Workshop Recommendations

This leaflet contains general suggestions and calculation models. SSAB does hereby expressly exclude any liability whatsoever for their suitability for individual applications. It is the responsibilty of the user of the manual to adapt the recommendations contained herein to the requirements of individual applications. Project manager marketing Johan Lundin, Technical advisors Mikael Ringholm, Per Hansson

CUTTING RECOMMENDATIONS Protection plates manufactured by SSAB have lean chemical compositions. This simplifies the cutting process. However, to get the best cut quality, Armox should be cut under controlled conditions as described below.

Armox 370T CL1 & CL2

Armox 440

Armox 500T

Armox 600T

Armox Advance

Recommended cutting method • Abrasive waterjet

Up to 15 mm

Up to 25 mm

Up to 15 mm

Up to 10 mm

-

• Plasma • Laser • Abrasive disc • Abrasive waterjet • Laser

15 - 25 mm

25 - 35 mm

15 - 25 mm

10 -20 mm

-

• Gas cutting at reduced speed • Gas cutting plus preheating to 170 +- 30°C • Abrasive disc • Abrasive waterjet

40 - 60 mm

25 - 35 mm

40 - 60 mm

20 - 30 mm

-

Above 60 mm

Above 35 mm

Above 60 mm

Above 30 mm

Up to 7 mm

• Gas cutting plus preheating to 170 +- 30°C plus keep warm for 4 hours at 160 +- 40°C • Abrasive disc • Abrasive waterjet • Abrasive disc

ABRASIVE WATERJET

GAS CUTTING

This process can be applied to the complete range of high-hardness Armox plate, and is recommended as the best method, because the absence of HAZ eliminates the risk of cracking.

This process can be applied to high-hardness Armox plate up to 80 mm thickness. It generates a kerf of 2-5 mm and a HAZ which is usually 4-10 mm wide.

LASER CUTTING High-hardness Armox plate up to around 20 mm thickness can be cut using this process. It generates a narrow kerf, usually less than 1 mm, and a narrow HAZ, usually less than 3 mm.

PLASMA CUTTING High-hardness Armox plate up to around 25 mm thickness can be cut using this process. It generates a kerf, usually 3-4 mm, and a HAZ up to 5 mm. Plasma cutting can be performed under water, which minimizes the amount of distortion.

ABRASIVE DISC This process is usually applied to the cutting of tube and rod but can also be adopted for straight line cutting of the complete range of high-hardness Armox plate. The kerf is the thickness of the disc, with little or no HAZ.

Uncontrolled gas cutting of high-hardness armour plate may result in hydrogen cracking (also called cold cracking) which may occur in thicknesses above 20-30 mm. The thicker the plate, the higher the cracksensitivity. The most effective technique to avoid cracking during and after cutting is to preheat the plate and then keep the cut parts warm afterwords. Preheating consists of bringing the whole plate, or at least a 100 mm wide area on either side of the future kerf, up to a specified minimum temperature before the process begins. This can be done by using thermostatically controlled furnaces or, in some cases, using gas burners to maintain the temperature throughout the process. The same equipment can be used to keep the profiles warm for a specific time immediately following the cutting process. In some instances, thick plate profiles that are not prone to overheating can be cut at low speed, which obviates the need for preheating.

3

WELDING RECOMMENDATIONS SSAB manufactures protection plate with lean chemical compositions which simplify welding. Armox plates should be welded with a consumable which produces a low hydrogen content in the weld metal. Good results require that hydrogen, which can induce cold cracking, is kept away from the weld area. Armox plates can be welded by any conventional welding method. All Armox grades can be welded to other weldable steel.

The temperature should be maintained throughout the entire weld operation, tack welding and root passes included.

EDGE PREPARATION A good fit between the work pieces is essential to minimize stresses and thereby the risk of cracking. All types of impurities on and near the edges, such as mill scale, rust, oil, paint and moisture, should be removed before welding.

Armox plates have been developed to have as low carbon equivalent as possible without loss in hardness, strength and ballistic properties. Typical carbon equivalents are shown in the table below.

TACK WELDING During tack welding the cooling rate is more rapid which increases the risk of cold cracking. In areas of high restraint the minimum length of each tack weld should be 50 mm to prevent hydrogen cracking.

Steel grade

Thickness range

Carbon equivalent1

Armox 370T CL1 & CL2

3–150 mm

0.67–0.75 2

PREHEAT TEMPERARATURES

Armox 440T

4–30 mm

0.68–0.72

If austenitic consumables are used, the plate should be welded at least at room temperature (18–25°C). But when welding plates thicker than 30 mm, in combination with high levels of restraint, preheating is recommended.

Armox 500T

3–115 mm

0.67–0.75 2

Armox 600T

4–20 mm

0.85 2

Armox Advance

5–7 mm

0.95

1) Carbon equivalent (CEV) in accordance to IIW:

If unalloyed or low-alloyed consumables are used preheating is necessary and dependent on plate thickness and restraint conditions.

C + Mn + Cr + Mo + V + Cu + Ni 6 5 15

2) For plate thicknesses >80 mm, please contact SSAB

Minimum recommended preheat and interpass temperatures for different plate thicknesses (mm) Thickness 3 Armox 370 T Class 1 Armox 370 T Class 2

3-80 mm 3-150 mm

10 125°C 50°C

Armox 440 T

4-30 mm

Armox 500 T

3-140 mm

Armox 600 T

4-20 mm

150°C 75°C

125°C

20

30

175°C

100°C 125°C

40

50

200°C

60

70

80

140

100°C + austenitic

150°C

150°C 175°C

200°C

100°C + austenitic 100°C + austenitic

Armox Advance

5-7 mm

Measure the preheat temperature here

Maximum recommended preheat/interpass temperatures Armox 370 T Armox 370 T Class 2

400°C

Armox 440 T

200°C

Armox 500 T

200°C

Armox 600 T

180°C

Armox Advance

150°C

Measure the temperature of the thickest plate in the joint. If the plate is 25 mm thick, measure the temperature 2 minutes after heating. If the plate is 12.5 mm thick, measure the temperature after 1 minute, etc. The interpass temperature can be measured in the weld metal or in the immediately adjacent parent metal.

4

75 mm

Intended weld joint

150

Welding can be carried out directly on the excellent primer, due to its low zinc content. The primer can easily be brushed or ground away in the area around the joint. Removing the primer prior to welding can be beneficial, as it can minimize the porosity in the weld and can facilitate welding in positions other than the horizontal.

The table on the previous page is applicable to single plate thickness when welding with a heat input of 1.7 kJ / mm. If the ambient humidity is high or the temperature is below +5 °C, the lowest recommended preheat temperatures given should be increased by 25 °C. This also applies to firmly clamped weld joints and if the heat input is 1.0-1.6 kJ / mm. Preheat temperatures for heat inputs lower than 1.0 kJ /mm can be determined by an applicable standard for high strength steels. One example is method B in European Norm EN 1011-2. The lowest recommended preheat and interpass temperatures in the chart on the previous page are not affected at heat inputs higher than 1.7 kJ / mm.

position the welds in low stress areas. Select the consumables which produce the lowest possible level of hydrogen in the weld metal for the given weld process.

CHOICE AND HANDLING OF CONSUMABLES

The hydrogen content should be lower than or equal to 5 ml of hydrogen per 100 g of weld metal when welding with unalloyed or low-alloyed welding consumables. Solid wires used in MAG and TIG welding can produce these low hydrogen contents in the weld metal. The hydrogen content for other types of welding consumables can best be obtained from the respective manufacturer.

Consumables should be selected on the basis of strength and toughness requirements in the joint. We recommendend soft consumables with a yield strength of up to 500 MPa. In order to achieve an optimum combination of strength and toughness in the welded joint, select a consumable with as low strength as possible, but which still fulfils the strength requirements for the joint. Using low-strength consumables can offer several benefits, such as higher toughness of the weld metal, higher resistance to hydrogen cracking and lower residual stresses in the joint. Designers should therefore attempt to

Unalloyed or low-alloyed consumables EN 499 xxx H5 AWS: A 5.18-93 ER70S-6 E7018-1 AWS: A 5.28-79 ER80S-G

Austenitic consumables EN 1600 E 18 8 Mn AWS A/SFA 5.4-92 E 307-15 AWS A5.22 E 307 LT-2

OK 48.08, OK Femax 38.65 OK 55.00

OK 67.45 OK 67.52

Filarc 35 Filarc 56 S

Filarc BM 307

OERLIKON

Special Supercord S

COMET 307 SAFDRY R 307

THYSSEN

Phoenix 120 K SH Grün K52W

THERMANIT X

OK Autrod 12.51 OK Tubrod 15.00

OK Autrod 16.95 OK Tubrod 14.36

Filarc PZ 6000 Filarc PZ 6130

Filarc PZ 6070 Filarc PZ 6470

OERLIKON

FLUXOFIL 40 Carbofil 100

NERTALIC 51 SAFDUAL 651

THYSSEN

TG 50 B Union K52

THERMANIT X

Manufacturer

ELECTRODES

ESAB

FILARC

ESAB

WIRES

If consumables are stored in accordance with the manufacturer’s recommendations, the hydrogen content will be maintained at the intended level. This applies, above all, to coated consumables and fluxes.

FILARC

5

BENDING RECOMMENDATIONS This section deals with free bending, although roll bending can obviously also be employed. The bending results are dependent on a number of factors which we have grouped under three headings: the plate, the tools and the procedure. These factors are discussed on page 11, where a couple of examples also are given.

Bending transverse to the final direction of rolling

Bending line Grind away any blemishes before bending. Sheared edges should also be grinded.

b Final rolling direction. The plate identity is always stamped transverse to the final direction of rolling.

R t

The edges of the die opening should always be as hard as or harder than the plate being bent, in order to avoid damage to the die. To avoid plate surface damage, mill grooves in the die edges and fit lubricated round rods into the grooves. The die edge radius should be at least half the plate thickness.

The die opening angle must allow for springback of the plate. As an example, if Armox 500 shall be bent to an angle of 90°, the die opening angle should not exceed 70° (see table).

w

Minimum recommended punch radius (R) and die opening width (W) for plate thickness (t) when the plate is bent to 90° parallell to the final rolling direction and transverse to the final direction of rolling – and also the corresponding springback. Thickness [mm]

Transverse R/t

Parallell R/t

Transverse W/t

Parallell W/t

Springback [°]

Armox 370T CL1 & CL2

t-15

3.0 4.0 5.0

3.5 5.0 6.0

9 10 12

10.5 11 13

9-13

Armox 440

t-15

4.0 5.0 6.0

5.0 6.0 7.0

10 10 12

10 12 14

11-18

Armox 500T

t-15

5.0 6.0 7.0

5.0 6.0 9.0

10 12 16

12 14 18

12-20

Armox 600T & Advance

Contact SSAB

6

THE PLATE

creased, the bending force and impression marks will admittedly be reduced, but at the expense of increased springback.

Steel grade Note that the bending force and springback increase with the plate strength. The top tool radius should also be increased when increasing the plate hardness.

Note that the opening angle must be so small that it will allow a sufficient amount of over-bending. Note that in roll bending, the springback will be much larger than the tabulated values.

Plate surface Our recommendations apply to shotblasted and anti-corrosion painted plate. Surface damage and rust which is under tension during bending may greatly reduce the bendability. In critical cases, such defects must be ground away.

BENDING PROCEDURE Friction The die edges must be clean and undamaged. The bending force needed and the risk of cracking can be reduced by using round rods free to rotate as die edges and/or by lubricating the die edges.

Plate edges Cut and sheared edges should be deburred and rounded with a grinder.

Bending angle Note that the bending angle has less effect on the force needed and the springback than the die opening width and steel grade. Springback can be compensated by over-bending by the same number of degrees.

Plate thickness (t) As a general rule, thinner plate can be bent to smaller radii.

Final rolling direction

Bending force (P)

The plate can be bent to a smaller radius transverse to the final rolling direction than bending parallell to the final rolling direction.

The bending force necessary can be estimated using the formula below. The force is obtained with an accuracy of ±20%, provided that all dimensions used are in mm. For symbols used, see figure on page 9.

Bend length (b) If the bend length is less than 10 times the plate thickness, the plate can often be bent to a smaller radius than the values given in table below.

P=

P [ton]: Bending force b [mm]: Bending length t [mm]: Thickness Rm [MPa]: Tensile strength w [mm]: Die opening width

1,6 x b x t2 x Rm 10000 x w

THE TOOLS Punch radius (R)

If the radius of the punch used for bending is much larger than that specified in the table on page 9, the force needed may be higher than the value obtained from the formula, unless the die opening width is increased correspondingly.

Choosing the right punch radius is the most important factor when bending Armox. A punch radius which is equal to or somewhat larger than the required bending radius is recommended.

Die opening width (W) The table (on page 9) specifies the minimum recommended die opening for minimizing the springback. If the width is in-

Hardness [HBW]

Tensile strength Rm [MPa]

Elongation A5 [%]

180

550

28

Armox 370T CL1 & CL2

380-430

1200

11

Armox 440

420-480

1400

10

Armox 500T

480-540

1600

8

S 355 acc to EN10025

Armox 600T Armox Advance

570-640

2000

7

58-63 HRC

>2000