Bochem’s Basics of Metallurgy


What you should know about the use of metals

   Designations used in tables
1. Steel
Stahl Steel, ST37K

2. Stainless  steel
Chromium-nickel steel
18/10-stainless steel, antimagnetic
AISI-type 304-303
18% Cr + 10% Ni

  18/10 E-Poli
Chromium-nickel steel
18/10-stainless steel, electrolytical
polished, antimagnetic
AISI-type 304-303
18% Cr + 10% Ni
   V4A-Stahl Chromium-nickel-molybdenum steel
AISI-type 316
17% Cr + 12% Ni + 2% Mo

  Rostfrei Chrome steel, magnetic
AISI-type 430
17 % Chrom

3. Cast iron
Malleable cast iron
Cast iron

4. Aluminium
Aluminium alloy
Aluminium alloy

5. Nickel
Ni 99,5%
Pure nickel 99,5 %

6. Brass

7. Titanium
Ti Titanium

1. Steel

Steel refers to metallic alloys that consists mostly of iron and has carbon contents between 0.01 % and 2.06%. A simpler definition is: "Every iron that is forgeable without adding other substances can be referred to as steel".
In the register of European steels, more than 2,300 steel types are listed. The use of steels with its guaranteed characteristics such as strength, corrosion behaviour, mouldability and welding capability is very common in technology.

Bochem steel products:
Stand bases, rods for stand bases

Specific weight: 7.85 g/cm3
Melting point: 1460°C

2. Stainless steel

Stainless steel is a generic term referring to non-corroding steels. They contain at least 10.5% chromium (Cr) and exhibit a clearly higher corrosion resistance than unalloyed steels. Higher Cr contents and further alloy constituents, such as nickel (Ni), molybdenum (Mo), titanium (Ti) or niobium (Nb), increase the corrosion resistance.

Three main types can be distinguished:
1. Chromium steel (magnetic) = non-corroding
2. Chromium-nickel steel (not/slightly magnetic) V2A = 18/10 steel
V2A steel is the stainless steel type which is most frequently used in the lab. It contains 18% chromium and 10% nickel. Its material number is 1.4301 (X5 CrNi 18-10).
3. Chromium nickel molybdenum steel (not magnetic) V4A
V4A steel contains 18% chromium, 12% nickel and 2% molybdenum. Its material number is 1.4401 (X5 CrNiMo 17-12-2).

Since stainless steels were invented in the year 1912, manufacturers and processors have used different trade names, such as V2A, V4A, NIROSTA®, Remanit, Cromargan.

If maintained and cleaned properly, stainless steel has a very long lifetime.
For removing rust or cleaning, the following tools should be used: stainless steel wire brushes, plastic sponges, a stainless steel spray or scouring powder.

Bochem stainless steel products:
Stand materials, containers, lab jacks, furniture, stirrers, tools, etc.
Specific weight: 7.85 g/cm3
Melting point: 1400°C

3. Malleable cast iron

Malleable cast iron is a cast iron that is post-treated under certain conditions, since it is as brittle as glass after casting. Only after the heat treatment, malleable cast iron becomes hard and resistant. Tempering occurs at 1060°C over a period of 3 days.

Bochem malleable cast iron products:
Double bossheads, clamps, etc.

Specific weight: 7.25 g/cm3
Melting point: 1200°C

4. Aluminium

Aluminium is the most important metal of the range of light metals, i.e. those metals that have a specific weight < 3.5 g/cm3. The different aluminium alloys are mainly used because of their low weight.

Bochem aluminium products:
Clamps, bossheads, rods for stand bases, lab jacks, etc.

However, aluminium has a lower load bearing capacity than cast iron or stainless steel. In addition, aluminium is not very resistant to corrosion. An aluminium structure ages in a lab and loses stability. This should be considered when using bossheads and clamps for bigger structures with hazardous or valuable substances. For this reason, industrial labs do not employ aluminium zinc die-casts.

Specific weight: 2.7 g/cm3
Melting point: 658°C

5. Nickel

Nickel is a transition metal and has a shiny, metallic silvery appearance. It is mainly used for instruments and containers in analytics. To this end, a purity of 99.5% is crucial. If nickel is heated in air, corrosion occurs. Under inert gas, however, the transition metal is corrosion-free. Furthermore, nickel is a constituent of stainless steel (10-12%).

Bochem nickel products:
Crucibles, bowls, spatulas

Specific weight: 8.89 g/cm3
Melting point is 1455°C

6. Brass

Brass is a generic term for copper-zinc alloys with a copper portion between 55 and 90% and a zinc portion between 45 and 10%. Brass features an excellent mechanical strength (turning, milling, etc.).
In gas burners, all parts carrying gas are made of brass, since parts turned at a high precision are needed to achieve the required gas tightness. Brass changes its colour and, for this reason, the surface is often provided with a nickel-plating, chromium-plating or other coatings.

Bochem brass products:
Bunsen burners, Teclu burners, Meker-Fisher burners

Specific weight: 8.96 g/cm3
Melting point is 910 °C

7. Titanium

Titanium is particularly suitable for applications where high corrosion-resistance, strength and low weight are important. The metal has a white-metallic shine, featuring light weight as well as high strength, ductility, corrosion resistance and thermal resistance. Due to the complicated production process, titanium is ten times as expensive as normal steel. Titanium is resistant to diluted sulphuric acid, hydrochloric acid, solutions containing chloride, cold nitric acid as well as most organic acids and alkaline solutions, such as sodium hydroxide.

Bochem titanium products:
Forceps, tongs, spatulas, scissors

Specific weight: 4.50 g/cm3
Melting point: 1668°C