The production of machined and welded parts for automobile construction prompted Don Foster to make a particularly selective choice among steel grades. From the company's many years of experience, it has been found that 15CDV6 is the best option for resolving the technical and economic problems that arise today.

IMPLEMENTATION OF 15CDV6
Machining in the annealed or treated state does not generate any particular difficulties.
In the treated state, steel can be rolled or bent with radii greater than 2.5 times the thickness.
Heat treatment has been defined specially to obtain excellent results by fluo-turning.
Similarly, deep stamping requires special annealing for the stamping techniques.

WELDING
15CDV6 steel is remarkably suitable for every welding process, whether oxyacetylene, electric, arc, resistance, electron beam or laser.
The main coated electrode manufacturers have defined rods with a special grade that are totally suitable and offer the same strength in the joint.

Soudure Autogène Française: Electrode Safer CDV 100
ESAB: Electrode OK 78-05

PFor torch or argon welding (TIG or MIG), a flux wire has been produced using slag and copper coating conforming to standard Air 9114.
No preheating is needed to a thickness of 10 mm, and welding in the treated state is just as easy as for annealed metals. After welding, there is no excessive hardening of the cord requiring stress-relief treatment.
Indeed, the presence of molybdenum and vanadium means that the annealing effect near the cord, affecting the mechanical strength of steel welded assemblies, is almost insensitive when 15CDV6 is used. The strength of the treated metal is maintained intact within the cord and around it, so that assemblies with consistent strength exceeding 1,000 MPa can be obtained without any heat treatment.

This unique property is confirmed by the thousands of rolled and welded power plants envelopes that have been produced in which the welded generating line is put through the same stresses as the base metal.

MIXED ASSEMBLIES
One major advantage of 15CDV6 steel is that it can be assembled, by welding, with other grades of steel.
For similar grades like 25CD4S, there is naturally little difficulty, but it can equally well assemble very different steels or alloys. For instance, for ballistic device construction, calling for structural hardening stainless steel, 15CDV6 steel not only welds very well with them, but preserves its properties after complex treatment.

There are also application where Z10CNT18 stainless steel is welded with 400CDV-20-25CD4S-XC18S steel, etc.
15CDV6 has replaced in the AIR 9160/C standard the 25CD4S steel because of its higher performance, whether in terms of weldability, suitability for tempering, or mechanical properties.
L'ASSOCIATION EUROPEENNE des CONSTRUCTEURS de MATERIELS AEROSPATIAL (AECMA) has standardized it under the designator FE-PL 52 S.

STEEL PROPERTIES, ESPECIALLY 15CDV6

MECHANICAL CHARACTERISTICS ON SHEET METAL

By tempering and annealing in air, tensile strength of between 980 and 1,180 MPa is obtained for sheet metal less than or equal to 8 mm in thickness. Beyond this thickness, 15CDV6 is still worth considering. Accordingly, the minimum strength of 1,000 MPa is preserved with good working capability on 25 mm oil or water tempered sheet metal, annealed, and even after electric arc welding, without preheating or post-heating.
From a thickness of 8 mm on, oil or water tempering ensures consistent strength exceeding 1,000 MPa with good working capability.

MECHANICAL PROPERTIES DEPENDING ON
ANNEALING TEMPERATURE

Density: 7,8

Average dilatation coefficient in m/m °C:
*between 20°C and 200°C: 12,6X10(exponent-6)
*between 20°C and 400°C: 13,5X10(exponent-6)
*between 20°C and 600°C: 14,3X10(exponent-6)

Transformation points:
*Ac 1 = 765°C
*Ac 3 = 950°C

Thermal conductivity in W m/m2 °C
*at 20°C : 46

FORGING
1100 / 900°C

ANNEALING
CHeating to 875°C and slow cooling. In the softened state, approximate Brinell hardness 174.

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15 CDV 6 is compatible with standard AIR 9160 C
25 CD 4 S is replaced by 15 CDV 6 in standard AIR 9160 C
4130 is compatible with US standard MIL-S-18729 C and MIL-S-6758 A