JP2010188369A - Method of manufacturing machine part using cold forging and method of cold forging the same - Google Patents

Method of manufacturing machine part using cold forging and method of cold forging the same Download PDF

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JP2010188369A
JP2010188369A JP2009033996A JP2009033996A JP2010188369A JP 2010188369 A JP2010188369 A JP 2010188369A JP 2009033996 A JP2009033996 A JP 2009033996A JP 2009033996 A JP2009033996 A JP 2009033996A JP 2010188369 A JP2010188369 A JP 2010188369A
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strength
mass
cold forging
shape
machine
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Hideki Kakimoto
英樹 柿本
Taku Osada
卓 長田
Tomokazu Masuda
智一 増田
Akihiro Matsugaseko
亮廣 松ヶ迫
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Kobe Steel Ltd
株式会社神戸製鋼所
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<P>PROBLEM TO BE SOLVED: To manufacture a product capable of fully securing strength of the product, by manufacturing a machine part conventionally manufactured by using hot forging, by using cold forging. <P>SOLUTION: A plastic strain is applied to a portion requiring strength in the machine part, when manufacturing the machine part by using the cold forging. A shape before machining is determined by providing a machining margin to a shape of the machine part. A shape before increasing strength is determined based on an amount of plastic strain applying for increasing strength of the portion requiring strength in the shape before machining. The cool forging is performed while applying strain in a strength increasing step so that the shape before increasing strength may become the shape before machining. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

本発明は、冷間鍛造を用いた機械部品の製造方法に関するものである。   The present invention relates to a method of manufacturing a machine part using cold forging.
従来より、大型ねじや自動車等の車両に用いられているクランクシャフト、コンロッド、トランスミッションギア等の機械部品は、熱間鍛造により製造されている(例えば、特許文献1、特許文献2)。
特許文献1のコンロッドの製造方法では、まず、コンロッドの元となる素材に熱間鍛造を施し、大端部と小端部とこれらを繋ぐ断面略H型のコラム部とを有すると共に外周部にバリを備えたコンロッドを熱間鍛造工程により成形し、次に、熱間鍛造したコンロッドの外周部に生じたバリをバリ抜き工程により除去し、コンロッドの大端部、小端部及びコラム部に冷間コイニング工程により冷間コイニングを施していた。
Conventionally, mechanical parts such as crankshafts, connecting rods, and transmission gears used in vehicles such as large screws and automobiles are manufactured by hot forging (for example, Patent Document 1 and Patent Document 2).
In the manufacturing method of the connecting rod of Patent Document 1, first, hot forging is performed on the material that is the source of the connecting rod, and a large end portion, a small end portion, and a column portion having a substantially H-shaped cross section that connects these are provided on the outer peripheral portion. The connecting rod with burrs is formed by the hot forging process, and then the burrs generated on the outer periphery of the hot forged connecting rod are removed by the burring process, and the connecting rod is applied to the large end, small end and column section. Cold coining was performed by the cold coining process.
また、特許文献2の製造方法では、コンロッドの元となる鋼材を、下限温度が固相線温度×0.94又は1250℃の何れか高い方とした上で、上限温度が液相線×0.98となるように加熱し,前記範囲の温度域で,素材表面の85%以上が金型に接触するように超高温鍛造することによって、コンロッドを製造していた。   Moreover, in the manufacturing method of patent document 2, after making the steel material used as the connecting rod into the higher one of lower limit temperature of solidus temperature x0.94 or 1250 degreeC, upper limit temperature is liquidus line x0. The connecting rod was manufactured by performing ultra-high temperature forging so that 85% or more of the material surface was in contact with the mold in the above temperature range.
特開2006−312978号公報JP 2006-31978 A 特開2005−54228号公報JP 2005-54228 A
このように、大型ねじ等の機械部品においては、熱間鍛造を用いて製造していたが、近年、部品製造工程におけるCO2の排出量削減のため、大型ねじのような熱間鍛造を用いて製造していた機械部品においても、冷間鍛造を用いて製造したいという要求が高まっているのが実情である。
しかしながら、熱間鍛造によって製造していた大型ねじ等の機械部品を、冷間鍛造に切り換えて製造した場合、単に鍛造方法を切り換えるだけでは、次の問題が生じる。熱間鋳造によって製品を作製する際には、熱間鍛造後に焼き入れや焼きもどし等の熱処理が施され、必要される部品強度を得ている。冷間鍛造ままで熱間鍛造と同等の部品強度を得るためには、強度の高い鋼材を使用する必要がある。しかし、そのような鋼材は、冷間鍛造時の変形抵抗が高く、金型の寿命を劣化させやすい。また、加工性も劣るため部品に割れが生じやすくなる。一方、熱間鍛造のような低い変形抵抗、高い加工性を得るためには軟質の鋼材を用いる必要があり、製品に要求される強度が十分に確保することができないのが実情である。
Thus, machine parts such as large screws were manufactured using hot forging, but in recent years, hot forging such as large screws has been used in order to reduce CO 2 emissions in the component manufacturing process. Even in the case of machine parts that have been manufactured in the past, there is a growing demand for manufacturing using cold forging.
However, when a machine part such as a large screw manufactured by hot forging is manufactured by switching to cold forging, the following problem occurs only by switching the forging method. When a product is manufactured by hot casting, heat treatment such as quenching and tempering is performed after hot forging to obtain a required component strength. In order to obtain a component strength equivalent to that of hot forging while still in cold forging, it is necessary to use a steel material having high strength. However, such a steel material has a high deformation resistance during cold forging and tends to deteriorate the life of the mold. Moreover, since workability is also inferior, the parts are likely to crack. On the other hand, in order to obtain low deformation resistance and high workability as in hot forging, it is necessary to use a soft steel material, and the actual situation is that sufficient strength required for products cannot be ensured.
本発明では、冷間鍛造を用いて機械部品を製造するに際し、製品の強度を十分に確保することができる冷間鍛造を用いた機械部品の製造方法及び冷間鍛造方法を提供する。   The present invention provides a method for manufacturing a machine part and a method for cold forging using cold forging that can sufficiently ensure the strength of the product when manufacturing the machine part using cold forging.
前記目的を達成するために、本発明では、次の手段を講じた。
即ち、本発明の手段は、冷間鍛造を用いて機械部品を製造するに際して、前記機械部品において強度が必要な部分に対し、塑性歪みを付与することによる強度増加工程を有する点にある。 前記機械部品の形状に機械加工代を付与することで機械加工前形状を決定し、前記機械加工前形状に、前記強度が必要な部分に対して強度増加のために付与する前記塑性歪み量に基づいて強度増加前形状を決定した上で、前記強度増加前形状が、前記機械加工前形状となるように前記強度増加工程にて歪みを入れながら冷間鍛造を行うことが好ましい。
In order to achieve the above object, the present invention takes the following measures.
That is, the means of the present invention is that when a machine part is manufactured using cold forging, it has a strength increasing step by applying plastic strain to a portion of the machine part that requires strength. A shape before machining is determined by giving machining allowance to the shape of the machine part, and the amount of plastic strain to be given to the shape before machining to increase the strength to the portion requiring the strength is determined. It is preferable to perform cold forging while adding strain in the strength increasing step so that the shape before increasing strength is determined based on the shape before increasing strength so that the shape before increasing strength becomes the shape before machining.
前記機械部品は、C:0.005〜0.045質量%、Si:0.005〜0.4質量%、Mn:0.3〜1質量%、P:0.05質量%以下(0%を含まない)、S:0.005〜0.05質量%、Al:0.005〜0.06質量%、N:0.008〜0.025質量%、及び式(1)を満たし、残部は鉄および不可避的不純物からなり、且つ固溶状態としてのN:0.007質量%以上を満たす材料から製造されることが好ましい。
前記塑性歪み量は、8以下(0を除く)であることが好ましい。さらには、塑性歪み量は、1以上5以下であることが好ましい。
The mechanical parts are: C: 0.005 to 0.045 mass%, Si: 0.005 to 0.4 mass%, Mn: 0.3 to 1 mass%, P: 0.05 mass% or less (0% S: 0.005 to 0.05 mass%, Al: 0.005 to 0.06 mass%, N: 0.008 to 0.025 mass%, and the formula (1) is satisfied, and the balance Is preferably made of a material consisting of iron and inevitable impurities and satisfying N: 0.007% by mass or more as a solid solution state.
The plastic strain amount is preferably 8 or less (excluding 0). Furthermore, the amount of plastic strain is preferably 1 or more and 5 or less.
前記塑性歪み量を、降伏応力(YP)、最大応力(TS)、強度(h)、疲労強度(i)のいずれかをもとにしたモデル式又は予め取得したデータベースから求めることが好ましい。
上述した冷間鍛造を用いた機械部品の製造方法における冷間鍛造においては、押し出し型鍛造又は圧縮部分圧下を行うことが好ましい。
The amount of plastic strain is preferably obtained from a model formula based on any one of yield stress (YP), maximum stress (TS), strength (h), and fatigue strength (i) or from a previously acquired database.
In the cold forging in the method of manufacturing a machine part using the cold forging described above, it is preferable to perform extrusion die forging or compression partial reduction.
本発明によれば、冷間鍛造を用いて機械部品を製造するに際し、製品の強度を十分に確保することができる製品を製造することができる。   ADVANTAGE OF THE INVENTION According to this invention, when manufacturing a machine part using cold forging, the product which can fully ensure the intensity | strength of a product can be manufactured.
冷間鍛造を用いた機械部品の製造方法を示したフローチャートである。It is the flowchart which showed the manufacturing method of the machine components using cold forging. 大型ねじ(機械部品)の製造方法を図示したものである。The manufacturing method of a large sized screw (mechanical part) is illustrated.
本発明の冷間鍛造を用いた機械部品の製造方法について説明する。
本発明の機械部品の製造方法では、従来より熱間鍛造により製造されていた大型ねじ、クランクシャフト、コンロッド、トランスミッションギア等の機械部品を、冷間鍛造を用いて製造するものである。以下、大型ねじを代表的に例示して、その製造方法を説明する。
図1は、機械部品の製造方法の手順を示したものであり、図2は、機械部品の製造方法の手順を図示したものである。なお、この製造方法においては、設計段階の内容も含んだものとなっており、後述する製品形状決定工程〜材料形状決定工程までが設計段階(加工前段階)であり、以降が具体的な加工段階となる。
The manufacturing method of the machine parts using the cold forging of this invention is demonstrated.
In the method of manufacturing a machine part according to the present invention, machine parts such as large screws, crankshafts, connecting rods, transmission gears and the like that have been conventionally manufactured by hot forging are manufactured by using cold forging. Hereinafter, the manufacturing method will be described using a large screw as a representative example.
FIG. 1 shows a procedure of a method for manufacturing a machine part, and FIG. 2 shows a procedure of a method for manufacturing a machine part. In this manufacturing method, the contents of the design stage are also included, and the product shape determination process to the material shape determination process, which will be described later, are the design stage (pre-processing stage), and the subsequent processing is concrete. It becomes a stage.
図1及び図2に示すように、まず、大型ねじ1を製造するにあたっては、大型ねじ1の製品形状Aを決定する(S1:製品形状決定工程)。即ち、冷間鍛造後(強度増加後)に機械加工が施されるが、この機械加工終了後の大型ねじ1の形状、即ち、製品にしたときの大型ねじ1の製品形状Aを製作図面中から決定する。この形状はユーザからの要求により決まることが多い。
次に、製品形状工程S1にて決定した製品形状Aに機械加工代を付与(加算)することで、機械加工前形状Bを決定する(S2:機械加工前形状工程)。
As shown in FIGS. 1 and 2, first, when manufacturing the large screw 1, the product shape A of the large screw 1 is determined (S1: product shape determining step). That is, machining is performed after cold forging (after strength increase), but the shape of the large screw 1 after the completion of the machining, that is, the product shape A of the large screw 1 when made into a product is shown in the production drawing. Determine from. This shape is often determined by user demand.
Next, a shape B before machining is determined by adding (adding) a machining allowance to the product shape A determined in the product shape step S1 (S2: shape process before machining).
例えば、機械加工前形状工程S2では、大型ねじ1における製品輪郭線(製造後の輪郭線)L1に、各箇所の機械加工代(例えば、数mm)の寸法を加算して、冷間鍛造後輪郭線(強度増加後輪郭線)L2を求めることによって冷間鍛造によって形成できる機械加工前形状Bを決定する。
そして、機械加工前形状工程S2にて決定した機械加工前形状Bに、強度が必要な部分に対して強度増加のために付与する塑性歪み量εに基づき、強度増加前形状(歪み前形状)Cを決定する(S3:強度増加前形状決定工程)。
For example, in the pre-machining shape step S2, the dimension of machining allowance (for example, several mm) at each location is added to the product contour line (manufactured contour line) L1 of the large screw 1 and after cold forging. A shape B before machining that can be formed by cold forging is determined by obtaining a contour line (contour line after increasing strength) L2.
Then, based on the amount of plastic strain ε to be imparted to the pre-machining shape B determined in the pre-machining shape step S2 to increase the strength for the portion requiring strength, the shape before the strength increase (pre-strain shape) C is determined (S3: shape determination step before increasing strength).
例えば、大型ねじ1において軸部2に強度が必要な場合、当該軸部2の冷間鍛造後(強度増加後)の鍛造後輪郭線L3に対して、機械加工代とは別に塑性歪みを与えうるだけの寸法ε(歪み量)を加算し、歪み付与前輪郭線L4を求めることによって、強度増加前形状(歪み前形状)Cを決定する。
この強度増加前形状決定工程S3では、後述する冷間鍛造の際(強度増加工程)に、強度が必要な部分に対して意図的に塑性歪みを与え、その部分(強度が必要な部分)のTS(引っ張り強度)やYSを増加させる、即ち、必要な部分での強度をアップさせることを意図して、塑性歪みの量を計算している。
For example, when the shaft portion 2 of the large screw 1 requires strength, a plastic strain is applied to the post-forging contour L3 after cold forging (after strength increase) of the shaft portion 2 separately from the machining allowance. The shape before strength increase (shape before distortion) C is determined by adding as much as possible dimension ε (amount of distortion) to obtain the contour line L4 before distortion.
In this pre-strength shape determination step S3, during cold forging described later (strength increasing step), plastic strain is intentionally applied to a portion requiring strength, and that portion (portion requiring strength) The amount of plastic strain is calculated in order to increase TS (tensile strength) and YS, that is, to increase the strength at a necessary portion.
従来の技術では、大型ねじ1は熱間鍛造とその後の熱処理によって製造することで強度を確保していたが、熱間鍛造していた大型ねじ1を単に冷間鍛造に変更するだけでは、前述した理由の通り予め必要な強度が得られない箇所が出てくる。
そのため、本発明では、従来の方法による冷間鍛造のみでは強度が得られない部分に対して、製造過程で意図的に塑性歪みを与えるようにすることで、部品強度を増加させている。言い換えれば、従来、熱間鍛造していた大型ねじ1は、残留歪みは有していないが、本発明では、意図的に、強度を向上させる部分に残留歪みを与えることで、冷間鍛造を行っても強度が確保できるようにしている。ここで、付与する塑性歪み量は、8以下(0を除く)にしている。塑性歪み量が8よりも大きい場合、強度が上がりすぎて冷間鍛造では部品加工ができなくなることから、塑性歪み量は8以下とする必要がある。また、付与する塑性歪み量は、1以上5以下であることが好ましい。付与する塑性歪み量が1未満であると十分な部品強度が得られず、5よりも大きいと鋼材の加工能が劣化しはじめるため、部品に割れが生じやすくなる。
In the conventional technique, the large screw 1 is manufactured by hot forging and subsequent heat treatment to ensure the strength. However, the large screw 1 that has been hot forged is simply changed to cold forging. As described above, there are places where the required strength cannot be obtained in advance.
Therefore, in the present invention, the strength of the parts is increased by intentionally applying plastic strain to the portion where the strength cannot be obtained only by cold forging by the conventional method. In other words, the conventional large-sized screw 1 that has been hot forged does not have residual strain. However, in the present invention, cold forging is intentionally applied by applying residual strain to a portion that improves strength. The strength can be secured even if it goes. Here, the amount of plastic strain to be applied is set to 8 or less (excluding 0). If the amount of plastic strain is greater than 8, the strength is so high that parts cannot be processed by cold forging, so the amount of plastic strain must be 8 or less. The amount of plastic strain to be applied is preferably 1 or more and 5 or less. If the amount of plastic strain to be applied is less than 1, sufficient component strength cannot be obtained, and if it is greater than 5, the workability of the steel material starts to deteriorate, so that the component is likely to crack.
なお、強度増加前形状決定工程S3において、塑性歪みを与える量はTS(引っ張り強度)を付与する度合い(量)に応じて設定すればよい。例えば、式(2)〜式(5)に示したモデル式又は予め取得したデータベースを用いて塑性歪み量εを決定してもよい。即ち、塑性歪み量を、降伏応力(YP)、最大応力(TS)、強度(h)、疲労強度(i)のいずれかをもとにしたモデル式又は予め取得したデータベースから求めてもよい。
ε=f-1(YP) ・・・(2)
ε=g-1(TS) ・・・(3)
ε=h-1(強度) ・・・(4)
ε=i-1(疲労強度) ・・・(5)
ただし、f:応力−歪み曲線(塑性歪み曲線)の関数、g:最大応力−歪み曲線(塑性歪み曲線)の関数、h:強度−歪み曲線(塑性歪み曲線)の関数、i:疲労強度−歪み曲線(塑性歪み曲線)の関数である。
In the shape determination step S3 before increasing strength, the amount of plastic strain may be set according to the degree (amount) of applying TS (tensile strength). For example, the plastic strain amount ε may be determined using the model expressions shown in Expressions (2) to (5) or a database acquired in advance. That is, the plastic strain amount may be obtained from a model formula based on any one of yield stress (YP), maximum stress (TS), strength (h), and fatigue strength (i), or from a database acquired in advance.
ε = f −1 (YP) (2)
ε = g −1 (TS) (3)
ε = h −1 (strength) (4)
ε = i −1 (fatigue strength) (5)
Where f: function of stress-strain curve (plastic strain curve), g: function of maximum stress-strain curve (plastic strain curve), h: function of strength-strain curve (plastic strain curve), i: fatigue strength- It is a function of a strain curve (plastic strain curve).
また、塑性歪みは、強度が必要な部分に対して与えればよく、上述したように、大型ねじ1において説明したように軸部分に限定されなず、適宜選定すればよい。
強度増加前形状(歪み前形状)Cを決定した後は、この強度増加前形状C(幅や高さ、体積等)から、大型ねじ1の元になる材料の大きさを決定する(S4:材料形状決定工程)。例えば、大型ねじ1を製造する際には、丸棒3を用いることから強度増加前形状C(幅や高さ、体積等)から丸棒3の直径、長さ等を決定する。
次に、材料の初期形状が決まると、熱間鍛造、又は、切削などの機械加工により、材料が強度増加前形状(歪み前形状)Cとなるように予備の加工を行う(S5:予備加工工程)。
Further, the plastic strain may be applied to a portion requiring strength, and as described above, the plastic strain is not limited to the shaft portion as described in the large screw 1 and may be appropriately selected.
After determining the pre-intensity shape (pre-strain shape) C, the material size of the large screw 1 is determined from the pre-intensity shape C (width, height, volume, etc.) (S4: Material shape determination step). For example, when the large screw 1 is manufactured, since the round bar 3 is used, the diameter, length, and the like of the round bar 3 are determined from the shape C (width, height, volume, etc.) before increasing the strength.
Next, when the initial shape of the material is determined, preliminary processing is performed so that the material has a shape before increasing strength (shape before strain) C by hot forging or machining (S5: preliminary processing). Process).
そして、予備加工工程S5にて材料を強度増加前形状(歪み前形状)Cの形状にした後は、機械加工前形状Bとなるように強度が必要な部分に塑性歪みを付与しながら冷間鍛造を行う(S6:強度増加工程)。
例えば、設計段階にて説明したように、この大型ねじ1においては軸部2の強度を増加させることから、強度増加工程S6では、軸部2に歪みを入れつつ冷間鍛造を行っている。詳しくは、この強度増加工程S6では、軸部2に対応する歪み付与前輪郭線L4が鍛造後輪郭線(強度増加後輪郭線)L2に一致するように圧縮等(部分圧下)を行い、塑性歪みを入れ、これにより、軸部2のTS(引っ張り強度)を増加させている。
And after making the material into the shape of the pre-intensity shape (pre-strain shape) C in the pre-processing step S5, the material is cold while giving plastic strain to the portion requiring strength so as to become the pre-machining shape B. Forging is performed (S6: strength increasing step).
For example, as described in the design stage, since the strength of the shaft portion 2 is increased in the large screw 1, cold forging is performed while straining the shaft portion 2 in the strength increasing step S6. Specifically, in this strength increasing step S6, compression or the like (partial reduction) is performed so that the pre-strained contour line L4 corresponding to the shaft portion 2 matches the post-forging contour line (contour line after increasing strength) L2. Strain is added, thereby increasing the TS (tensile strength) of the shaft 2.
そして、冷間鍛造後(強度増加後)は、機械加工前形状Bの材料に対して機械加工することによって、製品形状Aにする(S7:機械加工工程)。
なお、冷間鍛造を行う方法については限定されず、軸方向への圧縮(圧縮部分圧下)を行ってもよいし、押し出し成形(押し出し型鍛造)を行ってもよいし、型鍛造を行っても良い。また、冷間鍛造(冷間加工)時の雰囲気の温度は200℃未満であり、材料の加工前温度は、100℃未満であることが好ましい。
また、上記の説明では、予備加工工程S5を経てから強度増加工程(冷間鍛造工程)S6を行っているが、図2の矢印Sに示すように、この予備加工工程S5を行わずに、材料形状決定工程S4で決定した丸棒2に対して、直接、強度増加工程(冷間鍛造工程)S6を行ってもよい。つまり、この場合は、機械加工代が付与された形状となるように冷間鍛造を行いつつ、強度の必要な部分(例えば、軸部)に塑性歪み量εに応じた歪み入れを行うことになる。
And after cold forging (after strength increase), it is set as product shape A by machining with respect to the material of the shape B before machining (S7: machining process).
The method for performing cold forging is not limited, and axial compression (compressed partial compression) may be performed, extrusion molding (extrusion die forging) may be performed, or die forging may be performed. Also good. Moreover, it is preferable that the temperature of the atmosphere at the time of cold forging (cold processing) is less than 200 ° C., and the pre-processing temperature of the material is less than 100 ° C.
In the above description, the strength increasing step (cold forging step) S6 is performed after the preliminary processing step S5. However, as shown by the arrow S in FIG. The strength increasing step (cold forging step) S6 may be directly performed on the round bar 2 determined in the material shape determining step S4. In other words, in this case, while performing cold forging so as to obtain a shape with machining allowance, straining according to the amount of plastic strain ε is performed on a portion requiring strength (for example, a shaft portion). Become.
次に、機械部品の材料について説明する。
上述した機械部品の材料は、C:0.005〜0.045質量%、Si:0.005〜0.4質量%、Mn:0.3〜1質量%、P:0.05質量%以下(0%を含まない)、S:0.005〜0.05質量%、Al:0.005〜0.06質量%、N:0.008〜0.025質量%、及び式(1)を満たし、残部は鉄および不可避的不純物からなり、且つ固溶状態としてのN:0.007質量%以上を満たすものである。
この材料は、塑性歪みを付与するとTSやYSが向上する特性があり、特に、与える塑性歪みに比例してTSが向上するものである。なお、材料について説明するが、塑性歪みを付与した際にTSやYSが向上する材料であれば何でもよく、この実施形態に説明する材料に限定されない。
Next, materials for machine parts will be described.
The material of the mechanical part mentioned above is C: 0.005-0.045 mass%, Si: 0.005-0.4 mass%, Mn: 0.3-1 mass%, P: 0.05 mass% or less (Excluding 0%), S: 0.005 to 0.05 mass%, Al: 0.005 to 0.06 mass%, N: 0.008 to 0.025 mass%, and the formula (1) The balance is made of iron and inevitable impurities, and satisfies N: 0.007% by mass or more as a solid solution state.
This material has a characteristic that TS and YS are improved when plastic strain is applied, and TS is improved in proportion to the plastic strain applied. The material will be described, but any material can be used as long as TS and YS are improved when plastic strain is applied, and the material is not limited to the material described in this embodiment.
[C:0.005〜0.045質量%]
Cは、鋼材の組織の形成に大きな影響を及ぼす元素であり、組織をフェライト単相組織とするために、極力低減する必要があり、過剰に含有すると、鋼材の組織中にパーライトが生成し、パーライトの加工硬化によって変形抵抗が過大となる恐れがある。こうしたことから、C含有量は0.045質量%とする必要があり、好ましくは、0.043質量%以下、より好ましくは0.040質量%以下である。しかしながら、C含有量が極端に少なくなると、鋼材の溶製中の脱酸が困難になるため、下限は0.005質量%とすることが好ましく、より好ましくは0.01質量%以上、更に好ましくは0.015質量%以上である。
[C: 0.005 to 0.045% by mass]
C is an element that greatly affects the formation of the structure of the steel material, and in order to make the structure a ferrite single-phase structure, it is necessary to reduce as much as possible, and if excessively contained, pearlite is generated in the structure of the steel material, Deformation resistance may be excessive due to work hardening of pearlite. For these reasons, the C content needs to be 0.045% by mass, preferably 0.043% by mass or less, and more preferably 0.040% by mass or less. However, if the C content is extremely low, deoxidation during melting of the steel material becomes difficult, so the lower limit is preferably 0.005% by mass, more preferably 0.01% by mass or more, and still more preferably Is 0.015 mass% or more.
[Si:0.005〜0.4質量%]
Siは、溶製中の脱酸元素として有効である。Si含有量が0.005質量%未満であると、脱酸が不十分になって溶製中にブローホールを発生することになる。しかしながら、Si含有量が過剰になって0.4質量%を超えると、Siの固溶強化による変形抵抗の増大を招くと共に、割れが顕著になる場合がある。尚、Si含有量は好ましくは0.006質量%以上(より好ましくは0.007質量%以上)であり、好ましくは0.35質量%以下(より好ましくは0.32質量%以下)である。
[Si: 0.005 to 0.4 mass%]
Si is effective as a deoxidizing element during melting. When the Si content is less than 0.005% by mass, deoxidation becomes insufficient and blow holes are generated during melting. However, if the Si content becomes excessive and exceeds 0.4 mass%, the deformation resistance is increased due to the solid solution strengthening of Si, and cracks may become remarkable. The Si content is preferably 0.006% by mass or more (more preferably 0.007% by mass or more), preferably 0.35% by mass or less (more preferably 0.32% by mass or less).
[Mn:0.3〜1質量%]
鋼材中のN含有量を高めた場合、加工中の発熱による動的歪み時効によって割れが発生しやすくなるが、Mnはそのときの加工性を向上させ、割れを抑制する効果がある。この様な効果を有効に発揮させるには、0.3質量%以上含有させることが必要であり、好ましくは0.35質量%以上、より好ましくは0.40質量%以上である。一方、Mnが過剰に含まれると変形抵抗が過大となるだけでなく、偏析による組織の不均一性が生じるので、1質量%以下とする必要があり、好ましくは0.95質量%以下、より好ましくは0.90質量%以下である。
[Mn: 0.3 to 1% by mass]
When the N content in the steel material is increased, cracks are likely to occur due to dynamic strain aging due to heat generation during processing, but Mn has the effect of improving the workability at that time and suppressing cracks. In order to exhibit such an effect effectively, it is necessary to contain 0.3 mass% or more, preferably 0.35 mass% or more, more preferably 0.40 mass% or more. On the other hand, if Mn is contained excessively, not only the deformation resistance becomes excessive, but also the structure non-uniformity due to segregation occurs, so it is necessary to make it 1% by mass or less, preferably 0.95% by mass or less, more Preferably it is 0.90 mass% or less.
[P:0.05質量%以下(0%を含まない)]
リン(P)は、不可避的不純物であるが、これがフェライトに含有すると、フェライト粒界に偏析して冷間加工性を劣化させる元素である。また、フェライトを固溶強化させて変形抵抗の増大をもたらす元素でもある。よって、冷間加工性向上の観点から、P含有量は0.05質量%以下とする。好ましくは0.03質量%以下であるが、P含有量を0%にすることは、工業上困難である。
[S:0.005〜0.05質量%]
硫黄(S)も、Pと同様に不可避的不純物であり、FeSとして結晶粒界に膜状に析出し、加工性を劣化させる元素である。また、熱間脆性を引き起こす作用がある。そこで変形能を向上させる観点から、S含有量を、0.05質量%以下(好ましくは0.03質量%以下)とする。但しS含有量を0%にすることは、工業上困難である。尚、Sは被削性を向上させる効果を有するため、被削性向上の観点からは、0.005質量%以上含有させることが好ましく、より好ましくは0.008質量%以上含有させることが推奨される。
[Al:0.005〜0.06質量%]
Alは、強い脱酸効果を有して、鋼材の内部品質を向上させることができる。また、鋼中のNと結合して、AlNを形成し、フェライト結晶粒を整粒化する効果も有する。これらの効果を有効に発揮させるためには、0.005質量%以上のAlが必要である。また、0.01質量%以上が好ましく、0.015質量%以上が更に好ましい。Alの含有量が0.005質量%未満であると、溶製時にガス欠陥が発生しやすく、冷間鍛造時に割れが発生しやすい。一方、0.06質量%を超えると、固溶N量を低下させ、所定の部品強度が得られなくなる。Alは、好ましくは、0.05質量%以下、さらに、好ましくは0.04質量%以下である。
[P: 0.05% by mass or less (excluding 0%)]
Phosphorus (P) is an unavoidable impurity, but when it is contained in ferrite, it is an element that segregates at the ferrite grain boundaries and degrades cold workability. It is also an element that causes solid solution strengthening of ferrite to increase deformation resistance. Therefore, from the viewpoint of improving cold workability, the P content is 0.05% by mass or less. Although it is preferably 0.03% by mass or less, it is industrially difficult to make the P content 0%.
[S: 0.005 to 0.05 mass%]
Sulfur (S) is an unavoidable impurity like P, and is an element that precipitates in the form of a film at the grain boundary as FeS and degrades workability. It also has the effect of causing hot brittleness. Therefore, from the viewpoint of improving the deformability, the S content is set to 0.05% by mass or less (preferably 0.03% by mass or less). However, it is industrially difficult to reduce the S content to 0%. In addition, since S has an effect of improving machinability, it is preferable to contain 0.005% by mass or more, more preferably 0.008% by mass or more from the viewpoint of improving machinability. Is done.
[Al: 0.005 to 0.06% by mass]
Al has a strong deoxidation effect and can improve the internal quality of the steel material. Moreover, it combines with N in steel to form AlN, and has the effect of regulating the ferrite crystal grains. In order to exhibit these effects effectively, 0.005 mass% or more of Al is required. Moreover, 0.01 mass% or more is preferable and 0.015 mass% or more is still more preferable. If the Al content is less than 0.005% by mass, gas defects are likely to occur during melting, and cracks are likely to occur during cold forging. On the other hand, if it exceeds 0.06% by mass, the amount of solute N is reduced, and a predetermined component strength cannot be obtained. Al is preferably 0.05% by mass or less, more preferably 0.04% by mass or less.
[N:0.008〜0.025質量%]
窒素(N)は、加工後の静的歪み時効によって所定の強度を得るために重要な元素である。こうした効果を発揮させるためには、N含有量を0.008質量%以上とする必要がある。しかしながら、N含有量が過剰になって0.025質量%を超えると、静的歪み時効よりも加工中の動的歪み時効の影響が顕著になり、変形抵抗が増大することになる。尚、N含有量の好ましい下限は0.0085質量%(より好ましくは0.009質量%以上)であり、好ましい上限は0.023質量%(より好ましくは0.02質量%以下)である。
[N: 0.008 to 0.025 mass%]
Nitrogen (N) is an important element for obtaining a predetermined strength by static strain aging after processing. In order to exert such effects, the N content needs to be 0.008% by mass or more. However, if the N content becomes excessive and exceeds 0.025 mass%, the influence of dynamic strain aging during processing becomes more significant than static strain aging, and the deformation resistance increases. In addition, the minimum with preferable N content is 0.0085 mass% (more preferably 0.009 mass% or more), and a preferable upper limit is 0.023 mass% (more preferably 0.02 mass% or less).
機械部品に用いる材料では、固溶状態のN(固溶N)を所定量とすることによって、変形抵抗をあまり高くせずに、静的歪み時効を促進させることも特徴としている。冷間加工後に所定の強度を確保するためには、固溶Nの量を0.007質量%以上とする必要がある。しかしながら、固溶Nの量が過剰になると、冷問加工性が劣化するので、好ましくは00.025質量%以下とするのが良い。
尚、本発明における固溶Nの含有量は、JIS G 1228に準拠して、鋼材中の全N量から全N化合物中のN量を差し引いて求められる値である。この固溶Nの含有量の実用的な測定法を以下に例示する。
(a)不活性ガス融解法一熱伝導度法(全N量測定)
供試材から切り出したサンプルをルツボに入れ、不活性ガス気流中で融解してNを抽出し、抽出物を熱伝導度セルに搬送して熱伝導度の変化を測定して全N量を求める。
(b)アンモニア蒸留分離インドフェノール青吸光光度法(全N化合物量の測定)
供試材から切り出したサンプルを、10%AA系電解液に溶解し、定電流電解を行って、鋼中の全N化合物量を測定する。用いる10%AA系電解液は、10%アセトン、10%塩化テトラメチルアンモニウム、残部メタノールからなる非水溶媒系の電解液であり、鋼表面に不働態皮膜を生成させない溶液である。
The material used for the machine part is characterized by promoting static strain aging without increasing the deformation resistance by setting a predetermined amount of solid solution N (solid solution N). In order to ensure a predetermined strength after cold working, the amount of solute N needs to be 0.007% by mass or more. However, if the amount of solute N becomes excessive, the cold workability deteriorates, so that the amount is preferably 0.025% by mass or less.
In addition, content of the solid solution N in this invention is a value calculated | required by subtracting N amount in all N compounds from total N amount in steel materials based on JISG1228. A practical method for measuring the content of this solid solution N is exemplified below.
(A) Inert gas melting method, thermal conductivity method (total N content measurement)
The sample cut out from the test material is put in a crucible, melted in an inert gas stream to extract N, the extract is transferred to a thermal conductivity cell, and the change in thermal conductivity is measured to determine the total N amount. Ask.
(B) Ammonia distillation separation indophenol blue spectrophotometry (measurement of total N compound amount)
A sample cut out from the test material is dissolved in a 10% AA-based electrolytic solution, subjected to constant current electrolysis, and the total amount of N compounds in the steel is measured. The 10% AA electrolyte used is a non-aqueous solvent electrolyte consisting of 10% acetone, 10% tetramethylammonium chloride, and the remainder methanol, and does not generate a passive film on the steel surface.
供試材のサンプル約0.5gを、この10%AA系電解液に溶解させ、生成する不溶解残渣(N化合物)を穴サイズが0.1μmのポリカーボネート製のフィルタでろ過する。得られた不溶解残渣を、硫酸、硫酸カリウムおよび純銅製チップ中で加熱して分解し、分解物をろ液に合わせる。この溶液を、水酸化ナトリウムでアルカリ性にした後、水蒸気蒸留を行い、留出したアンモニアを希硫酸に吸収させる。更に、フェノール、次亜塩素酸ナトリウムおよびペンタシアノニトロシル鉄(III)酸ナトリウムを加えて青色錯体を生成させ、吸光光度計を用いて吸光度を測定して全N化合物量を求める。   About 0.5 g of the sample material is dissolved in the 10% AA electrolyte solution, and the resulting insoluble residue (N compound) is filtered through a polycarbonate filter having a hole size of 0.1 μm. The obtained insoluble residue is decomposed by heating in a chip made of sulfuric acid, potassium sulfate and pure copper, and the decomposition product is combined with the filtrate. After making this solution alkaline with sodium hydroxide, steam distillation is performed, and the distilled ammonia is absorbed in dilute sulfuric acid. Further, phenol, sodium hypochlorite and sodium pentacyanonitrosyl iron (III) are added to form a blue complex, and the absorbance is measured using an absorptiometer to determine the total N compound amount.
(a)の方法によって求められた全N量から、(b)の方法によって求められた全N化合物量を差し引いて固溶N量を求めることができる。
機械部品に用いる材料において、固溶Cは変形抵抗を大きく増加させ、静的歪み時効にあまり寄与せず、一方、固溶Nは変形抵抗をあまり上げず、静的歪み時効を促進させることができるため加工後(歪み付与後)の強度を増加させることができる作用を有する。
そのため、この材料においては、加工中の変形抵抗をあまり上げず、加工後の硬さを増加させるために、Cの含有量[C]とNの含有量[N]とは、式(1)の関係を満足する必要がある。式(1)の右辺の値(=10[C]+[N])が、0.3(質量%)を超えると、CおよびNの含有量が過剰となって、変形抵抗が過大となる。
The total amount of N compounds determined by the method (b) can be subtracted from the total N amount determined by the method (a) to determine the solid solution N amount.
In materials used for machine parts, solute C greatly increases deformation resistance and does not contribute much to static strain aging, while solute N does not increase deformation resistance and promotes static strain aging. Therefore, it has the effect of increasing the strength after processing (after applying strain).
Therefore, in this material, in order to increase the hardness after processing without increasing the deformation resistance during processing, the C content [C] and the N content [N] It is necessary to satisfy the relationship. When the value on the right side of Equation (1) (= 10 [C] + [N]) exceeds 0.3 (mass%), the C and N contents become excessive and the deformation resistance becomes excessive. .
尚、(10[C]+[N])の値は、0.29以下であることが好ましく、より好ましくは0.28以下とするのが良い。
0.3≧(10[C]十[N]) ・・・(1)
但し、[C]および[N]は、夫々CおよびNの含有量(質量%)を示す。
材料の成分は上記の通りであり、残部は鉄および不可避的不純物である。
以上の材料を用いて、大型ねじ1を本発明に示した鍛造方法により製造することにより、従来、熱間鍛造を用いてしか大型ねじ1を製造できなかったものが、冷間鍛造を用いて製造することができるようになった。なお、本発明の製造方法は、大型ねじ1のみならず、これまで熱間鍛造によって加工されていたクランクシャフト、コンロッド、トランスミッションギヤ等の自動車用部品、その他の機械部品)にも適用することができる。
Note that the value of (10 [C] + [N]) is preferably 0.29 or less, and more preferably 0.28 or less.
0.3 ≧ (10 [C] + [N]) (1)
However, [C] and [N] indicate the contents (% by mass) of C and N, respectively.
The components of the material are as described above, with the balance being iron and inevitable impurities.
By manufacturing the large screw 1 by the forging method shown in the present invention using the above-mentioned materials, conventionally, the large screw 1 can be manufactured only by using hot forging. It can be manufactured. Note that the manufacturing method of the present invention can be applied not only to the large screw 1 but also to automotive parts such as crankshafts, connecting rods, transmission gears, and other machine parts that have been processed by hot forging so far. it can.
1 大型ねじ
2 軸部
3 丸棒
1 Large screw 2 Shaft 3 Round bar

Claims (7)

  1. 冷間鍛造を用いて機械部品を製造するに際して、前記機械部品において強度が必要な部分に対し、塑性歪みを付与することによる強度増加工程を有することを特徴とする冷間鍛造を用いた機械部品の製造方法。   When manufacturing machine parts using cold forging, the machine parts using cold forging characterized by having a strength increasing step by applying plastic strain to the parts requiring strength in the machine parts Manufacturing method.
  2. 前記機械部品の形状に機械加工代を付与することで機械加工前形状を決定し、前記機械加工前形状に、前記強度が必要な部分に対して強度増加のために付与する前記塑性歪み量に基づいて強度増加前形状を決定した上で、
    前記強度増加前形状が、前記機械加工前形状となるように前記強度増加工程にて歪みを入れながら冷間鍛造を行うことを特徴とする請求項1に記載の冷間鍛造を用いた機械部品の製造方法。
    A shape before machining is determined by giving machining allowance to the shape of the machine part, and the amount of plastic strain to be given to the shape before machining to increase the strength to the portion requiring the strength is determined. After determining the shape before strength increase based on
    The machine part using cold forging according to claim 1, wherein cold forging is performed while straining in the strength increasing step so that the shape before increasing the strength becomes the shape before machining. Manufacturing method.
  3. 前記機械部品は、C:0.005〜0.045質量%、Si:0.005〜0.4質量%、Mn:0.3〜1質量%、P:0.05質量%以下(0%を含まない)、S:0.005〜0.05質量%、Al:0.005〜0.06質量%、N:0.008〜0.025質量%、及び式(1)を満たし、残部は鉄および不可避的不純物からなり、且つ固溶状態としてのN:0.007質量%以上を満たす材料から製造されることを特徴とする請求項1又は2に記載の冷間鍛造を用いた機械部品の製造方法。   The mechanical parts are: C: 0.005 to 0.045% by mass, Si: 0.005 to 0.4% by mass, Mn: 0.3 to 1% by mass, P: 0.05% by mass or less (0% S: 0.005 to 0.05 mass%, Al: 0.005 to 0.06 mass%, N: 0.008 to 0.025 mass%, and the formula (1) is satisfied, and the balance The machine using cold forging according to claim 1 or 2, wherein the machine is made of a material made of iron and inevitable impurities and satisfying N: 0.007% by mass or more as a solid solution state. Manufacturing method of parts.
  4. 前記塑性歪み量は、8以下(0を除く)であることを特徴とする請求項1〜3のいずれかに記載の冷間鍛造を用いた機械部品の製造方法。   The said plastic strain amount is 8 or less (except 0), The manufacturing method of the machine parts using the cold forging in any one of Claims 1-3 characterized by the above-mentioned.
  5. 前記塑性歪み量は、1以上5以下であることを特徴とする請求項1〜3のいずれかに記載の冷間鍛造を用いた機械部品の製造方法。   The said plastic strain amount is 1 or more and 5 or less, The manufacturing method of the machine components using the cold forging in any one of Claims 1-3 characterized by the above-mentioned.
  6. 前記塑性歪み量を、降伏応力(YP)、最大応力(TS)、強度(h)、疲労強度(i)のいずれかをもとにしたモデル式又は予め取得したデータベースから求めることを特徴とする請求項1〜5のいずれかに記載の冷間鍛造を用いた機械部品の製造方法。   The amount of plastic strain is obtained from a model formula based on any one of yield stress (YP), maximum stress (TS), strength (h), and fatigue strength (i), or from a previously acquired database. The manufacturing method of the machine component using the cold forging in any one of Claims 1-5.
  7. 請求項1〜請求項6の冷間鍛造を用いた機械部品の製造方法における冷間鍛造において、押し出し型鍛造又は圧縮部分圧下を行うことを特徴とする冷間鍛造方法。   A cold forging method in which extrusion die forging or compression partial reduction is performed in the cold forging in the method of manufacturing a machine part using cold forging according to claim 1.
JP2009033996A 2009-02-17 2009-02-17 Method of manufacturing machine part using cold forging and method of cold forging the same Pending JP2010188369A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0655237A (en) * 1992-06-08 1994-03-01 Rhythm Corp Manufacture of steering tie rod
JPH07305139A (en) * 1994-05-09 1995-11-21 Nippon Steel Corp Non-heat treated machine parts and production thereof
JP2006218502A (en) * 2005-02-09 2006-08-24 Kobe Steel Ltd Method, apparatus and program for deciding shape of die
JP2006231377A (en) * 2005-02-25 2006-09-07 Sanyo Special Steel Co Ltd Method for predicting shape after upsetting with hot-forging
JP2008163410A (en) * 2006-12-28 2008-07-17 Kobe Steel Ltd Steel for high-speed cold working and method for production thereof, and method for producing part formed by high-speed cold working

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0655237A (en) * 1992-06-08 1994-03-01 Rhythm Corp Manufacture of steering tie rod
JPH07305139A (en) * 1994-05-09 1995-11-21 Nippon Steel Corp Non-heat treated machine parts and production thereof
JP2006218502A (en) * 2005-02-09 2006-08-24 Kobe Steel Ltd Method, apparatus and program for deciding shape of die
JP2006231377A (en) * 2005-02-25 2006-09-07 Sanyo Special Steel Co Ltd Method for predicting shape after upsetting with hot-forging
JP2008163410A (en) * 2006-12-28 2008-07-17 Kobe Steel Ltd Steel for high-speed cold working and method for production thereof, and method for producing part formed by high-speed cold working

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