cemented carbide – mining parts

I’m Starry, and I have over 10 years of experience in the cemented carbide industry. From the “front lines” of sintering work in the workshop to “on-site debugging” of working conditions, I have gained a lot of experience and lessons the hard way, and I’m sharing all my lessons with you all today. Whether you are a purchaser for a mine, a construction worker on the front lines, or a new beginner, after reading this article, you will know the material, process, and difference for the mining tools, and also learn the “pitfalls” that cost me a lot of money back then.

I. First, Understand the Core: What Makes Cemented Carbide for Mining Special?

Many newbies have this question when they are newly entering this line of work: “Why is there such a big difference between the cemented carbide used in the mining industry and that used in the mechanical processing industry?” The answer is very simple: The working conditions for the mining tools are “hellish” in the true sense of the word.

I still remember when I was newly entering the line of work, my master and I went to an open pit mine to investigate the working conditions. We saw a drill bit that was newly put into use for only 3 hours, and the cutting edge was worn and cracked. At that time, my master turned to me and said, “The working conditions for the mining tools are very harsh, and they have to withstand the impact, wear, and fatigue, and they cannot afford to be careless.”

Before finalizing the specification, compare the required evidence and application inputs in the mining and tunneling carbide tools for supplier review.

Combining my practical experience over the years, here are 3 core characteristics of cemented carbide for mining — remember them to avoid pitfalls:

• The main components are WC-Co alloys, mostly two-phase alloys, and the coarse grain alloys make up the vast majority. The coarse grain structure has some positive effects on the impact resistance, because, after all, each time when drilling the mining rock, there will be a force of several hundred kilograms striking the cutting edge, and if the alloy is fine grain, chipping will certainly occur.
• It has extremely strict requirements for the raw materials. The components of WC and Co are relatively coarse, and the standards are very strict for the total amount of carbon and the amount of free carbon in the WC, namely, the total amount of carbon in the WC must be controlled between 6.05% and 6.15%, and the amount of free carbon must be less than or equal to 0.05%. If the standard is exceeded, the brittleness of the alloy will be increased, and the teeth will easily break when using the alloy.
• Core advantages: The core advantages of cemented carbide mining tools are better compared to those of ordinary tools. Cemented carbide has a hardness of more than HRA85, while the strength and toughness are improved by more than 30%. In addition, cemented carbide has strong adaptability in changing rocks, while the wear resistance is doubled, and no chipping occurs.

A side note: I recall a purchasing situation where a person chose low-cost alloy drill bits with high free carbon content. The drill bits thus broke immediately during drilling rocks, not only slowing down the construction process but almost leading to a safety accident. The purity of raw materials is thus the first lifeline of mining tools.

II. Decoding the Production Process: Seemingly Simple, Every Step Is Critical

Generally, many people think that the production process of cemented carbide mining tools is similar, or even identical, but this is not true. In fact, even a slight difference in each link may influence the service life of the tools.

In the years I have been engaged in the optimization of the production process, I think the most important thing is that in the production of mining tools, “precision” and “adaptability” are both needed. At present, a relatively stable and mature production process has been formed in the industry. The main steps can be described with the following 4 steps and the specific key points:

1. Raw material pretreatment: Mix WC and Co powders in proportion, and then add a forming agent. At present, paraffin is commonly used as a forming agent in the industry. Compared with other forming agents, paraffin has better mixing performance, and the green compact will not crack easily (I tried other forming agents, and the qualification rate of green compact dropped 15% directly).
2. Forming: According to the type of tools, adopt compression molding method, and the pressing pressure should be 150-200MPa. If there is uneven pressure, the density of green compact will be uneven, and deformation will occur after sintering.
3. Dewaxing: The common dewaxing technologies are vacuum dewaxing and hydrogen dewaxing. Vacuum dewaxing will not cause oxidation, and it is more suitable for making high-precision tools. Hydrogen dewaxing has higher efficiency, and it is more suitable for large-scale production. In my working place, both technologies are currently employed, and a balance between efficiency and quality is made.
4. Vacuum sintering: This step is most critical, and the temperature needs to be controlled from 1400-1450℃, along with a holding time of 2-3 hours. If the temperature exceeds this range, there would be growth in the grains, leading to a loss in toughness, while a temperature lower than this would result in insufficient sintering and hardness.

One small additional piece of information: Back then, a batch of drill bits, including cemented carbide drill bits and drill steel bits, was completely discarded due to a 50 degrees Celsius deviation in sintering temperature, leading to a loss of nearly 100,000 yuan. Thus, strict adjustment of process parameters needs to be carried out depending on the material and type of tools.

III. Main Types of Mining Tools: Select on Demand to Double Efficiency

The conditions of mining working are complex, and the types of rock and building require different cemented carbide tools. Many of the building parties are of low efficiency and serious tool wear due to improper selection, and this is the most common problem I face in my daily debugging on the site.

Together with the cases I have encountered, I will introduce 3 kinds of mainstream tools in the following part, and the scenarios and advantages of different tools so that you can choose the tool quickly:

(1) Cemented Carbide Tipped Drill Bit: The “Main Force” for Efficient Drilling

This is the most widely used method in the drilling of mines, especially in large and medium-sized open pit metal mines, especially non-ferrous metal open pit mines, which are almost inseparable from this method. I once saw that in the copper mine, the cemented carbide tipped drill bit was used to replace 8 steel tipped drill bits, the speed was doubled, and the replacement number was reduced by 70% in the large copper mine.

Its core advantages are prominent:

• High efficiency: The speed of the drill bit can reach 1-2 times the speed of the steel-tipped drill bit. Moreover, the drilling speed can reach 15-20m/h, which can be adjusted according to the rock hardness.
• Low wear: The service life of the drill bit can reach 4-10 times the life of the steel-tipped drill bit. This can reduce the number of drill bit replacements and improve the continuity of the project.
• Strong adaptability: This drill bit can adapt to the rock formation with different hardness. As long as the drill bit is selected correctly, it can run stably in both soft rock and medium-hard rock formations.

A brief note: When choosing cemented carbide tipped bits, the wear resistance and impact resistance of the carbide bits are crucial. Especially when drilling through hard rock formations, the recommended content of cobalt in carbide bits is 8-12%, which can help effectively prevent the carbide bits from breaking.

(2) Cemented Carbide Drill Steel Bit: The “All-rounder” for Rock Drilling

The drill steel bits, which are called borer bits, are mainly applied in underground mining, building tunnels, etc. In the process of impact and wear, the condition of the drill steel bits is more complicated than the open-pit mining, as I once witnessed in the underground iron mine: the drill steel bits are required not only to resist the impact but also the complicated conditions of the environment, including the humidity and dust, which requires a higher standard in the selection of materials and methods.

According to the structure, the mainstream drill steel bits are divided into 3 types, which are more efficient to select on demand:

• Straight-type drill steel bit: This is the most commonly used one, with extremely strong adaptability to different rock formations. This is a high-efficiency drill steel bit, used for medium-hard rock formations, with reasonable price and the highest cost performance (in the workshop where I work, the annual output of straight-type drill steel bits accounts for 60%).
• Cross-type drill steel bit: The alloy pieces are brazed vertically to each other. This one has better toughness. This drill steel bit is applicable to drilling soft or broken rock, effectively preventing jamming and chipping of the drill bit. However, the disadvantage is that the drilling speed is slightly lower than that of the straight-type one.
• X-type drill steel bit: The drilling speed is the highest, with rounder drilled blastholes. There are two kinds of connections: conical connection and thread connection, used for mechanized drilling and large-scale construction of large mines. The disadvantage is that the price is slightly higher..

(3) DTH Drill Bit (Down-the-Hole Drill Bit): The “Efficiency King” for Large Mines

Mainly, DTH drill bits are used in the drilling of deep holes in large open pit mines, especially in non-ferrous metal mines. The DTH drill bit has good development prospects. Once, I took part in the project of adapting tools in a large bauxite open pit mine. After using the cemented carbide DTH drill bits, the efficiency was increased by 40%, and the service life was prolonged by 50%. This was very well appreciated by the construction party.

Its main advantages are as follows: the drilling depth is large, efficiency is high, and stability is strong. The DTH drill bits have good adaptability to high-intensity and large-scale drilling. With the use of DTH drill bits and DTH drilling rigs, the construction intensity can be reduced, and efficiency can be improved.

IV. Solving Practical Pitfalls: I’ve Stepped Through These for You

Over the years in the industry, I have seen too many cases of fast tool wear and low construction efficiency due to improper operation and wrong selection. Combining my experience, I summarize 3 of the most common pitfalls and give specific solutions to help you avoid detours:

• Pitfall 1: The tools, especially steel bits and cemented carbide bits, are easy to chip and break — Solution: The content of cobalt and the size of WC particles shall be adjusted according to the hardness of the rock; at the same time, the operation shall be standardized to prevent excessive shock.
• Pitfall 2: The tools are easy to wear and consume too fast — Solution: The cutting edge of the tool shall be checked and ground in time; qualified purity cemented carbide tools shall be used, and those made of poor-quality raw materials shall be avoided; the drilling speed shall be adjusted according to the working condition to prevent dry drilling.
• Pitfall 3: The process is unstable, and the qualification rate of the products is low — Solution: The purity of the raw materials and the sintering condition shall be strictly controlled, and no residue shall be allowed in the dewaxing process; at the same time, the equipment shall be calibrated regularly to prevent product defects caused by equipment errors.

V. Future Outlook: New Directions for Cemented Carbide Mining Tools

According to the development rule of mine intelligence and scale, cemented carbide geological mining tools are constantly improving. Based on the development trend of this industry and my own experience, I dare to predict that “customization + lightweight” is the developing trend in the next 3-5 years.

From one perspective, the characteristics of rock formation and construction equipment for different mines are quite different. The commonly used general-purpose tools can no longer meet the requirements for efficient construction. Customized tools, adjusting the material and structure according to actual requirements, are the developing trend. Currently, I am participating in a customized DTH drill bit project. For the special rock formation of a copper mine, after optimizing the formula of the alloy, the service life of the tool is increased by 60%.

From another perspective, with the increasing popularity of intelligent mining equipment, the requirement for lightweight tools is becoming higher and higher. In terms of hardness and toughness, lightweight cemented carbide tools can reduce equipment load, improve construction efficiency, and reduce labor intensity.

Conclusion: Interactive Exchange, Exploring Industry Insights Together

The above is all the experience I have learned from 10 years of use of cemented carbide geological mining tools, and everything is based on experience.

I would like to ask a question, and that is, have you encountered the following difficulties in using cemented carbide geological mining tools? Is the problem of chipping, wear, and selection difficult? You can comment below, and we can discuss how to solve the problem together to avoid mistakes and move forward together.