Vermicular graphite cast iron and manufacturing process thereof

Abstract

The invention relates to vermicular graphite cast iron and a manufacturing process thereof. The manufacturing process sequentially comprises the steps of furnace charge preparation, iron liquid smelting, vermicularizing treatment and casting pouring. In the vermicularizing treatment process, vermicularizer partners are added, and comprise the following elements in parts by weight: 11 to 14 parts of Ca, 4 to 7 parts of Ba, 18 to 23 parts of Sb or Bi, 5 to 8 parts of C, 43 to 48 parts of Si and 9 to 13 parts of Fe. The obtained vermicular graphite cast iron is low in chilling tendency and high in ductility and toughness, and the slenderness ratio of vermicular graphite is lower (namely the vermicular graphite seems thick). The vermicularizing effect of the vermicular graphite cast iron is improved, and a vermicularizing rate range is reduced.

Description

technical field [0001] The invention relates to a vermicular graphite cast iron and a manufacturing process thereof. Background technique [0002] Vermicular graphite cast iron (hereinafter referred to as vermicular iron) is an engineering material that began to be applied in the 1970s, but the development speed in the past 40 years is not as fast as that of ductile iron. One of the important reasons affecting the development of vermicular iron is that the range of creep rate is difficult to control. [0003] Both the ISO standard and the national standard define the creep rate ≥ 80% as vermicular graphite cast iron, but also point out that since the cooling rate has a great influence on the creep rate, it is not always required for each casting that the creep rate is everywhere It is more than 80%, and the best creep rate can be determined according to the structure and actual use of the casting. [0004] However, there are two major problems in the existing technology: a...

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Problems solved by technology

[0004] However, there are two major problems in the existing technology: a) The creep rate range is difficult to control. Under the same production conditions, the creep rate difference (extreme difference) between different treatment packages may reach 50~70%, and the allowable extreme The difference should be ≤30%; b). It is difficult to obtain a high creep rate. Many important creep iron parts such as automobile engine cylinder blocks and cylinder heads require a creep rate of ≥70% or even ≥80%.

At the same time, the decline time of the existing creeping technology is relatively short, resulting in a lot of molten iron that cannot be cast before the decline and can only be returned to the furnace for resmelting

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