JP4911672B2 - Method for manufacturing high-pressure fuel pipe for accumulator fuel injection system - Google Patents
Method for manufacturing high-pressure fuel pipe for accumulator fuel injection system Download PDFInfo
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本発明は、主としてディーゼルエンジン用の蓄圧式燃料噴射システムに組込まれるコモンレールと、ポンプ〜コモンレール間およびコモンレール〜インジェクタ間に配設される燃料噴射管からなる高圧燃料配管とその製造方法に関する。 The present invention relates to a high-pressure fuel pipe mainly composed of a common rail incorporated in an accumulator fuel injection system for a diesel engine, a fuel injection pipe disposed between a pump and a common rail, and between a common rail and an injector, and a manufacturing method thereof.
ディーゼルエンジン用の蓄圧式燃料噴射システムに組込まれるコモンレールや、ポンプ〜コモンレール間およびコモンレール〜インジェクタ間に配設される燃料噴射管等からなる従来の燃料配管には、連続鋳造して得られた断面丸形ビレットをマンネスマン・マンドレルミル方式やマンネスマン・プラグミル方式の穿孔機を使って穿孔・圧延・伸管して製造した継目無鋼管や、前記ビレットを押出しや引抜きにより圧延した鍛造用丸棒等が採用されるのが一般的である。 Cross sections obtained by continuous casting in conventional fuel pipes such as common rails installed in pressure-accumulation fuel injection systems for diesel engines and fuel injection pipes arranged between pumps and common rails and between common rails and injectors Seamless steel pipes manufactured by drilling, rolling, and drawing round billets using Mannesmann mandrel mill type or Mannesmann plug mill type drilling machines, and round bars for forging that are rolled by extruding or drawing the billet Generally adopted.
ところで、連続鋳造された鋳片は周知の通り、鋳造時の最終凝固位置に相当する鋳片の横断面（引抜き方向に対して直角方向の断面）中心部に、軸方向に不連続の内部空隙（センターポロシティー）が存在する。この内部空隙が穿孔圧延時に十分に圧着されないで管内面に露出して管内面疵となる場合がある。
このような欠点を解決するために、連続鋳造時の最終凝固位置をビレット中心より外側にずらしたり、鋳型直下から凝固を開始するまでの冷却強度をビッレット外周方向で変化させて鋳造片中心に対して非対称の凝固シェルを生成させた後凝固冷却を開始して、ビレット中心部に空隙部分が発生して非金属介在物が偏析するのを防止する継目無鋼管素材用連続鋳造鋳片の製造方法が提案されている（特許文献１、２参照）。
By the way, the slab continuously cast is, as is well known, an axially discontinuous internal gap at the center of the cross section (cross section perpendicular to the drawing direction) of the slab corresponding to the final solidification position during casting. (Center Porosity) exists. In some cases, the internal gap is not sufficiently pressed during piercing and rolling, and is exposed to the inner surface of the tube to become a tube inner surface flaw.
In order to solve these disadvantages, the final solidification position during continuous casting is shifted to the outside of the billet center, or the cooling strength until solidification is started from directly below the mold is changed in the outer periphery of the billet to the center of the cast piece. A method for producing a continuous cast slab for a seamless steel pipe material in which a solidified cooling shell is formed and then solidification cooling is started to prevent a non-metallic inclusion from segregating due to the formation of a void in the center of the billet. Has been proposed (see Patent Documents 1 and 2).
特許文献１に記載されている方法は、連続鋳造装置の鋳型直下から鋳片中心部が凝固を開始し出すより以前までの間の二次冷却を、鋳片周方向に冷却強度を変化させて施すことにより、鋳片中心に対して非対称の凝固シェルを生成させた後、さらに凝固末期二次冷却を、未凝固液芯の中心部が凝固を開始し出した後から液芯の中心固相率が０．８以上となるまで継続して施す方法である。
この方法によれば、空隙（センターポロシティー）を鋳片中心から外れた位置に生成させることができると共に、偏心して生成するポロシティーを低減させることができる。
In the method described in Patent Document 1, the secondary cooling from immediately below the mold of the continuous casting apparatus to before the center of the slab starts to solidify is performed by changing the cooling strength in the slab circumferential direction. After the formation of an asymmetric solidified shell with respect to the center of the slab, further secondary cooling at the end of solidification is performed after the central part of the unsolidified liquid core starts to solidify. This is a method of continuously applying until the rate becomes 0.8 or more.
According to this method, a void (center porosity) can be generated at a position deviated from the center of the slab, and the porosity generated eccentrically can be reduced.
また、特許文献２に記載されている方法は、鋳片が鋳型直下から完全凝固に至る間に、長さ３ｍ以上の二次冷却帯で、鋳片周方向の冷却強度を変化させ、鋳片の最終凝固位置を鋳片中心より外側へずらす方法であり、さらに鋳片の最終凝固位置を鋳片中心よりずらした鋳片を、圧延温度に加熱しビレット中心をセンターとして穿孔圧延した鋼管素材から継目無鋼管を製造する方法である。
この方法によれば、鋳片の周囲から内部へ向けて凝固速度の異なる凝固シェルが成長して最終凝固部が鋳片中心より偏寄し、内部空隙も鋳片中心から外れた位置に形成される。
According to this method, solidified shells with different solidification speeds grow from the periphery of the slab to the inside, the final solidified part is offset from the center of the slab, and the internal void is also formed at a position off the center of the slab. The
しかしながら、上記した継目無鋼管素材用連続鋳造鋳片の製造方法では、いずれも鋳造時の鋳造金属（溶鋼等）の先端に発生する内部空隙（ポロシティー）部の表面付近に非金属介在物が偏析するため、当該連続鋳造鋳片を穿孔、伸管、圧延、あるいは押出し、引抜き、鍛造等の種々の加工を施しても前記非金属介在物は存在し除去することができないこと、またこの非金属介在物が管体の内面あるいは内面直下に存在すると、管体の使用時に圧力が上昇しかつその圧力が変動すると非金属介在物付近の母材に応力集中をきたし疲労破壊の基点となり得ること、等の問題がある。 However, in the above-described methods for producing continuous cast slabs for seamless steel pipe materials, there are non-metallic inclusions in the vicinity of the surface of the internal void (porosity) generated at the tip of the cast metal (molten steel, etc.) during casting. In order to segregate, the non-metallic inclusions exist and cannot be removed even if the continuous cast slab is subjected to various processes such as drilling, drawing, rolling, extrusion, drawing, forging, etc. If metal inclusions exist on the inner surface of the pipe body or directly under the inner surface, the pressure rises when the pipe is used, and if the pressure fluctuates, stress concentration may occur on the base metal near the non-metallic inclusions, which can be the starting point for fatigue failure , Etc.
本発明は、上記の問題点に鑑みなされたもので、高圧燃料噴射管やコモンレールに非金属介在物が存在しない蓄圧式燃料噴射システム用高圧燃料配管およびその製造方法を提供することを目的とするものである。 The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-pressure fuel pipe for an accumulator fuel injection system in which non-metallic inclusions are not present in a high-pressure fuel injection pipe or a common rail, and a method for manufacturing the same. Is.
本発明に係る蓄圧式燃料噴射システム用高圧燃料配管は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる組織を再結晶させて微細化した結晶粒を有する金属材料からなることを特徴とするものである。
本発明に係る蓄圧式燃料噴射システム用燃料配管の製造方法は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる丸棒を管軸方向に穿孔して素管となし、該素管を伸管工程にて縮径方向および／または管軸方向に圧延した後、熱処理工程にて再結晶温度以上に加熱して結晶粒を再結晶させ、さらに必要に応じて前記伸管工程および熱処理工程を繰り返し、その後、必要に応じてオートフレッテージ処理を施して高圧燃料噴射管とすることを特徴とするものである。
さらに、本発明に係る蓄圧式燃料噴射システム用高圧燃料配管の製造方法は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる丸棒を熱処理工程にて再結晶温度以上に加熱して結晶粒を再結晶させ、この再結晶させた丸棒を軸方向に穿孔した後、機械加工および／または分岐金具あるいは分岐管をろう付け、溶接もしくは組立て加工を施し、その後、必要に応じてオートフレッテージ処理を施してコモンレールとすることを特徴とするものである。
またさらに、本発明に係る蓄圧式燃料噴射システム用高圧燃料配管の製造方法は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる丸棒を縮径および／または軸方向に圧延後切断して鍛造素材とした後、該鍛造素材を鍛造加工し、さらに熱処理工程にて再結晶温度以上に加熱して結晶粒を再結晶させ、この再結晶させた鍛造素材を軸方向に穿孔した後、機械加工を施し、その後、必要に応じてオートフレッテージ処理を施してコモンレールとすることを特徴とするものである。
The high-pressure fuel pipe for an accumulator fuel injection system according to the present invention is an O.D. C. C. It is characterized in that it is made of a metal material having crystal grains refined by recrystallization of a structure consisting only of a unidirectionally solidified structure continuously cast by a process.
A method of manufacturing a fuel pipe for an accumulator fuel injection system according to the present invention is described in O.D. C. C. A round bar consisting only of a unidirectionally solidified structure continuously cast by the process is drilled in the pipe axis direction to form a raw pipe, and the raw pipe is rolled in the diameter reducing direction and / or the pipe axis direction in the drawing process. After that, the crystal grains are recrystallized by heating above the recrystallization temperature in the heat treatment step, and further, the tube drawing step and the heat treatment step are repeated as necessary, and then auto-frettage treatment is performed as necessary. A high-pressure fuel injection pipe is used.
Furthermore, the manufacturing method of the high-pressure fuel pipe for the pressure accumulation type fuel injection system according to the present invention is described in O.D. C. C. A round bar consisting only of a unidirectionally solidified structure continuously cast by the process is heated above the recrystallization temperature in a heat treatment step to recrystallize the crystal grains, and the recrystallized round bar is drilled in the axial direction. Thereafter, machining and / or brazing metal fittings or branch pipes are brazed, welded or assembled, and then auto-frettage treatment is performed as necessary to form a common rail.
Furthermore, a method for manufacturing a high-pressure fuel pipe for an accumulator fuel injection system according to the present invention is described in O.D. C. C. A round bar made only of a unidirectionally solidified structure continuously cast by a process is reduced in diameter and / or axially and then cut into a forged material, and then the forged material is forged and further subjected to a heat treatment process. The crystal grains are recrystallized by heating above the recrystallization temperature, and after drilling the recrystallized forged material in the axial direction, it is machined, and then subjected to auto-frettage treatment as necessary. It is characterized by doing.
なお、Ｏ．Ｃ．Ｃ．は、Ｏｈｎｏ Ｃｏｎｔｉｎｕｏｕｓ Ｃａｓｔｉｎｇの略で、等軸晶の全くない、一方向凝固組織のみからなる任意の断面形状の金属材料を、連続的に鋳造する方法である。 O. C. C. Is an abbreviation for Ohno Continuous Casting, and is a method of continuously casting a metal material having an arbitrary cross-sectional shape consisting of only a unidirectionally solidified structure and having no equiaxed crystals.
本発明の蓄圧式燃料噴射システム用高圧燃料配管は、等軸晶の全くない、一方向凝固組織のみからなる継目無鋼管素材用連続鋳造鋳片を素材としているため、非金属介在物が極めて少なく、引張応力が加わっても非金属介在物がほとんど存在しないのでその界面に発生する応力集中が発生せず内圧疲労強度が優れている。
また、本発明方法は、等軸晶の全くない、一方向凝固組織のみからなる継目無鋼管素材用連続鋳造鋳片を素材とし、該素材を伸管、鍛造、圧延等の塑性加工を施した後に再結晶温度以上に加熱して軸方向に連続していた結晶粒を再結晶させるので、機械的強度の高い高圧燃料配管が得られる。さらに、本発明方法によれば、配管の内面およびその表面直下に非金属介在物が存在しないので、引張応力が加わっても応力集中が発生せず、疲労強度も低下することなく内圧疲労強度の優れた高圧燃料配管を得ることができる。
The high-pressure fuel pipe for an accumulator fuel injection system according to the present invention is made of continuous cast slabs for seamless steel pipe material consisting of only a unidirectionally solidified structure without any equiaxed crystals, so there are very few non-metallic inclusions. Even when tensile stress is applied, there are almost no non-metallic inclusions, so stress concentration generated at the interface does not occur, and internal pressure fatigue strength is excellent.
In addition, the method of the present invention uses a continuous cast slab for a seamless steel pipe material made of only a unidirectionally solidified structure without any equiaxed crystal, and the material was subjected to plastic working such as drawn pipe, forging, and rolling. Since the crystal grains that have been continuously heated in the axial direction are recrystallized by heating to a temperature higher than the recrystallization temperature later, a high-pressure fuel pipe with high mechanical strength can be obtained. Furthermore, according to the method of the present invention, since there are no non-metallic inclusions on the inner surface of the pipe and immediately below the surface, stress concentration does not occur even if tensile stress is applied, and the internal pressure fatigue strength does not decrease without reducing the fatigue strength. An excellent high-pressure fuel pipe can be obtained.
本発明に係るＯ．Ｃ．Ｃ．プロセスの原理は、図１にその概要を示すごとく、従来の冷却鋳型に替えて、ヒーター１ａが埋設された加熱鋳型１を用い、該鋳型の内壁面の温度を溶湯（鋳造金属）２の凝固温度以上に保持し、鋳塊３の冷却を加熱鋳型１の外に配置した冷却水スプレー４等で行う方法である。図中、５は溶湯膜である。
この方法によれば、鋳塊３の凝固は鋳壁面上を避けて等軸晶が生成遊離する機会のないうちに徐々に進行し、また、加熱鋳型１内の温度分布を適切に選択することによって、加熱鋳型１内に突出するような形状の凝固界面を作らせることができるので、鋳塊３の中心部が先に凝固し、その際溶湯中の非金属介在物は鋳塊３の先端に閉じ込められることがなく溶湯中に存在し続け、最後に薄い表面層だけが加熱鋳型１のすぐ外で凝固することになり、鋳壁上における結晶の生成遊離を完全に阻止できることにより、等軸晶が全くなく非金属介在物をほとんど含有しない完全な一方向凝固組織からなる鋳塊３を得ることができる。しかも、この方法は、新たな結晶が生成される機会がないために、結晶は成長するにつれ競争によってその数を減ずるだけであるから、単結晶からなる鋳塊が極めて容易に得られるし、また、丸とか四角の断面はもちろん、種々の断面形状をもった材料を、直接、鋳造によって作ることができ、さらに塑性加工が困難な堅くて脆い合金の管や板を直接連続的につくることができる等の特徴を有する。
O. according to the present invention. C. C. As shown in FIG. 1, the principle of the process is as follows. Instead of the conventional cooling mold, the heating mold 1 in which the heater 1a is embedded is used, and the temperature of the inner wall surface of the mold is solidified by the molten metal (cast metal) 2. This is a method in which the ingot 3 is cooled by a cooling water spray 4 or the like disposed outside the heating mold 1 while being kept at a temperature or higher. In the figure, 5 is a molten metal film.
According to this method, solidification of the ingot 3 proceeds gradually before the opportunity to generate and release equiaxed crystals while avoiding the cast wall surface, and the temperature distribution in the heating mold 1 is appropriately selected. Thus, a solidification interface having a shape protruding into the heating mold 1 can be formed, so that the central portion of the ingot 3 is solidified first, and the non-metallic inclusions in the molten metal are at the tip of the ingot 3. It is not confined to the molten metal and continues to exist in the molten metal, and finally, only a thin surface layer is solidified just outside the heating mold 1, and it is possible to completely prevent crystal formation and liberation on the cast wall. An ingot 3 consisting of a completely unidirectionally solidified structure with no crystals and almost no nonmetallic inclusions can be obtained. Moreover, since this method has no opportunity to generate new crystals, the number of crystals is only reduced by competition as they grow, so an ingot made of a single crystal can be obtained very easily. In addition to round and square cross-sections, materials with various cross-sectional shapes can be made directly by casting, and solid and brittle alloy pipes and plates that are difficult to machine can be made directly and continuously. It has features such as being able to.
本発明方法は、上記Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織からなる連続鋳造鋳片を用いて蓄圧式燃料噴射システム用高圧燃料配管を製造する方法であり、その第１の製造方法は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる丸棒をマンネスマン・マンドレル方式やマンネスマン・プラグミル方式にて軸方向に穿孔して素管とし、該素管を伸管工程で例えばプラグ／ダイスを用いて縮径方向および管軸方向に圧延する。次いで伸管されて高い引張り応力の残留した素管を熱処理工程で再結晶温度以上に加熱して結晶粒を再結晶させる。さらに必要に応じて前記伸管工程および熱処理工程を複数回繰り返して、所定の寸法（外径、内径、肉厚）の継目無鋼管に仕上げる。
第２の製造方法は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる丸棒をマンネスマン・マンドレル方式やマンネスマン・プラグミル方式にて管軸方向に穿孔して素管とした後、伸管加工品を熱処理工程にて再結晶温度以上に加熱して結晶粒を再結晶させる。次いで、この再結晶させた管を管軸方向に伸管、熱処理して継目無鋼管に仕上げる。
第３の製造方法は、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造された一方向凝固組織のみからなる丸棒を縮径および／または軸方向に圧延後切断して鍛造素材とした後、該鍛造素材を鍛造加工し、さらに熱処理工程にて再結晶温度以上に加熱して結晶粒を再結晶させる。次いで、この再結晶させた鍛造材を軸方向に穿孔してコモンレールに仕上げる。
The method of the present invention comprises the above O.D. C. C. This is a method of manufacturing a high-pressure fuel pipe for an accumulator fuel injection system using a continuous cast slab made of a unidirectionally solidified structure continuously cast by a process. C. C. A round bar made only of a unidirectionally solidified structure continuously cast by a process is drilled in the axial direction by a Mannesmann mandrel method or a Mannesmann plug mill method to form a raw tube. It rolls in a diameter reduction direction and a pipe axis direction using a die. Next, the raw tube, which has been drawn and has a high tensile stress remaining, is heated above the recrystallization temperature in a heat treatment step to recrystallize the crystal grains. Further, if necessary, the drawing process and the heat treatment process are repeated a plurality of times to finish a seamless steel pipe having a predetermined dimension (outer diameter, inner diameter, wall thickness).
The second manufacturing method is O.D. C. C. A round bar consisting only of a unidirectionally solidified structure continuously cast by the process is drilled in the axial direction by the Mannesmann mandrel method or Mannesman plug mill method to form a blank tube, and then the drawn tube product is used in the heat treatment process. The crystal grains are recrystallized by heating above the recrystallization temperature. Next, this recrystallized tube is drawn in the tube axis direction and heat-treated to finish it into a seamless steel tube.
The third production method is described in O.D. C. C. A round bar made only of a unidirectionally solidified structure continuously cast by a process is reduced in diameter and / or axially and then cut into a forged material, and then the forged material is forged and further subjected to a heat treatment process. The crystal grains are recrystallized by heating above the recrystallization temperature. Next, the recrystallized forged material is drilled in the axial direction to finish a common rail.
上記第１〜第２の方法により製造した後は、その原管を所定の長さに切断し、例えば端末成形及び曲げ加工を施して高圧燃料噴射管としたり、前記原管に機械加工および／または分岐金具あるいは分岐管をろう付けもしくは溶接加工を施してコモンレールとする。
なお、高圧燃料噴射管やコモンレールの場合は、必要に応じてオートフレッテージ処理を施してもよい。
After being manufactured by the above first and second methods, the original pipe is cut into a predetermined length and subjected to, for example, terminal molding and bending to form a high-pressure fuel injection pipe. Alternatively, a branch rail or a branch pipe is brazed or welded to form a common rail.
In the case of a high-pressure fuel injection pipe or a common rail, autofrettage processing may be performed as necessary.
ＪＩＳ ＳＴＳ−４８０の溶鋼を用い、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造して一方向凝固組織からなる丸棒を製造し、次いで該丸棒をマンネスマン・マンドレル方式にて軸方向に穿孔して素管とし、この素管を伸管工程でプラグダイスを使用して縮径方向および管軸方向に圧延した後、熱処理工程で当該鋼の再結晶温度以上（８００℃以上）に加熱して結晶粒を再結晶させ、さらに前記伸管工程および熱処理工程を繰り返して外径φ８．０ｍｍ、内径φ３．０ｍｍ、肉厚ｔ２．５ｍｍの高圧燃料噴射管用鋼管を製造し、該鋼管を長さ３５０ｍｍに切断し、頭部成形した後曲げ加工を施して高圧燃料噴射管を得た。そして、さらに得られた高圧燃料噴射管内に３０００ｂａｒの高圧水を封じ込んでオートフレッテージ処理を施した。
オートフレッテージ未処理の燃料噴射管と、オートフレッテージ処理を施した高圧燃料噴射管の内圧疲労強度を調べた結果を表１に示す。
Using molten steel of JIS STS-480, O.D. C. C. A round bar made of a unidirectionally solidified structure is manufactured by continuous casting according to the process, and then the round bar is drilled in the axial direction by the Mannesmann mandrel method to form a raw pipe, and this raw pipe is plugged in the drawing process. After rolling in the direction of diameter reduction and tube axis using a die, the crystal grains are recrystallized by heating to a temperature higher than the recrystallization temperature of the steel (800 ° C. or higher) in the heat treatment step, and the tube drawing step and heat treatment are further performed. The process is repeated to produce a steel pipe for a high-pressure fuel injection pipe having an outer diameter of φ8.0 mm, an inner diameter of φ3.0 mm, and a wall thickness of t2.5 mm. The steel pipe is cut into a length of 350 mm, the head is molded, and then subjected to bending. A high pressure fuel injection tube was obtained. Then, 3000 bar of high-pressure water was sealed in the obtained high-pressure fuel injection pipe, and an auto-frettage treatment was performed.
Table 1 shows the results of examining the internal pressure fatigue strength of the fuel injection pipes that have not been subjected to auto-frettage processing and the high-pressure fuel injection pipe that has been subjected to auto-frettage processing.
ＪＩＳ ＳＴＳ−４１０の溶鋼を用い、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造して一方向凝固組織からなる丸棒を製造し、この丸棒をマンネスマン・プラグミル方式にて軸方向に穿孔して素管とし、次いで該素管に伸管工程および熱処理工程を繰り返して管状部の外径φ３２ｍｍ、内径φ１０ｍｍ、肉厚ｔ１１ｍｍの管材としてコモンレール用素材とし、この素材を熱処理工程で当該鋼の再結晶温度以上（８００℃以上）に加熱して結晶粒を再結晶させ、さらに特開平１０−３１８０８３号に記載されている内周面への圧縮応力の残留加工を実施した後、φ３．０ｍｍの分岐孔を穿孔し、頂部に頂角６０度の円錐状シート面を形成し、外周にリテーナ（分岐管継手金具）を装着して得られたコモンレールに、さらに４０００ｂａｒの高圧水を封じ込んでオートフレッテージ処理を施した。
オートフレッテージ未処理のコモンレールと、オートフレッテージ処理を施したコモンレールの内圧疲労強度を調べた結果を表１に併せて示す。
Using molten steel of JIS STS-410, O.D. C. C. A round bar made of a unidirectionally solidified structure is manufactured by continuous casting according to the process, and this round bar is drilled in the axial direction by a Mannesmann plug mill method to form a raw pipe, and then the pipe is drawn and heat treated. Repeat the process to make the tube material with the outer diameter φ32mm, the inner diameter φ10mm, and the wall thickness t11mm of the tubular part, and heat the material to the recrystallization temperature or higher (800 ° C or higher) of the steel in the heat treatment step. After recrystallizing and further carrying out the residual processing of compressive stress on the inner peripheral surface described in JP-A-10-318083, a φ3.0 mm branch hole is drilled, and the apex has a conical shape with an apex angle of 60 degrees A common rail obtained by forming a seat surface and mounting a retainer (branch fitting metal fitting) on the outer periphery was further sealed with 4000 bar of high-pressure water and subjected to auto-fretting treatment.
Table 1 also shows the results of examining the internal pressure fatigue strength of the common rail that has not been subjected to auto-frettage processing and the common rail that has been subjected to auto-frettage processing.
ＪＩＳ ＳＴＳ−４１０の溶鋼を用い、Ｏ．Ｃ．Ｃ．プロセスによって連続的に鋳造して一方向凝固組織からなる丸棒を製造し、この丸棒を押出しおよび／または引抜き加工しかつ切断して鍛造素材を製造し、この鍛造素材を型鍛造して外径φ３２ｍｍの本体部に外径φ１８ｍｍのボス部を多数突出させ、かつ複数のブラケット部を形成してコモンレール用素材とし、この素材を熱処理工程で当該鋼の再結晶温度以上（８００℃以上）に加熱して結晶粒を再結晶させた後、内径φ１０ｍｍのガンドリル加工を施し、さらに特開平１０−３１８０８３号に記載されている内周面への圧縮応力の残留加工を実施した後、各ボス部にＭ１６の雄ねじ加工とその頂部に頂角６０度の円錐状シート面を形成するとともに、当該ボス部にφ３ｍｍの分岐孔を穿孔し、最終仕上げ加工を施して得られたコモンレールに、さらに４０００ｂａｒの高圧水を封じ込んでオートフレッテージ処理を施した。
オートフレッテージ未処理のコモンレールと、オートフレッテージ処理を施したコモンレールの内圧疲労強度を調べた結果を表１に併せて示す。
［比較例１］
Using molten steel of JIS STS-410, O.D. C. C. A round bar made of a unidirectionally solidified structure is produced by continuous casting according to a process, and this round bar is extruded and / or drawn and cut to produce a forged material. A large number of bosses with an outer diameter of φ18 mm protrude from the main body with a diameter of φ32 mm, and a plurality of brackets are formed as a material for a common rail. This material is heated to a temperature higher than the recrystallization temperature of the steel (800 ° C or higher) in the heat treatment process. After recrystallizing the crystal grains by heating, after performing gun drilling with an inner diameter of φ10 mm and further carrying out residual processing of compressive stress on the inner peripheral surface described in JP-A-10-318083, each boss part In addition to forming a M16 male thread and a conical sheet surface with an apex angle of 60 degrees on the top, a φ3 mm branch hole is drilled in the boss and the final finish is applied to the common In, was subjected to autofrettage treatment further Fujikon high pressure water 4000 bar.
Table 1 also shows the results of examining the internal pressure fatigue strength of the common rail that has not been subjected to auto-frettage processing and the common rail that has been subjected to auto-frettage processing.
[Comparative Example 1]
ＪＩＳ ＳＴＳ−４８０の溶鋼を用い、通常の連続鋳造装置により製造された丸棒をマンネスマン・マンドレル方式にて管軸方向に穿孔して素管とし、該素管より実施例２と同じ寸法の燃料噴射管用鋼管を製造し、該鋼管を長さ３５０ｍｍに切断し、頭部成形した後曲げ加工を施して燃料噴射管を得た。
得られた燃料噴射管の内圧疲労強度を調べた結果を表１に併せて示す。
〔比較例２〕
Using a molten steel of JIS STS-480, a round bar manufactured by a normal continuous casting apparatus is drilled in the direction of the pipe axis by the Mannesmann mandrel method to form a raw pipe. A steel pipe for an injection pipe was manufactured, the steel pipe was cut into a length of 350 mm, a head part was formed, and then bending was performed to obtain a fuel injection pipe.
The results of examining the internal pressure fatigue strength of the obtained fuel injection pipe are also shown in Table 1.
[Comparative Example 2]
ＪＩＳ ＳＴＳ−４１０の溶鋼を用い、通常の連続鋳造装置により製造された丸棒をマンネスマン・マンドレル方式にて管軸方向に穿孔して素管とし、該素管より実施例２と同じ寸法のコモンレールを得た。
得られたコモンレールの内圧疲労強度を調べた結果を表１に併せて示す。
Using JIS STS-410 molten steel, a round bar manufactured by a normal continuous casting machine is drilled in the direction of the pipe axis by the Mannesmann mandrel method to form a raw pipe. Got.
The results of examining the internal pressure fatigue strength of the obtained common rail are also shown in Table 1.
表１に示す結果より明らかなごとく、本発明法による蓄圧式燃料噴射システム用高圧燃料配管はいずれも、等軸晶の全くない、一方向凝固組織のみからなる継目無鋼管素材用連続鋳造鋳片を素材としているため、非金属介在物が極めて少なく、機械的強度および内圧疲労強度共に優れている。 As is apparent from the results shown in Table 1, all of the high-pressure fuel pipes for the accumulator fuel injection system according to the present invention are continuously cast slabs for seamless steel pipe materials having no equiaxed crystals and consisting only of unidirectionally solidified structures. Therefore, there are very few non-metallic inclusions, and both mechanical strength and internal pressure fatigue strength are excellent.
本発明の蓄圧式燃料噴射システム用高圧燃料配管は、等軸晶の全くない、一方向凝固組織のみからなる継目無鋼管素材用連続鋳造鋳片を素材としているため、非金属介在物が極めて少なく、引張応力が加わっても応力集中が発生せず内圧疲労強度が優れ、高い信頼性が得られる。
また、本発明方法は、等軸晶の全くない、一方向凝固組織のみからなる継目無鋼管素材用連続鋳造鋳片を素材とし、該素材を伸管、鍛造、圧延等の塑性加工を施した後に再結晶温度以上に加熱して軸方向に連続していた結晶粒を再結晶させるので、機械的強度の高い高圧燃料配管が得られる。さらに、本発明方法によれば、配管の内面およびその表面直下に非金属介在物が存在しないので、引張応力が加わっても応力集中が発生せず、疲労強度も低下することなく内圧疲労強度の優れた信頼性の高い高圧燃料配管を得ることができる。
したがって、本発明の蓄圧式燃料噴射システム用高圧燃料配管は、ディーゼルエンジン用の蓄圧式燃料噴射システムに組込まれるコモンレールや、ポンプ〜コモンレール間およびコモンレール〜インジェクタ間に配設される燃料噴射管等からなる高圧燃料配管のみならず、他の高圧流体用配管にも十分に適用できる。
The high-pressure fuel pipe for an accumulator fuel injection system according to the present invention is made of continuous cast slabs for seamless steel pipe material consisting of only a unidirectionally solidified structure without any equiaxed crystals, so there are very few non-metallic inclusions. Even if tensile stress is applied, stress concentration does not occur, the internal pressure fatigue strength is excellent, and high reliability is obtained.
In addition, the method of the present invention uses a continuous cast slab for a seamless steel pipe material made of only a unidirectionally solidified structure without any equiaxed crystal, and the material was subjected to plastic working such as drawn pipe, forging, and rolling. Since the crystal grains that have been continuously heated in the axial direction are recrystallized by heating to a temperature higher than the recrystallization temperature later, a high-pressure fuel pipe with high mechanical strength can be obtained. Furthermore, according to the method of the present invention, since there are no non-metallic inclusions on the inner surface of the pipe and immediately below the surface, stress concentration does not occur even if tensile stress is applied, and the internal pressure fatigue strength does not decrease without reducing the fatigue strength. An excellent and reliable high-pressure fuel pipe can be obtained.
Accordingly, the high-pressure fuel pipe for the accumulator fuel injection system according to the present invention includes a common rail incorporated in the accumulator fuel injection system for a diesel engine, a fuel injection pipe disposed between the pump and the common rail, and between the common rail and the injector. The present invention can be sufficiently applied not only to the high-pressure fuel pipe as described above but also to other high-pressure fluid pipes.
１ 加熱鋳型
１ａ ヒーター
２ 溶湯（鋳造金属）
３ 鋳塊
４ 冷却水スプレー
５ 溶湯膜
1 Heating
3 Ingot 4
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