Steel U10A

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Steel U10A

Steel U10A

U10A steel is a carbonsteel.

The letter “U” at the beginning of the marking means “carbon steel”,The letter” A “in the end – high-quality steel.

Figure “10” shows the average fraction of carbon in steel, expressed in tenths of a percentage point.

U10A grade refers to high-quality steels.

The quality carbon steel of the series starting with the letter U is often used to make tools and is characterized by high strength and toughness.

They are steels necessarily subject to multi-stage heat treatments,it is not recommended to perform a hardening with the forge but using a hardening and extinguishing furnace in saline solutions or have it hardened by a specialized company.

To improve the quality of mechanical and technological indicators, instrumental steels are subjected to multi-stage heat treatment:

  • annealing of the raw material prior to the manufacture of the blade or tools;
  • hardening (cooling in saline solutions) and subsequent tempering of the blade or tool.
  • Verification of the hardness obtained even if it is not always enough to check only the hardness but this in general.

The properties obtained are determined by the chemical composition and the microstructure obtained: martensite with cementite and austenite inclusions.

Carbon content in steel: 0.7 – 1.3%.

For qualitative – up to 0.03%, phosphorus – up to 0.035%.

And for high instrumental quality: sulfur – up to 0.02%, phosphorus – up to 0.03%.

Classification of carbon steel

All steel that exists on the world market can be divided into carbon and alloyed.

All grades of carbon steel are divided into different classes of the classifier and the characteristics of the designation.

Proceeding from the main characteristics of classification, they distinguish:

  1. Structural carbon steel where the carbon content is less than 0.8% and are used for the production of reinforcement, rolled products and casting.
  2. Carbonaceous tool steels that contain carbon in the amount from 0.7% to 1.3% and are used for instruments, instrumentation.

By deoxidation methods:

  • boiling elements – deoxidation (RE) in the composition less than 0.05%;
  • Semi-calm – 0.05% ≤РЭ≤0.15%;
  • calm – 0.15% ≤РЕ≤0.3%.

By chemical composition:

  • low carbon content (0.3% ≤ C);
  • medium carbon (0.3 ≤ C ≤ 0.65%);
  • High carbon content (0.65 ≤ C≤1.3%).

Steels containing more than 1.3% carbon are not used in industry.

Depending on the microstructure:

  • pre-eutectoid: in such carbon steel in the composition of less than 0.8%;
  • eutecettoid – steel with a carbon content of 0.8%;
  • hypereutectoid – steel with a carbon content of more than 0.8%.

By quality:

  1. Ordinary quality Sulfur here contains less than 0.06%, phosphorus – no more than 0.07%.
  2. Quality steel. They do not contain sulfur and phosphorus more than 0.04%.
  3. High quality. The amount of sulfur here does not exceed 0.025%, and phosphorus – no more than 0.018%.

According to the basic standard, the grades of carbon steel are distributed to:

  • build quality;
  • instrumental quality;
  • high quality instrumental.

High-quality instrumental steels are used in cutlery

Explanation of the brand UXXA or GOST 1435-74:

  • U – carbon instrument;
  • 7 -13 – the carbon content in it is 0.7-1.3%, respectively;
  • D – presence of manganese in the composition;
  • A – high quality.

The chemical composition according to U10A or GOST 1435 is as follows:

  • carbon – 0.95-1.09,
  • silicon – 0.17-0.33,
  • manganese – 0.17-0.28,
  • sulfur – 0.018,
  • phosphorus – 0,025



U10A belongs to the instrumental carbonaceous.

Due to its characteristics it is close to U11 and U12 steels.

It has poor weldability, so it is not used for welded structures, is not sensitive to flakes, is not subject to fragility from tempering and is well polished.

Compared with u8a, it has greater hardenability during heat treatment, has a high surface hardness, which after hardening has a value of 58 – 60 HRC.

It does not react to small temperature deviations and the duration of individual heat treatment transitions therefore it can be applied even in non-specialized areas.


U10A steel is used for the production of cores and various cutting tools that work without overheating the sharp parts.

From it are obtained hand and blacksmith tools, such as hand or machine saws, taps, needle files, rasps, axes, calipers, godroni, files, needle files, scrapers, needle wire, working parts of automatic cold forgingmachines:

unloading, header, edging and cutting, as well as cold rolled tape used for the manufacture of springs and spring parts of various configurations, as well as valves, probes, various small watchmaking parts, etc.

It is a steel that is also used in cutlery and can be a good alternative for those who want knives with quality carbon steel.

Examples of use of carbonaceous steels for tools

The described steel is used to make all kinds of tools: cutting, percussion, auxiliary.

  • Steel U7, U7A – hammers, chisels, axes, fishing hooks.
  • Steel У8, У8А, У8Г – saws, screwdrivers, punches, flarers, cutters, pliers.
  • Steel U9, U9A – tool for metals, a tool for cutting wood.
  • Steel U10, steel U10A, U11, U11A – rasps, taps, helical tips, auxiliary tools for punching and calibration.
  • A 12, V12A – scans, taps, measuring instruments.
  • У13, У13А – files, shaving and surgical instruments, stamping punches.


This steel produced by Uddeholm, the Sleipner is a fantastic carbon steel with excellent qualities of resilience and tightness of the wire, it can be simplified by saying that it is a steel similar to D2, but with all the increased parameters.
A rational and careful choice of the brand of carbon steel, the understanding of the technology of its heat treatment, the understanding of its properties and characteristics for a create knives and tools manufactured, processed or used with reliability and over time.
U10A steel is one of the highest quality carbon steels in the top ten carbon steels.

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110 shares, 110 points
Andrea F

Maker and Enthusiast of Knifemaking. Other: Engineer / Professional Blogger / Bass Player / Instructor of Boxing / Muay Thai / Brazilian Jiu Jitsu / Grappling / CSW / MMA / Self Defence / FMA / Dirty Boxing / Silat / Jeet Kune Do & Kali / Fencing Knife / Stick Fighting / Weapons / Firearms. Street Fight Mentality & Fight Sport! State Of Love And Trust!


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