The commonly used materials of metal bellows

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Metallic bellows are wave-shaped tubes, also known as expansion or expansion joints. Metal bellows are elastic pipes that can be compressed or extended when pressure is applied to the outside of the pipe. When the pressure released and the material has not been stressed past its yield strength, the bellows will return to its original shape. The metal bellows are mainly used for non-concentric axial transmission with small bending radius, irregular turning, expansion or absorption of thermal deformation of pipes, etc., which is not convenient to connect pipes with pipes or connect pipes with equipment in the installation of fixed elbows.

Due to its excellent performance, it is widely used in automatic control and measuring instruments, vacuum technology, mechanical industry, electric power industry, transportation and atomic energy industry and other fields such as sensitive components, shock absorption components, non-concentric axial drive components, compensation components, sealing components, valve components and pipeline connections. Metal bellows should be selected according to the application and performance of different metal materials. The Common materials of metal bellows are carbon steel, copper, stainless steel, steel lined plastic, aluminum, titanium and so on. Today, lkalloy will discuss with you the common materials of metal bellows in details:

 

Copper alloy

Tin bronze C51900 ~ 0.1 X – 60 ℃ ~ + 100 ℃ metal bellows tube combined excellent flexibility and strength, has a good brazing and corrosion resistant performance. Hysteresis and elastic aftereffect are small and widely used as measuring elements.

Brass Bellows C24000 H – 60 ℃ ~ + 100 ℃ with low elasticity, large hysteresis and aftereffect, brazing sex is good.Can be used for non-corrosive media and precision is not high in the instrument as a measuring element.

Beryllium bronze Bellows C17510 P – 60 ℃ ~ + 150 ℃, nonmagnetic, have a very small hysteresis and elastic aftereffect, high flexibility, corrosion resistance, used for high precision measuring instrument.

 

Stainless steel

Bellows SUS321 G – 194 ℃ ~ + 400 ℃ has the very high bending fatigue strength and corrosion resistance, good welding performance, can be used as a measure of corrosive medium, sealing, connection and compensating element. Common brands are 304, 304L, 316, 316L, 317L, 310S, 321, etc. There are more special, high corrosion resistant of 6Mo special stainless steel (super stainless steel) such as 254SMO, 904L, N08367 or N08926. Duplex stainless steel offers high strength but poor elongation, it’s not recommended for small bellows, large bellows processing can be considered according to the technical conditions.

 

Nickel-based alloy

High corrosion and high-temperature conditions should take into account the resistance to chloride ions, sea water, acid, alkali corrosion and high temperature resistant alloy materials, such as high nickel alloy, nickel ferrochrome alloys such as Incoloy 800H, Incoloy 825, Inconel 625, Monel400 and alloy c-276.

 

Titanium

Generally, it is pure titanium Gr.1. It has high elongation while poor welding performance, which should be taken into consideration.

 

 

What are the effects of alloying elements on Nickel-based steel?

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The Nickel retains its austenitic cubic structure until it reaches the melting point, which provides freedom for ductile-brittle transition and greatly reduces manufacturing problems caused by the presence of other metals. Nickel is more inert than iron and more active than copper, so the order of corrosion resistance in reducing environment is Copper > Nickel > Iron. The addition of chromium on the basis of nickel provides the alloy with antioxidant properties, which can produce a wide range of alloys with the best resistance to both reducing and oxidizing environments.

For a certain nickel-based alloy, there are a variety of changes in the specific environment such as concentration, temperature, ventilation, liquid (gas) flow velocity, impurities, abrasion, cycle process conditions, etc., which will produce a variety of corrosion problems. These questions can be answered in nickel and other alloying elements.

Nickel-based alloys can hold more alloying elements in the solid solution state while maintaining good metallurgical stability compared with stainless steel and other Fe-based alloys. These factors allow the addition of a wide variety of alloying elements, making nickel-based alloys widely used in a wide variety of corrosive environments. The common elements in Nickel-based alloys are:

Ni

Nickel provides metallurgical stability, improves thermal stability and weldability, increases corrosion resistance to reducing acids and caustic soda, and in particular increases stress corrosion cracking resistance in chloride and caustic soda environments.

Cr

Chromium improves the properties of oxidation resistance, high-temperature oxidation resistance, vulcanization resistance, high pitting resistance and gap corrosion resistance.

Mo

Molybdenum improves the corrosion resistance of reducing acid, the resistance to pitting corrosion, gap corrosion and high-temperature strength under the environment of chloride aqueous solution.

Fe

Iron improves resistance to high temperature carburizing environment, reduces alloy cost and controls thermal expansion.

Cu

Copper improves corrosion resistance to reducing acids (especially sulfuric acid and hydrofluoric acid, which are used in airless applications) and salts. The addition of copper to nickel-chromium-molybdenum-ferroalloys helps to improve corrosion resistance to hydrofluoric acid, phosphoric acid and sulfuric acid.

Al

Aluminum improves high-temperature oxidation resistance and aging hardening.

Ti

The combination of titanium and carbon reduces the intergranular corrosion caused by chromium carbide precipitation during heat treatment and improves the aging strengthening.

Nb

The combination of Niobium and carbon reduces intercrystalline corrosion caused by chromium carbide precipitation during heat treatment and improves pitting corrosion resistance, clearance corrosion performance and high-temperature strength.

W

Tungsten improves the resistance to reducing acid and local corrosion as well as its strength and weldability.

N

Nitrogen improves metallurgical stability, pitting corrosion resistance, gap corrosion resistance and strength.

Co

Cobalt provides enhanced high temperature strength, carbonation resistance, and vulcanization resistance.

 

Many of these alloying elements can be combined with nickel over a wide range of compositions to form single-phase solid solutions, ensuring excellent corrosion resistance of the alloys under many corrosive conditions. The alloy also has good mechanical properties under complete annealing without worrying about harmful metallurgical changes during manufacturing or hot working. Many high Nickel alloys can be strengthened by solid solution hardening, carbide precipitation, precipitation (aging) hardening and dispersion hardening.

Which alloy material is most resistant to caustic soda?

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Caustic alkali generally refers to caustic soda and caustic potassium, namely sodium hydroxide and potassium hydroxide. Caustic embrittlement or caustic cracking occurs when the alloy material cracks under the action of tensile stress and corrosion medium in alkaline solution. In alkaline solutions, the concentration of hydrogen ions is usually low and the corrosion rate in chemical media usually decreases with the increase of PH value. At certain PH values, the corrosion rate of some metals hovers around the lowest value, while the PH value increases continuously as the corrosion degree increases.

Caustic soda has a wide range of applications. It can be used in papermaking, textile printing and dyeing, alumina, daily chemical, pharmaceutical, water treatment, steel and other industries. Caustic corrosion occurs when metals come into contact with caustic soda. Caustic corrosion can lead to pitting and other localized corrosion, as they tend to form cathode films that concentrate corrosion in susceptible anode areas. Austenitic stainless steels and other low Nickel materials may experience stress corrosion cracking or general corrosion in hot caustic soda.

Nickel and its alloys offer excellent alkali corrosion resistance for high temperature and concentration environments. Generally, the corrosion resistance of caustic soda usually increases with the increase of nickel content. In alkaline media, the most commonly used nickel alloys are Nickel 200/201, Monel 400, Nickel 600 and 625.

Plant tests in 23% caustic soda in tank receiving liquor from evaporator. average temperature,104℃
Material Corrosion rate，mpy(mm/a)
Nickel 200 0.16(0.004)
Monel alloy 400 0.20(0.005)
Inconel alloy 600 0.17(0.004)

Factory and laboratory test results, some of which are shown in the table below, show that nickel 200/201 and high nickel alloys are very satisfactory for the treatment of these materials

Laboratory corrosion tests in evaporation of caustic soda from 73-96 %, with and without chlorate
Materials Corrosion rate, mpy(mm/a)
Without chlorate with 0.30% Chlorate
Nickel 200 1.5(0.038) 260(6.60)
Inconel alloy 600 2.2(0.056) 380(9.65)

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Anti-corrosiont nickel based alloy Hastelloy C22 VS C276

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Hastelloy alloy has good resistance to pitting corrosion, crevice corrosion and stress corrosion cracking. It was well tolerated for a variety of corrosive medium in oxidation and reduction environments, even as high temperature up to 677 ℃; Hastelloy c-22 and c-276 are the only materials that can resist the corrosion of wet chlorine gas, hypochlorite and chlorine dioxide solution, and offering significant corrosion resistance to high concentration of chloride solution (such as iron chloride and copper chloride).

Hastelloy c-22 and c-276 have excellent welding performance and have been widely used in chemical and petrochemical fields, such as components in contact with chlorinated organics and catalytic systems. They are especially suitable for high temperature, mixed with impurities of inorganic acids and organic acids (such as formic acid and acetic acid), seawater corrosion environment.

The specification difference from different counties is as follows:

Chinese GB/T 15007-2008 NS3308 NS334
American ASTM B462-2006

ASTM B574-2006

ASTM B575-2006

 N06022 N10276
Special Metals INCONEL® alloy 22 INCONEL® alloy 276
Haynes International HASTELLOY® C-22® HASTELLOY® C-276®
Japanese JIS H 4551:2000 NW6022 NW 0276
Nippon Yakin NAS NW22 NAS NW276
German DIN 17744:2002 NiCr21Mo14W

2.4602

 NiMo16Cr15W

2.4819
VDM Metals VDM® Alloy 22

Nicrofer® 5621 hMoW

 VDM® Alloy 276

 

The chemical composition (%)difference is as follows:

Grade Ni C Mo Cr Fe W Co Mn V
C22 56 0.01 13 22 3 3 2.5 0.5 0.35
C276 57 0.01 16 16 5 4 2.5 1 0.35

We can learn that from the table above, there are few differences in the term of chemical analysis except the content of Mo and Cr. Alloy 22 has a higher Chromium and Molybdenum content than C276, demonstrating improved corrosion resistance in oxidizing aqueous media when high levels of chloride ions are present. In addition, the other differences are:

  1. Welding material：Varestraint hot-cracking tests performed on commercial alloys revealed a weldability ranking as follows: C-22 > C-276. Intermetallic secondary solidification constituents have been found associated with weld metal hot cracks in Alloys C-276 and C-22(gas-tungsten-arc welds). In Alloy C-276, this constituent is a combination of P and ώ phases, and in Alloy C-22, this constituent is composed of σ, P, and ώ C276 welding materials are wire ernicrmo-4 and electrode enicrmo-4; C22 welding material is wire ERnicrmo-10, electrode Enicrmo-10.
  2. C22 offers better and more comprehensive corrosion resistance compared with common nickel-chromium-molybdenum alloys such as C-276, C-4 and 625. C22 can be considered as an upgraded version of C276.
  3. Hastelloy c-22 alloy has a density of 8.7g/cm3, less than that of C276 alloy (8.9). However, C22 is more expensive because the manufacturing cost of C22 is higher than that of C276.

Each alloy has been manufactured to provide a unique set of benefits, wherever it is applied. Both commonly used corrosion resistant alloy. Hastelloy C22 and C276Hastelloy C22 and C276 generally, replace each other in most cases. C276 is more versatile and the C22 offers better performance.

The welding of SAF 2507 steel for nuclear power plants

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Most nuclear power plants in the world use sea water as its cooling medium. Seawater is the most corrosive medium in the natural environment which are prone to produce pitting for common stainless steel materials. How to obtain welded joints with good seawater corrosion resistance is very important. Super duplex stainless steel SAF2507 offers good pitting resistance, is used in cooling pipes for most modern nuclear power plants.

SS2328 (00Cr25Ni7Mo4N) steel is a type of super duplex stainless steel developed in Sweden in recent years with a commercial brand SAF2507(UNSS32750), which belongs to the third generation of duplex stainless steel. Mainly used in harsh media, especially the chlorine-containing environment, such as sea water. The balanced composition of high chromium, high molybdenum and high nitrogen makes the steel offering high resistance to stress corrosion cracking, pitting and crevice. Here we will introduce the welding of SAF 2507 super duplex stainless steel, please keep reading on.

 

Welding methods

Due to its limited metallurgical properties of duplex stainless steel, the following principles should be followed when selecting welding methods:

  1. Avoid using too high or too low welding heat input. Too low heat input will greatly reduce the austenite precipitate, leading to the process and performance reduction. However, too high heat input will result in the precipitation of harmful phase and coarse grain in the welded joint which produces the reduction of corrosion resistance and toughness.
  2. Suitable for multi-layer welding: multi-times, low melting rate.TIG welding is chosen as the ideal welding method according to the practical site construction. The table below is the welding parameters recommended by Sandvik of Sweden.
Grade heat input/KJ mm Interpass temperature/ ℃
SAF2507 0.2 —1.5 <150

Welding material

Due to the thermal cycle of welding, the ferrite of the weld metal increases sharply during the self-fusion welding of duplex stainless steel, and the precipitation of nitride and secondary Austenite at the same time, leading to the decrease of toughness and corrosion resistance. In order to restrain the increase of ferrite in weld metal, austenite-dominated weld metal is the ideal choice for duplex stainless steel welding. Its advantages are: grain refinement, reduction of nitride precipitation, improvement of plastic toughness and wear resistance, enhancement of crack resistance and reduction of inhomogeneity of upper and lower layers in multi-layer welding.

It is feasible and useful to increase the content of nickel or nitrogen while decreasing the Cr in welding materials. The content of nickel in the filler material is usually 2%- 4% higher than its base material. The filling material containing nitrogen is better than which containing nickel only. Both elements can increase the proportion of austenite phase and use stable, but nitrogen addition can not only delay the precipitation of intermetallic phase, but also improve the strength and corrosion resistance of welding metal.

At present, the resistant filler materials are generally added with the same nitrogen content as the base material on the basis of improving nickel, so as to ensure the austenite content of the weld is 60% to 70%. The sandvik25.10.4.l wire was used for TIG welding of SAF2507 steel. The typical chemical composition is shown below:

Grade C Si Mn S max P max Cr Ni Mo N
Sandvik25.10.4.L 0.02 0.3 0.4 0.02 0.020 25 10 4 0.25

 

It is shown that 20%N2 in pure Ar gas is lost in surface-weld bead during TIG welding of super duplex steel. The addition of nitrogen to the shielding gas effectively avoids the loss of nitrogen, because too much nitrogen will make the weld metal produce porosity. In general. When SAF2507 steel was welded by TIG, Sandvik25.10.4 was selected.L wire shielding gas Ar +2% N2 was used to obtain the welded joints with good corrosion resistance to seawater.

The common material for hardfacing weld

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Hardfacing weld(build-up welding or overlaying) is a surface welding process that uses flame, arc and plasma arc to melt base metal to form a wear-resistant, corrosion-resistant and heat-resistant coatings on the surface of the workpiece. Hardfacing has characterized the function of repairing and surface strengthening. With the wide application of wear-resistant materials in industry, hardfacing has become an important surfacing technology to solve the failure of metal parts lead by  abrasion.
Composition and structure of surfacing material have an important influence on the performance of the whole component. According to the composition of hardface welding metal and the structure of surfacing layer, hardfacing alloys can be classified as iron-based, nickel-based, cobalt-based, copper-based and tungsten carbide and so on.

Iron-based alloys
Iron-based alloys are the most widely used hardfacing welding materials. It adds other alloying elements such as Cr, Mo, W, Mn, Si, V, Ni, Ti, B, etc based on the carbon which not only affects the formation of hardening phase in the surfacing layer but also affects the properties of the body structure. The biggest advantage of iron-based hardfacing materials is its lower cost. Due to the carbon content, alloy content and cooling speed, the structure of the surfacing layer can be pearlite, martensite, austenite and carbide, etc.
1.Pearlitic steel surfacing material. This alloy has good weldability, strong impact resistance but low hardness. It is mainly used for repairing mechanical parts of elephant shafts.
2. Austenitic steel surfacing material. Austenite has high impact toughness, good corrosion resistance and heat resistance. It is generally used to repair parts with intermetallic and abrasive wear under severe impact loads such as mine trucks and railway turnouts.
3. Martensitic steel surfacing material. The hardness, yield strength and wear resistance of Martensite building-up welding layer are higher and it can withstand medium impact strength, but its impact resistance is worse than that of pearlite steel and austenitic steel layer. Mainly used for repairing intermetallic wear parts, such as gears, tractor chassis, etc.
4. Alloy cast iron bead welding material. This kind of welding layer has high abrasive wear resistance, heat resistance, corrosion resistance, good oxidation resistance but mild impact resistance and easy to crack when building up welding. It is mainly used for bead welding of agricultural machinery, mining equipment and other parts.

Cobalt-based alloys
Cobalt-based bead welding metals, also known as Stellite alloys, mainly refer to cobalt-chromium-tungsten alloys, which can maintain high strength and hardness at about 650 C and have excellent corrosion resistance and wear resistance. Among these kinds of bead welding metals, cobalt-based alloys have the best comprehensive properties and are mainly used for surfacing parts at high temperature.

Nickel-based alloy 
Nickel-based alloys are the most widely used for hardfacing and it has excellent wear resistance, corrosion resistance, heat resistance and high-temperature oxidation resistance. They are usually used in corrosive media or high-temperature environments where low-stress wear occurs. Nickel-based alloys containing intermetallics such as Hastelloy C-22, are more suitable for tungsten gas shielded arc surfacing or plasma arc surfacing and used to surfacing the sealing surface of valves working in severely corrosive media. Nickel-based alloys containing carbides are cheaper than cobalt-based alloys and are ideal substitutes for cobalt-based surfacing metals.

Copper-based alloys
Copper-based bead welding metals are characterized for their excellent corrosion resistance, cavitation resistance and intermetallic wear resistance. They can be hardfaced on iron-based materials to make bimetallic parts and repairing worn parts. However, its ve poor sulfide corrosion resistance and high temperature creep resistance made it not easy to weld and are only suitable for environments below 200℃. This kind of bead welding metal is mainly used for welding of bearing bush, sealing surface of the low-pressure valve, etc.

Tungsten carbide alloys
Tungsten carbide hardfacing alloy wire is famous for its high hardness, wear resistance, strength and high forward elastic modulus. It has the highest wear resistance among all surfacing alloys and has become irreplaceable composite surfacing alloys for workpieces or surfaces under severe abrasive wear and gas-particle wear. It is widely used in oil drilling, metallurgical mining and coal mining, civil construction, building materials, sugar, power generation, agricultural machinery and other industries

Copper Grade Comparison Of Different Standands

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There are more than 450 copper and copper alloys grades, each with a unique combination of properties to suit many applications, manufacturing processes and environments such as Brass (copper-zinc alloys), Bronze alloys, Copper-nickel alloys, Nickel-nickel-zinc alloys and Beryllium copper alloys. Every country has standards of their own or general for the copper and copper alloys grades according to the chemical element contents. Here we collected a grade comparison list for copper and its alloys in Europe, American, Germany, Japan and China for your reference.

Copper AmericanASTM ChineseGB InternationalISO JapanJIS GermanDIN EuroEU
High

Copper

Alloys

 C17200 QBe2 CuBe2 C1720 CuBe2 CuBe2
C17200 QBe1.9-0.1 CuBe2 C1720 CuBe2 CuBe2
C17000 QBe1.7 CuBe1.7 – – CuBe1.7
C17500 QBe0.6-2.5 CuCo2Be – – CuCo2Be
C17510 QBe0.4-1.8 CuNi2Be – – CuNi2Be
C18200 QCr0.5 – – – –
C16200 QCd1 – – CuCd1 –
C14500 QTe0.5 – – CuTeP CuTeP
Yellow

Brasses

(C21000-

28999)

 C21000 H96 CuZn5 C2100 CuZn5 CuZn5
C22000 H90 CuZn10 C2200 CuZn10 CuZn10
C23000 H85 CuZn15 C2300 CuZn15 CuZn15
C24000 H80 CuZn20 C2400 CuZn20 CuZn20
C26000 H70 CuZn30 C2600 CuZn30 CuZn30
C26000 H68 CuZn30 C2600 CuZn30 CuZn30
C26130 H70A CuZn30As – – –
C26130 H68A CuZn30As – – –
C27000 H65 CuZn35 C2680 CuZn33 CuZn33
C27200 H63 CuZn37 C2700 CuZn36 CuZn36
C27400 H32 CuZn40 C2720 CuZn37 CuZn37
C28000 H59 CuZn40 C2800 CuZn40 CuZn40
Leaded

Brasses

(C30000-C39999)

 C33000 HPb66-0.5 CuZn32Pb1 – – –
C35600 HPb63-3 CuZn34Pb2 C3560 CuZn36Pb1.5 CuZn35Pb2
C37100 HPb62-0.8 CuZn37Pb1 C3710 CuZn39Pb0.5 CuZn37Pb1
C36000 HPb62-3 CuZn36Pb3 C3601 CuZn36Pb3 CuZn36Pb3
C35300 HPb62-2 CuZn37Pb2 C3713 CuZn38Pb1.5 CuZn37Pb2
C37100 HPb61-1 CuZn39Pb1 C3710 CuZn39Pb0.5 CuZn39Pb1
C37700 HPb60-2 CuZn38Pb2 C3771 CuZn39Pb2 CuZn38Pb2
C37710 HPb59-3 CuZn39Pb3 C3561 CuZn39Pb3 CuZn39Pb3
C37000 HPb59-1 CuZn39Pb1 C3710 CuZn40Pb2 CuZn39Pb1
Tin Brasses

(C40000-C49999)

 C41100 HSn90-1 – – – –
C44300 HSn70-1 – – CuZn28Sn1 –
C46200 HSn62-1 – C4621 CuZn38Sn1 CuZn39Sn1
C46400 HSn60-1 – C4640 CuZn38Sn1 CuZn39Sn1
P-Bronzes

(C5000-C52999)

 C50500 QSn1.5-0.2 CuSn2 – – –
C51100 QSn4-0.3 CuSn4 C5101 CuSn4 CuSn4
C52100 QSn8-0.3 CuSn8 C5212 CuSn8 CuSn8
Al-Bronzes

(C60800-C64699)

 C60800 QAl5 CuAl5 C5102 CuAl5As –
C61000 QAl7 CuAl7 – CuAl8 –
C61900 QAl9-4 CuAl10Fe3 C6161 CuAl8Fe3 CuAl8Fe3
C63010 QAl9-5-1-1 CuAl10Ni5Fe4 C6280 CuAl10Ni5Fe4 CuAl10Ni5Fe4
C62300 QAl10-3-1.5 CuAl10Fe3 C6161 CuAl10Fe3Mn2 –
C63000 QAl10-4-4 CuAl9Fe4Ni4 C6301 CuAl10Ni5Fe4 CuAl10Ni5Fe4
C63280 QAl10-5-5 CuAl9Fe4Ni4 C6301 CuAl10Ni5Fe4 CuAl10Ni5Fe4
C63020 QAl11-6-6 CuAl10Ni5Fe4 C6301 CuAl11Ni6Fe5 –
C65600 HSi80-3 – – – –
C68700 HAl77-2 CuZn20Al2 – CuZn20Al2 –
Copper Nickel Alloy (C70000-C73499) C70400 B5 – – – –
C71000 B19 – C7100 – –
C71300 B25 CuNi25 – CuNi25 CuNi25
C71500 B30 CuNi30Mn1Fe C7150 CuNi30Mn1Fe CuNi30Mn1Fe
C70400 BFe5-1.5-0.5 – – – –
C70600 BFe10-1-1 CuNi10Fe1Mn C7060 CuNi10Fe1Mn CuNi10Fe1Mn
C71500 BFe30-1-1 CuNi30Mn1Fe C7150 CuNi30Mn1Fe CuNi30Mn1Fe
Nickel Silvers

(C73500-C79999)

 C75200 BZn18-18 CuNi18Zn20 C7521 CuNi18Zn20 –
C77000 BZn18-26 CuNi18Zn27 C7701 CuNi18Zn27 CuNi18Zn27
C75400 BZn15-20 CuNi15Zn21 C7541 CuNi12Zn24 CuNi12Zn24
C79000 BZn15-21-1.8 CuNi18Zn19Pb1 C7941 CuNi18Zn19Pb1 –
C79200 BZn15-24-1.5 CuNi10Zn28Pb1 – CuNi12Zn30Pb1 CuNi12Zn25Pb1

LKALLOY is an industry-leading manufacturer and supplier of beryllium copper, copper nickel, and a wide variety of mixed copper alloys. These alloy grades are among the most important and widely used copper alloys due to the impressive range of attributes that can be attained.

Processing Properties Of Metal Materials

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The processing property of metal refers to the possibility or difficulty of obtaining qualified products in the cold or hot manufacturing process of mechanical parts, that is, the ability of materials to adapt to the practical production process requirements. Different processing conditions lead to different processing methods and product properties, such as casting, forging, deep drawing, bending, cutting, weldability, hardenability, etc. Process performance is often determined by a combination of complex factors (physical, chemical, mechanical ans so on).

 

  1. Castability

The ability of metal materials to obtain qualified workpieces by casting which measured by fluidity, shrinkage and segregation. Fluidity is the ability of liquid metal to fill a mold. Shrinkage refers to the degree of volume shrinkage during solidification and segregation refers to the inhomogeneity of chemical composition and structure in metal due to the difference of crystallization sequence in the process of metal cooling and solidification.

  1. Forgeability

It refers to the metal material can change the shape without crack performance in the pressure processing, that is the capacity, in the hot or cold environment, metal can be hammer forging, rolling, stretching, extrusion and other processing. Malleability is mainly related to the chemical composition of metal materials.

  1. Machinability

Machinability refers to the difficulty to become qualified workpieces in the cutting process. Machinability is often measured by the surface roughness, the allowable cutting speed and the abration of tool. This is not only related to the chemical composition and mechanical properties itself, but also related to the cutting process (like tool geometry, durability, cutting speed and feed quantity, etc.). Although there are many factors affecting the cutting performance, but the most important is the nature of the metal itself, especially the hardness, when the metal hardness of HB150~230, the best cutting performance.

  1. Weldability

Weldability refers to the adaptability of metal materials to welding processing, that’s the performance of obtaining qualified welded joints under specified welding conditions. It related to metal welding defect sensitivity and the performance welding joints to meet the use requirements under a certain welding process conditions.

  1. Heat treatment

Metal heat treatment is to heat the metal workpiece to the appropriate temperature for a certain time and then cooling at different speeds in different media, by changing the surface or internal microstructure of metal materials to control its performance of a process. Heat treatment mainly includes annealing, normalizing, quenching, tempering, tempering, chemical heat treatment, solid solution treatment, precipitation hardening (precipitation strengthening), aging treatment and so on. The heat treatment performance of steel mainly considers its hardenability(quenching can get higher hardness and smooth surface), containing manganese, chromium, nickel and other elements of alloy steel hardenability is better while carbon steel hardenability is poor. The heat treatment requirement of aluminum alloy is strict and only several kinds of Copper alloy can be strengthened by melting heat treatment.

 

What’s the spherical titanium powder industrial application?

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Spherical titanium powders particular are silver-gray irregular metal powder in morphology and can also be magnetically screened or acid washed to remove any ferromagnetic contamination. These powders are characterized by its high strength, high corrosion resistance, widely used in a wide range of today’s most demanding markets such as aviation industry, aerospace industry, medical industry and ordinary industry. Do you know the industrial application of spherical titanium powder? Follow us to continue to read on!

 

Powder Metallurgy

Powder metallurgy, as a kind of advanced technology of material processing, plays an important role in the field of titanium industry. The titanium powder metallurgy molding technology can be used to directly produce finished products or parts close to the size of finished products. This technology has the characteristics of reducing the consumption of raw materials, shortening the processing cycle, and saving 20% ~ 50% of the cost compared with the conventional process, especially in the automobile industry, near net forming technology of titanium powder metallurgy is important. In Japan, automobile powder metallurgy parts are widely used in engines and transmissions the box, including connecting rod, seat, valve, pulley, synchronizer gear hub, synchronous ring and other complex and demanding key parts. Metal powder injection molding (MIM) is a rapidly developed near net powder metallurgy technology, which can produce high quality, high precision and complex parts. At present more and more titanium injection molding products have been developed and applied.

Laser Molding

Laser forming combines laser, CAD/CAM technology and powder materials, can be used directly with spherical titanium powder to produce complex final parts which performance between casting and forging pieces, and cost reduction of 15% to 30%, delivery time shortened by 50% to 75%. Re-searchers at aeromet company in American use a laser molding process to process titanium alloy powder into precision parts, which reduces the waste by 80% compared with the traditional casting process, and greatly shortens the production time. In addition, the use of laser molding technology to prepare titanium porous and dense biomedical materials can save time and materials, achieve customized processing, to meet the personalized needs of medical materials.

Thermal Spraying

Thermal spraying titanium layer technology is developed with the appearance of modern aviation and aerospace technology. At present, the commonly used methods of making titanium and titanium alloy coating include arc spraying, low-pressure plasma spraying, cold spraying, temperature spraying and other surface spraying technologies. Thermal spraying is mainly used to repair the workpiece defect parts, as well as high-temperature resistance, wear resistance and other parts of the protection and functional coating manufacturing. This process can reduce the production cost and make the surface of the workpiece obtain the required size and special properties, which not only solves the problem of titanium processing difficulties but also reduces the production cost by saving materials.

 

Titanium has good electrical conductivity and corrosion resistance, titanium coating made of titanium powder has become a research hotspot in the coating industry. Titanium coating is widely used in food storage, petrochemical industry, ocean ships and other fields. The titanium coating mixed with nano – spherical titanium powder has excellent antistatic and antifouling properties. With the development of the application of spherical titanium powders, the demand for high purity, low cost and stable spherical titanium powders increase rapidly.

 

Processing Technology of GH3600 Alloy Steel Pipe

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GH3600(ASTM/ASME UNS N06600) is a high temperature and oxidation resistant nickel based alloy. It is widely used in petrochemical processing, nuclear power and aerospace industry. Aerospace GH3600 alloy tubes are mainly used for hydrogen and oxygen rocket engines of upper stage power devices of carrier rockets. At present, the United States is planning on the basis of hydrogen and oxygen rocket engine’s orbit transfer vehicle and single stage to orbit of the space shuttle, developed for landing on the moon of Saturn rocket, second, third class, the J – 2 lox/lh2 engine developed by France and other European countries Ariane rocket and Japan is developing, the carrier rocket level above all use hydrogen engine as their main power devices.

At present, forging and drilling or cross-rolling piercing technology is mainly used in the billet of Nickel-based pipes in China. Due to the limitation of forging ratio, the uneven grain size of tube billet and a waste of raw materials in the drilling process, forging and drilling process are generally only suitable for thick wall, a short length and difficult to prepare hot-processed tube billet. Although the cross-rolling piercing process has high efficiency and high yield, due to its own structural constraints, whether it is two-roll or three-roll cross-rolling piercing, the material is not subjected to three-dimensional compressive stress, which results in circular micro-cracks on the cross-section of the billet and affects the possibility of subsequent processing. GH3600 alloy pipes for aerospace use are extruded to avoid the above situation.  Operations details including:

The equipment of extrusion blank is 2.5MN horizontal extrusion press. The blank size is 125 mm x 37 mm x L. The extrusion force is 1.6-1.8MN. The extrusion parameters are heating temperature 960-980 C, holding time 90-120 min, preheating temperature 500-600 C, extrusion speed 80-100mm?S-1 and extrusion ratio 10.1.

Two different rate distribution methods were used for cold rolling of finished products. The effects of different cold rolling processes on mechanical properties of products were compared for different cold rolling processes from 15mm *1.75mm to 5.8mm *0.4mm. The annealing pass processing rate of process 1 ranges from 68.9% to 70%, and that of process 2 ranges from 51.5% to 56.9%. The results are as follows:

  • GH3600 alloy tube can be extruded to refine the microstructure obviously and improve the microstructure uniformity.
  • The cold processing rate of finished products is controlled within the range of 51% to 57%, which can not only obtain good finished product structure, but also improve the room temperature elongation and yield strength at high temperature, and obtain better performance of finished products. Elongation of 39.8% at room temperature and 900 ℃ under the Rm of 124 Mpa, Rp0.2 is 82 Mpa.

The key point of tube extrusion is the matching of extrusion ratio and extrusion temperature. High extrusion ratio is beneficial to obtain the more uniform structure, but it will increase the extrusion pressure at the same time. While high extrusion temperature reduces the extrusion pressure, it also reduces the surface quality and dimensional accuracy of the product. At the same time, the sheath and lubrication mode of the high temperature alloy extrusion also play a crucial role.