What are the basic characteristics of gray cast iron? And what precautions should be taken during machining?

What are the basic characteristics of gray iron? What precautions should be taken during machining?

For gray iron casting manufacturers, the inherent characteristics of the product cannot be overlooked. Below is an introduction to the basic properties of gray iron.

This product has a relatively high clay content but a low water content. During the sand-mixing process, it's important to pay attention to both the silt content and the clay content. If the clay content exceeds that of the sand, the pull-out strength performance will be enhanced.

Normally, we should keep the effective bentonite content between 7% and 10%. The total amount of clay and available clay in the molding sand should be maintained at the same level as the silt content.

Secondly, anyone looking to purchase gray iron castings—whether for production purposes or not—should pay close attention to the product's moisture content. Moisture is one of the key factors determining the product's adhesion and plasticity. If the moisture level is relatively high, it can also cause fluctuations in the clay bonding strength, leading to reduced flowability of the molding sand. Moreover, excessively low moisture levels may result in brittleness and certain defects in the final product.

The machining process for gray iron castings is relatively simple. Laser surface treatment and casting surface alloying technologies can create a metallurgically bonded alloy layer on the surface of ordinary castings, endowing them with enhanced, composite properties—and have already yielded remarkable results. Strengthening and refining are the future directions for gray iron development in China. Thin-walled, lightweight, and tough gray iron materials are specifically designed to meet the engineering community's growing demands for energy efficiency and the recyclability of engineering materials, while also addressing society's increasing emphasis on environmental sustainability and green practices. Moreover, all gray iron products processed through specialized manufacturing techniques exhibit notable features such as refined graphite structure, uniform microstructure, and exceptional strength, making them perfectly suited for a wide range of construction applications.

Casting manufacturers employ resin sand and lost-foam casting in the production of gray iron. Various casting defects frequently occur during the manufacturing process of gray iron. How to prevent these defects has always been a key concern for casting companies. Let’s take a look at the details below.

During the gray iron casting process, significant amounts of gas are generated as surface data vaporize—especially at the moment when molten metal comes into contact with the foam plastic. Whenever possible, opt for bottom-pouring ladles. These ladles minimize heat loss of the molten metal, provide a higher pouring head, and enable faster pouring speeds. As a result, slag floats on the surface of the molten metal, leading to cleaner steel during casting. Due to equipment limitations, smaller and medium-sized machine tool castings that have lower or moderate quality requirements can also be outsourced. Additionally, carefully control the content of gas-generating substances in both molding sand and core sand; ensure that the moisture level in wet molding sand doesn’t exceed the optimal range. When preparing molds and finishing patterns, avoid using excessive amounts of release agents or water. Core boxes must be thoroughly dried, and once dried, cores should not be stored for extended periods. Cores intended for use the following day must be reheated in the furnace before being employed, to prevent moisture absorption. Furthermore, never use cold irons or core supports that have become damp or rusty.

We are Manufacturers of gray iron casting—feel free to contact us if you'd like to learn more about this topic. We can provide insights from various perspectives.