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简体中文 Cemented carbide rod is the core blank material for manufacturing CNC drills, end mills, reamers, step tools and various non-standard rotary cutting tools. In modern cemented carbide production systems, there are three mainstream forming processes for cemented carbide rod, including compression molding, precision extrusion molding and dry bag isostatic pressing.
These three processes differ greatly in forming principles, product features and production adaptability, targeting three segmented markets: mass standardized production, long bored rod production and high-precision tool production.
Compression Molding
Working Principle
Compression molding is the most mature and widely used traditional process for cemented carbide rod production. In production, well-mixed tungsten-cobalt powder with a proper amount of forming agent is filled into the cavity of high-precision customized rigid molds. With the support of hydraulic press equipment, unidirectional or bidirectional vertical pressure acts on the powder to achieve even compaction. Loose alloy powder is rapidly densified and molded into uniform cemented carbide rod blanks in one complete pressing cycle.
Process Features
Compression molding relies on rigid mold limiting forming and has obvious practical advantages.
Excellent dimensional accuracy
Restricted by precision molds, molded blanks have consistent outer diameter and roundness. The shrinkage deformation during sintering is controllable with small dimensional tolerance, which requires no complex finishing process.
Stable process and controllable cost
This production process features simple procedures, easy operation and universal equipment. It needs few auxiliary processes with low unit cost, which is fully suitable for large-scale industrial production.
High production efficiency
For standard short and small-diameter cemented carbide rod products, continuous rapid pressing can be realized. Its production capacity is higher than extrusion molding and dry bag pressing, making it the preferred process for mass production of standard rods.
Limitations
Limited by mold structure and cavity length, compression molding can only produce short cemented carbide rods and cannot meet the production requirements of ultra-long tool blanks. In transverse pressing, the upper and lower punches cannot fit completely, forming natural edge burrs on blank surfaces. Subsequent grinding and trimming are required, which increases working procedures and labor cost. It also slightly affects surface flatness and causes minor fluctuation of finished product yield.
Application Scenarios
This process is suitable for standardized solid cemented carbide rods with short length, small diameter and large order volume. It is widely used for blank production of standard milling cutters, general drills and ordinary reamers, and serves as the core process for mass production of common tool consumables.
Precision Extrusion Molding
Working Principle
Precision extrusion molding is a continuous forming process developed for slender and bored special-shaped cemented carbide rod products. Tungsten-cobalt powder is fully mixed with professional organic binder and lubricant in accurate proportion to prepare mixtures with stable fluidity and plasticity.
The mixed materials are sent to the extrusion cavity. The hydraulic system provides constant extrusion pressure to push materials through customized molds and core rod structures for continuous molding. This process can produce solid rods, straight internal cooling hole rods and spiral cooling hole rods to realize uninterrupted continuous production.
Process Features
Precision extrusion molding shows unique advantages in product structure and size adaptability.
Unlimited forming length
Different from compression molding restricted by fixed mold size, extrusion molding can continuously produce ultra-long cemented carbide rods, satisfying the production demand of special tools with large length-diameter ratio and extended cutting tools.
Exclusive process for internal cooling hole rods
By installing high-precision fixed core rods inside molds, straight or spiral internal cooling holes can be integrally formed in one step. The process ensures high standard of hole position accuracy, linearity and roundness. It is the core forming method for high-pressure cooling tools and cannot be replaced by compression molding or dry bag pressing.
Uniform blank density
Materials flow steadily and bear uniform pressure during extrusion, which effectively avoids local looseness and uneven density. The overall structural consistency of extruded blanks is better than conventional compression-molded products.
Limitations
A large amount of organic forming agent and binder is added to guarantee material fluidity. The follow-up degreasing, dewaxing and high-temperature sintering require strict parameter control. Unreasonable temperature zones, heating speed or holding time will lead to uneven shrinkage, internal cracks and pore defects, which demands standard production equipment and mature process experience.
Application Scenarios
This process is mainly used for ultra-long cemented carbide rods, straight or spiral internal cooling hole rods and extended precision tool blanks. It is widely applied in high-end tool manufacturing including deep-hole drills, extended end mills and high-pressure cooling finishing cutters.
Dry Bag Isostatic Pressing
Working Principle
Dry bag isostatic pressing is a precision forming technology for high-end cemented carbide rod production. Preprocessed high-purity cemented carbide powder is filled into a semi-fixed flexible dry bag mold and sealed. The whole mold is fixed inside a pressure vessel. Fluid media such as water or oil provides uniform omnidirectional static pressure. Different from unidirectional pressing, this three-dimensional pressurization mode compacts powder evenly and produces high-quality stress-free cemented carbide rod blanks with uniform microstructure.
Process Features
Extremely uniform internal structure
Omnidirectional fluid pressure ensures consistent stress on all blank positions, eliminating local density deviation and internal stress concentration caused by unidirectional compression. Sintered products have uniform grain distribution and no loose pores or residual stress. Tools made by this process are not easy to chip or deform during high-speed and heavy-load cutting, delivering more stable performance than products from the other two processes.
Low mold development cost
This process requires no customized rigid molds and can flexibly produce super-large diameter rods, ultra-long rods and various special-shaped alloy blanks. Pressed green blanks have high strength and can be directly transported, turned and finished with high machining tolerance.
Limitations
This process has obvious disadvantages in production capacity and dimensional accuracy. Compared with high-efficiency compression molding, dry bag pressing has longer single-batch production cycles and lower output. Flexible molds have no rigid positioning limit, so the outer diameter accuracy of blanks is slightly lower than compression-molded products, requiring additional precision turning and grinding correction.
Application Scenarios
It is suitable for high-end solid precision rods, large-diameter cemented carbide rods and special-shaped alloy parts. It serves high-precision fields such as aviation, precision molds and high-end CNC tool manufacturing that require stable internal structure, reliable cutting performance and long service life.
Core Selection Criteria for Forming Processes
1.Selection by Tool Structure
Tool structure is the key basis for process selection. Precision extrusion molding is the only choice for drills and mills with straight or spiral internal cooling holes. Only extrusion technology can form integrated high-precision cooling holes and guarantee hole accuracy, while compression molding and dry bag pressing cannot realize integrated internal hole forming. For solid rods without cooling holes, users can choose compression molding or dry bag pressing according to actual size, accuracy and performance requirements.
2. Selection by Geometric Size
Product size is a key restrictive factor for process matching. Limited by rigid molds, compression molding only adapts to short and small-diameter standardized rods. Extrusion molding has no length limit and is suitable for ultra-long rods with a large length-diameter ratio. Dry bag pressing has the widest size adaptability for large-diameter, ultra-long and non-standard special-shaped rods. The basic selection rule is compression molding for small standard rods, extrusion molding for long bored rods, and dry bag pressing for large-diameter high-end special-shaped rods.
3. Selection by Product Positioning
Compression molding is preferred for general economical tools and mass consumables to balance efficiency and cost. Precision extrusion molding is suitable for high-end finishing tools, heavy-load cutting tools and ultra-long cooling tools. Dry bag pressing is the best choice for tools used in aviation, precision molds and other high-precision fields, as its uniform internal structure ensures stable performance and long service life.
निष्कर्ष
In conclusion, the three forming processes have no absolute advantages or disadvantages, but differ in applicable scenarios. With differentiated forming principles and technical characteristics, they fully cover the production demands of all types of cemented carbide rod products in the industry.
