The First Minister will re-open Tata Steel's site at Llanwern this afternoon after the company invested £3.6million in its Zodiac plant.
The aim is to offer more flexibility to customers in the automotive sector as they try and expand the business and reach new markets.
Jon Ferriman, Director of the Port Talbot and Llanwern steelworks, said: "The investments we have completed recently, including the Zodiac upgrade, are all intended to improve the sustainability and competitiveness of the South Wales steel industry in extremely challenging times."
Meanwhile GDP figures are out later this morning and are likely to show a small rise, mostly due to improvements in the manufacturing and construction sectors.
An investigation is underway after a worker at the Tata Steel plant at Port Talbot was injured by a spillage of molten steel.
Two others workers were treated for shock after the accident on Tuesday night.
All three were taken to Morriston Hospital in Swansea.
The Health and Safety Executive (HSE) has been informed.
Tata Steel said that an internal investigation is now underway.
Safety is our top priority and we will look to learn everything possible from an investigation. Our record has been ever improving to ever high levels and accidents like this are a set back.
The Health and Safety Executive said they planned to visit the site on Thursday.
Welsh manufacturing is celebrating an important milestone tonight with news that Tata Steel has re-started its second blast furnace at the giant Port Talbot works
It's a major boost for Tata who are one of Wales' most important manufacturers.
It also marks the completion of a massive re-building project that's been seen as a vote of confidence in the future.
Hannah Thomas reports from Port Talbot
The lighting of blast furnace four not only marks the completion of a sophisticated £185 million engineering effort, but also signals Tata's commitment to the future of steel-making in Wales.
There is no denying the challenges that steel companies like Tata are facing in difficult global markets.
During my recent meeting with the company's senior executives and union representatives in Port Talbot, we were able to discuss how Government and the organisation can work together to ensure Tata' s UK operations can remain competitive.
The restarting of the furnace will go some way towards that aim, and I look forward to making a return visit to Port Talbot to see it in full operational mode in the near future.
Steel giant Tata has announced that production has restarted at the second blast furnace at its Port Talbot site.
The project - which cost £185m - began after Blast Furnace No.4 was decommissioned in July 2012.
A Tata spokesperson said the work has made the furnace "more efficient", along with upgrading its capacity and environmental performance.
In November, Tata announced it would make 584 of its workers in Wales redundant, blaming high energy costs and a fall in global demand for steel.
Business Secretary Vince Cable has admitted that UK Government help for steelmakers with operations in Wales such as Tata and Celsa has been 'slow in coming.'
But he blamed 'international rules' for slowing down efforts to aid companies struggling with high energy costs and global financial problems.
He told MPs on the Welsh Affairs committee that ministers recognise the difficulties facing steel companies and is working out ways of alleviating them. He was responding to a question from Labour MP Jessica Morden.
Representatives from Tata Steel will appear before the Welsh Affairs Committee later today.
Today's session is also expected to hear from the trade union Community and other representatives from the steel industry.
Traffic came to a standstill around Port Talbot this morning because of a protest by steelworkers.
Employees from the Tata plant were demonstrating after being told that they were to be replaced by cheaper labour from elsewhere in the EU.
Our Correspondent Richard Morgan reports from the picket line.
Contractors at Tata Steel's Port Talbot plant have had their jobs reinstated after holding an unofficial picketline this morning.
The workers had claimed they were being replaced by foreign workers on lower pay rates.
Following the protest, Tata Steel released a statement saying that discussions had taken place with the principal contractor. A spokesperson confirmed that the affected workers will now continue in their jobs until their parts in the project are completed.
A unofficial picket line is being staged at the Tata Steel plant in Port Talbot this morning after contract workers claim they were replaced by foreign workers on lower pay rates.
It comes a day after 47 contract workers were told their work was coming to an end.
The men claim they have now been replaced by Polish and German workers on lower pay.
Tata Steel say they have not made any employee redundant and a single contract that was been carried out by a German company has now come to an end.
One contract worker - Robert Newton - says he was working at the plant as an insulation engineer for three months and was told the news on Monday when the men turned up after the holidays.
The men, who say they are all members of the GMB union, say they will demonstrate at the plant all morning.