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Raw Material Help To Better Grasp The Performance
Jun 30, 2017

Raw material quality indicators, often encounter some terminology, accurately understand its meaning, help to better grasp the performance of raw materials. Some of the commonly used terminology is listed.

Forged metal products are also known as forging, the quality of the conditions forging there are many, first of all raw material control is a prerequisite for the quality of forgings. So today Xiaobian for everyone to introduce, the main defects of raw materials and forgings caused by the main for the following several.

Capillary crack:

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Located in the metal surface, the depth of about 0.5 ~ 1.5mm fine cracks. When the metal is rolled, the subcutaneous bubbles in the ingot are ruptured and ruptured. If not removed before forging, may cause forging cracks.

Fold:

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In the metal raw material surface depth of about 1mm in diameter at both ends of the opposite direction of crease. Horizontal observation, folding with the arc tangent to form an angle, crevice with iron oxide inclusions, surrounded by decarburization.

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The groove on the roll is incorrectly shaped, or the burrs generated by the groove wear surface are involved in the rolling, resulting in folding. If you do not remove before forging, may cause forging folding.

Scarring

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A layer of peelable film in the local area of the rolled material has a thickness of about 1.5 mm. Casting, due to molten steel splash and condensation in the ingot surface, rolling into a thin film and adhere to the surface of the material, that is scar. Forging after pickling cleaning, film peeling off the surface defects forging.

Layered fracture:

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Fracture or cross-section with the broken stone, bark is very similar to this defect in the alloy steel (chrome nickel steel, chrome nickel tungsten steel, etc.) more carbon steel also found.

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Mainly the quality of raw materials smelting problems, often appear in the axial part. It is generally believed that there are non-metallic inclusions in the steel, dendritic segregation and porosity, loose and other defects, in the forging process during the rolling direction was elongated, so that steel was sheet. Excessive impurities, forging there is the risk of layered rupture. The more serious the layered fracture, the plasticity of steel, the worse the toughness, especially the lateral mechanical properties is very low, if the steel layer is obvious layer of defects is unqualified.

Bright line:

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In the vertical fracture showing a bright shiny reflection of the thin lines, the majority of the entire fracture, the majority of the axis produced in the part. Bright lines are mainly due to segregation of alloying elements. The slight bright lines have little effect on the mechanical properties, and the severe bright lines will significantly reduce the plasticity and toughness of the material.

Non-metallic inclusions:

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In the longitudinal section of the rolling performance of the rolling or broken non-metallic inclusions. The former such as ocher, the latter such as oxides, brittle silicate. Non-metallic inclusions are mainly formed by melting or casting molten steel during the cooling process due to the chemical reaction between the components or between the metal and the furnace gas and the vessel. In addition, in the metal smelting and casting, due to refractory material into the molten steel, but also the formation of inclusions, this inclusions collectively as slag. Severe inclusions can cause forging cracking or reduced material performance.

Carbide segregation:

The same time as the above-

Often found in high carbon steel alloy (such as: high-speed steel, etc.), which is characterized by local areas have more carbide aggregation. The roughenite eutectic carbides and secondary reticulated carbides in steel are not broken and evenly distributed during blooming and rolling. Carbide segregation reduces steel forging deformation properties, easily lead to forging cracking. Forging heat treatment quenching easily local overheating, over burning and quenching. When the tool is made, the cutting edge is easy to crack.

Aluminum alloy oxide film:

Generally located on the web of die forging and near the parting surface. In the low magnification organization was fine cracks in the high-speed tissue was vortex-like, in the fracture on the characteristics can be divided into two categories: one, was flat flaky, color from the silver gray, light yellow until brown, dark brown ; The second, was a small dense and with a flash point of the point.

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The oxide film formed when the molten liquid surface of the exposed melt interacts with the vapor or other metal oxide in the atmosphere is formed in the inside of the liquid metal material during the casting process. The oxide film in the forging and die forging has no significant effect on the longitudinal mechanical properties but has a greater effect on the mechanical properties in the high direction, which reduces the strength in the high direction, especially the high direction elongation, the impact toughness and the high direction corrosion resistance The

Carbide segregation:

The same time as the above-

Often found in high carbon steel alloy (such as: high-speed steel, etc.), which is characterized by local areas have more carbide aggregation. The roughenite eutectic carbides and secondary reticulated carbides in steel are not broken and evenly distributed during blooming and rolling. Carbide segregation reduces steel forging deformation properties, easily lead to forging cracking. Forging heat treatment quenching easily local overheating, over burning and quenching. When the tool is made, the cutting edge is easy to crack.

Aluminum alloy oxide film:

Generally located on the web of die forging and near the parting surface. In the low magnification organization was fine cracks in the high-speed tissue was vortex-like, in the fracture on the characteristics can be divided into two categories: one, was flat flaky, color from the silver gray, light yellow until brown, dark brown ; The second, was a small dense and with a flash point of the point.

The same time as the above-

The oxide film formed when the molten liquid surface of the exposed melt interacts with the vapor or other metal oxide in the atmosphere is formed in the inside of the liquid metal material during the casting process. The oxide film in the forging and die forging has no significant effect on the longitudinal mechanical properties but has a greater effect on the mechanical properties in the high direction, which reduces the strength in the high direction, especially the high direction elongation, the impact toughness and the high direction corrosion resistance