The axle housing is mainly composed of sand casting raw materials

Steel contains no other alloy elements except carbon and a certain amount of silicon and manganese alloy elements for deoxidation. This kind of steel has large output and wide application. It is mainly used for manufacturing parts and components of general structure and mechanical structure, building structural parts and pipelines for conveying fluid. According to the use requirements, it sometimes needs to be used after heat treatment (normalizing or quenching and tempering), which has excellent mechanical properties. Zg40mn is used as the material of sand casting axle housing, which is widely used in mechanical structural parts. The parts are normalized + tempered by heat treatment, and its chemical composition and mechanical properties meet the requirements. The mechanical properties are not less than 295 MPa of yield strength, 640 MPa of tensile strength, 12% of elongation and 30% of reduction in area. The material is suitable for processing parts under high pressure and bearing friction and impact. The hardness of the material is in the range of hb163-200.

For cast steel for sand casting, its main raw materials include waste steel, ferrosilicon, ferromanganese and aluminum alloy deoxidizer, and the main auxiliary material is silica sand. The furnace mixing and batching process is an important link in molten steel smelting. The proportion of material components in smelting has an important impact on the mechanical properties of products. Strictly controlling the raw materials can reduce or avoid the occurrence of shrinkage cavity and porosity. Selecting good auxiliary materials can improve the surface quality of sand casting axle housing.

Selection of raw materials for sand casting

(1) Scrap steel is the main raw material for smelting sand castings. Two samples are randomly selected for chemical composition inspection in each batch. Scrap steel can be divided into high manganese steel and low manganese steel according to manganese content. Inspection according to the size and specification of scrap steel: medium scrap is all kinds of steel trimming, ship plate, steel castings and all kinds of mechanical scrap with overall size ≤ 1000 500 300 mm, thickness ≤ 6 mm and unit weight ≤ 5 kg. Small scrap includes various steel trimming, ship plate, steel casting and various mechanical scrap with overall size ≤ 1000 500 300 mm, thickness ≤ 4mm and unit weight ≤ 2 kg. The unified wastes are leftover materials with thickness ≤ 4 mm and weight less than 2 kg. The scrap steel shall be inspected with a magnifying glass to detect the following contents:

Shape and size acceptance rules: shape and size are regular and uniform. Super large, super long and overweight scrap shall not be used as raw materials, and steel sheet less than 2 mm shall not be used.

Scrap steel for sand casting shall not be mixed with ferroalloy, nonferrous metals and other impurities, and there shall be no mud, cement, sticky sand, rubber, etc. on the surface. The oil stain on the surface of scrap steel shall be removed. Tubular objects with closed ends, closed vessels, inflammables and explosives, radioactive and toxic substances are not allowed in scrap steel. Complete sets of machinery, equipment and structural parts are not allowed in waste steel.

(2) The main function of ferrosilicon for sand casting is to adjust the silicon content in zg40 Mn. Its brand is fesi75a11 5-b, the affinity between silicon and oxygen is large. Generally, it is added 10 min before tapping after the deoxidizer is used. The composition requirements are that the silicon content is between 72-80% and the aluminum content is not more than 1%. The control requirements for harmful elements such as sulfur and phosphorus must be strictly controlled below 0.02%. Generally observe the following through a magnifying glass:

The number of ferrosilicon blocks with a weight greater than 20kg for sand casting shall not exceed 10% of the batch weight, and the fragments shall not exceed 10% of the batch weight. The surface of ferrosilicon shall be clean without obvious slag, sand and other inclusions.

(3) High carbon ferromanganese is mainly used to adjust the content of manganese in the composition, and its material brand is femn68c7 0, the affinity between manganese and oxygen is greater than that of iron. Ferromanganese shall be put into it together with the slag after the formation of thin slag. The ferromanganese adjusted in the later stage of reduction shall be added 10 minutes before tapping. The content of its chemical composition shall be controlled to be between 62-75% of manganese. The content of sulfur and phosphorus shall be strictly controlled, in which the content of s shall not exceed 0.03%.

Observe the following through a 10x magnifying glass: the single weight of ferromanganese block shall not be greater than 40kg. The particle size range is 30-250 mm. The surface quality shall be clean without impurities and foreign inclusions.

(4) Silicon aluminum ferroalloy is a deoxidizer used in steelmaking production. It improves the morphology of inclusions and reduces the content of gas elements in molten steel. It is an effective means to improve the quality of molten steel, reduce the cost and save aluminum.

The surface quality of the alloy shall be clean without obvious bubbles, non-metallic inclusions and other impurities. Its aluminum content is controlled at 35-55%.

Composition requirements for auxiliary materials of sand casting

The quality requirements of silica sand shall comply with the standard GB / T 9442-1998 silica sand for sand casting. The silica sand shall be inspected by the molding sand detector as follows: suitable particle shape: 30 ~ 80% of round sand: the particles are spherical or close to spherical, with smooth surface and no redundant edges and corners. 15 ~ 25% particles of polygonal sand are polygonal and mostly obtuse. The sharp angle sand shall be controlled below 5%, and the particles are sharp angle with many acute angles. Mud, stone, steel slag, plastic and other sundries are not allowed in the silica sand to avoid affecting the molding sand.