UNI 7845-78-EN

Cr – – – – – – – – 0.901.20 1.001.30 0.801.20 0.901.20 0.801.10 0.901.20 0.901.20 0.400.60 0.601.00 0.600.90 0.601 – – – – – – – – – – – – – 0.400.70 0.701.00 1.601.90 2.603.20 3.704.20
3.1.3
3.1.4
3.2 3.2.1
3.2.1.1 The chemical composition of the casting must correspond to the limits of chemical composition reported in prospectus I for every steel quality. 3.2.1.2 The mechanical characteristics and jominy hardening values, which, in relation to the types of steel supply (see 5.3 prospectus VII) are useable for the test, are indicated respectively in prospectus II and prospectus IV. For the supply types from no 3 to no 3e small deviations in the chemical composition of casting with respect to values reported in prospectus I are accepted provided that the values of the mechanical character of pros IV are abided.
UNSIDER
Steel products, bars & coils, for quenching tempering - qualities, requirements and tests
UNI 7845
The present norms agree partially with the recommendations ISO 683, parts from I to VIII & EURONORM 83 (see clarifications) 1. Field of application The present norms concern the hot rolled, unalloyed and alloyed construction steel bars and coils for use of parts at quenching and tempering stage. One should pay attention on the primary importance of effect on mass in thermal treatment during quenching and tempering and its repercussions on the mechanical characteristics of the finished product, which change in relation to the dimensions. The mechanical characteristics shown in prospectus II refer to test prescriptions (Heat treatment, shape and dimensions determined by arc bar) which can differentiable itself from those of finished products. This norm does not apply to products for particular use for which any distinct norms exist (for example steel used for surface heat treatment) 2. Definitions and classification For the definitions and classifications and steels, see UNI EU 20. For the definition and classification of steel products as per shape and dimensions see UNI 7272. 3. 3.1 3.1.1 3.1.2 Material Steel processing procedure and fabrication process of product The steel in the present norm must be stabilized. Except for different agreement at the time of order, the steel processing procedure and the product fabrication process are left to choice of the producer. Special procedure, like degassing, vaccume or remelting process, must be agreed upon between the parties at the time f order Except for different agreement at the time of order, hot reduction must be such as to guarantee a correct metallurgical reduction, as a relation between the average transversal area section of the useful part of the ingot or of semi finished and area section of finished product. Chemical composition Casting analysis
Non alloyed
Alloyed Cr Alloyed Cr-Mn Alloyed Cr-V
Alloyed Cr-Mo
35CrMo4 42CrMo4 40NiCrMo2 39NiCrMo3 40NiCrMo7 30NiCrMo12 34NiCrMo16
0.220.29 0.270.34 0.320.39 0.380.45 0.370.44 0.350.43 0.370.44 0.280.35 0.310.38
Alloyed Ni-Cr-Mo
Other elements non indicated in prospectus should not be intentional added to steel, with exception of those to be processed in casting, all precautions must be adopted to avoid adding of elements coming from scrap and other raw material used during procuring, but residual elements may be present as long as harness & mechanical characteristics are obtained and use of product is not compromised. On request they can be supplied with addition of lead (0.15 0.30%) or sulfur (0.020 -+ 0.035%) for high speed mechanical working. On request higher amount of molybdenum (0.60%) can be supplied and eventually with addition of vanadium. These steel are not previewed in euronorm 83.

Group
Steel Quality C25 C30 C35 C40 C45 C50 C55 C60 41Cr4 36CrMn5 50CrV4 25CrMo4 30CrMo4
Mn 0.400.80 0.500.80 0.500.80 0.500.80 0.500.80 0.600.90 0.600.90 0.600.90 0.500.80 0.801.10 0.701.10 0.500.80 0.400.70 0.600.90 0.600.90 0.701.00 0.500.80 0.500.80 0.500.80 0.300.60
Si 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40 0.150.40

5.4.1.2 For the defect class B, if not specified differently at the time of order, in case of corrugated rods, if the depth of the defects is more that what indicated above, the repairing is accepted using grinding or mechanical scarfing provided that reaper results in smooth, well in agreement with rest of the surface and with A depth not more than 4% of the nominal diameter and total width not more than 1/4 of the circumference. 5.4.1.3 For the finished product of the other dimensions or other shapes the depth of the tolerable surface defects should be agreed at the time of order in relation to the use of product. 5.4.2 The surface of the product supplied at the peeled rolled peeled or rectified state must be without defects. 5.4.3 In case of dispute the measure of the depth of the defect is done using microscopic examination on a tasversal section of the sample of product and with grading 100 X. 5.5 Internal defects The use of appropriate techniques for studying eventual internal defects and the guarantee of their absence or limitation, purely as modalities for interpretation of techniques indicated ahead, must be agreed upon at the time of order where necessary. 5.6 Thermal treatment The prospectus VI reports the temperature for the quenching tempering treatment of arc bars of the single steel for the tests and the temperature for the Jominy test. 6. 6.1 Test Generality For all the finished products foreseen in the present norm can be agreed upon to do the check at the test as per point 5 of the UNI 5447. 6.2 Test unit The finished products must be checked for casting and where possible they are supplied at quenched and tempered state (supply type 5), for heat treatment lot and group of same diameter. 6.3 Chemical composition If agreed upon at the time of order, the casting analysis is communicated to the customer. Where, in case of type of supply no 1, no 1c and no 1e, the customer requests a check of the product, one must at least do a survey for casting. 6.4 Brinell strength and mechanical characteristics For the strength test (supply type no 1c, no 1e, no 2c, no 2e, no 3c, no 3e, no 4c and no 4e) and for the checking of mechanical characteristics on the test pieces of quenched and tempered arc bar (supply type no 3, no 3c, no 3e, no 4, no 4c, no 4e) the number of test to do are indicated in prospectus IX. Prospectus IX - Test to do number of test Test unit mass (In same casting) t till 50 Above 50 till 100 Above 100