摘要：<p class="MsoNormal" style="white-space:normal;text-align:center;"> <span style="font-size:14px;">粉末冶金零件整形模具的深冷處理工藝的研究</span> </p> <p class="p" style="white-space:normal;"> <span style="font-size:14px;">&nbsp;&nbsp;&nbsp;&nbsp;［摘要］分析了不同深冷工藝處理的整形芯棒壽命和磨損形貌，探討了整形模具的磨損機(jī)理和*佳冷處理工藝。&nbsp;</span><br /> <span style="font-size:14px;">粉末冶金零件由于其固有的優(yōu)點(diǎn)，而在機(jī)械等行業(yè)被越來越廣泛應(yīng)用。粉末冶金零件的制作工藝一般是這樣的：粉體壓制成型-高溫澆結(jié)-整形。經(jīng)整形后的粉末冶金零件只要稍微機(jī)加工一下就直接裝備，因此，對(duì)經(jīng)整形后的零件尺寸的公差有嚴(yán)格要求，為了保證粉末冶金零件尺寸要求，對(duì)整形模具陰模和芯棒的尺寸公差的要求也就比較嚴(yán)格，如某種襯套的整形芯棒尺寸要求Ф20+0.025。陰模和芯棒在整形過程中受到很大的擠壓力作用，工況條件十分惡劣，很容易由于嚴(yán)重磨損引起尺寸超差而報(bào)廢。因此，提高粉末冶金零件整形模具的耐磨性，從而提高整形模具的壽命對(duì)粉末冶金零件質(zhì)量和降低粉末冶金零件生產(chǎn)成本都有十分重要意義。本文擬通過對(duì)粉末冶金零件整形芯棒的深冷處理，來探討出提高粉末冶金零件整形模具壽命的深冷處理工藝。&nbsp;</span><br /> <span style="font-size:14px;">1．試驗(yàn)方法&nbsp;</span><br /> <span style="font-size:14px;">從某粉末冶金廠取一批機(jī)加工好后的132襯套整形芯棒，芯棒材料為GCr15。芯棒經(jīng)正常的淬火+150℃低溫回火后，盡快進(jìn)行深冷處理，深冷溫度分別有-100℃、-120℃、-140℃、-160℃和-196℃五種，保溫時(shí)間分別有1h、2h、4h、和8h&nbsp;4個(gè)時(shí)間。深冷處理后的模具都經(jīng)低于150℃的溫度回火，保溫時(shí)間均為1h，并分別測(cè)定其硬度。把經(jīng)深冷處理的芯棒與同批熱處理而未經(jīng)深冷處理的芯棒分別裝機(jī)測(cè)定其壽命，并用低倍放大鏡分別觀察處理工藝不同的模具的磨損形貌。&nbsp;</span><br /> <span style="font-size:14px;">2．試驗(yàn)結(jié)果及分析&nbsp;</span><br /> <span style="font-size:14px;">2.1試驗(yàn)結(jié)果&nbsp;</span><br /> <span style="font-size:14px;">表1&nbsp;芯棒經(jīng)不同處理工藝的壽命及硬度</span> </p> <table class="MsoNormalTable" align="center" style="width:809px;"> <tbody> <tr> <td width="125" valign="center" style="border:0.75pt outset windowtext;"> <p class="MsoNormal" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:12pt;"><br /> </span><span style="font-family:宋體;font-size:14px;">深冷處理溫度&nbsp;</span><span style="font-family:宋體;font-size:12pt;"><br /> </span><span style="font-family:宋體;font-size:14px;">&nbsp;&nbsp;&nbsp;（℃）</span><span style="font-family:&quot;Times New Roman&quot;;font-size:10.5pt;"></span> </p> </td> <td width="175" valign="top" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">深冷處理保溫時(shí)間&nbsp;</span><span style="font-family:宋體;font-size:10pt;"><br /> </span><span style="font-family:宋體;font-size:14px;">&nbsp;&nbsp;&nbsp;&nbsp;（h）</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">平均使用壽命&nbsp;</span><span style="font-family:宋體;font-size:10pt;"><br /> </span><span style="font-family:宋體;font-size:14px;">（整形零件個(gè)數(shù)）</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">平均硬度&nbsp;</span><span style="font-family:宋體;font-size:10pt;"><br /> </span><span style="font-family:宋體;font-size:14px;">（HPC）</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="125" valign="center" rowspan="4" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">-100</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">1</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">3800</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">60.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">2</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4100</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">60.6</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4300</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">8</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4500</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="125" valign="center" rowspan="4" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">-120</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">1</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4400</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">60.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">2</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4800</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">&nbsp;</span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">5100</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">&nbsp;</span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">5300</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="125" valign="center" rowspan="4" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">-140</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">1</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">5200</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">2</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">5500</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">5800</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">61.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">8</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">6100</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="125" valign="center" rowspan="4" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">-160</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">1</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">5900</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">2</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">6600</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">6900</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">8</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">7100</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="125" valign="center" rowspan="4" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">-196</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">1</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">6300</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">2</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">6800</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">4</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">7100</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">8</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">7200</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">62</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> <tr> <td width="125" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">未經(jīng)深冷處理</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="175" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">&nbsp;</span> </p> </td> <td width="168" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">3000</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> <td width="156" valign="center" style="border:0.75pt outset windowtext;"> <p class="p" style="margin-left:0pt;text-align:center;"> <span style="font-family:宋體;font-size:14px;">60.5</span><span style="font-family:宋體;font-size:10pt;"></span> </p> </td> </tr> </tbody> </table> <p class="MsoNormal" style="white-space:normal;"> <span style="font-size:14px;">由表</span><span style="font-size:14px;">1</span><span style="font-size:14px;">可以看出，粉末冶金零件整形芯棒經(jīng)深冷處理后，使用壽命明顯提高。深冷溫度越低、保溫時(shí)間越長(zhǎng)，模具失效前整形的零件個(gè)數(shù)也就越多，即模具的使用壽命也就越長(zhǎng)。但保溫時(shí)間相同情況下，</span><span style="font-size:14px;">-160℃</span><span style="font-size:14px;">和</span><span style="font-size:14px;">-196℃</span><span style="font-size:14px;">兩種深冷處理溫度整形芯棒的壽命相差不大。在相同的處理溫度下，保溫時(shí)間超過兩小時(shí)，模具壽命發(fā)生跳躍式上升，而后隨著保溫時(shí)間的延長(zhǎng)模具壽命平緩上升。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">2.2</span><span style="font-size:14px;">試驗(yàn)結(jié)果分析</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">觀察失效整形模具表面發(fā)現(xiàn)，模具表面布滿剝落坑和很多細(xì)小犁溝。這是由于模具在整形過程中，被整形的粉末冶金零件</span><span style="font-size:14px;">132</span><span style="font-size:14px;">襯套的粉體密度較高，達(dá)</span><span style="font-size:14px;">7.0g/cm3</span><span style="font-size:14px;">，燒結(jié)后硬度也較高，芯棒和陰模在整形過程中受到很大的擠壓力，模具在反復(fù)擠壓下，在模具亞表層殘余奧氏體處發(fā)生反復(fù)變形，產(chǎn)生位錯(cuò)塞積，而萌生裂紋，在反復(fù)擠壓過程中裂紋擴(kuò)展，直至表面而剝落，形成嚴(yán)重的剝落坑</span><span style="font-size:14px;">(1)</span><span style="font-size:14px;">。另外粉體中存在的雜質(zhì)</span><span style="font-size:14px;">——</span><span style="font-size:14px;">多種硬質(zhì)相粒子，在模具整形過程中在模具表面產(chǎn)生犁削，使模具表面布滿犁溝，由于雜質(zhì)粒子較小，故形成的犁溝較淺。芯棒由剝落和犁削共同作用下，產(chǎn)生尺寸超差而報(bào)廢。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">GCr15</span><span style="font-size:14px;">模具鋼制作的芯棒在深冷處理過程中組織結(jié)構(gòu)發(fā)生如下變化</span><span style="font-size:14px;">(2)(3)</span><span style="font-size:14px;">，殘余奧氏體量減少。殘余奧氏體中合金元素，特別是碳元素起著強(qiáng)化殘余奧氏體的作用，因而需要較多的能量才能促使剪切機(jī)理來產(chǎn)生馬氏體，深冷處理就是利用過冷度來增加馬氏體轉(zhuǎn)變的驅(qū)動(dòng)力，隨著深冷溫度降低，過冷度增加，馬氏體轉(zhuǎn)變?cè)酵耆?。在冷卻過程中殘余奧氏體向馬氏體的轉(zhuǎn)變速度，不取決與時(shí)間，而與過冷度有關(guān)，即殘余奧氏體量只與深冷溫度有關(guān)。另外，深冷處理還可以析出細(xì)小碳化物，細(xì)化組織結(jié)構(gòu)。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">深冷處理減少了殘余奧氏體量，增加了芯棒在擠壓過程中在亞表層萌生裂紋的難度，同時(shí)由于殘余奧氏體量減少以及細(xì)小碳化物析出和組織細(xì)化，使犁削難度增加。因此，芯棒經(jīng)深冷處理后，增加了抗疲勞磨損和磨粒磨損的能力，從而提高了芯棒壽命。如果深冷處理溫度較高</span><span style="font-size:14px;">(</span><span style="font-size:14px;">高于</span><span style="font-size:14px;">-160℃)</span><span style="font-size:14px;">，過冷度較小，殘余奧氏體向馬氏體的轉(zhuǎn)變的能量不足，殘余奧氏體量較多，表現(xiàn)在模具硬度幾乎不變，模具壽命提高不多。在較低溫度下深冷處理，只要保溫時(shí)間足以使芯棒冷透</span><span style="font-size:14px;">(</span><span style="font-size:14px;">不小于</span><span style="font-size:14px;">2h)</span><span style="font-size:14px;">，殘余奧氏體向馬氏體的轉(zhuǎn)變就較為完全，但馬氏體中析出的細(xì)小碳化物的量隨著保溫時(shí)間的延長(zhǎng)而緩慢增加。因此，模具壽命也隨保溫時(shí)間延長(zhǎng)而緩慢增加。如果考慮到隨著保溫時(shí)間延長(zhǎng)，模具深冷處理的成本也增大，那么取保溫時(shí)間為</span><span style="font-size:14px;">2</span><span style="font-size:14px;">～</span><span style="font-size:14px;">4h</span><span style="font-size:14px;">*適宜。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">3</span><span style="font-size:14px;">．結(jié)語</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">粉末冶金零件整形模具的破壞機(jī)理為疲勞磨損和磨粒磨損。模具經(jīng)深冷處理可以大幅度提高其壽命。深冷溫度以</span><span style="font-size:14px;">-160℃</span><span style="font-size:14px;">～</span><span style="font-size:14px;">-196℃</span><span style="font-size:14px;">為*佳，保溫時(shí)間越長(zhǎng)模具壽命越高，但從成本和壽命兩方面綜合考慮，取</span><span style="font-size:14px;">2</span><span style="font-size:14px;">～</span><span style="font-size:14px;">4h</span><span style="font-size:14px;">為宜。</span> </p> <p class="MsoNormal" style="white-space:normal;"> <span style="font-size:14px;">&nbsp;</span> </p>