涂料的作用与分类
发布时间：2020-04-16 11:26
<p style="margin: 0pt 0pt 10pt; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; text-indent: 0em; white-space: normal; line-height: 1.75em;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">涂料的主要作用是防止铸件粘砂。为了使配制的涂料能有效地防止铸件粘砂，首先要了解铸件粘砂形成机理。</span></p><p style="margin: 0pt 0pt 0px; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; text-indent: 0em; white-space: normal; break-after: avoid; line-height: 1.75em;"><span style="margin: 0px; padding: 0px; color: rgb(123, 12, 0);"><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; font-size: 18px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1.1</span><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">铸件粘砂形成机理</span></span></strong></span></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; white-space: normal;"><br/></p><p style="margin: 0pt; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; text-indent: 0em; white-space: normal; line-height: 1.75em;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">粘砂是一种铸件缺陷。它表现为铸件部分或整个表面上夹持 有型、芯砂或者粘附一层难于清除的低熔点物质。粘砂使铸件花 费较多清理工时甚至根本无法清理，使切削加工刀具磨损增加， 影响某些机器的正常工作效率和外观。</span></p><p><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">根据粘砂形成的原因，一般可将粘砂分为机械粘砂和化学粘砂。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">机械粘砂又称渗透粘砂，它是由于液体金属渗入型、芯表面 的孔隙而形成的。液态金属渗入深度大于砂粒半径时，凝固后这 些砂粒与铸件牢固地联接在一起。这种粘砂叫做机械粘砂。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">化学粘砂是由于金属氧化物与型、芯砂中的某些成分发生化 学反应，形成一种低熔点的化合物，并且这种低熔点化合物牢固 地粘附在铸件上形成难以清除的粘砂层。这种粘砂叫做化学粘砂。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">在实际铸件生产中，许多情况下观察到的粘砂都是综合性的，既是机械粘砂又是化学粘砂。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 16px;"><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; color: rgb(123, 12, 0);"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1.1.1 </span><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">机械粘砂形成机理</span></span></strong></span></section><section><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(123, 12, 0);"><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><br/></span></span></strong></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">机械粘砂是高温液体金属渗入铸型孔隙中形成的。渗入液体 金属越多、越深，机械粘砂越严重。从机械粘砂形成来看，必 定有一种力促使液体金属渗入砂型孔隙中去，也必定有一种力阻 止铁水渗入砂型孔隙中去。这两种力的对比和变化，决定了铸件 产生机械粘砂的倾向。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(123, 12, 0);"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">(1) </span><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">渗透动力</span></span></strong></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">即促使金属液渗入砂型孔隙的力，这主要是金属液对铸型的</span> <span style="margin: 0px; padding: 0px;">动压力和静压力。动压力和静压力越大，金属液越易渗入砂型孔</span><span style="margin: 0px; padding: 0px;">隙</span>.因此，高大铸件的下部，易形成机械粘砂。但是金属液的渗 入深度并不与金属液的压力完全成正比，因为金属液渗入砂型孔 隙中要散失热量，逐渐凝固而失去流动能力<span style="margin: 0px; padding: 0px;">浇注温度越高，铸</span> <span style="margin: 0px; padding: 0px;">件壁越厚，砂型的导热性越差，</span>则金属液的流动能力越强，流动时间越长，渗透越深，粘砂越严重。因此金属液的渗透动力还受到浇注温度、铸件壁厚、砂型导热性的限制。</span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">在铸件热节处的型芯以及被金属液包围的芯子最易产生较严</span><span style="margin: 0px; padding: 0px;">重的机械粘砂。这是因为这些部位的型芯散热条件差、被金属液</span> <span style="margin: 0px; padding: 0px;">加热到较高的温度，因而金属液长期处于可流动状态，渗入型芯</span> <span style="margin: 0px; padding: 0px;">深度大，机械粘砂加剧。型芯表面被金属液加热而达到的温度，</span> <span style="margin: 0px; padding: 0px;">还取决于铸型材料的冷却能力，即取决于蓄热系数，因此釆用</span><span style="margin: 0px; padding: 0px;">蓄热系数大的材料能减少铸型与液态金属的接触时间，也就减少</span> <span style="margin: 0px; padding: 0px;">了液态金属渗入铸型表面的时间。根据这一点，一些人认为错</span><span style="margin: 0px; padding: 0px;">砂、铭铁矿砂能消除机械粘砂并改善铸件表面光洁度是因为它们</span><span style="margin: 0px; padding: 0px;">有较高的蓄热能力。</span></span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; font-size: 14px; letter-spacing: 0pt; text-indent: 0em;">在生产钢铸件时，采用加金属微粉(铁及铁合金粉)的悬浮 浇注法能明显减少粘砂缺陷。</span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; font-size: 14px; letter-spacing: 0pt; text-indent: 0em;">这是因为金属微粉的加入降低了浇注温度和金属液的液态流动性。</span></section><section><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; font-size: 14px; letter-spacing: 0pt; text-indent: 0em;"><br/></span></section><section><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(123, 12, 0);"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">(2) </span><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">渗透阻力</span></span></strong><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(123, 12, 0);"><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"></span></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">即阻止金属液渗入砂型孔隙的能力。这方面主要有两种力， 一是砂型孔隙的阻力，另一是砂型孔隙中的气体压力(通称背压)。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">砂型孔隙的阻力取决于砂型孔隙大小</span><span style="margin: 0px; padding: 0px;">砂型孔隙越小，阻力</span><span style="margin: 0px; padding: 0px;">越大，金属液难以渗入。孔隙大小又取决于砂的颗粒组成、紧实</span><span style="margin: 0px; padding: 0px;">程度以及浇注和凝固过程中界面的物理化学反应过程。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;"><br/></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">有的学者给出了砂型孔隙大小与发生粘砂时的金属液高度的</span><span style="margin: 0px; padding: 0px;">关系式。假定将金属液渗透过程简化为如图</span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1-1</span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">所示的模型。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><br/></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">液体充满一圆筒，圆筒下部有一直径为</span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">D</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">的小孔。若液柱高力</span><span style="margin: 0px; padding: 0px;">不变，当小孔直径</span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">D</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">小到一定程度时，液体将不会从小孔流</span> <span style="margin: 0px; padding: 0px;">出。此时小孔直径</span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">Z</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">)<span style="margin: 0px; padding: 0px;">和液柱高要满足如下关系式：</span></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;"><br/></span></span></span></section><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0sXNYOLS6OW6jxeLw9WkYdstP0yalMDdr9wMLInsl9xznNrtjtEUzugg/640?wx_fmt=png"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">在上式中金属表面张力为一定值。</span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; letter-spacing: 0px;">当铸件的液柱高增大时,</span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; letter-spacing: 0px; text-align: justify;">砂粒孔隙直径必须减小才能保证液体金属不渗入铸型，因此为了减轻粘砂，大多数学者建议在粗砂粒中加入细砂粒或采用粒度分散的砂子。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; letter-spacing: 0px; text-align: justify;"><br/></span></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">型砂的紧实程度对孔隙大小也有很大影响，当提高铸型的压实压力时，可有效地减少金属液的渗入。因此高压造型是防止机械粘砂有效措施之一。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">金属与铸型界面上的物理化学作用如型砂烧结而致砂粒间隙增大，也会增大金属渗入深度。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">另一种渗透阻力是砂型中孔隙的气体压力。它阻止金属液渗入孔隙。当砂型受到金属液的热作用后，型砂中的水分、有机物 及某些矿物发生气化、燃烧、升华或分解等作用，产生大量气 体。这些气体不能全部及时逸岀，一部分留在孔隙中，形成较大 压力，阻止金属液的渗入「气体的背压决定于型砂的发气性和透气性，发气性大、透气性小，背压就大，金属液较难渗入。但是若采取这种措施来防止机械粘砂有增加铸件形成气孔的危险，必须加以注意。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; color: rgb(123, 12, 0);"><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">(1) </span><span style="margin: 0px; padding: 0px; letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">砂型毛细力</span></span></strong></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">这种力对机械粘砂的影响比较复杂，有时它是渗透动力，有 时它是渗透阻力。关键在于金属液是否润湿砂型以及润湿的程度。</span></section><section><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; letter-spacing: 0px; font-family: "Times New Roman";"><br/></span></span></section><section><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; letter-spacing: 0px; font-family: 宋体;">在研究机械粘砂时，可以</span><span style="margin: 0px; padding: 0px; letter-spacing: 0px; font-family: 宋体;">将砂型中砂粒间的孔隙近似地看作毛</span></span><span style="margin: 0px; padding: 0px; font-size: 14px; text-indent: 0em; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">细管。铁液在非氧化性气氛中对型砂是不润湿的，好像水银在玻璃细管中一样呈拱形，毛细力阻止铁液渗入砂型，如图1</span><span style="margin: 0px; padding: 0px; font-size: 14px; text-indent: 0em; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">-2(a) </span><span style="margin: 0px; padding: 0px; font-size: 14px; text-indent: 0em; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">所示。不润湿性越大，从孔隙中退出的力就越大。铁液处在氧化 性气氛中，铁液表面被氧化产生大量氧化铁，氧化铁能够润湿型砂，如同水在坡璃细管中一样，成为促使铁液渗入砂型孔隙中的 动力，如图</span><span style="margin: 0px; padding: 0px; font-size: 14px; text-indent: 0em; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">1-20)</span><span style="margin: 0px; padding: 0px; font-size: 14px; text-indent: 0em; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">所示。润湿性越大，渗入越深，粘砂越严重。</span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; text-indent: 0em; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"></span></span></section><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0sE46e1sASF8beFLFZnxXxLmibeTknVBzSvZ31LycP0sSzMt1fw422bHg/640?wx_fmt=png"/></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">不氧化的金属液不润湿铸型表面，此时毛细力也是渗透阻力。毛细力可由下式求出：</span></section></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; white-space: normal;"><br/></p><p><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0sPibUJb7exAcrBG82y3FwBAsfmYnEfzHpB0nMAQ4oPd2TapCnGAGzgOA/640?wx_fmt=png"/></section></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; white-space: normal;"><br/></p><p><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">润湿角反映了液体在固体表面上的润湿程度。润湿角可用图</span> </span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1-3</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">表示。当液体、固体、气体三相接触达到平衡时，从三相</span><span style="margin: 0px; padding: 0px;">接触点（图</span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1-3</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">中的O点）沿液气表面作切线，此切线和固</span><span style="margin: 0px; padding: 0px;">液界面的夹角<span style="margin: 0px; padding: 0px;">θ</span></span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">（</span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">夹有液体）即叫润湿角，又称接触角。当θ</span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><90° </span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">时，我们称物体被润湿（如水润湿玻璃），角愈小，润湿性能</span><span style="margin: 0px; padding: 0px;">愈好，铺展性也愈好。当<span style="margin: 0px; padding: 0px;">θ</span></span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">>90°</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">时，我们称物体不润湿（如水</span> <span style="margin: 0px; padding: 0px;">不润湿石蜡），</span></span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><span style="margin: 0px; padding: 0px;">θ</span>角愈大，润湿性能愈差，铺展性也愈差。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><br/></span></span></section><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0s5S2B5Picp4zYq1RfKCezOIKRwRMbDaUwLC9nf2lDbtcb07ibCRrslKjw/640?wx_fmt=png"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">润湿性除了取决于金属液和铸型两种材料的结构和性质外，</span> <span style="margin: 0px; padding: 0px;">还和它们所处的气氛环境有关。例如在氧化性（空气）、弱氧化</span><span style="margin: 0px; padding: 0px;">性（氮气加体积分数为</span></span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">0.5%</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">的氧气）和中性（氮气）气氛中，</span> <span style="margin: 0px; padding: 0px;">工业纯铁对于硅砂的润湿角<span style="margin: 0px; padding: 0px;">θ</span>分别为</span></span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">52°</span><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">、</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">83°</span><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">和</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">110°,</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">而工业</span> <span style="margin: 0px; padding: 0px;">纯铁对镁砂的润湿角<span style="margin: 0px; padding: 0px;">θ</span></span></span><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">分别为</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">92°, 107°</span><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">和</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">113</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">°。由此可见在氧化性气氛中，钢铁铸件在硅砂型中比在镁砂型中容易产生机械粘砂。钢铁铸件在石英砂型中，当氧化性气氛和弱氧化性气氛<span style="margin: 0px; padding: 0px;">时</span>,<span style="margin: 0px; padding: 0px;">润湿角皆<span style="margin: 0px; padding: 0px;">θ</span></span></span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px; font-size: 14px;"><90 C </span><span style="margin: 0px; padding: 0px; font-size: 11.6667px;">。</span></span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">说明这两种气氛下容易产生机械粘砂，</span> <span style="margin: 0px; padding: 0px;">而处于中性气氛时，则不容易产生机械粘砂。钢铁铸件在镁砂型</span> <span style="margin: 0px; padding: 0px;">中，无论在什么气氛中，润湿角皆<span style="margin: 0px; padding: 0px;">θ</span>〉</span></span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">90 °</span><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">说明是不润湿的，</span> <span style="margin: 0px; padding: 0px;">都不容易产生机械粘砂。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;"><br/></span></span></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">综上所述，可将影响机械粘砂的因素总结如下：</span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">如果砂粒粗大，砂粒间隙大，则容易产生机械粘砂；</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">2<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">如果粗砂粒中附加细砂粒或石英粉末，则砂粒间隙变小，</span> <span style="margin: 0px; padding: 0px;">不易产生机械粘砂；</span>'</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">3<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">如果铸型被充分紧实，则砂粒间隙变小</span>,不易产生机械粘砂；</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">4<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">如果砂粒间因固相反应而烧结成致密层，间隙变小，</span>则不易产生机械粘砂；</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">5<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">如果在型芯砂中加入煤粉、重油等物质。造成还原性气氛</span><span style="margin: 0px; padding: 0px;">及增加铸型背压，则不易产生机械粘砂；</span></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">6<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">如果采用导热快、蓄热能力大的错砂、铭铁矿砂等型芯</span><span style="margin: 0px; padding: 0px;">砂，则不易产生机械粘砂；</span></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">7<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">如果提高浇注温度及铸件热容量大时，则易产生机械粘砂；</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">8<span style="margin: 0px; padding: 0px;">）</span> </span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">液态金属的压力大时，则易产生机械粘砂；</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><br/></span></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">通过上述影响因素的分析我们可以看出，在铸型表面涂敷一薄层涂料是防止机械粘砂最有效、最节省的措施。这一薄层涂料 完全可以按照防止机械粘砂最有利的条件来设计和配制。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; color: rgb(123, 12, 0); font-size: 16px;"><strong style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; line-height: 24px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1.1.2</span><span style="margin: 0px; padding: 0px; letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">化学粘砂形成机理</span></strong></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">化学粘砂是金属氧化物和铸型材料相互产生化学反应,生成一 系列低熔点物质，这些低熔点物质牢固地粘附在铸件表面上的结果。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">这些化学反应中</span>,首先是金属的氧化。黑色金属表面极易氧化，高温下它的表面每秒钟可以形成</span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">0.001mm</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">厚的氧化层。当</span><span style="margin: 0px; padding: 0px;">钢液浇入砂型后，在型腔内空气或砂中水分的作用下，靠近砂型</span> <span style="margin: 0px; padding: 0px;">的表面部分会生成氧化亚铁：</span></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;"><br/></span></span></span></section><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0seQAacpbDSpjVefzCfhnSTq6QhtA3g5T0VvM4UvtZXKSQBRzlmIonzw/640?wx_fmt=png"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">氧化亚铁的熔点是</span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman"; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;">1370 °C ,</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">低于钢的熔点，并能润湿石英</span><span style="margin: 0px; padding: 0px;">砂。氧化亚铁易于渗入砂型，并和型砂中的二氧化硅发生反应</span>, 生成低熔点物质硅酸亚铁（又金铁橄榄石）等。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0pt; font-variant-numeric: normal; font-variant-east-asian: normal;"><br/></span></span></section><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0sNWnFboYhQAlhunvIicD0xJE3n5ibTcfohbcGBDMAna9zcOSHsvvQHFWA/640?wx_fmt=png"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(0, 0, 0); letter-spacing: 0px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">铁橄榄石的熔点为</span>1205 °C,<span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">除了铁橄榄石外，还可形成其</span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">它低熔点物质，其组成及熔点况表</span>1-1</span></section></p><p style="margin: 0pt 0pt 5pt; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; white-space: normal; text-indent: 21pt; line-height: 16.5pt;"><br/></p><p><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0s9Q201F2euGNQm4GplSzbXK0hiaKNyYx6ctZ7eflCCoQCiah4jUDZicwlw/640?wx_fmt=png"/></section><section><br/></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">在上述化学反应中的二氧化硅并不是石英砂本身，而是粘土分解产生的二氧化硅。有人用不含粘土的石英砂造型，并用磨得 很细的石英粉做粘结剂时，得到的铸铁件和铸钢件都没有粘砂。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">砂型中若含有碱性物质则会加剧铸件的化学粘砂。这是由于</span><span style="margin: 0px; padding: 0px;">形成了易熔的硅酸盐。由</span></span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">Na</span><sub style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: sub;">2</span></sub><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">O-FeO-SiO</span><sub style="margin: 0px; padding: 0px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; vertical-align: sub;">2</span></sub><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">系统的状态图可知其</span><span style="margin: 0px; padding: 0px;">中熔点最低的可低于</span></span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">500℃</span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;">。</span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-family: 宋体;"><br/></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; color: rgb(0, 0, 0); letter-spacing: 0px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">低熔点物质生成后，由于它们流动性好又能润湿型壁，故易</span> <span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">于渗入砂型孔隙内。这样又扩大氧化铁和型砂的作用面积，加剧</span> <span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">了化学粘砂。化学反应的结果又扩大了砂粒间的孔隙，更有利于</span><span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">低熔点物质向砂型深处渗入，从而将金属和砂型联成一体，如图</span> 1-4<span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">所示。</span></span></section></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; white-space: normal;"><br/></p><p style="margin-top: 0px; margin-bottom: 0px; padding: 0px; clear: both; color: rgb(51, 51, 51); font-family: mp-quote, -apple-system-font, BlinkMacSystemFont, "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", Arial, sans-serif; font-size: 17px; text-align: justify; white-space: normal;"><br/></p><p><section><img class="rich_pages" src="https://mmbiz.qpic.cn/mmbiz_png/TCIDp9rFWaYH256K8lR0PjicvrSM2OJ0sR7A2QnRJeqXroAqXFugx0rjzQ4FPCL6oicibm3l0xO1eQDicXK8U4C9Kg/640?wx_fmt=png"/></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px;"><span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">低熔点物质在铸件表面上形成烧结层后，烧结层与铸件表面</span> <span style="margin: 0px; padding: 0px; font-family: "Times New Roman";">若牢</span></span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); font-family: 宋体; letter-spacing: 0px; text-indent: 29px;">固地粘附在一起，则形成化学粘砂。若烧结层很容易从铸件 表面剥离下来，则非但不会造成化学粘砂，反而成为一种防止化学粘砂的措施.所以目前许多铸造工作者纷纷研究如何得到易剥离的烧结层。</span></span></section><section><br/></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">到目前为止，对烧结层与铸件表面粘结强度的研究还是很不充分的，各家的说法也不一致。大致可归纳为三种学说如下：</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">第一种学说认为，若铸件与烧结层之间的氧化铁的厚度达到</span><span style="margin: 0px; padding: 0px;">某个临界厚度，粘砂层就容易从铸件上清除下来。当使用水玻璃</span> <span style="margin: 0px; padding: 0px;">砂时，这个厚度为</span></span><span style="margin: 0px; padding: 0px; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;">100μ</span><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;">左右。为了防止化学粘砂，应增加氧化</span> <span style="margin: 0px; padding: 0px;">铁层厚度。采用石灰石砂型生产铸钢件时，由于石灰石分解产生</span><span style="margin: 0px; padding: 0px;">二氧化碳气体。二氧化碳气体是氧化性气体，它加剧了铸钢表面</span> <span style="margin: 0px; padding: 0px;">的氧化，使低熔点烧结层和铸件之间有一层很厚的氧化铁层，故</span><span style="margin: 0px; padding: 0px;">采用石灰石砂型生产铸钢件有良好的防粘砂效果。</span></span></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px;"><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal;"><span style="margin: 0px; padding: 0px;"><br/></span></span></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">在高温下氧化铁不断生成，也在不断消耗。如氧化铁生成速 度与其消耗速度相近，则氧化铁层的必要厚度就建立不起来。氧 化铁将形成铁橄榄石等低熔点物并牢固地粘附在铸件表面。如氧 化铁的生成速度大于其消耗速度，则在烧结层与铸件表面之间逐 渐积累起氧化铁层。当氧化铁层厚度达到临界厚度以上时，烧结 层易剥落。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;">铸钢件表面容易氧化，故一定厚度的氧化铁层的形成比较容易实现。铸铁中的碳、硅，锭等元素有防止铁氧化的作用，故在 铸铁件表面与烧结层之间不可能得到适宜厚度的氧化铁层。</span></section><section><span style="margin: 0px; padding: 0px; font-family: 宋体; color: rgb(0, 0, 0); letter-spacing: 0px; font-variant-numeric: normal; font-variant-east-asian: normal; font-size: 14px;"><br/></span></section><section><span style="margin: 0px; padding: 0px; font-size: 14px; font-family: 宋体; color: rgb(0, 0, 0); letter-sp
