JP2007301604A

JP2007301604A - Process design method and forging control method in ring forging

Info

Publication number: JP2007301604A
Application number: JP2006132873A
Authority: JP
Inventors: Hideki Kakimoto; 英樹柿本; Takanori Kagawa; 恭徳香川
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 2006-05-11
Filing date: 2006-05-11
Publication date: 2007-11-22
Anticipated expiration: 2026-05-11
Also published as: JP4783202B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a design method of a forging process, in which a right cylindrical shell such as a main body of a large-sized pressure container is effectively formed in a target shape by ring forging while drop in yield is prevented, and a forging control method using it. <P>SOLUTION: The design method of a forging process comprises: a step of setting an outer diameter D1, wall thickness T1, length L1, target rolling draft S, and rolling draft P per go-around when starting forging of a large-sized ring material; a step of determining the number of necessary go-around N; and a step of preparing a prediction formula which formulates the outer diameter D2 and the length L2 after deformation (enlarged diameter) for every go-around of the large-sized ring material and is corrected by forge data of an actual device. This design method controls the outer diameter and the length in the ring forging process of the actual device using the predicted outer diameter D2 and the length L2 per go-around. As a result, precise prediction for the outer diameter and the length of a forging finish material is possible, to thereby effectively determine material shapes or forging conditions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

この発明は、リアクターなどの、円筒状の端部が口絞りされた圧力容器用大型リング部材の鍛造工程設計方法とこの工程設計方法を用いた鍛造制御方法に関する。 The present invention relates to a forging process design method for a large ring member for a pressure vessel having a cylindrical end portion squeezed, such as a reactor, and a forging control method using this process design method.

化工機器用リアクターや原子力用圧力容器などの大型圧力容器は、その本体部の直円筒状シェル（ストレートシェル）の端部に設けた口絞り部に、半球形状の鏡板が接合されて形成されている。この直円筒状シェル（ストレートシェル）の鍛造はリング鍛造方法によって行なわれる。このリング鍛造方法は、図６に模式的に平面図を示すように、所定温度に加熱されたリング状素材１に芯金２を挿入し、鍛造プレスのプレスヘッドに固定した上金敷３により芯金２との間でリング状素材１を圧下して材料を円周方向に流動させ、芯金２を一定角度回転させることにより圧下領域を移動させて、この圧下を、肉厚および外径寸法が目標寸法となるまで、リング状素材１の全周にわたって通常数周程度、圧下を繰り返すことにより所定形状に成形する逐次鍛造方法である。このようなリング鍛造装置は、例えば、特許文献１に開示されている。このリング鍛造による成形工程は拡径工程と呼ばれ、従来、この拡径工程の設計は、鍛造前後で、前記直円筒状シェルの断面積の変化がなく長手方向（軸方向）にも変化しないとして行なわれていた。
特開昭６１−２３２０３３号公報 Large pressure vessels such as reactors for chemical equipment and nuclear pressure vessels are formed by joining a hemispherical end plate to the mouthpiece provided at the end of a straight cylindrical shell (straight shell) of the main body. Yes. The forging of the straight cylindrical shell (straight shell) is performed by a ring forging method. In this ring forging method, as shown schematically in a plan view in FIG. 6, a core metal 2 is inserted into a ring-shaped material 1 heated to a predetermined temperature and fixed to a press head of a forging press by a core metal 3. The ring-shaped material 1 is squeezed between the metal 2 to cause the material to flow in the circumferential direction, and the core metal 2 is rotated by a certain angle to move the squeezed region. This is a sequential forging method in which the rolling is repeatedly formed on the ring-shaped material 1 until it reaches the target dimension, and is usually formed into a predetermined shape by repeating the reduction. Such a ring forging device is disclosed in Patent Document 1, for example. This forming process by ring forging is called a diameter expansion process. Conventionally, the design of this diameter expansion process is the same before and after forging, and there is no change in the cross-sectional area of the straight cylindrical shell and no change in the longitudinal direction (axial direction). It was done as.
JP-A-61-232033

しかし、前記直円筒状シェルの形状は、外径Φ３０００〜Φ６０００ｍｍ、肉厚１５０〜５００ｍｍ、長さ２５００〜４０００ｍｍとその寸法範囲が幅広く、鍛造加工条件によって、拡径に伴い、直円筒状シェルの断面積が変化し、長手方向に伸縮する可能性があり、適正形状が得られないおそれがある。一般に、大型圧力容器などの鍛造製品では、鍛造工程設計は、工程設計者の経験と実機における試作の繰り返しにより行なわれているため、短期間での製品製造可否判断を行なうことができず、歩留も低下し、コストアップの原因となっていた。 However, the shape of the straight cylindrical shell has an outer diameter of Φ3000 to Φ6000 mm, a wall thickness of 150 to 500 mm, a length of 2500 to 4000 mm, and a wide range of dimensions. The cross-sectional area changes, and there is a possibility that it expands and contracts in the longitudinal direction, and there is a possibility that an appropriate shape cannot be obtained. In general, forging products such as large pressure vessels, the forging process design is carried out based on the experience of the process designer and repeated trial production on the actual machine, so it is not possible to determine whether or not the product can be manufactured in a short period of time. Yield also declined, causing cost increases.

そこで、この発明の課題は、大型圧力容器の本体部などの直円筒状シェルをリング鍛造により成形する場合に、鍛造過程での被成形材の形状予測を取り入れて、効率よく目標形状に成形し、歩留低下を防止することが可能な鍛造工程設計法方法と、それを用いた鍛造制御方法を提供することである。 Therefore, the subject of the present invention is that when a straight cylindrical shell such as a main body of a large pressure vessel is formed by ring forging, the shape of the material to be molded in the forging process is incorporated and the target shape is efficiently formed. Another object is to provide a forging process design method capable of preventing the yield reduction and a forging control method using the same.

前記の課題を解決するために、この発明では以下の構成を採用したのである。 In order to solve the above problems, the present invention employs the following configuration.

請求項１に係るリング鍛造における工程設計方法は、芯金により大型リング材の内周面を支持し、この大型リング材の外周面を金敷により加圧して大型リング材を回転させることにより圧下領域を移動させて大型リング材の全周にわたって所要の周回数だけ圧下を繰り返すことにより、所定の形状に拡径するリング鍛造における工程設計方法であって、前記大型リング材の鍛造開始時の外径Ｄ１、肉厚Ｔ１および長さＬ１と、目標圧下量Ｓと、１周回あたりの圧下量Ｐを設定するステップと、必要周回数Ｎを決定するステップと、前記大型リング材の１周回ごとの変形後の外径Ｄ２および長さＬ２を定式化し、この定式を実機鍛造データにより修正した予測式を用いて前記外径Ｄ２および長さＬ２をそれぞれ予測するステップを備えたことを特徴とする。 In the process design method in ring forging according to claim 1, the inner peripheral surface of a large ring material is supported by a core metal, the outer peripheral surface of the large ring material is pressed by an anvil, and the large ring material is rotated to thereby reduce the rolling region. Is a process design method in ring forging in which the diameter is expanded to a predetermined shape by repeating the required number of rounds over the entire circumference of the large ring material, and the outer diameter at the start of forging of the large ring material D1, thickness T1 and length L1, target reduction amount S, step of setting reduction amount P per round, step of determining required number of rounds N, and deformation of the large ring material per round The step of formulating a rear outer diameter D2 and a length L2 and predicting the outer diameter D2 and the length L2 using prediction formulas obtained by correcting this formula using actual machine forging data are provided. And butterflies.

このように、大型リング材の鍛造時に、周回ごとに、前記リング材の外径および長さを予測できるため、目標形状を得るための圧下量や周回数など鍛造条件を効率よく決定することができる。そして、予測した外径および長さを、実機リング鍛造時の周回ごとの目標寸法とすることができる。 Thus, since the outer diameter and length of the ring material can be predicted for each turn during forging of the large ring material, it is possible to efficiently determine forging conditions such as the amount of rolling and the number of turns for obtaining the target shape. it can. And the estimated outer diameter and length can be made into the target dimension for every round at the time of a real machine ring forge.

請求項２に係るリング鍛造における工程設計方法は、前記変形後の外径Ｄ２を以下の（１）式および（２）式を用いて、前記変形後の長さＬ２を以下の（３）式、（４）式および（５）式を用いてそれぞれ予測することを特徴とする。
Ｄ２＝ｆ（Ｄ２ｃ）-------------------------------------（１）
Ｄ２ｃ＝Ｔ２＋（Ｔ１／Ｔ２）×（Ｄ１−Ｔ１）-----------（２）
Ｌ２＝Ｌ１×ｅｘｐ（−ｇ（ε_θｃ）−ε_ｔ）--------------（３）
ε_θｃ＝ｌｎ（（Ｄ２−Ｔ２）／（Ｄ１−Ｔ１））----------（４）
ε_ｔ＝ｌｎ（Ｔ２／Ｔ１）--------------------------------（５）
ここで、Ｄ１およびＴ１は、鍛造開始時（素材）の外径および肉厚を、Ｔ２は変形（拡径）後の肉厚を、ε_θｃは円周方向のひずみ（以下、円周ひずみと記す）を、ε_ｔは肉厚方向（半径方向）のひずみ（以下、肉厚ひずみと記す）をそれぞれ示し、ｆ（Ｄ２ｃ）およびｇ（ε_θｃ）は、大型リング材の材質に依存する関数である。 The process design method in the ring forging according to claim 2 uses the following expression (1) and (2) as the outer diameter D2 after deformation, and sets the length L2 after deformation as the following expression (3). , (4) and (5) are used for prediction, respectively.
D2 = f (D2c) ------------------------------- (1)
D2c = T2 + (T1 / T2) × (D1-T1) --------- (2)
L2 = L1 × exp (−g (ε _θ c) −ε _t ) ------------- (3)
ε _θ c = ln ((D2-T2) / (D1-T1)) --------- (4)
ε _t = ln (T2 / T1) -------------------------------- (5)
Here, D1 and T1 are the outer diameter and thickness at the start of forging (material), T2 is the thickness after deformation (expansion), and ε _θ c is the strain in the circumferential direction (hereinafter referred to as circumferential strain). Ε _t indicates the strain in the thickness direction (radial direction) (hereinafter referred to as the thickness strain), and f (D2c) and g (ε _θ c) depend on the material of the large ring material Function.

前記大型リング材のリング鍛造後の形状予測を高精度に行なうためには、大型リング材の素材形状と鍛造条件（圧下量）から、鍛造形状の長手方向すなわち大型リング材の軸方向の伸縮を予測する必要がある。拡径工程内で体積一定則が成り立つと仮定すると、以下の（６）式が成立する。（６）式で、ε_ｔは肉厚ひずみ、ε_θは円周ひずみ、ε_ｌは長さ方向のひずみ（以下、長さひずみと記す）である。
ε_ｔ＋ε_θ＋ε_ｌ＝０ ----------------（６）
（６）式の肉厚ひずみε_ｔは前記（５）式により、また、長さひずみε_ｌは、（７）式でそれぞれ表わすことができる。
ε_ｔ＝ｌｎ（Ｔ２／Ｔ１）--------------（５）
ε_ｌ＝ｌｎ（Ｌ２／Ｌ１）--------------（７）
また、円周ひずみε_θを拡径前後の平均直径（Ｄ１−Ｔ１）および（Ｄ２−Ｔ２）で表すと、（８）式のように定式化される。
ε_θｃ＝ｌｎ（（Ｄ２−Ｔ２）／（Ｄ１−Ｔ１））-----------（８）
拡径前後の断面積が変化しないと仮定すると、拡径後の外径Ｄ２ｃは、上記の（２）式のように定式化される。
Ｄ２ｃ＝Ｔ２＋（Ｔ１／Ｔ２）×（Ｄ１−Ｔ１）------（２）
図１は、上記（２）式で算出した拡径後の外径Ｄ２ｃに対して、Ｃｒ−Ｍｏ鋼等の圧力容器用の大型リング材の実機鍛造時に測定した外径Ｄ２ａをプロットした結果である。図１から、算出外径Ｄ２ｃと実測外径Ｄ２ａとは良好な相関を示し、測定した外径Ｄ２ａと算出外径Ｄ２ｃとの関係は（９）式で表すことができる。
Ｄ２ａ＝０．９９２８×Ｄ２ｃ＋４４．８２＝ｆ（Ｄ２ｃ）------------（９）
したがって、拡径後（変形後）の外径Ｄ２は、（２）式で得られる算出外径Ｄ２ｃを用いて、（１）式に示したように、予測することが可能である。
Ｄ２＝ｆ（Ｄ２ｃ）-------------------------------------（１）
算出外径Ｄ２ｃを用いて、（９）式により求めたＤａをＤ２として、一般には（１）式により求めたＤ２を上記（４）式に代入すれば、円周ひずみε_θｃを求めることができる。 In order to predict the shape of the large ring material after ring forging with high accuracy, the longitudinal direction of the forged shape, that is, the axial direction of the large ring material, is extended from the material shape of the large ring material and the forging conditions (rolling amount). Need to predict. Assuming that the constant volume rule is established in the diameter expansion process, the following equation (6) is established. In Equation (6), ε _t is a thickness strain, ε _θ is a circumferential strain, and ε _l is a strain in the length direction (hereinafter referred to as a length strain).
ε _t + ε _θ + ε _l = 0 (6)
The thickness strain ε _{t in the} equation (6) can be expressed by the above equation (5), and the length strain ε _l can be expressed by the equation (7).
ε _t = ln (T2 / T1) ------------- (5)
ε _l = ln (L2 / L1) ------------- (7)
Further, when the circumferential strain ε _θ is expressed by average diameters before and after the diameter expansion (D1-T1) and (D2-T2), it is formulated as shown in the equation (8).
ε _θ c = ln ((D2-T2) / (D1-T1)) ---------- (8)
Assuming that the cross-sectional area before and after the diameter expansion does not change, the outer diameter D2c after the diameter expansion is formulated as in the above equation (2).
D2c = T2 + (T1 / T2) × (D1-T1) ----- (2)
FIG. 1 is a result of plotting the outer diameter D2a measured at the time of actual forging of a large ring material for a pressure vessel such as Cr-Mo steel against the outer diameter D2c after the diameter expansion calculated by the above equation (2). is there. From FIG. 1, the calculated outer diameter D2c and the measured outer diameter D2a show a good correlation, and the relationship between the measured outer diameter D2a and the calculated outer diameter D2c can be expressed by Equation (9).
D2a = 0.9928 × D2c + 44.82 = f (D2c) ----------- (9)
Therefore, the outer diameter D2 after diameter expansion (after deformation) can be predicted as shown in the expression (1) using the calculated outer diameter D2c obtained by the expression (2).
D2 = f (D2c) ------------------------------- (1)
Using the calculated outer diameter D2c, Da obtained by the equation (9) is set as D2, and generally when the D2 obtained by the equation (1) is substituted into the above equation (4), the circumferential strain ε _θ c is obtained. Can do.

図２は、上記（５）式〜（７）式から得られる理論値の円周ひずみε_θ（＝−ε_ｔ−ε_ｌ）に対して、実機寸法測定結果と上記定式化した（８）式から得られる円周ひずみε_θｃをプロットした結果である。（５）式の肉厚ひずみε_ｔおよび（７）式の長さひずみε_ｌは、いずれも実測寸法から求めたものである。図２から、前記の理論円周ひずみε_θと実機寸法測定結果を用いて（８）式から求めた計算円周ひずみε_θｃとは、円周ひずみが大きくなるに伴って差が生じてくるが、図２中に示したように、（１０）式に示す２次式で近似することにより、ε_θとε_θｃとに良好な相関が認められる。
ε_θ＝−０．２９８７×（ε_θｃ）^２＋１．０７０２×ε_θｃ＝ｇ（ε_θｃ）
-----（１０）
したがって、円周ひずみε_θは、（４）式で得られる円周ひずみε_θｃを用いて、一般には（１１）式に示すように、予測することが可能である。
ε_θ＝ｇ（ε_θｃ）-----------------------------------------（１１）
前記円周ひずみε_θｃを用いて（１０）式により（一般には（１１）式により）予測した円周ひずみε_θおよび（５）式で算出した肉厚ひずみε_ｔを（３）式に代入すると、鍛造開始時の大型リング材（素材）の長さＬ１を用いて、鍛造後の長さＬ２を前記（３）式の予測式で予測することができる。図３は、Ｃｒ−Ｍｏ鋼等の圧力容器用の大型リング材について、前記（３）式を用いて予測した変形後の長さＬ２と実測長さＬａとを比較した結果を示したものである。同図からわかるように、予測長さＬ２は、実測長さＬａと５％以内の精度で一致することが確認された。 FIG. 2 shows the actual machine dimension measurement result and the above formula for the theoretical circumferential strain ε _θ (= −ε _t −ε _l ) obtained from the above formulas (5) to (7) (8). It is the result of plotting the circumferential strain ε _θ c obtained from the equation. The thickness strain ε _{t in the} equation (5) and the length strain ε _l in the equation (7) are both obtained from the actually measured dimensions. From FIG. 2, the theoretical circumferential strain ε _θ and the calculated circumferential strain ε _θ c obtained from the equation (8) using the actual machine dimension measurement results differ as the circumferential strain increases. come, but as shown in FIG. 2, by approximating by a quadratic expression shown in equation (10), is observed a good correlation with epsilon _theta and epsilon _theta c.
ε _θ = −0.2987 × (ε _θ c) ² + 1.0702 × ε _θ c = g (ε _θ c)
----- (10)
Therefore, the circumferential strain ε _θ can be predicted using the circumferential strain ε _θ c obtained by the equation (4), as generally shown by the equation (11).
ε _θ = g (ε _θ c) -------------------------- (11)
Using said circumferential strain epsilon _theta c (10) by equation (generally (11) by) the thickness strain epsilon _t calculated in the circumferential predicted strain epsilon _theta and (5) (3) to By substituting, the length L2 after forging can be predicted by the prediction formula (3) using the length L1 of the large ring material (raw material) at the start of forging. FIG. 3 shows the result of comparison between the deformed length L2 predicted using the equation (3) and the measured length La for a large ring material for a pressure vessel such as Cr—Mo steel. is there. As can be seen from the figure, it was confirmed that the predicted length L2 coincided with the measured length La with an accuracy within 5%.

このように、実機寸法測定結果を用いて、（１）式および（１１）式に示したように、変形（拡径）後の外径Ｄ２および円周ひずみε_θを、実機鍛造データに基づいてｆ（Ｄ２ｃ）、ｇ（ε_θｃ）のように関数化することにより、周回ごとに変形後の長さＬ２を（３）式により簡便かつ精度よく予測することができる。なお、前記ｆ（Ｄ２ｃ）、ｇ（ε_θｃ）は大型リング材の材質に依存する関数である。 Thus, by using the actual dimensions measurement result, based on (1) as shown in formula and (11), deform the outer diameter D2 and circumferential strain epsilon _theta after (diameter), the actual forging data Thus, by making a function such as f (D2c) and g (ε _θ c), the length L2 after deformation can be predicted easily and accurately by Equation (3) for each turn. Note that the f (D2c), g (ε θ c) is a function that depends on the material of the large ring material.

請求項３に係るリング鍛造における工程設計方法は、芯金により大型リング材の内周面を支持し、この大型リング材の外周面を金敷により加圧して前記大型リング材を回転させることにより圧下領域を移動させて前記大型リング材の全周にわたって所要の周回数だけ圧下を繰り返すことにより、所定の形状に拡径するリング鍛造における鍛造制御方法であって、請求項２に記載した工程設計方法を用いて前記大型リング材の１周回ごとの変形後の外径Ｄ２および長さＬ２を予測し、前記１周回ごとの大型リング材の、外径Ｄ２ａ、長さＬ２ａおよび肉厚Ｔ２ａを計測し、この計測した外径Ｄ２ａおよび長さＬ２ａと、前記予測した外径Ｄ２およびＬ２をそれぞれ比較し、計測した外径Ｄ２ａおよび長さＬ２ａと予測した外径Ｄ２および長さＬ２との差ΔＤおよびΔＬが、所定の範囲にないときに、圧下量を修正し、累積圧下量が、目標圧下量Ｓに達したときに鍛造を終了するようにしたことを特徴とする。 A process design method in ring forging according to claim 3 is a method in which the inner peripheral surface of a large ring material is supported by a core metal, the outer peripheral surface of the large ring material is pressed by an anvil and the large ring material is rotated. The process design method according to claim 2, wherein the forging control method is for ring forging in which the diameter is expanded to a predetermined shape by moving a region and repeating the reduction for a predetermined number of times over the entire circumference of the large ring material. Is used to predict the outer diameter D2 and length L2 of the large ring material after deformation for each round, and measure the outer diameter D2a, length L2a and wall thickness T2a of the large ring material for each round. The measured outer diameter D2a and length L2a are compared with the predicted outer diameter D2 and L2, respectively, and the measured outer diameter D2a and length L2a are predicted as the outer diameter D2 and length L. The difference ΔD and ΔL and is, when not in the predetermined range, to correct the pressure amount, a cumulative reduction ratio, characterized in that so as to end the forged when it reaches the target pressure amount S.

このように、上記の工程設計方法により、１周回ごとの外径Ｄ２および長さＬ２を予測してそれぞれ目標外径および目標長さとし、この目標外径および目標長さと実機リング鍛造における１周回ごとの実測外径および長さと比較して圧下量を調節することにより、実機リング鍛造において外径および長さを簡便かつ精度よく制御することができる。 Thus, by the above process design method, the outer diameter D2 and the length L2 for each turn are predicted and set as the target outer diameter and the target length, respectively, and the target outer diameter and the target length and each turn in the actual ring forging. By adjusting the amount of reduction compared to the actually measured outer diameter and length, the outer diameter and length can be controlled easily and accurately in actual ring forging.

この発明では、大型リング材のリング鍛造過程で、予め実機鍛造時の寸法測定結果に基づいて補正した外径の予測式および長さの予測式を用いて、周回ごとに外径および長さを予測できるようにしたので、目標形状を得るための素材形状および圧下量や周回数などの鍛造条件を効率よく決定し、歩留低下を防止することができる。また、予測した外径および長さを、実機リング鍛造時の周回ごとの目標寸法として、実機リング鍛造における１周回ごとの実測外径および長さと比較して圧下量を調節することにより、実機リング鍛造において外径および長さを簡便かつ精度よく制御することができる。 In this invention, in the ring forging process of the large ring material, the outer diameter and the length are determined for each turn using the prediction formula for the outer diameter and the prediction formula for the length, which are corrected based on the dimension measurement result at the time of actual machine forging. Since the prediction can be performed, the material shape for obtaining the target shape and the forging conditions such as the reduction amount and the number of laps can be determined efficiently, and the yield reduction can be prevented. In addition, the predicted outer diameter and length are set as target dimensions for each turn during actual ring forging, and the actual ring is adjusted by adjusting the reduction amount compared to the actually measured outer diameter and length for each turn in actual ring forging. In forging, the outer diameter and length can be easily and accurately controlled.

以下に、この発明の実施形態を添付の図４および図５に基づいて説明する。 Hereinafter, embodiments of the present invention will be described with reference to FIGS. 4 and 5.

図４は、実施形態のリング鍛造における工程設計方法の流れを示したものである。まず、大型リング素材（鍛造開始時形状）の外径Ｄ１、肉厚Ｔ１、長さＬ１、目標圧下量Ｓ、および１周回あたりの圧下量Ｐを設定する（Ｓ１０）。この１周回あたりの圧下量Ｐは、鍛造荷重などの設備的制約条件等により定められる１周回あたりの許容圧下量ＰＡを超えないように、通常、各周回で等しく設定される。そして、必要周回数Ｎ（Ｎ＝Ｓ／Ｐ）を決定する（Ｓ２０）。次に、各周回ｉ（ｉ＝１〜Ｎ）について、累積圧下量Ｐsum（ｉ）から変形後の肉厚Ｔ２（ｉ）を求め、（１）式および（２）式を用いて変形後の外径Ｄ２（ｉ）を予測し、この変形後の外径Ｄ２および肉厚Ｔ２を用いて、（３）式〜(５)式から変形後の長さＬ２（ｉ）を予測する（Ｓ３０）。各周回の過程で、累積圧下量Ｐsum（ｉ）が計算され（Ｓ４０）、この各周回後の外径Ｄ２（ｉ）および長さＬ２（ｉ）の予測は、周回数がＮに達するまで行なわれる（Ｓ５０）。そして、累積圧下量Ｐsum（ｉ）（ｉ＝１〜Ｎ）が目標圧下量Ｓに達したかどうかを判定し（Ｓ６０）、目標圧下量Ｓに達すると、各周回後の被成形材（大型リング材）の形状、すなわち外径Ｄ２（ｉ）、長さＬ２（ｉ）、肉厚Ｔ２（ｉ）が出力され（Ｓ７０）、鍛造工程設計の１サイクルが終了する。目標圧下量に達していない場合には、不足している圧下量（Ｓ−Ｐsum（Ｎ））分だけさらに鍛造を継続する（Ｓ８０）。このような鍛造工程設計方法により、拡径後の大型リング材の外径とともに、長手方向の変形、すなわち伸縮を予測することができる。また、各周回への圧下量Ｐの配分やその結果として周回数を変化させることにより、前記工程設計を最適化することも可能である。 FIG. 4 shows the flow of the process design method in the ring forging of the embodiment. First, an outer diameter D1, a wall thickness T1, a length L1, a target reduction amount S, and a reduction amount P per round are set for a large ring material (shape at the start of forging) (S10). The rolling reduction amount P per round is normally set equal in each round so as not to exceed the allowable rolling reduction PA per round determined by equipment constraints such as forging load. Then, the necessary number of rotations N (N = S / P) is determined (S20). Next, for each turn i (i = 1 to N), the thickness T2 (i) after deformation is obtained from the cumulative reduction amount Psum (i), and the deformation after the deformation is calculated using the equations (1) and (2). The outer diameter D2 (i) is predicted, and the deformed length L2 (i) is predicted from the expressions (3) to (5) using the deformed outer diameter D2 and the wall thickness T2 (S30). . In the course of each round, the cumulative reduction amount Psum (i) is calculated (S40), and the outer diameter D2 (i) and the length L2 (i) after each round are predicted until the number of rounds reaches N. (S50). Then, it is determined whether or not the cumulative reduction amount Psum (i) (i = 1 to N) has reached the target reduction amount S (S60). The shape of the ring material), that is, the outer diameter D2 (i), the length L2 (i), and the wall thickness T2 (i) are output (S70), and one cycle of the forging process design is completed. When the target reduction amount has not been reached, forging is continued for the insufficient reduction amount (S-Psum (N)) (S80). By such a forging process design method, deformation in the longitudinal direction, that is, expansion and contraction can be predicted together with the outer diameter of the large ring material after diameter expansion. It is also possible to optimize the process design by distributing the rolling amount P to each lap and changing the number of laps as a result.

図５は、上記鍛造工程設計方法を用いた実施形態の鍛造制御方法の流れを示したものである。まず、図４に示した工程設計方法の場合と同様に、鍛造開始形状（大型リング素材）の外径Ｄ１ａ、肉厚Ｔ１ａ、長さＬ１ａ、および目標圧下量Ｓ、上記鍛造設計工程で設定された１周回あたりの圧下量Ｐ（Ｐ（ｉ））および必要周回数Ｎ（Ｎ＝Ｓ／Ｐ）を設定する（Ｓ１００）。次に、上記鍛造工程設計方法のステップ（Ｓ７０）により出力した、各周回（ｉ）後の外径Ｄ２（ｉ）、長さＬ２（ｉ）、肉厚Ｔ２（ｉ）を設定する（Ｓ１１０）。次に、各周回（ｉ）（ｉ＝１〜Ｎ）について、変形後の外周Ｄ２ａ（ｉ）、長さＬ２ａ（ｉ）、肉厚Ｔ２ａ（ｉ）を計測する（Ｓ１２０）。この計測値から、まず、各周回（ｉ）における実圧下量Ｐａ（ｉ）（Ｐａ（ｉ）＝Ｔ２ａ（ｉ−１）−Ｔ２ａ（ｉ））を算出し（Ｓ１３０）、累積圧下量Ｐａsum（ｉ）を算出する（Ｓ１４０）。そして、各周回（ｉ）後の実測外径Ｄ２ａ（ｉ）、実測長さＬ２（ｉ）と、上記鍛造工程設計で出力した各周回後の外径Ｄ２（ｉ）、長さＬ２（ｉ）とを比較し、この実測外径Ｄ２ａおよび実測長さＬ２ａと、各周回後の外径Ｄ２（ｉ）および長さＬ２（ｉ）との差ΔＤおよびΔＬが目標範囲内（工程設計値の±５％以内）に収まっているかどうかを判定する（Ｓ１５０）。目標範囲内に収まっていない場合、上記Ｓ１００で設定した圧下量Ｐａを修正して次周回（ｉ＋１）における圧下量Ｐ（ｉ＋１）＝α×Ｐ（ｉ）（修正係数α＜１）とし（Ｓ１６０）、周回数Ｎを修正する（Ｓ１７０）。ここで、１周回あたりの圧下量Ｐは、通常、許容される最大圧下量を設定するため（Ｓ１００）、修正係数αは１より小さい値となる。周回数を修正した次周回（ｉ＋１）から、図４に示したように、修正した圧下量Ｐおよび周回数Ｎ（Ｓ９０）により工程設計を再度行ない、次周回（ｉ＋１）以降の各周回終了時の鍛造形状を再出力する（Ｓ７０）。そして、次周回（ｉ＋１）以降、再出力したこの鍛造形状（外径Ｄ２および長さＬ２）と実測外径Ｄ２ａおよび長さＬ２ａを比較する（Ｓ１５０）。一方、目標範囲内に収まっている場合、周回数（ｉ）が上記Ｓ１００で設定した周回数（または修正した周回数）Ｎに達しているかどうかを判定し（Ｓ１８０）、達していない場合には鍛造を継続する。設定周回数（または修正周回数）Ｎに達した場合には、実圧下量（Ｔ１−Ｔ２ａ（Ｎ））が目標圧下量Ｓに到達しているかどうかを判定する（Ｓ１９０）。目標圧下量Ｓに達していない場合、不足圧下量Ｐａu（Ｐａu＝Ｓ−Ｐsuma（Ｎ）＝Ｔ１−Ｔ２ａ（Ｎ））を算出し（Ｓ２００）、周回数を追加して不足圧下量Ｐａu分だけ鍛造を継続する。Ｎ周回目で目標圧下量Ｓに到達すると鍛造を終了する。 FIG. 5 shows the flow of the forging control method of the embodiment using the forging process design method. First, as in the case of the process design method shown in FIG. 4, the outer diameter D1a, the wall thickness T1a, the length L1a, and the target reduction amount S of the forging start shape (large ring material) are set in the forging design process. In addition, a reduction amount P (P (i)) and a necessary number N of rotations (N = S / P) are set (S100). Next, the outer diameter D2 (i), the length L2 (i), and the thickness T2 (i) after each round (i) output in step (S70) of the forging process design method are set (S110). . Next, for each round (i) (i = 1 to N), the outer circumference D2a (i), the length L2a (i), and the thickness T2a (i) after deformation are measured (S120). First, an actual reduction amount Pa (i) (Pa (i) = T2a (i-1) -T2a (i)) in each lap (i) is calculated from this measured value (S130), and the cumulative reduction amount Pasum ( i) is calculated (S140). Then, the measured outer diameter D2a (i) and measured length L2 (i) after each round (i), and the outer diameter D2 (i) and length L2 (i) after each round output in the forging process design. The difference ΔD and ΔL between the measured outer diameter D2a and the measured length L2a and the outer diameter D2 (i) and the length L2 (i) after each lap are within the target range (± It is determined whether it is within 5% (S150). If not within the target range, the reduction amount Pa set in S100 is corrected so that the reduction amount P (i + 1) = α × P (i) (correction coefficient α <1) in the next lap (i + 1) (S160). ), The number of laps N is corrected (S170). Here, the reduction amount P per round usually sets a maximum allowable reduction amount (S100), so the correction coefficient α is a value smaller than 1. From the next round (i + 1) with the corrected number of laps, as shown in FIG. 4, the process design is performed again with the corrected reduction amount P and the number of laps N (S90), and at the end of each round after the next lap (i + 1) The forging shape is output again (S70). Then, after the next round (i + 1), the forged shape (outer diameter D2 and length L2) re-outputted is compared with the actually measured outer diameter D2a and length L2a (S150). On the other hand, if it is within the target range, it is determined whether or not the number of laps (i) has reached the number of laps (or the corrected number of laps) N set in S100 (S180). Continue forging. When the set number of rotations (or the number of corrected rotations) N has been reached, it is determined whether or not the actual reduction amount (T1-T2a (N)) has reached the target reduction amount S (S190). When the target reduction amount S has not been reached, the under-reduction amount Pau (Pau = S-Psuma (N) = T1-T2a (N)) is calculated (S200), and the number of laps is added to the under-reduction amount Pau. Continue forging. Forging ends when the target reduction amount S is reached in the Nth round.

表１は、拡径開始（素材）形状が、外径Ｄ（＝Ｄ１）＝３９００ｍｍ、肉厚Ｔ（＝Ｔ１）＝８５０ｍｍ、長さＬ（＝Ｌ１）＝２７６７ｍｍのＣｒ−Ｍｏ鋼の圧力容器用大型リング材のリング鍛造に関し、上述の鍛造工程設計方法を用いて、拡径１および拡径２終了後のリング材の外径Ｄ（＝Ｄ２）、長さＬ（＝Ｌ２）および肉厚Ｔ（＝Ｔ２）を予測した結果（実施例）、ならびに拡径工程でリング材の長さが変化しないとする従来の設計手法により外径Ｄ、長さＬおよび肉厚Ｔを予測した結果（比較例）を示したものである。表２は、上記鍛造工程設計方法を用いて鍛造制御を行なった実機リング鍛造での拡径１および拡径２終了後の外径Ｄ（＝Ｄ２ａ）、肉厚Ｔ（＝Ｔ２ａ）、および長さＬ（＝Ｌ２ａ）の寸法測定結果を示したものである。表１および表２で、拡径１とは、１回目の加熱での拡径工程を示し、拡径２とは２回目の加熱での拡径工程を示す。 Table 1 shows a Cr-Mo steel pressure vessel in which the diameter expansion start (material) shape is an outer diameter D (= D1) = 3900 mm, a wall thickness T (= T1) = 850 mm, and a length L (= L1) = 2767 mm. With respect to ring forging of large ring materials, the outer diameter D (= D2), length L (= L2), and wall thickness of the ring material after the expansion 1 and expansion 2 are completed using the forging process design method described above. Results of predicting T (= T2) (Example) and results of predicting outer diameter D, length L, and wall thickness T by a conventional design method in which the length of the ring material does not change in the diameter expansion process ( Comparative example) is shown. Table 2 shows the outer diameter D (= D2a), the wall thickness T (= T2a), and the length after the expansion 1 and the expansion 2 in the actual ring forging in which forging control is performed using the forging process design method. The dimension measurement result of length L (= L2a) is shown. In Tables 1 and 2, the diameter expansion 1 indicates the diameter expansion process in the first heating, and the diameter expansion 2 indicates the diameter expansion process in the second heating.

表１からわかるように、実施例の鍛造工程設計方法では、リング材の長さＬの変化（伸び）の予測値ΔＬｅは、拡径２終了後の長さの予測値(2841mm)と素材の長さ(2767mm)から、ΔＬｅ＝７４ｍｍである。表２から、上述の鍛造工程設計方法に基づいて鍛造制御を行なった実機での長さ変化（伸び）の実測値ΔＬａｅは、拡径２終了後の長さ(2830mm)と素材の長さ(2767mm)から、ΔＬａｅ＝６３ｍｍであり、本実施例の場合、予測値と実測値とは１％以内の精度で一致していることがわかる。一方、表１からわかるように、比較例の従来の設計手法では長さＬの変化は予測できない。また、表１および表２からわかるように、上述の鍛造工程設計方法に基づいて鍛造制御を行なった本実施例の場合には、拡径後の外径についても、比較例の従来の設計手法に比べて、予測値と実測値とは良好な精度で一致している。 As can be seen from Table 1, in the forging process design method of the example, the predicted value ΔLe of the change (elongation) of the length L of the ring material is the predicted value (2841 mm) of the length after diameter expansion 2 and the material From the length (2767 mm), ΔLe = 74 mm. From Table 2, the measured value ΔLae of the length change (elongation) in the actual machine for which the forging control was performed based on the above-described forging process design method is the length after the end of the diameter expansion 2 (2830 mm) and the length of the material ( 2767 mm), it can be seen that ΔLae = 63 mm, and in the case of the present example, the predicted value and the actual measurement value coincide with each other with an accuracy of 1% or less. On the other hand, as can be seen from Table 1, the change in the length L cannot be predicted by the conventional design method of the comparative example. Further, as can be seen from Tables 1 and 2, in the case of the present example in which forging control was performed based on the above-described forging process design method, the conventional design method of the comparative example was also applied to the outer diameter after the diameter expansion. Compared with, the predicted value and the actually measured value agree with good accuracy.

実施形態の鍛造工程設計方法で、算出式による拡径後の外径と実測した外径とを比較した説明図である。It is explanatory drawing which compared the outer diameter after diameter expansion by a calculation formula, and the measured outer diameter by the forge process design method of embodiment. 実施形態の鍛造工程設計方法で、算出式による拡径後の円周ひずみε_θｃと、理論および実測値から算出した円周ひずみε_θとを比較した説明図である。In forging process design method embodiment, the circumferential strain epsilon _theta c after expanded by calculation formula is an explanatory diagram comparing the circumferential strain epsilon _theta was calculated from the theoretical and measured values. 実施形態の鍛造工程設計方法により予測した拡径後の大型リング材の長さＬ２と実測した長さＬ２ａを比較した説明図である。It is explanatory drawing which compared length L2a of the large ring material after diameter expansion estimated by the forge process design method of embodiment, and measured length L2a. 実施形態の鍛造工程設計方法の流れを示す説明図である。It is explanatory drawing which shows the flow of the forge process design method of embodiment. 実施形態の鍛造制御方法の流れを示す説明図である。It is explanatory drawing which shows the flow of the forge control method of embodiment. リング鍛造を模式的に示す説明図（平面図）である。It is explanatory drawing (plan view) which shows ring forging typically.

Explanation of symbols

１：リング状素材２：芯金３：上金敷 1: Ring-shaped material 2: Core metal 3: Upper anvil

Claims

The inner ring surface of the large ring material is supported by the core metal, and the outer peripheral surface of the large ring material is pressed by the anvil and the large ring material is rotated to move the reduction region, and the required size is obtained over the entire circumference of the large ring material. A process design method in ring forging in which the diameter is expanded to a predetermined shape by repeating the reduction for the number of turns, the outer diameter D1, the thickness T1 and the length L1 at the start of forging of the large ring material, and the target reduction A step of setting an amount S, a reduction amount P per one turn, a step of determining a required number of turns N, and a deformed outer diameter D2 and a length L2 for each turn of the large ring material, A process design method in ring forging, comprising a step of predicting the outer diameter D2 and the length L2 using a prediction formula obtained by correcting this formula using actual machine forging data.

The deformed outer diameter D2 is calculated using the following equations (1) and (2), and the deformed length L2 is calculated using the following equations (3), (4) and (5). The process design method in the ring forging according to claim 1, wherein each is predicted.
D2 = f (D2c) ------------------------------- (1)
D2c = T2 + (T1 / T2) × (D1-T1) --------- (2)
L2 = L1 × exp (−g (ε _θ c) −ε _t ) ------------- (3)
ε _θ c = ln ((D2-T2) / (D1-T1)) --------- (4)
ε _t = ln (T2 / T1) -------------------------------- (5)
Here, D1 and T1 are the outer diameter and thickness at the start of forging (material), T2 is the thickness after deformation (expansion), ε _θ c is the circumferential strain, and ε _t is the wall thickness. The strain in the thickness direction (radial direction) is shown, and f (D2c) and g (ε _θ c) are functions depending on the material of the large ring material.

The inner peripheral surface of the large ring material is supported by the core metal, and the outer peripheral surface of the large ring material is pressed by the anvil and the large ring material is rotated so as to move the reduction region over the entire circumference of the large ring material. A forging control method in ring forging that expands the diameter to a predetermined shape by repeating the reduction for a required number of turns, wherein the large ring material is deformed for each turn using the process design method according to claim 2. The outer diameter D2 and the length L2 are predicted, the outer diameter D2a, the length L2a and the wall thickness T2a of the large ring material for each turn are measured, and the measured outer diameter D2a and length L2a The predicted outer diameters D2 and L2 are respectively compared, and when the differences ΔD and ΔL between the measured outer diameter D2a and length L2a and the predicted outer diameter D2 and length L2 are not within a predetermined range, A forging control method in ring forging, wherein the reduction amount is corrected, and forging is terminated when the cumulative reduction amount reaches a target reduction amount S.