Degradation of alloy properties by super purification and optimum design of advanced steels by the best use of impurity elements

通过超净化降低合金性能，并通过杂质元素的最佳利用来优化设计先进钢

基本信息

批准号：
11305050
负责人：
MORINAGA Masahiko
金额：
$ 7.71万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11305050/
关键词：
impurity sulfur heat-resisting steel steam oxidation 鉄鋼材料微量元素合金設計不純物元素

项目摘要

Some of alloy properties degrade by super purification. The best use of impurity elements such as S and B is needed for the optimum design of advanced heat-resisting steels. The objective of this research is to investigate the effect of impurity elements on the steam oxidation resistance. The results on the S impurity are summarized as follows ;( 1 ) It was observed that a mass loss occurred in the advanced high Cr ferntic steels m the early stage of steam oxidation at 650℃. However, this mass loss decreased significantly in the S-containing steels.( 2 ) As S was an impurity element to segregate on the surface of the stee at 650℃ it worked to assist the Cr enrichment on the surface owing to the strong affinity of these two elements As a result, Cr_2O_3 could form easily on the steel surface in the early stage of steam oSon a far as tne steel contained S.( 3 ) S existed under the Cr_2O_3 oxide layer or at the interface between the oxide and the base steel. The existence of S at the inte … More rface suppressed severe Cr depletion under the oxide, resulting in good oxidation resistance even for a long time exposure to steam.( 4 ) It was stressed here that even Cr_2O_3 oxide specimen itself showed a mass loss after steam oxidation at 650℃. However, the S doping into Cr_2O_3 decreased such a mass loss.( 5 ) As might be expected from these results, this S effect was not remarkable in the low Cr steels (e.g., 2.25%Cr steel).The mass loss obseryed ferritic steels and Cr_2O_3 oxide during steam oxidation was interpreted as due to the formation of a volatile hydroxide, CrO_2(OH)_2, as reported previously in austltic steels. The presence of S at an impurity level probably suppressed the formation of he volatile compound. This is probably the reason why S is effective in increasing the oxidation resistance to steam but not to air. The S effect became dominant if the steels contained 50ppm S. This is an allowable amount of S since it does not degrade mechanical properties of the steels. Therefore, for the optimum design, 50〜100ppmS should remain in advanced high Cr ferritic steels. Less

高级耐热钢的优化设计需要充分利用 S 和 B 等杂质元素，从而降低某些合金的性能。本研究的目的是研究杂质元素对蒸汽氧化的影响。对S杂质的研究结果总结如下：(1)观察到先进高铬铁素体钢在650℃蒸汽氧化初期发生了质量损失。然而，在含S钢中，这种质量损失显着减少。(2)由于S是一种杂质元素，在650℃时会在钢的表面偏析，因此由于与Cr的强亲和力，它有助于表面上Cr的富集。这两种元素的结果是，只要钢中含有S，在蒸汽初期，钢表面就很容易形成Cr_2O_3。(3)S存在于Cr_2O_3下面。氧化物层或氧化物与基体钢的界面处S的存在抑制了氧化物下严重的Cr贫化，即使长时间暴露在蒸汽中也具有良好的抗氧化性。这里强调的是，即使Cr_2O_3氧化物样品本身在650℃蒸汽氧化后也出现了质量损失，但Cr_2O_3中的S掺杂减少了这种质量损失。 5) 正如从这些结果中可以预期的那样，这种 S 效应在低 Cr 钢（例如 2.25%Cr 钢）中并不显着。在蒸汽氧化过程中观察到的铁素体钢和 Cr_2O_3 氧化物的质量损失被解释为由于形成挥发性氢氧化物 CrO_2(OH)_2，如之前在奥氏体钢中报道的那样。 S 可能以杂质水平存在。抑制挥发性化合物的形成，这可能是为什么 S 能够有效提高对蒸汽的抗氧化性，但对空气的抗氧化性却无效。如果钢中含有 50ppm S，则 S 效应变得占主导地位。这是允许的 S 量，因为它是有效的。不会降低钢的机械性能，因此，为了优化设计，先进高Cr铁素体钢中应保留50~100ppmS。