A nose type rail member for a crossing member applied to a turnout or wayside switch system on the ground for a train and the like, is made of high carbon steel material containing 0.70 to 0.82 wt. % of carbon. The rail member is constructed by a pair of rail parts, which have a concave at a side of the middle support part. A backing plate is made of the same material as the rail member, or a steel material having a less carbon content than that of the rail member, and is held by a pair of the opposite concaves. A pair of the head portions and the base portions at a side thereof are joined by means of electron beam welding, and the joined rail member is subjected to S.Q. heat processing; whereby at least a wheel tread of the rail member becomes a homogeneous and fine pearlite structure.

FIELD OF INVENTION 
     This invention relates to a nose type rail member used for crossing at a rail turnout, a method for manufacturing the same and a welded crossing using said nose rail. 
     THE PRIOR ART OF INVENTION 
     The crossing for a railway turnout is a wayside switch system of rolling stock track on the ground, which comprises a nose rail in which the head branches into two, and an integrated head runs in a line in the longitudinal direction with a wing rail on the side thereof. Traditionally, solid manganese steel crossings with high manganese cast iron and welded crossings with carbon steel are used. The former has the advantage of being abrasion resistant, tough and durable. However, it is difficult to weld the front and back ends in the longitudinal direction which are joined with the wayside rail, and it is necessary to join them with fish plates, resulting in faults in the joint. On the other hand, the latter crossing has the advantage of having no joint missing line because the front and back ends can be welded. However, in the case of consumable electrode welding (shielded arc welding, MAG welding end the like), since medium carbon steel, which contains a limited amount of carbon (C:0.33-0.38%) is usually used in view of the welding property, Cr, Mo, B and the like are added, resulting in the disadvantage that abrasion and settling occur around the transferring point more easily than high carbon steel treated with heat and high manganese steel. Since it is difficult to weld the parts having a narrow head width in the front parts of the nose rail, the material formed and processed by rolling or casting rails having a thick stem and a specific cross section must be used, resulting in the disadvantage of high production cost. 
     Anyway, at present, it is desired to enhance the rate of the train and reduce the noise, therefore, there is a need not only to eliminate joint missing line as thoroughly as possible in the turnout, but also to enhance abrasion resistance and durability of the members used. Traditional solid manganese steel crossings and welded crossings have not been satisfactory. 
     A welded crossing is known which can solve the above-mentioned problem, and is disclosed in Japanese Patent Unexamined Publication No. 1-97093. However, also in this welded crossing, wire used for the head of the nose rail is very expensive and the chemical composition of the high carbon steel varies with use such as NHH rail, DHH340 rail and DHH370 rail, and therefore uneconomically, different wire must be used for every chemical composition of the kind of rail in order that deposited metal parts should have the same SQ process ability as the base metal rail; thereby having further room for improvement. 
     In the case of TIG welding using filler wire as added hot charge, U-shaped narrow beveling in the order of 8-10 mm is required. Moreover, because of multilayer welding, in spite of the low heat input, the welding distortion is large end a restricting means is complicated, resulting in a lot of trouble and high costs; thereby also having room for improvement. 
     OBJECTS OF THE INVENTION 
     In view of above-mentioned traditional technical subject, it is an object of the invention to provide a welded nose rail for crossing which has the advantage of having no joint missing line with the front and back ordinary rail, which is the advantage of the welded crossing, and can enhance abrasion resistance and durability, which are the disadvantage thereof. 
     It Is an another object of the present invention to provide a welded nose rail for crossing with which welding and beveling is easy and which requires no wire, and can eliminate distortion by heat effect and a process of producing the same. 
     SUMMARY OF THE INVENTION 
     The present invention provides a nose rail for a crossing used at a railway turnout on the ground, in which a pair of rail members are joined at their side faces with the head branching into two and the integrated head running in a line, characterized in that; 
     said pair of rail members consist of high carbon steel containing 0.70 to 0.82% by weight of carbon and have facing cavities, which form a hollow holding backing material, at the stem point of the joint side face; 
     said backing material is the same steel as or steel containing a lower amount of carbon than said high carbon steel and held in the hollow so as to contact the hollow side end of the vertical joint of said head and base parts; 
     said integrated head part of said pair of rail members and the corresponding base part are directly joined with each other at least by electron beam welding; 
     the tread of the nose rail has a homogeneous fine pearlite structure. 
     Said pair of rails have a joint side face as a symmetry plane and are roughly divided into one group in which the rails are linearly symmetric with each other and the other group comprising a long nose rail and a short one. 
     And the present invention provides a method of producing the welded nose rail for crossing, which comprises: 
     joining head parts of a pair of rails with each other directly by electron beam welding, and 
     heat processing the whole head part of said pair of rails by slack quenching. Said slack quenching type heat processing is preferably conducted after electron beam welding, but may be conducted before electron beam welding. 
     The first process of the present invention is to produce a nose rail for crossing used at a railway turnout on the ground in which a pair of rail members are joined at their side faces, with the head branching into two and the integrated head running in a line, characterized in that: 
     said pair of rail members consist of high carbon steel containing 0.70 to 0.82% by weight of carbon and have facing cavities, which form a hollow holding backing material, at the stem point of the joining side face; 
     the head parts to be integrated of said pair of rail members are welded to the corresponding base parts by electron beam welding; and then 
     the rail is treated by slack quenching type heat processing, resulting in a high carbon steel rail with at least the tread of the nose rail having an almost homogeneous fine pearlite structure. 
     The second process of the present invention is to produce a nose rail for a crossing used at a railway turnout on the ground in which a pair of rail members are joined at their side faces, with the head branching into two and the integrated head running in a line, characterized in that: 
     said pair of rail members consist of high carbon steel containing 0.70 to 0.82% by weight of carbon and have facing cavities, which form a hollow holding backing material, at the stem point of the joining side face; 
     the rail is treated by slack quenching type heat processing, resulting in a high carbon steel rail member having a homogeneous pearlite structure; and then 
     the head parts to be integrated of said pair of rail members are welded to the corresponding base parts by electron beam welding. 
     As a method which conducts S.Q heat processing continuously, a method ( see Japanese Patent Publication No. 63-65735) can be used in which the head part of the rail is heated evenly with a heating device comprising a top face heating burner, of which the width of the flame can be adjusted depending on the width of the head of the rail, and a side face heating burner, which can move back and forth depending on the width of the head part of the rail, while said head part of the rail is cooled at a prescribed rate with a cooling device comprising a top face cooler, of which the width of the injection band of the cooling air can be adjusted depending on the width of the head of the rail, and a side face cooler, which can move back and forth depending on the width of the head part of the rail and inject cooling air and water. Thus, the desired abrasion resistance and fatigue resistance being obtained. However, since this method does not adequately consider the structural property of the nose rail for crossing wherein the front head part is integrated by welding and the back head part branches into two, in the case of heat processing the back head part of the rail branching into two by S.Q heat processing, a large processing device must be used and the width of the flame band and the cooling air injecting band must be equal to the whole width of the opening of the head part of the rail branching into two, therefore, the heating and cooling efficiency may be poor. 
     Then, according to the present invention, the continuous S.Q heat processing of the head of the nose rail for a crossing comprises heating and cooling the nose rail for the crossing having a structure in which the front is integrated by welding and the back has a head shape branching into two, and said heating process preferably comprises: arranging a pair of laterally spaced heating burners, each of which consists of plural device heads, above the head part of the nose rail; moving said heating burners and the nose rail relatively; moving said pair of heating burners in the direction of the head width varying with the longitudinal center line of the nose rail and rotating them at the opening angle of the head; adjusting the flame band by igniting and extinguishing plural craters of each device head; and controlling the flame strength of each device head to the proceeding direction by adjusting the flow of gas. 
     According to the present invention, the continuous S.Q heat processing of the head of the nose rail for crossing comprises heating and cooling continuously the nose rail for a crossing having a structure in which the front is integrated by welding and the back has a head shape branching into two and said cooling process preferably comprises: arranging a pair of laterally spaced coolers, each of which consists of plural air tanks, over the top face and side face of the head part of the nose rail; moving said coolers and the nose rail relatively; moving said pair of coolers in the direction of the head width varying with the longitudinal center line of the nose rail and rotating them at the opening angle of the head; controlling the cooling ability of the air shower with the compressed air within each air tank to the proceeding direction by adjusting the flow of air. 
     The head part of the nose rail has one front end with a sharp shape, the width of the head becoming larger towards the rear, then the head branching into two, the resulting two rails expanding to the back end, with the result that the cross section of the head changes. Therefore, S.Q heat processing may be conducted after half-processing the front head part of the nose rail, which is integrated by welding and to be heat processed, into the maximum volume of size and shape which can satisfy the heat processing quality of the product. 
     The back part of the nose rail, which branches into two, may have the parts below the jaw of the head covered with protecting plates and the like in order that the only head part of the rail can be heated or cooled by flame of the burner and air shower, respectively. 
     The head part of the nose rail from the top and half-processed to the back and branching into two is continuously heated to the desired temperature distribution. However, at least the welded head part having a large volume may preferably be preheated wholly to 300°-500° C. with an electric furnace and the like. 
     In cooling, the whole rail from the top and to the point branching into two and the head part of the rail behind the point branching into two may be cooled to below 300° C. with an air shower. 
     Moreover, the method of welding the nose rail, for example, EBW method or pressure welding method, may preferably be a method requiring no added hot charge, because the chemical composition of the weld metal are almost the same as the base metal, in comparison with the welding method requiring added hot charge. 
     According to the nose rail of the present invention, a welded crossing integrating said nose rail and the wing rail can be assembled by welding the base part of said nose rail to the base part of said wing rail, which is a high carbon steel rail comprising high carbon steel containing 0.70 to 0.82% by weight and having an even pearlite structure obtained by slack quenching type heat processing, and fastening a bolt and nut through the filler. 
     According to the present invention, the chemical composition of the weld metal is almost the same as the base metal rail and the material of a pair of rails is high carbon steel containing 0.70˜0.82% by weight of carbon, and therefore, the welded part may have a fine pearlite structure and some pearlite structure by welding under the conditions considering the appropriate preheating temperature and welding heat input, resulting in the tread of the rail with both of the whole head parts welded having a substantially homogeneous fine pearlite structure. Moreover, in the case that the rail material is not previously heat processed by slack quenching, if the head part of the nose rail welded by electron beam Is heat processed by slack quenching, the tread of the nose rail may have a homogeneous fine pearlite structure. 
     When electron beam welding is used, the shape of the bevel may be an I-shaped bevel which can be processed most easily and the weld penetration can be very deep, with the result that one-pass rapid joining is possible. Automatic welding can also be used. Moreover, since the heat input per unit of plate thickness as well as the total heat input is smaller than that according to other welding methods, the width of the weld metal and the part influenced by heat is narrow and the deformation caused by the welding distortion is very small. 
     With the use of the backing material, the spike and cold shut, which are welding defects peculiar to the electron beam welding, can be absorbed by said backing material, and therefore, the welded part of the base material may be sound. 
    
    
     BRIEF DESCRIPTION OF DRAWING 
     FIGS. 1(a) and 1(b) illustrate the whole planer structure of the welded nose rail for crossing of Example 1 produced according to the process of the present invention and the central section of said nose rail. 
     FIG. 2 is a cross-sectional view taken on line A--A˜D--D of the nose rail shown in FIG. 1. 
     FIG. 3 is a cross-sectional view taken on line E--E of the nose rail shown in FIG. 1. 
     FIG. 4 is a cross-sectional view taken on line F--F of the nose rail shown In FIG. 1. 
     FIG. 5 is a cross-sectional view taken on line G--G of the nose rail shown in FIG. 1. 
     FIG. 6 is a plan view illustrating the whole welded nose rail for crossing of Example 2 produced according to the process of the present invention. 
     FIG. 7 is a cross-sectional view taken on line A--A of the nose rail shown in FIG. 6. 
     FIG. 8 is a cross-sectional view taken on line B--B of the nose rail shown in FIG. 6. 
     FIG. 9 is a cross-sectional view taken on line C--C of the nose rail shown in FIG. 6. 
     FIG. 10 is a cross-sectional view taken on line D--D of the nose rail shown in FIG. 6. 
     FIG. 11 is a cross-sectional view illustrating the welded crossing using the nose rail shown in FIG. 6. 
     FIG. 12 is a plan view illustrating the whole nose rail for welded crossing of Example 3 produced according to the process of the present invention. 
     FIG. 13 is a cross-sectional view taken on line A--A of the nose rail shown in FIG. 12. 
     FIG. 14 is a cross-sectional view taken on line B--B of the nose rail shown in FIG. 12. 
     FIG. 15 is a cross-sectional view taken on line C--C of the nose rail shown in FIG. 12. 
     FIG. 16 is a cross-sectional view taken on line D--D of the nose rail shown in FIG. 12. 
     FIGS. 17a and 17B illustrates schematically the whole steps of continuous slack quenching heat type processing of the head part of the nose rail for crossing according to the example of the present invention. 
     FIG. 18 is a plan view illustrating the front part of said nose rail for crossing. 
     FIG. 19 is a cross-sectional view taken on line A--A of the rail shown in FIG. 17. 
     FIG. 20 is a cross-sectional view taken on line B--B of the nose rail shown in FIG. 17. 
     FIG. 21 is a cross-sectional view taken on line C--C of the nose rail shown In FIG. 17. 
     FIG. 22 is a cross-sectional view taken on line D--D of the nose rail shown in FIG. 17. 
     FIG. 23 is a cross-sectional view taken on line E--E of the nose rail shown in FIG. 17. 
     FIG. 24 is a cross-sectional view taken on line F--F the nose rail shown in FIG. 17. 
     FIGS. 25A-C illustrates in side elevation, (FIG. 25A) in vertical elevation (FIG. 25B) and in bottom (FIG. 25C) the heating burner used in said continuous slack quenching type heat processing of the head part. 
     FIGS. 26A-C illustrates in side elevation, (FIG. 26A) in vertical elevation (FIG. 26B) and in bottom (FIG. 26C) the cooler used in said continuous slack quenching type heat processing of the head 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be apparent from a reading of the following description in connection with the embodiment shown in the accompanying drawings. 
     EXAMPLE 1 
     FIGS. 1 (A) and (B) are plan views illustrating the whole welded nose rail for crossing of Example 1 produced according to the method of the present invention and a longitudinal central section view of said nose rail, respectively. 
     In this example, a pair of rail members 1 having the same cross section as an ordinary rail are used and joined with each other to be symmetric with respect to the longitudinal dinal center line. The material is a high carbon steel rail material containing 0.70 to 0.82% by weight of carbon. Electron beam welding is used to join said rails and the backing material 2 extending in the longitudinal direction is interposed at the stem point of said pair of rail members 1, 1. Said backing material 2, as shown in FIG. 1B, has a narrow width from the front point A to the bending point D--D and a larger width as from the bending point to the back. The top and bottom and parts of the backing material 2 extend from the hollow stem part 1c of the rail members 1, 1 to the joint of the head part 1a and the joint of the base part 1b, and is contacted to or held between them. At the point G--G where the rail members 1, 1 branch into two, the backing material 3 is contacted to the only joint of the base part 1b of the rail member 1 and extends in the longitudinal direction. On the other hand, the I-shaped bevel is formed at the joint of the head part 1a and base part 1b of said rail member 1 and the electron beam welding is conducted along the bevel extending on the longitudinal center line. 
     Said electron beam welding is usually conducted according to the following work flow. 
     The whole face of the bevel of the rail and the part around it are degreased and cleaned, and then, a pair of rails and a backing material are constructed and fixed with a jig, the whole being preheated to 400° C. in the preheating furnace. Immediately after preheating, the resulting rail is carried into the welding chamber of the electron beam welding device with the joint of the base up and electron beam welding is conducted under the conditions that the degree of vacuum within said welding chamber is over 5*10-4 Torr, the temperature of the rail is within the range of 300° to 350° C., and the welding heat input per unit of the plate thickness is 7-10 KJ/cm2. Air is taken into the welding chamber 10 minutes after the completion of welding, and then the whole is preheated to 400° C. to weld the joint of the head part of the rail, welding being conducted under the same conditions as those in the case of the base joint. Immediately after that, the whole is heated to 450° C.-550° C. in the electric furnace as post heating. Then the welding finishes. 
     Moreover, the head part 1a of the joined nose rail is heat processed by slack quenching. In the slack quenching type heat processing, the welded nose rail is put in the preheating furnace and heated to about 500° C. And then, the head part of the V-shaped nose rail is heated to about 1000° C. and cooled slowly by injecting compressed air. The tread of the nose rail which is heat processed has a homogeneous fine pearlite structure. 
     The slack quenching type heat processing is conducted in the above-mentioned example, however, a high carbon steel material before welding at the head part 1a may be one which is preliminary heat processed by slack quenching and have a homogeneous fine pearlite structure. In such a case, even if the nose rail 1 welded by electron beam has a small area which is thermally transformed into a pearlite structure around the welded part, the area is very narrow and almost the whole head part has a fine pearlite structure and forms a tread of the nose rail, with the result that the rail can be used without further processing. 
     FIG. 2 to FIG. 5 are transverse cross sectional views of the nose rail produced in this way taken on each point shown in FIG. 1. FIG. 2 is a cross-sectional view taken on line D--D at the bending point of the nose rail shown in FIG. 1 and each shape of the cross section taken on A--A, B--B or C--C, respectively shown in FIG. 1 is illustrated with two-dot chain line. FIG. 3 is a cross-sectional view taken on line E--E of FIG. 1 and FIG. 4 is a cross-sectional view taken on line F--F of FIG. 1. A pair of rails 1, 1 which are symmetric have the front parts where the head parts 1a as well as the base parts 1b are directly joined each other by electron beam welding. The backing material 2 is interposed between the stem parts 1c. The backing material 2 has the advantage of absorbing spike and cold shut peculiar to electron beam welding. At the back part past the bending point, as shown in FIG. 3 and FIG. 4, the hollow part appears between the stem parts 1c. The width of the hollow part increases as it goes backward. At the point on line G--G of FIG. 1, as shown in FIG. 5, only the base parts 1b are directly joined using the backing material by electron beam welding. 
     is described above, said backing material 3 can not only absorb spike and cold shut peculiar to electron beam welding but also minimize the necessary thickness of the bevel of the head part or the base part, and therefore, the thickness of the stem part of the front part of the nose rail can be increased, the welding heat input can be decreased, and the temperature of the base material rail can be prevented from increasing excessively. As a result, the cooling rate of the welded part by heat conduction to the parts around it immediately after welding can be controlled and a nose rail having a high strength can be obtained. 
     The welded nose rail 1 is welded with only the wing rail and base part 1b which are arranged on the both sides thereof, and the nose rail and the wing rail are combined through the filler with bolts and nuts, with the result that the integrated and fixed crossing is formed. In this case, the nose rail and the wing rail may be combined only with the filler and bolts. The welded crossing like this is welded to have no joint missing line with the ordinary rail at the front and back ends thereof and forms a turnout. 
     Example 2 and 3 described below are nose rails which use a long nose rail and a short nose rail. In view of the relation between the area where the wheel transfers between the wing rail and the nose rail on the basis of the structure of crossing, the welded part of the head part of the nose rail of this type is apart from the point where the impact load acts during the transfer. The part around said welded part is thermally converted into a pearlite structure, but the area is very narrow. Therefore, the rail which comprises the high carbon rail material containing 0.70 to 0.82% by weight of carbon as a rail material and is heat processed by slack quenching into having the head part with a homogeneous fine pearlite structure can be used well. Further, just like Example 1, the head part may be heat processed by slack quenching into having a homogeneous fine pearlite structure after the electron beam welding is completed. 
     EXAMPLE 2 
     FIG. 6 is a plan view illustrating the whole nose rail for welded crossing of Example 2 produced according to the method of the present invention. In this example, too, a pair of rails which have the same cross sectional shape as the ordinary rail are used, each of them comprising a long nose rail 10 and a short nose rail 11. The front end of said short nose rail is arranged at the bending point of the head part having a overall width of the long nose rail and they are symmetric with respect to the center line, with the result that they can be used as a nose rail for crossing of the compatible type. The rail material is a high carbon steel rail material containing 0.70 to 0.82% by weight of carbon. The long nose rail end the short nose rail 11 are directly joined by welding the head parts and the base parts continuously by curve and linear electron beam welding and the welded end part is treated with a tab plate. 
     FIG. 7 is a cross-sectional view taken on line A--A of the nose rail 1 shown in FIG. 6, FIG. 8 is a cross-sectional view taken on line B--B, FIG. 9 is a cross-sectional view taken on line C--C, and FIG. 10 is a cross-sectional view taken on line D--D. At the point of the front end part R of the short nose rail, as shown in FIG. 6 and FIG. 7, the backing material 4 extends from the center of the pair of rails, along the R part, to the bottom face of the head chin part and the top face of the base part. Then the tab plate 5 is used and the head parts 1a as well as the base parts 1b are directly joined to each other by curve and linear continuous electron beam welding. On the line B--B, as shown in FIG. 8, the backing material 4 is interposed between both stem parts 1c. Rearward from that point, as shown in FIG. 9 and FIG. 10, the hollow part appears between both stem parts 1c and the width of the hollow part increases as it goes backward. At the point on line D--D shown in FIG. 6, only base parts 1b, as shown in FIG. 10, are directly joined by electron beam welding using the backing material 4. 
     Like Example 1, the nose rail 1 of Example 2, FIG. 11, is welded with only the wing rail and base part 1b, which are arranged on the both sides thereof; the nose rail 1 and the wing rail 8 being combined through the filler 9a with the bolt 9b and the nut 9c, with the result that the integrated and fixed crossing is formed. The nose rail 1 and the wing rail 8 may be combined only with the filler 9a, bolt 9b and 9c. The welded crossing like this is welded not to have a joint missing line with the ordinary rail at the front and back ends thereof and forms a turnout. 
     EXAMPLE 3 
     FIG. 12 is a plan view illustrating the whole nose rail 1 for welded crossing of Example 3 produced according to the method of the present invention. In this example like Example 2, a pair of rails which have the same cross sectional shape as the ordinary rail are used, each of them comprising a long nose rail 12 and a short nose rail 13. The long nose rail 12 and the short nose rail 13 have the head parts joined directly by linear electron beam welding and the base parts by linear and curve electron beam welding. In the position where the front end of said short nose rail is arranged with respect to the long nose rail, the head part of the short nose rail is beveled from the point A--A ahead of the bending point C--C of the head part having a overall width of head part of the nose rail. The welded end can be eliminated at the point of the cross section A--A to B--B by finishing the head part of the nose rail after welding. While in the case of the base part, the welded end can be eliminated by finishing the base part of the nose rail after processing within the base of the short nose rail. 
     FIG. 13 is a cross-sectional view taken on line A--A of the nose rail 1 shown in FIG. 12, FIG. 14 is a cross-sectional view taken on line B--B and FIG. 15 is a cross-sectional view taken on line C--C. is shown in FIG. 12, 13 and 14, the stem part and the base part from the front end on line A--A to the point on line B--B of the short nose rail 13 is cut and removed with only the head parts 1a left. The base part 1b from the point on line B--B to the point on line C--C is cut and removed to be R-shaped with the head part 1a and the base part 1b left. At the point on line A--A and line B--B, only head parts 1a are directly joined using the backing material 6 by linear electron beam welding. The depth of the welding decreases gradually between the point on line B--B and the point on line A--A and the welding is completed. As shown in FIG. 15, the backing material 6 is interposed between the stem parts 1c in the back part from the bending point of the long rail on line C--C, and the head parts 1a as well as the base parts 1b are directly joined by electron beam welding. There is a hollow between the stem parts 1c. At the point on line D--D of FIG. 12 in the back part, as shown in FIG. 16, the long nose rail 12 and the short nose rail 13 have the symmetric cross section and the head parts 1a as well as the base parts 1b are directly joined using the backing material 6 by electron beam welding. 
     Like Example 1, the nose rail 1 of Example 3 is welded with only the wing rail and base part 1b, which are arranged on the both sides thereof; the nose rail and the wing rail being combined through the filler with the bolt and the nut, with the result that the integrated and fixed crossing is formed. The nose rail and the wing rail may be combined only with the filler, bolt and nut. The welded crossing like this is welded to have no joint missing line with the ordinary rail at the front and back ends thereof and forms a turnout. 
     The heat processing will be more clearly understood with reference to the following description taken in connection with the flow diagram illustrating the continuous S.Q heat processing of the head part of the nose rail for crossing according to an example of the present invention shown in FIG. 17. 
     FIGS. 17A and 17B (Section (a) illustrates S.Q heat processing of the integrated head part 1A of the nose rail 101. 
     FIGS. 17A and 17B (Section (b) illustrates S.Q heat processing of the head part 1B branching into two of the nose rail 101. 
     In the case of the S.Q heat processing according to this example, the S.Q heat processing is conducted continuously from the integrated head 101A of the front part of the rail 101 to the head 101B branching into two of the back part. When the integrated head part 101A is S.Q heat processed, both of the heating burner 102 and the cooler 103 are controlled to be closed. When the head part 101B branching into two is S.Q heat processed, both of the heating burner 102 and the cooler 103 are moved and rotated following the opening width and angle of the head part 101a of the rail. 
     The S.Q heat processing is conducted from the front and of the rail 101 to the back end and the opening between the two the rails increases as it goes backward from the branch part 101C, therefore, the flame of the heating burner 102 streams backward, with the result that the stream of the flame to the cooler 103 in the front part can be reduced. 
     The shield cloth (heat insulating material ribbon) is provided between the heating burner 102 and the cooler 103 to shut out the flame of the burner. 
     The whole area from the front end of the rail 101 to around the branch part 101C may be preheated to 300° C. to 500° C. with an electric furnace and the like, then the head part 1a of the rail may be heated and hardened with the heating burner 102, and the stem part 101b as well as the head part 101a of the rail may be cooled at the same time by an air shower, in order to obtain the deeper hardened layer. The whole welded part my be preheated, then the head part 101a of the rail may be heated and hardened with the heating burner 102, and not only the head part 101a but also the stem part 101b and the base part 101c of the rail may be cooled at the same time only with an air shower, in order to reduce the stress in the welded joint part during heating and cooling. The distortion occurring after the S.Q heat processing also can be reduced. 
     In the case that two rails 101 in the rear of the branch 101C of the nose rail are heated and cooled continuously at the same time, in order to prevent each whole rail and two rails from bending due to the break in the balance of heating and cooling, both sides of each rail 101 from the lower surface of the chin 101d to the upper surface of the base part 101c are covered with a protecting plate and only the head part 101a of the rail is heated and cooled. Therefore the balance of heating and cooling of each whole rail and two rails can easily be maintained, with the result that each rail can be prevented from bending in right and left directions and each of two rails on both sides can bend almost evenly in up-and-down directions. 
     FIG. 18 illustrates the shape 101A of the front head part of the nose rail 101. After the front part 101A of the nose rail is welded, the head is half-processed into having the maximum width and shape to satisfy surface hardness, cross section hardness, and effective hardened layer at the finish of the product, and therefore, S.Q heat processing conditions can be almost even over the whole length of the nose rail. 
     The processing rate can thus be kept constant. When heated, the integrated part 101A of the head can be prevented from being overheated by changing the width of the flame in response to the width of the head part. And when cooled, the head part of the rail can be cooled over the length thereof slowly at the required cooling rate by air shower, which can cool evenly, from the upper surface and the side surface. 
     FIGS. 19-21 are flow diagrams of S.Q heat processing of the integrated part 101A of the head of the nose rail. FIG. 19 is a cross-sectional view taken on line A--A of FIG. 17 and illustrates the cooling process at the point where the width of the head part of the nose rail 101 is 0 mm at the finish. The head part 101a of the rail is half-processed and the whole nose rail 101 is cooled by injecting the air shower from the cooler 103 to the upper surface and the side surfaces of the head part of the nose rail 101. 
     FIG. 21 is a cross-sectional view taken on line C--C of FIG. 17 and illustrates the heating process at the point where the welded nose rail 101 is not half-processed. The width of the flame band of the heating burner 102 is adjusted in response to the width of the head part 101a of the rail (see the hatching part 102a of the Figure) to prevent overheating. 
     FIGS. 22-25 illustrate the S.Q heat processing of the branch part 101B of the head part of the nose rail 101. FIG. 22 is a cross-sectional view taken on line D--D of FIG. 17 and illustrates the cooling process at the point in the rear of the branch 101C of the nose rail 101. The filling material 105 is provided between the head parts 101a of the rail at the branch point 101B. The rail from the chin part 101a of the head part on the outside of the rail to the upper face of the base part 101c is covered with the protective plate 106, and the air shower from the cooler is injected to the upper and side surfaces of the rail head part, with the result that the only rail head part 101a can be cooled. 
     FIG. 23 is a cross-sectional view taken on line E--E of FIG. 17 and illustrates the cooling process at the point where the nose rail 101 branches into two. The cooler 103 separates at the center and moves to above the head part 101a of the rails 101 on the both sides and rotates in response to the opening angle of the rail 101b. The air shower of the cooler 103 is injected from the upper surface of the head part 101a and the outside surface of the nose rail 101b, respectively, with the result that the only rail head 101a can be cooled. 
     FIG. 24 is a cross-sectional view taken on line F--F of FIG. 17 and illustrates the heating process at the point where the nose rail 101 branches into two. The heating burner 102 separates at the center and moves to above the head part 101a of the rails 101 on both sides and rotates in response to the opening angle of the rail 10lb. The rail head part 101a is then heated from each upper surface. The rail from the chin part 101d of the head part on the outside of the rail to the upper face of the base part 101c is covered with the protective plate 106, with the result that the only rail head 101a can be heated. 
     FIGS. 25A, B and C are a side elevation view, an elevation view and a bottom view of the heating burner, respectively. The heating burner 102 is a water cooled one. A lateral pair of heating burners 102 are constructed to be able to move horizontally in the direction of the width of the head part 101a of the nose rail, and rotate in the direction of the opening angle of the head parts and moved and rotated in response to the shape of the rail head part 101a by the drive. 
     The heating burner 102 has a pair of device heads 120 which are laterally symmetric. There are provided plural crater banks 121 in the device head 120 in the direction of the width of the rail head part and the flame band can be controlled by igniting and extinguishing remotely the crater bank. The flame strength of each device head 120 can be controlled by adjusting the gas flow of each device head 120. 
     There is provided a heating band burner 102 in the first half part in the proceeding direction of the rail and a soaking band burner 102 in the latter half part, resulting in the structure having two blocks. The heating band burner 102, at the beginning of the heating by the burner, raises the temperature around the surface of the rail head part 101a and heats rapidly to about 800°-900° C. with the neutral flame to increase the hardening-and-heating depth, while the soaking burner 102 provides uniform temperature dispersion by thermal diffusion after rapid heating, increases the hardening-and-heating depth by heat conduction, and heats to the required hardening temperature with reducing flame to prevent over-heating and decarburization around the surface, with the result that the deeper hardened layer can be obtained efficiently. 
     FIGS. 26A, B and C are a side elevation view, an elevation view and a bottom view of the cooler 103. The cooler 103 injects condensed air from an air compressor or a blower as an air shower to the rail head part 101a and is, like the heating burner, moved and rotated in response to the shape the rail head part 101a by the driver. 
     The cooler 103 has a pair of air boxes which are laterally symmetric and each air box 130 has a structure comprising an air box which injects an air shower from the upper surface and the outside surface of the rail head part 101a, the cooling ability of the air shower by the condensed air of each air box 130 being able to be controlled by adjusting the air flow of each air box 130. There is provided a partition plate 131 at the entrance of the cooler 103 to prevent the air shower injected from the air box 130 from flowing along the surface of the rail head part 101a to the heating burner 102, to prevent the part around the surface of the rail head part 101a heated and hardened from being cooled below the required cooling rate and to prevent the surface hardness and the cross section hardness around the surface from declining after the S.Q heat processing. 
     The cooler 103 in the first half cooling part in the proceeding direction of the rail cools the area having a temperature within the range of 800° to 500° C. slowly at the required cooling rate, in order that the rail head part 101a may have a fine pearlite structure. The temperature around the surface of the rail head part 101a becomes 300° C. by passing through said first half slow cooling zone. The interior of the rail head part 101a within the range of the tip to the branch 101b close to the rail head part 101a and the upper part of the stem 101b following it have a temperature over 300° C., therefore, further cooling is necessary to prevent softening of the hardened layer, that is, the part having a fine pearlite structure, by the interior heat. 
     In the case that the part of the nose rail 101 having a welded construction is cooled rapidly by water, large temperature stress occurs at the welded part, therefore, the latter half part of the cooling process is a rapid zone cooling by an air shower having a better cooling ability than the first half part, not only to suppress the temperature stress, but also to cool the whole nose rail below 300° C. efficiently. After that, the nose rail is air-cooled to the room temperature. 
     EFFECT OF INVENTION 
     As set forth hereinabove, according to the present invention, the base material of the nose rail is directly joined by electron beam welding without any added hot charge so that the chemical composition of the weld metal is almost the same as that of the base material. Therefore, the welded part has the same pearlite structure as the base material rail or a fine pearlite structure by welding under the conditions of the suitable preheating temperature and welding. Moreover, in the case of electron beam welding, the total heat input is small and the width of the part influenced by heat is very narrow, resulting in little residual stress and distortion after the welding. 
     According to the present invention, the whole part from the tip of the nose rail for a crossing having an integrated construction to the branch part, can be S.Q heat processed by heating and cooling in response to the size and shape of the head part. Therefore, there can be formed a hardened layer having a depth of 20 to 25 mm and a homogeneous pearlite structure, which has a good abrasion and fatigue resistance, over the whole surface of the nose rail for the crossing.