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    粉末冶金零件整形模具的深冷處理工藝的研究

    日期:2022-07-15 00:59
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    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點,而在機械等行業被越來越廣泛應用。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-整形。經整形后的粉末冶金零件只要稍微機加工一下就直接裝備,因此,對經整形后的零件尺寸的公差有嚴格要求,為了保證粉末冶金零件尺寸要求,對整形模具陰模和芯棒的尺寸公差的要求也就比較嚴格,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,很容易由于嚴重磨損引起尺寸超差而報廢。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粉末冶金零件質量和降低粉末冶金零件生產成本都有十分重要意義。本文擬通過對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.試驗方法&nbsp;</span><br /> <span style="font-size:14px;">從某粉末冶金廠取一批機加工好后的132襯套整形芯棒,芯棒材料為GCr15。芯棒經正常的淬火+150℃低溫回火后,盡快進行深冷處理,深冷溫度分別有-100℃、-120℃、-140℃、-160℃和-196℃五種,保溫時間分別有1h、2h、4h、和8h&nbsp;4個時間。深冷處理后的模具都經低于150℃的溫度回火,保溫時間均為1h,并分別測定其硬度。把經深冷處理的芯棒與同批熱處理而未經深冷處理的芯棒分別裝機測定其壽命,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.試驗結果及分析&nbsp;</span><br /> <span style="font-size:14px;">2.1試驗結果&nbsp;</span><br /> <span style="font-size:14px;">表1&nbsp;芯棒經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;">(整形零件個數)</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深冷處理后,使用壽命明顯提高。深冷溫度越低、保溫時間越長,模具失效前整形的零件個數也就越多,即模具的使用壽命也就越長。但保溫時間相同情況下,</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,保溫時間超過兩小時,模具壽命發生跳躍式上升,而后隨著保溫時間的延長模具壽命平緩上升。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">2.2</span><span style="font-size:14px;">試驗結果分析</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現,模具表面布滿剝落坑和很多細小犁溝。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</span><span style="font-size:14px;">7.0g/cm3</span><span style="font-size:14px;">,燒結后硬度也較高,芯棒和陰模在整形過程中受到很大的擠壓力,模具在反復擠壓下,在模具亞表層殘余奧氏體處發生反復變形,產生位錯塞積,而萌生裂紋,在反復擠壓過程中裂紋擴展,直至表面而剝落,形成嚴重的剝落坑</span><span style="font-size:14px;">(1)</span><span style="font-size:14px;">。另外粉體中存在的雜質</span><span style="font-size:14px;">——</span><span style="font-size:14px;">多種硬質相粒子,在模具整形過程中在模具表面產生犁削,使模具表面布滿犁溝,由于雜質粒子較小,故形成的犁溝較淺。芯棒由剝落和犁削共同作用下,產生尺寸超差而報廢。</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構發生如下變化</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理來產生馬氏體,深冷處理就是利用過冷度來增加馬氏體轉變的驅動力,隨著深冷溫度降低,過冷度增加,馬氏體轉變越完全。在冷卻過程中殘余奧氏體向馬氏體的轉變速度,不取決與時間,而與過冷度有關,即殘余奧氏體量只與深冷溫度有關。另外,深冷處理還可以析出細小碳化物,細化組織結構。</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,同時由于殘余奧氏體量減少以及細小碳化物析出和組織細化,使犁削難度增加。因此,芯棒經深冷處理后,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變的能量不足,殘余奧氏體量較多,表現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變就較為完全,但馬氏體中析出的細小碳化物的量隨著保溫時間的延長而緩慢增加。因此,模具壽命也隨保溫時間延長而緩慢增加。如果考慮到隨著保溫時間延長,模具深冷處理的成本也增大,那么取保溫時間為</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理為疲勞磨損和磨粒磨損。模具經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,保溫時間越長模具壽命越高,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>

    粉末冶金零件整形模具的深冷處理工藝的研究

        [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理和*佳冷處理工藝。 
    粉末冶金零件由于其固有的優點,而在機械等行業被越來越廣泛應用。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-整形。經整形后的粉末冶金零件只要稍微機加工一下就直接裝備,因此,對經整形后的零件尺寸的公差有嚴格要求,為了保證粉末冶金零件尺寸要求,對整形模具陰模和芯棒的尺寸公差的要求也就比較嚴格,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,很容易由于嚴重磨損引起尺寸超差而報廢。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粉末冶金零件質量和降低粉末冶金零件生產成本都有十分重要意義。本文擬通過對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。 
    1.試驗方法 
    從某粉末冶金廠取一批機加工好后的132襯套整形芯棒,芯棒材料為GCr15。芯棒經正常的淬火+150℃低溫回火后,盡快進行深冷處理,深冷溫度分別有-100℃、-120℃、-140℃、-160℃和-196℃五種,保溫時間分別有1h、2h、4h、和8h 4個時間。深冷處理后的模具都經低于150℃的溫度回火,保溫時間均為1h,并分別測定其硬度。把經深冷處理的芯棒與同批熱處理而未經深冷處理的芯棒分別裝機測定其壽命,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。 
    2.試驗結果及分析 
    2.1試驗結果 
    表1 芯棒經不同處理工藝的壽命及硬度


    深冷處理溫度 
       (℃)

    深冷處理保溫時間 
        (h)

    平均使用壽命 
    (整形零件個數)

    平均硬度 
    (HPC)

    -100

    1

    3800

    60.5

    2

    4100

    60.6

    4

    4300

    61

    8

    4500

    61.5

    -120

    1

    4400

    60.5

    2

    4800

    61

     

    5100

    61

     

    5300

    61.5

    -140

    1

    5200

    61

    2

    5500

    61.5

    4

    5800

    61.5

    8

    6100

    62

    -160

    1

    5900

    62

    2

    6600

    62

    4

    6900

    62

    8

    7100

    62

    -196

    1

    6300

    62

    2

    6800

    62

    4

    7100

    62

    8

    7200

    62

    未經深冷處理

     

    3000

    60.5

    由表1可以看出,粉末冶金零件整形芯棒經深冷處理后,使用壽命明顯提高。深冷溫度越低、保溫時間越長,模具失效前整形的零件個數也就越多,即模具的使用壽命也就越長。但保溫時間相同情況下,-160℃-196℃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,保溫時間超過兩小時,模具壽命發生跳躍式上升,而后隨著保溫時間的延長模具壽命平緩上升。 
    2.2試驗結果分析 
    觀察失效整形模具表面發現,模具表面布滿剝落坑和很多細小犁溝。這是由于模具在整形過程中,被整形的粉末冶金零件132襯套的粉體密度較高,達7.0g/cm3,燒結后硬度也較高,芯棒和陰模在整形過程中受到很大的擠壓力,模具在反復擠壓下,在模具亞表層殘余奧氏體處發生反復變形,產生位錯塞積,而萌生裂紋,在反復擠壓過程中裂紋擴展,直至表面而剝落,形成嚴重的剝落坑(1)。另外粉體中存在的雜質——多種硬質相粒子,在模具整形過程中在模具表面產生犁削,使模具表面布滿犁溝,由于雜質粒子較小,故形成的犁溝較淺。芯棒由剝落和犁削共同作用下,產生尺寸超差而報廢。 
    GCr15模具鋼制作的芯棒在深冷處理過程中組織結構發生如下變化(2)(3),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理來產生馬氏體,深冷處理就是利用過冷度來增加馬氏體轉變的驅動力,隨著深冷溫度降低,過冷度增加,馬氏體轉變越完全。在冷卻過程中殘余奧氏體向馬氏體的轉變速度,不取決與時間,而與過冷度有關,即殘余奧氏體量只與深冷溫度有關。另外,深冷處理還可以析出細小碳化物,細化組織結構。 
    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,同時由于殘余奧氏體量減少以及細小碳化物析出和組織細化,使犁削難度增加。因此,芯棒經深冷處理后,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(高于-160℃),過冷度較小,殘余奧氏體向馬氏體的轉變的能量不足,殘余奧氏體量較多,表現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,只要保溫時間足以使芯棒冷透(不小于2h),殘余奧氏體向馬氏體的轉變就較為完全,但馬氏體中析出的細小碳化物的量隨著保溫時間的延長而緩慢增加。因此,模具壽命也隨保溫時間延長而緩慢增加。如果考慮到隨著保溫時間延長,模具深冷處理的成本也增大,那么取保溫時間為24h*適宜。 
    3.結語 
    粉末冶金零件整形模具的破壞機理為疲勞磨損和磨粒磨損。模具經深冷處理可以大幅度提高其壽命。深冷溫度以-160℃-196℃為*佳,保溫時間越長模具壽命越高,但從成本和壽命兩方面綜合考慮,取24h為宜。

     

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