The Technological Properties Of Metal Materials
The technological properties of metal materials include: casting properties, forgeability, weldability, machinability, and heat treatment process properties
- Casting performance: The ability of metal materials to obtain excellent castings by metal casting is called casting performance, which is measured by fluidity, shrinkage and segregation. The material to be cast is mostly solid, but heated to liquid metal, such as copper, iron, tin, etc. The material of the casting mold can be sand, metal or even ceramic. In the first two years in the east of Nanguan vegetable market, two people melted a large number of aluminum cans and poured them into molds to cast large and small aluminum pots, aluminum pots, etc.
- Forgeability: Forging was a common metal processing technology before the Industrial Revolution. Horseshoes, cold weapons, and armor were all forged by blacksmiths in various countries. Gold and silver jewelry processing and metal packaging materials were the sum of metal forging and stamping. The adaptability of metal materials to be formed by forging is called forgeability. Forgeability mainly depends on the plasticity and deformation resistance of the metal material. The better the plasticity, the smaller the deformation resistance, and the better the forging performance of the metal. High carbon steel is not easy to forge, high speed steel is more difficult.
- Weldability: The adaptability of metal materials to welding processing becomes weldability. That is, under certain welding process conditions, it is difficult to obtain high-quality welded joints. The carbon content of steel is the main factor for the welding performance. The higher the carbon content and alloying element content, the worse the welding performance.
- Machining performance: CNC Machining performance is generally expressed by surface quality after cutting (measured by surface roughness) and tool life. The machinability is good when the metal material has appropriate hardness and sufficient brittleness. Changing the chemical composition of steel (such as adding a small amount of lead, phosphorus and other elements) and performing appropriate heat treatment (such as normalizing for low carbon steel and spheroidizing annealing for high carbon steel) can improve the machining performance of steel.
- Heat treatment process performance: The heat treatment process performance of steel mainly considers its hardenability, that is, the ability of the steel to accept quenching. , The hardenability of alloy steel containing manganese, chromium, nickel and other elements is better, and the hardenability of carbon steel is poor. The heat treatment requirements of aluminum alloys are strict, and there are only several kinds of copper alloys that can be strengthened by fusion heat treatment.
The test methods for the process performance of metal materials are as follows：
1. Upset Forging Inspect
Metal materials that need to undergo upsetting operations such as riveting and upsetting must be subjected to a cold upsetting inspect or a hot upsetting inspect at room temperature to determine the upsetting performance. During the inspect, the sample is forged to a specified length, such as 1/3 or 1/2 of the original length, and then the sample is checked for cracks and other defects.
2.The Cold Bending Inspect
A method for inspecting the cold bending properties of metal materials, that is, the material sample is bent around a bending center with a certain diameter to a certain angle or without the bending center to contact on both sides (ie, bending 180°, the bending center diameter d is 0). , Check the plastic deformation near the bend to see if there are cracks and other defects to determine whether the material is qualified. The diameter d of the bending center can be equal to half, equal, 2 times, 3 times, etc. of the thickness of the sample. The bending angle can be 90°, 120°, 180°.
3.The Cupping Inspect
A method for inspecting the metal stamping properties of metal materials. The process is to use the specified steel ball or spherical punch to press the sample in the die until the first crack occurs in the sample. The indentation depth is the cupping depth, and those whose depth is less than the specified value are qualified.
4.Profile Flattening Bending Inspect
Inspect the performance of metal profiles to withstand flattening bending deformation at room temperature or hot state, and show its defects. The process is: hammer the corner of the profile into a flat surface with a hand hammer or a forging hammer, and then bend the surface of the corner of the sample as the inner surface of the bending. Bending angle and thermal state inspect temperature are specified in relevant standards.
Inspect the metal strips, strips, plates and rivets to withstand the specified degree of forging deformation performance at room temperature or hot state, and show their defects. The forging operation can be carried out on a press, a mechanical hammer or a forging hammer; a hand hammer or a sledgehammer can also be used. For strip and plate samples, the width should be increased to the value specified in the relevant standard, and the length should be equal to 2 times the value. For strips and rivets, the sample shall be forged flat until the head diameter is 1.5 to 1.6 times the leg diameter and the height is 0.4 to 0.5 times the leg diameter.
This inspect is used to examine the performance of the wire or wire to withstand winding deformation to show its surface defects or the bonding firmness of the coating. During the inspect, the sample is wound on a mandrel with a diameter D in a tight helical circle along the thread direction. The size of D is specified in the relevant technical conditions. The number of winding turns is 5~10 turns.
This inspect is used to examine the performance of metal wires with a diameter (or feature size) less than or equal to 10mm to withstand plastic deformation when twisted, and to show metal inhomogeneity, surface defects and some internal defects. The method is to take the sample itself as the axis, and twist it uniformly in one direction or alternating direction until the sample breaks or reaches the specified number of twists.
8.Repeated Bending Inspect
This inspect is a method of examining the repeated bending resistance of metals (and coatings) and showing their defects. It is suitable for wires and strips with a cross-sectional area less than or equal to 120mm2 and strips and plates with a thickness less than or equal to 5mm. The method is to clamp the sample vertically in the instrument clamp, and make 90° repeated bending along the left and right directions on a plane that is perpendicular to the mutual contact line with the instrument clamp mouth, and the speed does not exceed 60 times/min. The number of bending is specified by relevant standards.
9.Knot Tension Inspect
This inspect is used to examine smaller diameter wires and single wires after wire rope splits, instead of repeated bending inspects. During the inspect, tie the sample to a dead knot and place it on the tensile inspecting machine to apply the load continuously and evenly until it breaks. The result is the quotient obtained by dividing the maximum load (in Newtons) displayed by the load indicator on the inspecting machine by the original cross-sectional area of the sample. The unit is MPa or N/mm2.
10. Flattening Inspect
This inspect is used to check the deformation properties of metal pipes when they are flattened to specified dimensions and to show their defects. During the inspect, place the sample between two parallel plates, and use a press or other methods to evenly press it to the flattening distance specified in the relevant technical conditions. express. When inspecting the welded pipe, the position of the weld should be in accordance with the relevant technical standards. If there is no stipulation, the weld should be located at an angle of 90° to the direction of force. The inspects are carried out at room temperature, but should not be lower than -10 ℃ in winter. After the inspect, check the bending deformation of the sample. If there is no crack, crack or weld crack, the inspect is considered to be qualified.
This inspect is used to examine the deformation performance of the metal pipe end flare process. Press the top core with a certain taper (such as 1:1015, etc.) into one end of the pipe sample to make it expand evenly to the flaring rate (%) specified in the relevant technical conditions, and then check whether there are cracks and other defects at the flaring. Determine whether it is qualified or not.
This inspect is used to examine the deformation properties of the metal pipe hemming process. During the inspect, the pipe wall is rolled outward to a specified angle (usually 90°) to reveal its defects. After the inspect, check whether there are cracks and other defects at the deformation to determine whether it is qualified.
13.Metal Pipe Hydraulic Inspect
Hydraulic inspect is used to inspect the quality and hydraulic strength of metal pipes, and to show whether there are any defects such as water leakage (or other fluids), wetting or permanent deformation (expansion) of steel pipes and cast iron pipes. Most of them use water as the pressure medium. , so it is also called hydraulic inspect. Although this inspect is not a inspect for further processing, it is customary to call it a process inspect in the current standard.