- Effects of Mo in HTLA steels include ( ).
- （ ）contribute a lower susceptibility to cracking in aluminum alloys.
- Normally, heat treatment for QTLA steels including ( ).
- In the case of brazing a cast iron part to prevent cracking and hardening, insulating blankets are installed to ( ).
- The funciton of () is similar to that of Chromium that tends to stabilize alfa-Fe (bcc) and its high-temperature counterpart delta-Fe (bcc).
- For QTLA steels, toughness decrease may occur in ( ) after welding.
- Main alloy elements in HTLA steels include ( ).
- Microstructures of plain carbon steels include ( ).
- （ ） is not heat treatalbe.
- When to choose Metal Stitching instead of a welding or brazing process?
- Normally, microstructures of QTLA steels include ( )
- Main alloying elements in QTLA steels include ( ).
- Al–Zn–Mg alloys are more attractive than other aluminium alloys because ( ).
- Function of carbon in casting irons includes ( ).
- Hot ductility tests simply measure the ( ) strength and ductility.
- In case 3, the depth of the stop hole is equal to ( ).
- Generally, the silicon content of cast irons is generally in the range of ( ).
- High-carbon steels are susceptible to hydrogen induce cracking because they are with high content of ( ).
- HTLA steels are ( ).
- Their structure of ( ) consists of branched and interconnected graphite flakes in a matrix of pearlite, ferrite or a mixture of the two.
- ( ) has been added to the shielding gas to reduce hydrogen in aluminium welds.
- Because of the high sensitization temperature range, the weld decay in ferritic stainless steels occurs close to the( ).
- Comparing with QTLA steels, HTLA steels are with ( ) hardness and ( ) toughness.
- Which region is next to the partially melted zone?
- Some types of QTLA steels are susceptible to liquation cracking because they contain a lot of ( ).
- Welding 7xxx alloys in its NA condition is most ideal since the strength in the HAZ can be recovered almost completely by post weld（）.
- No preheating is recommended during wielding of duplex due to ( ).
- To avoid hydrogen induced cracking, we have to limit the intrusion of ( ) during welding.
- The cleaning action of the DCEP cycle helps remove hydrated oxides and hydrides.
- Coarse grain in HAZ may cause toughness decrease.
- Specialty tests to evaluate susceptibility to various metallurgically related defects,such as solidification cracking or hydrogen cracking, should be conducted in the alloy development or selection stage.
- In order to avoid underbead cracking, cooling directly to room temperature is allowed during the welding of MSS.
- Moisture, grease, rust are sources of H in weld.
- Lower bainite may be found in postweld microstructure of QTLA steels.
- Al-Mg-Si alloys belong to 6xxxx.
- High carbon steels are susceptible to solidification cracking because their carbon content is high.
- Blackheart malleable irons are produced by annealing low carbon (2.2～2.9%) white iron castings without decarburisation.
- Crack stop hole is used to prevent the crack from spreading during the welding process.
- Hardenability, internal stresses and hydrogen are the reasons of underbead cracking.
- The danger always exists that if the self-restraint test is more severe than the actual application, test results may not predict performance.
- Precipitation of GP2 is not expected due to high cooling speed during welding of 6XXX in NA conditions.
- The weldability of cast iron is poor comparing to that of low carbon steels.
- Peak temperature in HAZ determines the microstructure of the joint of carbon steels.
- Cold welding is more suitable for large castings that are difficult to preheat or to machine surfaces that cannot be preheated.
- Sometimes, underbead cracks could serve as starting points of fatigue cracking.
- For the alloy in T6 condition, strength loss occurs in joint due to reversion and grain growth of GP zones.
- LBW possibly increase the susceptibility to hydrogen induced cracking of QTLA steels.
- The sensitization can be remedied by annealing in 650-815℃ for 10 min.
- Welding in the T6 condition is often preferred to welding in the T4 condition for 6XXX.
- Use proper filler wires and dilution in autogenous GTA welding is helpful to depress the formation of solidification cracking in FZ of 2219 alloys.
- Welding such an alloy in its AA condition is most ideal since the strength in the HAZ can be recovered almost completely by postweld natural aging.
- Cast irons can be conveniently grouped according to their structure, mechanical properties and weldability; they are ( ).
- Generally, the carbon content of cast irons is generally in the range of ( ).
- Malleable irons are more readily weldable than grey irons.
- Casting irons with pearlitic matrix own higher strength than ferritic matrix .
- The brazing weld need annealing heat treatment so that it is easily machined.
- Small welding current is generally recommened for arc cold welding of castings due to ( ).
- ( ) is extremely hard and brittle, in which much of the carbon in is retained in the form of iron carbide without graphite flakes.
- The cleaning action of the DCEN cycle helps remove hydrated oxides and hydrides.
- Liquation cracking can be reduced by selecting the proper filler metal.
- The main alloying element is for 7xxx alloys ( ).
- A fine equiaxed dendritic structure has a lower susceptibility to cracking than a coarse columnar dendritic structure.
- Adjusting welding sequence is helpful to prevent the formation of weld decay in austenitic stainless steels.
- Pure aluminum is not susceptible to solidification cracking.
- Freon has been added to the shielding gas to reduce hydrogen in aluminium welds.
- The minimum hardness in the joint of a FSWed precipitation-hardened aluminum alloys lies in the ( ).
- Liquation cracking and hydrogen-induced cracking in the PMZ of aluminium alloys are both caused by the combination of a susceptible microstructure and the presence of tensile stresses.
- The funciton of Mo is similar to that of Chromium that tends to stabilize alfa-Fe (bcc) and its high-temperature counterpart delta-Fe (bcc).
- PWHT would be helpful to prevent the formation of weld decay in austenitic stainless steels.
- No preheating is recommended during wielding of duplex due to coarse grain.
- Weld metal of austenitic stainless steels is susceptible to weld decay.
- Adjusting welding sequence might be helpful to prevent the formation of knife-line attack in austenitic stainless steels.
- If the carbon content of a type of steel is 0.1%, this steel is a kind of ( ).
- Before designing welding procedure, we'd better to analyze the weldability of the workpiece.
- Normally, because of auto-tempering, the postweld microstructure of QTLA steel is ( ).
- To remedy the underbead cracking, we need to reduce cooling rate when we weld oil engine connecting rod.
- When you weld HTLA steels, you'd better to take advantage of auto-tempering.
- QTLA steel is not susceptible to solidification cracking because it is with ( ).
- The weldability of high-carbon steel is worse than that of low-carbon steel because high-carbon steel is with ( ).
- Auto-tempering occurs after welding when ( ).
- For HTLA steels, chromium is able to ( ).
- Weldability is not easily quantified, and can depend on a variety of factors, including ( ).
- With carbon equivalent ( ), the steel has a low tendency to harden and cold cracking?
- Maximum crack distance has been used to allow more accurate determination of the cracking ( ) range.
- The calculation formula of carbon equivalent of the IWS considers the influence of () on weldability.
- ( ) is not a factor that affects weldability.
答案:improving hardenability###improving tempering stability###decreas temper embrittlement###decreas grain size
答案:abundant liquid between grains###A fine equiaxed dendritic structure
答案:temper###austenitizing###quench
答案:electrical insulation###thermal insulation
答案:Mo###Nb
答案:HAZ###fusion zone
答案:Mo###Cr###V###Mn
答案:martensite###pearlite###ferrite
答案:1100###5052###3003
答案:Preheating the whole part is not practical###Downtime is critical###When metal stitching will produce the best repair###Low cost
答案:lath martensite###lower bainite
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