SMEMACH：ADI Casting Manufacturer & Supplier
SMEMACH：ADI Casting Manufacturer & Supplier
To gain a deeper understanding of the performance and characteristics of Austempered Ductile Iron (ADI) products, we have conducted a two-year project research starting from 2023. This project focuses on six sets of steering components for heavy-duty trucks as the research objects. Through a comparative analysis of the most authentic experimental data, it demonstrates the process of product performance enhancement, aiming to provide strong support for global ADI customers in product iteration and upgrading or new product design.
This product weighs approximately 200KG and adopts the coated sand shell molding casting process. This process offers the following significant advantages:
Coated sand shell molding casting can effectively avoid casting defects and enhance product quality. It improves the appearance quality of the rough casting, reduces the machining allowance, increases the process yield, and ensures stable quality.
The rapid cooling rate during the pouring of coated sand molds significantly optimizes the graphite morphology of the castings, thereby improving the mechanical properties of the products and extending their service life.
Coated sand is particularly suitable for the production of complex thin-walled precision iron castings and high-demand iron castings. It effectively eliminates casting defects such as sand adhesion, deformation, hot cracking, and porosity.
The coated sand shell molding casting process results in smoother surfaces and more precise dimensions for the castings, reducing or eliminating the need for mechanical processing. This shortens the production cycle, saves metal materials, and reduces costs.
Castings produced using the shell molding line exhibit high geometric and dimensional accuracy, significantly reducing casting defects, lowering the rejection rate, improving surface quality, and reducing the amount of machining required.
In summary, this product, utilizing the coated sand shell molding casting process, features stable product quality, a low defect rate in castings, and high dimensional accuracy in casting.
The critical aspect of Austempered Ductile Iron (ADI) products lies in the adoption of the austempering heat treatment process. The treated products exhibit the following main characteristics:
Austempering yields a lower bainite structure, which significantly improves the strength, hardness, toughness, wear resistance, and plasticity of the steel.
Austempering reduces the temperature difference between the workpiece and the quenching medium, thereby lowering the quenching thermal stress. Simultaneously, the specific volume of bainite is smaller than that of martensite, and the temperature inside and outside the workpiece is relatively consistent, resulting in lower quenching organizational stress. This significantly reduces the tendency of the workpiece to deform and crack.
Austempering offers superior impact toughness compared to ordinary quenching-tempering (medium and low-temperature tempering), especially for steels with significant first-class temper brittleness.
After austempering, the organizational structure is uniform, with minimal internal stress and a very low likelihood of micro and ultra-micro cracks. Consequently, the fatigue strength significantly increases after austempering, extending the service life of the castings.
Both thermal and organizational stresses are significantly reduced during austempering. During isothermal holding, the stabilization of austenite increases the amount of retained austenite during subsequent cooling, resulting in minimal deformation, even achieving deformation-free quenching. This makes it suitable for some precision structural parts.
Compared to conventional quenching and tempering, austempering achieves the specified hardness with higher plasticity and impact toughness, along with minimal deformation. This saves man-hours and energy, reducing costs.
The austempering process improves the organizational structure and mechanical properties of ductile iron castings, providing them with higher strength and toughness, thereby enhancing the overall utilization of the material.
In summary, the austempering heat treatment process offers significant advantages in enhancing material performance, reducing deformation and cracking, and reducing product weight. It is particularly noteworthy that the technical parameters, temperature, and process time control of heat treatment require operation by experienced technical engineers. After years of experimentation and summarization, our company selects the optimal heat treatment scheme based on different raw materials and product design complexities.
After heat treatment, the cast products undergo surface treatment, and we then conduct mechanical performance testing experiments and data analysis using test bars from the same heat treatment batch.
Austempered Ductile Iron (ADI) products possess the following distinctive characteristics compared to cast products of low-alloy steels and forged products of alloy steels:
Under the same elongation conditions, the tensile strength of ADI is twice that of ordinary ductile iron. Under the same tensile strength conditions, the elongation is more than twice that of ordinary ductile iron. The tensile strength of ADI also surpasses that of quenched and tempered carbon steel and is comparable to that of low-alloy steel.
Due to the nearly 10% graphite content in ADI, parts of the same volume are approximately 10% lighter than forged steel, aiding in reducing the overall weight of the machine and decreasing fuel and power consumption.
ADI exhibits high bending fatigue strength and contact fatigue strength. Its rotational bending fatigue strength can reach 400-500MPa, comparable to that of quenched and tempered low-alloy steel. Its contact fatigue strength can reach 1600-2100MPa, higher than that of nitrided low-alloy steel.
ADI has a low elastic modulus, and the presence of graphite spheres in the matrix rapidly absorbs vibrations and increases noise damping, making the operation of components quieter and smoother.
With a hardness of 302-375HBW, its lifespan exceeds that of forged steel with a martensite structure and a hardness of 58-62HRC. CADI (containing 18% carbides) exhibits superior wear resistance to many high-alloy wear-resistant cast irons, while its notch-free impact toughness is 2-10 times that of wear-resistant cast irons.
These characteristics make Austempered Ductile Iron widely used internationally in industries such as automotive, heavy-duty trucks, industrial and construction mining equipment, agricultural machinery, railways, general machinery, wind power and energy equipment, and military and defense. Once you understand its characteristics, you will find it to be a highly ideal material choice.
This experiment was divided into two stages, conducted in 2023 and 2024, respectively.
The raw material for the heavy-duty truck steering casting suite subjected to the experiment was ductile iron with the grade QTD1050-700-6. The material properties were as follows: tensile strength ≥1050MPa, yield strength ≥700MPa, and elongation ≥6%.
The 2023 experimental data showed that after adopting the ADI process, the yield strength, tensile strength, elongation after fracture, and impact strength of the raw material were all enhanced. These data met the customer's requirements. Subsequently, we improved the raw material formulation and heat treatment process, and the 2024 experimental data are as follows:
From the 2024 experimental data, it can be observed that the mechanical properties of the second test bar showed significant improvements in tensile strength, elongation after fracture, and impact strength.
We conducted low-temperature experiments on the test bars, performing low-temperature tensile tests and low-temperature impact tests at -41°C. The data results are as follows:
The experimental results proved that ADI material still possesses extremely strong mechanical properties under low-temperature conditions. The tensile strength increased (from 1181 MPa at room temperature to 1242 MPa), while the elongation was minimally affected by low temperature (decreasing from 13.5% at room temperature to 12%). The impact strength decreased from 95J before the experiment to 65.5J, showing a significant decline (the room temperature requirement for impact strength is 80J).
The overall experimental results far exceeded the standards, and the customer was highly satisfied. Subsequently, we referenced the European Austempered Ductile Iron (ADI) standard ASTM A897 and compared it with the requirements for ductile iron with the grade QTD1200-4 at room temperature.
At -41°C, the comparison of our product's mechanical performance experimental data showed that the elongation after fracture was three times higher than the standard, reaching 12, while the tensile strength and impact strength met the material standard requirements.
Each set of authentic experimental data is our precious asset, the cornerstone of our continuous exploration, and an important basis for customers to confidently select and accept our products. We have been constantly exploring. The Chinese Austempered Ductile Iron (ADI) standard was introduced in 2009, and we have already mastered the core process control procedures.
The Austempered Ductile Iron (ADI) market is vast, with wide-ranging industry applications. We will continue to conduct in-depth research in this field and welcome you to contact us for technical exchanges. Let's jointly advance ADI technology and bring greater progress to humanity.
GB/T 24733-2023: ADI Adds QTD1600-1 Grade
ADI China International Standard-GB/T 24733-2023
ADI (Austempered Ductile Iron) : the "Wolverine" blade in the logging industry
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