Five technical requirements in flange forging process (part three)
2. Technical requirements for shape, size and surface condition of flange forgings
Based on reliable raw material quality, one of the tasks of flange forging processing is to obtain the required shape, size and surface condition to meet the requirements of parts design, processing and use conditions. The shape and size of the forgings should conform to these of the part and be as similar or close as possible. The main basis of the forging design is the part drawing. At the same time, the characteristics of the forging process, additional machining allowance and process materials, structural elements of the forgings, surface shape tolerances and dimensional tolerances, etc. should be considered.
Forging surface condition is an important indicator for assessing the quality of forgings. The condition of the non-machined surface of the forging will also directly affect the performance of the part. The starting point of the technical requirements for the surface condition of forgings is to make the surface integrity meet certain specifications.
The basic of ensuring that the parts meet the conditions of use are the structural and mechanical properties of the forgings, which need to correctly formulate and strictly control the forging process.
The structure of forgings includes microstructure and macrostructure. Macrostructure is used to check the flow line distribution of the forging and to judge various metallurgical defects in the forging. Microstructure includes grain size, and purity of the forged part in the final heat treatment state.
The mechanical properties of forgings vary according to the different uses of the forgings and the requirements for their mechanical properties. The room temperature mechanical properties of forgings, such as strength index, plasticity index, impact toughness, hardness, fatigue strength, fracture toughness, etc., will vary depending on the material and forging use. For parts working at high temperatures, there should also be requirements for high temperature instantaneous tensile properties, enduring properties, creep resistance, thermal fatigue properties and thermal stability. The mechanical properties of the forgings should also be consistent with these of the raw materials. For large forgings made from large-size raw materials, the mechanical properties can be appropriately reduced as required. The mechanical performance indicators of various forgings are specified in the relevant technical standards. The test items to be added for the trial production of forgings shall be indicated in the special technical conditions.
Other technical requirements for forgings
Other technical requirements for forgings include forging heat treatment, special project inspection and test methods. According to different materials, the heat treatment of forgings can be divided into preliminary heat treatment and final heat treatment. Steel forgings are supplied in a pre-treated state, and the final heat treatment is carried out during the part processing. High-temperature alloys, titanium alloys and aluminum alloy forgings are mostly supplied in the final heat treatment state.
The processing system for preliminary heat treatment and final heat treatment is noted in the forging drawings or special technical documents. Special project inspection refers to ultrasonic flaw detection and other non-destructive tests of forgings. Due to the complex shape of the forging, ultrasonic flaw detection is only used for important forgings. In addition to the design, the flaw detection part should be considered in the area where the force of the part is large. The characteristics of the process and the weak points of the parts should also be considered. The specific part can be determined by the design, metallurgy and process department, and marked in the product or forging pattern. Other non-destructive tests refer to magnetic particle inspection and fluorescence crack detection. The test methods for checking the technical requirements of forgings must be clearly defined and stated in the technical standards for forgings.
Based on reliable raw material quality, one of the tasks of flange forging processing is to obtain the required shape, size and surface condition to meet the requirements of parts design, processing and use conditions. The shape and size of the forgings should conform to these of the part and be as similar or close as possible. The main basis of the forging design is the part drawing. At the same time, the characteristics of the forging process, additional machining allowance and process materials, structural elements of the forgings, surface shape tolerances and dimensional tolerances, etc. should be considered.
Forging surface condition is an important indicator for assessing the quality of forgings. The condition of the non-machined surface of the forging will also directly affect the performance of the part. The starting point of the technical requirements for the surface condition of forgings is to make the surface integrity meet certain specifications.
The basic of ensuring that the parts meet the conditions of use are the structural and mechanical properties of the forgings, which need to correctly formulate and strictly control the forging process.
The structure of forgings includes microstructure and macrostructure. Macrostructure is used to check the flow line distribution of the forging and to judge various metallurgical defects in the forging. Microstructure includes grain size, and purity of the forged part in the final heat treatment state.
The mechanical properties of forgings vary according to the different uses of the forgings and the requirements for their mechanical properties. The room temperature mechanical properties of forgings, such as strength index, plasticity index, impact toughness, hardness, fatigue strength, fracture toughness, etc., will vary depending on the material and forging use. For parts working at high temperatures, there should also be requirements for high temperature instantaneous tensile properties, enduring properties, creep resistance, thermal fatigue properties and thermal stability. The mechanical properties of the forgings should also be consistent with these of the raw materials. For large forgings made from large-size raw materials, the mechanical properties can be appropriately reduced as required. The mechanical performance indicators of various forgings are specified in the relevant technical standards. The test items to be added for the trial production of forgings shall be indicated in the special technical conditions.
Other technical requirements for forgings
Other technical requirements for forgings include forging heat treatment, special project inspection and test methods. According to different materials, the heat treatment of forgings can be divided into preliminary heat treatment and final heat treatment. Steel forgings are supplied in a pre-treated state, and the final heat treatment is carried out during the part processing. High-temperature alloys, titanium alloys and aluminum alloy forgings are mostly supplied in the final heat treatment state.
The processing system for preliminary heat treatment and final heat treatment is noted in the forging drawings or special technical documents. Special project inspection refers to ultrasonic flaw detection and other non-destructive tests of forgings. Due to the complex shape of the forging, ultrasonic flaw detection is only used for important forgings. In addition to the design, the flaw detection part should be considered in the area where the force of the part is large. The characteristics of the process and the weak points of the parts should also be considered. The specific part can be determined by the design, metallurgy and process department, and marked in the product or forging pattern. Other non-destructive tests refer to magnetic particle inspection and fluorescence crack detection. The test methods for checking the technical requirements of forgings must be clearly defined and stated in the technical standards for forgings.
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