Section
3 Castings for machinery construction
3.1 Scope
3.1.3 The manufacture
or repair of cast steel connecting rods is not permitted, except where
the manufacturing and quality control procedures have been approved
by LR. For approval purposes, tests are to be carried out at the place
of manufacture using the proposed process to demonstrate that the
castings are sound. Tests are to be carried out to confirm that the
appropriate mechanical properties are attained within the casting,
including areas where weld repairs have been performed. Any changes
to manufacturing, repair and quality control procedures are to be
submitted to LR for approval, see also
Ch 1, 2.2 LR Approval – General.
3.2 Chemical composition
3.2.1 The chemical composition of ladle samples for carbon and carbon-manganese
machinery steel castings is to comply with the limits given in Table 4.3.1 Chemical composition limits for
machinery steel castings (%): C, C-Mn steels, or where applicable, the requirements of the
approved specification.
Table 4.3.1 Chemical composition limits for
machinery steel castings (%): C, C-Mn steels
Steel type
|
Applications
|
C (max.)
|
Si (max.)
|
Mn
|
S (max.)
|
P (max.)
|
Residual elements (max.)
|
Total residuals (max.)
|
Cu
|
Cr
|
Ni
|
Mo
|
C, C-Mn
|
Castings for non-welded construction
|
0,40
|
0,60
|
0,50-1,60
|
0,035
|
0,035
|
0,30
|
0,30
|
0,40
|
0,15
|
0,80
|
Castings for welded construction
|
0,23
(See Note)
|
0,60
|
0,50-1,60
|
0,035
|
0,035
|
0,30
|
0,30
|
0,40
|
0,15
|
0,80
|
Note Castings which are intended for parts of a
welded fabrication are to be of weldable quality with a carbon content
generally not exceeding 0,23%. The carbon content may be increased
above this level provided that the carbon equivalent (Ceq) is not more
than 0,41%, calculated using the following formula:
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3.2.2 Proposals
to use steels with higher carbon content, or alloy steels, for welded
construction will be subject to special consideration.
3.2.3 For alloy machinery steel castings, the chemical composition of the ladle
samples is to comply with the limits provided in Table 4.3.2 Chemical composition limits for
machinery steel castings (%): Alloy steels, or where applicable, the
requirements of the approved specification.
Table 4.3.2 Chemical composition limits for
machinery steel castings (%): Alloy steels
Steel type
|
Applications
|
C (max.)
|
Si (max.)
|
Mn
|
S (max.)
|
P (max.)
|
Alloying elements (min.)
(See Note)
|
Cu
|
Cr
|
Ni
|
Mo
|
Alloy
|
Castings for non-welded construction
|
0,45
|
0,60
|
0,50-1,60
|
0,030
|
0,035
|
0,30
|
0,40
|
0,40
|
0,15
|
Castings for welded construction
|
Alloying element values
are to comply with recognised national/ international standards or
designer’s specifications and shall be agreed with LR.
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Note.
At least one of the elements shall comply with the minimum
content.
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3.3 Heat treatment
3.3.1 Castings are to be supplied in one of the following delivery
conditions:
- Carbon and carbon-manganese steels:
- Fully annealed
- Normalised
- Normalised and tempered
- Quenched and tempered.
-
Alloy steels:
- Normalised
- Normalised and tempered
- Quenched and tempered.
For all types of steel, the tempering temperature is to be not less
than 550°C.
3.3.2 The delivery condition shall meet the design and application requirements. It is the
manufacturer’s responsibility to select the appropriate heat treatment method for
obtaining the required mechanical properties.
3.3.3 Engine bedplate
castings, turbine castings and any other castings where dimensional
stability and freedom from internal stresses are important, are to
be given a stress relief heat treatment. This is to be at a temperature
not lower than 550°C, followed by furnace cooling to 300°C
or lower. Alternatively, full annealing may be used provided that
the castings are furnace cooled to 300°C or lower.
3.4 Mechanical tests
3.4.1 At least one tensile test specimen and one set of impact tests are to be
taken from material representing each casting or batch of castings.
3.4.2 Where the casting is of complex design, or where the finished mass exceeds
10 tonnes, two cast on test samples are to be provided from the heaviest section,
located as far as practicable from each other. Where large castings are made from two or
more casts which are not mixed in a ladle prior to pouring, two or more test samples are
required corresponding to the number of casts involved. The test samples are to be
integrally cast at locations as widely separated as possible.
3.4.3 Table 4.3.3 Mechanical properties for
machinery steel castings intended for welding and Table 4.3.4 Mechanical properties for
machinery steel castings not intended for welding gives the minimum requirements for yield stress,
elongation, reduction of area and impact test energy values corresponding to steel types
and different strength levels, but it is not intended that these should necessarily be
regarded as specific grades. Intermediate levels of minimum tensile strength may be
specified, in which case minimum values for yield stress, elongation and reduction of
area may be obtained by interpolation.
Table 4.3.3 Mechanical properties for
machinery steel castings intended for welding
Steel type
|
Specified minimum tensile strength
(N/mm2)
|
Yield stress (N/mm2) min.
|
Elongation on 5, 65 min.
|
Reduction of area (%) min.
|
Charpy V-notch impact test (See Note)
|
Test
temperature (°C)
|
Minimum average energy (J)
|
C, C-Mn
|
400-550
440-590
480-630
520-670
560-710
600-750
|
200
220
240
260
300
320
|
25
22
20
18
15
13
|
40
30
27
25
20
20
|
0
|
27
|
Alloy
|
550-700
|
355
|
18
|
30
|
600-750
|
400
|
16
|
30
|
650-800
|
450
|
14
|
30
|
700-850
|
540
|
12
|
28
|
Note. Special consideration may be given
to alternative requirements for Charpy V-notch impact test, depending on
design and application, and subject to agreement by LR.
|
Table 4.3.4 Mechanical properties for
machinery steel castings not intended for welding
Steel type
|
Specified minimum tensile strength
(N/mm2)
|
Yield stress (N/mm2) min.
|
Elongation on 5, 65 min.
|
Reduction of area (%) min.
|
Charpy V-notch impact test (See Note
1)
|
Test
temperature (°C)
|
Minimum
average energy (J)
|
C, C-Mn
|
400-550
440-590
480-630
520-670
560-710
600-750
|
200
220
240
260
300
320
|
25
22
20
18
15
13
|
40
30
27
25
20
20
|
AT
(See Note 2)
|
27
|
Alloy
|
550-700
|
340
|
16
|
35
|
600-750
|
400
|
16
|
35
|
650-800
|
450
|
14
|
32
|
700-850
|
540
|
12
|
28
|
Note 1. Special
consideration may be given to alternative requirements for Charpy
V-notch impact test, depending on design and application, and subject
to agreement by LR.
Note 2. AT refers to
Ambient Temperature (i.e. 23°C±5°C), which is specified in ISO
148-1.
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3.4.6 For alloy
steel castings and carbon-manganese steel castings containing more
than 0,40 per cent carbon, the results of all mechanical tests are
to comply with an approved specification.
3.4.7 When a casting, or a batch of castings, has failed to meet the mechanical
test requirements, it may be re-heat treated and re-submitted for acceptance tests but
this may not be carried out more than twice, see
Ch 2, 1.4 Re-testing procedures. The additional tests detailed in Ch 2, 1.4 Re-testing procedures are to be taken, preferably from the same test sample, but
alternatively from another test sample representative of the casting or batch of
castings.
3.5 Non-Destructive Examination
3.5.1 All piston crowns and cylinder heads are to be examined by ultrasonic
testing unless otherwise agreed with LR. Piston crowns intended for engines having a
bore size larger than 400 mm and cylinder heads intended for engines having a bore size
larger than 300 mm are additionally to be examined by magnetic particle or penetrant
testing in accordance with and Ch 4, 1.8 Volumetric Non-Destructive Examination.
3.5.4 Other castings
are to be examined by non-destructive methods where specified.
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