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          粉末冶金零件整形模具的深冷处理工艺的研究

          日期:2024-01-17 21:51
          浏览次数:0
          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处理工艺的研究</span> </p> <p class="p" style="white-space:normal;"> <span style="font-size:14px;">&nbsp;&nbsp;&nbsp;&nbsp;[摘要]分析了不同深冷工艺处理的整形芯棒寿命和磨损形貌,探讨了整形模具的磨损机理和*佳冷处理工艺。&nbsp;</span><br /> <span style="font-size:14px;">粉末冶金零件由于其固有的优点,而在机械等行业被越来越广泛应用。粉末冶金零件的制作工艺一般是这样的:粉体压制成型-高温浇结-整形。经整形后的粉末冶金零件只要稍微机加工一下就直接装备,因此,对经整形后的零件尺寸的公差有严格要求,为了保证粉末冶金零件尺寸要求,对整形模具阴模和芯棒的尺寸公差的要求也就比较严格,如某种衬套的整形芯棒尺寸要求Ф20+0.025。阴模和芯棒在整形过程中受到很大的挤压力作用,工况条件十分恶劣,很容易由于严重磨损引起尺寸超差而报废。因此,提高粉末冶金零件整形模具的耐磨性,从而提高整形模具的寿命对粉末冶金零件质量和降低粉末冶金零件生产成本都有十分重要意义。本文拟通过对粉末冶金零件整形芯棒的深冷处理,来探讨出提高粉末冶金零件整形模具寿命的深冷处理工艺。&nbsp;</span><br /> <span style="font-size:14px;">1.试验方法&nbsp;</span><br /> <span style="font-size:14px;">从某粉末冶金厂取一批机加工好后的132衬套整形芯棒,芯棒材料为GCr15。芯棒经正常的淬火+150℃低温回火后,尽快进行深冷处理,深冷温度分别有-100℃、-120℃、-140℃、-160℃和-196℃五种,保温时间分别有1h、2h、4h、和8h&nbsp;4个时间。深冷处理后的模具都经低于150℃的温度回火,保温时间均为1h,并分别测定其硬度。把经深冷处理的芯棒与同批热处理而未经深冷处理的芯棒分别装机测定其寿命,并用低倍放大镜分别观察处理工艺不同的模具的磨损形貌。&nbsp;</span><br /> <span style="font-size:14px;">2.试验结果及分析&nbsp;</span><br /> <span style="font-size:14px;">2.1试验结果&nbsp;</span><br /> <span style="font-size:14px;">表1&nbsp;芯棒经不同处理工艺的寿命及硬度</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:宋体;font-size:12pt;"><br /> </span><span style="font-family:宋体;font-size:14px;">深冷处理温度&nbsp;</span><span style="font-family:宋体;font-size:12pt;"><br /> </span><span style="font-family:宋体;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:宋体;font-size:14px;">深冷处理保温时间&nbsp;</span><span style="font-family:宋体;font-size:10pt;"><br /> </span><span style="font-family:宋体;font-size:14px;">&nbsp;&nbsp;&nbsp;&nbsp;(h)</span><span style="font-family:宋体;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:宋体;font-size:14px;">平均使用寿命&nbsp;</span><span style="font-family:宋体;font-size:10pt;"><br /> </span><span style="font-family:宋体;font-size:14px;">(整形零件个数)</span><span style="font-family:宋体;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:宋体;font-size:14px;">平均硬度&nbsp;</span><span style="font-family:宋体;font-size:10pt;"><br /> </span><span style="font-family:宋体;font-size:14px;">(HPC)</span><span style="font-family:宋体;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:宋体;font-size:14px;">-100</span><span style="font-family:宋体;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:宋体;font-size:14px;">1</span><span style="font-family:宋体;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:宋体;font-size:14px;">3800</span><span style="font-family:宋体;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:宋体;font-size:14px;">60.5</span><span style="font-family:宋体;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:宋体;font-size:14px;">2</span><span style="font-family:宋体;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:宋体;font-size:14px;">4100</span><span style="font-family:宋体;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:宋体;font-size:14px;">60.6</span><span style="font-family:宋体;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:宋体;font-size:14px;">4</span><span style="font-family:宋体;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:宋体;font-size:14px;">4300</span><span style="font-family:宋体;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:宋体;font-size:14px;">61</span><span style="font-family:宋体;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:宋体;font-size:14px;">8</span><span style="font-family:宋体;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:宋体;font-size:14px;">4500</span><span style="font-family:宋体;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:宋体;font-size:14px;">61.5</span><span style="font-family:宋体;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:宋体;font-size:14px;">-120</span><span style="font-family:宋体;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:宋体;font-size:14px;">1</span><span style="font-family:宋体;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:宋体;font-size:14px;">4400</span><span style="font-family:宋体;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:宋体;font-size:14px;">60.5</span><span style="font-family:宋体;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:宋体;font-size:14px;">2</span><span style="font-family:宋体;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:宋体;font-size:14px;">4800</span><span style="font-family:宋体;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:宋体;font-size:14px;">61</span><span style="font-family:宋体;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:宋体;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:宋体;font-size:14px;">5100</span><span style="font-family:宋体;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:宋体;font-size:14px;">61</span><span style="font-family:宋体;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:宋体;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:宋体;font-size:14px;">5300</span><span style="font-family:宋体;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:宋体;font-size:14px;">61.5</span><span style="font-family:宋体;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:宋体;font-size:14px;">-140</span><span style="font-family:宋体;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:宋体;font-size:14px;">1</span><span style="font-family:宋体;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:宋体;font-size:14px;">5200</span><span style="font-family:宋体;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:宋体;font-size:14px;">61</span><span style="font-family:宋体;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:宋体;font-size:14px;">2</span><span style="font-family:宋体;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:宋体;font-size:14px;">5500</span><span style="font-family:宋体;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:宋体;font-size:14px;">61.5</span><span style="font-family:宋体;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:宋体;font-size:14px;">4</span><span style="font-family:宋体;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:宋体;font-size:14px;">5800</span><span style="font-family:宋体;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:宋体;font-size:14px;">61.5</span><span style="font-family:宋体;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:宋体;font-size:14px;">8</span><span style="font-family:宋体;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:宋体;font-size:14px;">6100</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">-160</span><span style="font-family:宋体;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:宋体;font-size:14px;">1</span><span style="font-family:宋体;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:宋体;font-size:14px;">5900</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">2</span><span style="font-family:宋体;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:宋体;font-size:14px;">6600</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">4</span><span style="font-family:宋体;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:宋体;font-size:14px;">6900</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">8</span><span style="font-family:宋体;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:宋体;font-size:14px;">7100</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">-196</span><span style="font-family:宋体;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:宋体;font-size:14px;">1</span><span style="font-family:宋体;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:宋体;font-size:14px;">6300</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">2</span><span style="font-family:宋体;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:宋体;font-size:14px;">6800</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">4</span><span style="font-family:宋体;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:宋体;font-size:14px;">7100</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">8</span><span style="font-family:宋体;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:宋体;font-size:14px;">7200</span><span style="font-family:宋体;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:宋体;font-size:14px;">62</span><span style="font-family:宋体;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:宋体;font-size:14px;">未经深冷处理</span><span style="font-family:宋体;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:宋体;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:宋体;font-size:14px;">3000</span><span style="font-family:宋体;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:宋体;font-size:14px;">60.5</span><span style="font-family:宋体;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经深冷处理后,使用寿命明显提高。深冷温度越低、保温时间越长,模具失效前整形的零件个数也就越多,即模具的使用寿命也就越长。但保温时间相同情况下,</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;">两种深冷处理温度整形芯棒的寿命相差不大。在相同的处理温度下,保温时间超过两小时,模具寿命发生跳跃式上升,而后随着保温时间的延长模具寿命平缓上升。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">2.2</span><span style="font-size:14px;">试验结果分析</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">观察失效整形模具表面发现,模具表面布满剥落坑和很多细小犁沟。这是由于模具在整形过程中,被整形的粉末冶金零件</span><span style="font-size:14px;">132</span><span style="font-size:14px;">衬套的粉体密度较高,达</span><span style="font-size:14px;">7.0g/cm3</span><span style="font-size:14px;">,烧结后硬度也较高,芯棒和阴模在整形过程中受到很大的挤压力,模具在反复挤压下,在模具亚表层残余奥氏体处发生反复变形,产生位错塞积,而萌生裂纹,在反复挤压过程中裂纹扩展,直至表面而剥落,形成严重的剥落坑</span><span style="font-size:14px;">(1)</span><span style="font-size:14px;">。另外粉体中存在的杂质</span><span style="font-size:14px;">——</span><span style="font-size:14px;">多种硬质相粒子,在模具整形过程中在模具表面产生犁削,使模具表面布满犁沟,由于杂质粒子较小,故形成的犁沟较浅。芯棒由剥落和犁削共同作用下,产生尺寸超差而报废。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">GCr15</span><span style="font-size:14px;">模具钢制作的芯棒在深冷处理过程中组织结构发生如下变化</span><span style="font-size:14px;">(2)(3)</span><span style="font-size:14px;">,残余奥氏体量减少。残余奥氏体中合金元素,特别是碳元素起着强化残余奥氏体的作用,因而需要较多的能量才能促使剪切机理来产生马氏体,深冷处理就是利用过冷度来增加马氏体转变的驱动力,随着深冷温度降低,过冷度增加,马氏体转变越完全。在冷却过程中残余奥氏体向马氏体的转变速度,不取决与时间,而与过冷度有关,即残余奥氏体量只与深冷温度有关。另外,深冷处理还可以析出细小碳化物,细化组织结构。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">深冷处理减少了残余奥氏体量,增加了芯棒在挤压过程中在亚表层萌生裂纹的难度,同时由于残余奥氏体量减少以及细小碳化物析出和组织细化,使犁削难度增加。因此,芯棒经深冷处理后,增加了抗疲劳磨损和磨粒磨损的能力,从而提高了芯棒寿命。如果深冷处理温度较高</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;">,过冷度较小,残余奥氏体向马氏体的转变的能量不足,残余奥氏体量较多,表现在模具硬度几乎不变,模具寿命提高不多。在较低温度下深冷处理,只要保温时间足以使芯棒冷透</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;">,残余奥氏体向马氏体的转变就较为完全,但马氏体中析出的细小碳化物的量随着保温时间的延长而缓慢增加。因此,模具寿命也随保温时间延长而缓慢增加。如果考虑到随着保温时间延长,模具深冷处理的成本也增大,那么取保温时间为</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;">*适宜。</span><span style="font-size:14px;">&nbsp;</span><br /> <span style="font-size:14px;">3</span><span style="font-size:14px;">.结语</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坏机理为疲劳磨损和磨粒磨损。模具经深冷处理可以大幅度提高其寿命。深冷温度以</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;">为*佳,保温时间越长模具寿命越高,但从成本和寿命两方面综合考虑,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;">为宜。</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处理工艺的研究

              [摘要]分析了不同深冷工艺处理的整形芯棒寿命和磨损形貌,探讨了整形模具的磨损机理和*佳冷处理工艺。 
          粉末冶金零件由于其固有的优点,而在机械等行业被越来越广泛应用。粉末冶金零件的制作工艺一般是这样的:粉体压制成型-高温浇结-整形。经整形后的粉末冶金零件只要稍微机加工一下就直接装备,因此,对经整形后的零件尺寸的公差有严格要求,为了保证粉末冶金零件尺寸要求,对整形模具阴模和芯棒的尺寸公差的要求也就比较严格,如某种衬套的整形芯棒尺寸要求Ф20+0.025。阴模和芯棒在整形过程中受到很大的挤压力作用,工况条件十分恶劣,很容易由于严重磨损引起尺寸超差而报废。因此,提高粉末冶金零件整形模具的耐磨性,从而提高整形模具的寿命对粉末冶金零件质量和降低粉末冶金零件生产成本都有十分重要意义。本文拟通过对粉末冶金零件整形芯棒的深冷处理,来探讨出提高粉末冶金零件整形模具寿命的深冷处理工艺。 
          1.试验方法 
          从某粉末冶金厂取一批机加工好后的132衬套整形芯棒,芯棒材料为GCr15。芯棒经正常的淬火+150℃低温回火后,尽快进行深冷处理,深冷温度分别有-100℃、-120℃、-140℃、-160℃和-196℃五种,保温时间分别有1h、2h、4h、和8h 4个时间。深冷处理后的模具都经低于150℃的温度回火,保温时间均为1h,并分别测定其硬度。把经深冷处理的芯棒与同批热处理而未经深冷处理的芯棒分别装机测定其寿命,并用低倍放大镜分别观察处理工艺不同的模具的磨损形貌。 
          2.试验结果及分析 
          2.1试验结果 
          表1 芯棒经不同处理工艺的寿命及硬度


          深冷处理温度 
             (℃)

          深冷处理保温时间 
              (h)

          平均使用寿命 
          (整形零件个数)

          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

          未经深冷处理

           

          3000

          60.5

          由表1可以看出,粉末冶金零件整形芯棒经深冷处理后,使用寿命明显提高。深冷温度越低、保温时间越长,模具失效前整形的零件个数也就越多,即模具的使用寿命也就越长。但保温时间相同情况下,-160℃-196℃两种深冷处理温度整形芯棒的寿命相差不大。在相同的处理温度下,保温时间超过两小时,模具寿命发生跳跃式上升,而后随着保温时间的延长模具寿命平缓上升。 
          2.2试验结果分析 
          观察失效整形模具表面发现,模具表面布满剥落坑和很多细小犁沟。这是由于模具在整形过程中,被整形的粉末冶金零件132衬套的粉体密度较高,达7.0g/cm3,烧结后硬度也较高,芯棒和阴模在整形过程中受到很大的挤压力,模具在反复挤压下,在模具亚表层残余奥氏体处发生反复变形,产生位错塞积,而萌生裂纹,在反复挤压过程中裂纹扩展,直至表面而剥落,形成严重的剥落坑(1)。另外粉体中存在的杂质——多种硬质相粒子,在模具整形过程中在模具表面产生犁削,使模具表面布满犁沟,由于杂质粒子较小,故形成的犁沟较浅。芯棒由剥落和犁削共同作用下,产生尺寸超差而报废。 
          GCr15模具钢制作的芯棒在深冷处理过程中组织结构发生如下变化(2)(3),残余奥氏体量减少。残余奥氏体中合金元素,特别是碳元素起着强化残余奥氏体的作用,因而需要较多的能量才能促使剪切机理来产生马氏体,深冷处理就是利用过冷度来增加马氏体转变的驱动力,随着深冷温度降低,过冷度增加,马氏体转变越完全。在冷却过程中残余奥氏体向马氏体的转变速度,不取决与时间,而与过冷度有关,即残余奥氏体量只与深冷温度有关。另外,深冷处理还可以析出细小碳化物,细化组织结构。 
          深冷处理减少了残余奥氏体量,增加了芯棒在挤压过程中在亚表层萌生裂纹的难度,同时由于残余奥氏体量减少以及细小碳化物析出和组织细化,使犁削难度增加。因此,芯棒经深冷处理后,增加了抗疲劳磨损和磨粒磨损的能力,从而提高了芯棒寿命。如果深冷处理温度较高(高于-160℃),过冷度较小,残余奥氏体向马氏体的转变的能量不足,残余奥氏体量较多,表现在模具硬度几乎不变,模具寿命提高不多。在较低温度下深冷处理,只要保温时间足以使芯棒冷透(不小于2h),残余奥氏体向马氏体的转变就较为完全,但马氏体中析出的细小碳化物的量随着保温时间的延长而缓慢增加。因此,模具寿命也随保温时间延长而缓慢增加。如果考虑到随着保温时间延长,模具深冷处理的成本也增大,那么取保温时间为24h*适宜。 
          3.结语 
          粉末冶金零件整形模具的破坏机理为疲劳磨损和磨粒磨损。模具经深冷处理可以大幅度提高其寿命。深冷温度以-160℃-196℃为*佳,保温时间越长模具寿命越高,但从成本和寿命两方面综合考虑,取24h为宜。

           

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