耐热钢（耐热合金）和高温合金的含义

摘要：<p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">耐热钢（耐热合金）和高温合金的含义</span></span><span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><br /> </span><span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">先来说耐热钢和耐热合金。这两者的區(qū)别并没有(yǒu)明确的规定，通常将合金元素含量小(xiǎo)于</span>50%<span style="font-family:宋體(tǐ);">的称為(wèi)耐热钢，合金元素含量大于</span><span style="font-family:Calibri;">50%</span><span style="font-family:宋體(tǐ);">的，叫做（铁基）耐热合金。两者的分(fēn)别主要在于合金元素含量。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">再来说耐热钢和高温合金。耐热钢是指具有(yǒu)良好的高温抗氧化性和高温强度的钢。耐热钢和耐热合金在较高载荷下的*高使用(yòng)温度一般只能(néng)达到</span>750<span style="font-family:宋體(tǐ);">℃～</span><span style="font-family:Calibri;">850</span><span style="font-family:宋體(tǐ);">℃。对于更高温度下使用(yòng)的部件，则采用(yòng)镍基、钴基及难熔金属為(wèi)基的高温合金。两者的分(fēn)别主要在于耐高温温度范围。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:Calibri;font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;mso-fareast-font-family:宋體(tǐ);"><span style="font-family:宋體(tǐ);">高温工况对金属的耐热性提出了什么挑战？耐热性具體(tǐ)的含义？</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属材料的耐热性包含高温抗氧化性和高温强度两个方面。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;">①<span style="font-family:Calibri;">&nbsp;</span><span style="font-family:宋體(tǐ);">高温抗氧化性</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属的高温抗氧化性是指钢在高温条件下对氧化作用(yòng)的抗力，是钢能(néng)否持久地在高温下工作的重要保证条件</span></span><span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">氧化是一种典型的化學(xué)腐蚀，在高温空气、燃烧废气等氧化性气氛中，金属与氧接触发生化學(xué)反应即氧化腐蚀，腐蚀产物(wù)</span>(<span style="font-family:宋體(tǐ);">氧化膜</span><span style="font-family:Calibri;">)</span><span style="font-family:宋體(tǐ);">附着在金属的表面。随着氧化的进行，氧化膜厚度继续增加，金属氧化到一定程度后是否继续氧化，直接取决于金属表面氧化膜的性能(néng)。如果生成的氧化膜是致密、稳定的，与基體(tǐ)金属结合力高，氧化膜强度较高，就能(néng)够阻止氧原子向金属内部的扩散，降低氧化速度，否则会加速氧化，使金属表面起皮和脱落等，导致零件早期失效。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">钢表面氧化膜的组成与温度有(yǒu)关，在</span>570<span style="font-family:宋體(tǐ);">℃以下，氧化膜由</span><span style="font-family:Calibri;">Fe2O3+Fe3O4</span><span style="font-family:宋體(tǐ);">组成，比较致密，能(néng)有(yǒu)效地阻碍氧的扩散，抗氧化性较好。大于</span><span style="font-family:Calibri;">570</span><span style="font-family:宋體(tǐ);">℃加热，氧化膜由</span><span style="font-family:Calibri;">FeO+Fe2O3+Fe3O4</span><span style="font-family:宋體(tǐ);">组成，靠近钢表面的是</span><span style="font-family:Calibri;">FeO</span><span style="font-family:宋體(tǐ);">，向外依次為(wèi)</span><span style="font-family:Calibri;">Fe3O4</span><span style="font-family:宋體(tǐ);">和</span><span style="font-family:Calibri;">Fe2O3</span><span style="font-family:宋體(tǐ);">，</span><span style="font-family:Calibri;">FeO</span><span style="font-family:宋體(tǐ);">疏松多(duō)孔，占整个氧化膜厚的</span><span style="font-family:Calibri;">90%</span><span style="font-family:宋體(tǐ);">左右，金属原子和氧原子很(hěn)容易通过</span><span style="font-family:Calibri;">FeO</span><span style="font-family:宋體(tǐ);">层扩散，加速氧化。高温下</span><span style="font-family:Calibri;">FeO</span><span style="font-family:宋體(tǐ);">的存在，钢的抗氧化性大大下降，而且温度越高，原子扩散越快，氧化速度越快。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">提高钢的抗氧化性主要途径是合金化，在钢中加入</span>Cr<span style="font-family:宋體(tǐ);">、</span><span style="font-family:Calibri;">Si</span><span style="font-family:宋體(tǐ);">、</span><span style="font-family:Calibri;">Al</span><span style="font-family:宋體(tǐ);">等合金元素，使钢在高温与氧接触时，优先形成致密的高熔点氧化膜</span><span style="font-family:Calibri;">Cr2O3</span><span style="font-family:宋體(tǐ);">、</span><span style="font-family:Calibri;">SiO2</span><span style="font-family:宋體(tǐ);">、</span><span style="font-family:Calibri;">Al2O3</span><span style="font-family:宋體(tǐ);">等，严密地覆盖住钢的表面，阻止氧化的继续进行。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;">②<span style="font-family:Calibri;">&nbsp;</span><span style="font-family:宋體(tǐ);">高温强度</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;">&nbsp;<span style="font-family:宋體(tǐ);">金属的高温强度是指金属材料在高温下对机械载荷作用(yòng)的抗力，即高温下金属材料抵抗塑性变形和破坏的能(néng)力。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属在高温下表现出的力學(xué)性能(néng)与室温下有(yǒu)较大的區(qū)别，当工作温度大于再结晶温度后，金属除了受外力作用(yòng)产生了塑性变形和加工硬化外，还会发生再结晶和软化过程，因此在室温下能(néng)正常服役的零件就难以满足高温下的要求。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属在高温下的力學(xué)性能(néng)与温度、时间、组织变化等因素有(yǒu)关。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属在高温下工作常会发生</span>“蠕变”现象，即当工作温度大于再结晶温度时，工作应力超过该温度下的弹性极限时，随时间的延長(cháng)金属发生缓慢变形的现象。金属对蠕变的抗力越大，其高温强度也越高。</span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属的高温强度一般用(yòng)蠕变极限和持久强度来表示。蠕变极限是指金属在某温度下，经过一段时间后，其残余变形量达一定数值时的应力值。持久强度是指在恒定温度下经过一定时间，金属材料发生断裂破坏时的应力值。</span></span> </p> <p style="margin:0pt;"> <span style="font-family:宋體(tǐ);font-size:10.5pt;mso-spacerun:&quot;yes&quot;;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0000pt;"><span style="font-family:宋體(tǐ);">金属材料在高温下晶界强度低于晶内，因此加入合金元素提高再结晶温度，形成稳定的特殊碳化物(wù)，以及采用(yòng)粗晶材料，减少晶界等都能(néng)有(yǒu)效地提高钢的高温强度。</span></span> </p>