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附 錄
附錄A：
Research on orbital cold forging for the edge cam of automobile fuel injection pump
ABSTRACT: The experimental investigation and theoretical analysis of an orbital cold forging of an edge cam was explored. The effects of blank shape and the process parameters on the edge cam forming are discussed. Photoplastic technology was successfully applied to the simulation of an orbital cold forging process applied to an edge cam. The China-made polycarbonate (PCBA) was used as a simulation material, and a 3-D strain distribution was obtained inside the model materials, which provided theoretical guidance for optimizing process parameters on the orbital cold forging of the edge cam. The factors that caused a crack were identified and the deformation laws in orbital cold forging of an edge cam were clarified. The metal flow line, hardness, microstructures and accuracy of the orbital cold forged edge cam were found to meet the required service properties of the product.
Keywords: Orbital cold forging, edge cam, photoplasticity, simulation
1. INTRODUCTION
The edge cam of the automobile fuel injection pump is a key part with complicated shape and high precision, encountered high contact stress and a high shearing stress. It is hard to be made by the conventional forming processes or machining processes, and it doesn’t meet service properties of the product. The structural character and the forming property of materials of the edge cam were analyzed. Orbital cold forging is a forging process where a fixed bottom die and a moveable/orbiting top punch come together to form complex geometric workpieces with finished dimensional accuracy in a single forging operation. The orbiting upper die rolls over a metal blank while the bottom die is raised hydraulically. The billet is kneaded into the bottom die with relatively little force to produce a Near Net Shape or finished workpiece. This process features the orbiting upper die. Due to this orbiting motion over the workpiece, the resultant localized forces can achieve a high degree of deformation at a relatively low force level. As per the adjacent diagram, the forming force required, compared to conventional forming, is much lower due to a smaller contact area.
2. EXPERIMENT
2.1 Experimental equipment
The orbital forging press—Type PXWP-100C with capacity of 1600KN was employed for forming experiment. The orbital head completes 200 revolutions per minute. The inclined angle of the orbital head is adjustable 0° to 2° and there are four orbits selectable: circle, straight, spiral and daisy.
2.2 Selecting the blank shape
The geometric shape of the blank influences greatly the filling performance and the die life of orbital cold forged parts. If the selection is incorrect, it would either damage the die or make the work piece formation unsuccessful. According to the characteristic of the geometric shape of the edge cam, three kinds of blank shape were adopted to test.
Blank a) with the step and flange:
The size of the protruding step of blank with the function of fixing position in the lower die is basically same as the size of the edge cam. The shape of the edge cam can be formed by the orbital forging with small deformation.
Cylindrical blank b) with small step:
The size of the protruding step of blank with the function of fixing position in the lower die is basically same as the size of the edge cam. The shape of the edge cam can be formed by the orbital forging with large deformation.
Cylindrical blank c):
By the outside diameter of the cylindrical blank to fix position in the lower die, the shape of whole edge cam can be formed by the orbital forging with large deformation.
All three types of blanks can be successfully formed to the edge cam. Although the deformation of blank a) and blank b) are easier to form than the blank c), the blank a) and the blank b) require being preformed in mass production, thus it will incur high costs. In contrast, although the deformation of the blank c) is higher, its geometric shape is much simpler. Preforming is not a necessary process for blank c). It is suitable for mass production.
The work hardening of material plays a very important part in orbital cold forging. So to avoid the surface cracking of the blank in orbital cold forging, the softening annealing and good lubricating for blank are very much required. The orbital cold forging process for the edge cam is as below:
Blank——Spheroidizing annealing ——Baiting——Phosphating and soap treatment——Orbital cold forging.
2.3 Selecting orbital cold forging Parameters
If the orbit is a circle, the angle of oscillation can range from 0° to 2°. Once the angle is decided, the movement of the rocker will be not changed. If the angle is larger, the area between the rocker and work piece surface is also decreased, so the required deformation force is rather less, the forming time shorter. While a larger angle can bring higher efficiency, the accuracy of the parts will also be affected. This type of orbit is suited for producing axisymmetrical parts. If the spiral orbit is selected, orbital forging will be helpful for the radial and axial flow of the metal, and also has a better centre deformation; this rocker will apply action cyclically to the central area of the blank. So it is easy to form a part with a much complicated end face. Selecting a linear orbit, it will be easier to form a longer part such as hammer and chisel. If a daisy orbit is selected, the part with tooth profile such as bevel gear and jaw clutch will be formed more easily.
The angle of oscillation directly influences the deformation resistance and metal flow, the deformation resistance of theorbital cold forging is calculated as formula below:
P=0.45s2RtanγKπR2σs
Where: S—— feed per revolution, mm/r；
R—— maximum radius of the orbital cold forged part;
γ—— angle of oscillation;
σs—— yield strength of materials;
K ——influence coefficient of the friction, the inhomogeneous distribution of stress and the shape of forged part etc.
For the edge cam, S=1.2 mm/r; γ= 2°, σs=700 N/mm2 (the average yield strength of material 20CrMo), K=1.8, R=32.5mm， So, P=1444KN.
Thus, if the angle of oscillation is increased, the loading force is decreased, this is helpful for the radial flow of the metal. The maximum angle of oscillation 2° was applied for orbital cold forging of the edge cam. According to the characteristics of the edge cam’s geometric shape and the type of orbit, the circular motion of the orbital head is selected.
The process trial proves the filling property of metal is better, and the clear top & bottom faces of the edge cam was obtained.The lower die of orbital cold forging is generally very highly stressed. The lower die of orbital cold forging is similar to extrusion die. The lower die of orbital cold forging for the edge cam is reinforced by two stress rings. The lower die of orbital cold forging with axially-split inset was employed so as to minimize dangerous stress concentrations.
In order to prevent the curve surface and the protruding step of the edge cam from being worn down and a fracture failure, a mobile core is employed in the process, and then an ejector is used to push the forged part out after it is being formed.
3. PHOTOPLASTIC SIMULATION
Orbital cold forging deformation for the edge cam was studied with a photoplastic method. The model blank of photoplastic simulation need not to be split before forming. So the defects which the approximate portion of other experimental simulation methods is too large in studying the large deformation are avoided for photoplastic method. The photoplastic method can directly give us a set of the difference lines of equal principal strain, and a set of the direction tracks of principal strain in the model. It has many advantages such as: the strain diagram was directly perceived through the senses, and it’s reality, high measuring precision and high sensitivity. It is convenient for data collection, and provides a good way to study the plastic deformation which reflects the real situation.
The China made polycarbonate (PCBA) was used as a simulation material. The blank size of the model material (PCBA) was same as the blank size of the edge cam. The blank of the model material was directly orbital cold forged. The full-field strain distribution for orbital cold forging deformation was indirectly obtained by the similarity relationship.The full-field strain distribution which is on the section with height of 17mm along the Z axial direction of the edge cam for orbital cold forging.
From the strain distribution diagram, it was observed in the deformation of the edge cam, that the εZ of intermediate zone is compression strain, the radial strain εr and the tangential strain εθ of intermediate zone are tension strain where r≈10mm. This is identical with ordinary cylinder upsetting, and the fluctuation of strain value is low. But the fluctuation of strain value is higher where the intermediate zone r>10mm. It indicates that the deforming zone is inhomogeneous deformation. The max.radial strain εr was attained and the larger tangential strain εθ was also attained where r=25mm. As a result, the cracks occur easily in this zone. This is consistent with the cracks occurrence of orbital cold forging of the edge cam. The strain distribution of each Z axis section and deformation rules can be seen from the strain distribution diagram in orbital cold forging of the edge cam, such as the cracks occur easily in the maximal tension strain zone. The deformation homogeneity and detailed deforming of each deformation zone can be explored by the fluctuation of each strain value. It provides experimental basis for keeping defects of deformation cracks from happening, and fixing quantify datum for process experimental analysis. Thereby correct metal deformation laws were obtained in orbital cold forging of the edge cam.
4. RESULT AND ANALYSIS
Upon the completion of optimizing the process parameters, orbital forging of the edge cam analysis and experimental trials, the qualified orbital forged edge cam was obtained.
The microstructure of blank (Spheroidizing annealed condition) is composed of ferrite and pearlite.
After blank forging, the grain is elongated and distorted. It takes on the obvious fiber structure, and the crystal boundary and the slip line can’t be identified. Thus the grains were fragmentized in orbital forging of the edge cam, the amount of recrystallizing nucleus were increased in the subsequent heat treatment.
The interior zone of the edge cam is free from any defects. But the metal flow line of the machining made edge cam is cut off. The brinell hardness of blank (annealed condition) is 130-135HB on average, after deformation, as result of work hardening, the highest hardness of the edge cam reaches to 287HV, a 110% increase. The hardness distribution of the edge cam isn’t uniform. The hardness of the edge cam is higher where the strain is higher. This is consistent with experimental simulation and physical measurement. It indicates that the mechanical property of the edge cam by orbital cold forging is better than the machining made edge cam. The work hardening of the material caused by orbital cold forming increases tensile strength and hardness of the edge cam. The wear resistant property of the edge cam was greatly improved.
5. CONCLUSIONS
Upon the completion of the research on the orbital cold forging of the edge cam, the following conclusions are drawn:
(1) The complicated 3D curved parts with finished dimensional accuracy such as the edge cam of automobile can be formed in a single forging operation.
(2) The photoplastic technology can be applied to simulation of orbital cold forging process of the edge cam.
(3) The photoplastic technology gives us a theoretical basis for further exploration on orbital cold forging process, as well as the selection of the optimization process parameters.
(4) The metal flow line, hardness and metallographic structure of the orbital forged edge cam meet the service performance, which is better than machining made part.
(5) In comparison with hot precision forging, the orbital cold forging of the edge cam can save 1/3 of the material consumption, and the productivity increases by over five times. In comparison with machining, the orbital cold forging of the edge cam can save 2/3 of the material consumption, and the productivity increases by over ten times.
附錄B：
關(guān)于汽車噴油泵端面凸輪軌道冷鍛的研究
摘要:對試驗研究和理論分析的端面凸輪機構(gòu)軌道冷鍛進行了探討。在零件毛坯形狀的影響及工藝參數(shù)對成形的端面凸輪等方面進行了探討。光范技術(shù)成功應(yīng)用于模擬冷鍛工藝應(yīng)用于端面凸輪。針聚碳酸酯(PCBA)作為一個模擬的資料，并獲得了三維塑性應(yīng)變分布模型材料內(nèi)提供了理論指導(dǎo)為優(yōu)化工藝參數(shù)對軌道冷鍛。這個因素所引起的裂縫識別和變形規(guī)律在端面凸輪軌道冷鍛方面得到了澄清。發(fā)現(xiàn)了金屬流線，硬度，組織和準確性端面凸輪軌道冷鍛，滿足所需的服務(wù)性質(zhì)產(chǎn)品。
關(guān)鍵字： 軌道的冷鍛造，凸輪，光塑力學(xué)，模擬
1. 引言
汽車燃油噴射泵的端面凸輪是一種形狀復(fù)雜，精度高，遇到高接觸應(yīng)力、高剪切應(yīng)力的關(guān)鍵部件。用傳統(tǒng)的形成的過程或者機器加工過程做是很難的，并且它不是那些滿足服務(wù)性質(zhì)的產(chǎn)品。對其形成的結(jié)構(gòu)特點和材料性能的端面特征進行了分析。軌道冷鍛鍛造工藝是一個固定的底模和活動的軌道頂端沖頭一起完成具有一定幾何尺寸精度的復(fù)雜工件的一個單一的鍛造操作。軌道上模滾過金屬毛坯當(dāng)?shù)啄１灰簤号e升。揉進了鋼坯底部和相對小的力模具生產(chǎn)近凈形或完成的工件。該工藝是軌道上模。由于在工件上方的這種繞軌道運行的運動，因而發(fā)生的局限的力量在相對低的力量水平能實現(xiàn)高度的變形。按照鄰近的圖解，形成的力量需要，與傳統(tǒng)的形成相比，由于一個更小的接觸面積而低得多。
2. 試驗
2.1試驗設(shè)備
重1600KN 的PXWP-100C鍛壓機被用來做試驗。軌道頭完成200 轉(zhuǎn)/分。軌道頭的傾斜角度可調(diào)整0°到2°，有4個軌道可選：圓形，直線形，螺線形和扁帶形。
2.2選擇毛坯的形狀
幾何形狀的毛坯很大的影響填充性能及模具壽命的軌道冷鍛部分。如果選擇是正確的，它也不會破壞或使的工件形成以失敗告終。根據(jù)特征的幾何形狀的端面凸輪，對三種毛坯形狀進行了測試。
毛坯a：用這種措施和凸緣：
突出的大小的毛坯功能定位在上下模基本上是一樣大小的端面。這種形狀的端面凸輪能形成軌道小變形。
圓柱體的毛坯b：用簡單的步驟
突出的大小毛坯的功能定位在上下?；旧鲜且粯哟笮〉亩嗣妗６嗣嫱馆喌男螤钅苄纬绍壍来笞冃巍?
圓柱體的毛坯c:
通過外部的直徑圓柱毛坯來定位在上下模形狀的整體優(yōu)勢,可以形成凸輪和軌道大變形。
所有三種類型的毛坯可以成功地形成端面。雖然變形的毛坯a)和毛坯b)很容易形成需要被預(yù)先大批量生產(chǎn)，因此它會承受高額的費用。相反,盡管變形毛坯c)越高，其幾何形狀是非常簡單的，適用于大批量生產(chǎn)。
工作中起著非常重要的部分材料是軌道冷鍛。所以,為了避免表面裂紋的毛坯在軌道冷鍛、軟化退火，良好的潤滑是非常必需的。端面凸輪冷鍛工藝如下:
毛坯——球化退火——下料——磷化、肥皂處理——軌道冷鍛。
2.3選擇軌道的冷鍛造參數(shù)
如果軌道一圈、角振蕩的范圍可以從0°～2°。一旦角確定了，運動將沒有改變。如果這個角度越大，之間的區(qū)域,工件表面搖臂也下降，導(dǎo)致變形力是需要較少的時間形成。而大角度可以帶來更高的效率，精確的部分也會受到影響。這種類型的軌道適合生產(chǎn)回轉(zhuǎn)體零件。如果螺旋軌道被選中，軌道鍛造有利于徑向、軸向流的金屬，也有較好的中心變形，這搖臂將適用于變形狀況的毛坯的中心地區(qū)。所以很容易形成有一個更為復(fù)雜的頂面部分。選擇一個線性軌道時，它將會更容易形成一個較長的部分如鐵鎚和鑿刀，擊碎它。如果一個扁帶形軌道被選中，這個部分齒形錐齒輪和鄂式離合器將更容易形成。
這個角振蕩會直接影響變形抗力和金屬流動、耐候鋼的變形抗力的theorbital冷鍛的公式如下:
P=0.45s2RtanγKπR2σs
S - -每轉(zhuǎn)走刀量，mm/r；
R - -軌道冷鍛的最大半徑；
γ - -擺動角；
σs - -材料的屈服強度；
K - -摩擦的影響系數(shù)，鍛造部分的應(yīng)力不均勻分布等。
對于端面凸輪，S = 1.2毫米/轉(zhuǎn)； γ= 2°，σs = 700 N/mm 2(材料20 CrMo的平均屈服強度) ,K = 1.8，R = 32.5毫米，因此，P = 1444 KN。
因此，如果擺動角被增加，裝的力量被減少，這對金屬的徑向流動有幫助。最大擺動角2°申請軌道凸輪端面的冷鍛造。根據(jù)那些端面凸輪的幾何形狀和那些類型的軌道的特性，選擇圓形的軌道頭。
試驗證明填充合適的金屬是更好的,獲得明確的頂部和底部的端面凸輪。下模冷鍛通常是壓力很高。下模軌道冷鍛類似于擠壓模具。下模軌道冷鍛凸輪有兩個應(yīng)力加固環(huán)。下模軌道冷鍛使用軸向分開,最大限度地降低危險的應(yīng)力集中。
為了防止曲線表面和端面凸輪的磨損，從而斷裂失效，在這個過程中使用移動的核心，然后在形成后用排出器來推動鍛造部分分離出。
3.光范模擬
端面凸輪機構(gòu)的軌道冷鍛使用廣泛模擬來研究。光范模擬的毛坯模型成型之前不必分裂。因此，其它實驗?zāi)M關(guān)于大變形的缺陷的被光范模擬避免了。這個光范模擬方法可以直接給我們一套不同的平等主應(yīng)變，和一套軌跡模型中主應(yīng)變。它具有許多優(yōu)點，如: 直觀的應(yīng)變圖,通過它的實現(xiàn)測量精度和靈敏度高。方便的數(shù)據(jù)采集，并提供了一個很好的學(xué)習(xí)方法反映了塑性變形的實際情況。
中國制造的聚碳酸酯(PCBA)作為一個模擬的資料。這個尺寸的模型材料(PCBA)同樣大小的毛坯端面。該模型的毛坯材料是直接軌道冷鍛。細致的應(yīng)變分布為軌道冷鍛變形，是間接獲得相似的關(guān)系,以高度17mm Z軸方向沿端面凸輪軌道冷鍛。
從圖表，應(yīng)變分布的變形觀測的端面，εZ凸輪的過渡區(qū)是壓縮應(yīng)變、徑向應(yīng)變εr、拉伸應(yīng)變εθ≈10毫米。這等同于較低的普通圓柱鐓和波動的應(yīng)變值。但是波動的應(yīng)變值較高的過渡區(qū)r > 10毫米。結(jié)果表明，變形區(qū)是不均勻變形。這個最大應(yīng)變εr在切和更大的地方也達到εθ，r = 25毫米。作為結(jié)果，此區(qū)域容易發(fā)生裂縫。這符合軌道冷鍛凸輪裂縫的出現(xiàn)。變形性和每一個變形區(qū)變形可以由上下各應(yīng)變值反映。它提供了實驗基礎(chǔ)上的缺陷，保持變形的情況，安裝工藝試驗分析量化基準。金屬變形規(guī)律，從而獲得正確的端面凸輪軌道冷鍛。
4. 結(jié)果和分析
完成優(yōu)化工藝參數(shù)，端面凸輪軌道鍛造的分析和實驗測試，獲得合格的軌道鍛造端面凸輪。
微觀結(jié)構(gòu)的毛坯（球化退火條件）是由鐵素體和珠光體。
在鍛造毛坯之后，顆粒被拉長并且變形。它呈現(xiàn)出明顯的纖維結(jié)構(gòu)、水晶邊界和不被確認的滑移線。因此顆粒破碎在軌道鍛造端面再結(jié)晶，凸輪機構(gòu)在隨后增加核熱處理。顆粒將獲得精制，因而產(chǎn)品的機械性能會有所好轉(zhuǎn)。
端面凸輪的內(nèi)部區(qū)域沒有任何缺陷。但是金屬機器加工的線使凸輪端面被切斷。毛坯的(退火的狀態(tài))布氏硬度平均是130-135 HB，在變形之后，由于工作硬化，端面凸輪的最高硬度伸到287 HV，110%的增加。與端面凸輪的硬度分配不一致。端面凸輪強度更高的地方，硬度更高。這與實驗?zāi)M和物理測量一致。它表明通過冷鍛造的端面凸輪的軌道的比機械加工更好。硬化工作所造成的物質(zhì)軌道冷成型增加端面凸輪的抗拉強度和硬度。端面凸輪的耐磨損性能被大大改進。
5. 結(jié)論
當(dāng)完成對端面凸輪冷鍛軌道的研究時，得出下列結(jié)論：
⑴單一鍛造操作可完成復(fù)雜的三維曲面零件尺寸精度諸如汽車的端面凸輪機構(gòu)。
⑵光范技術(shù)可用于模擬鍛造工藝的凸輪冷鍛軌道。
⑶光范技術(shù)在一個理論基礎(chǔ)上進一步探索軌道冷鍛工藝，以及優(yōu)化工藝參數(shù)。
⑷金屬流線、硬度和軌道的金相組織凸輪端面鍛造滿足使用性能，這是優(yōu)于機械加工的一部分。
⑸與熱精密鍛造相比，端面凸輪軌道冷鍛能節(jié)省1/3的材料消耗，而生產(chǎn)率增加超過5倍。與機械加工相比，端面凸輪軌道冷鍛能節(jié)省2/3的材料消耗，生產(chǎn)率更是增加了超過10倍。
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