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1、精选优质文档-倾情为你奉上塑料在国民经济的多个领域中得到广泛的应用,而它的产量按体积计算在世界上已超过了钢铁的产量。同时, 塑料模具是塑料成型加工中不可缺少的工具, 在总的模具产量中所占的例逐年增加, 在当前已处于重要位置。在我国塑料模具的应用在国民经济中的地位愈来愈重要。它的钢材耗用量大, 品种规格多, 形状复杂, 表面粗糙度值要求低, 制造难度大。因此, 探讨塑料模具的制造中的选用材料与热处理问题, 综合分析其工作条件、失效、性能, 合理选用材料与热处理以及提高它的使用寿命, 保证制件质量,降低制造成本显得非常重要。1、塑料模具失效因素分析(1) 一般模具失效因素分析一般模具制造中包括模具
2、设计、选用材料、热处理机械加工、调试与安装等过程。根据调查表明: 模具失效的因素中, 模具所使用的材料与热处理是影响使用寿命的主要因素 , 其比例约占70%,国内外的有关资料也表明了相同的结果。从全面质量管理的角度出发, 不能把影响模具使用寿命的诸因素作为多项式之和来衡量, 而应该是多因素的乘积, 这样模具材料与热处理的优劣在整个模具制造过程中就显得特别重要。(2) 塑料模具失效因素分析塑料模具的重要失效形式为磨损失效, 局部塑性变形失效和断裂失效。当塑料模具使用的材料与热处理不合理, 塑料模具的型腔表面硬度低, 而耐磨性差, 其表现为, 型腔面因磨损及变形引起的尺寸超差; 粗糙度值因拉毛而变
3、高, 表面质量恶化。尤其是当使用固态物料进入塑模型腔, 它会加剧型腔面的磨损, 故塑料模产生了磨损失效。加之,塑料加工时含有氯、氟等成份受热分解出腐蚀性气体 HCl、HF, 使塑料模具型腔面产生腐蚀磨损, 形成侵蚀失效。局部塑性变形失效。塑料模具所采用的材料强度与韧性不足, 变形抗力低; 当填充的物料进入塑模型腔内, 有超载、持续受热, 周期受压, 而应力分布不均匀, 以及塑模型腔面硬化层过薄, 从而使塑模产生局部的塑性变形而引起的表面皱纹、凹陷、麻点棱角堆塌, 超过要求限度而造成失效以及回火不充分等因素使塑料模具寿命缩短, 过早的失效。断裂失效。塑料模具形状复杂, 多棱角薄边,应力严重集中在
4、韧性不足之外。同时, 塑料模采用合金工具钢回火不充分, 而发生断裂失效。从塑料模三种失效形式可知: 选用合理的塑料模具材料与热处理, 对它的使用寿命至关重要。故此,塑料模具材料的选用与热处理应满足下列要求:A1较高的硬度、良好的耐磨性、型腔硬度要求在 HRC3060, 淬火硬度大于 HRC55, 并且有足够的硬化深度, 心部有足够的强韧性, 以免脆断, 塑性变形。B1一定的抗热性, 在 150250 长期工作, 不氧化、不变形, 尺寸稳定性好。C1注射时, 有腐蚀介质析出, 要求有一定的耐蚀性。D1热处理变形小, 对精密模具来说, 要求变形小于0105%, 并且有足够的淬透性。E1切削加工性能
5、好, 具有优良的抛光, 耐磨性能, 镜面抛光可达 Ra 011 m以下。F1 焊接性, 锻造工艺性能良好12、塑料模具合理选材与热处理的基准随着对塑料模具的要求的提高, 对模具钢材也提出了更多的要求。即希望提供更多、更好的具有高硬度镜面加工性能好, 耐磨性能强的淬火, 回火类新钢材。但是, 还要根据塑料的类型以及对被成型的塑料制品的尺寸、精度、质量、数量不同的要求, 并考虑已有制造模具的条件来选用不同类型的塑料模具钢及其热处理。(1) 合理选用塑料模具钢表 1塑料模具钢的选用工作条件推荐钢号生产塑料产品批量较小, 精度要求不高, 尺寸不大的模具45、55钢或10、20钢渗碳在使用过程中有较大的
6、动载荷, 生产批量较大, 磨损严重12CrNi3A、20Cr、20CrMnMo、20Cr2Ni4A钢渗碳大型、复杂、批量较大、注射成型或挤压成型模具3Cr2Mo、4Cr3Mo3SiV、5CrNiMo、5CrMnMo、4Cr5MoSiV、4Cr5M0SiV1、热固性成型及要求高耐磨、高强度、塑料模具9Mn2V、7CrMn2WMo、CrWMn、MnCrWV、GCr15、5Cr2MnWMoVs、Cr2Mn2SiWMoV、Cr6WV、Cr12MoV、Cr12耐腐蚀和高精度塑料模具4Cr13、9Cr18、Cr18MoV、Cr14Mo、Cr14Mo4V复杂、精密、高耐磨塑料模具25CrNi3MoAL18N
7、i（250） 、18Ni （300） 、18Ni （350）(2) 塑料模具钢的热处理塑料模具如果采用常规的热处理质量无法保证,模具使用寿命短, 材料的利用率仅为 60%, 为此,对塑料模具中所使用的钢材, 应采用特别的热处理,以延长塑模使用寿命。对于要求心部具有高的强韧性和表面层的耐磨性的塑料模具, 可通过表面强化处理技术, 提高耐磨性和使用寿命。然而表面强化技术, 它不仅能提高塑模型腔表面的耐磨性, 而且能使塑模内部保持足够的强韧性, 这对于改善塑料模的综合性能, 节约合金元素, 大幅度降低成本, 充分发挥材料的潜力, 以及更好地利用新材料, 都是十分有效的, 实践证明: 表面强化技术是提
8、高塑模质量和延长其使用寿命的主要途径。采用电火花表面强化技术, 它是通过火花放电作用, 把一种导电材料（YT15、YT30） 涂敷及渗透到另一种导电钢制模 45钢 的表面上, 构成合金化的表面层, 从而改变模具工作面的物理和化学性能的一种工艺方法。为了使被强化的45 钢制模具的基体表面光洁, 事先必须将模具基体 45 钢 的工作面和电极表面清洗干净, 然后手握 D9110 强化机将电极 YT15、YT30 沿模具 45 钢制作 工作面移动, 并保持一定的压力, 使火花放电均匀连续。经电火化强化之后, 被强化表层 显微 硬度可达HV11001400, 甚至更高。其强化层与结合牢固, 耐冲击、不剥
9、落。强化处理时, 工件处于冷态, 且放电点极小, 时间短, 没有退火变形等现象, 这大大提高模具型腔面的耐热性、耐磨性、热硬性和耐蚀性,生产实践证明, 经电火花表面强化后, 挤出塑料模使用寿命可提高 1 倍以上, 强化层在使用过程中磨损后, 还可以重新进行强化。3 、塑料模选用材料的发展方向塑料模具对钢材的质量和性能有一些特殊要求。例如: 热处理变形小, 研磨与抛光性能好, 光洁度高, 有较强的花纹刻蚀性, 尺寸稳定, 有别于其他模具材料, 尤其是型腔复杂, 高精度的塑料模具对模具的选材有更高的要求, 但模具钢直接影响模具的寿命。现有的国产传统的模具钢从品种质量、性能等方面都不能满足现代化的生
10、产需求, 于是国内又开发与研制了一些新型的塑料模具钢, 以供选用。（1） 5CrMnMoVSCo 5NiSCo 高韧性易切削料、模具钢, 这种钢材在国内是首创, 其切削加工性、等向性、韧性和可锻性均好。5NiMoSCo 预处理采用调质工艺, 其淬火温度为 890900 , 油淬之后, 硬度在 HRC60 以上,650 回火后, 予处理硬度为 HRC35, 其切削加工性同退火状态的45 钢, 可顺利地进行多种切削加工。(2) SM1 和 SM2 塑料模具钢它属于硫系易切削模具钢, 用于要求高的注射模、压铸模, 效果良好。两种模具钢中的元素,S 以 MnS 型微粒夹杂存在, 可以起到减少切削力和易
11、于断屑的作用。SM 1锻轧之后, 迅速退火, 而 SM2 则不用退火, 直接经时效和预硬化处理可使用。二种钢经570 氮化后, 心部基体强度不变, 表面硬度可达 HV1100。SM2 可氮化与时效同时进行。4、国内外塑料模具发展水平的比较近年来确实发展很快 ,有些已达到或接近国际水平 ,尤其是随着改革开放政策的不断深入 ,“三资”企业蓬勃发展 ,对我国塑料模具设计制造水平的提高起到了非常大的作用。然而 ,由于我国模具制造基础薄弱 ,各地发展极不平衡 ,因此总体来看 ,与国际先进水平相比和与国内外市场需求相比 ,差距还很大。这主要表现在下列方面。(1) 塑料模具产品水平(2) 工艺装备水平我国塑
12、料模制造企业设备数控化率和 CAD/CAM应用覆盖面比国外低得多 ,且设备不配套、利用率低的现象十分严重。国产设备在精度、加工表面粗糙度、刚性、稳定性、可靠性及刀具和附件的配套性和精度保持性等方面与国外相比仍有较大差距。.(3)开发能力及经济效益等方面国外模具企业技术人员比例很高 ,多数企业在5%以上 ,有些在 50%以上 ,有些企业往往是大多数职工可在技术与生产岗位上互换 ,具有很高素质 ,加之企业对产品开发很重视 ,经常与产品厂一起共同开发产品与模具 ,因此有很强的开发能力。我国模具企业技术人员比例低 ,多数企业在 10%15%之间 ,且大多数只注重模具开发 ,不重视产品开发 ,因此综合开
13、发能力很低 ,在市场上常处于被动地位。经济效益方面 ,国外工业发达国家每个模具职工平均创造模具产值 15 万20 万美元 ,而我国只有 4万5 万元人民币。国外模具企业大都有一定利润 ,而我国模具企业大都是微利甚至亏损。.(4 )管理及其他方面国内外模具企业管理上的差距十分明显。管理上差距所带来的问题往往比技术上的差距更为严重。利用计算机进行科学管理在国外企业中已十分广泛 ,而国内还很少采用。到目前为止 ,通过 ISO9000 认证的模具企业全国还不到 1%。另外 ,诸如企业结构、产品结构、技术结构及企业运营机制等方面 ,国内外差距也较大。.(5)产需矛盾我国塑料模具市场总体上供不应求 ,特别
14、是大型、精密、复杂、长寿命塑料模产需矛盾十分突出 ,满足率只有 60%左右。尤其是为工程塑料配套的模具 ,目前满足率只有 40%左右。工程塑料是我国重点支持和优先发展的产业 ,预计每年将有 25%的增长率。为解决这个矛盾 ,每年只好大量进口。1999 年共进口塑模具约 4 亿美元 ,其中绝大部分是塑料模具。Plastics in a number of areas of the national economy has been widely used, and its production by volume in the world has exceeded the output of i
15、ron and steel. At the same time, plastic mold plastic molding are an indispensable tool for the mold in the total production has increased year by year the proportion of cases, in the present is in an important position. Plastic mold in China application status in the national economy more and more
16、important. Its steel consumption, and many varieties of different specifications, the shape of complex, low value of surface roughness, manufacturing difficult. Therefore, to explore the manufacture of plastic mold materials and heat treatment selection problem, a comprehensive analysis of their wor
17、king conditions, failure, performance, a reasonable selection of materials and heat treatment, as well as improve its service life and ensure the quality of parts, reduce manufacturing costs it is very important. 1,Factor analysis of plastic mold (1) Factor analysis of the general failure die Includ
18、ed in the general mold die design, selection of materials, machining heat treatment, testing and installation process. According to the survey show that: Failure of the factors that mold, used mold materials and heat treatment are the main factors affect the life, the proportion of about 70% of the
19、relevant information both at home and abroad also shows that the same results. Total quality management from the point of view of the impact of mold should not put life as a polynomial of the factors and to measure, but are the product of many factors, such mold materials and heat treatment of the p
20、ros at the whole process of mold manufacturing it is particularly important. (2) Failure factors of plastic mold Plastic mold of the important failure mode of failure for the wear and tear, failure of local plastic deformation and fracture failure. When the plastic mold materials and heat treatment
21、used unreasonable, plastic mold cavity lower surface hardness, wear resistance and bad, and its performance for the cavity surface and deformation due to wear and tear caused by the size of super-bad; roughness value as a result of the change nap high, the deterioration of surface quality. Especiall
22、y when the use of solid materials into plastic cavity model, it would aggravate the wear cavity surface, it produced a wear plastic failure. In addition, plastic processing contain chlorine, fluorine and other corrosive elements of the heat decomposition gases HCl, HF, so that produce plastic mold c
23、avity surface corrosion and wear, the formation of corrosion failure. local plastic deformation failure. Plastic mold material used in inadequate strength and toughness, deformation resistance is low; when the filler material into the plastic model of the cavity, there is overloading, continuous hea
24、t, compression cycle, and non-uniform stress distribution, as well as the cavity surface-hardening plastic model had a thin layer so that local produce mold caused by plastic deformation of the surface wrinkles, dents, pitting angular heap collapsed, more than the requirements, as well as the limits
25、 of failure caused by such factors as inadequate tempering plastic mold to make shorten the life span of premature failure. fracture failure. Plastic mold the shape of complex, multi-corner thin edge, the stress on the toughness of a serious shortage. At the same time, the use of plastic alloy tool
26、steel tempering inadequate fracture failure occurs. From the plastic shows the form of three types of failure: a reasonable choice of mold materials and heat treatment, it is essential for life. Therefore, the plastic mold material selection and heat treatment should meet the following requirements:
27、 A1 high hardness, good wear resistance, hardness cavity at HRC30 60, quenching the hardness more than HRC55, and there is enough depth of hardening, the center has sufficient strength and toughness to avoid brittle fracture, plastic deformation. The heat resistance must B1, 150 250 at the long-term
28、, non-oxidized, non-deformation, good dimensional stability. C1 injection, precipitation has corrosive medium, requires a certain degree of corrosion resistance. D1 deformation heat treatment of small, precision mold, the deformation is less than 0105 percent requirement, and there is sufficient har
29、denability. E1 good cutting performance, with excellent polishing, can wear, mirror-polished up to Ra 011 m below. F1 welding and forging process in good 12, plastic mold materials and heat treatment of a reasonable benchmark Plastic mold with the requirements of the improvement of the steel mold ma
30、de more demands. That wish to provide more and better processing of high-performance mirror good hardness, wear resistance and strong quenching and tempering of new steel. However, also according to the type of plastic molding on the size of the plastic products, precision, quality, number of differ
31、ent requirements, taking into account the conditions have been manufacturing molds to choose different types of plastic mold steel and heat treatment. (1) a reasonable selection of plastic mold steelTable 1 Selection of Plastic Mold Steel working conditionsSteel No. recommendThe production of small
32、quantities of plastic products, precision modest, size of the mold is not large45,55 or 10,20 Steel Carburizing SteelIn the use of the process there is a larger dynamic load, the production of larger quantities, wear serious12CrNi3A, 20Cr, 20CrMnMo, Carburizing steel 20Cr2Ni4A Large, complex, large-
33、volume, injection molding or extrusion mold3Cr2Mo, 4Cr3Mo3SiV, 5CrNiMo, 5CrMnMo, 4Cr5MoSiV, 4Cr5M0SiV1,Thermoset molding and high wear resistance, high strength, plastic mold9Mn2V, 7CrMn2WMo, CrWMn, MnCrWV, GCr15, 5Cr2MnWMoVs, Cr2 Mn2SiWMoV, Cr6WV, Cr12MoV, Cr12 Corrosion resistance and high-precisi
34、on plastic mold4Cr13, 9Cr18, Cr18MoV, Cr14Mo, Cr14Mo4VComplex, sophisticated, high wear-resistant plastic mold25CrNi3MoAL18Ni (250), 18Ni (300), 18Ni (350)(2)Heat treatment of plastic mold steelIf the use of conventional plastic mold heat treatment can not guarantee the quality, mold short life, the
35、 utilization of material is only 60%, to that end, on the plastic mold used in the steel, special heat treatment should be used to extend mold life. Requirements of the center for high strength and toughness and wear resistance of the surface layer of the plastic mold can be enhanced through the sur
36、face treatment technology, improve wear resistance and service life. However, surface hardening technology, which not only can improve the plastic model of the cavity surface resistance to abrasion, but also maintain enough internal mold of the strength and toughness, which is to improve the overall
37、 performance plastic, saving of alloying elements, a significant reduction in costs, and give full play to the potential of materials, as well as better use of new materials, are very effective, practical and proven: surface hardening technology is to improve the modeling quality and extending its l
38、ife to the major route of transmission. EDM surface hardening technology used, it is through the spark discharge effect, put a conductive material (YT15, YT30) coating and penetrate into a steel mold conductive surface 45 on steel, alloy composition of the surface layer, thereby to change the die fa
39、ce the physical and chemical properties of a process. Be enhanced in order to make 45 steel mold and smooth the surface of the substrate, must be pre-mold 45 steel substrate and the electrode surface of the face wash, and then machine will strengthen the hands D9110 electrode YT15, YT30 steel produc
40、tion along the die face 45 to move and maintain a certain degree of stress, so that continuous spark discharge uniformity. Enhanced by the electric cremation, the surface microhardness was enhanced up to HV1100 1400, or even higher. Enhanced layer and the combination of its strong, impact-resistant,
41、 non-peeling. Strengthening treatment, the workpiece in the cold, and the discharge point is extremely small, time is short, there is no deformation phenomena such as annealing, which greatly enhance the heat-resistant mold cavity surface, and resistance to abrasion, hot hard and corrosion resistanc
42、e, the production of practice has proved by the electric spark surface hardening, the plastic extrusion enhance the useful life of more than one, and strengthen the use of layers in the process of wear and tear, could also be re-strengthen. 3, plastic materials, the development direction of selectio
43、n Plastic mold steel quality and performance has some special requirements. For example: small-deformation heat treatment, grinding and polishing good performance, finish high, there is a strong etching of the pattern, size, stability, and is different from the other mold materials, especially cavit
44、y are complex, high-precision plastic mold of the mold material there is higher requirements, but a direct impact on die steel die life. Made available from the traditional varieties of mold steel quality, performance and other aspects of the production can not meet the needs of modernization, and d
45、evelopment and the development of domestic and some new type of plastic mold steel, selected for. (1) 5CrMnMoVSCo 5NiSCo free cutting high toughness materials, mold steel, this steel is the first in China, and its cutting, and isotropic, toughness and good forging of both. 5NiMoSCo - quenched and te
46、mpered the use of pre-treatment process, the quenching temperature of 890 900 , oil quenching, the hardness of HRC60 or more 650 after tempering, to deal with hardness HRC35, cutting of their status with the annealing of the 45 steel, can be successfully carried out a variety of machining. (2) SM1 a
47、nd SM2 plastic mold steel it is sulfur free cutting die steel grades for demanding injection mold, die-casting mold well. Two die steel elements, S-type particles to MnS inclusions exist, you can play to reduce the cutting force and the role of breaking easily. SM 1 after rolling forging, rapid anne
48、aling, annealing and SM2 is not directly by the statute of limitations and pre-hardening treatment can be used. Two kinds of nitrided steel by 570 , the intensity of the center of the matrix remains unchanged, the surface hardness of up to HV1100. Nitride and SM2 can be spent at the same time.4, pla
49、stic mold at home and abroad compared levels of development Indeed developed rapidly in recent years, some have reached or come close to international standards, especially with the policy of reform and opening up the deepening of the three capital enterprises to flourish, the plastic mold design and manufacture of our country