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Alloy T41 / 20CrMoVTiB4-10 / 1.7729

Steel for Power Plant High Temperature Bolt applications

Alloy T41 / 20CrMoVTiB4-10 / 1.7729

In August 2012, Broder Metals Group Ltd became the exclusive stockholder and distributor for High Temperature Bolting Alloy T41 round bar material developed by PRD Fasteners Ltd. The material is extensively used for turbine and process plant fasteners and for boiler support rods in coal fired power plants around the world.

This blog is one of a series that provides details about the product, both for internal technical information for our sales staff, and as general information for any interested outsider.  A previous blog has discussed the history of the product.

A full document (including all information released as blogs) is available as a PDF, providing in depth the material’s chemical, mechanical and metallographic properties is available on request – please email mike.andrews@broder-metals-group.com for a free copy.

Material specification

PRD AT41 bar is produced in a German mill via the ingot cast route in accordance with PRD Data Sheet DH/28/1 revision 3 (3-09/2007) and process specifications PFC 7729 SDS rev 5+, PFC 7729 BGS rev 5+ and PFC 7729 GFM rev 1+. Ingot cast material tends to produce a finer grain structure, which in turn provides better creep properties than continuous cast (concast) material.

The material is heat treated in accordance with BSEN 10269:1999; 20CrMoVTiB4-10 with appropriate sub-critical annealing, hardening and tempering cycles according to the diameter of the material. Every bar is subject to spectroscope analysis, and every bar is Circograph and Ultrasonically tested to DIN EN 10308 03/12 CLASS 4.  The werkstoffe number is 1.7729.

Independent microstructural examination from one longitudinal section across the full cross-sectional width of the bar product is carried out and reported as standard for each cast of material.

Grain size testing to ASTM-E 112 with acceptance limits of size 5 or finer is also reported as standard for each cast.

PRD-AT41, and the fasteners manufactured out of it, was approved by EON in September 2007 for use on high temperature steam turbine plant. Full details of the testing process and acceptance results can be found in the EON Power Technology Report No PT/LH979/R.

The extensive proving trials and the maintained testing regimes via independent test houses, means that the material meets or exceeds the following industry standard specifications:

  • CEGB GDCD TD2 ISS2
  • CEGB 0259604/82 (T41)
  • GEC Turbine Generators Ltd Specification 30/227 ISS 10/83
  • BS 1506 681-820
  • BS 4882 B16A
  • Siemens AG Specification TLV 9185 01
  • BSEN 10269 1999 Material Number 1.7729
  • Durehete 1055
  • PFC 7729 SDS revision 5
  • PFC 7729 BGS revision 5
  • PFC 7729 GFM revision 1

Finally, in addition to meeting the standard requirements of material of this type, e.g. BE EN 10269: 1999 and 1999+A1:2006 (Steels and nickel alloys for fasteners with specified elevated and/or low temperature properties) the following information is supplied as standard on all Mill or Broder Metals Group’s own EN 10204 3.1 certificates (either / both supplied at the request of the customer):

  1. Values of Sb (Antimony) and R – normally the Sb value is not reported unless specifically requested, but without which the value of R cannot be independently checked.
  2. Grain size (which is ASTM 5 or finer)
  3. The results of the independent microstructural examination on each cast.

Material Application

The material is ideal for high room- and elevated-temperature fasteners, has good creep, notch and relaxation resistance up to 570o C, and is comparable to low alloy steel turbine casting materials in terms of its thermal expansion coefficients.

These properties make the material ideal for use for turbine and process plant fasteners and for boiler support rods and is increasingly being considered for all power generation plant, in addition to its’ traditional use in coal-fired power stations.

Testing Regime

100% of bars are hardness tested, and the hardest & softest bars are selected for full mechanical testing and must meet the following requirements in the longitudinal direction:

100% of bars are spectroscope analysed and results compared against the relevant standard.

100% of bars are Circograph tested and Ultrasonically tested to DIN EN 10308.03/02 Class 4.

All material is delivered fully identified and batch traceable, along with mill or Broder Metals Group EN 10204 3.1 certification at customer’s request. All certification shows manufacturing process number, chemical analysis, mechanical properties, non-destructive testing results, heat treatment, grain size and microstructural examination details.

Additional testing can be carried out to satisfy critical requirements at independent test houses as required.

Contact

To discuss the properties of PRD-AT41 or to seek supply opportunities, please contact Broder Metals Group on ++44 (0) 114 232 9241 or email: sales@broder-metals-group.com

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