W8

W8(1978)(cont)(Rev.1
July 2002)(Rev.2
May 2004)(Rev.3
Mar 2022)(Rev.4
Mar 2024)

Hull and machinery steel castings
1

Scope

1.1 These requirements are applicable to C, C-Mn and alloy steel castings intended for hulland machinery applications for ships and offshore units for worldwide services as specified in
the relevant IACS Unified requirements and/or requirements of the Classification Society.
This Unified Requirement also makes consideration for grades that are intended for
fabrication by welding, as well as grades not intended for welding.
1.2 Additional requirements may be necessary, especially when the castings are intended
for service at low or elevated temperatures, e.g. for ships with ice-class or for boilers.
Additional requirements will typically be required for castings for offshore units depending on
applicable service temperature and environment.
1.3 Similarly, C and C-Mn steel castings and alloy steel castings which comply with nationalor proprietary specifications may be accepted provided such specifications give reasonableequivalence to these requirements or are otherwise specially approved or required by theClassification Society.
2

Manufacture

2.1

Castings are to be made at a manufacturer approved by the Classification Society.

2.2

The steel is to be manufactured by a process approved by the Classification Society.

2.3 All flame cutting, scarfing or arc-air gouging to remove surplus metal is to beundertaken in accordance with recognized good practice and is to be carried out before thefinal heat treatment. Preheating is to be employed when necessitated by the chemicalcomposition and/or thickness of the castings. If necessary, the affected areas are to be either
machined or ground smooth.
2.4 For certain components including steel castings subjected to surface hardening
process, the proposed method of manufacture may require special approval by theClassification Society.
2.5 Joining of two or more castings by welding to form a composite component:
Requirements for welding procedure qualification tests of steels for hull construction andmarine structures are specified in UR W28. Welders for hull structural steel castings are to bequalified in accordance with UR W32. Requirements for other WPS and qualification thereof,
for welder certification and for type approval of welding consumables are at the discretion of
the Class Societies.
2.6 Temporary welds made for operations such as lifting, handling, staging, etc., are to bein accordance with approved welding procedures and qualified welders, and are to be
removed, ground and inspected using suitable NDT methods.
________________________________________________________
Notes:
1.

Rev.3 of this UR is to be uniformly implemented by IACS Societies for ships and offshore
units contracted for construction on or after 1 July 2023.
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W8

2.

Rev.4 of this UR is to be uniformly implemented by IACS Societies for ships and offshore
units contracted for construction on or after 01 January 2025.

3.

The “contracted for construction” date means the date on which the contract to build thevessel is signed between the prospective owner and the shipbuilder. For further details
regarding the date of “contract for construction”, refer to IACS Procedural Requirement(PR) No. 29.

(cont)

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3

Quality of castings

3.1 All castings are to be free from surface or internal defects, which would be prejudicial totheir proper application in service. The surface finish is to be in accordance with goodpractice and any specific requirements of the approved plan.
4

Chemical composition

4.1 All castings are to be made from killed steel and the chemical composition is to beappropriate for the type of steel and the mechanical properties specified for the castings.
4.1 The chemical composition of each heat is to be determined by the manufacturer on asample taken preferably during the pouring of the heat. When multiple heats are tapped into acommon ladle, the ladle analysis shall apply.
4.2 The chemical composition is to comply with the overall limits given in Table 1 and Table
2, respectively, or, where applicable, the requirements of the approved specification.
Table 1 Chemical composition limits for hull andmachinery steel castings (%): C, C-Mn steels
Steel
type

C, C-Mn

Total
Residual elements
residuals(max.)(max.)Mo
Cu Cr Ni

Applications

SiC(max.) (max.)

Mn

SP(max.) (max.)

Castings for
non-welded
construction

0.40

0.60

0.501.60

0.035 0.035 0.30 0.30 0.40 0.15

0.80

Castings for
weldedconstruction

0.23

0.60

0.50- 0.035 0.035 0.30 0.30 0.40 0.15
1.60

0.80

Table 2 Chemical composition limits for hull and machinery steel castings (%): Alloy steels
Steel
type

Alloy

Applications

SiC(max.) (max.)

Mn

SP(max.) (max.)

Alloying elements1) (min.)
Ni
Mo
Cr
Cu

Castings for
non-welded
construction

0.45

0.501.60

0.030 0.035

0.30Castings for
weldedconstruction

0.60

0.40

0.40

0.15

alloying element values to be agreed with Class Society1) At least one of the elements shall comply with the minimum content.

4.3 Suitable grain refining elements such as aluminium may be used at the discretion of the
manufacturer or as agreed with the Class Society.
5Heat treatment (including straightening)

5.1

Castings are to be supplied in one of the following delivery conditions:(a) Carbon and carbon-manganese steels:- Fully annealed- Normalized

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- Normalized and tempered- Quenched and tempered.

W8(cont)(b) Alloy steels:- Normalized- Normalized and tempered- Quenched and tempered
For all types of steel the tempering temperature is to be not less than 550°C.
The delivery condition shall meet the design and application requirements. It is the
manufacturers responsibility to select the appropriate heat treatment method to obtain therequired mechanical properties.
5.2 Castings for components such as crankshafts and engine bedplates, where
dimensional stability and freedom from internal stresses are important, are to be given a
stress relief heat treatment. This is to be carried out at a temperature of not less than 550°C
followed by furnace cooling to 300°C or lower.
5.3 Heat treatment is to be carried out in properly constructed furnaces which are efficiently
maintained and have adequate means for control and recording of temperature. The furnace
dimensions are to be such as to allow the whole casting to be uniformly heated to thenecessary temperature. In the case of very large castings alternative methods for heat
treatment will be specially considered by the Classification Society.
Sufficient thermocouples are to be connected to the furnace charge to measure and recordthat its temperature is adequately uniform unless the temperature uniformity of the furnace isverified at regular intervals.
5.4 If a casting is locally reheated or any straightening operation is performed after the finalheat treatment, a subsequent stress relieving heat treatment may be required in order toavoid the possibility of harmful residual stresses. The manufacturer shall have strict control ofthis temperature in order to avoid any detrimental effects to the final heat treatment andresultant microstructure and mechanical properties of the casting.
5.5 The foundry is to maintain records of heat treatment identifying the furnace used,furnace charge, date, temperature and time at temperature. The records are to be presented
to the Surveyor on request.
6

Mechanical tests

6.1 Test material, sufficient for the required tests and for possible retest purposes is to beprovided for each casting or batch of castings.
6.2 At least one test block is to be provided for each casting or batch of castings. Unlessotherwise agreed these test blocks are to be either attached to the castings, cast integrally on
the castings or cast separately.integrally cast or gated to the castings.
6.3 (i) The preferred test block arrangement, where practical, is for the manufacturer toprovide at least one 30mm test block by either attached to the castings or cast integrally on
the castings.1
Note 1: The test results represent the material from which the castings have been poured andthe subsequent heat treatment process and may not necessarily represent the properties of thecastings. These properties can be affected by solidification conditions and the rate of cooling
during heat treatment, which are in turn influenced by casting thickness, size, complexity andPage 4 of 12

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shape. The purpose of the test block is to provide a qualitative check to demonstrate theeffective control of existing heat treatment processes and procedures.

6.3 (ii) For castings where it is required that the mechanical properties need to be
demonstrated for specific section thicknesses and when agreed upon between the
manufacturer and the purchaser, then proposals2 for alternative test block arrangements (interms of size and type) are to be submitted for approval by the Classification Society.
Note 2: The size of the test blocks for mechanical testing may be determined by the rulingsection of the casting that they are representative of the casting’s heat treatment andmicrostructure. Also see ISO 4885,2018; ISO683-1:2016 and ISO 683-2: 2016.
Alternatively, determination of test block size and type may be supported by historical andstatistical test data, production of a representative test block or a component, simulation
software, or a combination of all these items.

6.3
The size of the test blocks for mechanical testing is to be such that the heat treatment
and microstructure is representative for the section of the casting with the ruling section, i.e.
the section for which the specified mechanical properties apply, see also ISO 683-1:2018 andISO 683-2:2018, respectively.
For C, C-Mn steel castings this is in general to be achieved as follows:
The test block shall have a thickness (tS) of not less than the ruling section of the casting, or
30 mm, whichever is larger.
For large thickness castings other than stern tube, stern frame, anchor and rudder horn, tS
normally need not to exceed 150 mm. Length and width of the test block is normally to be atleast three times tS, unless otherwise agreed with the Class Society, as shown in Figure 1.
(Note that longer or wider test blocks may be necessary in order to accommodate therequired test specimens.)
For castings for stern tube, stern frame, anchor and rudder horn the test block thickness tSshall represent the ruling section.
Guidance:
Shorter width or length may be accepted for test blocks where actual casting width or length(tA) is in the range between tS and 3tS.
Example 1: For a general casting with dimensions 140 x 160 x 1250 mm the required test
block size would typically be 140 x 160 x 420 mm (that is: tS x tA x 3tS).
Example 2: For a stern tube casting with ruling section tS = 170 mm and width/height/lengthtA1/tA2/tA3 = 1000/600/1800 mm, the required test block size would typically be 170 x 510 x 510
mm (that is: tS x 3tS x 3tS) see Figure 2.
(end of guidance)

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Fig. 1: Specimen positions relative to the test block in accordance with ISO 4990:2015** The figure taken from ISO 4990:2015, Steel castings — General technical delivery requirements, is reproducedwith the permission of the International Organization for Standardization, ISO. This standard can be obtained fromany ISO member and from the website of the ISO Central Secretariat at the following address: www.iso.org.
Copyright remains with ISO.

Fig. 2: Example 2: test block gated to stern tube casting
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W8W8(cont)For alloy steel castings the manufacturer shall propose dimensions for the test block anddemonstrate the representative nature of it.
6.4 For test blocks with thickness ≤ 56 mm, the longitudinal axis of the test specimens is tobe located at ≥ 14 mm from the surface in the thickness direction. For test blocks withthickness > 56 mm, the longitudinal axis of the test specimens is to be located at ≥ ¼ tS fromthe surface. Test specimens shall be taken in such a way that no part of the gauge length ismachined from material closer than tS to any of the other surfaces. For impact testing, thisrequirement shall apply to the complete test specimen - refer to Figure 1 for location of test
specimens in relation to the test block.
6.45 Where the casting is of complex design or where the finished mass exceeds 10 tonnes,
two cast on test blocks are to be provided from the heaviest section, located as far aspracticable from each other.
6.56 Where large castings are made from two or more casts, which are not mixed in a ladleprior to pouring, two or more test blocks are to be provided corresponding to the number ofcasts involved. These are to be attached to the casting or cast integrally on the castings
integrally cast at locations as widely separated as possible.
6.67 For castings where the method of manufacture has been specially approved by theClassification Society in accordance with W8.2.4, the number and position of test blocks is tobe agreed with the Classification Society having regard to the method of manufacture
employed.
6.78 As an alternative to 6.2, where a number of small castings of about the same size, eachof which is under 1000kg in mass, are made from one cast and heat treated in the same
furnace charge, a batch testing procedure may be adopted using separately cast test blocksof suitable dimensions. At least one test block is to be provided for each batch of castings.
6.89 The test blocks are not to be detached from the casting until the specified heat
treatment has been completed and they have been properly identified.
6.910 One tensile test specimen and one set of impact tests are to be taken from each test
block.
6.1011 The preparation of test specimens and the procedures used for mechanical testing
are to comply with the relevant requirements of UR W2. Unless otherwise agreed all tests areto be carried out in the presence of the Surveyors.
7

Mechanical properties

7.1 Table 3 and Table 4 give the minimum requirements for yield stress, elongation,
reduction of area and impact test energy values corresponding to steel types and different
strength levels. Where it is proposed to use a steel with a specified minimum tensile strengthintermediate to those given, corresponding minimum values for the other properties may beobtained by interpolation.
7.2 Castings may be supplied to any specified minimum tensile strength selected within thegeneral limits detailed in Table 3 and Table 4, respectively, but subject to any additional
requirements of the relevant construction Rules.

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7.3 The mechanical properties are to comply with the requirements3 of Table 3 and Table 4,
respectively, appropriate to the specified minimum tensile strength or, where applicable, therequirements of the approved specification.
Note 3: See also sections 6.3.

7.4

Re-test requirements for tensile tests are to be in accordance with UR W2.

7.5 The additional tests detailed in 7.4 are to be taken, preferably from the same, butalternatively from another, test block representative of the casting or batch of castings.
7.6 At the option of the manufacturer, when a casting or batch of castings has failed tomeet the test requirements, it may be reheat treated and re-submitted for acceptance tests.
Table 3 Mechanical properties for steel castings intended for welding

Steel
type

C, C-Mn

Alloy

Specifiedminimumtensilestrength1)(N/mm2 )
400
440
480
520
560
600
550
600
650
700

Charpy V-notch impact
Yield stress Elongation Reduction
Testof area
on 5,65 √So(N/mm2)temperature(%) min.
(%) min.
min.
(°C)
200
220
240
260
300
320
355
400
450
540

25
22
20
18
15
13
18
16
14
12

40
30
27
25
20
20
30
30
30
28

Minimum
averageenergy (J)

0

27

0

27

NOTE
1)
A tensile strength range of 150 N/mm2 may additionally be specified.
2)
Special consideration may be given to alternative requirements for Charpy V-notch
impact test, depending on design and application, and subject to agreement by Society.

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Table 4. Mechanical properties for machinery steel castings not intended for welding

W8(cont)

Charpy V-notch impact

Steel
type

Specifiedminimumtensilestrength1)(N/mm2 )C, C-Mn

400
440
480
520
560
600

200
220
240
260
300
320

25
22
20
18
15
13

40
30
27
25
20
20

550

340

16

35

600

400

16

35

650

450

14

32

700

540

12

28

Alloy

test2)
Yield stress Elongation Reductionof area (%)
Test
Minimum(N/mm2) on 5,65 √So
min.
temperature
average(%) min.
min.
(°C)
energy (J)

AT3)

27

AT3)

27

NOTE
A tensile strength range of 150 N/mm2 may additionally be specified.
2)
Special consideration may be given to alternative requirements for Charpy V-notch impact
test, depending on design and application, and subject to agreement by Society.
3)
AT refers to Ambient Temperature (i.e. 23°C±5°C), which is specified in ISO 148-1:2016
1)

8

Inspection

8.1 All castings are to be cleaned and adequately prepared for examination; suitable
methods include pickling, caustic cleaning, wire brushing, local grinding, shot or sandblasting. The surfaces are not to be hammered, peened or treated in any way which may
obscure defects.
8.2 Before acceptance all castings are to be presented to the Surveyors for visual
examination. Where applicable, this is to include the examination of internal surfaces. Unlessotherwise agreed, the verification of dimensions is the responsibility of the manufacturer.
8.3 When required by the relevant construction Rules, or by the approved procedure forwelded composite components (see W8.2.6.), appropriate non-destructive testing is also to
be carried out before acceptance and the results are to be reported by the manufacturer. The
extent of testing and acceptance criteria are to be agreed with the Classification Society.
IACS Recommendation No. 69 is regarded as an example of an acceptable standard
specifying suitable minimum requirements.
8.4 When required by the relevant construction Rules castings are to be pressure tested
before final acceptance. These tests are to be carried out in the presence of the Surveyor andare to be to their satisfaction.
8.5 In the event of any casting proving to be defective during subsequent machining or
testing it is to be rejected notwithstanding any previous certification.
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9

Rectification of defective castings

9.1

General(i)

Where castings are to be repaired, the manufacturer shall exercise robust controls of all
repair operations regarding the repair of castings, with respect to dimensions, heat
treatment, inspection and quality control.

(ii) The approval of the Classification Society is to be obtained where steel castings fromwhich defects were removed are to be used with or without weld repair.
(iii) Defects and unacceptable indications must be repaired as indicated below:
Defective parts of material may be removed by grinding, or by chipping and grinding, orby arc air-gouging and grinding. Thermal methods of metal removal shall only beallowed before the final heat treatment. All grooves shall have a bottom radius ofapproximately three times the groove depth and should be smoothly blended to thesurface area with a finish equal to that of the adjacent surface.
(iv) For NDT of steel castings after repair, see 8.3.
(v) Where the defective area is to be repaired by welding, the excavations are to besuitably shaped to allow good access for welding. The resulting grooves are to be
subsequently ground smooth and complete elimination of the defective material is to beverified by MT or PT.
(vi) Shallow grooves or depressions resulting from the removal of defects may be accepted
provided that they will cause no appreciable reduction in the strength of the casting or
affect the intended use, and the depth of defect removal is not over 15mm or 10% ofwall thickness, whichever is less. The resulting grooves or depressions are to be
subsequently ground smooth and complete elimination of the defective material is to beverified by MT or PT. Small surface irregularities sealed by welding are to be treated as
weld repairs, see 9.2.
9.2

Weld Repairs

In addition to the requirements given in 9.1, the following apply for weld repairs:(i)

For C and C-Mn steel castings weld repairs shall be suitably classified as major orminor. For alloy steel castings, repair requires approval from the Classification Society.
a.

Major repairs are those where:- the depth is greater than 25% of the wall thickness or 25mm whichever is less, or- the total weld area on a casting exceeds 0.125m^2 of the casting surface notingthat where a distance between two welds is less than their average width, they
are to be considered as one weld.

b.

Minor weld repairs: Weld repairs not classified as major are considered as minor
and need to be carried out in accordance with a qualified welding procedure.

(ii) The following is required for major repairs:a.

Shall be carried out before the final delivery heat treatment conditionb.

Shall comply with the requirements in (iv) below

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W8

c.

(cont)

Before welding is started, full details of the extent and location of the repair, theproposed welding procedure, heat treatment and subsequent inspection
procedures are to be submitted for approval.

(iii) The following is required for minor repairs:a.

Shall be carried out before the final delivery heat treatment conditionb.

Shall comply with the requirements in (iv) below (also with respect to records, see(iv) f) and g).

c.

With the exception of alloy steels, do not require prior approval by the Classification
Society, except as given in (d)d.

The Classification Society may request minor repairs in critical areas to be treatedas major repairs.

(iv) The following requirements apply for all weld repairs (major and minor):a.

All castings in alloy steels and all castings for crankshafts are to be suitably preheated prior to welding. Castings in carbon or carbon-manganese steel may also
require to be pre-heated depending on their chemical composition and thedimensions and position of the weld repairs.

b.

Welding procedures are to be qualified and shall match the delivery condition of thecasting. Qualification of welding procedures shall follow the Classification Societyrules, or subject to agreement with the Classification Society, a recognised
standard (e.g. IACS UR W28 or ISO 11970:2016.

c.

Welding is to be done under cover in positions free from draughts and adverse
weather conditions by qualified welders with adequate supervision. As far as
possible, all welding is to be carried out in the downhand (flat) position.

d.

The welding consumables used are to be of an appropriate composition, giving aweld deposit with mechanical properties similar and in no way inferior to those of
the parent castings. Welding procedure tests are to be carried out by the
manufacturer to demonstrate that satisfactory mechanical properties can beobtained after heat treatment as detailed in 5.1.

e.

After welding has been completed the castings are to be given either a suitable
heat treatment in accordance with the requirements of 5.1 or a stress relieving heat
treatment at a temperature of not less than 550°C for C and C-Mn steel castings.
For alloy steel castings, the heat treatment has to be agreed with the Class
Society. The type of heat treatment employed will be dependent on the chemicalcomposition of the casting and the dimensions, positions and nature of the repairs,
and should not affect the properties of the casting.
Subject to the prior agreement of Classification Society, special consideration may
be given to the omission of post weld heat treatment or to the acceptance of local
stress-relieving heat treatment where the repaired area is small and machining of
the casting has reached an advanced stage.

f.

On completion of heat treatment the weld repairs and adjacent material are to be
ground smooth and examined by magnetic particle or liquid penetrant testing.
Supplementary examination by ultrasonics or radiography ultrasonic orPage 11 of 12

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radiographic testing may also be required depending on the dimensions and natureof the original defect. Satisfactory results are to be obtained from all forms of nondestructive testing used.

W8(cont)
g.

The manufacturer is to maintain full records detailing the extent and location of
repairs made to each casting and details of weld procedures and heat treatments
applied for repairs. These records are to be available to the Surveyor and copies
provided on request.

9.3 Recommendation for welding: For steels with C ≥ 0.23 or Ceq ≥ 0.45, the WPQT on
which the WPS is based, should be qualified on a base material having a Ceq as follows: theCeq of the base material should not fall below more than 0.02 of the material to be welded.
(Example: WPQT for a material with actual Ceq = 0.50 may be qualified on a material with
Ceq ≥ 0.48.)
10

Identification of castings

10.1 The manufacturer is to adopt a system of identification which will enable all finishedcastings to be traced to the original cast and the Surveyors are to be given full facilities for so
tracing the castings when required.
10.2 Before acceptance, all castings which have been tested and inspected with satisfactory
results are to be clearly marked by the manufacturer. At the discretion of individual
Classification Societies any of the following particulars may be required:(i) Steel quality.
(ii) Identification number, cast number or other marking which will enable the full history of
the casting to be traced.
(iii) Manufacturer's name or trade mark.
(iv) The Classification Society's name, initials or symbol.
(v) Abbreviated name of the Classification Society's local office.
(vi) Personal stamp of Surveyors responsible for inspection.
(vii) Where applicable, test pressure.
10.3 Where small castings are manufactured in large numbers, modified arrangements for
identification may be specially agreed with the Classification Society.
11

Certification

11.1 The manufacturer is to provide the required type of inspection certificate giving thefollowing particulars for each casting or batch of castings which has been accepted:(i) Purchaser's name and order number.
(ii) Description of castings and steel quality.
(iii) Identification number.
(iv) Steel making process, cast number and chemical analysis of ladle samples.
(v) Results of mechanical tests.
(vi) Results of non-destructive tests, where applicable.
(vii) Details of heat treatment, including temperatures and holding times.
(viii) Where applicable, test pressure.
End ofDocument

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