DIN 8555


E 23 UM 250 CKNPTZ
1 2 3 4 5


1 Short symbol for manual arc welding


2 Short
Alloy group and application
1 Unalloyed up to 0.4% C or low-alloyed up to 0.4% C and up to max. 5 % alloy constituents Cr, Mn, Mo, Ni in total; soft surfacing, e. g. fill-up welding, buffering layers
2 Unalloyed with more than 0.4% C or low-alloyed with more than 0.4%C and up to max. 5% alloy consitutents Cr, Mn, Mo, Ni in total; running wheels
3 Alloyed, with the properties of hot working steel, hot working tools
4 Alloyed, with the properties of high-speed steel, cutting tools, mandrels, shear blades, cutters, drill bits
5 Alloyed with more than 5% Cr and low C-content (up to approx. 0.2%C) for scale-resistant (also against sulphurous gases) and from 12% Cr-content corrosion-resistant surfacings, e. g. valve parts, plungers, furnace parts
6 Alloyed with more than 5% Cr and higher C-content (approx. 0.2 - 2.0% C) cutting tools, shear blades, rollers for cold rolling mills
7 Mn austenite with 11 to 18% Mn and more than 0.5% C and up to 3% Ni surfacings on large surfaces, e. g. wear plates, jaw plates, digging teeth, bolts
8 Cr-Ni-Mn-austenite crusher parts for medium stress, switch tongue, rails, water turbine parts
9 Cr-Ni-steel (corrosion and heat resistant) corrosion and heat resistant surfacings
10 High C-content and high Cr-alloyed with and without additional carbide former, repairs on mining and steel plant equipment, surfacing on machine parts in the construction industry and agriculture, overburden excavators, sinter crushers
2 20 Co-based, Cr-W-alloyed, with or without Ni and Mo fittings of all tpyes, valve seats of exhaust valves in combustion engines, valve seats of steam engines, pump shafts and similar parts which are exposed to heavy corrosion and erosion
21 Carbide-based (sintered, cast or folled) tools and machine parts for working in stony earth, drills and similar tools, press schrews in the ceramic industry
22 Ni-based, Cr-alloyed, Cr-B-alloyed valves, screws,shafts, e.g. for concrete pumps
23 Ni-based, Mo-alloyed with or without Cr hot working tools, contact surfaces of valves in chemical apparatuses, claddings at working edges of cuttings from Ni-Cr-Mo-alloys which are used for work at high temperatures
30 Cu-based, Sn-alloyed bearing shell, slides, shafts, valves, housings, snail and helical gear wheels, guide and running wheels, fittings
31 Cu-based, Al-alloyed machine parts and fittings in the chemical industry, food, paper and electrical industry
32 Cu-based, Ni-alloyed distillators, sea water pipes, condensers, coolers, chemical apparatuses, heat exchangers


3 Symbol Type
GW rolled
GO cast
GZ drawn
GS sintered
GF filled
UM coated


4 Classification of hardness
Hardness class Hardness degree
40 37 – 42 HRC
45 >42 – 47 HRC
50 >47 – 52 HRC
55 >52 – 57 HRC
60 >57 – 62 HRC
65 >62 – 67 HRC
70 >67 HRC
150 125 – 175 HB
200 >175 – 225 HB
250 >225 – 275 HB
300 >275 – 325 HB
350 >325 –375 HB
400 >375 – 450 HB


5 Symbol Properties of weld metal
C corrosion-resistant
G abrasion-resistant
K work-hardenable*1
N non-magnetizable
P impact-resistant
R stainless
S edge-holding (high-speed steel)
T creep-resistant (high-speed steel)
Z heat-resistant (temp. > 600 C)
*1 The wear properties of the weld metal depend on a work-hardening after-treatment. It can be achieved by subsequent hammering or pressing, but also without such after-treatment if the weld metal is exposed to compressive stress, rolling or impact stress during operation