What are Some Useful Alloys?

A metal product is obtained by mixing and melting a metal with another or several metals or non-metals, and cooling and solidifying the product. ^[1]

An alloy consists of two or more metals and metals or

Often two or more metal elements or metal-based addition of other non-metal elements through an alloying process (

According to the names of the major metals in the alloy, they are classified as certain alloys. For example, those with high copper content are copper alloys, and their properties mainly maintain the properties of copper.

There are thousands of alloys used in industry, and only a few of them are briefly introduced.

With the development of science and technology, the types of new alloys are increasing. Here are the main ones.

[1] Medium carbon steel: representative steel types are 30, 35, 40, 45, and also ML30, ML35, ML40, ML45, which have relatively stable room temperature performance, and are used for small and medium structural parts, fasteners, transmission shafts, gears, etc .
[2] Manganese steel: 40Mn2 and 50Mn2. It has susceptibility to overheating, high temperature tempering brittleness, easy cracking during water quenching, and higher hardenability than carbon steel.
[3] Silicon-manganese steel: representative steel grades 35SiMn and 42SiMn. High fatigue strength, decarburization and overheat sensitivity and temper brittleness. It is used to manufacture gears, shafts, rotating shafts, connecting rods, worms, etc. with moderate impact, medium and high load, but little impact. It can also manufacture fasteners below 400 ° C.
[4] Boron steel: 40B, 45B, 50BA, ML35B. It has high hardenability and comprehensive mechanical properties higher than carbon steel. It is equivalent to 40Cr in the manufacture of parts and fasteners with small cross-section dimensions.
[5] Manganese-boron steel: 40MnB. Hardenability is slightly higher than 40Cr, high strength, toughness and low temperature impact toughness, and temper brittleness. 40MnB is often used instead of 40Cr to make large cross-section parts, instead of 40CrNi to make small pieces; 45MnB instead of 40Cr, 45Cr; 45Mn2B instead of 45Cr and part of 40CrNi, 45CrNi as important shafts, and ML35 MnB is also used for fastener production.
[6] Manganese vanadium boron steel: Representative steel types are 20 MnVB and 40MnVB. The hardening and tempering properties are better than 40Cr, the tendency of overheating is small, and the tempering brittleness. It is often used instead of 40Cr, 45Cr, 38CrSi, 42CrMo and 40CrNi to make important quenched and tempered parts. It is also useful for small and medium size bolts below 10.9, ML20 MnVB.
[7] Manganese tungsten boron steel: 40MnWB. Good low temperature impact performance, no tempering brittleness. It is equivalent to 35CrMo and 40CrNi, and is used to manufacture parts below 70mm.
[8] Silicon-manganese-molybdenum-tungsten steel: Representative steel grade 35SiMn2MoW. It has high hardenability, calculated by 50% martensite, with a water quenching diameter of 180 and an oil quenching diameter of 100; its tendency to quench cracking and temper brittleness is small; it has high strength and toughness. It can replace 35CrNiMoA and 40CrNiMo, and is used to manufacture shafts, connecting rods and bolts with large cross sections and heavy loads.
[9] Silicon-manganese-molybdenum-tungsten-vanadium steel: Representative steel grade 37SiMn2MoWVA. Water-quenched diameter 100, oil-quenched diameter 70; good tempering stability, low temperature impact toughness, high high temperature strength, and low tempering brittleness, used to manufacture large cross-section shaft parts.
[10] Chrome steel: 40Cr

Castability (casting property) of an alloy refers to the process performance exhibited by the alloy during casting, and mainly refers to the fluidity and shrinkage of the alloy. These properties are important

Rumor: alloy is not pure

Israeli scientists discovered that quasicrystals enjoyed the 2011 Nobel Prize in Chemistry exclusively. The known quasicrystals are all intermetallic compounds. The laws concerning the composition and structure of quasicrystals are still being studied. It has been found that quasicrystals composed of aluminum-copper-iron-chromium have low friction coefficient, high hardness, low surface energy, and low heat transfer. Nozzle coating. The following statement is correct

A. B. Crystals formed by ionic compounds must have metal elements. There must be no non-polar bonds in covalent compounds

C. B. The alloy is pure D. Quasicrystals can be developed into new materials

(So-called) standard answer is D

The rumor comes from the seventh question of the middle school chemistry test paper in the third year (first) of the joint exam for the Jinlan Cooperative Organization in Ningbo, Zhejiang Province in the 2012-2013 school year.

Refutation: Of course, the alloy can be pure . For example, the known quasicrystals are intermetallic compounds ^[4] . This precisely illustrates the above-mentioned quasicrystal alloy Al65Cu23Fe12 as a fixed intermetallic compound (intermetallic compound). ) ^[5] , which is pure. The misconception that alloys are mixtures should not be used as knowledge points for spreading or burning so-called exercises. As the so-called "alloy is a mixture" in the following article is a fundamental scientific error , it should not be misled:

"Mastering the Keys to the Entrance Examination of" Metals and Metal Materials "" from "Mathematics, Physics and Chemistry of Middle School Students (Junior High School Edition. Senior High School Entrance Examination)" 2013 Issue 10 ^[6]