High Chromium Steel Sand Casting

Usually a certain element (except iron) becomes high alloy steel when the proportion in steel exceeds 10%. High chromium alloy steel refers to alloy steel with a chromium content of more than 10%.High chromium sand cast iron generally has high hardness and high wear resistance, and high chromium alloy steel is often used as raw material for bearing steel, hammer head, lining plate and other steel.

Product Description

1. Implementation standards: The company strictly implements ISO9001 & TS 16949 certification.

2. Material standards for Alloy steel sand casting products: ISO, GB, ASTM, SAE, ISO, EN, DIN, JIS, BS

3. Main process: sand casting, deburring, sand blasting, machining, heat treatment, leak testing, surface treatment, etc.

4. Available materials: high chromium steel, high manganese steel, alloy steel, gray iron, ductile iron, cast iron, cast steel, cast aluminum, cast copper, etc. can be customized according to customer requirements.

Casting Process of High Chromium Cast Iron

Chemical composition design of high chromium cast iron: (generally hypoeutectic high chromium cast iron is used).

1.In the process, the number of carbides is often changed by adjusting the carbon content.

2. For high-chromium cast iron without other alloying elements, the maximum diameter that can be hardened by air quenching is 20mm. To improve the hardenability, alloying elements must be added.

3. Manganese drastically reduces Ms, which will cause high chromium cast iron to have more retained austenite after quenching. Therefore, it is generally controlled below 1.0%.

4. The reduction of Ms by copper will cause a lot of retained austenite. Therefore, it is generally controlled below 1.5%.

5. Due to the high price of V, it is usually only suitable for castings that are not easy to heat treat.

6. The increase of Ms in silicon will reduce the retained austenite and reduce the hardenability. Therefore, it should generally be controlled.

7. The melting temperature of high-chromium cast iron induction furnace is 1480℃, which is enough and does not need to be too high.

8. The pouring temperature of High chromium sand cast iron is not expected to be too high, so as to avoid excessive shrinkage and sticky sand. The pouring temperature is 1350-1400℃ for thick and large parts (1380-1420℃ for general parts). High pouring temperature aggravates the shrinkage cavity under the riser, and will cause dense micro-shrinkage and coarse grain structure.

9. The shrinkage rate of high chromium cast iron model is 2%.

10. The riser size of high chromium cast iron is designed according to carbon steel, and the gating system is designed according to gray cast iron. The pouring riser is cut by the gas cutting method, which is prone to hot cracks. Therefore, the easy-cut riser or the side riser is used in the design, and the knocking method is used to remove it.

11. The reason for the short service life of high-chromium cast iron is not that the metallographic phase is unqualified, but that there are casting defects such as shrinkage cavities, pores, and inclusions in the casting, so the casting process must be paid enough attention.

12. High chromium cast iron is easy to crack. In the design of the casting process, care should be taken not to block the shrinkage of the casting to avoid cracking.

13. High chromium cast iron castings should be fully cooled in the mold, and then unpacked. Premature unpacking and high unpacking temperature are the main reasons for cracking of castings.

14. When high-chromium cast iron is cast by metal mold, the pouring temperature should be kept above 150 °C to prevent the casting from cooling too quickly and cracking.

15. High-chromium cast iron adopts high-temperature air quenching and medium-low temperature tempering heat treatment to obtain a high-hardness martensite matrix.

16. The as-cast matrix structure of high-chromium cast iron before heat treatment depends on the as-cast cooling rate. When the cooling rate is high, it is usually an austenite matrix: as the cooling rate decreases, a mixture of martensite, pearlite and austenite gradually begins to precipitate. The cooling rate is further reduced, and a pearlite matrix structure may be obtained.

17. The best quenching temperature of high-chromium cast iron is generally selected according to the chromium content and the wall thickness of the parts. The higher the quenching temperature, the higher the hardenability, but the greater the amount of retained austenite that may be formed after quenching. The quenching temperature of Cr15 high chromium cast iron is 940-970℃, and the quenching temperature of Cr20 high chromium cast iron is 960-1010℃. The holding time is selected according to the wall thickness. Generally 2-4h, wall thickness parts 4-6h.

18. The high-chromium cast iron after air quenching has large internal stress, and tempering heat treatment should be carried out as soon as possible.

19. For some high-chromium cast iron castings with complex shapes and great disparities in wall thickness, the heating temperature (≤50℃/h) should be strictly controlled to avoid cracking of the castings. Sometimes it is safer to use stepped heating (stay at 200°C, 400°C, and 600°C for 2-3 hours), and the temperature rise above 700°C can be appropriately accelerated. But not more than 150℃/h.

20. The holding time should be comprehensively considered according to the factors such as the wall thickness of the casting, the amount of furnace installed, the state and the heating rate, so as to avoid the quenching of some castings or the core of the casting due to insufficient holding time.

21. High chromium cast iron should be deoxidized when it is released from the furnace. Usually, 0.5% ferromanganese is added to the furnace for pre-deoxidation, 0.25% of ferrosilicon is added to the furnace for initial deoxidation, and 0.05% of aluminum is added to the bag for final deoxidation.

22. The temperature of high-chromium cast iron is controlled at 1450°C during the smelting process, and the final rapid temperature rise is controlled at 1480°C for deoxidation.

Post Casting Process

1. Heat treatment: annealing, carbonization, tempering, quenching, normalizing, surface tempering

2. Processing equipment: CNC, WEDM, lathe, milling machine, drilling machine, grinder, etc.;

3. Surface treatment: powder spraying, chrome plating, painting, sandblasting, nickel plating, galvanizing, blackening, polishing, bluing, etc.

Moulds and Inspection Fixtures

1. Mold service life: usually semi-permanent. (except for lost foam)

2. Mold delivery time: 10-25 days, (according to product structure and product size).

3. Tooling and mold maintenance: Zhongwei is responsible for precision parts.

Available Materials List:

Grey iron and ductile iron

Other materials: cast iron, cast steel, cast aluminum, cast copper, alloy steel, etc. can be customized according to customer requirements.

Quality Control

1. Quality control of High chromium sand cast iron: The defective rate is less than 0.1%.

2. Samples and trial run will be 100% inspected during production and before shipment, sample inspection for mass production according to ISDO standards or customer requirements

3. Testing equipment: flaw detection, spectrum analyzer, golden image analyzer, three-coordinate measuring machine, hardness testing equipment, tensile testing machine;

4. Provide after-sales service.

5. The quality can be traced back.

Application

1. Application of high chromium cast iron grinding ball in ball mill

Ball mill is the main equipment in the grinding process of cement, electric power, mining and other industries. Grinding ball is one of the main wearing parts of ball mill. The grinding ball must have both high wear resistance and high toughness. Its wear resistance plays an extremely important role in production. Therefore, it is extremely important to improve its hardness, impact resistance and wear resistance.

2. Application of high chromium cast iron in slurry pump

Slurry pumps are widely used in industrial and mining sectors such as mining, metallurgy, thermal power generation, coal, chemical industry and environmental protection to transport high-concentration slurry. During the process, it not only bears the erosion and wear of the material, but also bears the corrosion effect of the slurry, and the operating conditions are extremely bad. The materials used in the flow parts of slurry pumps at home and abroad are mainly stainless steel, high chromium cast iron and nickel hard cast iron. High-chromium cast iron is an ideal candidate material for the flow-through parts of slurry pumps. By adjusting or selecting the content of carbon and chromium, the best use of flow-through parts under different industrial and mining conditions can be obtained.

3. Application of high chromium cast iron in cement mill

The manganese-aluminum composite high-chromium cast iron cement grinding roller liner is not ideal for hardenability and wear resistance for thick and large parts, and is only suitable for castings with an effective cross-section of 100mm-140mm. The roller liner with thick and large section needs high-chromium cast iron with certain impact resistance, which is used for large-scale cement vertical mills.

4. Application of high chromium cast iron in crusher jaws

With the increase of the size of the crusher and the improvement of the degree of mechanization, the wear resistance of the jaw plate has become more and more prominent. Due to the poor wear resistance of the jaw plate, frequent replacement is caused, which not only increases the cost of ore breaking, but also reduces the productivity and increases the labor intensity of workers. Therefore, the problem of improving the wear resistance of the jaw plate has attracted people's attention.