BS EN 14399-3 High Strength Structural Bolt Assembly

EN 14399 DIN 6914 ISO 7412 DIN 7990 structural Bolt

The Structural Bolts following EN 14399-4 , ISO 7412 and DIN 6914 is to use thinner Nuts and shorter thread lengths to obtain the required ductility by plastic deformation of the threads within the nut. The structural bolt assembly is used in both preloaded and non-preloaded applications and it can be argued that in the event of failure by thread plastic deformation the assembly still acts as a non-preloaded assembly. These assemblies are more sensitive to over-tightening during preloading and therefore require more site control. If severely over tightened during preloading the mode of failure by plastic deformation of the engaged thread of the bolt assembly offers little indication of impending failure.

Hot Forging  Bolts

We make Hot Forming/Forged Bolts through the Screw Forging and Hot Head Forging Machines.
The Hot Forming mostly done for Bolts having bigger diameter, longer length or special Head shape...

ISO 898-1 Specification

This part of ISO 898 specifies mechanical and physical properties of bolts, Screws and studs made of carbon steel and alloy steel when tested at an ambient temperature range of 10 °C to 35 °C. Fasteners — the term used when bolts, screws and studs are considered all together — that conform to the requirements of this part of ISO 898 are evaluated at that ambient temperature range. They might not retain the specified mechanical and physical properties at elevated temperatures (see Annex B) and/or lower temperatures.

ISO 898-1 Chemical Composition

Note:
a. In case of dispute, the product analysis applies.
b. Boron content can reach 0,005 %, provided that non-effective boron is controlled by addition of titanium and/or aluminium.
c. For cold forged fasteners of property classes 4.6 and 5.6, heat treatment of the wire used for cold forging or of the cold forged Fastener itself may be necessary to achieve required ductility.
d. Free cutting steel is allowed for these property classes with the following maximum sulphur, phosphorus and lead contents: sulphur 0,34 %; phosphorus 0,11 %; lead 0,35 %.
e. In case of plain carbon boron steel with a carbon content below 0,25 % (cast analysis), the minimum manganese content shall be 0,6 % for property class 8.8 and 0,7 % for 9.8 and 10.9.
f. For the materials of these property classes, there shall be a sufficient hardenability to ensure a structure consisting of approximately 90 % martensite in the core of the threaded sections for the fasteners in the “as-hardened” condition before tempering.
g. This alloy steel shall contain at least one of the following elements in the minimum quantity given: chromium 0,30 %, nickel 0,30 %, molybdenum 0,20 %, vanadium 0,10 %. Where elements are specified in combinations of two, three or four and have alloy contents less than those given above, the limit value to be applied for steel class determination is 70 % of the sum of the individual limit values shown above for the two, three or four elements concerned.
h. A metallographically detectable white phosphorus enriched layer is not permitted for property class 12.9/12.9. It shall be detected by a suitable test method.
i. Caution is advised when the use of property class 12.9/12.9 is considered. The capability of the fastener manufacturer, the service conditions and the wrenching methods should be considered. Environments may cause stress corrosion cracking of fasteners as processed as well as those coated.

ISO 898-1 Mechanical Requirements

Note:
a. Values do not apply for structural bolting.
b. For structural bolting d W M12.
c. Nominal values are specified only for the purpose of the designation system for property classes. See Clause 5.
d. In cases where the lower yield strength ReL cannot be determined, it is permissible to measure the stress at 0,2 % non-proportional elongation Rp0,2.
e. For the property classes 4.8, 5.8 and 6.8 the values for Rpf min are under investigation. The present values are given for calculation of the proof stress ratio only. They are not test values.
f. Proof loads are specified in Tables 5 and 7.
g. Hardness determined at the end of a fastener shall be 250 HV, 238 HB or 99,5 HRB maximum.
h. Surface hardness shall not be more than 30 Vickers points above the measured core hardness of the fastener when determination of both surface hardness and core hardness are carried out with HV 0,3.
i. Any increase in hardness at the surface which indicates that the surface hardness exceeds 390 HV is not acceptable.
j. Any increase in hardness at the surface which indicates that the surface hardness exceeds 435 HV is not acceptable.
k. Values are determined at a test temperature of −20 °C, see 9.14.
l.Applies to d W 16 mm.
m. Value for KV is under investigation.
n. Instead of ISO 6157-1, ISO 6157-3 may apply by agreement between the manufacturer and the purchaser.