TCM 1 806-Johann Maier & Co. – Stuttgart (DE) EN 4634-060013

2 Replies to “TCM 1 806-Johann Maier & Co. – Stuttgart (DE) EN 4634-060013”

1. In QTP/QTR for qualification 806:

   • Tensile tests on screws:

   QTP, Clause 3.4.1.
   Allowance coefficient k = 0,45 was applied by JM for minimum tensile load requirement.
   This k=0,45 is for reduced countersunk head bolt with drive recess.
   EN4634 is not a screw with reduced head in my opinion, but this is a normal countersunk head screw with a drive recess in the head.
   For instance, following standards define countersunk screw, reduced head, with drive recess: EN4499, EN3304. In the title of these standards, it is written: “Screws, 100° countersunk reduced head (…)”.
   In EN4634, “reduced” is not mentioned in the title.
   EN4499 and EN3304 screw head height for MJ6 = 1,43 mm MAX.
   EN4634 screw head height for MJ6 = 2,6 mm (reference).
   So, from my point of view, k=0,45 is not applicable for EN4634, instead, as per prEN2576, Annex B, we have k=0,8 for normal countersunk head bolt, which might be more suitable for EN4634.
   Perhaps, it is unfortunate that prEN2576 does not specify any allowance coefficient for normal countersunk head bolt with drive recess. Maybe, this is not necessary (because of “normal” head height).
   In QTR, actual tensile values are significantly higher than 8,81 kN, which is minimum tensile load calculated with k=0,45: actual values are around 23 – 24 kN at break! See QTR clause 4.4.1 and test report 4.4.1A..
   If we consider k=0,8, then: minimum tensile load = 19,578×0,8=15,66 kN.

   • Stress rupture test on screws:

   Stress rupture Load = AR?R as per prEN2576, clause B.2.2.2, with ?R=760 MPa and AR= (pi/4)(d3)².
   There is a mistake in prEN2576, clause B.2.2.2: ?R=760 MPa in clause B.2.2.2 is not applicable for A286 bolts, 900 MPa strength class.
   For me, the right stress rupture strength is 480 MPa instead of 760 MPa.
   If we do the math:
   For MJ6x1: AR= (pi/4)(d3)²=(pi/4)(4,845)²=18,44 mm².
   Load = AR?R= 18,44×480=8851 N.
   Allowance coefficient k = 0,45 was applied for minimum stress rupture (@650°C) load in QTP and QTR.
   In QTP/QTR, minimum stress rupture Load = 8,85 * k = 8,85 * 0,45 = 3,98 kN.
   So, k=0,45 may not be applicable for EN4634 for the same reason given for tensile test.
   Instead, as per prEN2576, Annex B, we have k=0,8 for normal countersunk head bolt, which might be more suitable for EN4634.
   If we consider k=0,8, then: minimum stress rupture load = 8,851×0,8=7,08 kN.

   Last thing, in prEN2576:2015, clause B.2.2.1, Ultimate Tensile Strength mentioned is: Rm = 1210 MPa for ambient temperature test, which is wrong because prEN2576:2015 deals with A286 bolts with 900 MPa strength class.
   Fortunately, tensile load value in prEN2576, table 7 are in line with 900 MPa UTS:
   I hope these topics are clear enough!…

   If they are, could you please provide your advice, help me in solving this “issue”?

   Many thanks in advance,

   NOTE: if needed, see details on email entitled “RE: Qualification 806 –EN4634-060013 – JOHAN MAIER- EN4634 product standard – prEN 2576:2015 tech. Spec._Tensile and stress”, dated, February, Monday 17th 2020.

   Reply

2. QTR_EN4634_060013 para 4.4.2 was up-dated. New QTR revision is rev. c, issued 9.4.2020.

   The „Stress Rupture Test“ as required in the Technical Specification PrEN2576, Table 1 para 5.4.2 was repeated due to misinterpretation of the “K-Factor” for “Countersunk head bolt with drive recess in head”.The former “Stress Rupture Test” was performed with a “K-Factor of 0,45” which related to a tensile strength value of 3,98KN.

   New tests were successful performed with the correct “K-Factor of 0,8” which related to a tensile strength value of 7,08 KN. (see Laboratory Test Report from “WTL Werkstofftechnik-Labor GmbH”; GWT-ZP-2020-0968- issued 30-March2020, in QTR para 4.4.2 Annex QTR Doku4. rev.c.)

   It is clear for me now.
   Many thanks for performing a new stress rupture test with allowance coefficient “k” = 0,8.
   Qualification approved on my side.
   Best regards.
   Julien

   Reply