China Carbon Steel Silica Sol Investment Casting Factory

Carbon steel Silica Sol investment castings are the custom castings produced by lost wax investment casting process (or called precision casting) of carbon steel. Cast carbon steel is the kind of cast steel with carbon as the main alloying element and a small amount of other alloy elements. They can be divided into cast low carbon steel, cast medium carbon steel and cast high carbon steel. The carbon content of cast low carbon steel is less than 0.25%, the carbon content of medium carbon steel is between 0.25% and 0.60%, and the carbon content of cast high carbon steel is between 0.6% and 3.0%. The strength and hardness of cast carbon steel increase with the increase of carbon content. Cast carbon steel has kinds of advantages such as lower production cost, higher strength, better toughness and higher plasticity. Carbon steel Silica Sol castings can be used to manufacture parts that bear heavy loads, such as tractor spare parts, railroad freight cars, automobile, steel rolling mill stands, hydraulic press bases in heavy machinery. They can also be used to manufacture parts that are subject to large forces and impact, such as wheels, couplers, bolsters and side frames on railway vehicles.

The carbon content of cast carbon steel is generally between 0.2% and 0.6%. If the carbon content is too high, its plasticity will deteriorate, and cracks are prone to occur during casting.

The grade of cast steel is composed of ZG and two sets of numbers. Among them, ZG is the code for cast steel, and the two sets of numbers after the code represent the yield strength ReL (MPa) and the tensile strength Rm (MPa). For example, ZG270-500 indicates cast steel with a yield strength of 270 MPa and a tensile strength of 500 MPa.

Different grades of cast carbon steel are used for parts with different usage requirements. ZG230-450 has certain strength and good plasticity, toughness, and weldability, and has acceptable cutting performance. It is used to manufacture parts that are not subjected to high stress and require certain toughness, such as anvil bases, bearing housings, shells, valve bodies, and base plates; ZG270-500 has higher strength and better toughness, and all the process performances are good. It is widely used and commonly used for manufacturing steel rolling machine frames, bearing housings, connecting rods, and cylinder bodies, etc.; ZG310-570 has good strength and cutting performance, lower plasticity and toughness, and is used to manufacture various mechanical parts that are subjected to high loads, such as large gears, cylinder bodies, brake wheels, and rollers; ZG340-640 has high strength, hardness, and wear resistance, poor weldability, and is often used to manufacture crane gears, rolls, ratchet wheels, and couplings, etc.

The grades, chemical composition, and properties of general engineering cast carbon steel are shown in the following table:

Grades, chemical composition and properties of general engineering cast carbon steel

In production, the requirements for cast carbon steel are to have certain mechanical properties. The main indicators of mechanical properties usually refer to strength (yield strength ReL and tensile strength Rm), plasticity (elongation A and reduction of area Z), and toughness (impact absorption energy K).

The mechanical properties of steel are determined by its microstructure, and the microstructure is basically determined by the chemical composition of the steel, the crystallization conditions, and the heat treatment temperature.

The chemical composition of carbon steel, apart from iron, mainly includes carbon, silicon, manganese, phosphorus, and sulfur. Among these five elements, carbon plays the most significant role. The amount of carbon directly affects the microstructure and mechanical properties of the steel. Cast carbon steel is classified by the different carbon contents. The mass fractions of silicon and manganese should be controlled within a certain range, and fluctuations within this range have no significant impact on the mechanical properties of the steel. Phosphorus and sulfur reduce the mechanical properties of the steel and are harmful impurities, and they need to be controlled below a certain limit.

The melting process of cast carbon steel is one of the most critical steps. To obtain qualified castings, the pouring temperature (see the table below) and pouring speed must be strictly controlled.

Cast state microstructure: The mechanical properties of carbon steel in the cast state are relatively poor, especially with low impact toughness. The reasons for the poor mechanical properties include possible casting defects (such as shrinkage cavities, porosity, gas pores, cracks, etc.), and more importantly, it is due to the shortcomings in the microstructure, mainly manifested as coarse grains and bainite. In addition, there are also internal stresses within the casting.