Section 6 Steel Forgings

601. Steel forgings

1. Application

(1) The requirements in 601. are to apply to the steel forgings(except those specified in 602., 603. and 604.) intended to be used for the components of hull construction, equipments, and machi- nery specified in each Part, and where relevant, these requirements are also applicable to materi- al for forging stock and to rolled bars intended to be machined into components of simple shape (hereinafter referred to as the "steel forgings").

(2) Steel forgings having characteristics differing from those specified in 601. are to comply with the requirements in 101. 2.

2. Kinds The steel forgings are classified as specified in Table 2.1.83 and 2.1.84.

3. Manufacturing process

(1) Steel forgings are to be manufactured from the killed steel.

(2) Adequate discards are to be made from the top and bottom of each ingot to ensure freedom

from piping and harmful segregation in the finished forgings.

(3) Steel forgings are to be hot worked by press or hammer from ingots, blooms forged or rolled

from ingots or blooms made from ingots by a combination of rolling and forging.

(4) Steel forgings are to be gradually and uniformly hot worked and are to be brought as nearly as

possible to the finished shape and size. Where practicable, they are to be worked so as to

cause metal flow in the most favourable direction having regard to the mode of stressing in service.

(5) The reduction ratio is to comply with the following;

(a) For components where the fibre deformation is mainly longitudinal; the total reduction ratio is to be not less than those shown in Table 2.1.80. See Guidance

Table 2.1.80 Reduction Ratio

(b) Disc type forgings such as gear wheels are made by upsetting

(i) The thickness of any part of the disc is to be not more than one half of the length of the billet from which it was formed provided that this billet has received an initial forging reduction of not less than 1.5:1.

(ii) Where the piece used has been cut directly from an ingot or where the billet has re- ceived an initial reduction of less than 1.5:1, the thickness of any part of the disc is to be not more than one third of the length of the original piece.

(6) The shaping of forgings or rolled slabs and billets by flame cutting, scarfing or arc-air gouging is to be undertaken in accordance with recognized good practice and, unless otherwise approved, is to be carried out before the final heat treatment. Preheating is to be employed when neces- sitated by the composition and thickness of the steel. For certain components, subsequent ma- chining of all flame cut surfaces may be required. See Guidance

(7) When

posed

two or more forgings are joined by welding to form a composite component, the pro- welding procedure specification is to be submitted for approval to the Society. Welding

procedure qualification tests may be required.

4. Heat treatment

(1) Except as provided in (5), after completion of all hot working operations, forgings are to be supplied in one of the conditions given in Table 2.1.81. to refine the grain structure and to obtain the required mechanical properties. No annealed forging is to be removed from the fur- nace until the temperature of the entire furnace charge has fallen to or below a temperature of 455°C. The tempering temperature is to be not less than 550 . See Guidance

Table 2.1.81 Heat Treatment

(2) Alternatively, alloy steel forgings may be supplied in the normalized and tempered condition, in which case the specified mechanical properties are to be agreed with the Society.

(3) Steel forgings which are subjected to any hot work after heat treatment, are to be heat treated

again.

(4) If a forging is locally reheated or any straightening operation is performed after the final heat

treatment, consideration is to be given to a subsequent stress relieving heat treatment.

(5) Where induction hardening or nitriding is to be carried out, forgings are to be heat treated at an appropriate stage to a condition suitable for this subsequent surface hardening.

(6) Where carburizing is to be carried out, forgings are to be heat treated at an appropriate stage

(generally either by full annealing or by normalizing and tempering) to a condition suitable for subsequent machining and carburizing.

(7) Where it is intended to surface harden forgings, full details of the proposed procedure and spec- ification are to be submitted for the approval of the Society. For the purposes of this approval, the manufacture may be required to demonstrate by test that the proposed procedure gives a

uniform surface layer of the required hardness and depth and that it does not impair the sound- ness and properties of the steel. See Guidance

(8) Heat treatment is to be carried out in properly constructed furnaces which are efficiently main-

tained and have adequate means for control and recording of temperature. The furnace di- mensions are to be such as to allow the whole furnace charge to be uniformly heated to the necessary temperature. In the case of very large forgings alternative methods of heat treatment

will be specially considered by the Society.

Sufficient thermocouples are to be connected to the furnace charge to measure and record that its temperature is adequately uniform unless the temperature uniformity of the furnace is verified

at regular intervals.

(9) The forge 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.

5. Chemical composition

(1) The chemical composition of steel forgings is to comply with the requirements given in Table 2.1.82.

(2) The chemical composition of each heat is to be determined by the manufacturer on a sample

taken preferably during the pouring of the heat. When multi heats are tapped into a common ladle, the ladle analysis shall apply.

(3) At the option of the manufacturer, suitable grain refining elements such as aluminium, niobium

or vanadium may be added.

analysis.

The content of such elements is to be reported in the ladle

Table 2.1.82 Chemical Composition

6. Mechanical properties

(1) The mechanical properties of

2.1.83. and 2.1.84.

steel forgings are to comply with the requirements given in Table

(2) At the discretion of this Societies hardness tests may be required on the following: The results

of hardness tests are to be reported and, for information purposes, typical Brinell hardness val- ues are given in Table 2.1.84.

(i) Gear forgings after completion of heat treatment and prior to machining the gear teeth. The

hardness is to be determined at four positions equally spaced around the circumference of the surface where teeth will subsequently be cut. Where the finished diameter of the toothed portion exceeds 2.5 m, the above number of test positions is to be increased to eight. Where the width of a gear wheel rim forging exceeds 1.25 m, the hardness is to be determined at eight positions at each end of the forging.

(ii) Small crankshaft and gear forgings which have been batch tested.

In such cases at least one hardness test is to be carried out on each forging.

(3) Hardness tests may also be required on forgings which have been induction hardened, nitrided or carburized. For gear forgings these tests are to be carried out on the teeth after, where appli-

cable, they have been ground to the finished profile. The results of such tests are to comply with the approved specifications.

7. Selection of test specimens

(1) Except as provided in (10) and (11), the test specimens for steel forgings are, after final heat treatment, to be taken lengthwise from prolongations or through bolt holes having a sectional area not less than that of the body of forging. Where batch testing is permitted according to (10), the test material may alternatively be a production part or separately forged. Separately forged test material is to have a reduction ratio similar to that used for the forgings represented.

(2) "One set of test specimens" is to consist of one tensile test specimen and when required, three charpy- V notch impact test specimen.

Table 2.1.83 Kinds and Mechanical Properties for Hull Steel Forgings

Table 2.1.84 Kinds and mechanical properties for machinery steel forgings

(3) Test specimens are normally to be cut with their axes either mainly parallel (longitudinal test) or mainly tangential (tangential test) to the principal axial direction of each product.

(4) Unless otherwise agreed, the longitudinal axis of test specimens is to be positioned as follows.

However the axis of transverse specimens may be located close to the surface of the forgings

(a) for thickness or diameter up to maximum 50 mm, the axis of test specimens is to be at the mid-thickness or the center of the cross section.

(b) for thickness or diameter greater than 50 mm, the axis is to be at one quarter thickness (mid-radius) or 80 mm, whichever is less, below any heat treated surface.

(5) Except as provided in (10), the number and direction of tests is to be as given in (a) through

(h) of the following requirements:

(a) Hull components such as rudder stocks, pintles etc. General machinery components such as

shafting, connecting rods, etc. : One set of tests is to be taken from the end of each forg- ing in a longitudinal direction except that, at the discretion of the manufacture, the alter- native directions or positions as shown in Fig 2.1.17., Fig 2.1.18. and Fig 2.1.19 may be

used. Where a forging exceeds both 4 tonnes in mass

and 3 m in length, one set of tests is

to be taken from each

end.

Fig 2.1.17 Plain shaft

Fig 2.1.18 Flanged shaft

Fig 2.1.19 Flanged shaft with collar

(b) Pinions : Where the finished machined diameter of the toothed portion exceeds 200 mm one set of tests is to be taken from each forging in a tangential direction adjacent to the tooth- ed portion (test position B in Fig 2.1.20) Where the dimensions preclude the preparation of tests from this position, tests in a tangential direction are to be taken from the end of the journal (test position C in Fig 2.1.20). If however, the journal diameter is 200 mm or less the tests are to be taken in a longitudinal direction (test position A in Fig 2.1.20). Where the finished length of the toothed portion exceed 1.25 m, one set of tests is to be taken from each end.

Fig 2.1.20 Pinion

(c) Small pinions : Where the finished diameter of the toothed portion is 200 mm or less one set of tests is to be taken in a longitudinal direction (test position A in Fig 2.1.20).

(d)

Gear wheels : One set of tests is to be taken from each forging in a tangential direction

(test position A or B in Fig 2.1.21).

Fig 2.1.21 Gear wheel

(e) Rims intended for reduction gears and for cam shaft driving gears of diesel engine (see Pt 5, Ch 2 201.1) are to comply with the following requirements.

(i) Where the finished diameter exceeds 2.5 m or the mass (as heat treated excluding test material) exceeds 3 tonnes, two sets of tests are to be taken from diametrically opposite positions (test positions A and B in Fig 2.1.22). The mechanical properties for longi-

tudinal test are to be applied.

Fig 2.1.22 Gear rim (made by expanding)

(ii) Where the weight and finished diameter are different from those given in (a), one set of test specimens may be taken from one end of the rim.

(f) Pinion sleeves : One set of tests is to be taken from each forging in a tangential direction

(test position A or B in Fig 2.1.23). Where the finished length exceeds 1.25 m one set of tests is to be taken from each end.

Fig 2.1.23 Pinion sleeve

(g) Crankwebs : One set of tests is to be taken from each forging in a tangential direction.

(h) Solid open die forged crankshafts : One set of tests is to be taken in a longitudinal direc- tion from the driving shaft end of each forging (test position A in Fig 2.1.24). Where the mass (as heat treated but excluding test material) exceeds 3 tonnes tests in a longitudinal direction are to be taken from each end (test positions A and B in Fig 2.1.24). Where, however, the crankthrows are formed by machining or flame cutting, the second set of tests is to be taken in a tangential direction from material removed from the crankthrow at the end opposite the driving shaft end (test position C in Fig 2.1.24).

Fig 2.1.24 Solid forged crankshaft

(6) For closed die crankshaft forgings and crankshaft forgings where the method of manufacture has been approved by the Society, the number and position of test specimens is to be agreed with the Society having regard to the method of manufacture employed.

(7) When a forging is subsequently divided into a number of components, all of which are heat treated together in the same furnace charge, for test purposes this may be regarded as one forg- ing and the number of tests required is to be related to the total length and mass of the origi- nal multiple forging.

(8) The test specimens are not to be separated from the body before the final heat treatment has

been completed. In the case of stamp forging or other case of forging requiring the surface hardening process, the test specimens may be prepared at a proper stage before the final heat treatment providing that such is approved by the Surveyor.

(9) When forgings are to be carburized, sufficient test material is to be provided for both prelimi- nary tests at the forge and for final tests after completion of carburizing. For this purpose du-

plicate sets of test material are to be taken from positions as detailed in (5) except that irre-

spective of the dimensions or mass of the forging, and, in the case of forgings with integral journals,

tests are required are to be cut in

from one position only a longitudinal direction.

This test material is to be machined to a diameter of D/4 or 60 mm, whichever is less, D is the finished diameter of the toothed portion. For preliminary tests at the forge one test material is to be given a blank carburizing and heat treatment cycle simulating that

where set of which

subsequently will be applied to the forging. For final acceptance tests, the second set of test material is to be blank carburized and heat treated along with the forgings which they represent.

At the discretion of the forgemaster or gear manufacture test samples of larger cross section may be either carburized or blank carburized, but these are to be machined to the required di- ameter prior to the final quenching and tempering heat treatment. Alternative procedures for test- ing of forgings which are to be carburized may be specially agreed with the Society.

(10) Normalized forgings with mass up to 1000 kg each and quenched and tempered forgings with mass up to 500 kg each may be batch tested. A batch is to consist of forgings of similar shape

and dimensions, made from the same heat of steel, heat treated in the same furnace charge and with a total mass not exceeding 6 tonnes for normalized forgings and 3 tonnes for quenched and tempered forgings, respectively.

(11) A batch testing procedure may also be used for hot rolled bars. A batch is to consist of ei- ther:

(i) material from the same rolled ingot or bloom provided that where this is cut into individual lengths, these are all heat treated in the same furnace charge, or

(ii) bars of the same diameter and heat, heat treated in the same furnace charge and with a to-

tal mass not exceeding 2.5 tonnes.

8. Surface inspection See Guidance

(1) When heat treatment and final machining are completed and, if necessary, at a proper time dur- ing machining, surface inspection is to be carried out. Where applicable, this is to include the examination of internal surfaces and bores. Testing methods and acceptance criteria are to be in accordance with the Guidance relating to the Rules specified by the Society.

(2) Dimension inspection of the steel forgings is to be conducted under the responsibility of the manufacturer, unless otherwise specified.

9. Quality

(1) Steel forgings are to be free from surface or internal defects which would be prejudicial to their proper application in service.

(2) When required by the conditions of approval for surface hardened forgings referred in 4 (7), ad-

ditional test samples are to be processed at the same time as the forgings which they represent. These test samples are subsequently to be sectioned in order to determine the hardness, shape

and depth of the locally hardened zone and which are to comply with the requirements of the approved specification.

(3) In the event of any forging proving defective during subsequent machining or testing, it is to

be rejected notwithstanding any previous certification.

10. Non-destructive inspection

(1) The following steel forgings are to be subjected to ultrasonic test at an appropriate stage of the manufacturing process and the test reports are to be showed or submitted to the Surveyor. Testing methods and acceptance criteria are to be in accordance with the Guidance relating to the Rules specified by the Society. See Guidance

(a) Rudder stock and pintle.

(b) Steel forgings given in Pt 5, Ch 2, 201.1.

(c) Thrust shafts, intermediate shafts and propeller shafts.

(d) Reduction gears and reduction gear shafts.

(e) Turbine rotors, turbine discs and turbine blades.

(2) The important parts of the following steel forgings are to be subjected to magnetic particle or liquid penetrant test at an appropriate stage of the manufacturing process. Testing methods and

acceptance criteria are to be in accordance with the Guidance relating to the Rules specified by

the Society. See Guidance

(a)

(b)

(c)

(d)

Steel forgings given in Pt 5, Ch 2, 201.1.

Propeller shafts. Reduction gears.

Turbine rotors, turbine discs and turbine blades.

(3) The Society may require sulphur print test for the portion of gear teeth.

(4) In place of the test methods given above, the Society may non-destructive inspections considered adequate by the Society.

(5) The Society may require non-destructive inspection or the steel and (2) when such is deemed necessary by the Society. See

accept the application of other

See Guidance

other than those specified in (1)

Guidance

(6) The welded parts of steel forgings used for welded construction are to be subjected to the non-destructive inspections considered adequate by the Society. See Guidance

11. Repair of defects

(1) Defects may be removed by grinding or chipping and grinding provided the component di- mensions are acceptable.

(2) After removing the defects, adequate non-destructive inspections are to be carried out to ensure that all defects have been completely removed.

(3) The resulting grooves are to have a bottom radius of approximately three times the groove

depth and are to be blended into the surrounding surface so as to avoid any sharp contours. Where the forgings from which defects where removed are used in that condition, the forgings are to be approved by the Surveyor.

(4) Repair welding of forgings except crankshaft forgings may be permitted subject to prior appro-

val of the Society. In such cases, full details of the extent and location of the repair, posed welding procedure, heat treatment and subsequent inspection procedures are to mitted for the approval. See Guidance

(5) The manufacturer is to maintain full records detailing the extent and location of repairs

the pro-

be sub-

made to

each forging and details of weld procedures and heat treatments applied for repairs. These re- cords are to be available to the Surveyor and copies provided on request.

12. Retest procedures

(1) Where the tensile test or hardness test fails to meet the requirements, additional test may be carried out in accordance with the requirements of 109.

(2) Regarding the impact tests, additional tests are to be carried out according to the requirements given in 301. 10 (3).

(3) The additional tests are to be taken, preferably from material adjacent to the original tests, but alternatively from another test position or sample representative of the forging or batch of

forgings.

(4) At the option of the manufacturer, when a forging or a batch of forgings has failed to meet the test requirements, it may be reheat treated and re-submitted for acceptance tests.

13. Marking

(1) Steel forgings which have satisfactorily complied with the required tests are to be marked with the identification mark in accordance with the requirements in 110.

(2) For steel forgings to which the requirements given in note 1. of the Table 2.1.83 and Table

2.1.84 applied, the material symbols are specified as R SF - (or R SF - A ) and the specified ten- sile strength is to be filled in symbol " - ". (e.g. For Hull and General purpose steel forging

which the specified tensile strength is 420 N m m : R SF 420H)

(3) Where carbon steel forgings are intended for welded construction specified in Note (1) of Table

2.1.82, "W" is to be suffixed to the marking. (e.g. RSF 440H-W, RSF 440M-W)

(4) The grade of Steel bars is to be indicated by suffixing a letter "B" to the symbol "R SF ". (e.g.

For Machinery steel forging which the specified tensile strength is 440 N mm : R SF B 440M)

14. Additional requirements for crank shafts

(1) Where solid crank shafts of 250 mm and over in finished diameter are manufactured by free forging, the heat treatment is normally to be carried out after crank parts are machined as near- ly as possible to the finished shape. See Guidance

(2) Where solid crank shafts, semibuilt-up crank throws and full built up crank arms are manufac- tured by special manufacturing processes, the preliminary tests instructed by the Society are to be carried out, in connection with the manufacturing processes and the selection of test specimens. See Guidance

(3) Where special manufacturing processes are adopted to reduce the size of crank shaft (refer to the requirements in Pt 5, Ch, 208. the preliminary tests instructed by the Society are to be carried out.

15. Additional requirements for turbine rotors

(1) The test specimens for turbine rotors are to be taken in accordance with the following require- ments:

(a) Where the turbine rotor is greater than 3 tons in weight, one set of longitudinal test speci- mens is to be taken from each end of the shaft portion and one set of transverse test speci- mens from the body portion respectively. (See Fig 2.1.25)

(b) Where the turbine rotor is not exceeding 3 tons in weight, one set of longitudinal test specimens is to be taken from one end of the shaft portion and one set of transverse test

specimens from the body portion respectively.

(2) For each turbine disc, one set of transverse test specimens is to be taken from the boss portion. (See Fig 2.1.26)

Fig 2.1.25 Selection of test specimen for turbine rotor

Note: One set of test specimens may be taken from one location given in the Figure.

Fig 2.1.26 Selection of test specimen for turbine disc

(3) Solid forged turbine rotors intended for main propulsion service where the inlet steam temper- ature exceeds 400 are to be subjected to stability tests at least once at a suitable time after rough machining or heat treatment. This requirement is also applicable to rotors fabricated by welding. The method of stability test is to be approved by the Society prior to the test.

16. Additional requirements for turbine blades Turbine blades are to be tested in accordance with the approved test specification.

602. Stainless steel forgings

1. Application

(1) Tinhge sryesqtuemiresmuesnetds

ate lotow atpepmlypetroatuthree (s-t1a6in5less asntedelovfoergiingsdefsoigr nvatlevmespearantdurep)ipeserfvititciengosr incoprriop-

sion-resisting service (hereinafter referred to as "steel forgings").

(2) Steel forgings having characteristics differing from those specified in 602. are to comply with the requirements in 101. 2.

2. Kinds Steel forgings are classified as specified in Table 2.1.85.

3. Heat treatment

Steel forgings are generally to

4. Chemical composition

The chemical composition of

2.1.85.

receive a solid solution treatment.

steel forgings is to comply with the requirements given in Table

Table 2.1.85 Grade and Chemical Composition

5. Mechanical properties

(1) The mechanical properties of steel forgings are to comply with the requirements given in Table 2.1.86.

(2) Where deemed necessary by the Society, impact test or corrosion resistance test may be re- quired in addition to the specified tests.

Table 2.1.86 Mechanical Properties

6. Selection of the specimens

(1) The number of tensile test specimens is to be in accordance with the requirements in 601. 7.

(2) Tensile test specimens are to be taken with their longitudinal axes parallel to the direction of forging, unless otherwise specially provided by the Society.

(3) Where tests are made in accordance with the requirements in 601. 7 (5), (c) and (d), the

Surveyor may require hardness test for each forging.

7. Marking

Steel forgings which have satisfactorily complied with the required test are to be marked with the identification mark in accordance with the requirements in 110.

603. Steel forgings for chains

1. Application

(1) These requirements are to apply to the steel forgings used for anchor chain cables and accesso- ries specified in Pt 4, Ch 8 (hereinafter referred to as "steel forgings").

(2) Steel forgings for manufacture of offshore mooring chain accessories are to be in accordance with the Guidance relating to the Rules specified by the Society. See Guidance

(3) Steel forgings having characteristics differing from those specified in (1) are to comply with requirements in 101. 2.

the

(4) In addition to the requirements given in Society. See Guidance

603., general requirements may be considered by the

2. Kinds

The steel forgings are classified as specified in Table 2.1.87.

Table 2.1.87 Grades of Steel Forgings

3. Heat treatment

The steel forgings are to be normalized, normalized and tempered, quenched and tempered or heat treated by the process approved by the Society.

4. Deoxidation practice and chemical composition

The deoxidation practice and chemical composition of each grade are to comply with the require-

ments given in Table 2.1.88. Elements other than specified in ject to a special approval by the Society.

Table 2.1.88 may be added sub-

Table 2.1.88 Deoxidation Practice and Chemical Composition (%)

5. Mechanical properties

The mechanical properties of each grade are to comply with

2.1.89.

the requirements given in Table

Table 2.1.89 Mechanical Properties

6. Selection of test specimens

(1) One test sample is to be selected from each lot of every 25 steel forgings or fraction thereof,

which belong to the same heat. In case of steel

test samples may be reduced subject to approval

forgings having small diameter, the number of

of the Society. Where specially approved by

the Society,

the test sample may be taken from the representative part of the steel forging at a

proper time during manufacturing, or a separate sample forged to the forge ratio equivalent to

that of the

steel forgings. In this case, the test sample is to be heat treated simultaneously

with the steel forgings.

(2) For Grade 1 and Grade 2 chain bars, one tensile test specimen is to be taken from the test sample; for Grade 3 chain bars, one tensile test specimen and one set (3 pieces) of impact test specimens are to be taken from the test sample.

(3) The tensile and impact test specimens are to be taken from the test sample in the direction of forging at a depth of 1/6 diameter from the surface or as close as possible to this position. (see Fig 2.1.5)

7. Surface inspection

Surface inspection for all grades is to be carried out and it is to be confirmed that there are no harmful defects.

8. Retest procedure

Where the tensile test or impact test on the selected first test specimens fails to meet the require- ments, additional tests may be carried out according to the requirements given in 306. 9.

9. Marking

Steel forgings which have satisfactorily complied with the required tests are to be marked with the identification mark in accordance with the requirement in 110.

604. Steel forgings for low temperature service

1. Application

(1) Ttehmes reinqtueinredmedentos abree utosedappalty thtoe

tdheesigstneeltemfopregriantgusrefolrowvearlvethsanand0 pipien filtitqinugefsieidn gpaispincgarrsiyesrs-

(hereinafter referred to as "steel forgings").

(2) Steel forgings other than those specified in 604. are to comply with the requirements given in

101. 2.

Kinds The steel forgings are classified as given in Table 2.1.90. 2.

Heat treatment 3.

The steel forgings are to be normalized, normalized and tempered, quenched and tempered or dou- ble normalized and tempered.

Deoxidation practice and chemical composition 4.

The deoxidation practice and chemical composition of each grade ments given in Table 2.1.90.

are to comply with the require-

Table 2.1.90 Grades and Chemical Composition

5. Mechanical properties

(1) The mechanical properties of steel forgings are to comply with

2.1.91.

the requirements given in Table

(2) Where deemed necessary by the specified in (1).

Society, other tests may be required in addition to the tests

Table 2.1.91 Mechanical Properties

6. Selection of tests specimens

(1) The number of test specimens is to be in accordance with the requirements specified in 601. 7.

(2) The test specimens for tensile and impact tests are to be cut with their longitudinal axes paral- lel to the direction of forging except where otherwise specially specified.

(3) Where tests are made in accordance with the requirements in 601. 7 (5), (c) and (d), the Surveyor may require a hardness test for each forging.

7. Retest procedures

(1) Where the tensile tests fail to meet the requirements, additional tests may be carried out accord- ing to the requirements given in 109.

(2) Regarding the impact tests, additional tests are to be carried out according to the requirements given in 304. 9.

8. Marking

Marking for steel castings is to comply with the requirements given in 601. 13. (1) and in case the requirement in Note (1) of Table 2.1.91. has been applied, "impact test temperature T" is to be suffixed to the marking (e.g. R L F A - 25T )