JP5629598B2 - Manufacturing method for seamless steel pipe for high strength hollow spring - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for producing a high-strength seamless steel pipe element for a hollow spring, and in particular, to produce a high-quality seamless steel pipe element pipe suitable for producing a hollow steel suspension spring used in automobiles and the like. It is about the method.

  In recent years, with increasing demands for lighter and higher output vehicles for the purpose of reducing exhaust gas and improving fuel efficiency, high-stress designs have been applied to suspension springs, valve springs, clutch springs, etc. used in suspensions, engines, clutches, etc. Is oriented. Therefore, these springs are in the direction of increasing the strength and reducing the diameter, and the load stress tends to further increase. In order to respond to these trends, spring steel with higher performance in terms of fatigue resistance and sag resistance is strongly desired. Also, in order to achieve weight reduction while maintaining fatigue resistance and sag resistance, pipes that are hollow rather than the rod-shaped wire (ie, solid wire) that has been used as a spring material so far A steel material having no welded portion (that is, a seamless pipe) is used as a spring material. Various techniques for producing the hollow seamless steel pipe as described above have been proposed so far.

  For example, Patent Document 1 discloses a method of manufacturing a seamless steel pipe for a spring in which mandrel mill rolling is performed after Mannesmann drilling, but there is a problem that deep inner surface flaws are likely to occur during Mannesmann drilling. Further, although Patent Document 2 discloses a method of manufacturing a seamless steel pipe having a shallow surface flaw by using a cylindrical billet and performing hydrostatic extrusion, the generation of coarse inner flaws cannot be reliably suppressed. I had a problem.

Japanese Patent No. 2512984 JP 2007-125588 A

  The present invention has been made in view of the above-described technical background, and it is possible to produce coarse inner surface flaws in the hollow surface layer portion of a hollow billet during the manufacture of a seamless steel pipe for a high-strength hollow spring, particularly during the hot extrusion process. An object of the present invention is to provide a method for manufacturing a raw steel pipe for seamless steel pipe that suppresses generation.

  1. C: 0.2-0.7 mass%, Si: 0.5-3 mass%, Mn: 0.1-2 mass%, Al: 0.1 mass% or less (excluding 0%), P: From steel containing 0.02% by mass or less (excluding 0%), S: 0.02% by mass or less (not including 0%) and N: 0.02% by mass or less (not including 0%) And a hollow billet in which the average crystal grain size of the steel structure in the inner surface layer portion is adjusted to 15 μm or less is subjected to hot extrusion to produce a hollow seamless steel pipe. A manufacturing method of a base pipe for a seamless steel pipe for a high-strength hollow spring.

  2. The element for a seamless steel pipe for high-strength hollow springs according to claim 1, wherein the crystal grain size of the steel structure in the inner surface layer of the hollow billet is adjusted by hot forging at a forging finish temperature of 900 ° C or higher and lower than 1000 ° C. A method of manufacturing a tube.

  3. 2. The high strength hollow spring according to claim 1, wherein the adjustment of the crystal grain size of the steel structure in the inner surface layer portion of the hollow billet is performed by a normalizing treatment at 900 ° C. or more and less than 1000 ° C. performed after hot forging. A method for producing a seamless steel pipe.

  4). C: 0.2-0.7 mass%, Si: 0.5-3 mass%, Mn: 0.1-2 mass%, Al: 0.1 mass% or less (excluding 0%), P: From steel containing 0.02% by mass or less (excluding 0%), S: 0.02% by mass or less (not including 0%) and N: 0.02% by mass or less (not including 0%) A hollow billet is preheated to a temperature of 50 to 600 ° C., and then subjected to hot extrusion to produce a hollow seamless steel pipe. A method for producing a seamless steel pipe for a high-strength hollow spring.

  5. The said steel further contains Cr: 3 mass% or less (0% is not included), The manufacturing method of the raw steel pipe for seamless steel pipes for high-strength hollow springs in any one of Claims 1-4.

  6). The method for producing a raw steel pipe for a high-strength hollow spring seamless steel pipe according to any one of claims 1 to 5, wherein the steel further contains B: not more than 0.015 mass% (not including 0%).

  7). The steel further includes V: 1% by mass or less (excluding 0%), Ti: 0.3% by mass or less (not including 0%), and Nb: 0.3% by mass or less (excluding 0%). The manufacturing method of the raw steel pipe for seamless steel pipes for high-strength hollow springs in any one of Claims 1-6 containing 1 or more chosen from these.

  8). The steel according to any one of claims 1 to 7, further comprising at least one selected from Ni: 3% by mass or less (excluding 0%) and Cu: 3% by mass or less (not including 0%). The manufacturing method of the elementary pipe for seamless steel pipes for high-strength hollow springs of description.

  9. The method for manufacturing a raw steel pipe for a high-strength hollow spring according to any one of claims 1 to 8, wherein the steel further contains Mo: 2 mass% or less (not including 0%).

  10. The steel is further Ca: 0.005 mass% or less (excluding 0%), Mg: 0.005 mass% or less (not including 0%), and REM: 0.02 mass% or less (including 0%). The manufacturing method of the raw steel pipe for seamless steel pipes for high intensity | strength hollow springs in any one of Claims 1-9 containing 1 or more chosen from.

  11. The steel further includes Zr: 0.1% by mass or less (excluding 0%), Ta: 0.1% by mass or less (excluding 0%), and Hf: 0.1% by mass or less (0% The manufacturing method of the raw | natural pipe | tube for seamless steel pipes for high strength hollow springs in any one of Claims 1-10 containing 1 or more types chosen from (it does not contain).

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the coarse inner surface flaw in an inner surface surface layer part can be suppressed, and a high quality high intensity | strength hollow steel spring for seamless steel pipes can be manufactured.

Hereinafter, the contents of the present invention will be described in detail.
First, the raw material (hollow billet) in the method for producing a raw steel pipe for a seamless steel pipe for high-strength hollow springs of the present invention (hereinafter may be abbreviated as the present method production method, the present production method, the present method, the present invention, etc.). Regarding the chemical components of steel, the component ranges and reasons for limitation will be described from the basic components (elements) C, Si, Mn, Al, P, S, and N. In addition, the% display about each following component means all the mass%.

(1) C: 0.2 to 0.7%
C is an element necessary for ensuring high strength, and for that purpose it is necessary to contain 0.20% or more. The C content is preferably 0.3% or more, more preferably 0.35% or more. However, if the C content is excessive, it is difficult to ensure ductility, so it is necessary to set the content to 0.7% or less. The C content is preferably 0.65% or less, and more preferably 0.6% or less.

(2) Si: 0.5 to 3%
Si is an element effective for improving the sag resistance necessary for the spring. To obtain the sag resistance necessary for the spring of the strength level targeted in the present invention, the Si content is 0.5%. It is necessary to do it above. Preferably it is 1% or more, More preferably, it is 1.5% or more. However, since Si is also an element that promotes decarburization, if Si is excessively contained, formation of a decarburized layer on the steel surface is promoted. As a result, a peeling process for removing the decarburized layer is required, which is inconvenient in terms of manufacturing cost. For these reasons, the upper limit of the Si content is set to 3% in the present invention. Preferably it is 2.5% or less, More preferably, it is 2.2% or less.

(3) Mn: 0.1 to 2%
Mn is a beneficial element that is used as a deoxidizing element and detoxifies by forming S and MnS, which are harmful elements in steel. In order to exhibit such an effect effectively, it is necessary to contain 0.1% or more of Mn. Preferably it is 0.15% or more, more preferably 0.2% or more. However, when the Mn content is excessive, segregation bands are formed, resulting in variations in materials. For these reasons, the upper limit of the Mn content is set to 2% in the present invention. Preferably it is 1.5% or less, More preferably, it is 1% or less.

(4) Al: 0.1% or less (excluding 0%)
Al is mainly added as a deoxidizing element. Further, N and AlN are formed to render the solid solution N harmless and contribute to the refinement of the structure. In particular, in order to fix the solute N, it is preferable to contain Al so as to exceed twice the N content. However, since Al is an element that promotes decarburization in the same way as Si, it is necessary to suppress the addition of a large amount of Al in the spring steel containing a large amount of Si. Preferably it is 0.07% or less, More preferably, it is 0.05% or less.

(5) P: 0.02% or less (excluding 0%)
Since P is a harmful element that deteriorates the toughness and ductility of steel, it is important to reduce it as much as possible. In the present invention, the upper limit is set to 0.02%. Preferably it is 0.01% or less, more preferably 0.008% or less. Note that P is an impurity inevitably contained in the steel material, and it is difficult to make the amount 0% in industrial production.

(6) S: 0.02% or less (excluding 0%)
Since S is a harmful element that deteriorates the toughness and ductility of steel as in the case of P described above, it is important to reduce it as much as possible. In the present invention, S is suppressed to 0.02% or less. Preferably it is 0.01% or less, More preferably, it is 0.008% or less. In addition, S is an impurity inevitably contained in steel, and it is difficult to make the amount 0% in industrial production.

(7) N: 0.02% or less (excluding 0%)
N has the effect of forming nitrides and refining the structure when Al, Ti, and the like are present, but when present in a solid solution state, N deteriorates the toughness and hydrogen embrittlement resistance of the steel material. In the present invention, the upper limit of the N amount is set to 0.02%. Preferably it is 0.01% or less, More preferably, it is 0.005% or less.

  The material to which the present invention is applied requires the above-mentioned basic components, and further, Cr, B, [V, Ti, Nb], [Ni, Cu], Mo, [Ca, Mg, REM] as selective components. ], [Zr, Ta and Hf] can be added and contained as appropriate. About these selection components, the component range and the reason for limitation will be described. In addition, it has shown that the component enclosed with [] is an element of the same effect.

Cr: 3% or less (excluding 0%)
Cr is an effective element for securing strength and improving corrosion resistance after tempering, and is an important element for suspension springs that require a high level of corrosion resistance. Such an effect increases as the Cr content increases, but in order to exert such an effect preferentially, it is preferable to contain Cr by 0.2% or more. More preferably, the content is 0.5% or more. However, when the Cr content is excessive, a supercooled structure is likely to be generated, and it is concentrated in cementite to lower the plastic deformability, resulting in deterioration of cold workability. When the Cr content is excessive, Cr carbide different from cementite is likely to be formed, and the balance between strength and ductility is deteriorated. For these reasons, in the steel material used in the present invention, the Cr content is preferably suppressed to 3% or less. More preferably, it is 2% or less, and still more preferably 1.7% or less.

B: 0.015% or less (excluding 0%)
B has an effect of suppressing fracture from the prior austenite grain boundaries after quenching and tempering of the steel material. In order to exhibit such an effect, it is preferable to contain B 0.001% or more. However, when B is contained excessively, a coarse carbon boride is formed and the characteristics of the steel material are impaired. Moreover, when B is contained more than necessary, it also causes generation of wrinkles in the rolled material. For these reasons, the upper limit of the B content is set to 0.015%. More preferably, it is 0.010% or less, and further preferably 0.005% or less.

[V: 1% or less (not including 0%), Ti: 0.3% or less (not including 0%) and Nb: 0.3% or less (not including 0%) 1 More than species]
V, Ti, and Nb form carbon / nitrides (carbides, nitrides, carbonitrides), sulfides, and the like with C, N, S, etc., and have the effect of detoxifying these elements. Further, the effect of refining the structure by forming the charcoal / nitride is also exhibited. Furthermore, it has the effect of improving delayed fracture resistance. However, when the content of these elements is excessive, coarse charcoal / nitride is formed, and the toughness and ductility may deteriorate. Therefore, in this invention, it is preferable to make the upper limit of content of V, Ti, and Nb into 1%, 0.3%, and 0.3%, respectively. More preferably, V is 0.5% or less, Ti is 0.1% or less, and Nb is 0.1% or less. Furthermore, from the viewpoint of cost reduction, it is preferable that V: 0.3% or less, Ti: 0.05% or less, and Nb: 0.05% or less.

[Ni: 3% or less (not including 0%) and / or Cu: 3% or less (not including 0%)]
In consideration of cost reduction, Ni does not have a lower limit in order to prevent addition. However, when suppressing surface decarburization or improving corrosion resistance, Ni is preferably contained in an amount of 0.1% or more. However, if the Ni content is excessive, a supercooled structure may be generated in the rolled material, or retained austenite may be present after quenching, which may deteriorate the properties of the steel material. For these reasons, when Ni is contained, the upper limit is made 3%. From the viewpoint of cost reduction, it is preferably 2% or less, more preferably 1% or less.

  Cu is an element effective for suppressing surface layer decarburization and improving the corrosion resistance like Ni. In order to exert such an effect, it is preferable to contain 0.1% or more of Cu. However, if the Cu content is excessive, a supercooled structure may be generated or cracks may occur during hot working. For these reasons, when Cu is contained, the upper limit is made 3%. From the viewpoint of cost reduction, it is preferably 2% or less, more preferably 1% or less.

Mo: 2% or less (excluding 0%)
Mo is an element effective for securing strength and improving toughness after tempering. However, when the Mo content is excessive, toughness deteriorates. For these reasons, the upper limit of the Mo content is preferably 2%. More preferably, it is 0.5% or less.

[Ca: selected from the group consisting of 0.005% or less (excluding 0%), Mg: 0.005% or less (not including 0%), and REM: 0.02% or less (not including 0%) One or more
Ca, Mg, and REM (rare earth elements) all form sulfides and have an effect of improving toughness by preventing elongation of MnS, and can be added according to required characteristics. However, if the content exceeds the upper limit, the toughness is deteriorated. The preferable upper limit of each is 0.003% for Ca, 0.003% for Mg, and 0.01% for REM.
In the present invention, REM means a lanthanoid element (15 elements from La to Ln), Sc (scandium) and Y (yttrium).

[Zr: selected from the group consisting of 0.1% or less (not including 0%), Ta: 0.1% or less (not including 0%), and Hf: 0.1% or less (not including 0%) One or more
These elements are combined with N to form nitrides and are stable and suppress the growth of austenite (γ) grain size during heating, and have the effect of reducing the final structure and improving toughness. However, it is not preferable to add excessively in excess of 0.1% because the nitride becomes coarse and deteriorates fatigue characteristics. For these reasons, the upper limit was set to 0.1%. A more preferable upper limit is 0.05% in all cases, and a further preferable upper limit is 0.025%.

  And in this invention method, a hot-extrusion method is fundamentally applied using the high strength spring steel which has the said component as a raw material, and a raw steel pipe for seamless steel pipes is manufactured. As a whole manufacturing process, the steel of the same component is melted by a refining furnace such as a converter, and is cast into a slab by a continuous casting method, and this slab is hot-rolled to form a billet (square or round). The raw billet is hot forged and / or hot-rolled, and further subjected to heat treatment such as normalization as necessary, and then machined to form a hollow billet. This hollow billet is hot-extruded to produce a hot-extruded steel pipe (seamless pipe for seamless steel pipe). In addition, the obtained seamless steel pipes are usually subjected to cold processing such as drawing and pilger mill rolling, annealing for softening purposes, and pickling for the purpose of removing annealing scale, usually repeatedly several times, It is formed into a seamless steel pipe shape.

  The present inventors have conducted various studies on the cause of coarse inner surface flaws that occur in the manufacture of such a seamless steel pipe, and when the hollow billet is heated before the hot extrusion process, cracks are generated on the inner surface of the billet. It was discovered that it remained as an internal flaw in the product after the subsequent cold working. This crack on the inner surface of the billet is due to thermal stress generated on the inner surface of the hollow part during heating, and when producing a billet for hot extrusion using the steel for high strength springs targeted in the present invention, In order to ensure workability, the ferrite and pearlite structure is controlled, but it was found that the ferrite and pearlite structure of medium carbon steel is due to the lack of notch toughness.

  Based on these findings, we came up with the idea that improving the notch toughness of billet materials is effective in suppressing the occurrence of internal flaws in seamless steel pipes. In order to improve the notch toughness, the steel structure of the hollow billet before hot extrusion is refined and adjusted to an appropriate crystal grain size range, or the hollow billet is appropriately processed before hot extrusion. It has been found important to preheat to a temperature range. These conditions will be described more specifically.

(A) Steel structure of hollow billet (average crystal grain size: 15 microns or less)
When the structure size of the hollow billet made of high strength spring steel of the steel component of the present invention and the occurrence of cracks after hot extrusion were investigated, the inner surface layer portion (hollow inner surface layer portion) of the billet It was confirmed that internal cracks occurred when the average crystal grain size of the steel structure exceeded 15 μm, whereas cracks did not occur when the average crystal grain size was 15 μm or less. From this result, in the present invention, it is essential to perform hot extrusion using a hollow billet in which the average crystal grain size in the inner surface layer portion is adjusted to 15 μm or less in advance. Further, by using a hollow billet having an average crystal grain size of preferably 12 μm or less, more preferably 10 μm or less, the notch toughness of steel is further improved, and the occurrence of internal cracks can be more reliably suppressed. Become. Here, the inner surface layer portion indicates a region in which the thickness from the inner surface is 0.1 mm or less.

  And as a concrete method for adjusting the average crystal grain size of the inner surface layer portion to 15 μm or less, the finishing temperature is set to 900 ° C. or higher and 1000 ° C. during hot forging or hot rolling in the forming step of the hollow billet. It is sufficient to perform the normalizing treatment at a temperature of 900 ° C. or more and less than 1000 ° C. after the hot forging or hot rolling. Of course, the method is not limited to these methods as long as the average crystal grain size of the hollow billet can be adjusted to 15 μm or less. In the case of hot forging or hot rolling, when the finishing temperature is set to 900 ° C. or higher and lower than 1000 ° C., the heating temperature before processing may be easily controlled to the finishing temperature condition. Specifically, heating may be performed at about 900 to 1250 ° C. Moreover, when performing the normalizing process at a temperature of 900 ° C. or higher and lower than 1000 ° C. after the hot forging or hot rolling, the hot forging or hot rolling may be performed under normal conditions. Usually, hot forging and hot rolling are performed under conditions such that the heating temperature is about 1000 to 1250 ° C. and the finishing temperature is 1000 ° C. or higher.

(B) Preheating of the hollow billet (preheating temperature: 50 to 600 ° C.)
On the other hand, the notch toughness of high-strength spring molten steel is greatly affected by the heating state at a relatively low temperature, so it is considered that preheating before heating during hot extrusion is effective for improving the notch toughness. The relationship between the preheating temperature of the hollow billet and the occurrence of cracks after hot extrusion was investigated, and it was found that no internal cracking occurred when the preheating temperature was 50 to 600 ° C.
Based on this result, in the present invention, as a means different from the adjustment of the grain size of the steel structure, it is also essential to preheat at 50 to 600 ° C. once before the heating at the time of hot extrusion. It is. Further, by setting the lower limit of the preheating temperature of the hollow billet to 100 ° C., more preferably 300 ° C., the notch toughness of the steel is further improved, and the occurrence of internal cracks can be more reliably suppressed.

  And in this invention, after processing by these (A) and / or (B) conditions, a hollow billet should just be hot-extruded on normal conditions. Usually, hot extrusion is performed after heating the billet to about 950 to 1150 ° C.

(Example)
Examples are given below to demonstrate the excellent effects of the present invention.
After melting a medium carbon spring steel having the chemical composition shown in Table 1 as test steel and hot rolling a slab produced by continuous casting to produce a 155 square billet (steel slab), Hot forging was performed at various forging heating temperatures and forging finishing temperatures of 900 to 1250 ° C. to form 150φ round bars. About some, the normalizing process was performed at 900 degreeC and 950 degreeC after hot forging. Next, a 150φ round bar is machined to produce a hollow billet for extrusion having an outer diameter of 143φ × inner diameter of 40φ. The hollow billet is heated to 1000 to 1050 ° C. by high-frequency heating, and then subjected to hot extrusion. A hot-extruded steel pipe having a diameter of 54φ and an inner diameter of 38φ (elementary tube for seamless steel pipe) was obtained.

Then, a sample for observing the structure is collected from the axial center of each seamless steel pipe obtained in this way by wet cutting, and observed to observe the cross section of the steel pipe (plane perpendicular to the extrusion axis direction). The sample was adjusted. At this time, nital (nitric acid + alcohol) was used as a corrosive solution for revealing the metal structure. The steel structure of the inner surface layer portion (region of 0.1 mm or less from the inner surface) of the prepared sample was observed with an optical microscope at a magnification of 100 to 400 times, and the crystal grain size of the ferrite pearlite structure was measured by a ferrite grain size measuring method ( In accordance with JISG0552), the crystal grain size number was measured to the first decimal place. The crystal grain size number of 5 fields was measured for each sample, the average particle size number G was calculated, and the crystal grain size converted to the unit of μm was obtained by the following formula.
Crystal grain size D (μm) = 10 × 2 ^{(10-G) / 2}
In addition, the presence or absence of wrinkles was checked by ultrasonic inspection. When a wrinkle signal was recognized by ultrasonic flaw detection, the signal portion was cut and the wrinkle size was measured. At this time, the case where wrinkles of 100 μm or more were not recognized in the ultrasonic flaw detection test was evaluated as “◯”, the case where there was a wrinkle signal and the cut inspection was 100 μm or more and 200 μm or less was evaluated as “X”, These results are shown in Table 2 together with the manufacturing conditions of the hollow billet.

As is clear from the comparison between the examples (invention examples) according to the method of the present invention and the comparative examples in Table 2, the average crystal grain size of the hollow billet (inner surface layer part) before hot extrusion is adjusted to 15 μm or less. Alternatively, by preheating the hollow billet to 50 to 600 ° C, cracks do not occur even when heated during hot extrusion, and a high-quality, high-strength seamless steel pipe for hollow springs with no internal defects is obtained. You can see that

Claims (11)

  C: 0.2-0.7 mass%, Si: 0.5-3 mass%, Mn: 0.1-2 mass%, Al: 0.1 mass% or less (excluding 0%), P: From steel containing 0.02% by mass or less (excluding 0%), S: 0.02% by mass or less (not including 0%) and N: 0.02% by mass or less (not including 0%) And a hollow billet in which the average crystal grain size of the steel structure in the inner surface layer portion is adjusted to 15 μm or less is subjected to hot extrusion to produce a hollow seamless steel pipe. A manufacturing method of a base pipe for a seamless steel pipe for a high-strength hollow spring.   The element for a seamless steel pipe for high-strength hollow springs according to claim 1, wherein the crystal grain size of the steel structure in the inner surface layer of the hollow billet is adjusted by hot forging at a forging finish temperature of 900 ° C or higher and lower than 1000 ° C. A method of manufacturing a tube.   2. The high strength hollow spring according to claim 1, wherein the adjustment of the crystal grain size of the steel structure in the inner surface layer portion of the hollow billet is performed by a normalizing treatment at 900 ° C. or more and less than 1000 ° C. performed after hot forging. A method for producing a seamless steel pipe.   C: 0.2-0.7 mass%, Si: 0.5-3 mass%, Mn: 0.1-2 mass%, Al: 0.1 mass% or less (excluding 0%), P: From steel containing 0.02% by mass or less (excluding 0%), S: 0.02% by mass or less (not including 0%) and N: 0.02% by mass or less (not including 0%) The hollow billet is preheated to a temperature of 50 to 600 ° C., and then subjected to hot extrusion to produce a hollow seamless steel pipe blank for seamless steel pipe. Manufacturing method.   The said steel further contains Cr: 3 mass% or less (0% is not included), The manufacturing method of the raw steel pipe for seamless steel pipes for high-strength hollow springs in any one of Claims 1-4.   The method for producing a raw steel pipe for a high-strength hollow spring seamless steel pipe according to any one of claims 1 to 5, wherein the steel further contains B: not more than 0.015 mass% (not including 0%).   The steel further includes V: 1% by mass or less (excluding 0%), Ti: 0.3% by mass or less (not including 0%), and Nb: 0.3% by mass or less (excluding 0%). The manufacturing method of the raw steel pipe for seamless steel pipes for high-strength hollow springs in any one of Claims 1-6 containing 1 or more chosen from these.   The steel according to any one of claims 1 to 7, further comprising at least one selected from Ni: 3% by mass or less (excluding 0%) and Cu: 3% by mass or less (not including 0%). The manufacturing method of the elementary pipe for seamless steel pipes for high-strength hollow springs of description.   The method for manufacturing a raw steel pipe for a high-strength hollow spring according to any one of claims 1 to 8, wherein the steel further contains Mo: 2 mass% or less (not including 0%).   The steel is further Ca: 0.005 mass% or less (excluding 0%), Mg: 0.005 mass% or less (not including 0%), and REM: 0.02 mass% or less (including 0%). The manufacturing method of the raw steel pipe for seamless steel pipes for high intensity | strength hollow springs in any one of Claims 1-9 containing 1 or more chosen from. The steel further includes Zr: 0.1% by mass or less (excluding 0%), Ta: 0.1% by mass or less (excluding 0%), and Hf: 0.1% by mass or less (0% The manufacturing method of the raw | natural pipe | tube for seamless steel pipes for high strength hollow springs in any one of Claims 1-10 containing 1 or more types chosen from (it does not contain).