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铸体检验实践中时有灰铸铁牌号与硬度牌号相矛盾的现象,即其中一种牌号合格,而另一种牌号不合格,由此而产生供需双方发生异议,究其原因,实属牌号选择不当。灰铸铁的抗拉强度与硬度之间存在一定的函数关系,若孤立地选择牌号势必产生上述现象。本文以GB9439-88《灰铸铁体》为基础,简述灰铸铁牌号和硬度牌号的选择。1 牌号选择 1.1按灰铸铁件主要工作壁厚的抗拉强度（σ_b）选择牌号 灰铸铁体的抗拉强度与铸件壁厚有关（壁厚效应）,同一牌号的灰铸铁件不同壁厚处会得到不同的抗拉强度。按灰铸铁体主要工作壁厚设计和使用要求给出的抗拉强度（σ_b）,结合表1,即可选出灰铸铁牌号,若能实测主要工作壁厚的抗拉强度,继而修正牌号,将可较准确地选定牌号。
Casting inspection practice, there are gray cast iron grades and hardness of the contradictory phenomenon, that is, one of the grades pass, and the other grades failed, resulting in both supply and demand objections, the reason, it is the choice of grades improper. There is a certain functional relationship between the tensile strength and the hardness of gray cast iron. If the grade is selected in isolation, it is bound to produce the above phenomenon. In this paper, GB9439-88 “gray cast iron” based on gray cast iron grade and hardness grades of choice. 1 grade selection 1.1 The main work of gray cast iron wall thickness of the tensile strength (σ_b) selection of grades Gray cast iron body tensile strength and casting wall thickness (wall thickness effect), the same grade gray iron castings of different thickness will Get different tensile strength. According to the main work of gray cast iron wall thickness design and use requirements given by the tensile strength (σ_b), combined with Table 1, you can choose the gray cast iron grades, if we can measure the tensile strength of the main wall thickness, and then amend the grade, Will be able to select the grade more accurately.