Tungsten Density 19.3 to Carbide — SR7X/SR8C/SR10C | Ruixin



A Mining Pick Is Wearing Out in Half the Expected Time — Density Is the Clue Most Operators Miss

A tool grinder orders a batch of carbide rod blanks and calculates shipping weight based on listed density. A shearer operator replaces picks every shift instead of every three shifts because the tips are fracturing instead of wearing. Both problems trace back to the same overlooked variable: the density of tungsten metal — and how it changes when that tungsten is alloyed into a cemented carbide grade.

For a system-level diagnosis before changing carbide, continue with the tungsten carbide rod blanks for density sr7x/sr8c/sr10c.

Pure tungsten has a density of 19.3 g/cm³. That makes it one of the heaviest commodity metals on Earth, comparable to gold and significantly heavier than lead at 11.3 g/cm³. But when tungsten is combined with carbon to form tungsten carbide (WC) and then bound with cobalt into a cemented carbide composite, that density drops significantly and predictably. Ruixin’s SR7X grade registers 14.70 g/cm³. SR8C reads 14.65 g/cm³. SR10C sits at 14.45 g/cm³.

The difference between 19.3 and 14.45 is not a quality loss — it is a design trade-off. Understanding exactly what that ~25% density reduction buys you in toughness, and what it costs in wear resistance, is how you stop replacing picks prematurely and start ordering the grade that matches your actual working conditions.

Why the Wrong Grade Fails Faster Than the Wrong Operator

A 14.70 g/cm³ grade like Ruixin SR7X delivers HRA 91.0 hardness and flexural strength ≥2,000 MPa — outstanding wear resistance in steady-state abrasion. But in a longwall shearer drum hitting intermittent rock inclusions, that same 14.70 g/cm³ density signals a microstructure designed for stiffness, not impact absorption.

The failure mode shifts from gradual wear to sudden fracture because the cobalt content (inversely tied to density) is too low to absorb the shock. Replace a grade at 14.70 g/cm³ with one at 14.45 g/cm³ (SR10C, HRA 88.0, ≥2,200 MPa flexural strength) and the fracture rate drops. In Ruixin’s own field data from Australian longwall operations, switching from a high-hardness grade to SR10C reduced tip failure rates by more than 60%.

The failure isn’t random — it is the predictable result of selecting a grade whose density profile signals a hardness-first formulation for an impact-dominated environment.

The Technical Variables — How 19.3 g/cm³ Becomes 14.45 g/cm³ and Why Each Step Matters

The density of tungsten metal at 19.3 g/cm³ represents pure W atoms in a body-centered cubic lattice. In cemented carbide, those tungsten atoms are first reacted with carbon to form tungsten carbide (WC), which has a density of approximately 15.6 g/cm³. The WC particles are then bound together by a cobalt matrix with a density of only 8.9 g/cm³.

Every percentage point of cobalt added replaces heavier WC particles with lighter cobalt, reducing the composite density. This creates a predictable chain:

• Higher density → more WC per unit volume → higher HRA hardness → better abrasion resistance → lower toughness
• Lower density → more cobalt binder per unit volume → higher flexural strength (MPa) → better impact resistance → lower wear resistance

Ruixin’s three standard grades map this trade-off with measurable precision:

Variable	Pure Tungsten	WC Particle	SR7X Grade	SR8C Grade	SR10C Grade
Density	19.3 g/cm³	~15.6 g/cm³	14.70 ± 0.05	14.65 ± 0.05	14.45 ± 0.05
Hardness (HRA)	—	—	91.0 ± 0.5	89.0 ± 0.5	88.0 ± 0.5
Flexural Strength	—	—	≥2,000 MPa	≥2,200 MPa	≥2,200 MPa
Grain Size	—	—	1.0-1.2 µm	2.0-3.0 µm	2.0-3.0 µm

Grain size adds another dimension. SR7X uses 1.0-1.2 µm grains: finer microstructure that packs more WC into the same volume, contributing to its higher density and hardness. SR8C and SR10C use 2.0-3.0 µm grains, which improve fracture toughness at the cost of some hardness.

The relationship between cobalt content and hardness is inverse: increasing cobalt from approximately 6% to 12% drops HRA from ~92 to ~88, but flexural strength rises from ~2,000 to ~2,800 MPa. Density follows the cobalt curve — a grade at 14.70 g/cm³ has roughly 6% cobalt; one at 14.45 g/cm³ has roughly 10% cobalt.

For mining pick applications, the limiting constraint is impact energy — which means grades optimized purely for hardness (higher density) will underperform here regardless of price.

Grade Options and Performance Trade-offs — SR7X, SR8C, and SR10C

The density difference between Ruixin’s three standard grades is small at 0.25 g/cm³ from SR7X to SR10C — but the operational difference is large. Here is how each grade maps to specific working conditions.

Grade Selection Table

Application Scenario	Recommended Grade	Key Parameters	Why This Grade
High-abrasion, low-impact — e.g., road milling, steady-state rotary drilling in homogeneous rock	SR7X	Density 14.70 g/cm³, HRA 91.0, 1.0-1.2 µm grain, ≥2,000 MPa	Maximum tungsten content per volume resists abrasive wear; fine grain structure holds edge longer. Impact risk is low, so the trade-off toward hardness is safe.
Medium-impact, medium-abrasion — e.g., roadheader picks in mixed ground, shearer drums in medium coal	SR8C	Density 14.65 g/cm³, HRA 89.0, 2.0-3.0 µm grain, ≥2,200 MPa	Balanced formulation handles both wear and intermittent impact. Higher flexural strength than SR7X prevents sudden fracture when the tool encounters rock stringers.
High-impact, medium-abrasion — e.g., longwall shearers in hard coal with rock inclusions, TBM in fractured formations	SR10C	Density 14.45 g/cm³, HRA 88.0, 2.0-3.0 µm grain, ≥2,200 MPa	Lowest density signals highest cobalt content, delivering maximum toughness. The priority is surviving impact cycles — wear resistance is secondary.

The choice isn’t “which grade is better”: it is “which failure mode does your application punish more: wear or fracture?”

What the Wrong Grade Costs — Quantified

Selecting a grade by density without understanding its counterpart variables produces measurable losses.

• Tip life drops 30-50% when a high-density/low-cobalt grade is used in impact applications. The tips don’t wear out; they chip and fracture before reaching their wear potential.
• Replacement frequency doubles when fracture replaces gradual wear as the failure mode. A shearer drum that should run for three shifts between pick changes may require replacement every shift.
• Cost per meter rises 20-35% when the grade mismatch causes premature failure. The cost of the carbide itself is a fraction of the downtime cost to change picks in an underground longwall operation.
• Rod blank weight calculation errors occur when assumed density does not match the actual grade specification. A rod blank ordered at SR7X density (14.70 g/cm³) but manufactured in a lower-density grade will be lighter than expected, affecting tool holder balance and cutting dynamics in precision grinding applications.

These are not theoretical ranges. Ruixin has documented each of these outcomes across customer applications in coal mining, road milling, and tool grinding operations. The common thread: density was listed on the spec sheet, but nobody asked what it meant for their specific failure mode.

Exclusive Ruixin Data Point: Density and Rod Blank Weight Calculations

Here is a calculation that does not appear in any generic article about tungsten density.

A Ø20 mm × 330 mm carbide rod blank (a common size for tool grinding) has a volume of approximately 103.7 cm³. Using Ruixin SR7X density (14.70 g/cm³), that rod weighs 1,524 g. Using Ruixin SR10C density (14.45 g/cm³), the same rod weighs 1,498 g, a difference of 26 g per rod.

For a production order of 500 rods, the total weight variation between SR7X and SR10C is 13 kg. That affects shipping cost, customs declaration values, and, critically, the counterbalance specifications in multi-tool setups where rod weight consistency matters.

If your supplier lists only “tungsten carbide” as the material without specifying the grade density, you could be accepting ±0.25 g/cm³ variation without knowing it. Ruixin provides the density spec on every grade: SR7X at 14.70 ± 0.05 g/cm³, SR8C at 14.65 ± 0.05 g/cm³, and SR10C at 14.45 ± 0.05 g/cm³.

How to Implement This in Your Operation

Matching the density of tungsten metal to your application begins with one question: what is your primary failure mode?

If the carbide component is wearing away gradually (thinning, losing edge, reducing clearance), the density is too low for the abrasion level. Move toward SR7X (14.70 g/cm³, HRA 91.0). If the carbide is fracturing (chipping, spalling, shattering), the density is too high for the impact level. Move toward SR10C (14.45 g/cm³, HRA 88.0).

For tool grinders ordering rod blanks, confirm the density value on your material test report. A single grade designation without the measured density leaves room for batch variation that affects weight consistency across production runs. Ruixin provides a material test report with every batch that includes density, HRA hardness, and flexural strength. See our carbide rod blanks page for available dimensions and grade specifications.

For mining operators, the starting point is your pick failure pattern. If you are replacing due to wear, SR7X is the first candidate. If you are replacing due to fracture, start with SR10C. If you see a mix of both, SR8C at 14.65 g/cm³ is the balanced middle option. Our coal tooth carbide tips page covers the available geometries and OEM compatibility for shearer and roadheader picks.

For a deeper understanding of how cobalt content and grain size interact beyond density, read our full cemented carbide grade selection guide, which breaks down the microstructure variables that density alone cannot explain.

Frequently Asked Questions

How do I choose the right carbide grade based on density for my mining application?

Density alone does not determine grade suitability — it is a reliable indicator of the WC-to-cobalt ratio. Higher density means higher tungsten content and better wear resistance. For high-abrasion applications with low impact, choose a denser grade like Ruixin SR7X at 14.70 g/cm³. For high-impact conditions, accept slightly lower density (SR10C at 14.45 g/cm³) to gain the toughness the cobalt binder provides. Match the grade to your primary failure mode.

What is the difference between SR7X and SR8C in terms of density and performance?

Ruixin SR7X has a density of 14.70 g/cm³ with HRA 91.0 and 1.0-1.2 µm grain size — optimized for high wear resistance in low-impact applications. Ruixin SR8C has a density of 14.65 g/cm³ with HRA 89.0 and 2.0-3.0 µm grain size — a balanced grade for medium-impact conditions. The density difference of 0.05 g/cm³ reflects SR8C’s slightly higher cobalt content, which trades some wear resistance for impact toughness.

Which Ruixin grade performs best under high-impact mining conditions?

Ruixin SR10C at 14.45 g/cm³, HRA 88.0, and flexural strength ≥2,200 MPa is the highest-toughness grade in the standard range. Its lower density reflects higher cobalt content, which allows the carbide to absorb impact energy without fracturing. In longwall shearer applications with hard coal seams and intermittent rock inclusions, SR10C reduces tip fracture rates by up to 60% compared to harder, denser grades.

How does cobalt content affect cemented carbide density and performance?

Cobalt has a density of approximately 8.9 g/cm³, while tungsten carbide particles have a density of approximately 15.6 g/cm³. As cobalt content increases, the overall composite density drops because the lighter cobalt binder replaces heavier WC particles. A grade at approximately 6% cobalt reads 14.70 g/cm³, while a grade at approximately 10% cobalt reads 14.45 g/cm³. This density drop comes with higher flexural strength and impact resistance but lower HRA hardness and abrasion resistance.

What causes premature carbide tip failure in mining picks?

Premature failure is usually a grade mismatch rather than a quality defect. The most common pattern is using a high-hardness, high-density grade in an impact-dominated application — the tip is hard enough to resist abrasion but too brittle to survive the shock loads. Ruixin sees this most often when operators run grades equivalent to SR7X in conditions that require SR10C’s toughness. The failure shifts from gradual wear to sudden fracture, and replacement frequency doubles.

Is a higher density always better when selecting a carbide grade?

No. Higher density indicates higher tungsten content and therefore higher abrasion resistance, but it also signals lower cobalt content and lower flexural strength. In impact-dominated applications, a lower-density grade with more cobalt binder will outlast a higher-density grade because it resists fracture — which is the active failure mode. Density is one variable in a three-variable system that also includes grain size and cobalt percentage. No single spec number gives the full picture.

Get a Custom Grade Recommendation

The density of tungsten metal at 19.3 g/cm³ is a fixed property. The density of your cemented carbide grade is a design choice. Send us your application details (rock type, machine model, current grade designation, and failure photos if available), and our engineers will confirm grade selection and available dimensions within 24 hours. Custom grade formulations are available when your conditions fall outside the SR7X, SR8C, and SR10C standard specifications.

Email: info@ruixintungstencarbide.com
WhatsApp: +86-15253178777