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what is Spur gear?

October 21, 2020

Spur gear is a classification of gears. According to the relative position and tooth direction of a pair of gear axes (whether the two circles are parallel), it can be divided into plane gear rotation and space gear rotation; according to

Spur gear

the working conditions of the gears, it can be divided into open transmission and closed transmission; according to gear teeth or tooth profile. The gear is divided into straight teeth, helical teeth, herringbone teeth, or straight teeth, curved teeth, as per the shapes.

The code name is 4 for valve drive mode. see details at: https://www.tanghaivalve.com/valve-model-establishment-and-meaning/

Unit One , valve type (code name):

butterfly valve	safety valve	Diaph-ragm valve	ball valve	gate valve	check valve	plug valve	Pressure reducing valve	globe valve	filter	Disch-arge valve
D	A	G	Q	Z	H	X	Y	J	GL	FL

Unit two, valve drive mode (code name):

drive mode	Electro-magne-tism	Electro-magnetic hydraulic	Electro-hydraulic	tur-bine	Spur gear	Bevel gear	pneu-matic	Hydr-aulic	Gas-hydr-aulic	elec-tric	han-dle	Hand-wheel
code	0	1	2	3	4	5	6	7	8	9

Unit three, valve connection method (code name):

connection	internal thread	external thread	two different connections	flange	welding	wafer	clamp	ferrule
code	1	2	3	4	6	7	8	9

Classification
Straight cylinder/spur gear
Meshing mode: external meshing, internal meshing, gear and rack
Basic characteristics: The tooth profile contact line is a straight line parallel to the axis. A pair of tooth profiles enter or exit the mesh at the same time along the tooth width, which is likely to cause shock and noise, and the transmission stability is poor.

Straight bevel gear:
Pitch cone, index cone, tooth tip cone, tooth root cone, base cone; used for transmission between intersecting two shafts, the gear teeth are distributed along the cone surface, and the size of the starting gear teeth gradually decreases toward the cone tip.
In order to enable the gear to rotate in both directions, the tooth profile on both sides of the gear tooth is composed of involute surfaces with the same shape and opposite directions. The names and symbols of each part are: addendum circle, tooth root circle, tooth Slot, tooth thickness, tooth pitch, modulus m, index circle d, tooth top and tooth root, top clearance

Gears are divided into spur gears, helical gears, herringbone gears, and curved gears according to the shape of the tooth line. The spur gears are gears whose teeth are parallel to the axis.

Surveying method:
The spur gear is one of the most common gears in actual production and use. Damage is inevitable during use. Therefore, it is necessary to make a new gear that is the same as the original one. For various reasons, the customer cannot provide the required spur gear. In order to ensure the normal use of the processed products, the gear drawings need to be accurately surveyed and mapped. The surveying and mapping work is a complicated task. Since there are few data on the surveying and mapping of spur gears, it is naturally inconvenient to consult. The work experience and methods of surveying and mapping spur gears in several actual production are summarized by the operation. The introduction is as follows:

First of all, although there are many parameters and dimensions of spur gears, the standard system of various gears stipulates the modulus or diameter pitch as the calculation basis for other parameters and the dimensions of each part. Therefore, the surveying and mapping work should make every effort to accurately determine the size of the modulus or the diametral pitch. At the same time, the pressure angle is the basic parameter to determine the tooth profile, and accurate determination is equally important.

Secondly, we need to understand the usage and production country of the gear being surveyed, so that we can estimate the standard system adopted by this gear. Generally speaking, China, Japan, Germany, France, Czech Republic, and the former Soviet Union all adopt the modular system. You can also observe the tooth profile of the gear. If the tooth profile is curved and the bottom of the tooth groove is narrow and arc-shaped, it can be preliminarily judged as a modular system. The standard pressure angle is mostly 20 degrees; the United States and the United Kingdom adopt diameter control, and the standard pressure angles are 14.5 degrees and 20 degrees. Observing that the tooth profile is relatively straight and the bottom of the tooth groove is wider and the arc is small, it can be preliminarily judged as the diameter control. The pressure angle is 14.5 degrees. You can also use gear hobs or standard rack samples to determine which pressure angle is. If you know the above conditions, you can actually survey and map:

(1) Method of measuring the diameter of the addendum circle Dm

First count the number of teeth Z of the gear, and then use a vernier caliper to measure the diameter Dm of the addendum circle. If it is determined that the gear is a modular standard tooth profile, its modulus:

m = Dm/Z+2

If it is determined that the gear is a standard tooth profile with diameter control, its diameter pitch is

Dp=25.4*(Z+2)/ Dm

However, it should be noted that if the number of teeth of the gear is even, it can be directly measured; if the number of teeth is odd, the measured size is not the addendum diameter Dm, but two teeth from the tip of a tooth to the opposite tooth space. The distance D between the intersection of the face and the addendum circle is smaller than the diameter of the addendum circle. Usually, Dm is multiplied by the correction coefficient k to get the addendum circle diameter D, namely:

Dm=k*D

In practice, the diameter of the addendum circle calculated by the odd-numbered gear addendum circle diameter correction coefficient k (Table 1) is generally small. The diameter of the addendum circle calculated using the corrected correction coefficient k (Table 2) according to the above formula is more Close to the real value, Table 2 is more accurate than Table 1, and the number of teeth is finer, for reference.

fig.1-Odd tooth gear Addendum circle diameter Correction coefficient K

fig.2-Correction coefficient after correction k

If the odd-numbered gear is not a gear shaft but has a hole, you can also measure the inner hole diameter d and the distance H from the hole wall to the tooth tip, and get the tooth tip circle diameter by the following formula:

Dm=2*H+d

(2) Method of measuring the height of the tooth

When the gear is inconvenient to measure the diameter of the addendum circle due to large modulus, tooth punching, etc., the full height h of the tooth can be measured to determine the modulus or diametral pitch. The total tooth height h can be measured with the depth tail needle of a vernier caliper, and other depth measuring tools are also available, depending on the site conditions; if the gear has a hole, the tooth total height h can be obtained indirectly by measuring the inner hole wall to the tooth tip and tooth root The subtraction of the distance is the total tooth height h, and the modulus or diametral pitch is calculated as follows:

m=h/2f+c Dp=25.4*(2f+c)/h

f:: Addendum height coefficient c: Radial clearance coefficient

f, c can be found by checking the gear standard system parameter table[3]

(3) Method of measuring center distance A

When the gear teeth are sharp, worn, or rolled, the above two methods cannot be measured. At this time, we can ask the customer to provide the center distance A of the two paired gears and the number of teeth of the two gears. These are easy to do. Calculate the modulus or diametral pitch as follows:

m=2*A/Z1+Z2 Dp=25.4*(Z1+Z2)/2*A

Z1, Z2: Number of teeth of matched gear

The modulus or diametral pitch calculated by any one of the three methods is compared with the standard modulus or diametral pitch series, and the closest one is fine.

The above are the commonly used methods for surveying and mapping spur gears in actual work. It is best to use two methods to check each other, so that the determined modulus or diameter section is more accurate, and the surveying and mapping work is basically completed. Special attention: The above surveying and mapping methods are carried out under the condition that we can pre-determine or investigate the standard system adopted by the gear. If the gear’s “all conditions are unknown”, the above methods can only be referred to, and then comprehensively judged by other means. It is believed that the above several surveying methods will be helpful to colleagues who have just joined the work soon or for the first time to survey and map spur gears. It is worth referring to.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Check valve model designation method

October 21, 2020

Check valve model representation method Check model preparation instructions
Check valve (one-way valve) model compilation instructions:
Check valve (one-way valve) is also called check valve or reverse flow valve. It is an automatic valve that opens or

tilting disc swing check valve (3)

closes the disc through the flow of the medium itself, and can only flow in one direction and cannot be reversed. It is mainly used for In the piping system, prevent the medium from flowing back or flowing backward. Check valves have a wide range of uses and types. Different types of check valves are also different in different pipelines, operating conditions and connection methods. In order to avoid selecting the wrong model when purchasing a valve, and causing unnecessary working conditions during the application process due to improper model selection, users should have more understanding and awareness of the following check valve model preparation instructions. Check valve (check valve) model compilation instructions are mainly to make a detailed analysis of the additional conditions, connection methods, structural forms, sealing materials, pressure ratings and shell materials of the check valve. Hope it helps you when you buy check valves.

Check valve (check valve) model representation method:
Additional code of check valve: HH: micro-resistance slow-closing check valve, BH: heat preservation check valve, HQ: rolling ball check valve;
Check valve code: H stands for check valve;
Connection code: 4 flanges, 6 welding, 7 wafer;
Code of structural form: 1: lift type, 2: vertical type, 4: swing type, 6: double flap type, 8: butterfly type;
Sealing material code: B: babbitt alloy, F: fluorine plastic, H: stainless steel, M: Monel alloy, X: rubber, Y: cemented carbide, W: direct processing;
Pressure grade code: 16=16 kg pressure, PN1.6-25mpa, pound grade 150LB-2500LB, Japanese grade 5K-63K;
Shell material code: Q: ductile iron, C: carbon steel, P:304, R:316, A: titanium alloy, I: chromium molybdenum steel;

Example of model preparation of check valve (check valve):
H44H-16C swing flange check valve
H: indicates the check valve;
4: Flange link;
4: Swing type;
H: The sealing material is stainless steel;
16: The pressure is 16 kg (1.6mpa)
C: The valve body is carbon steel.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Valve model establishment and meaning (2)

October 20, 2020

In the previous article, we have introduced the establishment of code number of the valve model in China. However, there are more and more types of valves and materials, and the compilation of valve models is becoming more and

U-type flange butterfly valve, ductile iron, DI, center line,

more complicated. Although China has a unified standard for valve model formulation, it is gradually unable to meet the needs of the development of the valve industry. At present, valve manufacturers generally adopt a unified numbering method; each manufacturer that cannot use a unified numbering method can develop its own numbering method according to its own situation.
Here we mainly introduce the method of Chinese valve numbering, and we will give examples.
For example, the Z543H-16C bevel gear drive, flange connection, flat gate valve, nominal pressure 1.6MPA, valve body material is carbon steel.
Please refer to the previous article for the specific number code: Valve model establishment and meaning

Unit One , valve type (code name):

butterfly valve	safety valve	Diaph-ragm valve	ball valve	gate valve	check valve	plug valve	Pressure reducing valve	globe valve	filter	Disch-arge valve
D	A	G	Q	Z	H	X	Y	J	GL	FL

Unit two, valve drive mode (code name):

drive mode	Electro-magne-tism	Electro-magnetic hydraulic	Electro-hydraulic	tur-bine	Spur gear	Bevel gear	pneu-matic	Hydr-aulic	Gas-hydr-aulic	elec-tric	han-dle	Hand-wheel
code	0	1	2	3	4	5	6	7	8	9

Unit three, valve connection method (code name):

connection	internal thread	external thread	two different connections	flange	welding	wafer	clamp	ferrule
code	1	2	3	4	6	7	8	9

Unit Four, valve structure (code name):

Butterfly valve structure (code name):

butterfly structure		butterfly code	butterfly structure		butterfly code
sealed	singl eccentric	0	unsealed	single eccentric	5
	center vertical plate	1		center vertical plate	6
	double eccentric	2		double eccentric	7
	triple eccentric	3		triple eccentric	8
	linkage mechanism	4		linkage mechanism	9

Another example: D341X-16Q: Double flange butterfly valve, worm gear, soft centerline seal, nominal pressure 1.6Mpa, valve body material is ductile iron
Another example: D371X-10C: Wafer butterfly valve, turbo drive, soft centerline seal, nominal pressure 1.0MPA, and the valve body material is cast steel.
The valve number has 7 digits, and each position has a different code, so there are many changes in the valve, and the price will not be too uniform. And these 7 codes can’t represent the details of all materials. In addition to these 7 codes, there are many components that will greatly affect the use of the valve and the cost and price of the valve, such as the material of the valve plate, the material of the valve shaft, and the length of the valve structure.
Therefore, in the valve industry, there are many special products that need to be customized, and individual inquiries need to be checked separately, and special circumstances require special treatment.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Description of lining material for rubber lining valve

October 12, 2020

Overview of rubber-lined valves:
Rubber-lined valve (lined valve) is a valve suitable for pipelines containing corrosive media and high sealing requirements. Generally, the applicable temperature should not be too high, and it is not suitable for use in media

double-wing-check-valve-3

containing particles to avoid scratches. Scratches or scratches the sealing surface, causing the valve to leak. Rubber-lined valve is a kind of plastic product produced by the chemical reaction of many chemical substances. The main materials are: soft rubber, hard rubber, butyl rubber, natural rubber, EPDM rubber, fluorine rubber, Lining silicone rubber, etc., its main working purposes are: diversion, adjustment, throttling, cut-off, check, diversion, overflow, etc., which means that as long as it is a general fluid valve, it can be controlled.

The main lining materials of rubber-lined valves:
【Neoprene, Code CR】
Applicable temperature: -10℃~105℃ Animal oil, vegetable oil, inorganic lubricating oil and corrosive slurries with a wide range of pH value, good wear resistance.
【Soft Rubber Code BR】
Applicable temperature: -10℃~85℃
Applicable medium: good wear resistance. Mainly used for sulfuric acid below 50%, sodium hydroxide, potassium hydroxide, neutral salt bath solution and ammonia solution, cement, clay, cinder ash, granular fertilizer and solid fluids with strong abrasiveness, and thick viscous liquids of various concentrations Wait. _
【Butyl Rubber Code IIR】 Applicable temperature: -10℃~120℃
Applicable medium: corrosion resistance and wear resistance. Can withstand most organic acids, alkalis and hydroxide compounds, inorganic salts and inorganic acid element gases, alcohols, aldehydes, ethers, ketones, esters, etc., ≤30% sulfuric acid, phosphoric acid, hydrofluoric acid, animal oil , Vegetable oil, caustic alkali and a variety of lipids. _
【Hard Rubber Code NR】 Applicable temperature: -10℃~85℃
Applicable medium: hydrochloric acid, fluorosilicic acid, formic acid and phenolic acid, hydrochloric acid, 30% sulfuric acid, 50% hydrofluoric acid, except strong oxidants (such as organic solvents such as acid, chromic acid, concentrated sulfuric acid and hydrogen peroxide) Acid, 80% phosphoric acid, alkali, salt, metal plating solution, sodium hydroxide, potassium hydroxide, neutral salt solution, 10% sodium hypochlorite, wet chlorine, ammonia, most alcohols, organic acids and aldehydes, etc.

Conversion of valve nominal diameter and inch | comparison table

October 12, 2020

Valve nominal diameter|valve nominal diameter
Definition of valve nominal diameter:

ductile iron, DI, butterfly valve, manufacturer, center line, TH valve

Nominal diameter (or nominal diameter), also known as average outer diameter, refers to the size of all piping accessories in the piping system. The nominal diameter is a convenient round integer for reference. The nominal diameter of the valve is marked with a number followed by the letter DN. DN represents the internal diameter of the pipe in millimeters. For example, DN50 is 50 millimeters. The American standard valve is usually expressed in inches (“), and the fractional valve is to express the internal diameter of the pipe in inches. The conversion formula is 1”=25.4mm, such as 8” is equivalent to the domestic DN200mm.

Valve nominal diameter comparison table:
The nominal diameter of the valve (NPS-NOMINAL PIPE SIZE) is not necessarily the same as the diameter of the flow channel. For the selection of its size, the required Cv value is calculated from the conditions of the conveying fluid, and then the Cv value (refer to the manufacturer’s catalog) is used to select a suitable valve The nominal diameter (NPS) is the nominal inner diameter that characterizes the valve diameter. The national standard is expressed by DN and the unit is mm. The American standard is expressed in inches. The conversion relationship between inch NPS and metric DN is as follows:

No.	inch	DN/mm	No.	inch	DN/mm	No.	inch	DN/mm
1	1/8	4	17	10	250	33	42	1050
2	1/4	8	18	12	300	34	48	1200
3	3/8	10	19	14	350	35	54	1350
4	1/2	15	20	16	400	36	60	1500
5	3/4	20	21	18	450	37	64	1600
6	1	25	22	20	500	38	72	1800
7	11/4	32	23	22	550	39	80	2000
8	11/2	40	24	24	600	40	84	2100
9	2	50	25	26	650	41	88	2200
10	21/2	65	26	28	700	42	96	2400
11	3	80	27	30	750
12	31/2	90	28	32	800
13	4	100	29	34	850
14	5	125	30	36	900
15	6	150	31	38	950
16	8	200	32	40	1000

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Comparison table of valve diameter (DN) and pipe diameter

October 10, 2020

The size of the valve caliber has an inevitable relationship with the size of the pipeline. It is usually said that the pipe diameter (outer diameter) is matched with the valve. The valve diameter needs to be calculated according to the actual parameters. Generally speaking, the pipeline will be larger, and the valve actually needs to be smaller. It mainly depends on the flow rate to be controlled by the valve position, and the pipeline size only needs the flow capacity.
(1) Comparison table of pipe fitting size and valve diameter and inches:

Diameter/inch	DN (Norminal diameter) mm	pipe OD (mm)
1/4＂	8	13.7
3/8＂	10	17.14
1/2＂	15	21.3
3/4＂	20	26.7
1＂	25	33.4
1.2＂	32	42.2
1.5＂	40	48.3
2＂	50	60.3
2.5＂	65	73
3＂	80	88.9
4＂	100	114.3
5＂	125	141.3
6＂	150	168.3
8＂	200	219.1
10＂	250	273
12＂	300	323.8
14＂	350	355.6
16＂	400	406.4

(2) Valve diameter DN (nominal diameter) corresponds to the outer diameter of the pipe Ф (mm):

Norminal diameter/DN	pipe OD small	pipe OD big	Norminal diameter/DN	pipe OD small	pipe OD big
15	18	22	350	360	377
20	25	27	400	406	426
25	32	34	450	457	480
32	38	42	500	508	530
40	45	48	600	610	630
50	57	60	700	720
65	73	76	800	820
80	89	89	900	920
100	108	114	1000	1020
125	133	140	1200	1220
150	159	168	1400	1420
200	219	219	1600	1620
250	273	273	1800	1820
300	324	325	2000	2020

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Working principle diagram of swing check valve

October 9, 2020

Working principle diagram of swing check valve
Swing check valve, also known as check (flow) valve, is an automatic valve used on one-way flow pipelines to prevent the medium from flowing back. It depends on the pressure of the pipeline medium to open or close the valve. It can be divided into single valve type , Double valve type and multi valve type, are one of the more commonly used valves. Swing check valves are generally suitable for pipelines with relatively clean fluid media. They are not suitable for

swing-check-valve-working-principle-diagram

working conditions with high viscosity or solid particles. Otherwise, the check valve will be insensitive to opening and cannot achieve a complete seal. The answer is not reliable enough. The swing check valve only allows the medium to flow in one direction, which can effectively prevent the medium from flowing back to prevent accidents.

The working principle of the swing check valve:
The disc of the swing check valve and the rocker are connected together, and can rotate a certain angle around the pin shaft. When the pipeline fluid flows in the specified direction (from left to right), the inlet pressure of the disc is higher than the outlet pressure. At this time, the disc is pushed away from the valve seat and rotates around the pin to a certain position, and the valve is in the open state. When the pressure difference between the two sides of the valve flap decreases to a certain level, the valve flap falls and returns to the closed state. When the fluid flows from right to left, that is, reverse flow, the pressure on the right side of the valve disc is higher than the pressure on the left side, and the force generated by the pressure difference on both sides presses the valve disc on the valve seat, and the fluid cannot pass through, the medium Can not flow back; and the greater the fluid pressure, the tighter the sealing surface is, and the better the sealing effect. To

The installation position of the swing check valve is not restricted. It can be installed horizontally in the pipeline, or on a vertical or inclined pipeline, but if it is installed on a vertical pipeline, the flow direction of the medium should be from bottom to top.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

Working principle diagram of lift check valve

October 9, 2020

Lifting check valve structure:

Lifting check valve is a kind of valve that prevents pipeline media from flowing back, mainly composed of valve body, valve seat, valve flap, valve cover and other related parts. The lift check valve is equipped with a spring to ensure that the disc is always in a dynamic equilibrium state under the action of the spring. Regardless of the medium pressure at the inlet of the valve, the valve can maintain a balanced operation.

lift check valve Working principle diagram

The working principle of the lift check valve:

The lift check valve has a guide rod on the disc, which can move up and down freely in the guide hole of the valve cover. When the pipeline medium flows in in the specified direction (from left to right), and the pressure below the valve flap exceeds the pressure above it, push the valve flap to rise along the center line of the guide hole of the valve cover, and the valve will automatically open to allow the medium to flow; if the fluid flows from the right to the right Left flow, that is, when it flows backward, the pressure above the valve flap is greater than the pressure below it. The pressure difference between the upper and lower pressures and the weight of the valve flap press the valve flap on the valve seat, so that the medium cannot pass through, that is, the fluid cannot flow back; and pipeline fluid The greater the pressure, the tighter the sealing surface is, and the better the sealing effect.

The seat sealing surface of the lift check valve can be welded, or it can be made into a seat sealing ring and then expanded or threaded on the valve body; when the valve body is made of stainless steel, the sealing surface can also be on the valve body It is directly processed from above. The sealing surface of the disc can be directly processed on the disc, or can be processed after surfacing or welded on the disc with the inner and outer periphery of the sealing ring. The straight-through lift check valve can only be installed on the pipeline in a balanced way, and the center line of the valve flap is vertical to the horizontal plane, while the vertical lift check valve is not subject to this restriction.

What is butt welding? (9)- New technology of flash butt welding

September 29, 2020

New technology of flash butt welding
1) Program-controlled reduced-voltage flash butt welding is characterized by the use of higher secondary no-load voltage at the beginning of the flash to facilitate the initiation of the flash. When the end surface temperature rises, the low-voltage flash is used and maintained The flash speed remains unchanged to improve thermal efficiency.

flash butt welding-schematic diagram

When approaching the upsetting, increase the secondary voltage to make the flash stronger to increase the self-protection effect.
Program-controlled reduced-voltage flash butt welding is compared with preheated flash butt welding. It has the advantages of short welding time, low power required, and uniform heating.

2) Pulse flash butt welding. The characteristic of this welding method is that in the stroke of the moving clamp, a reciprocating vibration stroke is superimposed through the hydraulic vibration device, the amplitude is 0.25-1.2mm, and the frequency is 3-35Hz. Tune. Due to the vibration, the end face of the weldment is alternately short-circuited and pulled apart, resulting in a pulse flash.

Compared with ordinary flash butt welding, pulse flash butt welding has no spontaneous blasting of the lintel, the splashed particles are small and the flame is shallow, so the thermal efficiency can be more than doubled, and the upsetting allowance can be reduced to 2/3-1/ 2.

The above two methods are mainly to meet the needs of flash butt welding of large section workpieces.

3) Rectangular wave flash butt welding Compared with power frequency AC sine wave flash butt welding, this welding method can significantly improve the stability of the flash. Because the sine wave power supply will instantly interrupt the flash when the voltage is close to zero, and the rectangular wave can evenly produce the flash in the full cycle. It has nothing to do with the voltage phase.

The number of flashes per unit time of the rectangular wave power supply is 30% higher than that of power frequency AC, the sprayed metal particles are fine, the flame is shallow and the thermal efficiency is high. The rectangular wave frequency can be adjusted within the range of 30-180Hz. This method is mostly used for continuous flash butt welding of thin plates and aluminum alloy wheels.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

What is butt welding? (8)- typical workpieces

September 29, 2020

Butt welding of typical workpieces
1, butt welding of small section workpieces

wire with diameter d≤5mm is mostly used for resistance butt welding,
Small diameter wires, wires of different materials, and wires and stamping parts (such as resistors and diode end caps) can be welded by capacitive energy storage type, which is characterized by very hard welding conditions and

resistance butt welding-Schematic diagram

extremely narrow heating range, which greatly reduces The influence of the thermal and physical properties of the welded metal on the formation of the joint.
2. Butt welding of rods
is mostly used in the butt welding of steel bars in the construction industry, usually resistance butt welding is used for diameter d<10mm; continuous flash butt welding for d>10mm; preheated flash butt welding for d>30mm. When using a manual butt welding machine, because the power of the welding machine is small (usually not more than 50KVA), when d=15-20mm, it is generally necessary to use preheated flash butt welding.

Semi-circular or V-shaped clamp electrodes can be used for butt welding of rods. The latter can be used in various diameters, so it is widely used. The rods are of solid cross-section, with greater rigidity, and longer extension lengths can be used.
3, pipe butt welding
Pipe butt welding is widely used in boiler manufacturing, pipeline engineering and petroleum equipment manufacturing. Choose continuous or preheated flash butt welding according to the section and material of the pipe. The clamp electrode can be semicircular or V-shaped. Usually when the ratio of pipe diameter to wall thickness is greater than 10, a semicircle can be selected to prevent the pipe from being crushed. V-shape can be used when the ratio is less than 10. To prevent the tube from slipping in the clamp electrode, the clamp electrode should have an appropriate working length. When the pipe diameter is 20-50mm, the length of the workpiece is 2-2.5 times the pipe diameter; when the pipe diameter is 200-300mm, it is 1-1.5 times.

Because the tube has an expanded cross-section, the heat dissipation is faster, the liquid metal on the end surface is easy to cool, and it is difficult to extrude during upsetting. The area is scattered, and the self-protection effect is weakened during the flashing process. Therefore, when the process parameters are not selected properly, non-metallic inclusions will remain in the interface to form gray spot defects. Maintain stable flash, increase flash and upsetting speed, and adopt gas protection to reduce or eliminate gray spots.

After the pipe is welded, the internal and external burrs need to be removed to ensure that the external surface of the pipe is smooth and there is a certain channel aperture inside. Deburring requires special tools.

4, thin plate butt welding

flash butt welding-schematic diagram

Thin plate butt welding is widely used in the continuous production line of rolled steel plate in the metallurgical industry. The width of the plate is from 300 to 1500mm or more, and the thickness is from less than 1mm to more than ten mm. The materials include carbon steel, alloy steel and non-ferrous metals and their alloys. After the plate is butt welded, the joint will undergo rolling and produce great plastic deformation, so it must not only have a certain strength, but also a high plasticity. For steel plates with a thickness of less than 5mm, continuous flash butt welding is generally used, and a plane electrode is used for single-sided conduction. When the plate is thick, preheated flash butt welding is used for double-sided conduction to ensure uniform heating along the entire end surface.

When welding thin plates, due to the relatively large cross-section length and width, the area is scattered, the joint cools quickly, and the self-protection effect is weak during the flashing process. At the same time, the liquid lintel is small and the liquid metal layer on the end surface is thin. Prone to oxidation and solidification. Therefore, the flashing and upsetting speed must be increased. After welding, the burr must be removed with a burr cutting device while it is hot.
5. Butt welding of ring parts
When welding ring parts (such as wheel rims, chain rings, bearing rings, jet engine mounting edges, etc.), in addition to considering the general rules of butt welding process, attention should be paid to the influence of shunting and ring deformation elasticity. Due to the shunt, the required power should be increased by 15-50%. Although the diameter of the ring decreases, the cross section increases, and the material resistivity decreases.

When the ring parts are butt welded, the upsetting pressure must consider the influence of the deformation rebound force, but because the shunt has the effect of heating the ring back, the increase in the upsetting pressure is not large.

Bicycles, motorcycle rims, and automobile rims all use continuous flash butt welding, and the front mouth of the clamp electrode must match the cross-section of the workpiece. During upsetting, in order to prevent the rebound force from affecting the quality of the joint, or even pull the joint apart, it is necessary to extend the time of no current upsetting.

Chain links such as anchor chains and drive chains are mostly used in the manufacture of low-carbon steel and low-alloy steel. Resistance butt welding can be used when diameter d<20mm, and preheating flash butt welding can be used when d>20mm. The purpose of preheating is to heat the interface. Uniform, easy to produce certain plastic deformation during upsetting.
6, tool butt welding
When cutting tool butt welding, one of the current process methods used to manufacture blanks in tool manufacturing is mainly the butt welding of high-speed steel (W8Cr4V, W-9Cr4V2) and medium carbon steel. Tool butt welding has the following characteristics:

1) The thermal conductivity and resistivity of high-speed steel and medium-carbon steel are quite different. At room temperature, medium carbon steel λ=0.42W/(cm℃), ρ0=18-22uΩcm; high-speed steel λ=0.23W/(cm℃), ρ0=48Ωcm. In order to make the temperature distribution on both sides of the joint surface basically the same , The extension length of high speed steel should be 30-50% smaller than that of medium carbon steel. Under normal circumstances, the extension length of high-speed steel is (0.5-1.0)d. In order to prevent excessive heat dissipation, the extension length is not less than 10mm.

2) High-speed steel has a high tendency to quench, the hardness after welding will be greatly increased, and quenching cracks may occur. In order to prevent cracks, preheating flash butt welding can be used. During preheating, heat the metal in the range of 5-10mm near the interface to 1100-1200℃. After welding, it is annealed in an electric furnace at 600-700℃ for 30 minutes.

3) When high-speed steel is heated to a high temperature, it will produce grain growth or the formation of ledeburite eutectic on the semi-melted grain boundary, making the joint brittle. The ledeburite eutectic cannot be eliminated by heat treatment. Therefore, it is necessary to use sufficient upsetting to eliminate this structure.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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