压铸过程原理
发布时间：2020-05-25 17:01
<p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压铸的主要特点是金属液在高压、高速下充填压铸模型腔，并在高压下成型、 结晶。因此，压铸过程中压力和速度的变化及其作用是至关重要的，它们直接影 响金属充填形态和金属液在型腔中的运动，从而影响压铸件的质量。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 18px; color: rgb(123, 12, 0);">第一节 压铸压力</span></strong></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 18px; color: rgb(123, 12, 0);"><br/></span></strong></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压铸压力是压铸工艺中的主要参数之一。压铸过程中的压力是由压铸机的 压射机构产生的，压射机构通过工作液体将压力传递给压射活塞，然后由压射活 塞经压射冲头施加于压室内的金属液上。 </span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">作用于金属液上的压力是获得组织致密和轮廓清晰的铸件的主要因素，所 以，必须了解并掌握压铸过程中作用在金属液上的压力的变化情况，以便正确利 用压铸过程中各阶段的压力，并合理选择压力的数值。</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压铸过程中的压力可以用压射力和压射压力两种形式来表示。压铸机压射缸内的工作液作用于压射冲头，使其推动金属液充填模具型腔的 力称为压射力。其大小随压铸机的规格而不同，它反映了压铸机功率的大小。 </span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压射压力是指压射过程中，压室内单位面积上金属液所受到的静压力。压射力和压射压力的关系如下：</span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; max-width: 100%; clear: both; min-height: 1em; color: rgb(51, 51, 51); font-family: -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; white-space: normal; background-color: rgb(255, 255, 255); line-height: 1.75em; box-sizing: border-box !important; overflow-wrap: break-word !important;"><br/></p><p><section></section><section></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">由式（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY13; color: rgb(0, 0, 0);">2-1</span>）可知，压射压力与压射力成正比，而与压射冲头的截面积成反比。所以，压射压力可以通过调整压射力和更换不同直径的压射冲头来实现。<br/></span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">如果既考虑压射力又考虑压射压力，会把问题复杂化，而且压射压力更能反 映压铸过程中金属液在充填时的各个阶段以及金属液流经各个不同截面时的力 的概念，因此，压铸压力通常指的是压射压力。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">在压铸过程中，作用在金属液上的压射压力并不是一个常数，而是随着压射 阶段的变化而改变。金属液在压室与压铸模型腔中的运动可分解为四个阶段，图 <span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY13; color: rgb(0, 0, 0);">2-1</span>表示在不同阶段压射冲头的运动速度与金属液所受的压力（压射压力）曲线。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">第一阶段τ1压射冲头以慢速 <span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY12; box-sizing: border-box !important; overflow-wrap: break-word !important;">v1</span><span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY13; box-sizing: border-box !important; overflow-wrap: break-word !important;"> </span>前进，封住浇口，金属液被推动，其所受压力p1 也较低，此时p1仅用于克服压室与液压缸对运动活塞的摩擦阻力。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4Trgicx6yJwzQsepUmClmfjAlVtvxALiboZWg3c8ANvpoDicibrekeZmVFobg/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">第二阶段τ2本阶段在压射冲头作用下，金属液将完全充满压室至浇口处的<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0);">空间，压射冲头的速度达到v2，压力 <span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY12;">p2</span></span><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY13; color: rgb(0, 0, 0);"> </span><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0);">也由于压室中金属液的反作用而超过p1。</span></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">第三阶段<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;">τ3</span><span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY16; box-sizing: border-box !important; overflow-wrap: break-word !important;"> </span>金属液充填浇注系统和压铸模型腔，因为内浇口面积急剧缩 小，故使金属液流动速度v3下降，但压力则上升至p3，在第三阶段结束前，金属液因压射机构的惯性关系，而发生水锤作用，使压力增高，并发生波动，待波动消失之后，即开始压铸的第四阶段。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">第四阶段τ4本阶段的主要任务是建立最后的增压，使铸件在压力p4下凝固，而达到使铸件致密的目的。所需最终压力 <span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY17; box-sizing: border-box !important; overflow-wrap: break-word !important;">p4</span><span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY16; box-sizing: border-box !important; overflow-wrap: break-word !important;"> </span>的大小与合金的种类、状态（黏度、密度）和对铸件的质量要求有关。p4一般为 <span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY16; box-sizing: border-box !important; overflow-wrap: break-word !important;">50-500MPa</span>。如果在最终压力达 到时，浇注系统中的金属仍处于液态或半固态，则压力p4将传给凝固中的铸件， 缩小铸件中的缩孔、气泡，改善铸件表面质量（特别是在半固态压铸时）。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">上述过程称为四级压射。根据工艺要求，压铸机均应实现四级压射。目前使 用的大中型压铸机为四级压射，中小型压铸机多为三级压射，这种机构是把四级 压射中的第二和第三阶段合为一个阶段。从τ1~τ4为一个压铸周期，其中 <span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY17; box-sizing: border-box !important; overflow-wrap: break-word !important;">p3</span><span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY16; box-sizing: border-box !important; overflow-wrap: break-word !important;"> </span>愈 高所得的充填速度愈高，而p4 愈大，则愈易获得外廓清晰、组织致密和表面粗糙 度要求高的铸件。在整个过程中p3 和p4 是最重要的。所以，在压铸过程中压力的主要作用在一定程度上是为了获得速度，保证液态金属的流动性。但要达到这 一目的，必须具备以下条件：</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY16; box-sizing: border-box !important; overflow-wrap: break-word !important;">1</span>）铸件和内浇口应具有适当的厚度；</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY16; box-sizing: border-box !important; overflow-wrap: break-word !important;">2</span>）具有相当厚度的余料和足够的压射力，否则效果不好。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">上述压力和速度的变化曲线只是理论性的，实际上液态金属充填型腔时，因铸件复杂程度不同，金属充填特性及操作不同等因素，压射曲线也会出现不同的形式。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(123, 12, 0); font-size: 18px;">第二节 压铸速度</span></strong></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">压铸中，压铸速度有压射速度和充填速度两个不同的概念。压射速度是指压铸机压射缸内的压力油推动压射冲头前进的线速度。充填速度是指金属液在压 力作用下，通过内浇口进入型腔的线速度。充填速度的主要作用是将金属液在凝 固之前迅速输入型腔，它是获得轮廓清晰、表面质量高的铸件的重要因素。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">速度和压力是密切相关的两个工艺参数，因此除有适当的压射压力外，还必 须正确地选择速度。充填速度确定的依据是合金的特性和铸件的结构特点。当 充填速度较低时，会使铸件轮廓不清，甚至不能成型。当充填速度较高时，即使采 用较低的压射压力也可以获得表面质量高的铸件。但是过高的充填速度会引起 许多工艺上的缺点，造成不利的压铸条件，主要有以下几点。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY18; box-sizing: border-box !important; overflow-wrap: break-word !important;">1</span>）裹住空气形成气泡。由于高速金属液流到空气的前面，堵塞排气通道，所 以，空气被裹在型腔内。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY18; box-sizing: border-box !important; overflow-wrap: break-word !important;">2</span>）金属液呈雾状进入型腔，黏附于型壁上，随后进入的金属液不能与它熔合 而形成表面缺陷（冷豆或冷隔），降低铸件表面质量。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY18; box-sizing: border-box !important; overflow-wrap: break-word !important;">3</span>）高速金属流产生漩涡，裹住空气和最先进入型腔的冷金属，使铸件产生气 孔和氧化夹杂。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; font-family: DY18; box-sizing: border-box !important; overflow-wrap: break-word !important;">4</span>）高速金属流冲刷型壁，加速压铸模的磨损。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">在冷室压铸机中，压室、浇道和压铸模型腔相连，成为一个密闭系统，因而它 们之间具有连续方程的关系，即</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrKhFdRzsXJEuSbAENqC0YUKc54G6oId65vt9VYcDkuWmTpLLCVQ3YgQ/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">由于压射速度与充填速度有式（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY18; color: rgb(0, 0, 0);">2-2</span>）与式（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-family: DY18;">2-2</span>）的关系，确定了充填速度， 就能很方便地求出压射速度，而且充填速度更能反映压铸的工艺特性，因此，压铸 速度通常指的是充填速度。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">由式（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY21; color: rgb(0, 0, 0);">2-3</span>）可知，金属液充填压铸模型腔的线速度与压室直径的平方、冲头 的压射速度成正比，而与内浇口的截面积成反比。因此，可以通过改变上述三因 素的数值来调整充填速度。其中压室直径的变化可以较显著地改变充填速度；与 此同时，压射压力的数值也会随同变化。通过变化内浇口的截面积来调整充填速 度是不太方便的，这是由于当内浇口的截面积、位置确定后，其所能调整的范围很小，对金属液充填速度影响不显著。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压射速度的调节可通过调整压铸机上的压力控制阀来实现。在生产中，应根 据具体条件去确定调整因素。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">此外，充填速度和压射压力有关，根据水力学原理，压射压力与充填速度间的 关系可用下式来表示，即</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrOeNNPVlPuBz2jUyMBuhzYev3kLqKibgehtEibMLrI16u81JaL72rTgjw/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">因为金属液是黏性液体，它在流经浇注系统时，会因摩擦而引起动能损失，故 上式应改写为</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4Tr5C2SaIfRNUaFxrXa2MzexFP7pkuJQicf3UgO3uv6WBNGNK6rO2wCd2Q/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">由此可见，充填速度与压射压力的平方根成正比，而与金属液密度的平方根成反比。因此，压射压力大，充填速度就高；金属液密度大，充填速度就低。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">由上面的分析得知，影响充填速度的因素有三个，即压射速度、压射压力和内 浇口截面积。因此，生产中通常采用的调整充填速度的方法是：调整压射速度、改 变压射压力、调整内浇口的截面积。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">总之，压力和速度是相辅相成而又相互制约的两个基本参数。为适应各种铸 件对压铸工艺不同的要求，压铸压力和压铸速度都应做到无级调整。一般压铸压 力高时，铸件质量就较好。为使压力更好地完成“充填”、“成型”和“压实”的任务， 在制定压铸工艺时，必须充分考虑各因素之间的影响。</span></section><section><br/></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(123, 12, 0); font-size: 18px;">第三节 金属充填铸型的形态</span></strong></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压铸过程中金属液充填压铸模型腔的形态与铸件的质量（致密度、气孔、力学 性能、表面粗糙度等）有着很大的关系，长期以来，人们对此进行了广泛的研究。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">在压铸过程中，金属液充填压铸模型腔的时间极短，一般为百分之几或千分 之几秒，在这一瞬间内，金属液的充填形态是极其复杂的。它与铸件结构、压射速 度、压力、压铸模温度、金属液温度、金属液黏度、浇注系统的形状和尺寸大小等都有着密切的关系。因而金属液充填形态对铸件质量起着决定性的作用，为此，必 须掌握金属液充填形态的规律，了解充填特性，以便正确地设计浇注系统，获得优质铸件。</span></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">一、金属充填理论</span></strong><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">金属液充填压铸模型腔的过程是一个非常复杂的过程，它涉及流体力学和热 力学的一些理论问题。研究充填理论的目的在于运用这些理论以更好地指导我 们选择合理的工艺方案和工艺参数，从而消除压铸生产中出现的各种缺陷，以获 得优质的压铸件。充填过程主要有以下三种现象。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY26; color: rgb(0, 0, 0);">1</span>）压入 压射系统有必需的能量，对注入压室内的金属液，施加高压力和高速度使熔液经压铸模的浇口流向型腔。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY27; color: rgb(0, 0, 0);">2</span>）金属液流动 熔液从内浇口注入型腔，而后熔液流动并充填型腔的各个 角落，以获得形状完整、轮廓清晰的铸件。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY27; color: rgb(0, 0, 0);">3</span>）冷却凝固 熔液充填型腔后，冷却凝固，此现象在充填过程中自始至终地 进行着，必须在完全凝固前充满型腔各个角落。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">为了探明压铸时，液态金属充填型腔的真实情况，许多压铸工作者进行了一 系列的试验研究工作，提出了各种充填理论。国内外压铸工作者对金属液充填形 态提出的各种不同观点归纳起来有三种：喷射充填理论、全壁厚充填理论、三阶段 充填理论。</span></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（一）喷射充填理论</span></strong><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">这是最早提出的一种金属充填理论，它是由弗洛梅尔（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY27; color: rgb(0, 0, 0);">L.Frommer</span>）于1932年 根据锌合金压铸的实际经验并通过大量实验而得出的。实验铸型是一个在一端 开设浇口的矩形截面型腔。通过研究，认为金属液的充填过程可以分为两个阶段，即冲击阶段和涡流阶段。在速度、压力均保持不变的条件下，金属液进入内浇 口后仍保持内浇口截面的形状冲击到对面的型壁（冲击阶段）。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">随后，由于对面型 壁的阻碍，金属液呈涡流状态，向着内浇口一端反向充填（涡流阶段），这时由于铸 型侧壁对此回流金属流的摩擦阻力，以及此金属流动过程中温度降低所形成的黏 度迅速增高，因而使此回流金属流的流速减慢。与此同时，一部分金属液积聚在 型腔中部，导致液流中心部分的速度大于靠近型壁处的速度。图2-2所示为金 属液在型腔内的充填形态。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">大量的实验证实，这一充填理论适用于具有缝形浇口的长方形铸件或具有大 的充填速度以及薄的内浇口的铸件。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">根据这一理论，金属液充填铸型的特性与内浇口截面积Ag<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY28; color: rgb(0, 0, 0);"> </span>和型腔截面积A1的比值有关，压铸过程中应采用Ag/A1>（1/4~1/3），以控制金属液的进入速度， 从而保持平稳充填。在此情况下，应在内浇口附近开设排气槽，使型腔内的气体能顺利排除。</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4Trq5Ju8dPW9TFUrE3fY1fAiaKI98kQ9be3icY4ibJSfkabUMJjEW3FzVhjQ/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（二）全壁厚充填理论</span></strong><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">该理论是由布兰特（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY29; color: rgb(0, 0, 0);">W.G.Brandt</span>）于1937年用铝合金压入试验性的压铸型中 得出的。实验铸型具有不同厚度0.5~2mm的内浇口和不同厚度的矩形截面型腔。内浇口截面积与型腔截面积之比Ag/A1<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY29; color: rgb(0, 0, 0);"> </span>在0.1~0.6的范围内，用短路接触器测定金属液在型腔内的充填轨迹。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">该理论的结论如下。</span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY29; color: rgb(0, 0, 0);">1</span>）金属液通过内浇口进入型腔后，即扩展至型壁，然后沿整个型腔截面向前 充填，直到整个型腔充满金属液为止。其充填形态如图2-3所示。</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrSKeicsEJDTNyG4I74NzdGNO1gCpF1pjPCl72IrV6j4MUvzXPlo1Q4Iw/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY29; color: rgb(0, 0, 0);">2</span>）在整个充填过程中不出现涡流状态，在实验中没有发现金属堆积在型腔 远端的任一实例，凡是远端有欠铸的铸件，在浇口附近反而完全填实。因此认为 喷射充填理论是不符合实际情况的，并且推翻了喷射充填理论所提出的将复杂铸 件看成若干个连续矩形型腔的说法。同时认为，无论Ag/A1的值大于或小于1/4~1/3，其结果并无区别。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">按这种理论，金属的充填是由后向前的，流动中不产生涡流，型腔中的空气可 以得到充分的排除。至于充填到最后，在进口处所形成的“死区”，完全符合液体 由孔流经导管的水力学现象。</span></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（三）三阶段充填理论</span></strong><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">此充填理论是巴顿（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY31; color: rgb(0, 0, 0);">H.K.Barton</span>）于1944~1952<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY31; color: rgb(0, 0, 0);"> </span>年提出的。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">按三阶段充填理论所做的局部充填试验表明，其充填过程具有三个阶段，如 图2-4所示。</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrpQ8TXeSBQGn6Gia1MaiaH8N1ZBG2nicYJIibze2xOP7ic8Qc0KribNt18dNw/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">第一阶段 金属液射入型腔与型壁相撞后，就相反于内浇口或沿着型腔表面 散开，在型腔转角处，由于金属液积聚而产生涡流，在正常均匀热传导下，与型腔 接触部分形成一层凝固壳，即为铸件的表层，又称为薄壳层。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">第二阶段 在铸件表层形成壳后，金属液继续充填铸型，当第二阶段结束时， 型腔完全充满，此时，在型腔的截面上，金属液具有不同的黏度，其最外层已接近 于固相线温度，而中间部分黏度很小，还处于液态。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">第三阶段 金属液完全充满型腔后，型腔、浇注系统和压室是一个封闭的水 力学系统，在这一系统中各处压力是相等的，压射力通过铸件中心还处于液态的 金属继续作用。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">在实际生产中，大多数铸件（型腔）的形状比充填理论试验的型腔要复杂得 多。通过对各种不同类型压铸件的缺陷分析和对铸件表面流痕的观察可知，金属 在型腔中的充填形态并不是由单一因素所能决定的。例如，在同一铸件上，由于 工艺参数的变动，也会引起充填形态的改变；在同一铸件上，由于其各部位结构形 式的差异，亦可能产生不同的充填形态。至于采取哪种形态，则是由金属流经型腔部位的当时条件而定。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">上述三种充填理论，在不同的工艺条件下都有其实际存在的可能性，其中全 壁厚充填理论所提出的充填形态是最理想的。</span></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（四）理想充填形态在三级压射中的获得</span></strong><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">压铸件的气孔、冷隔、流痕等缺陷都是由于金属充填型腔时产生的涡流和裹 气所引起的。涡流和裹气现象的产生又是金属液高速射向型壁或两股金属流相 对碰撞的结果。因此，理想充填形态的获得，应保证在金属液充满型腔的条件下， 以最低的充填速度及浇注温度，使金属流形成与型腔基本一致的金属液柱，从一 端顺利地充满型腔，排出气体。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">但这一形态的获得，即使在适宜的浇注系统中使金属液起到较完善的整流和 定向作用，若没有其他工艺条件的配合，亦难达到充填过程中各阶段的要求。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">三级压射速度的定点压射是改善充填形态的有效方法。所谓三级压射速度 定点压射是指压射缸在压射过程中，按充填各阶段的要求，分为三级压射速度，每 一级压射的始终位置均有严格的控制。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">在第一级压射时，压射冲头以较慢的速度推进，以利于将压室中的气体挤出， 直至金属液即将充满压室为止。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">第二级压射则是按铸件的结构、壁厚选择适当的流速，以在充满型腔过程中 金属液不凝固为原则，将糊状金属把型腔基本充满。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">第三级压射是在金属液充满型腔的瞬间以高速高压施加于金属液上，增压后 使铸件在压力的作用下凝固，以获得轮廓清晰、表面质量高、内部组织致密的优质铸件。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">由上述充填过程可知，三级压射可避免一般充填中所发生的裹气和涡流现 象。在第二级压射中，金属液流进内浇口后，温度有所下降，黏度相应提高；同时， 金属液在流人型腔后因容积突然增大，向外扩张，当金属液接触到型壁后，金属液 流随型腔而改变形状，此时由于金属液对型壁有黏附性，更使它的流动性降低。这样，在型腔表面形成一层极薄的表皮，随后按金属流向逐步充填铸型。因此，在适当的铸型温度及金属液温度下，第二级压射形成了金属流端部的金属柱后，即 使再增加压射速度，亦不致有产生涡流的危害。所以，第二种充填形态的获得有 利于避免气孔，特别对厚壁铸件功效更大。</span></section><section><br/></section><section><strong style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">（五）金属液在型腔中的几种充填形态</span></strong><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"></span></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">图2-5所示为在某一压力下金属的充填形态。当改变内浇口截面积与铸件 截面积之比时，充填所需的时间也不同，当Ag/A1=1/3时，充填所需时间最短。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">图2-6所示为在一般压力下，内浇口在型腔一侧时的充填形态。</span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;"><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0);">图<span style="margin: 0px; padding: 0px; max-width: 100%; text-align: left; font-family: DY33; box-sizing: border-box !important; overflow-wrap: break-word !important;">2-7</span></span>所示为型腔特别薄时（对锌合金可以薄到0.4mm）的充填形态。金属 流厚度接近于型腔，故金属流入型腔后，即与型腔的一侧或两侧接触［见图2-7（a）、（b）］。与型腔接触的金属因冷却而温度降低，中间的金属从冷凝金属层 <span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY33; color: rgb(0, 0, 0);">& </span>上 面滑过去，又与前方的型腔壁接触，而新的金属液 <span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY33; color: rgb(0, 0, 0);">! </span>从两侧逐渐冷却凝固的金属 层中通过［见图 <span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY33; color: rgb(0, 0, 0);">2-7</span>（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-family: DY33;">c</span>）、（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-family: DY33;">d</span>）］。</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrdAf70nI5AVGkDINibf6mlkUULfIfXz0D5By5KYj2vaJDBkXKAGGibxrA/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">图2-8<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY33; color: rgb(0, 0, 0);"> </span>所示为金属流在型腔转角处的充填形态。金属液流入型腔转角处会产生 涡流［见图2-8（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-family: DY33;">b</span>）］，基本上没有向前流动的速度，在型腔垂直部分充满以前向左移动 甚慢［见图2-8（<span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; color: rgb(0, 0, 0); font-family: DY33;">c</span>）］，在垂直部分充满以后，后面的金属推动前面的金属向左流动［见 图 <span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-family: DY33; color: rgb(0, 0, 0);">2-8</span>（d）］。<br/></span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; font-size: 16px;">图2-9所示为型腔表面是一圆弧面时的金属充填形态。金属液有靠近外壁 流动的趋势，因此，靠近内壁处的空气无法排出，易产生缺陷。</span></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4Tr1BFS6Hqjic38BA4SAorztrtokobWAQG47mYiar1Lqia2BicdU12AyFgzpQ/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrdWzO4E1RiaRyZCictvIauYNQEXPRwbVehyJeFQLxFQwWicOfEdq8EmKpg/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrVVoYOhaF9oJibwRtsUEkNVH7vZZEoWUv6bBeEgwRV77XzvcIE5iaqn2Q/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section><section><br/></section><section><img class="rich_pages " src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaaicYgtcukborCYia1mQibI4TrzmsUgWnmC80Vwg2PO9jlvicsw4fm4hqicaXib4ic4CmYJPYkNyCEqepOHQ/640?wx_fmt=png&tp=webp&wxfrom=5&wx_lazy=1&wx_co=1"/></section></p><p><br/></p>
