Which one of the following elements is alloyed with iron to produce steel which can resist high temperatures and also have high hardness and abrasion resistance ?

1. Basics of Metallurgy and Metal Ores (basic)

Welcome to your first step in mastering everyday chemistry! To understand how the world around us is built—from the smartphone in your hand to the bridges across our rivers—we must start with Metallurgy. This is the scientific process of extracting metals from their natural sources and refining them for use. While elements are broadly classified into metals and non-metals based on properties like luster, malleability, and conductivity Science, Class X, Metals and Non-metals, p.37, most metals are rarely found in their pure state in nature. Instead, they exist as minerals—naturally occurring inorganic substances found in the Earth's crust.

When a mineral contains a high enough concentration of a metal to make its extraction economically profitable, we call it an ore. For example, iron is the backbone of industrial development, and India is endowed with high-quality iron ores like Magnetite and Hematite Contemporary India II, Class X, p.107. Understanding the difference between these ores is crucial for industrial application: High-grade ores require less processing and offer better physical properties for manufacturing.

Type of Ore	Iron Content	Key Characteristic
Magnetite	~70%	Excellent magnetic qualities; vital for the electrical industry.
Hematite	50-60%	The most important industrial ore by quantity used.

However, pure metals often lack the specific 'superpowers' needed for heavy-duty work. This is where alloying comes in. By mixing a metal with other elements, we can transform its properties. For instance, Tungsten is often added to steel to create high-speed steel. This alloy retains its hardness and resists wear even at elevated temperatures, making it indispensable for industrial cutting tools that generate intense heat during use. Metallurgy is thus the art of balancing chemistry and engineering to create the materials that define modern civilization.

Sources: Science, Class X, Metals and Non-metals, p.37; Contemporary India II, Class X, Minerals and Energy Resources, p.107

2. Introduction to Alloys (basic)

In their pure state, many metals are too soft or reactive for practical use. For instance, pure iron is very soft and stretches easily when hot. To overcome these limitations, we create alloys. An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal Science, class X (NCERT 2025 ed.), Metals and Non-metals, p.54. By carefully blending elements, we can "engineer" the properties of the material—making it harder, resistant to rust, or capable of withstanding extreme heat.

The process of making an alloy involves melting the primary metal first and then dissolving the other elements into it in definite proportions. This uniform mixing ensures that the individual substances cannot be seen with the naked eye, giving the material consistent properties throughout Science, class VIII (NCERT Revised ed 2025), Nature of Matter, p.118. For example, while pure iron rusts easily, adding Chromium and Nickel creates Stainless Steel, which is famous for its hardness and resistance to corrosion.

Different elements provide specific "superpowers" to the base metal. In the tool industry, where machines must cut through other metals at high speeds, Tungsten is added to steel to raise its melting point and maintain hardness even when the tool gets red-hot from friction Certificate Physical and Human Geography, GC Leong, Manufacturing Industry, p.284. This ability to retain strength at high temperatures is known as hot hardness.

Alloy	Primary Components	Key Property/Use
Brass	Copper + Zinc	Malleability and acoustic properties
Bronze	Copper + Tin	Strength; used since ancient Mesopotamia for tools/weapons
Steel	Iron + Carbon (0.05%)	Increased hardness and strength
Alnico	Iron + Aluminum + Nickel + Cobalt	Permanent magnets

Sources: Science, class X (NCERT 2025 ed.), Metals and Non-metals, p.54; Science, class VIII (NCERT Revised ed 2025), Nature of Matter: Elements, Compounds, and Mixtures, p.118; Certificate Physical and Human Geography, GC Leong, Manufacturing Industry and The Iron and Steel Industry, p.284; Themes in world history, History Class XI (NCERT 2025 ed.), Writing and City Life, p.12

3. The Chemistry of Iron and Steel (intermediate)

To understand the chemistry of iron and steel, we must start with the Blast Furnace, where the transformation from earth to metal begins. The process involves smelting iron ore with coke (a fuel and reducing agent) and limestone (a flux) at intense temperatures exceeding 1,650°C Certificate Physical and Human Geography, GC Leong, p.284-285. Chemically, this is a Redox reaction: the carbon in the coke strips oxygen from the iron ore to form carbon oxides (like CO and CO₂), leaving behind molten iron. Meanwhile, the limestone reacts with sandy impurities in the ore to form slag, which floats on top and is easily removed. This molten product, known as Pig Iron, is the raw material for all other forms but is quite brittle due to its high carbon content (around 3-4%).

The true 'chemistry' of everyday metal comes down to Carbon management. By refining pig iron to remove impurities and adjusting the carbon levels, we create different grades of iron. For instance, Wrought Iron is the purest commercial form, made by the puddling process to remove carbon until it becomes tough, malleable, and rust-resistant—perfect for ornamental gates Certificate Physical and Human Geography, GC Leong, p.285. Steel, however, is the sweet spot: it contains between 0.3% and 2.2% carbon, providing a balance of strength and flexibility that pig iron lacks.

The 'magic' happens when we add ferro-alloys to steel to give it specific properties. Think of these as chemical 'spices' that alter the metal's internal structure. For example, chromium is added for corrosion resistance (stainless steel), while Tungsten is the go-to element when you need hot hardness. Tungsten forms incredibly hard carbides that prevent the steel from softening even when it becomes red-hot from friction. This makes tungsten-containing steels indispensable for high-speed cutting tools and heavy-duty machinery Certificate Physical and Human Geography, GC Leong, p.285.

Type of Iron	Carbon Content	Key Characteristic
Pig Iron	~3-4%	Intermediate product; very brittle.
Cast Iron	High	Hard but snaps under pressure; used for lamp posts.
Wrought Iron	Very Low	Strong, tough, and highly rust-resistant.
Steel	0.3% - 2.2%	Versatile; properties modified by adding alloys.

Sources: Certificate Physical and Human Geography, GC Leong, Manufacturing Industry and The Iron and Steel Industry, p.284-285; Geography of India, Majid Husain, Industries, p.27; Science, class X (NCERT 2025 ed.), Carbon and its Compounds, p.58

4. Corrosion and Protection of Metals (intermediate)

To understand the chemistry of everyday objects, we must first look at why metal structures—from massive bridges to kitchen utensils—eventually degrade. This process is known as corrosion. It is defined as the gradual deterioration of a metal surface due to its interaction with the environment, specifically air, moisture, or chemicals Science-Class VII . NCERT(Revised ed 2025), The World of Metals and Non-metals, p.50. From a chemical perspective, corrosion is a redox reaction where the metal loses electrons (oxidation) to return to its more stable, naturally occurring state, such as an oxide or a sulfide. While the most famous example is the rusting of iron, corrosion affects many metals differently. For instance, iron reacts with oxygen and water to form a brown, flaky substance called hydrated iron oxide (rust) Science-Class VII . NCERT(Revised ed 2025), Changes Around Us: Physical and Chemical, p.62. In contrast, copper develops a characteristic green coating (basic copper carbonate) and silver turns black when it reacts with sulfur compounds in the air to form silver sulfide Science-Class VII . NCERT(Revised ed 2025), The World of Metals and Non-metals, p.50. Interestingly, the mechanism of corrosion often resembles a tiny Galvanic cell, where moisture acts as an electrolyte and different parts of the metal surface act as electrodes, allowing an electric current to facilitate the chemical breakdown Science, Class VIII . NCERT(Revised ed 2025), Electricity: Magnetic and Heating Effects, p.55. Protecting metals is a major industrial challenge because the economic cost of replacing corroded structures is enormous. Common methods include barrier protection (painting or oiling) and galvanization (coating iron with a layer of zinc). We also use alloying—mixing metals with other elements—to change their chemical properties. For example, Chromium is widely used as a corrosion protector for steel plates; it forms a thin, invisible layer of oxide that prevents further oxygen from reaching the metal underneath. However, we must be careful with the chemistry used: while Hexavalent Chromium (Chromium VI) is an effective hardener and corrosion protector, it is extremely toxic to the environment and can damage DNA Environment, Shankar IAS Academy, Environmental Pollution, p.93.

Metal	Corrosion Product	Typical Color
Iron	Hydrated Iron Oxide (Fe₂O₃·xH₂O)	Brown
Copper	Basic Copper Carbonate (CuCO₃·Cu(OH)₂)	Green
Silver	Silver Sulfide (Ag₂S)	Black

Sources: Science-Class VII . NCERT(Revised ed 2025), The World of Metals and Non-metals, p.50; Science-Class VII . NCERT(Revised ed 2025), Changes Around Us: Physical and Chemical, p.62; Science, Class VIII . NCERT(Revised ed 2025), Electricity: Magnetic and Heating Effects, p.55; Environment, Shankar IAS Academy, Environmental Pollution, p.93

5. Strategic Minerals and High-Tech Applications (exam-level)

In the world of high-tech manufacturing, strategic minerals are the unsung heroes that provide the backbone for advanced industrial and defense applications. These minerals are categorized as 'strategic' because they are essential for a nation's economic and national security, yet their supply is often vulnerable to disruption. While many minerals exist in nature as compounds with a fixed chemical composition, they rarely occur as pure elements Science, Class VIII NCERT, p.130. To harness their power, we use chemistry to extract them and blend them into alloys, creating materials with 'superhuman' properties.

Tungsten is a prime example of a strategic metal. It possesses the highest melting point of all metallic elements and is incredibly dense. In metallurgy, tungsten acts as a powerful alloying agent, particularly in the creation of High-Speed Steel (HSS). When added to steel, tungsten reacts with carbon to form hard, stable particles called tungsten carbides (WC). These carbides are dispersed throughout the steel, preventing the metal grains from shifting even under intense stress. This results in hot hardness (also known as 'red hardness') — the remarkable ability of a tool to remain sharp and hard even when it is glowing red from the heat of high-speed friction.

Beyond its hardness, tungsten-containing steels offer exceptional abrasion resistance, making them indispensable for tools that must cut through other metals or withstand extreme wear. While other metals like nickel and chromium are added to steel to increase resistance to shock and corrosion Certificate Physical and Human Geography, GC Leong, p.284, tungsten is the go-to element for maintaining structural integrity at high temperatures. In the Indian context, the management of such vital resources is governed by a federal structure where the Central Government frames the regulations for mineral development (falling under the Union List), while State Governments generally own the minerals and collect royalties Indian Economy, Vivek Singh, p.427.

Sources: Science, Class VIII NCERT, Nature of Matter: Elements, Compounds, and Mixtures, p.130; Certificate Physical and Human Geography, GC Leong, Manufacturing Industry and The Iron and Steel Industry, p.284; Indian Economy, Vivek Singh, Infrastructure and Investment Models, p.427

6. Common Steel Alloying Elements (Cr, Ni, Mn) (intermediate)

Pure iron is remarkably soft and stretches easily when hot, making it impractical for most industrial uses. To transform it into a versatile material, we mix it with other elements to create alloys—homogeneous mixtures that modify the physical and chemical properties of the base metal Science, Class X, Metals and Non-metals, p.54. While adding just 0.05% Carbon makes iron hard and strong, adding metals like Chromium (Cr) and Nickel (Ni) creates Stainless Steel, which is famous for its hardness and its refusal to rust Science, Class VIII, Nature of Matter, p.118.

Each alloying element serves a specific purpose in modern engineering. Chromium is the primary defense against corrosion; it reacts with oxygen to form a thin, invisible protective layer that prevents further oxidation or "rusting" Science, Class X, Chemical Reactions and Equations, p.13. Nickel adds toughness and resistance to heat and shock, making the steel reliable under extreme pressure or temperature changes Certificate Physical and Human Geography, Manufacturing Industry, p.284. Meanwhile, Manganese (Mn) is often used to increase the strength and hardness of the steel during the manufacturing process by removing impurities like oxygen and sulfur.

For specialized industrial applications, such as high-speed cutting tools, we introduce Tungsten (W). Tungsten is unique because it provides hot hardness (also known as red hardness). While ordinary steel softens when it gets hot due to friction, tungsten-containing steels maintain their razor-sharp edges and structural integrity even at glowing temperatures. This makes it indispensable for drill bits and heavy-duty machinery that must endure high abrasion and intense heat.

Alloying Element	Primary Benefit	Common Application
Chromium	Corrosion resistance (Anti-rust)	Cutlery, medical tools, car trim
Nickel	Toughness and heat resistance	Springs, aircraft engines, heavy machinery
Tungsten	Hot hardness and wear resistance	High-speed cutting tools, drill bits

Sources: Science, Class X (NCERT 2025), Metals and Non-metals, p.54; Science, Class VIII (NCERT 2025), Nature of Matter, p.118; Certificate Physical and Human Geography (GC Leong), Manufacturing Industry, p.284; Science, Class X (NCERT 2025), Chemical Reactions and Equations, p.13

7. Tungsten: Properties and 'Red Hardness' (exam-level)

When we think of Tungsten (symbol W), the first thing that usually comes to mind is the glowing filament inside a traditional light bulb. This application exists because Tungsten possesses one of the most extreme physical properties in the natural world: a melting point of 3380°C Science, Class X (NCERT 2025 ed.), Electricity, p.190. At temperatures where most metals would have long since turned into liquid or even vapor, Tungsten remains a solid, emitting light through incandescence without melting.

Beyond light bulbs, Tungsten is a critical player in metallurgy due to its role in creating alloys. While pure metals are often soft, adding Tungsten to steel creates a material with exceptional hot hardness, also known as 'Red Hardness'. In industrial settings, when a drill bit or a saw blade cuts through metal at high speeds, the friction generates intense heat, often making the tool glow red. Most steels would soften and lose their cutting edge under such heat, but Tungsten-containing "high-speed steels" maintain their structural integrity and sharpness even when red-hot. This is because Tungsten forms incredibly hard carbides within the steel’s microstructure, which act as a heat-resistant skeletal frame.

Property	Pure Tungsten	Tungsten-Alloy Steel
Primary Use	Lamp filaments, X-ray targets	High-speed cutting tools, drill bits
Key Advantage	Extreme melting point (3380°C)	Red Hardness (retains strength at high temp)
Chemical Behavior	Does not oxidize easily Science, Class X (NCERT 2025 ed.), Electricity, p.179	Forms stable, hard carbides

Interestingly, while Tungsten is a good conductor, it has a higher resistivity than copper or aluminium Science, Class X (NCERT 2025 ed.), Electricity, p.194. This resistance is actually a feature, not a bug—it allows the filament to heat up significantly (Joule heating) to produce light. To prevent the hot metal from reacting with oxygen and burning out, these bulbs are usually filled with chemically inactive gases like Nitrogen or Argon Science, Class X (NCERT 2025 ed.), Electricity, p.190.

Sources: Science, Class X (NCERT 2025 ed.), Metals and Non-metals, p.39; Science, Class X (NCERT 2025 ed.), Electricity, p.179, 190, 194

8. Solving the Original PYQ (exam-level)

Review the concepts above and try solving the question.