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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:2024-07-04 19:20
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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(yōu)點(diǎn),而在機械等行業(yè)被越來(lái)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(jīng)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(jīng)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(guò)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(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(guò)對粉末冶金零件整形芯棒的深冷處理,來(lái)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(chǎng)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(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測定其壽命,并用低倍放大鏡分別觀(guān)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(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)</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(cháng),模具失效前整形的零件個(gè)數也就越多,即模具的使用壽命也就越長(cháng)。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(guò)兩小時(shí),模具壽命發(fā)生跳躍式上升,而后隨著(zhù)保溫時(shí)間的延長(cháng)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(guān)察失效整形模具表面發(fā)現,模具表面布滿(mǎn)剝落坑和很多細小犁溝。這是由于模具在整形過(guò)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(guò)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(fā)生反復變形,產(chǎn)生位錯塞積,而萌生裂紋,在反復擠壓過(guò)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(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(guò)程中在模具表面產(chǎn)生犁削,使模具表面布滿(mǎn)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(guò)程中組織結構發(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(zhù)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(lái)產(chǎn)生馬氏體,深冷處理就是利用過(guò)冷度來(lái)增加馬氏體轉變的驅動(dòng)力,隨著(zhù)深冷溫度降低,過(guò)冷度增加,馬氏體轉變越完全。在冷卻過(guò)程中殘余奧氏體向馬氏體的轉變速度,不取決與時(shí)間,而與過(guò)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(guò)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小碳化物析出和組織細化,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(guò)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(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變就較為完全,但馬氏體中析出的細小碳化物的量隨著(zhù)保溫時(shí)間的延長(cháng)而緩慢增加。因此,模具壽命也隨保溫時(shí)間延長(cháng)而緩慢增加。如果考慮到隨著(zhù)保溫時(shí)間延長(cháng),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;">.結語(yǔ)</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(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(cháng)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(yōu)點(diǎn),而在機械等行業(yè)被越來(lái)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(jīng)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(jīng)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(guò)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(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(guò)對粉末冶金零件整形芯棒的深冷處理,來(lái)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(chǎng)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(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 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測定其壽命,并用低倍放大鏡分別觀(guān)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(jīng)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(shí)間 
    (h)

平均使用壽命 
(整形零件個(gè)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(jīng)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(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(cháng),模具失效前整形的零件個(gè)數也就越多,即模具的使用壽命也就越長(cháng)。但保溫時(shí)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(shí)間超過(guò)兩小時(shí),模具壽命發(fā)生跳躍式上升,而后隨著(zhù)保溫時(shí)間的延長(cháng)模具壽命平緩上升。 
2.2試驗結果分析 
觀(guān)察失效整形模具表面發(fā)現,模具表面布滿(mǎn)剝落坑和很多細小犁溝。這是由于模具在整形過(guò)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(guò)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(fā)生反復變形,產(chǎn)生位錯塞積,而萌生裂紋,在反復擠壓過(guò)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(zhì)——多種硬質(zhì)相粒子,在模具整形過(guò)程中在模具表面產(chǎn)生犁削,使模具表面布滿(mǎn)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)生尺寸超差而報廢。 
GCr15模具鋼制作的芯棒在深冷處理過(guò)程中組織結構發(fā)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(zhù)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(lái)產(chǎn)生馬氏體,深冷處理就是利用過(guò)冷度來(lái)增加馬氏體轉變的驅動(dòng)力,隨著(zhù)深冷溫度降低,過(guò)冷度增加,馬氏體轉變越完全。在冷卻過(guò)程中殘余奧氏體向馬氏體的轉變速度,不取決與時(shí)間,而與過(guò)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(guò)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小碳化物析出和組織細化,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(高于-160℃),過(guò)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(shí)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(zhù)保溫時(shí)間的延長(cháng)而緩慢增加。因此,模具壽命也隨保溫時(shí)間延長(cháng)而緩慢增加。如果考慮到隨著(zhù)保溫時(shí)間延長(cháng),模具深冷處理的成本也增大,那么取保溫時(shí)間為24h*適宜。 
3.結語(yǔ) 
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(jīng)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(shí)間越長(cháng)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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