AXE STREAM exclusive hand-made ax by Serhiy Dytyuk, U8 tool steel 60-62 HRC

 U8 steel: characteristics, interpretation, chemical composition

Specific weight:  7839 kg/m  ³
Heat treatment:  Hardening 780  ^o  C, oil, Tempering 400  ^o  C.
Material hardness:  HB 10  ^-1  = 187 MPa
Temperature of critical points:  Ac  ₁  = 720 , Ar  ₁  = 700 , Mn = 245
Tempera forging, °C:  beginning 1180, end 800. Sections up to 100 mm are cooled in the air, 101-300 mm in a pit.
Machinability by cutting:  at HB 187-227,  in  ₌  620 MPa, To  _{tvv. spl}  =1.2 and K  _{? b.st}  = 1.1
Weldability of the material: not applicable for welded structures.
Fluke sensitivity:  insensitive.
Tendency to release brittleness:  not prone.

Characteristics of steel U8

Steel 09G2S decoding of marking:

• "U" - tool steel, quality unalloyed steel;

• "8" is the percentage of carbon.

Chemical composition of U8

Mass fraction of U8 steel elements according to DSTU 1435-99

Group 3: Cr 0.20 - 0.40. For steel produced by the scrap process, increased mass fractions of Ni, Cu, Cr by 0.05% of each element are allowed.

In this steel, the only alloying additive that affects the properties is carbon, the rest of the additives fall into the composition of the metal, they are impurities (silicon and manganese - during melting, nickel, chromium and copper - as a result of melting scrap metal). However, they often contribute to an increase in the quality of calcination (of course, a little), which has a negative effect on some uses (for example, in the manufacture of wire).

Mechanical properties of U8 steel

The hardness of steel depends on the tempering temperature

The mechanical properties became dependent on the test temperature

Properties according to the DSTU 1435-99 standard

Hardness of steel after heat treatment

Properties according to the DSTU 2283-79 standard

Physical properties of U8

Preliminary heat treatment has a significant effect on the properties of steel, it provides an optimal structure. This steel is extremely sensitive to the type of hardening medium, therefore cooling is carried out in 2 media, water-oil.

Properties according to the TU 14-19-81-90 standard

Density, g/cm  ³  :  7.81*

* Typical property value for low-carbon and low-alloy steel. This value is not prescribed by the standards, it is indicative and cannot be used for design purposes

Technological properties of the U8 brand

Heat resistance

Incandescence

The U8 alloy is characterized by high hardness of the surface layer, and low wear resistance. A poor indicator of a small degree of heat resistance leads to the fact that steel is not used for the production of tools with a cross-section of more than 20-25 mm, as well as parts of equipment operated in continuous mode and temperatures above 200 °C.

Also, U8 steel is not intended for welding. But it lends itself perfectly to blacksmith welding.

The steel of the brand is not flake-sensitive, and is easily subjected to any kind of treatment when heated.

Deciphering the U8 steel grade:  the letter U indicates that we have a tool-quality unalloyed steel in front of us, which contains carbon in an average amount of 0.8%.

U8 steel tool and its heat treatment:  locksmith hammers are made of U7 and U8 steels. The battlements and the tail are subject to hardening. Heating is best done in a salt or lead bath. When heating the hammer in a chamber furnace, the hammer is first hardened, and then the tail, after which it is alternately cooled until the middle part is completely darkened. For final cooling, the hammer is transferred to oil. Bake at 260-340 ° for 30-40 minutes. Hardness R  _c  = 49-56. The hardness is checked on the RV device.

U8 or U7 steel is used for the manufacture of pneumatic tools. The working tail part is subjected to hardening. You should avoid heating the pneumatic tool completely, so it is best to heat it in salt or lead baths. The working part is hardened in water with transfer to oil, and the tail part in oil. After that, the tool is tempered depending on the required hardness of the working part, namely: chisels, cross chisels, punches, embossing and notches are tempered at 240-270 ° with a holding time of 30-40 minutes. Required hardness R  _c  = 56-59.

Crimping, support, fighting and knocking out are released at 270-300 ° for 30-40 minutes. Required hardness R  _c  = 53-56. Determine the hardness with a calibrated file. There are rare cases when a pneumatic tool breaks during operation at the point of transition from a smaller diameter to a larger one, and the fracture structure is very fine-grained to a depth of 5-8 mm around the circumference, and coarse-grained deeper. The main cause of breakdowns is insufficient cleanliness of the surface at transition points (risks, scratches, etc.).

Machine tool bits are made of U8, U9, 65X steels. The place of transition from the thin part of the bit to the thick part, as well as the walls of the hole in the hollow bit, should be hardened to a small hardness. If this is not observed, the bit may bend or break during operation. A slight transition hardness is achieved by intermittent water quenching for solid carbon steel bits, or full quenching followed by salt bath quenching to gray runout for all other bits. The tail part is not hardened. Solid chisels are fired at a temperature of 260-280 °, and hollow ones at 320-360 °; keep for 20-30 minutes. The required hardness for false bits is R  _c  = 56-58, and for hollow bits R  _c  = 50-52.

Carpentry and carpentry chisels and chisels are made from the same steels. Heat for hardening is produced in furnaces-baths with a length of 60-80 mm. When heating chamber furnaces, the tool is soaked for a length of 60-80 mm. The tail part is not hardened. Leave at a temperature of 250-300° for 20-40 minutes. Required hardness R  _c  = 53-58.

Combined pliers and nippers are made of U7 and U8 steels. They are subjected to heat treatment in assembled form with open jaws, only the working part is cut - in nippers, the length of the sponge is 8-10 mm, and in the combined pliers, the length of the sponge is included, including the slots in the hinge. Cool in oil or kerosene with vigorous stirring. The leave is produced at a normal temperature of 220-300° for 30-40 minutes. Hardness R  _c  = 52-60. The hardness is controlled on the RV device or with a calibrated file, as well as by biting off a steel wire with a diameter of 2 mm.

Stamps are made of the above-mentioned steels, hardened with subsequent tempering at a temperature of 220-250°. The stem is released by heating in a lead bath until the gray color of the escape. The required hardness of the working part R  _c  =54-58.

Additional characteristics of U8

Welding of U8 steel

Forge welding is possible - the process of inseparably joining heated pieces of metal with the application of external pressure. Form of delivery of steel U It is delivered in the form of forged strips, hot-rolled circles, squares and forged circles, sheets.

Field of application

It is mainly used for the production of tools, the operation of which does not require heating of the cutting edge: milling cutters, axes and chisels, countersinks, saws and chisels, cornerers, screwdrivers, nippers, pliers, etc.

Application of U8 steel taking into account characteristics and properties

This steel is used as an indispensable raw material for the manufacture of tools, the operation of which does not require heating. These are pneumatic, woodworking, metalworking and assembly tools - corers, nippers and screwdrivers, rollers, pliers, milling cutters, parts of watch mechanisms and springs, etc. All these products require special heat treatment, often using individual technology.

Steel analogues U8

U8 steel tools and types of their heat treatment

This steel is very sensitive to the type of processing, so there are no single recommendations. Locksmith's hammers made of U8 steel are hardened in the area of ​​the striker and tail. Heating is carried out in a salt or lead bath. Leave at 260-340 ° C for 30-40 minutes.

In the production of pneumatic tools, the working part - the tail - is subjected to hardening, and heating the entire tool is contraindicated. Vacation is performed depending on the required hardness of the working sector (individually for different tools).

For chisels, Kreuzmeisels, and punches, the vacation is carried out in the mode of 240 °C -270 °C with a holding time of up to 40 minutes. And for fighters, knockers - 270 °С -300 °С. When hardening the bit for the U8, U9, 65X machines, the sections of the transition from the thin area to the thick one, and the walls of the hole are made to a small degree of hardness. This is achieved by intermittent hardening in an aqueous environment. The tail section is not subjected to hardening. Carpentry and carpentry chisels and chisels are heated for hardening in furnaces-baths to a length of 60-80 mm. The tail section is not subject to hardening