Buyers usually pay attention to the hardness of gray cast iron. In the appendix of GB 9439-88, the hardness of gray cast iron is divided into six types according to Brinell hardness. There is a certain correspondence between hardness and tensile strength, and its empirical formula is:
When: HB = RH (100+0.438b)
When: HB = RH (44+0.724)
RH in the formula is called relative hardness, and its value is determined by the raw materials, melting process, treatment process and cooling rate of the casting. In a casting workshop, for gray cast iron castings with the same brand, similar wall thickness and quality, the above factors remain roughly certain, so the hardness and corresponding tensile strength are given for a casting workshop.
The relative hardness (RH) of gray cast iron ranges from 0.8 to 1.20. For the diagram of the relationship between hardness and tensile strength of gray cast iron, please refer to 3-29 in the first volume of Mechanical Design Manual. Please refer to the table below.
right hand
0.8
0.9
1.0
1. 1
1.2
GB9439-88
Half board and lodging
Half board and lodging
Half board and lodging
Half board and lodging
Half board and lodging
Half board and lodging
100
93
105
1 16
128
140
150*
122
135
15 1
165
180
163~220
200
150
169
188
206
225
170~24 1
250*
166
188
2 10
230
250
170~24 1
300
185
208
23 1
255
278
350*
203
226
252
278
303
Generally speaking, it can be considered that the following properties of gray cast iron increase with the increase of brand number HT 100 to HT350:
1) various strengths, including high-temperature strength;
2) the ability to obtain low machining roughness;
3) elastic modulus;
4) Wear resistance;
However, with the increase of tensile strength, the following properties decrease.
1) machinability;
2) thermal shock resistance;
3) shock absorption;
4) Ability to cast thin-walled parts.
Performance and application:
It has certain tensile strength, good compressive strength (compressive strength is 3-4 times of tensile strength), excellent shock absorption, good wear resistance, machinability, greater sensitivity to wall thickness than ordinary metals, high temperature growth, low impact performance, high thermal conductivity and excellent casting process performance (shrinkage of gray cast iron is generally 0.5- 1.05%, while that of carbon cast steel, Good corrosion resistance (coarse graphite gray cast iron has good dilute acid resistance, and its corrosion resistance does not change much when the element content is in the ordinary range, but it has good corrosion resistance to alkaline solution at room temperature, molten caustic soda (650℃), salts, organic matter, crude oil, carbon disulfide and water in water pipes that are alkaline after hydrolysis. Adding 0.4- 1.0% copper to gray cast iron can increase the corrosion resistance to seawater, sewage and atmosphere. )
See the following table for the comparison of similar foreign brands:
Country names and standards
trademark
Britain, England
BS 1452-77
United States of America
ASTM448-76
Federal Republic of Germany (FRG)
DIN 169 1
the Soviet Union
гoct 14 12-79
France
NFA32- 10 1
Japan
JISG550 1- 1956
HT 150
150
25B
GG- 15
Sc 15
Ft 15D
FC 15
HT200
No.220
30B
GG-20
Sc20
Ft20D
FC20
HT250
No.260
40B
GG-25
Sc25
Ft25D
FC25
1 and HT 150 are often used to manufacture parts under moderate stress, such as pillars, bases, gear boxes, end covers, valve bodies, pipes and handwheels. Good corrosion resistance to concentrated sulfuric acid. In the water pump industry, it is used to manufacture the pump body, impeller, shaft sleeve, sealing ring and stuffing ring of various small and medium-sized fresh water pumps, as well as the base, bearing end cover, stuffing box, sealing ring and bearing body of various impurity pumps.
2.HT200 is often used to manufacture more important parts under greater stress. Such as cylinder, flywheel, bearing seat, hydraulic pump, valve body, etc. It is usually used for casting pump body, bearing seat, base and impeller and various small pump castings, and is used for many parts that need corrosion resistance, especially those that are resistant to concentrated sulfuric acid corrosion. (Its corrosion resistance to concentrated sulfuric acid is the same as HT 150).
3.HT250 is often used to manufacture important parts that bear great stress, such as cylinders, bases, flywheels, couplings, gearboxes, bearing housings and housings of hydraulic pumps and valves. In the pump industry, it is usually used to manufacture various parts of small and medium-sized fresh water pumps, such as pump body, impeller, shaft sleeve, sealing ring and packing ring. Good corrosion resistance to concentrated sulfuric acid.
(2) Ductile iron: In addition to the characteristics of ordinary cast iron, ductile iron also has the following characteristics: good heat resistance, certain corrosion resistance, high high-temperature mechanical strength and plasticity, and good energy impact resistance. Tensile strength and elongation are the basis of acceptance of ductile iron.
See the following table for the comparison of similar foreign brands:
Country name and
standard
trademark
Britain, England
BS2789-85
the Soviet Union
гoct 7293-85
Japan
JISG5502-82
international standard
ISO 1083-87
United States of America
ASTM 536-77
comment
Brinell hardness HB
QT400- 18
400/ 18
bч40
FCD37
400- 18
130~ 180
QT450- 10
450/ 10
bч45
FCD45
450- 10
160~2 10
QT500-7
500/7
bч50
FCD50
500-7
80-55-06
170~230
QT600-3
600/3
bч60
FCD60
600-3
80-60-3
190~270
1 and Qt 400- 18 are ferritic ductile iron. The strength, elongation and impact value of this material are higher than that of malleable cast iron, and it has a high ability to bear large energy impact load at room temperature. Its low energy and multiple impact resistance at room temperature and low temperature are better than malleable cast iron. In addition, it also has certain corrosion resistance (corrosion resistance is better than gray cast iron). It can be used to manufacture the runner of axial flow pump or vortex pump, the water inlet joint of submersible pump for well, etc.
2.Qt 450- 10 is ferritic ductile iron, which has similar properties as low carbon steel, namely high toughness and high plasticity; It has lower ductile-brittle transition temperature and higher low-temperature impact value. This nodular cast iron also has certain heat resistance and corrosion resistance. It is mainly used to manufacture parts that require high toughness, plasticity and certain impact value when working at low temperature. In the pump industry, it is used to manufacture the coupling of multistage centrifugal pump, the inlet flange of pump seat, the runner of axial flow vortex pump, the inlet joint of well submersible pump, etc.
3.Qt 500-7 is a nodular cast iron with ferrite and pearlite mixed matrix, which has excellent comprehensive mechanical properties and is suitable for manufacturing parts bearing general dynamic load and static load. The water pump industry is widely used to manufacture the pump body, pump cover, bracket, bearing body, fixture, labyrinth sleeve, skeleton parts and connecting rod of marine electric reciprocating pump. Wear resistance is generally better than gray cast iron and hardness is generally higher than malleable cast iron, so wear resistance is also better than malleable cast iron. The corrosion resistance is higher than that of ordinary pearlite gray cast iron, but far lower than that of ferritic ductile cast iron.
4.Qt 600-3 is ductile iron with pearlite and a little ferrite matrix. This material has high strength, hardness, wear resistance, plasticity and toughness, and its yield ratio is higher than that of 45 steel. It is usually used for dynamic load components that require high strength and wear resistance. The corrosion resistance is much lower than that of ferritic ductile iron. In the water pump industry, it is used to manufacture crankshafts and connecting rods of marine electric reciprocating pumps, connecting rods and bow frames of metering pumps, shells of large and medium-sized submersible pumps, crankshafts of high-pressure pumps, etc.
(3) Malleable cast iron: Malleable cast iron is also called Masteel. Because the carbon content is higher than that of cast steel, it has better castability than cast steel, and its toughness is similar to that of the corresponding cast steel after heat treatment. Malleable cast iron has the following advantages:
* with high strength, σ b300 ~ 375 MPa;
* It has high plasticity with an elongation of 6 ~12%;
* It has high toughness, and the impact toughness of notched samples can reach100 ~137 kJ/m3;
* Excellent heat resistance;
* Excellent atmospheric corrosion resistance;
* Excellent shock absorption performance;
* more stable than ductile iron;
* Easy to organize assembly line production;
* Good machining and cutting performance.
The production cycle of malleable cast iron is longer. Its production is divided into two stages. In the first stage, a white iron blank is cast by molten iron with a certain composition; In the first stage, the finished malleable cast iron is obtained by graphite annealing or decarburization annealing. Malleable cast iron is divided into black core malleable cast iron and white core malleable cast iron. More than 90% of malleable cast iron produced in China is black core ferritic malleable cast iron. It is mostly used to manufacture parts that are impacted and vibrated, such as automobiles, tractors, railway buildings, agricultural machinery castings, plumbing fittings, power line fittings and so on. Black core malleable cast iron includes KTH300-06 (joint of pump pipe, etc. ), KTH330-08 (The pump industry is usually used to manufacture the inlet flange of the pump, etc. ), KTH300- 10 (the pump industry is usually used to manufacture the inlet flange of the pump, etc. ) and KTH300- 12. Among them, KTH330-08 and KTH300- 12 are recommended brands.
Compared with similar foreign brands:
Domestic brand
Country and
Standard code
KTH300-06
KTH330-08
KTH350- 10
Britain (BS 668 1-86)
B30-06
B32- 10
B35- 12
Sweden (multinational company 707E-77)
SISO8 14-00
Spain (UNE 36114-63+04-63)
Type c
Soviet union (γ OCT 12 15-79)
КЧ30-6
КЧ33-8
КЧ35- 10
Japan (JISG 5702-78)
FCMB28
FCMB32
FCMB28(35)
International Organization for Standardization (ISO5922-8 1)
B30-06
B32- 12
B30-06
West Germany (DIN 1692-82)
GTS35- 10
France (NFA 32-702-82)
MN350- 10
Tensile strength σb(Mpa)
300
330
350
Elongation δ (%)
six
eight
10
Brinell hardness HB
≤ 150
≤ 150
≤ 150
(4) Corrosion resistant cast iron
1 and STNiCr are low nickel-chromium alkali-resistant cast irons, which are characterized by: the mechanical properties are improved compared with ordinary cast irons; Corrosion resistance, especially alkali resistance, is greatly improved; It has good heat resistance; Like ordinary cast iron, it has good castability.
Application in pump production The overflow part of chemical pump containing NaOH, Na2CO3, KOH and other alkaline media is applied. Such as pump body, pump cover, impeller, suction pipe, discharge pipe, etc. Yangquan Water Pump Factory applied cast iron to LKG chemical pump for extracting sodium hydroxide solution in alumina plant.
2.STA 15 is alkali-resistant cast iron containing 4 ~ 6%. It has the following excellent properties: good corrosion resistance in ammonia-alkali mother liquor; Excellent sulfur corrosion resistance; It has good heat resistance; Hardness and corrosion resistance are higher than those of aluminum-free gray cast iron; It has good vibration reduction ability. It has the following disadvantages: poor casting performance, easy to appear casting defects such as slag inclusion, crack, shrinkage cavity and composition segregation; Aging treatment is needed, and sometimes high temperature annealing treatment is needed, so the corrosion resistance will be better.
Overview of application aluminum cast iron has been used as a heat-resistant material in the past, and in recent years it has been used as a corrosion-resistant material for manufacturing equipment such as sodium carbonate, ammonium chloride and ammonium bicarbonate in the chemical industry. In the pump industry, it is mainly used as a corrosion-resistant material for alkali pumps. For example, W vortex pump produced by Yangquan Water Pump Factory is used to pump ammonia mother liquor in small chemical fertilizer industry.
3.ATNi 15Cu6Cr2 is flake graphite austenitic cast iron.
Compared with similar foreign brands:
country
standard
trademark
West Germany
DIN 1692-8 1
GGL-NiCuCr 1562
France
NFA32-30 1-72
Left nucleus 1562
Britain, England
BS3468-86
F 1
United States of America
ASTM 436-78
Type I
International Organization for Standardization (ISO)
ISO2892-73
L-NiCuCr 1562
(5) High-silicon corrosion-resistant cast iron: Five grades of high-silicon corrosion-resistant cast iron are specified in GB849 1-87, namely, STSI 1 1Cu2RR, STSi 15Mo3R, STSi 15R and STSI65438.
Similar brand: Si 14 (British BS1591-75); +0-75); No. 1 (American ANSI/ASTMA5 18-80).
See the following table for performance, applicable conditions and application examples:
trademark
Performance and applicable conditions
Application example
STSi 1 1Cu2CrR
It has good mechanical properties and can be produced by general machining methods. It has stable corrosion resistance in sulfuric acid with a concentration greater than or equal to 10%, nitric acid with a concentration less than or equal to 46% or mixed acid composed of the above two media, chlorinated sulfuric acid with a concentration greater than or equal to 70%, benzene, benzene sulfonic acid and other media, but it cannot withstand rapid alternating load, impact load and sudden temperature change.
Horizontal centrifuges, submersible pumps, valves, cocks, towers, cooling drains, bends and other chemical equipment and parts.
STSi 15R
STSi 17R
It has good corrosion resistance in oxidizing acids (such as nitric acid and compound acid at various temperatures and concentrations), various organic acids and a series of salt solutions, but it is not resistant to corrosion in halogen acids, salt solutions (such as hydrofluoric acid and fluoride) and strong alkali solutions, and severe alternating load, impact load and sudden temperature change are not allowed.
Various centrifugal pumps, valves, cocks, towers and tanks, pipe fittings, low-pressure vessels and various non-standard parts.
STSi 15Mo3R
In sulfuric acid, nitric acid and hydrochloric acid with various temperatures and concentrations, in alkaline aqueous solution and saline solution, when the temperature difference between parts on the same casting is not more than 30℃, it has particularly high corrosion resistance without dynamic load, alternating load, impact load and pulse load.
be the same as the above
STSi 15Cr4R
It has excellent electrochemical corrosion resistance and improved corrosion resistance under antioxidant conditions. Chromium in high silicon chromium cast iron can improve its passivation and pitting breakdown potential. However, severe alternating load, impact load and sudden temperature change are not allowed.
It is widely used as an auxiliary anode casting in impressed current cathodic protection system.
STSi 14.5Cu6
STSi 13Cu5
Adding copper can not only improve the corrosion resistance to hot sulfuric acid, but also improve the mechanical properties, increase the strength of the material, reduce the hardness and improve the impact toughness processability.
Multi-stage pump impeller, guide vane, single-stage pump shell with bearing cover, impeller back cover.
(VI) Wear-resistant white cast iron: There are four main types: low alloy white cast iron, nickel hard white cast iron, high composite white cast iron and medium manganese wear-resistant ductile iron.
Low-alloy white cast iron mainly includes KmTBMn2W2, KmTBCrMn2, KmTBCr 1, KmTBCr2Ni, KmTBMn3Cr2MoCu and so on.
Nickel hard white cast iron mainly includes KmTBNi4Cr2-GT (nickel hard I type) and KmTBCr9Ni5Si2 (nickel hard IV type);
The high complex white cast irons mainly include KmTBCr 15Mo2-GT, KmTBCr20Mo2, KmTBCr26, etc.
Medium manganese wear-resistant ductile iron mainly includes MQTMn6Mo.
1 and KmTBCr 1 have low wear resistance and are used for equipment with low wear resistance (Yangquan Water Pump Factory uses this material to manufacture the pipeline of slag pump). Similar brand Allen ASH64. Hardness HB 280-340, tensile strength 150- 180ma, bending strength 320-360Ma. The formability is worse than that of gray cast iron, the weldability is worse than that of gray cast iron, and the machinability is worse than that of gray cast iron, but it is better than other wear-resistant white cast irons.
2.KmTBCr2Ni has high wear resistance and good heat resistance, and is suitable for pumps with low wear resistance and simple heat-resistant iron castings. Similar brand Allen ASH65. Hardness HB 400-500, casting performance is better than ordinary gray cast iron, welding performance is worse than gray cast iron, cutting performance is worse than gray cast iron, but it is easier to process than nickel hard white cast iron.
3.KmTBMn2W2 was jointly developed by Shijiazhuang Water Pump Factory and Shenyang Foundry Research Institute on 1973. Shijiazhuang Water Pump Factory uses this material to mass produce all kinds of PN and PS sheaths, impellers, guard plates and other over-current components. Chemical composition: 2.5-3.0% carbon, 0.5- 1.5% silicon, 1.3- 1.6% manganese, 1.2-2.0% tungsten, 0./kloc. = 0.10% p. Hardness HRC & gt=38, bending strength 450MPa.
Casting performance: poor fluidity, large linear shrinkage (about 2%), easy to appear defects such as porosity, shrinkage cavity and crack.
Poor welding performance.
Cutting and grinding performance: can be used for processing.
4.KmTBMn3Cr2MoCu is mainly used for overflow parts of mud pumps, such as pump body, pump cover and impeller.
Hardness: as-cast HRC 28-35, heat treatment HRC & gt=50.
Bending strength: as-cast 500Mpa, heat treatment 600Ma.
The casting performance is better than that of ordinary low alloy white cast iron.
Cutting and grinding performance: usually quenching heat treatment is carried out after as-cast processing, and grinding into finished products after heat treatment.
5.KmTBMn5W3 was jointly developed by Shijiazhuang Water Pump Factory and Shenyang Foundry Research Institute on 1973. Chemical composition: 3.0-3.5% of carbon, 0.8- 1.3% of silicon, 4.0-6.0% of manganese, 2.5-3.5% of tungsten and 0. 10% of sulfur. = 0.15% p. hardness HRC55-65, bending strength 450-570MPa.
Castability: poor fluidity, large linear shrinkage (1.98-2.2%), easy to produce defects such as porosity, shrinkage cavity, porosity and cracks.
The welding performance is very poor, so welding is generally not carried out.
Cutting performance: it can be cut.
6.KmTBCr5Mn2 is one of the anti-wear materials for impurity pumps developed and used by Zigong Industrial Pump Factory 1982. There are two kinds of high carbon (GT) and low carbon (DT). Chemical composition: 2.6-3.2% carbon, 4.5-6.5% chromium, 0/.5-2.5% manganese, 0/.2-1.5% molybdenum and 0/.2-2.0% copper.
Hardness: kmtbcr5mn2-gt, HRC 52-60; KmTBCr5Mn2-DT，48-56 .
Casting performance: poor fluidity, large linear shrinkage, easy to appear defects such as porosity, shrinkage cavity, shrinkage porosity and cracks.
It is mainly used to manufacture easily damaged over-current components such as impeller, pump body, sheath and guard plate of small and medium-sized impurity pumps. Its service life is as follows
Conveying power plant fly ash: 2500-5500h；; Conveying river sand: 2500-5000 h; Coal preparation plant > 3500 hours; Cement transportation: 2500-4500 hours; ; Aluminum slurry in aluminum plant: 2000 hours.
7.KmTBNi4Cr2-GT This alloy contains more nickel and the cost is higher.
Similar brand: Germany (DIN1695-81) G-X330N; Cr42. UK (BS 4844/2-72) No.2 B. Sweden (MNC708e-71) SIS0513-00 USA (ASTM 4532-80) IAICR-HC.
Abroad, it has been widely used to manufacture impeller, impurity pump sheath, plate hammer of mine crusher, lining plate of ball mill, grinding ball, blade of shot blasting machine, lining plate and so on. Hardness after heat treatment HRC >；; =55。
Wear resistance: better than low alloy white cast iron, but worse than high complex white cast iron.
Castability: poor fluidity, large linear shrinkage (about 2%), prone to shrinkage porosity, shrinkage cavity, hot cracking and other defects.
The welding performance is very poor, so welding is generally not carried out. When welding is needed, special covered electrode is needed and special welding process is adopted.
Cutting and grinding performance: YH2 cemented carbide tool can be used for cutting.
8. Compared with KmTBNi4Cr2-GT, KmTBCr9Ni5Si2 has higher wear resistance.
Similar brand: Germany (DIN1695-81) G-X300crnisi952. Britain (BS 4844/2-72) No.2 C, D and E Sweden (MNC708E-7 1)SIS0457-00. United States (ASTM4532-80)IANi-HiCr
Hardness: The lowest hardness of sand casting is HB550, and the highest hardness after quenching is HB600.
Wear resistance: better than KmTBCr26, but not as good as KmTBCr 15Mo3.
Castability: poor fluidity, large linear shrinkage (about 2%), prone to shrinkage porosity, shrinkage cavity, hot cracking and other defects.
The welding performance is very poor, so welding is generally not carried out. It is slightly more difficult to machine than KmTBNi4Cr2-GT cast iron.
9.KMT BCR 15Mo2-DT (GT) is characterized by medium carbon, high complexity and low molybdenum. Ⅲ
Similar brand: Germany (DIN1695-81) G-X300 CRMO153. Britain (BS4844/3-86)3A (low carbon 2.4-3.0%) and 3B (high carbon 3.0-3.6%). Usa (ASTM 4532-80) Ⅲ c15% Cr-Mo HC. See the table below for hardness:
Material trademark
Hardness HRC
As cast condition
as-quenched
Softening annealing state
KmTBCr 15Mo2-DT
40-56
& gt=58
& lt=40
KmTBCr 15Mo2-GT
50-58
& gt=58
& lt=40
Heat treatment system: it is very difficult to process this material in as-cast or hardened state. Generally, it needs high-temperature softening annealing, rough cutting, hardening heat treatment and finishing to the finished product.
Moldability: linear shrinkage is about 2% and volume shrinkage is about 3.98%. Casting is prone to shrinkage cavity, crack and other defects.
The welding performance is very poor, so welding is generally not carried out. However, if necessary, local defects of castings can be repaired by high temperature cast iron welding rod.
Cutting and grinding performance: cutting can be performed after softening and annealing, and grinding can be performed after quenching and hardening. At present, ceramic tools are being studied and popularized at home and abroad for turning.
10 and KmTBCr26 have good comprehensive properties-high wear resistance, good toughness and easy annealing. Mainly used for parts requiring high wear resistance, high corrosion resistance and high temperature oxidation resistance. Such as slurry pump, crusher, ball mill, shot blasting machine and other wearing parts.
Similar brand: Germany (DIN1695-81) G-X26cr27. Britain (BS4844-86)3D (low carbon), 3E (high carbon). American (ASTM 4532-80) Ⅲ 25% Cr. The hardness of Sweden (MNC708E-7 1) is shown in the following table:
Material trademark
Hardness HRC
As cast condition
as-quenched
Softening annealing state
KmTBCr26
50-58
& gt=55
& lt=40
Moldability: linear shrinkage is about 2. 1%, and the shrinkage rate is 4.03%. Defects such as shrinkage cavity and hot cracking are easy to occur.
The welding performance is very poor, so welding is generally not carried out.
Machinability: Generally, it is processed after annealing. As-cast or quenched workpieces can be directly cut with cemented carbide tools or ceramic tools.
1 1 and KmTBCr 18 are divided into high-carbon GT(2.8-3.2%C) and low-carbon DT(2.0-2.6%C). High carbon type is mainly used for erosion wear of neutral or alkaline slurry; Low-carbon type is mainly used for erosion and wear of PH> acid mud =3.
Similar brands: French standard number 24 10Cr 18, German standard number X4 10Cr 18.
Hardness: high carbon type, as-cast HRC = 50-54, quenched HRC 58-62; Low carbon type, as-cast H.
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