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The bollard can also be called a hitch column casting, which is divided from the cast material, and has a cast iron bollard and a cast steel bollard .

First, the casting standard: GB9439-88 two, two casting features: (1) wear resistance and shock absorption. Since the graphite in the cast iron bollard is beneficial for lubrication and oil storage, the wear resistance is good. Similarly, the presence of graphite is superior to the cast steel bollard. (2) Good process performance. Because gray cast iron has a high carbon content and is close to the eutectic composition, the melting point is relatively low, the fluidity is good, and the shrinkage rate is small, so it is suitable for casting complex or thin-walled castings. In addition, since graphite is easy to form chip breaking during cutting, the machinability of gray cast iron is superior to that of steel.

Third, the relationship between hardness and tensile strength: there is a certain correspondence between the hardness and tensile strength of gray cast iron, and its empirical relationship is:

1. When O≥196N/mmm2

HB=RH (fly 00+0 4380b) (B1)

2. When 0≥796N/mmm2

HB=RH (44+O 7240b) (B2)

The relative hardness (RH) value in the formula is mainly determined by the raw material, the melting process, the treatment process, and the cooling rate of the casting.

Fourth, the advantages of using resin sand casting machine tool bed castings

1. Resin sand type has good rigidity and high sand strength at the initial stage of casting. It has the conditions to utilize the graphitization expansion of the solidification process of cast iron, effectively eliminating shrinkage and shrinkage defects, and achieving less risers and no risers of gray cast iron and ductile iron castings. Casting.

2. In the real casting production, the polystyrene foam molding is used to apply the furose resin self-hardening sand molding. When the molten metal is poured into the mold, the foam plastic form is rapidly vaporized under the action of the high-temperature molten metal, and burns and disappears. The molten metal replaces the position occupied by the original foam, and is solidified into a solid casting having the same shape as the shape.

3. Relatively speaking, lost foam casting has great advantages for producing single-piece or small-volume automobile covers, large-sized molds such as machine bed, and traditional sand molds. It not only saves expensive wood type costs, but also is easy to operate. It shortens the production cycle, improves production efficiency, and has the advantages of high dimensional accuracy, small machining allowance and good surface quality.

Heat treatment of machine tool castings

Heat treatment process:

As a large casting, bed casting products must be heat treated to improve their performance and improve the intrinsic quality of cast iron castings. Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing methods, heat treatment generally does not change the shape and overall chemical composition of the workpiece, but changes the microstructure inside the workpiece or changes the chemical composition of the surface of the workpiece. , to give or improve the performance of the workpiece. It is characterized by improved internal quality of the workpiece.

In order to make the metal workpiece have the required mechanical properties, physical properties and chemical properties, in addition to the rational selection of materials and various forming processes, heat treatment processes are often essential. Steel is the most widely used material in the machinery industry. The microstructure of steel is complex and can be controlled by heat treatment. Therefore, the heat treatment of steel is the main content of metal heat treatment. In addition, aluminum, copper, magnesium, titanium, and the like can also be modified by heat treatment to obtain different mechanical properties, physical properties, and chemical properties.

The overall heat treatment is a metal heat treatment process that heats the workpiece as a whole and then cools it at an appropriate speed to change its overall mechanical properties. The overall heat treatment of steel has four basic processes: annealing, normalizing, quenching and tempering.

Bed casting annealing

Annealing type of heat treatment: Common annealing processes include: recrystallization annealing, stress relief annealing, spheroidizing annealing, and complete annealing. The purpose of annealing: mainly to reduce the hardness of metal materials, improve plasticity, to facilitate cutting or pressure processing, reduce residual stress, improve the homogenization of structure and composition, or prepare for the subsequent heat treatment.

Full annealing and isothermal annealing

Complete annealing, also known as recrystallization annealing, is generally referred to as annealing. This type of annealing is mainly used for casting, forging and hot-rolled profiles of various carbon steels and alloy steels with sub-eutectoid compositions, and sometimes for welded structures. It is often used as a final heat treatment for some non-heavy workpieces or as a pre-heat treatment for certain workpieces.

Spheroidizing annealing

Spheroidizing annealing is mainly used for hypereutectoid carbon steel and alloy tool steels (such as steel cutting tools, measuring tools, and steels used in molds). Its main purpose is to reduce hardness, improve machinability, and prepare for later quenching.

Stress relief annealing

Stress relief annealing, also known as low temperature annealing (or high temperature tempering), is mainly used to eliminate residual stresses in castings, forgings, welded parts, hot rolled parts, cold drawn parts, and the like. If these stresses are not eliminated, it will cause deformation or cracking of the steel after a certain period of time or during subsequent cutting operations.

2. Quenching

The most common cooling media we use for quenching are brine, water and oil. The salt-quenched workpiece is easy to obtain high hardness and smooth surface. It is not easy to produce hard spots that are hard to quench, but it is easy to deform the workpiece seriously and even crack. The use of oil as a quenching medium is only suitable for the quenching of some alloy steels or small-sized carbon steel workpieces with relatively high stability of supercooled austenite.


The purpose of tempering is as follows:

Reducing brittleness, eliminating or reducing internal stress, there is great internal stress and brittleness after quenching of steel parts. If it is not tempered in time, it will cause deformation or even cracking of steel parts. 2. Obtaining the mechanical properties required for the workpiece, the workpiece has high hardness and high brittleness after quenching. In order to meet the different performance requirements of various workpieces, the hardness can be adjusted by appropriate tempering to reduce the brittleness and obtain the required toughness. Plasticity. 3. Stabilize the workpiece size 4. For some alloy steels that are difficult to soften by annealing, high temperature tempering is often used after quenching (or normalizing) to properly aggregate the carbides in the steel and reduce the hardness to facilitate cutting.

Castings are mainly used as blanks for machine parts, and some precision castings can also be used directly as parts of machines. Castings account for a large proportion in mechanical products. For example, in tractors, the weight of castings accounts for 50-70% of the weight of the whole machine, 40-70% of agricultural machinery, and 70-90% of machine tools and internal combustion engines. Among all kinds of castings, the most suitable castings for machinery use, the most complex shape, and the largest amount, accounting for about 60% of the total output of castings. Followed by metal ingot molds for metallurgy and engineering pipes.

The non-machined surface and appearance quality of castings have an impact on the commercial properties of castings, including:

(1) Surface roughness (increased box, collapsed and sanded);

(2) Surface or lumen cleanliness (sand, sticky "paint layer");

(3) Flatness deviation (non-machined surface undulations);

(4) Surface roughness;

(5) Contour definition (contour definition of structural units such as bosses and umbilicals, which are evaluated by the naked eye). Machine tool castings for the requirements of the lost mold: coating (1): coating requirements: water-based graphite coating, the wave height is between 60-70, in the greenhouse when painting, it is strictly prohibited to move before drying to prevent Deformation (2) Brushing requirements: the coating is evenly mixed, and the coating is strictly white. (3) Coating drying: After the coating is dry, it must have sufficient strength to dry at 50-60 °C for 24 hours.

The factory strictly adheres to the quality policy of “excellent products, service dedication, scientific management, and first-class”, and adheres to the quality principle of “unqualified raw materials are not put into production, and unqualified products are not manufactured”.

1. Provide special needs product design, manufacturing, to meet the individual needs of customers.

2. The company arranges production and shipment in strict accordance with the contract, and guarantees to supply according to the time specified in the contract.

Each sales engineer will provide our customers with comprehensive pre-sales services, and at the same time, according to the customer's working conditions and purpose, help customers choose the right products and provide comprehensive delivery solutions.

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