Encyclopedia of Tungsten Carbide Rods

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Encyclopedia of Tungsten carbide rods

Tungsten carbide is well-known for its properties, and nowadays, can be made into various tungsten carbide products, including tungsten carbide buttons, tungsten carbide dies, tungsten carbide wear parts, and so on. And tungsten carbide rods are one of the tungsten carbide products. In case you may have many questions about tungsten carbide rods, this article is to introduce tungsten carbide rods in as detail as possible as the following aspects:

1. What are tungsten carbide rods?

2. Elements of tungsten carbide rods;

3. How to make tungsten carbide rods?

4. How to cut tungsten carbide rods?

5. Advantages of tungsten carbide rods;

6. Application of tungsten carbide rods;

WHAT ARE TUNGSTEN CARBIDE RODS?

Tungsten carbide rods, also known as tungsten carbide round bars, are made of cemented carbide, which is a type of composite material manufactured by powder metallurgy. As a product of tungsten carbide, carbide rods also have better properties such as high hardness, wear resistance, and corrosion resistance.

ELEMENTS OF TUNGSTEN CARBIDE RODS

Cemented carbide consists of a refractory metal compound and bonding metal so tungsten carbide rods are inorganic material composed of tungsten and carbide atoms in equal proportions. The raw material tungsten carbide powder is a light gray powder and has a carbon content that is three times higher than that of steel. As the tungsten carbide has high hardness, only after diamond, the only abrasive way to polish tungsten carbide is the cubic boron nitride

HOW TO MAKE TUNGSTEN CARBIDE RODS?

1. Prepare raw materials;

High-quality tungsten carbide powder and cobalt powder will be well-prepared for manufacturing tungsten carbide rods.

2. Ball milling;

The mixture of tungsten carbide powder and cobalt powder will be put into the ball milling machine according to a certain grade and grain size. The ball milling machine has the ability to manufacture powder of any grain size, like fine and ultra-fine powder.

3. Spray drying;

After ball milling, the tungsten carbide mixture becomes a tungsten carbide slurry. And for finishing compacting and sintering, we should dry up the mixture. The dry spray tower can achieve this. 

4. Compacting;

There are three methods that can be used to compact tungsten carbide rods. They are die pressing, extrusion pressing, and dry-bag isostatic pressing.

Die pressing is pressing the tungsten carbide with a die mold. This process is used for manufacturing most tungsten carbide production. There are two kinds of ways to press tungsten carbide with a die mold. One for the small size of production, they are pressed automatically by a machine. The larger ones are compacted by a hydraulic press machine, which will produce more pressure.

Extrusion pressing can be used to press tungsten carbide bars. In this process, there are two kinds of forming agents used widely. One is cellulose, and the other one is paraffin. Using cellulose as forming agent can produce high-quality tungsten carbide bars. Tungsten carbide powder is pressed into a vacuum environment and then out continuously. But it takes a long time to dry the tungsten carbide bars before sintering. Using paraffin wax also has its characteristics. When the tungsten carbide bars are discharging, they are a hard body. So it doesn’t take a long time to dry. But the tungsten carbide bars produced with paraffin as its forming agent have a lower qualified rate.

Dry-bag isostatic pressing can also be used to press tungsten carbide bars, but only for that under 16mm diameter. Otherwise, it will be easy to break. During the dry-bag isostatic pressing, the forming pressure is high, and the pressing process is fast. Tungsten carbide bars after dry-bag isostatic pressing have to be ground before sintering. And then it can be sintered directly. In this process, the forming agent is always paraffin.

5. Sintering;

During sintering, cobalt powder gets melted because of its low melting point and binds the tungsten carbide particle tightly. During the sintering, the carbide rods will shrink apparently, so it is very important to calculate shrinkage before sintering in order to achieve the desired tolerance.

6. Machining;

In order to reach accuracy tolerances, the majority of the rod blanks will need to be centerless ground and provide other services, including, length cutting, chamfering, slotting, and cylindrical grinding.

7. Inspection;

In order to assure both quality and performance, the essential qualities of the raw material, RTP, and raw sintered components are examined and analyzed. We will carry out a string of comprehensive checks, including testing the straightness, sizes, and physical performance of the object, etc. 

You can also get more information on How Long Will It Take To Produce Carbide Rods.

HOW TO CUT TUNGSTEN CARBIDE RODS?

As tungsten carbide rods can be used for multiple purposes, the sizes needed are different. Sometimes, the users need to cut the long tungsten carbide rods into shorter ones. Here are two ways to cut tungsten carbide rods.

1. Cutting with a tabletop grinder;

Different tabletop grinders behave differently. When cutting tungsten carbide rods with a table grinder, the worker should mark the area where you will be cutting the carbide rods and press the carbide rods against the diamond grinding wheel firmly with both hands. The tungsten carbide rods should be removed from the cutter as far as possible and cooled in clean water. 

2. Cutting with a cutting tool;

Workers should place tungsten carbide rods into a vice tightly enough but don’t apply excessive pressure. The diamond cutting wheel should be tightened to the grinder so that it won’t move. Workers should make the area where will be cut, and then start the grinder and cut the carbide rods directly.

ADVANTAGES OF TUNGSTEN CARBIDE RODS

1. Compared with high-speed steel cutting tools, tungsten carbide rods are more cost-effective and efficient. They have a longer lifespan so that they can serve for a long time;

2. Tungsten carbide rods are able to tolerate extreme temperatures and can spin at very high speeds;

3. When it comes to finishing, tools made from tungsten carbide rods can deliver superior performance than another type;

4. Tungsten carbide rods have high resistance to crack;

5. Carbide rods are the financial choice to avoid making frequent tool purchase.

APPLICATION OF TUNGSTEN CARBIDE RODS

With many good properties of tungsten carbide, including high red hardness, weldability, and great hardness, carbide rods can be widely used in various industries. Tungsten carbide round bars can be manufactured into drills, end mills, and reamers. They can be tools for papermaking, packing, printing, and cutting various materials, like solid wood, density boards, non-ferrous metal, and gray cast iron. Tungsten carbide rods are popularly used to process other materials, like tungsten carbide milling cutters, aviation tools, milling cutters, cemented carbide rotary files, cemented carbide tools, and electronic tools.

As a professional manufacturer of tungsten carbide products, with more than 10 years of history, ZZBETTER is committed to providing you high quality and durable tungsten carbide rods. And we can assure you that every tungsten carbide rod sent to you, is inspected and well-packed. If you are interested in tungsten carbide round bars and want more information and details, you can CONTACT US by phone or mail at the left, or SEND US MAIL at the bottom of the page. 

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While the metallurgic term “carbide grades” refers specifically to tungsten carbide (WC) sintered with cobalt, the same term has a broader meaning in machining: sintered tungsten carbide combined with coatings and other treatments. For example, two turning inserts made of the same carbide material but with a different coating or post-treatment are considered different grades. Carbide and coating combinations lack classification standardization, however, so different cutting tool suppliers use different names and classification methods for their grade charts. This can make grade comparison difficult for the end-user, an especially trying problem given that carbide grade suitability for a given application dramatically affects possible cutting conditions and tool life.

To navigate this maze, users must first understand what constitutes a carbide grade and how each element influences different aspects of machining.

What is the Substrate?

The substrate is the bare material of the cutting insert or solid tool underneath the coatings and post-treatments. It is typically made up of between 80- and 95-percent WC. To give the substrate the desired properties, material manufacturers add various alloying elements. The main alloying element is cobalt (Co) — higher levels of cobalt lead to greater toughness, while lower levels of cobalt lead to greater hardness. Very hard substrates can reach a hardness of 1800 HV and provide excellent wear resistance, but are very brittle and are only suitable for very stable conditions. Very tough substrates have a hardness of around 1300 HV. These substrates can machine only at lower cutting speeds and wear out faster, but have better resistance to interrupted cuts and unfavorable conditions.

The right balance between hardness and toughness is the most crucial factor when selecting a grade for a particular application. Picking a grade that is too hard can lead to micro breakages along the cutting edge or even catastrophic failure. At the same time, a grade that is too tough will wear out fast or require decreasing the cutting speed, thus reducing productivity. Table 1 provides some basic guidelines for selecting the correct hardness:

Table 1 - Source: MachiningDoctor.com Material Turning Milling   Continuous Light Interrupted Heavy Interrupted   Steel Hard Medium Tough Tough Stainless Steel Hard Medium Tough Tough Aluminum Hard Medium-Hard Medium Medium Inconel Very Hard Hard Medium Tough Titanium Very Hard Hard Medium Medium

What Are Carbide Coatings?

Most modern carbide inserts and solid carbide tools are coated with a thin film (between 3 and 20 microns, or 0.0001 to 0.0007 inch). The coating is typically composed of titanium nitride, aluminum oxide and titanium carbon nitride layers. This coating increases the hardness and creates a heat barrier between the cut and the substrate.

Cutting tool coatings are added through one of two major technologies:

Additional reading:
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Want more information on high quality carbide pdc cutter insert? Feel free to contact us.

1. CVD (Chemical Vapor Deposition) —CVD coating layers can be as thick as 25 microns. This thickness ensures an effective heat barrier and enables higher cutting speeds compared with PVD coatings. On the other hand, that same thickness makes coating very sharp cutting edges impossible, and the coating is more prone to cracks and breakages.
2. PVD (Physical Vapor Deposition) — PVD coatings range in thickness from 1 to 8 microns. PVD-coated inserts need to operate at lower cutting speeds when compared with CVD; however, they are tougher, can be applied on sharp cutting edges, and have smoother surfaces that generate less friction.

Table 2 provides a basic guide to selecting the most suitable coating for different applications.

Table 2 - Source: MachiningDoctor.com Material Turning Parting and Grooving Milling   High Cutting Speed Low Cutting Speed     Steel CVD PVD PVD PVD / Thin CVD Stainless Steel Thin CVD PVD PVD PVD / Thin CVD Aluminum Uncoated Uncoated Uncoated Uncoated Inconel Thin PVD Thin PVD Thin PVD PVD Titanium Thin PVD / Uncoated Thin PVD / Uncoated Thin PVD / Uncoated PVD / Uncoated

What Are Post-Treatments?

Despite only gaining traction about a decade ago, adding a post-treatment after coating has become an industry standard. These treatments are usually sandblasting or other polishing techniques that smoothen the top coating layer, reducing friction and, as a result, generated heat. Price differences are typically minor, and in most cases, it is recommended to favor grades with post-treatment.

Grade Selection Charts

To choose the correct carbide grade for a particular application, look at the supplier's catalog or website for guidance. Although there is no formal international standard, most suppliers use charts that describe grades’ recommended working envelopes based on their "application range" as expressed in a three-character letter-number combination, such as P05-P20.

The first letter represents the material group according to the ISO standard. A letter and a corresponding color are assigned to each material group.

Letter Material Color P Steel Blue M Stainless Steel Yellow K Cast Iron Red N Non-Ferrous Green S Super-Alloys Orange H Hardened Steel Grey

The following two numbers represent the grade's relative hardness level on a scale from 05 to 45 in increments of 5. A 05 application requires a very hard grade suitable for favorable and stable conditions. A 45 application requires a very tough grade suitable for unfavorable and unstable conditions.

Again, there is no standard for these values, so they should be interpreted as a relative value within the specific grade table in which they appear. For example, a grade marked as P10-P20 in two catalogs of different suppliers could have a different hardness.

Grade selection tables are usually shown separately for four different main applications:

1. Turning
2. Milling
3. Grooving/Parting
4. Drilling

A grade marked as P10-P20 in the turning grades table could have different hardness than a grade marked as P10-P20 in the milling grades table, even in the same catalog. This difference comes down to the fact that favorable conditions vary across different applications. Turning applications are best tackled with very hard grades, but in milling, favorable conditions require some toughness because of its interrupted nature.

Table 3, “Grades for Turning” - Source: MachiningDoctor.com

Table 3 depicts a hypothetical chart of grades and their uses in different difficulties of turning applications, as might appear in a cutting tools supplier catalog. In this example, grade A would be recommended for a wide range of turning conditions, but not for heavy interrupted cuts, while grade D would be recommended for heavy interrupted turning and other highly unfavorable conditions. Tools such as the Grades Finder from MachiningDoctor.com can search for grades according to this designation system.

Carbide Grade Designations

Just as there is no official standard for grade application ranges, there is no formal standard for grade designations. That said, most major carbide insert suppliers follow common guidelines in their grade designations. The "classic" designation follows a six-character format BBSSNN, where:

• BB — Brand Code: Each major supplier has its own letters associated with it.
• SS — Grade Series Number: Grade series numbers are usually represented by two random digits. A series is usually a group of grades designed for a particular raw material and sharing a common coating type. Some examples of grade series could be:
  • BB85 — CVD grades for turning steel.
  • BB64 — PVD grades for nickel-based alloys.
  • BB23 — CVD grades for milling cast iron.
• NN — Hardness Level: The last two digits, in most cases, reflect the hardness level of the different grades in a series. The number usually ranges from 05 to 45 according to the same system explained above about the grade charts. For example:
  • BB8505 — A very hard grade for turning steel in stable conditions.
  • BB8540 — A very tough grade for turning steel in heavy interrupted cuts.

The above explanation is correct in many cases. But since this is not an ISO/ANSI standard, some suppliers make their own adjustments to the system, and it is wise to be on the lookout for these changes.

Turning Grades

Grades play a vital role in turning applications, more than in any other application. Because of that, when checking any supplier's catalog, the turning section will feature the largest selection of grades.

Why are grades so important in turning?

This extensive range of turning grades stems from the extensive range of turning applications. Everything from continuous machining, where the cutting edge is constantly engaged with the workpiece and suffers no impact but generates lots of heat, to interrupted cuts, which have heavy impacts, falls into this category.

The wide range of turning grades also relates to the vast array of diameters in manufacturing, from 1/8 inch (3 mm) for Swiss-type machines to 100 inches for heavy industrial purposes. Because the cutting speed also depends on the diameter, there is a need for different grades that are optimized for either low or high cutting speeds.

Major suppliers usually provide separate series of grades for each material group. In each series, the grades range from tough for interrupted cuts to hard for continuous machining.

Milling Grades

In milling, the range of grades on offer is smaller. Due to the application’s fundamentally interrupted nature, milling tools require tough grades with high impact resistance. For the same reason, the coating layer must be thin — otherwise, it will not withstand the impacts.

Most suppliers will use a tough substrate and a variety of coatings for milling different material groups.

Parting and Grooving Grades

In parting or grooving applications, grade selection is limited due to cutting speed factors. That is, the diameter gets smaller as the cut approaches the center. The cutting speed thus decreases gradually. In parting-off to the center, the speed ultimately reaches zero at the end of the cut, and the operation becomes shearing instead of cutting.

Therefore, a grade for parting-off must be compatible with a wide range of cutting speeds, and the substrate should be tough enough to handle the shearing at the end of the operation.

Shallow grooving is an exception to other types. As it shares similarities with turning, suppliers with a large selection of grooving inserts will usually offer a wider variety of grades for specific material groups and conditions.

Drilling Grades

In drilling, the center of the drill always has a cutting speed of zero, while the periphery has a cutting speed that depends on the drill diameter and spindle speed. Grades optimized for high cutting speeds will fail, and therefore should not be used. Most suppliers will offer just a handful of grades.

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