冷冲模具使用寿命的影响[1]
冷冲模具的使用寿命是以冲制出的工件数量来计算的。影响冷冲模寿命的因素很多。主要有模具结构设计、制造模具所用凸模和凹模的材料、模具的热处理质量与表面强化、冲模零件的制造精度和冷冲压材料的选取。除此之外，还有冲模的安装、调整、使用以及维修等。
1．模具设计对寿命的影响
(1)排样设计的影响排样方法与搭边值对模具寿命的影响很大，过小的搭边值，往往是造成模具急剧磨损和凸、凹模啃伤的重要原因。从节约材料出发，搭边值愈小愈好，但搭边值小于一定数值后，对模具寿命和剪切表面质量不利。在冲裁中有可能被拉人模具问隙中，使零件产生毛刺，甚至损坏模具刃口，降低模具寿命。因此，在考虑提高材料利用率的同时，必须根据零件产量、质量和寿命，确定排样方法和搭边值。
(2)凹模结构的影响对容易产生应力集中而开裂的凹模结构，可以采用组合结构或镶拼结构，以及预应力结构，从而提高模具使用寿命。
(3)间隙的影响当间隙过小时，压缩挤压利害，摩擦力增大，磨损增大，侧面的磨损加剧，冲裁后卸料和推件时，材料与凸、凹模之间的摩擦还将造成刃口侧面的磨损比端面的磨大大，同时也容易造成凸、凹模温度很高，把金属碎屑吸附在刃口侧面，形成金属瘤，使凸、凹模出现崩刃或胀裂现象。因此，过小的间隙对模具寿命极为不利。间隙太大，会增加凸模与凹模端面边缘的集中应力，致使压应力急剧增加，于是刃口边很快屈服变形而失去棱角。因此又增加了冲裁力，进而使刃口边更快磨损，降低模具寿命。但为了减小凸、凹模的磨损，延长模具使用寿命，在保证冲裁件质量的前提下，设计时适当采用较大间隙是十分必要的。
(4)模具导向结构对寿命的影响可靠的导向对于减小工作零件的磨损，避免凸、凹模啃伤是非常有效的。特别对无问隙或小问隙冲裁模、复合模和多工位级进模更为重要。为提高模具寿命，必须根据工序和零件精度要求，正确选择导向形式和导向精度，所选择导向精度应高于凸、凹模的配合精度。
(5)冷冲压材料选取的影响冷冲压材料应满足制件的设计要求和冲压工艺要求，否则容易损伤模具，降低模具使用寿命。冷冲压材料表面质量不好，冲压时制件易破裂，也易擦伤模具。冷冲压材料塑性不好，变形量小，冲压时制件易破裂，也易擦伤模具。另外，材料的厚度公差应符合国家标准。因为一副冲模适用于一定材料的厚度，成形、弯曲、翻边、引伸模具的凸、凹模结构间隙是直接根据材料厚度来确定的。所以材料厚度不均匀，会导致废品产生和模具损坏。
2．模具材料对模具寿命的影响
模具材料对模具寿命的影响是模具材料性质、化学成分、组织结构、硬度和冶金质量等的综合反映。其中，材料性质和热处理质量影响最为明显。模具材料性质对模具寿命的影响是很大的。如将同一种工件，使用不同的模具材料做弯曲试验，试验结果：用9Mn2V材料，其寿命为5万次；用Crl2MoV渗氮，其寿命可达40万次。因此，在选用材料时，应根据制件的批量大小，合理选用模具材料。模具工作零件的硬度对模具寿命的影响也很大。但并不是硬度愈高、模具寿命愈长。这是因为硬度与强度、韧性及耐磨性等有密切的关系。有的冲模要求硬度高，寿命长。如采用T10钢制造冲模，硬度为54～58HRC，只冲几千次，制件毛刺就很大。如果将硬度提高到60～64HRC，则刃磨寿命可达2～3万次。但如果继续提高硬度，则会出现早期断裂。有的冲模硬度不宜过高，如采用Crl2MoV制造凹模硬度为58～62HRC时，一般寿命为2—3万件，失效形式是崩刃和开裂以及如果将硬度降到54～58HRC，寿命提高到5～6万件，但硬度降低到50～53HRC会出现凹模刃口易磨钝现象。由此可见，模具硬度必须根据材料性质和失效形式而定。应使硬度、强度、韧性及耐磨性、耐疲劳强度等达到特定冲压工序所需要的最佳配合。
3．模具的热处理质量与表面强化对寿命的影响
模具的热处理质量对模具的性质与使用寿命影响很大。实践证明，模具工作零件的淬火变形与开裂，使用过程中早期断裂，虽然与材料的冶金质量、锻造质量、模具结构及加工有关，但与模具的热处理关系更大。根据模具失效原因的分析统计，热处理不当引起的失效占50％ 以上。实践证明，高级的模具材料必须配以正确的热处理工艺，才能真正发挥材料的潜力。模具工作零件表面强化处理的目的，是获得外硬内韧的效果，从而得到硬度、耐磨性、韧性、耐疲劳强度的良好配合。模具表面强化处理方法很多，表面处理的新技术工艺发展很快。除氮碳共渗和离子氮化、渗硼、渗铌、渗钒、表面镀硬铬和电火花强化外，化学气相沉积(CVD)和物理气相沉积(PVD)已逐步采用。经CVD和PVD处理后，模具表面覆盖一层超硬物质，如TiC、TiN等。硬度极高、耐磨性、耐蚀性、抗黏合性很好，可提高模具寿命几倍到几十倍。
4．冲模零件的制造精度对模具寿命的影响
冲模制造的精度与使用寿命关系很大，特别是模具表面粗糙度对模具影响很大。如用Crl2MoV钢制造落料模，如果表面粗糙度值R =1．6 m时，其寿命为3万件左右。如经精抛光，表面粗糙度值R =0．4 m，寿命可提高到4—5万件。因此，对模具工作零件表面，一般都要经过磨削、研磨、抛光等精加工和精细加工。
5．其他方面对模具寿命的影响
(1)压力机的精度不高，也易使冲模损坏。
(2)冲模在压力机上安装的正确与否及操作者的技术水平高低，对模具寿命也有很大影响。
(3)冲模的保管和维护好坏，以及使用润滑剂的情况，也影响模具使用寿命。
冷冲模凸凹模间隙控制和调整方法
冷冲压模具凸、凹模间隙的大小和均匀程度直接影响冲裁件的质量和模具的使用寿命的长短。在保证冲裁件间隙时装配也是模具制造中十分重要的环节，而且装配质量将直接影响凸、凹模的间隙是否均匀。比如加工时凸、凹模的尺寸精度虽已达到要求，但是在装配时如果调整不好，就会造成间隙不均匀，冲出的零件有毛边。甚至会冲出不合格的零件。模具装配的关键是要控制凸、凹模的相对位置，以保证凸、凹模的间隙正确、均匀并能冲出合格的零件。
1.模具在装配前应关注的问题[2]
凸、凹模间隙既与模具本身零件的精度有关，也与装配时的装配工艺是否合理有关。为了保证凸、凹模的位置正确和间隙均匀，模具从设计、加工到装配整个环节要注意的问题如下：
（1）凸、凹模的正确设计和制造
设计模具时首先应根据冲裁件的断面质量、模具使用寿命等因素选择合理的凸、凹模间隙。并要考虑到模具在使用过程中的磨损使间隙增大，一般在设计模具时采用最小合理间隙。并在制造过程中保证模具零件的加工质量和精度，在装配过程中确保凸、凹模间隙均匀，这对于加工复杂形状零件十分关键。
（2）装配方法的选择要合理
冲模装配方法大致包括直接装配法和配合装配法。装配前必须仔细研究模具装配图，充分考虑和分析冲模的结构特点、冲模零件加工工艺和加工精度等，以选择方便、准确、可靠的装配方法以保证冲裁件质量。
2.凸、凹模间隙的控制与调整的方法【3】
凸、凹模的间隙控制，应根据冲模结构、间隙大小、冲裁件的质量和实际装配条件来选定。凸、凹模间隙的控制与调整方法有以下几种。
（1） 透光法
将凸、凹模合模后，用光照射底面，观察凸、凹模刃口周围透过的光线和分布情况来判断间隙的大小和均匀性。如果不均匀，重新调整至间隙均匀后再固定，此法适用于薄板小间隙冲裁模。
（2） 塞尺法
将凸、凹模合模后，用凸、凹模单边间隙厚度的塞尺塞入凸、凹模各方向间隙中。然后拧紧上模固定螺钉。最后放纸试冲，最后将上模座与固定板配钻、铰定位销孔，并打人销钉定位。
（3）垫片调整法
垫片调整间隙法简便、应用广泛。如图1所示，合模后垫好等高垫铁，将垫片包在凸模上使凸模进入凹模内，观察凸、凹模的间隙状况。如果间隙不均匀，用敲击凸模固定板的方法调整间隙，然后拧紧上模固定螺钉。最后放纸试冲，观察切纸上四周毛刺均匀程度，从而判断凸、凹模间隙是否均匀，再调整间隙直至冲裁毛刺均匀为止。最后将上模座与固定板配钻、铰定位销孔，并打入销钉定位。这种方法广泛适用于冲裁材料较厚的大间隙冲模和弯曲、拉深成形模具的间隙控制。
（4）化学法
当凸、凹模的形状复杂时，用上述几种方法调整间隙较困难时，这时可用化学方法来控制间隙，常用的是电镀法。电镀法是在凸模工作端表面镀上一层铜或锌来代替垫片。镀层厚度与单边隙相同，刃人凹模孔内，检查上下移动无阻滞现象即可装配紧固。镀层在冲模使用过程中会自然脱落，无需去除。此法镀层均匀，可提高装配间隙的均匀性。
（5）工艺措施调整法
采用工艺措施调整模具间隙主要有2种方法：
1.尺寸法
加工凸模时，将凸模前端适当加长，加长段截面尺寸加工到与凹模型孔尺寸相同。装配时，使凸模进入凹模型孔，自然形成冲裁间隙，然后将凸模连同凸模固定板一起与上模座配作销钉固定，最后将凸模前端加长段去除即可形成均匀间隙。
2.定位孔法
工艺定位孔法就和级进模里面的原理差不多。加工时，在凸模固定板和凹模相同的位置上加工两定位孔，可将定位孔与模具型腔一次割出。装配时，在定位孔内插入定位销来保证间隙。
（6） 标准样板法
根据零件图预先在线切割机床上加工一标准样板或采用合格冲压零件，装配调整时将其放在凸、凹模之间，使上、下模相对运动时松紧程度适当即可。
（7） 测量法
测量法采用的测量工具有塞尺。塞尺测量法调整后的凸、凹模间隙均匀性好，是常用的方法。装配时，在凸模刃口放入凹模孔内后，根据凸、凹模间隙的大小选择不同规格的塞尺插入凸、凹模间隙中，检查凹模刃口周边各处间隙，并根据测量结果进行调整。调整时只要敲击凸模固定板直至调整好为止。
(8)调整修配法
冲模在使用一段时间后，由于凸、凹模的正常磨损。要对所加工的零件进行检查，若制品产生毛刺，凸、凹模刃口变钝和崩刃因素，则是因为凸、凹模间隙因磨损发生了变化，即变大或不均匀。为使凸、凹模恢复到原来的间隙值冲出合格零件可采用以下方法进行修配。
1. 凸、凹模间隙变大的修配方法
一般冲模在使用一段时间后，由于正常磨损会使凸、凹模间隙逐渐增大，从而使工件产生毛刺等一系列的问题。这种情况下，可先用厚度等于单面间隙值的块规插入凸、凹模刃口之间，若凸、凹模间隙不太大，修磨工作部分的刃口继续使用，可改善冲件质量。当间隙值过大时，则可采高温加热后局部锻打的方法重新修正凹模尺寸使其恢复到原来的间隙值。工件冷却后，再用压印锉修法重新修整间隙值，并用火焰表面淬火的方法来提高刃口表面的硬度。
2. 凸、凹模间隙不均匀的修配方法
冲模使用一段时间后，间隙不均匀会使冲件局部边缘产生毛刺或刃口被咬坏。在冲模正常磨损情况下，由于导向装置磨损后精度降低使得凸、凹模相对发生偏移，应分别在导柱和导套上镀一层铬使其恢复到原来的尺寸，再通过压印锉修法将高点去除。如果是由于定位销松动失去定位作用而致使凸、凹模不同心，从而引起凸、凹模间隙不均匀。应先将凸、凹模间隙调整好，重新配作销钉固定。
Die Life of cold stamping die and influence
Die with the life of the workpiece by punching out the number of terms. Many factors affect the life Die. There are die structure design, manufacture molds used in the punch and die materials, die quality and surface hardening heat treatment, precision die manufacturing parts and cold stamping materials selection. In addition, there are die installation, adjustment, use and maintenance.
1. Die Design on Life
(1) Layout design of layout methods and take the boundary value a great impact on the die life, too small to take the boundary value, often causing rapid wear and convex mold, die bite wounds on the. Starting from material savings, take the boundary value smaller the better, but take the edge is less than some value, the cut surface of the mold and the quality of life adversely. There will be left behind in the blanking die Q-gap were to produce spare parts glitch, or even damage the die edge, reduce die life. Therefore, consider increasing the material utilization of the same time, parts must yield, quality and life expectancy to determine the layout methods and take the boundary.
(2) die structure prone to stress concentration on the cracking of the die structure, composite structure can be used or mosaic structure, and prestressed structure to enhance the mold life.
(3) the impact of clearance when the gap is too small, compressed extrusion of interest, increased friction, increased wear, the wear side of aggravated discharge and push pieces after blanking time, materials and convex, the friction between die will cause wear and tear than the end edge on the side of the grinding much, but also easily lead to convex, concave mold temperature is high, the adsorption of metal debris in the side edge to form a metal tumor, so that male and female die chipping or expansion occurs crack phenomenon. Therefore, the gap is too small to Die Life very bad. Gap is too large will increase the punch and the die face the edge of the concentration of stress, resulting in a sharp increase in stress, so blade edge quickly lose angular yield deformation. Therefore, addition of blanking force, thereby enabling faster edge edge wear, reduce die life. But in order to reduce the male and female die wear, extending mold life, while ensuring quality of stamping pieces under the premise that larger space designed properly it is necessary.
(4) Die-oriented structure of the life of a reliable guide for the working parts reduce wear, prevent male and female die bite wound is very effective. In particular, non-small-Q gap Q gap or Die, compound die and multi-position progressive die even more important. To improve the die life, must be based on processes and the demand of precision, the correct choice-oriented form and orientation accuracy, the choice should be higher than the accuracy-oriented convex, concave mold with precision.
(5) the impact of cold stamping materials, cold stamping materials selected should meet the design requirements of workpieces and stamping process requirements, or easy to mold damage and reduce mold life. Poor surface quality of cold stamping, punching, cracking when the workpiece is also easy to scratch mold. Bad cold stamping plastic materials, deformation is small, easy to press when the workpiece rupture, but also easy to scratch mold. In addition, the material thickness tolerances shall comply with national standards. Die because of a certain thickness of material suitable for forming, bending, flanging, drawing die of the male and female die structure gap is directly determined by the thickness of the material. Therefore, uneven thickness, will result in waste generation and mold damage.
2. Die Die Life of
Die Die Life of a mold material properties, chemical composition, structure, hardness and comprehensive reflection of metallurgical quality. Among them, the material properties and heat treatment affect the quality of the most obvious. Mold material properties on the impact of die life is great. If the same workpiece, using a different mold material of the bending test, the test results: The 9Mn2V material, the life of 5 million; with Crl2MoV nitriding, the life of up to 40 million. Therefore, the choice of materials, the batch size should be based on workpiece, rational use of mold materials. The hardness of the die parts to Die Life a great impact. But not the higher hardness, longer die life. This is because the hardness and strength, toughness and abrasion resistance are closely related. Some die demands of high hardness, long life. Such as the use of T10 steel dies, hardness 54 ~ 58HRC, only washed thousands of times a burr on the workpiece great. If the hardness to 60 ~ 64HRC, the grinding life of up to 2 to 3 million. However, if continue to improve hardness, fracture occurs earlier. Some die hardness should not be too high, as the die manufacturing using Crl2MoV 58 ~ 62HRC hardness, the general life of 2-3 million, invalid form of chipping and cracking, and if the hardness down to 54 ~ 58HRC, life expectancy increased to 5 ~ 60 000, but decreased to 50 ~ 53HRC hardness appears easy to blunt the die edge phenomenon. Thus, mold hardness must be based on material properties and failure modes may be. Should enable the hardness, strength, toughness and wear resistance, resistance to fatigue strength needed to achieve a particular stamping process the best match.
3. The surface of the mold heat treatment to strengthen the quality and impact on life
Mold heat treatment the nature and quality of life of the mold a great impact. Practice shows that the die parts of the quenching distortion and cracking, early fracture during use, while the metallurgical and materials quality, forging quality, mold structure and process related, but related more to die of heat treatment. According to statistical analysis of failure causes of mold, heat treatment failure due to improper accounting for more than 50%. Practice shows that the mold material must be accompanied by high heat treatment process properly, can really play a material's potential. Parts surface hardening mold work purpose is to obtain the effect of external hard tough inside, so be hardness, wear resistance, toughness, good resistance to fatigue with. Many ways to die surface hardening, surface treatment technology of new technologies developed rapidly. In addition to Nitrocarburizing and ion nitride, boride, seepage niobium, vanadium permeability, hard chrome plated and spark strengthening, the chemical vapor deposition (CVD) and physical vapor deposition (PVD) has been gradually adopted. By CVD and PVD treatment, the mold surface covered with super-hard material, such as TiC, TiN, etc.. High hardness, wear resistance, corrosion resistance, adhesion is very good, can improve the die life several times to several times.
4. Manufacturing precision of the die parts of die life
Precision die manufacturing and life in it in particular, mold surface roughness on the mold a great impact. If using Crl2MoV steel blanking die, if the surface roughness value R = 1.6 m, its life span is about 30,000. Such as polished by the precision, surface roughness value R = 0.4 m, life can be increased to 4-5 million. Therefore, the working parts of the mold surface, the general must go through grinding, grinding, polishing and other finishing and fine processing.
5. Other aspects of the impact of die life
(1) Press the accuracy is not high, but also easy to make die damage.
(2) die in the press or not installed properly and the operator's technical level, on the tool life is also greatly affected.
(3) dies in the custody and maintenance of good and bad, and the use of lubricant condition also affects mold life.
Cold die clearances between control and adjusting method
Cold stamping mould convex, concave die size and distribution of the clearance degree directly affect the quality of the blanking pieces and the length of the service life of the die. In guarantee blanking pieces space is mould manufacturing assembly very important link, and assembly quality will directly influence the convex, concave die if the clearance between the uniform. Such as the process of convex, concave die size precision although already meet the requirements, but in assembling if adjustment is bad, can cause clearance does not even, rushed out of the spare parts of the raw edges. Even rushed out of unqualified parts. The mold assembly is key to control convex, concave die of relative positions, in order to ensure that the convex, concave die, uniform and the clearance between the right to rush out of qualified parts.
1. Die before assembly the problems that should be paid attention[2]
Convex, concave die and mould parts itself is clearance of the precision, and the assembly of the assembly process is reasonable. In order to ensure that the position of the convex, concave die correctly and gaps even, mould design, processing to assembly from the whole link should pay attention to the following questions：
（1）Convex, concave die design and manufacture of the right
Design should be based on the above all when die cutting the section of a quality, service life of die factors such as the reasonable selection of convex, concave die clearance. And to consider the mould in the process of using that gap wear increases, general in the design the least reasonable clearance when mould. And in the manufacturing process can ensure the parts processing precision and quality, in the assembly process ensure convex, concave die gap even, this for processing complex shape is very key parts.
（2）Assembly method the choice should be reasonable
Die assembly method include roughly assembly method and direct with assembly method. Before the assembly must be carefully study mold assembly drawing, full consideration and analysis of the structure characteristics of punching die, die parts processing technology and processing accuracy etc, in order to choose convenient, accurate and reliable assembly method to ensure the quality of blanking pieces.
2. Convex, concave die gap between the control and adjustment of the method[3]
Convex, concave die clearance control, should according to die structure, clearance size, blanking pieces of quality and practical assembly condition to selected. Convex, concave die gap between the control and adjustment method have the following kinds.
（1）Pervious to light method
Will convex, concave die after molmerged, shone a light on the underside, observe the convex, concave die around through light and distribution to judge the size of the clearance and uniformity. If not even, to adjust to evenly between fixed again, this method is suitable for small gap plate stamping die.
（2）Feeler method
Will convex, concave die after molmerged, convex, concave die into the thickness of unilateral clearance feeler convex, concave die gaps in each direction. Then tighten the screw on mode. Finally put paper to stamping and will last mould seat and fixed on board with drilling, reaming positioning pin hole, and at a pin location.
（3）Gaskets DiaoZhengFa
Gasket adjustment method is simple, convenient, clearance is used widely. As shown in figure 1 shows, the mat with good contour mat iron, will gaskets wrapped in the punch to the punch into the concave mould, observe the convex, concave die clearance condition. If clearance does not even, with striking the protruding models of fixed plate method clearance adjustment, then tighten the screw on mode. Finally put paper to stamping, observation on paper cutting around burr and even rate to judge whether clearance convex, concave die even, to adjust the gap until cutting burr uniform so far. Finally the mould seat and the plate with drilling, reaming positioning pin hole, and enter the pin location. This method widely used cutting materials focusing thick large clearance and bending stamping, deep drawing mould clearance control.
(4) Chemical method
When the convex, concave die complex shape, the use of the above several methods more difficult to adjust the gap, the chemical method can be used to control the gap, the plating method is used. Plating method is the punch in the work surface coated with copper or zinc instead of washers. The plating thickness and unilateral gap is same, blade people concave die hole, and check the move without block phenomenon can assembly tighten. Coating in use process will die fall off naturally, need not removed. This uniform coating, can improve the uniformity of assembling clearance.
(5) Technology DiaoZhengFa measures
The main technological measures to adjust the gap between two kinds of the mould method:
1. Size method
Processing of the punch, will the punch front-end appropriate lengthen, extended period of section size and sunken model hole processing to the same size. Assembly, make the punch into female model hole, natural form the cutting clearance, and then to the punch with fixed together with the punch mould seat on board with the pin for fixed and will last longer period of the punch front can remove form even clearance.
2. Positioning hole method
Process positioning hole method and the inside of the progressive die principle about. Processing, the punch in fixed board and concave die on the same position processing two positioning hole, can will locate hole and the mold cavity a cut out. Assembly, in the positioning hole insert pins to ensure that gap.
(6) Standard model method
According to the drawing wedm in advance in processing a standard model or the qualified stamping parts, to adjust the assembly put it in between convex, concave die, upper and lower die relative motion can be reasonable degree when appropriate.
(7) Measurement method
Measuring method of the measuring tool have feeler. A feeler method after the adjustment convex, concave die clearance good uniformity, it is the commonly used method. Assembly, the punch in the concave die in the hole, convex, concave die according to the size of the clearance choose different specifications of the feeler insert convex, concave die clearance, inspection concave die around the blade gap everywhere, and according to the measured results adjustment. If the adjustment of the punch fixed board knock until adjust good so far.
(8) Adjustment method of repair match means
Die in use after period of time, because the convex, concave die normal wear and tear. To working parts inspection, if products produce burr, convex, concave die dull and collapse the blade factors, it is because of the convex, concave die clearance for wear changed, namely bigger or not even. To make the convex, concave die restored to the original gap value out of parts can use the following method to qualified for repair match means.
1. Convex, concave die clearance greaten repair match means method
General dies in use after period of time, because normal wear will make convex, concave die gap increase gradually, thus to make the work and so on a series of problems produced burr. This kind of circumstance, can use first thickness is equal to one of the KuaiGui insert gap between the convex, concave die, if convex, concave die clearance does not too big, the grinding work part of the blade continue to use, can improve the quality of stamping. When gap value too big when, the recoverable high temperature heat of local forging the modification methods female die size make it restored to the original gap value. Workpiece cooling followed by the pressure seal the law to file to trim gap value, and with the flame hardening method to improve the blade surface hardness.
2. Convex, concave die clearance does not even repair match means method
Dies after a period of using, clearance does not even can make blunt a local produce burr or the blade was edge chewed. In normal wear punching die, because after wearing precision guide device that reduce convex, concave die happen relatively migration, respectively in the guide pin and a guide to cover on the plating chromium layer the restored to its original size, again through the pressure seal the law will remove file high. If it is due to the pins loosening lose positioning function and cause different convex, concave die heart, and cause convex, concave die clearance does not even. Should first will convex, concave die gap adjusting well, to match for taper pin.
参考文献
[2]谢昱北. 《模具设计与制造》.2005年 北京 北京大学出版社.
[3]薛兽翔. 《冲压模具与制造》.2004年 北京 北京化学工业出版社.
[5] CHEN Zhi-ming ZHANG Hai-ou WANG Gui-lan. China's mold industry current situation and development[J]
Forging & Stamping Technology. 2004
年 05期 1-2
