"Cast steel" redirects here. For another sense of that term, see cast steel.
Steel casting is a specialized form of casting involving various types of steel cast to either final/net or near-net shape. Steel castings are used when iron castings cannot deliver enough strength or shock resistance.[1]
Steel is more difficult to cast than iron. It has a higher melting point and greater shrinkage rate, which requires consideration during mold design. Risers should be given more capacity to draw from as the metal cools and shrinks. Attention should be paid to the thickness of mold cavities, as thinner areas will cool quicker than thicker areas, which can create internal stress points that can lead to fracture.
Molten steel is also less fluid than molten iron, making it more difficult to pour and fill intricate gaps in a mold cavity. Molten steel is also more likely to react with internal mold surfaces, making for more unpredictable results.
Cast parts often require machining to achieve accurate tolerances and desired surface finishes. Carbon steel is the easiest type of steel to machine. High-carbon steel can be more time consuming to cut or grind, and will wear tools faster. Low-carbon steel can get gummy, making it difficult to work with.
Generally, the presence of alloys used to increase mechanical performance often make machining more difficult.
Damping ability
Casting is often a valuable means to creating intricate parts used in machine applications where vibration is often a factor. Cast steel typically has a lower damping ability than cast iron, which can lead to excess vibration and noise in the form of ringing or squealing.
Impact and wear resistance
Most steels offer a good balance of strength and ductility, which makes them extremely tough. This allows them to withstand significant stress and strain without fracturing. Steel can also be fairly wear-resistant. Alloy additions can increase both impact and wear resistance.[3]
Steel casting alloys
Alloy steel castings are broken down into two categories: low-alloy steels and high-alloy steels.[4] Low-alloy steels contain less than 8% alloying content and high-alloy steels have 8% or more.[4]
This is a table of some steel casting alloys:
Heat resistant steel castings per ASTM A297-1981[4]
Grade
Nominal alloy composition (%wt)
Tensile strength, minimum
Yield strength to 0.2%, minimum
Elongation, minimum, from 2 in, 51 mm (%)
(ksi)
(MPa)
(ksi)
(MPa)
HC
28 Cr
55
380
-
-
-
HD
28 Cr, 5 Ni
75
515
35
240
8
HF
19 Cr, 9 Ni
70
485
35
240
25
HH
25 Cr, 12 Ni
75
515
35
240
10
HI
28 Cr, 15 Ni
70
485
35
240
10
HK
25 Cr, 20 Ni
65
450
35
240
10
HL
29 Cr, 20 Ni
65
450
35
240
10
HN
20 Cr, 25 Ni
63
435
-
-
8
HP
26 Cr, 35 Ni
62.5
430
34
235
4.5
HT
15 Cr, 35 Ni
65
450
-
-
4
HU
19 Cr, 39 Ni
65
450
-
-
4
HW
12 Cr, 60 Ni
60
415
-
-
-
HX
17 Cr, 66 Ni
60
415
-
-
-
Corrosion resistant steel castings per ASTM A743-1981a[5]
Grade
Nominal alloy composition (%wt)
Tensile strength, minimum
Yield strength to 0.2%, minimum
Elongation, minimum, from 2 in, 51 mm (%)
(ksi)
(MPa)
(ksi)
(MPa)
CF-8
9 Cr, 9 Ni
70
485
30
205
35
CG-12
22 Cr, 12 Ni
70
485
28
195
35
CF-20
19 Cr, 9 Ni
70
485
30
205
30
CF-8M
19 Cr, 10 Ni, with Mo
70
485
30
205
30
CF-8C
19 Cr, 10 Ni, with Nb
70
485
30
205
30
CF-16 & CF-16Fa
19 Cr, 9 Ni, free machining
70
485
30
205
25
CH-10 & CH-20
25 Cr, 12 Ni
70
485
30
205
30
CK-20
25 Cr, 20 Ni
65
450
28
195
30
CE-30
29 Cr, 9 Ni
80
550
40
275
10
CA-15 & CA-15M
12 Cr
90
620
65
450
18
CB-30
20 Cr
65
450
30
205
-
CC-50
28 Cr
55
380
-
-
-
CA-40
12 Cr
100
690
70
485
15
CF-3
19 Cr, 9 Ni
70
485
30
205
35
CF-3M
19 Cr, 10 Ni, with Mo
70
485
30
205
30
CG6MMN
Cr-Ni-Mn-Mo
75
515
35
240
30
CG-8M
19 Cr, 11 Ni, with Mo
75
520
35
240
25
CN-7M
20 Cr, 29 Ni, with Co & Mo
62
425
25
170
35
CN-7MS
19 Cr, 24 Ni, with Co & Mo
70
485
30
205
35
CW-12M
Ni, Mo & Cr
72
495
46
315
4
CY-40
Ni, Cr & Fe
70
485
28
195
30
CA-6NM
12 Cr, 4 Ni
110
775
80
550
15
CD-4MCu
25 Cr, 5 Ni, 3 Cu, 2 Mo
100
690
70
485
16
CA-6N
11 Cr, 7 Ni
140
965
135
930
15
Terminology
In present-day vocabulary, the term cast steel is almost always used in its sense referring to steel castings. Between the late 19th and mid 20th centuries, this was not always true, which is worth understanding if one is reading historical documents; see cast steel for details.