of the rail head to the head side and the chin on the opposite side through the head side and the top of the head so as to surround the head of the rail.

  As a result of the test, no defective magnetic powder pattern was confirmed, and it was found that the gas pressure contact was good.

Next, from the preparation conditions of the test body No. 2 (Example 1),
(a) Formation of gap
(b) Increase in the amount of acetylene gas before the start of heat deformation
(c) Test specimens prepared by excluding the three steps of reducing the applied pressure before the start of heating deformation one by one were prepared as specimen No. 3, specimen No. 4, and specimen No. 5, respectively. That is, specimen No. 3 was produced by making the production conditions identical to Example 1 except that no gap was formed (Example 2), and specimen No. 4 was made of acetylene gas before the start of heat deformation. Except that the amount was not increased, the production conditions were the same as in Example 1 (Example 3), and specimen No. 5 was produced under the conditions except that the pressure was not reduced before the start of heat deformation. Is made in accordance with Example 1 (Example 4).

  As a result of testing these, in specimen No. 3, a defective magnetic powder pattern was confirmed in the part (both sides) from the upper corner of the head to the head side, and in specimen No. 4, the upper corner of the head (both sides) and the head. A defective magnetic powder pattern was confirmed on the partial chin (one side), and a defective magnetic powder pattern was confirmed on the head side (one side) in specimen No. 5.

  In each of these, the carbon supply became insufficient because no gap was formed, the carbon concentration decreased because the amount of acetylene gas was not increased, and the sufficient pressure was not reached because the applied pressure was not reduced. This seems to be the cause.

  Next, when the specimen No. 6 was produced by making the production conditions the same as in Example 1 except for the gap depth D (Example 5), a defect magnetic powder pattern was confirmed on the head side (both sides).

  This may be due to the lack of carbon supply due to the shallow gap.

  Next, except that the amount of acetylene gas with respect to the amount of oxygen gas before the start of heat deformation was increased, the production conditions were made to match those of Example 1 (Example 6), and an attempt was made to produce specimen No. 7. Since overmelting occurred, the production operation was stopped.

1 Railway rails (steel for construction)
2 End face 3 Center of end face 4 Edge edge 5 Recess 11 Gap

Claims (6)

Two structural steel materials are abutted at their end faces, and the abutting portions are heated by a combustion flame composed of oxygen gas and acetylene gas while applying a pressing force in the axial direction of the material to the structural steel material. In the gas pressure welding method for joining two structural steel materials to each other,
When the structural steel materials are abutted at their end faces, a concave portion is formed on the end face of at least one of the structural steel materials so that the end faces are in contact with each other at the center and separated from each other at the peripheral edge. Provided,
The combustion flame is adjusted so that the amount of acetylene gas is larger and the amount of oxygen gas is larger than the amount of oxygen gas before the heat deformation of the butt portion due to the combustion flame is started, and the pressure is increased. Is set smaller before heating deformation start than after heating deformation start,
In the heating step, the gas pressure welding method is characterized in that the combustion flame is blown into a gap between the end faces formed by the recess. The gas pressure welding method according to claim 1, wherein the end surface of each structural steel material is formed so that the peripheral edge recedes in a taper shape from the center to form the concave portion. The gas pressure welding method according to claim 1 or 2, wherein the structural steel material is a railroad rail. The rail is a bainite rail, and the concave portion is configured such that the gap separation dimension W is 1 to 5 mm at the end face edge and the depth D from the end face edge of the gap is 5 to 15 mm. The gas pressure welding method according to claim 3. The gas pressure welding method according to claim 3, wherein the rail for railroad is a bainite rail, and the applied pressure is set to 15 to 20 MPa before the start of heat deformation and 22 to 25 MPa after the start of heat deformation. The rail for railroad is a bainite rail, and the amount of acetylene gas in the combustion flame is 1.1 to 1.3 times the amount of oxygen gas before the start of heating deformation, and 1.0 to 1.05 times after the start of heating deformation. The gas pressure welding method according to claim 3.

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