JP6492727B2 - Manufacturing method of thickened steel pipe - Google Patents

Description

  The present invention relates to a method of manufacturing a thickened steel pipe having a wall thickness increased as compared with a raw steel pipe.

  For example, some automotive parts such as torsion beams and exhaust mufflers are made of steel pipes with a constant wall thickness (hereinafter referred to as “steel pipes”), and the material pipes are widened (diameter expansion). Some are manufactured by performing. The thickness of the raw steel pipe decreases with the spread processing of the automobile parts manufactured from the raw steel pipe.

  Depending on the degree of thickness reduction, the design requirements related to the thickness of the automobile parts may not be satisfied, and in the worst case, cracks may occur in the diameter-expanded portion, and the desired automobile parts may not be manufactured. .

  As one of the methods to suppress such thinning that becomes a problem when molding automobile parts, the thickness of the part where the thinning of the material steel pipe after molding is predicted is preliminarily processed before the opening process is performed. It is known to increase the thickness of the steel pipe by increasing the thickness. If a thickened steel pipe with increased wall thickness can be easily pre-formed, it will be reduced to a thickened steel pipe by secondary processing that reduces the wall thickness of the thickened steel pipe, for example, widening, etc. Even if this occurs, it is possible to satisfy the design requirements regarding the thickness of the automobile part after the secondary processing.

  Patent Documents 1 to 3 disclose inventions in which a steel tube is manufactured by increasing the thickness of a material steel pipe by devising the shape of a tool used for cold mouth opening. In particular, in Patent Document 3, as a first step, a punch having a taper portion with a taper angle of 30 degrees or more and less than 60 degrees is inserted from one end of a metal tube and is thickened at one end portion of the tube. After forming the expanded portion, as a second step, the expanded portion obtained in the first step is inserted into a contracted tube mold having a taper portion and contracted to a predetermined diameter, so that a desired thickened portion is obtained. And an outer diameter of the thickened portion is the same as or substantially the same as the diameter of other portions, and an invention for manufacturing a metal tube easily and at low cost by cold working is disclosed.

JP 2007-275896 A JP 2004-291072 A JP-A-9-327723

According to the invention disclosed in Patent Literatures 1 to 3, it is true that {(t ₁ −t ₀ ) / t ₀ } × 100 () when the outer diameters before and after the flaring process are t ₀ and t _1. %), It is possible to suppress thinning in the vicinity of the pipe end of the thickened steel pipe in the widening process with a predetermined pipe expansion rate (diameter expansion rate) defined as “%”.

  However, according to the invention disclosed in Patent Documents 1 to 3, as disclosed in Patent Document 2, in order to form a thickened steel pipe with a large diameter expansion rate, for example, a diameter expansion rate of 50% or more, upsetting If squeezing is not performed while being processed or divided into multiple steps, the thinning at the pipe end of the thickened steel pipe will increase, and there is a risk that it will not form until the end and will break at the end of the pipe.

  In particular, according to the examination results of the present inventors, as in the invention disclosed in Patent Document 3, after the diameter expansion process is performed on the raw pipe, the diameter-reduction process is performed to manufacture the thickened steel pipe (a ) Only about 16% thickening is obtained in the longitudinal position from the pipe end in the thickened part, and the degree of thickening is not sufficient, (b) The pipe end of the thickened steel pipe is thinned (For example, about 2.7% thinning on the side of the weld and about 1.2% thinning on the base metal) There is a problem that there is concern about cracks at the end, and it has been found difficult to sufficiently increase the thickness of the material steel pipe to obtain a desired thickened steel pipe.

  The present invention has been made in view of such problems that the prior art has, and it is possible to sufficiently obtain a degree of thickness increase in the longitudinal direction position from the tube end in the increased thickness portion of about 27% or more, It is to provide a method of manufacturing a thickened steel pipe by reducing the thinning at the pipe end.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention, unlike the method disclosed by Patent Document 3, increased the thickness by performing diameter expansion processing after performing diameter reduction processing on the raw tube. Manufacturing steel pipes, specifically, reducing the diameter of steel pipes at a specified reduction ratio using a narrowing tool (diameter reduction tool) that is cold and has a large taper angle and does not buckle the original pipe. After that, by using a squeezing tool (diameter expansion tool) having a sizing ratio approximately the same as this squeezing ratio, the squeezed material steel pipe is subjected to a sizing process, so that the pipe in the thickened part The thickness increase at the longitudinal position from the end can be sufficiently obtained to be about 27% or more, and the increased thickness steel pipe can be manufactured by reducing the thickness reduction at the end of the pipe. If secondary processing (spreading processing) is performed at a rate of 80% or more, it is the best compared to that formed from a steel tube. It can be suppressed thinning at the ends, and finding that it is possible to mold not cracked, and completed the present invention by overlapping a further study.

The present invention, on one end of the material steel, Te - Te with path angle is less than 30 degrees - the curvature of the path section radius by inserting a mouth aperture tool is 20mm or more, inserting the core metal into the material steel pipe The intermediate steel pipe corresponds to one end of the raw steel pipe after the intermediate steel pipe is manufactured by reducing the diameter of the raw steel pipe at a predetermined reduction ratio without pressing the one end of the raw steel pipe. the tube end, said with tape having the radial contraction rate substantially enlarged rate of the same rate - Pas angle by inserting a mouth widened tool is more than 30 degrees, without pressing the tube end of said intermediate steel pipe, A method of manufacturing a thickened steel pipe, wherein a thickened steel pipe having a larger wall thickness than that of the material steel pipe is manufactured by subjecting the intermediate steel pipe to a diameter expansion process.

  In the case of using a welded steel pipe as the material steel pipe, the degree of the thickening in the longitudinal direction position from the pipe end in the thickened part of the thickened steel pipe manufactured according to the present invention can be sufficiently obtained as about 27% or more. In the circumferential position at the pipe end, about 0.5% of the thickness is reduced by the side of the weld, but the thickness of the other base material can be increased by about 1.5%.

  In the present invention, the ratio (t / D) between the thickness t (mm) of the original tube and the outer diameter D (mm) is 0.005 to 0.3, and 0.5 ≦ t ≦ 30. It is applied under the condition of 15 ≦ D ≦ 700.

  The steel type of the original pipe to which the present invention is applied is not particularly limited, but even a high-strength metal material such as high-strength steel can be preferably used.

  According to the present invention, it is possible to easily form a thickened steel pipe having a wall thickness that is greater than that of the material steel pipe. When secondary processing for reducing the thickness of the thickened steel pipe is performed on the thickened steel pipe manufactured according to the present invention, for example, widening processing, even if the thinned steel pipe is thinned, It becomes possible to satisfy the design requirements regarding the thickness of the automobile parts.

Fig.1 (a)-FIG.1 (e) are explanatory drawings which show the condition which manufactures a thickened steel pipe with the manufacturing method which concerns on this invention. FIG. 2 is a graph showing the degree of thickening at the longitudinal position from the tube end in the thickened portion. FIG. 3 is a graph showing the wall thickness at the circumferential position at the pipe end.

The present invention will be described with reference to the accompanying drawings. FIG. 1A to FIG. 1E are explanatory views showing a situation in which a thickened steel pipe 6 is manufactured by the manufacturing method according to the present invention. In FIGS. 1A to 1D, reference numeral 2 indicates a mouthpiece tool, and reference numeral 5 indicates a mouth spreading tool.

  In the steps shown in FIGS. 1A to 1E, the intermediate steel pipe 4 is manufactured by reducing the diameter of the raw steel pipe 1 using the aperture tool 2 and the mold 3 that supports the raw steel pipe 1. Then, using the die 3 for supporting the widening tool 5 and the intermediate steel pipe 4 to the intermediate steel pipe 4, the diameter increasing process is performed to manufacture the thickened steel pipe 6.

  Although the steel types of the material steel pipe 1 include, for example, stainless steel and aluminum alloy steel, even a high-strength metal material such as high-tensile steel can be preferably used.

  When the thickness of the raw steel pipe 1 is t (mm) and the outer diameter is D (mm), t / D: 0.005 to 0.3, 0.5 ≦ t ≦ 30, 15 ≦ D ≦ The raw material steel pipe 1 which satisfies the range of 700 can be used.

This mouth aperture taper angle theta ₁ of the mouth aperture tool 2 used in processing can be used from 5 to 50 degrees, Te - the path angle increases the axial load is increased, since the buckling tends to occur It is desirable to use an aperture tool having a taper angle of 20 to 30 degrees.

  Further, as a result of studying the radius of curvature R (mm) of the taper portion, if the radius of curvature R is reduced (for example, 10 mm), the axial load increases, so that an effect of increasing the thickness can be expected. In order to bend easily, the radius of curvature R of the taper portion is desirably 20 to 30 mm.

That is, as shown in FIGS. 1 (a) and 1 (b), Te - less path angle theta ₁ is 30 degrees, Te - mouth aperture tool (contraction径工tool) the radius of curvature R of the path portion is 20mm or more 2 is used to produce the intermediate steel pipe 4 by reducing the diameter of the raw steel pipe 1 at a predetermined reduction ratio (for example, 25%), and then, as shown in FIGS. 1 (c) and 1 (d), A diameter expansion process is performed on the intermediate steel pipe 4 by using a widening tool (diameter expansion tool) 5 having a diameter expansion ratio substantially equal to the diameter reduction ratio of the diameter processing and a taper angle of 30 degrees or more. Thereby, as shown in FIG.1 (e), the thickened steel pipe 6 which has a thickness larger than the thickness of the raw steel pipe 1 is manufactured.

Mouth spread the tool 5 Te - Pas angle theta ₂ may be used as the substantially the same manner as 5 to 60 degrees and taper angle theta ₁ of the mouth aperture tool 2. Mouth spread of the tool 5 Te - thickening effect for when the path angle θ ₂ is too small, the axial load does not take much smaller, on the other hand, the hand - buckling when the path angle is too large axial load is too large Therefore, the taper angle θ ₂ is desirably 30 degrees or more.

  According to the present invention shown in FIGS. 1 (a) to 1 (e), a thickened steel pipe 6 having a thickness larger than that of the raw steel pipe 1 can be easily formed. If secondary processing for reducing the thickness of the thickened steel pipe 6 is performed on the thickened steel pipe 6 manufactured according to the present invention, for example, squeezing, for example, even if the thinned steel pipe 6 is thinned, It becomes possible to satisfy the design requirements regarding the thickness of the automobile parts after processing.

  In this way, the thickened steel pipe 6 having a thickness larger than the thickness of the material steel pipe 1 can be manufactured. The outer diameter of the thickened steel pipe 6 may be the same as the outer diameter of the material steel pipe 1 or may be slightly different from the outer diameter of the material steel pipe 1 so as to be substantially the same.

  It is desirable to apply a lubricant to prevent seizure between the raw steel pipe 1, the intermediate steel pipe 4, the squeezing tool 2, and the widening tool 5, but depending on the type of lubricant, sliding in the axial direction is preferable. However, since the easiness to change and the effect of increasing the thickness also differ, an appropriate lubricant may be used.

In the thickened steel pipe 6 manufactured according to the present invention, the thickness increase in the longitudinal position from the pipe end in the thickened part can be sufficiently obtained as about 27% or more, and the thinning at the pipe end is reduced. (Although thinning of about 0.5% can be seen at the side of the weld, it is about 1.5% thicker for other base materials)
The thickened steel pipe 6 can be manufactured.

  As described above, according to the present invention, the thickened steel pipe 6 whose thickness is increased as compared with the material steel pipe 1 can be easily formed. If secondary processing for reducing the thickness of the thickened steel pipe 6 is performed on the thickened steel pipe 6 manufactured according to the present invention, for example, squeezing, for example, even if the thinned steel pipe 6 is thinned, It becomes possible to satisfy the design requirements regarding the thickness of the automobile parts after processing.

  The present invention for performing a diameter expanding process after performing a diameter reducing process on a material steel pipe (outer diameter D: 22.2 mm, wall thickness t: 1.2 mm, t / D: 0.054, steel type: stainless steel), Numerical analysis of the situation of manufacturing a thickened steel pipe with increased wall thickness in the range of 40 mm from the pipe end to the axial direction by the invention described in Patent Document 3 in which diameter reduction processing is performed after diameter expansion processing did.

Incidentally, the taper angle theta ₁ is 20 degrees mouth aperture tool used in diametral reduction, Te - the radius of curvature R of the path portion is 25 mm, radial contraction rate for the material steel pipe is 25%. In addition, a lubricant was applied to prevent seizure of the raw steel pipe, the intermediate steel pipe, the mouth drawing tool, and the mouth spreading tool.

In the present invention, the taper angle θ ₂ of the mouth-opening tool used for the diameter expansion processing on the intermediate steel pipe is set to three levels of 50 degrees, 30 degrees, and 20 degrees.

  For each of the thickened steel pipes obtained by the invention described in the present invention, Patent Document 3, the degree of thickening at the longitudinal position from the pipe end in the thickened part, the thinning at the pipe end, and the pipe end The fluctuation margin of the wall thickness at the circumferential position relative to the original wall thickness of the material pipe was obtained.

  FIG. 2 is a graph showing the degree of thickening at the longitudinal position from the pipe end in the thickened portion, and FIG. 3 is a graph showing the thickness at the circumferential position at the pipe end.

  As shown in the graph of FIG. 2, the thickness increase at the longitudinal position from the pipe end in the increased thickness portion was sufficiently increased to about 27% or more according to the present invention, whereas Patent Document 3 According to the invention described in the above, it can be seen that it was unsatisfactory at 16%.

  As shown in the graph of FIG. 3, it can be seen that, according to the present invention, the thickness reduction at the pipe end portion can be reduced as compared with the invention described in Patent Document 3.

  Furthermore, as shown in the graph of FIG. 3, the pipe end where there is a concern about cracking is hardly thinned (0.5% thinning near the welded portion), and the base metal part is thickened. I understand that.

1 Material steel pipe 2 Narrowing tool (reducing tool)
3 Mold 4 Intermediate steel pipe 5 Opening tool (Expansion tool)
6 Thickened steel pipe

Claims (1)

One end of the material steel, Te - Te with path angle is less than 30 degrees - the radius of curvature of the path portion by inserting the mouth aperture tool is 20mm or more, without inserting the core metal into the material steel pipe, and After manufacturing the intermediate steel pipe by reducing the diameter of the raw steel pipe at a predetermined reduction ratio without pressing the one end of the raw steel pipe, the pipe end corresponding to one end of the raw steel pipe of the intermediate steel pipe, Inserting a widening tool having a diameter expansion ratio of approximately the same ratio as the diameter reduction ratio and a taper angle of 30 degrees or more, without pressing the pipe end of the intermediate steel pipe, A method for producing a thickened steel pipe, characterized by producing a thickened steel pipe having a larger wall thickness than that of the material steel pipe by performing a diameter expansion process.

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