Standards Development

Scope

This document specifies the test principle, sampling, apparatus, condition, procedure, data processing, and test report for penetration strength of grey cast irons and compacted (vermicular) graphite cast irons grade ISO 16112/JV/400 to ISO 16112/JV/500.

Purpose

Grey cast iron, as an important metal material, plays an irreplaceable role in China's industrial sector. According to the statistics, the global casting output in 2022 reached 51,79 million tons, of which grey cast iron accounted for 21,20 million tons, representing 41% of the total casting output. Grey cast iron is characterized by excellent casting process performance, good heat conductivity, vibration damping , and wear resistance properties. It is suitable for casting complex structures or thin-walled castings. Gray cast iron parts are widely used in the automotive industry, construction machinery, mining machinery, rail transit, petrochemical industry, and other fields.

Currently, in developed industrial countries, tensile strength and hardness are generally used to evaluate the main mechanical properties of grey cast iron. The wedge penetration strength test method, as a means of assessing the hardness and strength of cast iron materials, has been widely adopted globally, especially in the automotive industry. The wedge penetration strength test method offers the following advantages:

(1) Direct Sampling: The test samples for wedge penetration strength are taken directly from the body of the cast iron part itself, eliminating the need to cast separate test blocks. This avoids performance differences between the test blocks and the cast iron body due to factors such as chemical composition and cooling conditions, allowing for an accurate evaluation of the strength and hardness of the cast iron body.

(2) Convenient Operation: When size limitations of the casting blank or prior machining of the casting prevent taking tensile test samples from the body, wedge-shaped penetration strength test blocks can be prepared for testing, to evaluate the mechanical properties of the cast iron part conveniently, without requiring equipment such as tensile testing machines.

(3) Low Cost: The sample volume used for wedge penetration strength testing is small, resulting in low preparation costs and ease of processing.

In 1934, Dr. Ludwig and Dr. Christoph in Vienna, Austria, discovered a direct relationship between the force required to cut a grey cast iron sample with two opposing blades and its tensile strength. Currently, the wedge penetration strength test method is widely used to test the strength and hardness of grey cast iron in many countries around the world, including China, Germany, the United States, the United Kingdom, and Austria. Relevant standards or specifications from various countries include:

Germany's VDG standard (Keildruckpruefung, VDG-merkblatt P-340), German standard TGL 14401/04, Austrian standard Pruefvorschrift No.42, Chinese national standard GB/T 38440—2019 Test Method for Wedge penetration Strength and its English version. Germany has incorporated the wedge compression strength test into the DIN EN 1561:2023 Founding - Grey Cast Iron standard.

However, there is no such International Standard, and no unified specification has been established. Due to technical differences and the background of standard formulation between countries, the wedge compression strength test results and the conversion relationship between wedge compression strength and tensile strength differ among countries, making it difficult to serve as a unified criterion for international trade.

China has conducted in-depth research on the basic theory of wedge compression strength and accumulated a large amount of experimental data, leading to the publication of the GB/T 38440—2019 Test Method for Wedge Compression Strength. China has overcome various challenges in developing the test apparatus through thorough research and analysis of test principles, precision-influencing factors, algorithm derivation of test relationships, experimental validation of related technical solutions, and studies on and validation of the test apparatus. These efforts have established a linear relationship between wedge compression strength and tensile strength, accurately evaluating the mechanical properties of cast iron components.

This standard provides a convenient test method for inspecting the mechanical properties of cast iron materials, guides the processes and product design of cast iron materials. This standard is significant for promoting the theoretical research and application of wedge compression strength in cast iron materials, promoting international exchange and cooperation.