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Previous editions of Technical Tidbits have focused onhow to select the proper alloy and temper of base metals for use in electricaland electronic connectors. This is an important decision, although there aremany more design choices that must be made. Miniaturization demands smallspring contacts, which are often formed from wire (flat or round), or stampedand formed from strip. This issue of Technical Tidbits focuses on thedifferences between strip and wire, and how to choose the proper form. 我们在其他的文章中有讨论对于连接器如何选择合适的合金和回火状态。影响选择的因数有很多。小型化的要求需要使用小的弹簧触点，这些触点通常由线材（扁平或者圆形）制备或用带材冲压而成。本文的讨论主要集中于线材和带材之间的区别，以及如何选择合适的形式。 Sometimes it is very easy to make the choice. Certainalloys and tempers are available only as strip, and others are available onlyas wire. Wire is usually available in longer coils than strip, while strip isavailable in much larger widths than flat wire. However, wire has tighter widthtolerances than strip. Wire does not offer the same design flexibility that stripdoes. For example, if the part to be stamped has a great deal of surface area,wire may not be wide enough to meet the demand. Furthermore, if a contact has avery irregular cross section with several bends in both the longitudinal andtransverse directions, then strip is the material of choice. On the other hand,if the contact is a simple shape with constant cross section, then wire willwork perfectly. 有时候做出决定是比较简单的。某些合金和回火状态只能由带材提供，而一些合金和回火状态只能由线材提供。从尺寸上来说：线材通常比带材长度长；带材的宽度比线材大，但是线材公差更严格。从设计灵活度上来说，线材的设计灵活性与带材不同。例如，如果要冲压的零件要求很大的面积，线材则不够宽，无法满足要求。如果触点的横截面非常不规则，且在纵向和横向上有多个弯曲，则需要选择带材。如果触点是具有恒定横截面的简单形状，则适合选择线材。 Narrow width strip must be slit from the muchwider coils that are produced by copper mills. At each slit edge, there arefour features of interest. Rollover is the area at the top (beginning)of the slit that has been crumpled downward by the slitting knife. Shear isthe area that has been sheared into a straight edge by the knife. The last partof the slit edge will be literally torn out of the cross section. This area istermed fracture or break. A burr is a small, sharp ridgeof material extending from the bottom of the fracture zone. Since burrs canbreak off, possibly even resulting in connector shorts, finished contacts areoften chemically or physically deburred, at an additional cost. The left sideof figure 1 demonstrates the features of the slit edge, while the right sidecompares the cross sectional shapes of wire and strip. Note that the edgefeatures are exaggerated in the figure for clarity. The sizes of the rollover,shear, and break zones, as well as the size of the burrs, depend on theclearance between, and vertical overlap of, the slitting knives. It isimportant to note that these features appear on the edges of stamped parts aswell. 想要得到窄带，需要通过母卷宽度的材料上分条得到。在分条的边缘，有四个典型特征：滚转，是指切缝顶部被分条刀向下压皱的部分；剪切，是指被刀具剪切成直边的区域；撕裂，切缝边缘的最后一部分不是剪切而是撕裂；毛刺，是料带撕裂端延伸出来的小而锋利的部分。由于毛刺可能会脱落，严重时会导致连接器短路，因此一般会以化学或者物理方法去毛刺，这会带来额外的成本。图1的左边图显示了分条切口的特征，而右边图比较了线材和带材横截面形状。图中的特征被放大，为了更清晰的表现。各个区域的大小，取决于分条刀之间的间隙和作用重叠的区域。对于冲压的截面，也是同样道理。 Figure 1. Shapedifferences between drawn wire and slit strip. 图1，线材和分条带材之间的差异 Slitting operations will impart cold work and residualstress to the edges of the strip. These stresses can create problems such asdie exit twist or camber when the strip is stamped. If the width to thicknessratio is less than 5:1, strip may even show shape problems before stamping,since the residual slitting stresses will be present across a substantialportion of the cross section. These stresses will be compounded by the residualstresses induced by forming operations, unless the final processing step is aheat treatment to stress relieve or age harden the material. 分条操作将带来额外的冷加工和产生残余应力。这些应力会在冲压带材是产生不良影响，例如模具出口发生扭折或蛇形弯。如果宽/厚比小于5/1，由于较高的残余应力比例，带材有可能在冲压前就出现形状的问题。伴随着后续冲压加工，零件内应力会交织复合在一起。除非最终的加工步骤是对材料进行去应力退火或者时效。 Round wire is drawn to the proper gauge, and flatwire may be drawn or rolled from the top, bottom, and sides to the proper widthand thickness. In either case, there is no slitting involved. This means thatwire will not have the residual stresses from slitting that are present instrip. Since the residual stresses can negatively impact the performance ofelectrical contacts, wire may offer a slight advantage. However, any formingoperations performed on the wire to shape it into the contact will also createresidual stress. There will always be some residual stress present, unless thestress is relieved by heat treatment. 将线材拉拔至适当的规格，或是从不同方向将扁钢轧制至适当的宽度和厚度。这两种情况下，都不涉及剪切，也就意味线材中不会产生类似带材中的纵向残余应力。由于残余应力会对电触点的性能产生负面影响，因此线材在这方面比线材表现略优。然而，对线材进行的任何加工也会带来残余应力。除非通过热处理消除，否则总会存在一些残余应力的。 Wire and strip are processed differently. One consequenceis that equivalent alloys and tempers can show completely different propertiesin strip and in wire. For example, 1/4 hard (H01 temper) C26000 brass wire hasa 57 ksi yield strength, a 70 ksi tensile strength, and a 20% elongation. Instrip form, 1/4 hard (H01 temper) C26000 brass has a 40 ksi yield strength, a54 ksi tensile strength, and 43% elongation. This discrepancy comes from thedefinition of H01 temper as being a 10.9% reduction in strip thickness or wirediameter. The true strain associated with these reductions is twice asmuch in round wire as in the rectangular strip, so 1/4 hard wire has undergonetwice as much strain hardening as 1/4 hard strip. Not only are materialproperties dependent upon the alloy and temper, they are also dependent on theproduct form! Therefore, in order to properly specify a material on a print,the designer has to name the alloy, temper, and product form (if it is notobviously an application for strip or wire.) It is certainly not enough tospecify merely “brass”, “phosphor bronze”, or “beryllium copper” on a print.Unfortunately, the author has seen many prints where this is done. 线材和带材的加工方式不同，带来的影响是标注一样的回火状态可能在线材和带材中表现出完全不同的性能。例如1/4H (H01态) C26000黄铜线的屈服强度为57 ksi，抗拉强度为70 ksi，伸长率为20%。在对应的带材中，1/4H（H01态）C26000黄铜的屈服强度为40 ksi，抗拉强度为54 ksi，伸长率为43%。这种差异的来源是对于H01的定义，H01定义是片材的厚度或者线材的直径减少10.9%。对于线材而言，直径减少10.9%需要经历两倍于片材的加工量。所以说，材料性能不仅仅取决于合金种类和回火态，还取决于产品的形式。正确的选择一种材料，需要工程师标注正确的合金、回火态和产品形式，而不是仅仅写“黄铜”、“磷青铜”或者“铍铜”。 Strip offers several advantages over wire, includinggreater design flexibility and a generally lower cost in large widths. However,there are some applications where wire will perform better, especially whennarrow, regular cross sections are required. Wire will show lower residualstresses and will have a better shaped edge than strip. Strip and wire aprocessed differently, so they cannot be directly substituted for one another.Product form can be equally important in determining properties as alloy andtemper. 综上，线材和带材各有优势。带材具有很更大的设计灵活性和大宽幅下更优的成本优势。而线材对于要求窄而规则的应用场景更为适合。线材具有更低的加工残余应力和更优的边缘形貌。带材和线材加工方式不同，不能简单的直接相互替代。在决定合金和回火态时，确定产品的形式也十分重要。 请联系美题隆高性能材料事业部（PM）获取更多信息。 |
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