Machine tools are assembled from many parts, casting bed is a large category, broadly refers to large iron parts.
Commonly used casting grades are HT200, HT250, HT300, the higher the grade, the lower the carbon content and silicon content, the better the mechanical properties such as strength, hardness, wear resistance, etc.
According to the market positioning of the machine tool, economical CNC machine tools we generally purchase HT250 cast iron, while high-precision models use HT300 cast iron manufactured by Mihanna process.
Mihanna castings have a variety of advantages, including:
High strength: Mihanna castings have excellent strength and hardness, and can withstand high stress and heavy load.
Wear resistance: Castings are specially treated, with excellent wear resistance, and can be used for a long time without damage in harsh friction environments.
Corrosion resistance: Mihanna castings have good corrosion resistance media properties and can be used for a long time in wet or chemical corrosion environments without being affected.
Dimensional stability: Through strict production process and material control, Mihanna castings have high dimensional stability, which can ensure dimensional accuracy at different temperatures and working conditions.
Excellent mechanical properties: Mihanna castings have excellent mechanical properties, including good tensile strength, modulus of elasticity and ductility, suitable for a variety of complex applications.
Good machining: Mihanna castings because of uniform organization, stable performance, with good machining, easy to cut, grinding, drilling and other machining.
Strictly speaking, castings will produce internal stress in the production process, causing bed deformation and affecting machine tool accuracy. In the past, the traditional method of eliminating stress was natural aging, and castings needed to be placed outdoors for at least 18 months, in the sun and rain. However, due to the increase in market demand, fewer and fewer manufacturers are willing to carry out natural aging. Our factory’s linear guide rail machine tool model, castings after secondary tempering to eliminate stress, and then placed outdoors for 4 months. For hard rail machine tool castings, the time can range from 12 to 18 months, the reason is also very simple, the current sales of linear guide rail machine tools are higher.
At present, secondary tempering is the fastest way for casting manufacturers to eliminate stress, but due to cost considerations, the secondary tempering process of many casting manufacturers may not meet the standard. Usually, the heating speed of the tempering process is 20 ° ~ 50 ° / hour, the constant temperature between 500 ° ~ 600 ° is 4 hours, and the cooling speed is 20 ° ~ 50 ° / hour.
The structural design of castings also plays a certain role in reducing internal stress, including reasonable reinforcing rib arrangement and appropriate casting thickness in key positions.
In summary, once the machine tool industry expands its scale to do batch, it indicates that the quality is uncontrollable, and it is crucial for the choice of manufacturers to choose to earn more money or adhere to the original intention to give dignity to each machine tool so as to win the respect of customers in the product link.
