Analysis of common defects in copper alloy tube and rod profiles
1. Overheating and overburning:
Definition:
During the heating or processing process of metal, due to high temperature and long time, the phenomenon of enlarging the structure and grains of the island is called overheating. When severe overheating occurs, the low melting point components between the grains will melt or the grain boundaries will weaken, which is called overburning.
cause:
a. The heating temperature is high, the heating time is long, or the area is exposed to a high temperature source for a long time;
b. The temperature at the end of hot extrusion is too high or the product stays in the high temperature area for a long time;
c. There are low melting point components or there are many low melting point impurities in the alloy.
2. Cracks or cracking:
Definition:
Continuous or intermittent irregular cracks appear on the surface of pipe and rod profiles. Minor ones are called cracks, and severe ones are called cracking.
cause:
a. There are cracks, inclusions, shrinkage cavities, porosity, cold insulation or other harmful impurities in the casting ingot or the crystal structure and chemical composition are seriously uneven;
b. There is large stress in the ingot or large stress caused by improper processing technology;
c. The extrusion speed is too fast and the processing rate is too high;
d. The heat treatment process is improper, and the processing or heat treatment is in the brittle temperature zone of the material.
3. Contraction:
Definition:
Tail shrinkage is a special defect at the tail of extruded products. At the end of extrusion, due to metal turbulence, oxide scale on the surface of the ingot, lubricant and other contaminants often flow into it, resulting in delamination between metals.
cause:
a. The metal flow at the extrusion tail is disordered;
b. There are defects on the surface and sub-surface of the ingot, and there are lubricants and other contaminants in the extrusion barrel.
4. Bubbling
Definition:
The surface of the product after extrusion, drawing, and return has strip-like bulges elongated along the processing direction. When dissected, it becomes a cavity. This bulge is called a bubble. The bubbles are mostly long strips with a smooth surface and a metallic luster inside when cut open, with some associated oxides or other inclusions.
cause:
a. There are defects such as pores, shrinkage cavities, and inclusions in the ingot, and delamination is formed along the processing direction after extrusion, stretching, and cold rolling;
b. Excessive lubricant in the extrusion cylinder;
c. The shrinkage of the extruded product is not completely removed, and delamination is formed after further stretching.
5. Dezincification
Definition:
After annealing or pickling of zinc-containing copper alloy tubes, rods and wires, gray or red spots appearing on the surface are called dezincification. The above-mentioned stains may appear slightly, and severe dezincification may cause microstructural changes.
cause:
a. The annealing temperature is too high, and the flame is directly sprayed onto the surface of the product, causing the zinc to melt, volatilize or oxidize;
b. The extrusion temperature is too high;
c. During pickling, the acid concentration is too high and the pickling time is too long, causing surface dezincification;
d. Under the action of environmental media, chemical or electrochemical reactions occur to form dezincification.
6. Pockmarked noodles (commonly known as pitting and trachoma)
Definition:
The rough surface with tiny dot-like depressions and uneven surfaces on the surface of tube-rod wire rods is called pitted surface. The pockmarks are distributed locally, periodically or in patches. Individual ones are called pockmarks, and severe ones are called pockmarks.
cause:
a. High annealing temperature and long annealing time lead to coarse grains, and zinc-containing copper alloys are severely dezincified during annealing;
b. Pickled;
c. The processing rate is too small and the surface is not smooth;
d. The surface of the processing equipment or tools is not smooth, and foreign matter is stuck on it, which is formed after contact with the material.
7. Surface ring marks
Definition:
Periodic annular protrusions appear on the surface or inner wall of tube-rod wire rods and become surface annular marks, commonly known as bamboo knots.
Surface ring marks are produced during the stretching, peeling and straightening processes. Ring marks are generally smooth, and individual raised edges have edges and corners. During the straightening process, a special annular bulge appears along the 450 direction.
cause:
a. The reasons for the stretching ring are uneven annealing temperature, poor process and lubrication, and incomplete pickling;
b. The reason for the ring-shaped peeling is that the design of the peeling mold is unreasonable and the stretching speed is inappropriate; or the cutting edge of the peeling mold is not sharp and the chip removal resistance is large;
c. The cause of the straightening ring is improper adjustment of the roller angle or excessive pressure.
Brands and uses of commonly used copper alloys
▲Ordinary brass, 6 common brands
1. H96, used for condenser tubes, radiators, heat sinks and conductive parts.
2. H80, used for thin-walled pipes, corrugated pipes, etc.
3． H70, used for mechanical and electrical parts, etc.
4. H68, used for complex cold-stamped parts, deep-drawn parts, radiator shells, etc.
5. H65, used for small hardware, small springs, screws and machine parts, etc.
6. H62, used for rivets, pins, conduits, nuts, etc.
▲Lead brass, 3 common grades
1. HPb63-2, used for general strength mechanical parts.
2. HPb61-1, used for high-strength structural parts.
3. HPb59-1, used for hot stamping and cutting parts, such as pins, screws, etc.
▲Manganese brass, 2 common brands
HMn58-2 and HMn57-3-1 are mainly used for parts used in corrosive conditions and weak current industries.
▲Tin brass, 3 common brands
1. HSn90-1, used for elastic bushings of automobiles and tractors and other corrosion-resistant and friction-reducing parts.
2. HSn70-1, high temperature corrosion-resistant condenser tubes and conduits in ships and power plant equipment.
3. HSn62-1, used for parts that come into contact with sea water and gasoline.
▲Iron brass, 2 common brands
1. HFe59-1-1, used for parts working under friction and corrosion, such as washers, bushings, etc.
2. HFe58-1-1, high-strength corrosion-resistant parts used for hot pressing and cutting.
▲Nickel brass
Hni65-5, used for pressure gauge tubes, condenser tubes and papermaking nets, etc.
▲Tin bronze, 5 common grades
1. QSn4-3, corrosion-resistant and wear-resistant parts, diamagnetic components and springs, etc.
2. QSn4-4-2.5, parts subject to friction, such as bushings, bearings, discs, etc.
3． QSn6.5-0.1, spring contact piece, wear-resistant and anti-magnetic parts in precision instruments.
4． QSn6.5-0.4, used for papermaking copper mesh, springs, wear-resistant parts, etc.
5. QSn7-0.2, used for workpieces that are subject to friction, such as bearings, worm gears and springs.
▲Aluminum bronze, 5 common grades
1. QAI5, for corrosion-resistant elastic components.
2. QAI9-2, pipe fittings working in steam below 250℃.
3. QAI9-4, used for bearings, gears, valve seats, ship parts and electrical components.
4. QAI7, used for gears, friction wheels, worm gear transmission mechanisms, etc.
5. QAI10-3-1.5, used for wear-resistant parts working at high temperatures, such as bearings, gears, flywheels, etc.
▲Beryllium bronze, 2 common grades
1. Qbe1.7, used for important springs, sensitive components of precision instruments, etc.
2. Qbe2 is used for important elastic components and bearings under high-speed and high-temperature working conditions.
▲Silicon bronze, 2 common brands
1. QSi1-3 is used for friction parts working below 300℃, such as intake and exhaust valve guide bushes.
2. Qsi3-1, used for springs, worm gears, worm gears and corrosion-resistant parts, etc.
▲Manganese bronze
QMn5 is commonly used in the manufacture of various pipe joints for steam engine parts and worm gears, steam valves and other high-temperature corrosion-resistant parts.
