The purpose of preheating spiral steel pipe before welding

Critical components of alloy steel and thick parts must be preheated before welding.

The purpose of preheating the spiral steel pipe before welding is as follows:

(1) Preheating can slow down the cooling rate after welding, make hydrogen diffuse in the weld metal and escape, and avoid cracking caused by hydrogen. It can also reduce the degree of hardening of welds and heat-affected zones to improve the crack resistance of welded joints.

(2) Preheating can reduce welding stress. Uniform local or general preheating reduces the weld zone temperature (also known as temperature gradient) between welders. In this way, on the one hand, the welding stress is reduced, and on the other hand, the welding strain rate is reduced, thereby avoiding welding cracks.

(3) Preheating can reduce the bonding degree of the welded structure, especially the bonding degree of the corner joints, reduce the occurrence of cracks, and increase the preheating temperature.

The selection of welding preheating temperature and inter-pass temperature is not only related to the chemical composition of steel and electrode, the stiffness of welding structure, welding method, ambient temperature, etc. but these factors should also be considered and determined. In addition, the uniformity of preheating temperature has an important influence on the uniformity of the welding area in the thickness direction of the steel and the reduction of welding stress. The width of local preheating should be the possibility of welder restraint, generally three times the wall thickness around the weld zone, and not less than 150-200mm. If the preheating is uneven, not only will the welding stress not be reduced, but it will increase the welding stress.

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Xinyue Support Singapore Food Industry Development

Xinyue has been in steel pipe industry for decades, accumulated rich supplier resources, with its sufficient inventory to provide clients with short, frequency, fast goods supply preparation.

The client is a new from Singapore. The client needs the inventory of stainless steel all the year around, and has extremely requirements for the delivery date, quality and payment requirements. This order is different size from diameter 33.4 mm to 355.6 mm different size, standard ASTM A790 UNS S32750 stainless steel pipes.

For delivery, Xinyue perennial preparation of different specifications of inventory, in case of need. As for the quality, due to the epidemic, the client can not visit the factory in person. Xinyue provides clients with information of past stainless steel cooperation projects, third-party inspection reports, photos and videos of stock products and PMI testing videos, which further dispel client’s doubts and win their trust. For payment, Xinyue provides a number of bank information, and provides cooperate client with a good reputation for Xinyue. Finally reach an agreement with the client and confirm the purchase order.

The client's trust is the beginning of cooperation. This client not only cooperated with Xinyue for the first order due to the Xinyue’s good quality, fast delivery time and good service, but also actively introduced other friend to Xinyue for cooperation with Xinyue after cooperating with Xinyue. This is the client's great recognition and support for Xinyue.

“Build the world, serve the globe” it is Xinyue cooperation rule, and it is also because of the concept that service the client and good quality, which win over and over regular and new client long term cooperation.

https://www.tjxysteel.com/news/Xinyue-Support-Singapore-Food-Industry-Development-2052.html

All hands on deck to help our customers

Project location：Indonesia

Product：Anchor Bolt

Standard and material：

Bolt: ASTM F1554 GR.55

Nuts : ASTM A194 2H

Washer: ASTM F436 Type 1

Specifications：

Anchor Bolt M24×498 Thread 158×30mm

Anchor Bolt M50×1428 Thread 238×60mm

Application：Steel Piling

Inquiry time：2022.09

Order time：2022.10

Shipping time：2022.11

Arrival time：2022.11

The customer of this order is a downstream processing factory of local contractors in Indonesia. The journey of cooperation with Xinyue started in May this year. The fast delivery and high-quality service left a deep impression on the customer, and also contributed to the second cooperation between the two parties. The products of this order are anchor bolts, which belong to non-standard customization. After receiving the drawings from the end customer, the Xinyue team immediately made a detailed analysis of the drawings, took the initiative to request proofing, actively and quickly responded to customer needs, assisted customers in project bidding, and prepared various bidding documents. During the order production, the epidemic situation was blocked, resulting in an extremely tight delivery schedule. Over the past three years, the epidemic situation has been rampant repeatedly, so we gradually found out a response mechanism. First, we truthfully informed the customer of the actual situation. After receiving the customer’s understanding and support, Xinyue timely adjusted the shipping date of the letter of credit, and at the first time after the closure, it organized workshop workers to work overtime to quickly complete all production tasks, and finally successfully shipped to the customer’s destination port in early November.

https://www.xysteelpipe.com/all-hands-on-deck-to-help-our-customers/

Xinyue Steel — Winning customer trust with quality service

Project location：Australia

Product：Stainless steel coil

Standard and material：JIS G4305 SUS304

Specifications：2*1219*C/3*1222*C/4*1219*C

Application：Deep processing into other products

Inquiry time：2022.09.10

Order time：2022.09.31

Shipping time：2022.11.30

Arrival time：2022.12.08

This order is the second one from a new customer in Australia. The product quality, production process and delivery service of first order have been highly recognized by customers. In September this year, due to the project demand, the same batch of stainless steel coils were needed. The customer thought of Xinyue at the first time, and then sent an inquiry to our company. With good cooperation in the early stage for the same products, both parties quickly confirmed the details and contract terms. After receiving the down payment, Xinyue also started the production process as scheduled. At present, all the ordered products have passed SGS testing and successfully arrived at the customer’s destination port on December 8.

“Trust” is undoubtedly the most valuable and difficult thing to obtain in the commercial society. It is definitely the greatest affirmation for us to get 100% trust, support and recognition from customers. We will continue to work hard to complete every order and make constant efforts to realize the vision of “building the world to serve the world”.

https://www.xysteelpipe.com/xinyue-steel-winning-customer-trust-with-quality-service/

Thermal Expansion Seamless Steel Pipe Manufacturing Process

Cross rolling is a rolling method between longitudinal rolling and cross rolling. The rolling of the rolled piece rotates along its own axis, deforms and advances between two or three rolls whose longitudinal axes intersect (or incline) in the same direction of rotation. Cross rolling is mainly used for piercing and rolling of pipes (such as the production of thermal expansion seamless pipes), and periodic section rolling of steel balls.

The cross rolling method has been widely used in the production process of heat-expanded seamless steel pipes. In addition to the main thermal expansion process of piercing, it is also used in rolling, leveling, sizing, elongation, expansion and spinning, etc. in the basic process.

The difference between cross rolling and longitudinal rolling and cross rolling is mainly in the fluidity of metal. The main direction of metal flow during longitudinal rolling is the same as that of the roll surface, and the main direction of metal flow during cross rolling is the same as that of the roll surface. Cross rolling is between longitudinal rolling and cross rolling, and the flow direction of deformed metal is Forming an angle with the direction of movement of the deformation tool roll, in addition to the forward movement, the metal also rotates around its own axis, which is a spiral forward movement. There are two types of skew rolling mills used in production: two-roll and three-roll systems.

The piercing process in the production of thermal expansion seamless steel pipe is more reasonable today, and the piercing process has been automated. The whole process of cross-rolling piercing can be divided into 3 stages:

1. Unstable process. The metal at the front end of the tube blank gradually fills the deformation zone stage, that is, the tube blank and the roll begin to contact the front metal and exit the deformation zone. In this stage, there are primary bite and secondary bite.

2. Stabilization process. This is the main stage of the piercing process, from the metal at the front end of the tube blank to the deformation zone until the metal at the tail end of the tube blank begins to leave the deformation zone.

3. Unstable process. The metal at the end of the tube blank gradually leaves the deformation zone until all the metal leaves the roll.

There is a clear difference between a stable process and an unstable process, which can be easily observed in the production process. For example, there is a difference between the size of the head and tail and the middle size of a capillary. Generally, the diameter of the front end of the capillary is large, the diameter of the tail end is small, and the middle part is consistent. Large head-to-tail size deviation is one of the characteristics of an unstable process.

The reason for the large diameter of the head is that as the metal at the front end gradually fills the deformation zone, the friction force on the contact surface between the metal and the roll increases gradually, and it reaches a maximum value in the complete deformation zone, especially when the front end of the tube billet meets the plug At the same time, due to the axial resistance of the plug, the metal is resisted in the axial extension, so that the axial extension deformation is reduced, and the lateral deformation is increased. In addition, there is no outer end restriction, resulting in a large front diameter. The diameter of the tail end is small, because when the tail end of the tube blank is penetrated by the plug, the resistance of the plug drops significantly, and it is easy to extend and deform. At the same time, the lateral rolling is small, so the outer diameter is small.

The front and rear jams that appear in production are also one of the unstable features. Although the three processes are different, they are all realized in the same deformation zone. The deformation zone is composed of rolls, plugs and guide discs.

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Carbon content classification of seamless tubes

Carbon steel seamless tube is divided into:

1. Low carbon steel seamless tube

Low carbon steel tube is carbon steel with a carbon content of less than 0.25%, including most ordinary carbon structural steels and some high-quality carbon structural steels, most of which are used for engineering structural parts that do not require heat treatment. Some are also carburized or heat treated.

2. General carbon content seamless tube (medium carbon steel)

Medium carbon steel has good thermal working and cutting performance, but poor welding performance. Its strength and hardness are higher than low carbon steel, while plasticity and toughness are lower than low carbon steel. It can be directly processed by cold rolling without heat treatment, or it can be machined or forged after heat treatment. The hardened medium carbon steel has excellent comprehensive mechanical properties. The maximum achievable hardness is about HRC55 (HB538), and σb is 600-1100MPa. Therefore, medium carbon steels are widely used in various moderate strength level applications. It is not only widely used as a building material, but also used to make various machine parts.

3. High carbon steel seamless tube

High-carbon steel is often called tool steel, with a carbon content of 0.60% to 1.70%, which can be quenched and tempered, and has poor welding performance. Hammers, crowbars, etc. are all made of steel with a carbon content of 0.75%. Cutting tools such as drills, taps and reamers are made of steel with a carbon content of 0.90% to 1.00%.

The weldability of steel mainly depends on its chemical composition. The most influential element is carbon, and the higher the carbon content of the steel, the more difficult it is to weld. Most of the other alloying elements of steel are also not conducive to welding, but the degree of influence is generally much smaller than that of carbon.

Generally speaking, low carbon steel has good weldability and does not require special processing methods. Welding with basic electrodes is only necessary when low temperatures, thick plates or high demands are required and proper preheating is required. When the carbon and sulfur content of low-carbon steel exceeds the upper limit, in addition to reasonable selection of the groove shape, high-quality low-hydrogen electrodes, preheating and post-heating are used to prevent thermal cracks from reducing the melt ratio.

Medium carbon steel is prone to cold cracks during welding. The higher the carbon content, the greater the hardening tendency of the heat-affected zone, the greater the tendency of cold cracking, and the poorer the weldability. As the carbon content of the steel increases, so does the carbon content of the weld metal. Combined with the negative impact of sulfur, welds are prone to hot cracking. Therefore, when welding medium carbon steel, basic electrodes with excellent crack resistance must be used, and preheating and post-heating measures must be taken to suppress the occurrence of cracks.

When welding high-carbon steel, due to the high carbon content of this steel, large welding stress will be generated during welding. The tendency of hardening and cold cracks in the heat-affected zone of the weld is large, and the weld zone is also prone to hot cracks. High-carbon steel is more likely to produce hot cracks than medium-carbon steel during welding, so it has the worst weldability and is not used for general welding structures, but only for repair welding and surface treatment of castings. After welding, the weld must be tempered to relieve stress, fix the structure, prevent cracks, and improve the performance of the weld.

https://www.xysteelpipe.com/carbon-content-classification-of-seamless-tubes/

Cross rolling perforating technology and quality defect and its prevention

The cross-rolling piercing process is the most widely used in the production of seamless steel pipes, and was invented by the German Mannesmann brothers in 1883. The cross-rolling piercing machine includes two-roll cross-rolling piercing machine and three-roll cross-rolling piercing machine. The capillary quality defects produced by cross-rolling and piercing of tube blank mainly include inward fold, outward fold, uneven wall thickness and surface scratches of capillary.

Capillary infolding: Capillary is the defect most likely to occur in cross-rolling piercing, and it is closely related to the piercing performance of the tube blank, the adjustment of the piercing process parameters of the piercing pass machine, and the quality of the piercing plug. Factors affecting capillary infolding: one is the reduction (rate) and compression times before the plug; the other is the hole shape; the third is the surface quality of the plug.

Outward bending of the capillary tube: Most of the outward bending of the capillary tube is caused by the surface defect of the tube blank, which is another surface quality defect that is easily caused when the tube blank is cross-rolled and pierced. Factors affecting capillary outward bending: A. tube blank plasticity and perforation deformation; B. tube blank surface defects; C. perforation tool quality and pass shape.

Uneven capillary wall thickness: There are uneven transverse wall thickness and uneven longitudinal wall thickness. When cross-rolling and piercing, uneven transverse wall thickness is most likely to occur. The main factors affecting the uneven transverse wall thickness of the capillary tube are: the heating temperature of the tube blank, the centering of the tube end, the adjustment of the hole pattern of the piercing machine and the shape of the tool, etc.

Capillary surface scratches: Although the requirements for the surface quality of perforated capillary pipes are not as strict as those of pipe rolling mills and sizing mills for steel pipe surface quality, severe surface scratches of capillary pipes will also affect the surface quality of steel pipes. Factors affecting the surface abrasion of the capillary tube: mainly because the surface of the perforating tool or the exit roller table of the piercing machine is severely worn, rough or the roller table does not rotate. In order to prevent the capillary surface from being scratched by the surface defects of the perforating tool, the inspection and grinding of the perforating tool (guide cylinder and trough) should be strengthened.

https://www.xysteelpipe.com/cross-rolling-perforating-technology-and-quality-defect-and-its-prevention/

Surface processing defects of seamless tubes and their prevention

 Surface processing of seamless tubes (smls) mainly includes: steel tube surface shot peening, overall surface grinding and mechanical processing. Its purpose is to further improve the surface quality or dimensional accuracy of steel tubes.

Shot peening on the surface of seamless tube: Shot peening on the surface of steel pipe is to spray iron shot or quartz sand shot (collectively referred to as sand shot) of a certain size on the surface of seamless tube at a high speed to knock off the oxide scale on the surface to Improve the smoothness of the steel tube surface. When the iron oxide scale on the surface of the steel tube is crushed and peeled off, some surface defects that are not easy to be found by the naked eye will also be exposed and easy to remove.

The size and hardness of the sand shot and the injection speed are important factors affecting the shot peening quality of the steel tube surface. If the sand shot is too large, the hardness is too high and the injection speed is too fast, it is easy to crush and fall off the oxide scale on the surface of the steel tube, but it may also cause a large number of pits of different sizes on the surface of the steel tube to form pockmarks. On the contrary, the iron oxide scale may not be completely removed. In addition, the thickness and density of the oxide scale on the steel tube surface will also affect the shot peening effect.

The thicker and denser the iron oxide scale on the steel tube surface, the worse the effect of iron oxide scale cleaning under the same conditions. Spray (shot) shot derusting is the most ideal way for pipeline derusting.

Overall grinding of the surface of seamless tube: The tools for overall grinding of the outer surface of the steel pipe mainly include abrasive belts, grinding wheels and grinding machines. The overall grinding of the inner surface of the steel pipe adopts grinding wheel grinding or inner mesh grinding machine grinding. After the surface of the steel tube is ground as a whole, it can not only completely remove the oxide scale on the surface of the steel tube, improve the surface finish of the steel tube, but also remove some small defects on the surface of the steel tube, such as small cracks, hairlines, pits, scratches, etc. Grinding the surface of steel tube with abrasive belt or grinding wheel as a whole may cause quality defects mainly: black skin on the surface of steel tube, excessive wall thickness, plane (polygon), pit, burns and wear marks, etc. The black skin on the surface of the steel tube is due to the small amount of grinding or pits on the surface of the steel tube. Increasing the amount of grinding can eliminate the black skin on the surface of the steel tube.

Generally speaking, the surface quality of the steel pipe will be better, but the efficiency will be lower if the seamless steel tube is ground with the abrasive belt as a whole.

https://www.xysteelpipe.com/surface-processing-defects-of-seamless-tubes-and-their-prevention/

Factors affecting the quality of seamless pipe

There are two categories of factors that affect the quality of seamless tubes: steel quality and rolling process factors.

Many factors of the rolling process are discussed here. The main influencing factors are: temperature, process adjustment, tool quality, process cooling and lubrication, removal and control of sundries on the surface of rolled pieces, etc.

1. Temperature

Temperature is the most important factor affecting the quality of seamless tubes. First of all, the uniformity of the heating temperature of the tube blank directly affects the uniform wall thickness and inner surface quality of the perforated capillary, which in turn affects the wall thickness quality of the product. Secondly, the temperature level and uniformity of the seamless steel tube during rolling (especially the final rolling temperature) are related to the mechanical properties, dimensional accuracy and surface quality of the product delivered in the hot-rolled state, especially when the steel billet or tube blank When it is overheated or even overburned, it will cause waste products. Therefore, in the production process of hot-rolled seamless tubes, heating and controlling the deformation temperature strictly according to the process requirements must be done first.

2. Process adjustment

The quality of process adjustment and work quality mainly affects the geometric and appearance quality of seamless steel tubes.

For example, the adjustment of the piercing machine and the rolling mill affects the wall thickness accuracy of the product, and the adjustment of the sizing machine is related to the outer diameter accuracy and straightness of the product. Moreover, process adjustment also affects whether the rolling process can be carried out normally.

3. Tool quality

Whether the tool quality is good or bad, stable or not, is directly related to whether the dimensional accuracy, surface quality and tool consumption of the product can be effectively controlled; Surface, the second is to affect mandrel consumption and production costs.

4. Process cooling and lubrication

The cooling quality of piercing plugs and rolls not only affects their life, but also affects the quality control of the inner and outer surfaces of finished products. The cooling and lubrication quality of the mandrel first affects the inner surface quality, wall thickness accuracy and mandrel consumption of the seamless steel tube; at the same time, it will also affect the load during rolling.

5. Removal and control of impurities on the surface of the rolled piece

This refers to the timely and effective removal of oxide scale on the inner and outer surfaces of capillary and barren pipes and the control of re-oxidation before rolling deformation. Nitrogen blowing and borax spraying treatment on the inner hole of the capillary tube, high-pressure water descaling at the entrance of the rolled tube and the fixed (reduced) diameter can effectively improve and improve the quality of the inner and outer surfaces.

In short, there are many factors that affect the quality of seamless steel tubes, and they are often the combined effect of various factors. Therefore, the above-mentioned main influencing factors must be effectively controlled. Only in this way can we control the quality of seamless steel tubes and produce hot-rolled seamless steel tubes with high dimensional accuracy, good performance and excellent quality.

https://www.xysteelpipe.com/factors-affecting-the-quality-of-seamless-pipe/