新合金9Cr-1Mo-V
New Alloy 9Cr-1Mo-V

　　由于电厂压力（高达4100 psi）和温度（高达593^oC），因此对更有效的新合金9Cr-1Mo-V的需求越来越多，和F22甚至SS316相比，这种新合金具有更高的抗蠕变强度，越来越多的在管道、阀门和联接件上采用。由于减少了管壁的厚度，成本也因此大幅减少。ASME所允许的应力如表1所示。
　　As power plants pressures (up to 4100 psi) and temperatures (up to 1100^oF (593^oC)) are being steadily raised to increase efficiency a new alloy 9Cr-1Mo-V with higher creep strength then F22 or even SS316 has been introduced for pipes, valves and fittings. Large savings can be achieved in piping because of reduced wall thickness. The ASME allowable stresses are shown in Table 1.

在538^oC下，F91锻件具有：
(a) 承受应力比铸件高出18.5%。
(b) 比F22或WC9高出127%
At 1050^oF (538^oC) F91 Forgings have:
(a) 18.5% higher allowable stress than casting.
(b) 127% higher than F22 or WC9.

铸件9Cr-1Mo-V
Castings in 9Cr-1Mo-V

　　直到2001年六月ASME才分配一个级别。铸件被列为ASME法典第2191-21款。ASME级是A217 C12A。
　　have not been yet (June 2001) assigned a grade by the ASME. The castings are ordered to the ASME code case 2192-21. The ASTM grade is A217 C12A.

图1：没有铁氧体或块状碳化物 (100X)⁽¹⁾的
可接受铸件微观结构
Figure 1: Acceptable microstructure of castings
without ferrites or blocky carbides (100X)⁽¹⁾

浇铸铸件工艺过程的难度
Difficult Processing Issues In Pouring Castings

　　9CR-1MO-V合金优异的高温性能依赖于包含亚微观碳化物的特殊微观结构（图1）的形成。这些都受到脱氧工艺、热处理、焊接法和PWHT的影响。如果这些工艺过程没有正确进行，即使成分和室温机械特性都符合要求，也不会实现所需要的蠕变特性。⁽¹⁾
　　The excellent high-temperature properties of 9CR-1MO-V alloys depend on the formation of a particular microstructure (Fig. 1) containing submicroscopic carbides. This is affected by the deoxidation practices, heat-treatment, the welding process and PWHT. If those processes are not properly executed, the required creep properties will not be realized even though the composition and room temperature mechanical properties will apear acceptable.⁽¹⁾

脱氧
Deoxidation

　　为了在浇铸之前消除熔化金属中的溶解氧，需要在金属中添加具有很高的氧亲合力的元素，如钛，钒，铌和镁。正确的工艺过程（是很难实现的），可以保证最后能被接受的均衡微观结构和所期待的高温蠕变强度。
　　To remove dissolved oxygen in the molten metal prior to pouring, elements have been added which have high affinity for oxygen such as titanium, vanadium, niobium and magnesium. The proper processing, which is difficult, can assure the final acceptable proportion microstructure (Fig. 1) and the expected high-temperature creep strength.

热处理
Heat Treatment

　　高温处理也是关键的，并需要进行严格的控制，才能够保证适当的微观结构。
　　The HT procedure is also critical and requires strict controls to ensure the proper microstructure.

通过焊接改进铸件的性能很难达到X射线的质量要求⁽¹⁾
Difficulties In Upgrading of Castings
by Welding to Meet X-Ray Quality⁽¹⁾

　　高铬含量（9%）能够提供很高的硬化性。因此在焊接部位和热影响区域（HAZ）形成马氏体就需要正确的精密的PWHT工序。需要适当的程间温度和正确选择填充金属材料来防止冷热裂缝，产生适当的蠕变阻力和韧性。
　　The high chrome content (9%) provides very high hardenability. Consequently martensite will form in the welds and heat affected zone (HAZ) requiring proper and precise PWHT procedures. The proper interpass temperature is required to prevent cold and hot cracking as well as the proper selection of welding filler material, to produce the proper creep resistance and toughness.

图2：不可接受的微观结构铸件，
带有大块白色铁素体区域 (200X)⁽¹⁾
Figure 2: Unacceptable microstructure in castings
with large white ferrite areas. (200X)⁽¹⁾

1. 在关键的脱氧过程中，高亲合力元素也会结合氮，并且阻止在热处理过程中形成细密的铌碳氮化物，而这是高温特性的基础。⁽¹⁾
   During the critical deoxidation the high affinity elements can also combine with nitrogen and prevent during the heat treatment the formation of fine niobium carbonitrides which are essential for the high temperature properties.⁽¹⁾
2. 如果在X射线改进或制造过程和PWHT中，材料没有正确熔化、热处理、焊接，则铸件将会缺乏高温特性。⁽¹⁾
   If the material is not properly melted, heat treated, welded during X-Ray upgrading or during manufacturing and PWHT the casting will lack the high temperature properties.⁽¹⁾

⁽¹⁾参考文献：Donald R. Bush (Fisher) 在《阀门》杂志2001年冬季卷3。
⁽¹⁾References: Donald R. Bush (Fisher) article in Valve magazine Volume 13, Winter 2001.