A cold saw, also known as a metal cutting cold saw, is a term used to describe the cutting process of a metal circular saw machine. During the metal cutting process, the heat generated by the saw blade teeth cutting the workpiece is transferred to the sawdust, keeping the workpiece and the saw blade cool. That’s why it’s called cold sawing.
Types of Cold Saws
There are two types of cold saw blades: high-speed steel (HSS) blades and TCT (tungsten carbide-tipped) alloy blades.
The material of HSS blades mainly includes M2 and M35. The cutting speed of the blade is generally between 10-150 meters/second, depending on the material and specifications of the workpiece being cut.
Coated HSS blades can achieve cutting speeds of up to 250 meters/minute.
The tooth feed rate of the blade is between 0.03-0.15 millimeters/tooth, depending on the power, torque, and quality of the sawing equipment.
The outer diameter specification of the blade is 50-650 millimeters with a blade hardness of HRC 65.
The blade can be sharpened, and it can typically be sharpened 15-20 times, depending on the specifications of the workpiece being cut.
The cutting life of the blade can reach up to 0.3-1 square meter (cutting end face area) for larger HSS blade specifications.
Generally, inlaid HSS is used for blades over 2000 millimeters, with the saw teeth being made of inlaid HSS material, and the base of the blade being made of vanadium or manganese steel.
The material of TCT alloy teeth is tungsten steel with a blade cutting speed of generally between 60-380 meters/second, depending on the material and specifications of the workpiece being cut. The feed rate of the tungsten steel blade teeth is between 0.04-0.08.
The blade specifications are 250-780 millimeters.
There are two types of TCT blades for cutting iron.
One has small teeth, a thin blade, high cutting speed, and long blade life, lasting for approximately 15-50 square meters of cutting. It is a disposable blade.
The other has large teeth, a thick blade, low cutting speed, and is suitable for cutting large workpieces, with the blade diameter reaching over 2000 millimeters.
The life of the blade is generally around 8 square meters and can be sharpened 5-10 times.
(Compared with Manganese Steel Flying Saw)
Cold saw cutting and friction sawing are different, mainly in the way of cutting:
Manganese steel flying saw blade: The manganese steel saw blade rotates at high speed to generate friction with the workpiece. The friction between the saw blade and the workpiece during the cutting process creates high temperatures that cause the contact-welded pipe to break. This is actually a burn-off process, resulting in visible high scorch marks on the surface.
High-speed steel cold cut saw: relies on the slow rotation of the high-speed steel saw blade to mill-cut welded pipes, which can achieve smooth and burr-free cutting results with no noise.
The cutting speed is fast, achieving optimal cutting efficiency and high work efficiency.
The blade deviation is low, and there are no burrs on the cut surface of the steel pipe, thereby improving the accuracy of the workpiece cutting, and maximizing the service life of the blade.
Using the cold milling and cutting method, very little heat is generated during the cutting process, which avoids changes in the internal stress and material structure of the cut section. At the same time, the blade exerts minimal pressure on the steel pipe and does not cause deformation of the pipe wall and mouth.
Workpieces processed with high-speed steel cold cut saw have good end face quality:
- By adopting an optimized cutting method, the accuracy of the cut section is high, and there are no burrs inside or outside.
- The cut surface is flat and smooth without requiring subsequent processing such as chamfering (reducing the processing intensity of subsequent processes), saving both processing steps and raw materials.
- The workpiece will not change its material due to the high temperature generated by friction.
- The operator fatigue is low, thereby improving the cutting efficiency.
- There are no sparks, dust or noise during the cutting process, making it environmentally friendly and energy-saving.
The service life is long, and the blade can be repeatedly sharpened using a saw blade grinding machine. The service life of the sharpened blade is the same as that of a new blade. This improves production efficiency and reduces costs.
Select the sawing parameters based on the material and specifications of the workpiece being cut:
- Determine the tooth pitch, tooth shape, front and back angle parameters of the saw teeth, the thickness of the blade, and the diameter of the blade.
- Determine the sawing speed.
- Determine the tooth feed rate.
The combination of these factors will result in a reasonable sawing efficiency and the maximum service life of the blade.
Existence of problem and its treatment
Vibration problem and its treatment
During the cutting process, there is a tendency for vibration to occur which can lead to poor cutting effect, long equipment downtime, blade breakage during the cutting process or other occurrences such as bearing burn caused by uneven pressure on the spindle. The surface size and burr of the steel cut by sawing are out of tolerance.
(1) Conventional method: In the installation process, leveling is adopted (set the horizontal position of the upper slide support and lower idler wheel based on the reference point), and the V-shaped wheels are aligned in a straight line using a wire drawing method, so that the idler wheel is at a uniform height and on the same line. Based on the force analysis of the upper slide support, counterweights are added to the saw cover area to balance the force and ensure stable operation.
Stacking problem of steel and its treatment
During the cutting process, if the stress is uneven, the steel may stack, especially when cutting small-sized steel, which can cause damage to the saw blade and equipment.
(1) An air pressure-driven torque clamping device is installed in the cutting port to eliminate the stacking phenomenon, protect the saw blade, and reduce the reactive force generated by deformation of the steel under radial force acting on the saw blade.
(2) Support rollers are added to the cutting port, and after increasing the support rollers, they work together with the clamping device to pressurize the steel before cutting. This significantly improves the surface quality of the saw cut and greatly reduces the damage rate of the saw blade.
The problem of large water spray area and its treatment
When entering the cold saw, round steel is around 320℃, and water is sprayed to cool the saw blade during the cutting and withdrawal processes. In actual production, the water spray area is too large, which causes a decrease in the surface quality of the steel and water waste.
(1) The original sprinkler pipe is replaced with a spray pipe. More nozzles are added, and a fog spray method is used for key spraying at the cutting point. Since the nozzle end has a circular arc concave surface, it can atomize the water mist, make the spray uniform, and is easy to replace due to the use of screw connections, which is conducive to maintenance work.
(2) Use the surrounding cooling method to cool the saw cover, and spray-cool the cutting port and cutting teeth in a targeted manner on key parts.
(3) When feeding during sawing, a spray valve is used, and the injection pressure is increased. The spray valve is closed during withdrawal.
Friction problem between the saw cover and the saw blade and its treatment
The friction between the saw cover and the saw blade causes the overall vibration of the upper slide support, which results in loosening of the motor grounding bolt, and if this goes on for a long time, it will directly cause bearing burn or motor burn.
(1) The connection method of the original saw cover spindle was unreasonable, and the stress point of the saw cover pin shaft was on one side plate of the upper slide support, which easily deformed the side plate and caused the saw cover to tilt. By lengthening the pin shaft and increasing the stress point, using the side plate as a fulcrum, and making the internal panel of the upper slide support the real stress point, the structure of the saw cover became more reasonable, avoiding similar accidents.
(2) When replacing the saw blade, the original method of using a crane to lift the saw cover can easily deform the cover. Now hydraulic cylinders are used to lift the saw cover, and cushion pads are added where the cover contacts with the steel after the saw cover is flipped, which effectively solves the problem.