The material of the repaired cast iron valve is HT200 and QT450, and the experimental pressure is 2

The difficulty is that there are two different strengths and different forms of cast iron materials, and then the engineering pressure of 24 kg is indeed very demanding, generally gray iron is to use 308 electrodes, ductile iron with 408 electrodes, the two can be welded together with the process of hot welding 308 electrodes are used, but from the simplicity of the process, it is best to use the cold welding process, then return to the choice of both cold welding and welding rods suitable for two different cast iron welding, it is best to choose wewelding777 cast iron electrodes, This is the most widely used for cast iron overhaul and maintenance, and the crack resistance is very excellent to ensure that there will be no cracks during the welding process, so as to ensure that the maximum pressure will be withheld after welding.

Characteristics of WeWelding 777 Special Cast Iron Electrodes.

Wewelding777 has a special coating effect, the welding process can produce a soft arc similar to the pulse, the thermal impact on all kinds of cast iron base metal is very small, the special pulse arc can remove all kinds of impurities on the surface of the cast iron, and even for the welding of oil stains and long-term oil immersion castings also has good permeability without porosity or inclusion, and the hardness of the heat affected zone will not become very high, and the forming weld welded by the cold welding process has very excellent crack resistance, Able to cope with all kinds of harsh base metal environments.

Application of WeWelding 777 Cast Iron Electrode.

It is suitable for all-round cold welding process welding, can weld almost all cast iron base metals, and is easy to realize the dissimilar welding of cast iron and carbon steel, solve the defects such as matrix fracture, crack, wear, and hole filling, and can be machined after welding, and is used in various types of iron castings such as engine housings, cylinder heads, machine bases, and gear teeth of casting gears on many occasions.

Technical parameters of WEwelding777 cast iron electrode WE777 special cast iron electrode.

Tensile Strength: 70,000 psi (482 Nv2 mm²) Yield Strength: Typically 62,000 (427 Nn mm²) Hardness (Hb): 185HB

Color matching with the base metal: similar Power supply selection: AC and DC dual-use, DC reverse connection when DC.

Composition of WeWelding 777 Cast Iron Electrodes.

Composition: Nickel, Iron & Oxide, Silicon & Oxide, Rest.

Proportion: (%60%-100% 2%-10% unknown.

Diameter (mm).

Current (amps) 60-100 85-110 90-140 Package Weight (lbs) 2 2 2

Here are some of the well-known brands recognized in the valve industry, which are widely recognized and have a high reputation. While rankings may vary depending on time and market conditions, the following brands are generally considered to be among the top brands in the valve industry:

The following influential first-line brands of water system valves and industrial valves can be used as a reference, but for reference only: Suzhou Neway Valve, Shanghai Guanlong Valve, Shanghai Qizhong Valve, Sanhua, Su Yan, Shentong, Su Valve, Nanfang, Jiang.

First, the word Yao. The above manufacturers are only estimates and references, and the specific situation may vary or fluctuate at any time due to changes in a series of factors such as changes in the market, the size of the competition pattern, and the stability of product quality. As an indispensable key device in industrial production and civil facilities, the quality and reputation of the valve brand directly affect the satisfaction and trust of users.

These brands are known in the valve industry for their innovative technology, high-quality products and reliability. It is important to note that the market and industry are evolving rapidly, and different rankings may vary depending on time and region. For the most up-to-date ranking information, it is recommended to refer to industry reports, professional organizations or market research data for more detailed and accurate information.

Grade HT200

Category: Grey cast iron.

Cast iron grade Higher strength cast iron, the matrix is pearlite, the strength, wear resistance, heat resistance are good, and the vibration damping is also good; The casting performance is good, and manual failure treatment is required.

Working conditions 1Parts subjected to greater stress (bending stress

2.The pressure per unit area between the friction surfaces is greater than 10t for large castings working under wear

3.A certain degree of airtightness or resistance to weakly corrosive media is required.

Application Example 1The more important castings in general machinery manufacturing, such as: cylinders, gears, machine bases, metal cutting machine tool beds and bed tops, etc.

2.Cylinder blocks, cylinder heads, pistons, brake wheels, coupling discs for automobiles and tractors, and piston rings for gasoline and diesel engines.

3.Inspection co-construction with measuring planes, such as: marking plates, V-shaped iron, flat rulers, level frames, etc.

4.Hydraulic cylinders, pump bodies, valve bodies, and pump casings and vessels that require a certain degree of corrosion resistance are required to withstand the following medium pressures.

5.Pulleys with a circumferential speed of 12 20 ms and other parts that meet the listed conditions.

6.Parts that need to be surface hardened.

Grade QT450-10

Category: Ductile iron.

Basal tissue ferrite 80%.

The main characteristics are good weldability and machinability, the plasticity is slightly lower than HT400-18, and the strength and small energy impact toughness are better than HT400-18

Application examples Agricultural machinery: used to make oil pump gears in internal combustion engines, medium-temperature cylinder partitions for steam turbines, valve bodies for water turbines, rolling stock bearings, and connecting plates and bowls for transmission lines.

HT200 is gray cast iron, QT450-10 is ductile iron, and the density and tensile strength of both are different.

QT450-10 is a high-strength cast iron.

material, the name stands for ductile iron.

Ductile iron is spheroidized and inoculated to obtain ductile iron, which effectively improves the mechanical properties of cast iron, especially plasticity and toughness, so as to obtain higher strength than carbon steel. It has been successfully applied to the casting of parts with complex stress, high strength, high toughness and wear resistance.

In addition to iron, other chemical components of ductile iron are: carbon content, silicon content, total amount of manganese, phosphorus, sulfur and an appropriate amount of rare earth, magnesium and other spheroidizing elements.

Name Ductile Iron.

Serial number = 7 grade = QT450-10

Material status = single cast test block.

b\mpa=≥450

Hardness HB=160 210

Specimen blank size mm=

Characteristics and applications = It has good plasticity and toughness, weldability and machinability, and is used in the manufacture of agricultural machinery, ploughshares, harvesters, lawn mowers, etc.; Wheel hubs, drive axle bodies, clutch housings, differential housings, etc. for automobiles and tractors; Valve body, bonnet, compressor cylinder, railway rail pad, motor housing, gearbox, etc.

QT450-10 is ductile iron, which is ferritic ductile iron with high toughness and plasticity. At low temperature, the toughness changes to brittleness, but the low temperature impact value is higher, and there is a certain resistance to acute temperature change and corrosion resistance. It has a wide range of uses, and is used in agricultural machinery for ploughshares, plough columns, differential shells, etc.; It is used as a valve body, high and low pressure cylinder in general machinery, etc.; It can also be used for steel caps for transmission lines, etc.

Chemical composition. Carbon C:

Silicon si:manganese mn:

Sulfur s: phosphorus p:

Magnesium mg: rare earth re:

Carbon equivalent: mechanical properties.

Tensile strength b (mpa): 450

Conditional yield strength mpa): 310

Elongation δ 10

Hardness: 160 210HB

This material is the most commonly used ductile iron and is used in a wide range of applications; There are a lot of spot spots here in Ningbo; *1*5*8*8*8*

HT200 is a grade of gray cast iron, which belongs to ferrous metals, and the carbon content is 200MPa for the minimum tensile strength of the gray cast iron HT200 gauge diameter 30mm specimen

Grades, properties and uses of commonly used engineering materials.

1) Carbon steel

The carbon content is less, manganese and silicon are beneficial elements, which have a certain strengthening effect on steel; Sulfur and phosphorus are harmful, increasing the hot and cold brittleness of steel.

Carbon Structural Steel Q Yield Point Quality Grade (ABCD) Deoxidation Method; High-quality carbon structural steel, two digits indicate the average carbon content of 10,000 fractions, and high MN content should be injected with MN; Carbon tool steels are added with "carbon" or t as a thousandth of the average carbon content.

2) Alloy steel

Commonly used alloying elements include silicon, manganese, nickel, chromium, copper, vanadium, titanium, rare earth elements, etc. Ordinary low-alloy structural steel, carburized steel, quenched and tempered steel, spring steel, rolling bearing steel.

3) Cast iron

Iron-carbon alloys with greater carbon content have worse mechanical properties than steel and cannot be forged. However, it has the characteristics of excellent castability, shock absorption, wear resistance, etc., coupled with low cost, simple production equipment and technology, accounting for 45 90 of the total weight of the machine; Grey cast iron HT200 watch.

Hello! Gate valves are made of materials of various properties, including gray cast iron, cast iron, and stainless steel. HT stands for: Grey cast iron. 200 represents: the main connection and dimensions of the gate valve.

QT450-10 is ductile iron with a tensile strength value of 450MPa and an elongation value of 10.

Ductile iron is carbon in the form of spherical graphite, its mechanical properties are far better than gray iron and close to steel, it has excellent casting, cutting and wear resistance, has a certain elasticity, widely used in the manufacture of crankshafts, gears, pistons and other advanced castings and a variety of mechanical parts.

HT200 is a grade of gray cast iron, and the minimum tensile strength of the gray cast iron HT200 table 30 specimen is 200MPa

HT200 is the grade of gray cast iron, HT stands for gray cast iron, HT is the abbreviation of gray cast iron Chinese pinyin, and the minimum tensile strength of the sample in Table 30 of gray cast iron HT200 is 200MPa

HT200 scope of application.

The tensile strength and plasticity are low, but the casting performance and shock absorption performance are good, and they are mainly used to cast pressure and vibration parts such as automobile engine cylinders, cylinder liners, and lathe beds.

HT200 Chemical Composition:

pσb ≥200mpa

The common denominator is:

1. All are gray cast iron, the main components are iron, carbon, silicon, manganese, sulfur and phosphorus, which is the most widely used cast iron, and its output accounts for more than 80% of the total output of cast iron.

2. The metallographic matrix structure is the same, which is ferrite + pearlite.

3. All of them have good casting performance, good vibration damping, good wear resistance, good cutting performance, and low notch sensitivity.

Differences: 1. QT500 is ductile iron, HT300 and HT200 are gray cast iron.

2. The metallographic structure of QT500 is ferrite + spherical graphite + pearlite; The metallographic structure of HT300 and HT200 is ferrite + flake graphite + pearlite.

3. QT500 tensile strength b (MPa): 500;HT300500 Tensile Strength B (MPa): 300;HT200 Tensile Strength B (MPa): 200

4. When QT500 is at low temperature, the toughness changes to brittleness, but the low temperature impact value is high, and it has a certain temperature resistance and corrosion resistance.

It is widely used in oil pump gears of internal combustion engines, medium temperature cylinder separators of steam turbines, valve bodies of water turbines, bearings of railway rolling stock, transmission shafts of machine seat frames, etc.

HT300 has high strength and good wear resistance, but it has a large tendency to white mouth and poor casting performance, so it needs to be manually aged.

It is suitable for the manufacture of castings that are subjected to high exaggerated bending stress and require high air tightness, such as heavy machine tool beds, gears, cams, large engine crankshafts and cylinder blocks, high-pressure cylinders, rolling bases, etc.

HT200 has low tensile strength and plasticity, but good casting performance and shock absorption.

It is mainly suitable for casting automobile engine cylinders, cylinder liners, lathe beds and other stress-bearing and vibration-bearing parts.

QT500 is ductile iron with a tensile strength of 500MPa; HT500 and HT200 are gray cast iron, with tensile strength of 500MPa and 200MPa respectively.

What cast iron grades have in common is that they are graded by mechanical properties (tensile strength). For example, the grade HT300 means that it is gray cast iron, and the tensile strength is not less than 300MPa.

But there is a difference between them: because the plasticity of gray cast iron is very small, the grade only indicates the tensile strength; Other cast iron grades (such as ductile iron, malleable cast iron) not only indicate strength, but also indicate plasticity (elongation) indicators, such as grade QT500-7, which means that it is ductile iron, and its tensile strength is not less than 500MPa, and the elongation is not less than 7%.

All are gray cast iron, QT500 is ductile cast iron, HT300 is inoculated cast iron, HT200 is ordinary gray cast iron.

Commonly used materials for valves.

1. Gray cast iron: Gray cast iron is suitable for water, steam, air, gas and oil with a nominal pressure of pn and a temperature of 10 200. The commonly used grades of gray cast iron are: HT200, HT250, HT300, HT350.

2. Malleable cast iron: suitable for water, steam, air and oil medium with nominal pressure pn and temperature of 30 300, commonly used grades are: KTH300-06, KTH330-08, KTH350-10.

3. Ductile iron: suitable for PN, water, steam, air and oil at a temperature of 30 350. Commonly used grades are: QT400-15, QT450-10, QT500-7.

In view of the current domestic technology level, the factories are uneven, and it is often not easy for users to inspect. As a rule of thumb, it is recommended that the valve is still made of steel for safety.

4. Acid-resistant high silicon ductile iron: suitable for corrosive media with nominal pressure pn and temperature lower than 120.

5. Carbon steel: suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with nominal pressure pn and temperature of 30 425. Commonly used grades are WC1, WCB, ZG25 and high-quality steel and low-alloy structural steel 16Mn.

6. Copper alloy: suitable for PN water, seawater, oxygen, air, oil and other media, as well as steam medium with a temperature of 40 250, the commonly used grades are ZGNSn10ZN2 (tin bronze), H62, HPB59-1 (brass), QAZ19-2, QA19-4 (aluminum bronze).

7. High-temperature copper: suitable for steam and petroleum products with nominal pressure PN temperature 570. Commonly used grades are ZGCR5MO, ZG15GR1MO1V, 12CRMOV, WC6, WC9 and other grades.

The specific selection must be in accordance with the provisions of the valve pressure and temperature specifications.

8. Low-temperature steel: suitable for nominal pressure PN, temperature -196 ethylene, propylene, liquid natural gas, liquid nitrogen and other media, commonly used grades) ZG1Cr18Ni Cr18Ni9, 1Cr18Ni9Ti, ZG0Cr18Ni9

9. Stainless acid-resistant steel: suitable for nominal pressure PN, temperature 200 nitric acid, acetic acid and other media, commonly used grades are ZG0CR18NI9TI, ZG0CR18NI10 "Nitric Acid Resistance", ZG0CR18NI12MO2TI, ZG1CR18NI12MO2TI "Acid and Urea Resistance".

Ten: In addition to the above-mentioned metal valves, there are also plastic valves and ceramic valves for special applications.